TUPA
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Tuesday Poster Session: TUPA
09 May 2023, 16:30 -
18:30
TUPA001
Copper surface treatment with deep UV ultrafast laser for improved photocathode photoemissive properties
1350
Surface nanostructuring is a promising approach when it comes to improving the quantum efficiency (QE) of materials for electron accelerator purposes at CERN. This is due to the plasmonic effect taking place in metallic materials at the nanoscale, when an electromagnetic wave interacts with a sub-wavelength feature. Ultrafast laser surface nanopatterning can be an efficient and times saving method for producing such nanostructures. We conducted a study of nanostructuring of copper surfaces with a deep-UV femtosecond laser. A wide range of fabrication parameters (speed, laser fluence and repetition rate) were tested. At different energy regimes we were able to produce Laser Induced Periodic Surface Structures (LIPSS), as well as spherical nanoparticles of tunable size and other types of periodic nanoscale features. Sub-wavelength periodic structures yield higher exaltation of surface plasmons under matching excitation wavelength, resulting in a potentially significant increase in QE of copper photocathodes. Moreover, by using the same laser source for nanomachining and photoemission, one can easily integrate the technology in and existing photoinjector.
Paper: TUPA001
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA001
About: Received: 13 May 2023 — Revised: 22 May 2023 — Accepted: 22 May 2023 — Issue date: 26 Sep 2023
TUPA002
Simulation of plasmonic effects in nanostructured copper surfaces for field-assisted photoemission
1354
We propose a simulation model of the field enhancement and quantum efficiency (QE) increase of metallic surfaces as a result of a surface nanostructuring. In the framework of photoinjector facilities for electron accelerators at CERN, achieving optimal nanostructuring parameters may become a significant asset. The presence of a well-designed periodic surface topography can give rise to plasmonic resonance and coupling effects within the structures, which yields a local increase in electron density and an electric field enhancement. This model is used to provide a deeper insight into these effects. We investigate the dependency of the electron emission enhancement on the nanopattern geometry and incident wavelength on the plasmonic resonance. We examine, based on former experimental results, the performance of Laser Induced Periodic Surface Structures (LIPSS) and other types of periodic nanoscale features, but we also demonstrate the surprisingly strong contribution of nanoparticles in the global field enhancement of the surface. These particles are a common side effect of ultrafast laser surface processing and themselves exhibit unique plasmonic resonance properties.
Paper: TUPA002
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA002
About: Received: 04 May 2023 — Revised: 07 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA003
Prformance of laser patterned copper plasmonic photocathodes
1358
We study ultrafast laser surface nanopatterning as an alternative to improve the photo-emissive properties of metallic photocathodes. By tailoring the physical dimensions of these surface nanostructures, one can localize the optical field intensity and exploit plasmonic effects occurring in such nanostructures. As a result, this surface nanopatterning technique can become a great tool for improving metallic photocathodes photoemission behavior enabling their use for next generation high brightness electron sources. Our goal is to investigate such surface-plasmon assisted photoemission processes with a view on simplifying the photocathode production at CERN while extending the lifetime of existing photoinjectors. The performance of two different femtosecond laser nanopatterned plasmonic photocathodes was analyzed by measuring the quantum yield with a 65kV DC electron gun utilizing 266nm laser excitation generated by a nanosecond laser with 5ns pulse duration and 10Hz repetition rate. By comparing the electron emission of the copper surface nanostructured areas with that of a flat area, our results suggest quantum yield enhancements of up to 5 times.
Paper: TUPA003
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA003
About: Received: 07 May 2023 — Revised: 08 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
Experimental investigations and Simulations of Dark Current in ELBE SRF gun-II
In the high gradient rf photoinjectors, dark current is the “unwanted beam” not produced by the cathode drive laser. It is a part of field emission from the cavity and photocathode, which is accelerated through the gun. Dark current can cause beam loss, increase the risk of damage to accelerator components, and create additional background for beam users. Furthermore, during operation of the ELBE srf gun, the dark current has been found to correlate with the photocathode QE and life time. Therefore, understanding the sources as well as the dynamics of dark current is crucial to machine safety and gun quality. In this paper we present our experimental investigations of the dark current at the ELBE SRF gun-II. The beam dynamics of the dark current is studied with the ASTRA code, which helps us to track the field electrons starting from the cathode area and from other sources, so that we can understand their different contributions to the dark current.
Impact of Surface Cleaning on the Quantum Efficiency of Mg Photocathodes
Many experiments in biomedicine, security imaging, and condensed matter physics require high brilliance and moderate electron beams. The properties of the photo electron source is defined by the photocathode quality such as low thermal emittance, fast response time, high quantum efficiency (QE) and the photocathodes’ robustness. Metal cathodes are commonly used in RF Guns because they work robustly and tolerate poor vacuum compared to semiconductor photocathodes. However, metal cathodes only provide low quantum efficiencies in UV range and the most prerequisite for improving the QE is to produce an atomically clean surface. At ELBE, a successfully established process for improving the QE of Mg is laser cleaning [1]. Although this method improves the QE, a non-uniform surface and potential damage of the Mg photocathode arise at the same time. Ideally, an alternative process producing an atomically clean, smooth, and damage-free surface is desired. In this work, we evaluate and discuss the effect of different surface cleanings, including hydrogen ion cleaning and thermal surface cleaning under UHV conditions, on the QE of Mg photocathodes, with the help of in-situ X-ray photoelectron spectroscopy (XPS). References [1] Teichert, J. et al. Successful user operation of the superconducting radio-frequency photo electron gun with Mg cathodes at ELBE. Phys. Rev. Accel. Beams 24, 1–30 (2021).
TUPA006
Activities at INFN LASA on ESS Medium Beta Cavities
1362
To complete the Italian In-Kind contribution to the ESS SRF Linac, we are working on the qualification of the last eight missing cavities. To achieve this, we are proceeding with reprocessing of not yet qualified cavities and, as a mitigation, we are constructing at the vendor four more cavities. In this paper, we report on the actual status of both of these activities with the most recent results.
Paper: TUPA006
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA006
About: Received: 03 May 2023 — Revised: 07 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
TUPA007
Status of a low-energy electron TRAnsverse Momentum Measurement device (TRAMM) at INFN LASA
1366
To advance in the characterization of photocathodes for high brightness sources, the measurement of the thermal emittance plays a key role. The TRAnsverse Momentun Measurement device developed at INFN LASA will allow equipping our photocathode laboratory with an advance device able gving in quasi on-line feedback during the photocathode growth process. This paper reports on the status of the apparatus and its latest achievements.
Paper: TUPA007
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA007
About: Received: 04 May 2023 — Revised: 10 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
TUPA008
Photocathode activities at INFN LASA
1370
INFN LASA photocathode lab develops and produces films that are used in high brightness photoinjectors. Besides the long-time and still on-going experience on Cs2Te, recently we have restarted an activity on alkali-antimonide films, sensitive to visible light, exploring the possibility of their stable operation in CW machine. We report in this paper the recent results obtained both on the advancements on cesium telluride and on the characterization of alkali antimonide.
Paper: TUPA008
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA008
About: Received: 04 May 2023 — Revised: 11 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
TUPA009
Progress on the new high gradient C Band standing wave RF photo-gun
1374
The new C-Band RF gun, developed in the context of the European I.FAST project has been realized. It is a 2.5 cell standing wave cavity with a four port mode launcher, designed to operate with short rf pulses (300 ns) and cathode peak field larger than 160 MV/m. In the paper we present the realization procedure and the results of the vacuum and low power RF test. The gun is now ready for the high power test that will be performed at PSI, Switzerland.
Paper: TUPA009
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA009
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
Work function measurement by means of photoelectron yield spectroscopy using a tunable pulsed laser to investigate short lifetime of the CeB6 thermionic cathode at SACLA
We have been developing an in-situ work function (WF) measurement system to investigate an unexpectedly short lifetime problem of a CeB6 thermionic cathode at the SACLA electron injector. Photoelectron yield spectroscopy using a nanosecond tunable pulsed laser in the wavelength range from 410 to 709 nm was adopted because this method provides a high S/N ratio in a hot operational condition of the thermionic cathode and makes it possible to perform the measurement during the XFEL operation. As the first step, demonstrative WF measurements using an offline cathode test system have been conducted and the WF of an unused fresh CeB6 cathode was precisely estimated to be a value of 2.44±0.02 eV at a temperature of 836 °C. In this conference, the details of the test system and the first measurement results will be presented.
TUPA012
Modeling optical interference effects for optimization of electron emission properties from thin film semiconductor photocathodes
1378
High-quality electron beams are critical for generation of intense X-ray pulses from free electron lasers. It was proposed that complex thin films and heterostructures with semiconductor photoemissive layers may be used in photocathodes to produce electron beams with better quality. New developments in material science allow designing alkali-antimonide photocathodes with specific coatings that could significantly increase their lifetime while not markedly degrading their quantum efficiency (QE). Moreover, results from recent experiments demonstrated that QE can be increased by optical interference absorption effects in layered materials. Modeling of these complex photocathode material designs is needed to predict and optimize their electron emission properties. We apply recently developed extended moments and thin film models to evaluate quantum efficiency and intrinsic emittance from thin film cesium-telluride and alkali-antimonide semiconductor photocathodes grown on different substrates. We will discuss simulation results and suggest possible ways to optimize electron emission properties from these thin films photocathodes.
Paper: TUPA012
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA012
About: Received: 02 May 2023 — Revised: 07 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
Operation pressure and lifetime improvement of bialkali photocathodes via graphene protection
Protection of free-electron sources has been technically challenging due to lack of materials that transmit electrons while preventing corrosive gas molecules. Two-dimensional (2D) materials uniquely possess both of required properties. Here, we report three orders of magnitude increase in operation pressure and factor of two to four enhancement in the lifetime of high quantum efficiency (QE) bialkali photocathodes (cesium potassium antimonide (CsK2Sb)) by protecting them with graphene. The photoelectrons were extracted through the graphene protection layer in a reflection mode, and we achieved QE of ~0.14 % at ~3.4 eV, 1/e lifetime of 188 hours during operation, and no decrease of QE during operation at pressure of as high as ~1×10-3 Pa. In comparison, the QE decreased drastically at 10-6 Pa for bare, non-protected CsK2Sb photocathodes and their 1/e lifetime during operation was ~48 hours. We attributed the improvements to the gas impermeability and photoelectron transparency of graphene.
TUPA014
Transport model and Monte-Carlo simulations for photoemission from thin film semiconductors under high fields
1382
Semiconductor photocathodes, particularly those produced with thin films and heterostructures, are promising candidates of high brightness electron sources. It is also well-known that electron beam brightness increases with the photocathode gun’s operating gradient. Combining both heterostructure semiconductor photocathode and cyro-cooled high-gradient photocathode gun may improve electron sources for many applications. However, effects of the high field gradient on the semiconductor photocathode need to be understood in order to preserve and optimize the quality of the emitted photo-electron beams, which can be done with from detailed simulation study and theoretical analysis. In this work, we apply Monte-Carlo method to study high field transport and emission from semiconductor photocathodes such as Cs2Te. The results will be used to inform a theoretical transport model based on the moments method and the cathode development for the CARIE project at LANL.
Paper: TUPA014
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA014
About: Received: 03 May 2023 — Revised: 12 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
Multiscale material design of robust semiconductor photocathodes under strong fields
Unprecedented electron beam brightness can potentially be achieved by exploiting high gradients in cryo-cooled RF cavities functionalized with high QE semiconductor photocathode materials. However, strong electric fields and thermal stresses from associated emission currents could potentially affect material stability, leading to breakdown events which may shorten device lifetime or degrade performance. To ensure robust performance and long operational lifetimes, the underlying processes leading to microstructural evolution in such semiconductor photocathodes needs to be explored under strong fields. Here, we present a suite of multiscale modeling tools specially tailored to probe the electro-thermo-mechanical behavior of semiconductor photocathodes. We first parameterize a machine learning interatomic potential suitable for classical charge equilibration molecular dynamics (MD) using density functional theory (DFT) calculations of CsTe. DFT and MD informed material properties are further incorporated into a meso-scale finite element (FE) model to predict morphological evolution of cathode surfaces under fields and thermal stresses due to emission currents.
Methods to Discover New Photocathode Materials using Machine Learning and Data-Driven Screening
The photocathodes used as electron sources in high-performance electron accelerators today are largely one of only a handful of materials. While there has been an increased understanding of the properties of the electron beams produced by these cathodes, there has been little change in the overall selection of materials used at accelerator facilities. In fact, nearly all of the photocathodes in use today originated in the photomultiplier tube or night vision goggle industries, where efforts were aimed at discovering new materials by employing trial-and-error based iterative experimental approaches. Our work in the field of photocathode discovery was initially directed towards improving the brightness of electron beams used in FELs and was the first data-driven approach to screening for high brightness photocathode materials. Through screening over 74,000 semiconducting materials, a list of novel candidate materials was generated. Our current work is focused on two other areas of interest for photocathodes: very high average current photocathodes and spin-polarized electrons. We will apply active learning techniques to reduce the amount of computationally expensive calculations that need to be performed in order to discover more new materials for photocathodes.
TUPA019
Photoelectron spectroscopy of CsK2Sb photocathode at Synchrotron Radiation Facility using vacuum transport system
1386
As accelerators and electron microscopes become more advancement, high-performance photocathodes are required. In particular, CsK2Sb photocathode is of interest because of its low emittance, excitability in visible light, and high quantum efficiency (QE). On the other hand, it has drawbacks such as weak structure, limited operating vacuum pressure, and short lifetime with time or charge. To resolve these issues, it is necessary to understand the molecular structure of the cathode and its degradation mechanism. In this study, we transported CsK2Sb photocathode to a beamline of synchrotron radiation facility using a vacuum transport system for surface analysis. Specifically, the cathode was deposited at the evaporation system at Nagoya University. We transported it to Aichi Synchrotron Radiation Center (Aichi SR) away from 15 km, and analyzed it in the depth direction by X-ray photoelectron spectroscopy (XPS) at BL7U. Based on the results, we quantitatively evaluated the composition ratios and stoichiometry of the cathode element (Sb, K, Cs). A Cs excess state was observed at the surface, and it is consistent with previous studies. It was observed that K was first desorbed among the three elements of cathode with sputtering. The cause is considered that weakest binding energy of K.
Paper: TUPA019
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA019
About: Received: 20 Mar 2023 — Revised: 07 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA020
Test of a DC-photogun Injector for the Lighthouse facility
1390
Worldwide there is a push for producing medical isotopes using particle accelerators rather than fission reactions. Here we report on the operation of a DC-photogun designed for producing Mo-99 in the Lighthouse facility and commissioned by the Institute for Radio Elements (IRE, Belgium). The gun is based on the successful CBETA design by Cornell University. It is installed at the RI site in Bergisch Gladbach, Germany. As innovative components it contains a photocathode deposition system allowing an automatic transfer of photocathodes into the gun and it uses Novec 4710, a gas developed by 3M as a sustainable replacement for SF6. The injector was installed at the RI site in Bergisch Gladbach, Germany and has produced first e-beam in April 2022. Currently we are ramping up the e-beam power and optimizing the photocathodes. The high-voltage has been conditioned up to >400kV and we see no negative impact of the NOVEC gas. The laser produces 40W at 515nm and 1.3GHz repetition rate and adjustable pulse length. It can deliver pulse trains of 100ns up to CW with variable pulse power onto the cathode. In the MBE system we routinely prepare photocathodes with at least 5% quantum efficiency, well sufficient for the design current of 40mA.The beam diagnostics is currently used to optimize the electron beam. The current focus is on ramping up the power to the design value of 40mA at 350kV.
Paper: TUPA020
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA020
About: Received: 11 May 2023 — Revised: 12 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
Lifetime improvement of the CeB6 thermionic cathode at the X-ray free-electron laser facility SACLA by avoiding backward-accelerated electrons
A CeB6 thermionic gun is presently operating for the X-ray free-electron laser (XFEL) facility SACLA. The gun emits high-intensity stable electron beams with a low-emittance of 0.6 µm, however, the emission lifetime of CeB6 cathode was unexpectedly limited to only one year or less at the SACLA injector. Recently, it was predicted by a particle tracking simulation and measurements that a cause of the short lifetime was bombardment of high-energy electrons which were accelerated backward at the injector linac. The CeB6 gun tank was modified to detach the horizontal cathode position from the beam axis of injector in order to avoid the back-bombardment. By these attempts, the cathode lifetime was significantly prolonged and the XFEL operation became stable more than ever. In this conference, beam simulation and measurements of the backward-accelerated electrons and apparatus modification to improve the CeB6 cathode lifetime will be presented.
Engineering, Manufacturing and Validation of Microwave Thermionic Electron Gun for Advanced Photon Source Upgrade*
Recently, RadiaBeam has designed, manufactured, high power tested and delivered a robust production ready S-Band thermionic RF gun with optimized electromagnetic performance, improved thermal engineering and robust yet precise cathode mounting technique. This gun will facilitate performance improvements of existing and future light sources, industrial accelerators, and electron beam driven terahertz sources. Unlike conventional electrically or side-coupled RF guns, this new gun operates on pi-mode, with a help of magnetic coupling holes. This new iteration of thermionic electron gun was redesigned for cost efficiency without sacrificing performance. Thermal simulations, mechanical engineering, manufacturing and high power testing results will be presented.
TUPA023
Longitudinal bunch shaping and optimization of the FAST injector
1393
The FAST Injector at Fermilab has been the focus of a number of recent experimental efforts as 1) the driver of a novel FEL experiment, 2) as the injector for IOTA, and 3) as a test-bed for novel machine learning algorithms to reconstruct phase space measurements. Here we present our recent work to simulate the FAST injector and perform realistic comparisons of simulated beam distributions to measured beam distributions using a multi-slit emittance diagnostic. We also present studies on using laser pulse stacking to shape the beam distribution for creating optimal current distributions for FEL experiments.
Paper: TUPA023
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA023
About: Received: 03 May 2023 — Revised: 22 May 2023 — Accepted: 22 May 2023 — Issue date: 26 Sep 2023
Optimization Studies On An S-band RF Gun For MeV-Ultrafast Electron Diffraction
MeV-ultrafast electron diffraction (MeV-UED) has enabled broad scientific opportunities for the studies of structural dynamics, ultrafast chemical processes and coupling of electronic and atomic motions in a variety of gas, liquid and solid state systems. The growing demand of future scientific needs calls for relativistic electron probes with ultra-short bunch length(10 fs) and ultra-low normalized emittance(2 nm). A high brightness, low emittance electron source is required for this purpose. Here, we present optimization studies on a 2.86 GHz S-band RF gun for MeV-UED applications. Gun modeling, beam dynamics simulations and multi-objective genetic algorithm (MOGA) optimizations will be described. Performance with different cell lengths, gun phases and pulse charges will be presented.
Commissioning of LCLSII injector
LCLSII 1-MeV CW electron source was successfully commissioned 2018-2020. 100MeV injector system is being commissioned since summer 2022. CW RF operations for injector system is routinely established and e-beam is being ramped to very high rate. Ultra-low emittance has been achieved for desired charges. Dark current along the injector beam line is systematically characterized and mitigations are placed. We will present operational experience for CW RF gun/buncher and high rate (up to 1MHz) e-beam operations. 100MeV injector beam performance including ultra-low emittance and bunch length for desired charges, and dark current measurement and mitigation will be discussed.
TUPA028
Low-emittance SRF photo-injector prototype cryomodule for the LCLS-II high-energy upgrade: design and fabrication
1396
The high-energy upgrade of the Linac Coherent Light Source II (LCLS-II-HE) will extend the X-ray energy range up to 20 keV. The goal is to produce low emittance (0.1 mm∙mrad) electron bunches (100 pC/bunch) and accelerate 30 μA beams through the superconducting linac to 8 GeV. A low-frequency superconducting radio-frequency photo-injector (SRF-PI) will be a key aspect of the upgrade. An SRF-PI cryomodule with a 185.7 MHz Quarter-Wave Resonator (QWR) for operation at a cath-ode field of 30 MV/m and a cathode system compatible with high quantum efficiency photo-cathodes operating at 55-80 K or 300 K are currently being developed. We report on the design and fabrication status of the SRF-PI cryomodule and cathode system for LCLS-II-HE.
Paper: TUPA028
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA028
About: Received: 03 May 2023 — Revised: 05 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA029
Conceptual design of the low dark charge photocathode RF gun for Relativistic Ultrafast Electron Diffraction and Imaging (RUEDI) facility
1400
The electron source is a critical component of the RUEDI (Relativistic Ultrafast Electron Diffraction & Imaging) facility, which needs to provide beam to match the re-quirements for performing both electron microscopy and ultrafast electron diffraction. To meet these demands, different operational modes are needed, to deliver ultra-short, ultra-bright and highly temporally and energy stable electron pulses with a charge varying from 0.2 pC to 20 pC and a kinetic energy of 4 MeV, with a repetition rate with 100 Hz (and higher). The dark charge produced by the electron source should be minimised to avoid significant noise in the image. Analysis of existing elec-tron sources suggested that the optimal solution is a normal-conducting S-band RF photocathode gun operat-ing with a metal photocathode, illuminated by an ultravi-olet laser. A number of critical design decisions were identified to reduce gun dark charge which are discussed in this paper. These include the gun RF design (number of cells and type of coupling), beam generation scheme (that includes the type of the photocathode), reducing duration of RF drive pulse and methods of maintaining good RF field stability.
Paper: TUPA029
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA029
About: Received: 03 May 2023 — Revised: 07 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA030
Mean Transverse Energy and Degradation Measurements on a Caesium Telluride Photocathode
1404
Fourth generation light sources require high brightness electron beams. To achieve this a cathode with a high quantum efficiency and low intrinsic emittance is required while also being robust with a long lifetime and low dark current. Alkali-metal photocathodes have the potential to fulfil these requirements and, as such, are an important area of research for the accelerator physics community. A Cs-Te photocathode grown at STFC Daresbury Laboratory is presented. Important photoemissive properties such as quantum efficiency (QE), mean transverse energy (MTE) and lifetime have been investigated using the Transverse Energy Spread Spectrometer (TESS). Elevated MTE beyond the Cs$_2$Te photoemission threshold is reported as well the QE decrease and MTE increase when a Cs-Te photocathode is subject to progressive oxygen degradation.
Paper: TUPA030
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA030
About: Received: 02 May 2023 — Revised: 09 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA032
Copper photocathodes for the modified 10 Hz gun on the CLARA accelerator
1408
During the last run, the CLARA accelerator* ran with a 2.5 cell 10 Hz S-band RF gun which had a modified back plate to allow the use of INFN-style photocathode pucks. Previously this gun had used a solid wall back plate that also acted as the photocathode**. This presentation describes the different photocathodes that were used during the run and the various methods employed to prepare them for use. An initial cathode which was based on a solid Mo puck with the thin film of Cu grown using magnetron sputtering was seen to give high initial QE but a very fast degradation rate. Subsequent cathodes were hybrids with a Mo body and a solid copper tip for the active area. Several cathodes prepared using alternative techniques were employed, giving varied initial QE and lifetime. The final cathode used had satisfactory QE and a long enough lifetime to deliver a six month period of beam exploitation for external facility users. * D. Angal-Kalinin, et al, ‘Design, specifications, and first beam measurements of the compact linear accelerator for research and applications front end’ Physical Review Accelerators and Beams 23 (2020) 044801 ** T.C.Q. Noakes, et al, ‘Photocathode preparation and characteristics of the electron source for the VELA/CLARA facility’ Proceedings of the International Particle Accelerator Conference 2018 (IPAC-18), THPMK063, 2018, Vancouver, Canada
Paper: TUPA032
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA032
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
TUPA034
High-power experiment of a C-band photocathode gun
1412
The C-band electron gun is an attractive option for lower emittance with compactness. In this paper, a new C-band photocathode gun has been developed. The electron gun experienced a high-power test and had preliminary reached the designed gradient on the cathode. The high-power test results are the basis of the beam dynamics design and beam testing.
Paper: TUPA034
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA034
About: Received: 08 May 2023 — Revised: 09 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA035
Negative electron-affinity activation procedures for GaAs photocathodes at Photo-CATCH
1415
State-of-the-art spin-polarized photo-electron sources use GaAs-based photocathodes to provide electron beams with high degrees of spin-polarization. Such photo-guns are required to operate with both quantum efficiency and cathode lifetime as high as possible in order to meet the requirements of high-current applications such as energy-recovery linacs and colliders. Both quantum efficiency and lifetime are determined by the quality of the thin surface layer, typically consisting of Cs in combination with an oxidant, required for GaAs photocathodes to achieve negative electron affinity. This layer is applied during a so-called activation process. It is therefore of great interest to optimize and standardize this procedure in order to provide the best possible conditions for reliable photo-gun operation. This contribution presents the analysis of bulk-GaAs activations using Cs and O conducted at the Photo-CATCH test stand. The effects of Cs and O partial pressures on final quantum efficiency and lifetime, as well as the duration of the activation process were scrutinized in order to find an optimal partial pressure ratio at a reasonable duration of the procedure.
Paper: TUPA035
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA035
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA037
Ultrahigh vacuum S-band gun and advanced photocathode studies at Tsinghua University
1418
High brightness photoinjectors demand low thermal emittance and high electric field to deliver brighter electron beams for modern accelerator-based scientific instruments. High quantum efficiency, low thermal emittance photocathodes, mainly semiconductors, easily degrade in poor vacuum conditions and could not operate with an extended lifetime. Therefore, an ultrahigh vacuum electron gun is necessary to accommodate advanced photocathodes for high performance and reliable operation. In this paper, we report on the development of an ultrahigh vacuum, high gradient S-band gun at Tsinghua University. The gun geometry is redesigned to reach more than one order of magnitude improvement of the vacuum level at the photocathode. Preliminary commissioning results of the new gun will be presented. The new gun and beamline will partially serve as a test facility for advanced semiconductor photocathodes. We will also report on the design and commissioning results of an alkali antimonide photocathode deposition system.
Paper: TUPA037
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA037
About: Received: 03 May 2023 — Revised: 05 Jun 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
TUPA038
Effects of bulk material properties on RF surface resistivity
1422
Several concepts for future linear colliders are dependent on very high gradient normal conducting RF cavities achieved by operation at cryogenic temperatures in order to reduce breakdown rates (BDR). These maximum fields are intended to be in excess of 200 MV/m. The concepts include the ultra compact Xray free electron laser and the C$^3$ collider. The theory involved with the complex physics of breakdown is a diverse and rich field of study. Most results are empirical so continued understanding of the phenomena becomes necessary. One contributing factor to the reduced BDR is the increased hardness at cryogenic temperatures of the copper. in order to test that assumption we can consider obtaining hardness improvements from the alloying of copper with silver. We will here present a preliminary theory of this alloy based improvement especially with respect to an improved understanding of the surface resistivity using our previously established theory improvements which go beyond the usual Reuter and Sondheimer explanation. We will compare this to quality factors measured in Cband pillbox cavities as a function of temperature.
Paper: TUPA038
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA038
About: Received: 03 May 2023 — Revised: 13 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
TUPA039
Temperature stability in CrYogenic Brightness-Optimized Radiofrequency Gun (CYBORG)
1425
X-ray free electron lasers (XFEL) and other x-ray producing light sources are large, costly to maintain, and inaccessible due to minimal supply and high demand. In addition, concepts for future electron colliders benefit from cost reduction size is reduced through normal conducting RF cavities are operated at very high gradients. It is advantageous then to consider miniaturizing electron linacs through a variety of means. We intend to increase beam brightness from the photoinjector via high gradient operation (>120 MV/m) and cryogenic temperature operation at the cathode (<77K). To this end, we have fabricated a new 0.5 cell CrYogenic Brightness-Optimized Radiofrequency Gun (CYBGORG). CYBORG serves three functions: a stepping stone to a higher gradient cryogenic photoinjector for an ultra-compact XFEL (UCXFEL); a prototype for infrastructure development useful for concepts such as the Cool Copper Collider (C^3); and a test bed for cathode studies in a heretofore unexplored regime of cryogenic and very high gradient regime relevant for the National Science Foundation Center for Bright Beams. We present here commissioning status of CYBORG and the associated beamline focusing in particular on C-band RF power development and thermal balancing of the gun in the cryogenic environment.
Paper: TUPA039
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA039
About: Received: 03 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
TUPA040
Longitudinal beam dynamics and RF requirements for a chain of muon RCSs
1428
A facility for the collision of muons offers a unique path to a compact lepton collider with an energy reach in the multi-TeV regime, well beyond the possibilities of conventional electron accelerators. However, due to the short lifetime of muons, the constraints for acceleration and collisions are very different. An extremely fast energy increase in combination with intense and ultra-short bunches is essential for a high muon survival rate and luminosity. A chain of rapid cycling synchrotrons (RCS) for acceleration from around 60 GeV to several TeV is proposed by the International Muon Collider Collaboration. We study the longitudinal beam dynamics and radio-frequency (RF) requirements for these RCSs with respect to induced voltages from intensity effects. A high synchrotron tune due to the large RF voltages is a particular challenge. We present simulation results of the longitudinal bunch distribution to determine the number of RF stations distributed over the RCS to mitigate that large tune. The impact of the induced voltages from short-range wakefields and single- as well as multi-turn beam loading is analyzed, for both fundamental and higher-order modes.
Paper: TUPA040
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA040
About: Received: 28 Apr 2023 — Revised: 11 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA041
Ionization of the muonium using the electron
1432
The muonium is the bound state of the positive muon and the electron. The muoium can be ionized using a dedicated laser to produce the ultra-slow muon beam. It is one idea that the dense electrons may be used as a substitute of the ionization laser for the muonium. The preliminary study is reported for the ionization of the muonium using the electron.
Paper: TUPA041
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA041
About: Received: 03 May 2023 — Revised: 09 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA043
An electron model of vertical FFA accelerator for Harmonytron
1434
A new type of accelerator called Harmonytron has been proposed. The Harmonytron is based on a scheme of vertical Fixed-Field Alternating gradient (vFFA) focusing with harmonic number jump beam acceleration. An electron model of vFFA accelerator is under development at Kyushu University. The current status of the vFFA accelerator will be discussed.
Paper: TUPA043
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA043
About: Received: 02 May 2023 — Revised: 15 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA044
FFA design study for a high intensity proton driver
1437
As an option for the proton driver for the next generation spallation neutron source (ISIS-II) at the Rutherford Appleton Laboratory (RAL), a Fixed Field Alternating Gradient Accelerator (FFA) is being considered. A prototype accelerator has been designed, referred to as FETS-FFA, to demonstrate flexible handling of beam repetition for users and high intensity operation with minimum beam loss. FETS-FFA takes the 3 MeV beams from RAL's Front End Test Stand (FETS) linac and accelerates them to 12 MeV. FD spiral optics have been adopted as the basic focusing structure, which allows the operating point to be chosen along the diagonal in tune space. Flexible beam repetition will be demonstrated by RF beam stacking at the extraction energy, which enables users to choose different (lower) repetition rates independent of the acceleration cycle. For high intensity beam study, several schemes of injection painting are being considered. At the injection energy, the space charge tune shift can be easily exceed -0.3. This paper discusses the overall design, while further details of each aspect of the accelerator, including hardware, are presented in separate conference papers.
Paper: TUPA044
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA044
About: Received: 02 May 2023 — Revised: 05 Jun 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA045
High-energy single-cycle terahertz sources for compact particle accelerators and manipulators
1440
Novel accelerator concepts such as all-optical terahertz (THz) based compact accelerators demand high-power THz sources that are robust in order to enable reliable testing. THz sources based on the tilted-pulse front scheme have become the method of choice for table-top, high-energy, single-cycle (SC) THz generation due to both their versatility and scalability. However, due to the noncollinear interaction geometry, fine-tuning of the performance and tailoring of the THz beam properties requires a detailed understanding of the dependences on the setup parameters. Here, we present on the use of multi-dimensional parameter scans to systematically map out sensitivities of such THz sources on the primary interaction parameters and show experimental characterization of a robust, high-energy, single-cycle THz source designed and constructed based on these findings. This setup delivers pulses centered at 300 GHz with pulse energies exceeding 400 µJ at 52 Hz repetition rate and a shot-to-shot rms stability < 3.8%. Such robust, high-energy THz sources are crucial for the development of next generation THz-driven particle accelerators and manipulators.
Paper: TUPA045
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA045
About: Received: 10 May 2023 — Revised: 10 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
Compact Single-Side-Pumped Terahertz-Driven Booster Accelerator
Recent demonstrations of terahertz (THz) powered accelerators and beam manipulators have opened a pathway towards miniaturized accelerators that promise to enable new science due to unique features such as reduced timing-jitter and reduced space-charge broadening of the electron bunches. Here, we present on the development of a matchbox sized multi-layered accelerator structure powered by a single few-cycle terahertz pulse and designed to boost the output of a 55 keV DC electron gun to energies up to ~ 400 keV. An integrated actuated mirror is used to interfere the transversely injected THz pulse with itself, creating a transient standing wave optimized for efficient acceleration of the electrons. In contrast to a double-side-pumped approach this reduces the complexity of the optical setup by using the available THz energy more efficiently. We demonstrate first acceleration and map out the booster performance by varying the injection timing of the electrons and fine-tuning of the transient THz standing wave. Such a table-top source is promising for ultrafast electron diffraction experiments as well as precursor for subsequent acceleration to MeV energy by THz-driven LINACs.
TUPA047
3D polarisation of a structured laser beam and prospects for its application to charged particle acceleration
1443
A Structured Laser Beam (SLB) is a type of optical beam with spatially inhomogeneous 3D polarisation structures. Generating SLBs from vector beams allows the creation of Hollow Structured Laser Beams (HSLB) with a dark central core. In this way, atypical electric and magnetic field vectors, which are purely longitudinally polarized in the dark zones of the beam, are obtained. The SLB spatial distribution can also include regions with both the electric and magnetic fields longitudinally polarized and oriented in the same or opposite directions. The SLB has a transverse distribution similar to that of a Bessel beam but can theoretically propagate to infinity, therefore giving the potential to generate strong, longitudinally oriented electric fields over long distances, which could possibly allow the acceleration of charged particles. The results of the study of this phenomenon, including simulations of the spatial distribution of the electromagnetic field components, are presented in this paper.
Paper: TUPA047
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA047
About: Received: 10 May 2023 — Revised: 11 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
TUPA049
Design of an E x B chopper based on permanent magnets
1446
Chopper systems are typically used to provide beam time structure and ensure the safety of accelerator operations by deflecting the beam away. The reliability of conventional chopper is entirely based on high-voltage (HV) pulsed power supplies, and when it fails to charge the electrostatic deflection plate, the beam cannot be cut off and will enters the downstream accelerator. To meet the strict beam stopping time requirements of the China Initiative Accelerator Driven System (CiADS), improvements in safety are necessary. To address this issue, a novel E × B chopper has been physically designed, which is based on a permanent magnet and an electrostatic deflection plate. This design ensures the safety of the accelerator while providing the necessary pulse waveform. The device is small and highly reliable, making it suitable for use in most accelerators. The device is small and highly reliable, making it suitable for use in most accelerators. Moreover, beam dynamics simulations of the chopper have been conducted to determine its influence on beam quality, and beam cutting capability analysis has been performed.
Paper: TUPA049
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA049
About: Received: 03 May 2023 — Revised: 25 May 2023 — Accepted: 25 May 2023 — Issue date: 26 Sep 2023
TUPA050
Design of a compact superconducting recoil separator for HIE-ISOLDE
1450
The High Intensity and Energy ISOLDE facility (HIE-ISOLDE) at CERN has unprecedentedly expanded the research capabilities to investigate the structure of the atomic nucleus and the nuclear interaction. In this context, to meet the high-resolution mass spectroscopy required by the HIE-ISOLDE physics program, an innovative spectrometer is currently being designed, the ISOLDE Superconducting Recoil Separator (ISRS). The ISRS is based on a compact storage ring formed of iron-free superconducting multifunction Canted-Cosine-Theta (CCT) magnets. In this contribution, we report on the current status of the ISRS design, paying special attention to its optics configuration and beam dynamics aspects.
Paper: TUPA050
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA050
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA051
TeV/m acceleration in laser-graphene interactions
1454
Electron acceleration in solid-state plasmas is of interest within the Laser Wakefield Acceleration (LWFA) research. Layered nanostructures such as graphene nanoribbons can be used as targets for intense UV lasers to generate and accelerate electron bunches. We present numerical Particle in Cell (PIC) simulations of a novel sub-femtosecond self-injection scheme which relies on edge-plasma oscillations in a layered graphene target. The scheme delivers 0.4 fs-long electron bunches of 2.5 pC total charge with an energy gain rate of 4.8 TeV/m. These parameters are unprecedented and, if confirmed experimentally, may have an impact on fundamental femtosecond research.
Paper: TUPA051
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA051
About: Received: 01 May 2023 — Revised: 07 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA052
Driver-witness configuration in CNT array-based acceleration
1457
Solid-state plasma wakefield acceleration might be an alternative to accelerate particles with ultra-high accelerating gradients, in the order of TV/m. In addition, due to their thermodynamic properties, 2D carbon-based materials, such as graphene layers and/or carbon nanotubes (CNT) are good candidates to be used as the media to sustain such ultra-high gradients. In particular, due to their cylindrical symmetry, multi-nm-aperture targets, made of CNT bundles or arrays may facilitate particle channelling through the crystalline structure. In this work, a two-bunch, driver-and-witness configuration is proposed to demonstrate the potential to achieve particle acceleration as the bunches propagate along a CNT-array structure. Particle-in-cell simulations have been performed using the VSIM code in a 2D Cartesian geometry to study the acceleration of the second (witness) bunch caused by the wakefield driven by the first (driver) bunch. The effective plasma-density approach was adopted to estimate the wakefield wavelength, which was used to identify the ideal separation between the two bunches, aiming to optimize the witness-bunch acceleration and focusing. Simulation results show the high acceleration gradient obtained, and the energy transfer from the driver to the witness bunch.
Paper: TUPA052
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA052
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
A DSRD-Based Pulse Forming Network for a Dielectric Wall Accelerator
Purpose: In the effort to develop a compact dielectric wall accelerator (DWA) system for proton radiotherapy, this work aims to demonstrate the feasibility of a drift step recovery diode (DSRD) based pulse forming network (PFN) to generate high magnitude, nanosecond scale voltage pulses at high repetition rates. Methods: An initial numerical feasibility study was conducted in order to demonstrate the possibility of generating a 17 kV, nanosecond scale pulse with a DSRD-based standard PFN (forward and reverse current branch). Then, a DSRD-based PFN was designed using a magnetic switch, seen in [Figure 1][1] (https://bit.ly/3iMCOHs). Saturation of a transformer discharges a storage capacitor. At maximum current, the DSRD turns off, commuting stored energy to a load. A low energy prototype was developed at SLAC. A 20 kV, high repetition rate (1-10 kHz) prototype is currently being developed. Results: The numerical study demonstrated that a max output of 16505 V with a rise time of 1.11 ns can be generated with a stack of 19 DSRDs. [Figure 2][2] (https://bit.ly/3VGPuhS) presents a 4.9 kV pulse of the low energy prototype. [1]: https://bit.ly/3iMCOHs [2]: https://bit.ly/3VGPuhS
Terahertz Time Stamping Tool Development for SLAC MeV-UED
Mega electron volt (MeV) accelerators used for ultrafast electron diffraction (UED) have provided a unique insight into visualizing elusive ultrafast processes from photochemical reactions and lattice motion, to phase transitions occurring in quantum materials. In this work, we demonstrate recent measurements of strong THz streaking of ultrafast electron bunches generated from an rf photoeinjector using an efficient THz deflector structure. We show that the structure can achieve upward of 1.5 MV/cm of peak THz fields to 3 MeV, 10 fC bunches subsequently improving the timing resolution of single-shot measurements of bunch length and jitter. Such measurements are used to obtain a significant improvement in the MeV-UED timing resolution. With this setup, we have measured coherent charge wave oscillations in photo-excited TaS2 thin film within ~50 fs temporal resolution. These results are essential for the development of a THz timing tool toward new regimes of few femtosecond timing resolution.
Design and Testing of a High-Gradient mm-Wave Accelerator Prototype
Accelerators operating in the mm-wave regime can reach much higher gradients than conventional accelerators due to the favorable scaling of the breakdown threshold with frequency. These structures also have the potential to achieve a much higher shunt impedance, enabling the efficient use of RF power that is critical given the current limitations on high power RF sources in this regime. We report on the design, fabrication, and testing of a 95 GHz linac. Simulations predict this π-mode standing wave accelerator composed of 16 cells will produce an energy gain of 3 MeV for an input power of 1 MW. We report on cold test results characterizing the fabricated prototype, as well as techniques for tuning the cavities. We discuss the outlook for beam tests of this mm-wave accelerator utilizing a field emission gun and injector, as well as extending this approach to higher beam energies.
TUPA059
Study of the transfer and matching line for a PWFA-driven FEL
1461
The development of compact accelerator facilities providing high-brightness beams is one of the most challenging tasks in the field of next-generation compact and cost affordable particle accelerators. Recent results obtained at SPARC_LAB show evidence of the FEL laser by a compact (3 cm) particle beam plasma accelerator. This work is carried out in the framework of the SPARC_LAB activities concerning the R&D on particle-driven plasma wakefield accelerators for the realization of new compact plasma based facilities i.e EuPRAXIA@SPARC_LAB. The work here presented is a theoretical study demonstrating a possible scheme concerning the implementation of an innovative array of discharge capillaries, operating as active-plasma lenses, and one collimator to build an unconventional transport line for bunches outgoing from plasma accelerating module. Taking advantage of the symmetric and linear focusing provided by an active-plasma lens, the witness is captured and transported along the array without affecting its quality at the exit of the plasma module. At the same time the driver, being over-focused in the same array, can be removed by means of a collimator.
Paper: TUPA059
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA059
About: Received: 03 May 2023 — Revised: 06 Jun 2023 — Accepted: 06 Jun 2023 — Issue date: 26 Sep 2023
TUPA060
Laser source and Gabor lens for use within LhARA
1465
The ‘Laser-hybrid Accelerator for Radiobiological Applications’, LhARA*, facility is conceived to study the biological response to ionising radiation, specifically focussing upon the co-called ‘FLASH’ (>40 Gy/min) regime. A high repetition laser, directed at a thin target, will generate high intensity, ultra-short, particle bunches, at up to 15 MeV/u (and subsequent acceleration up to 127 MeV/u, as required). These particles will be guided to one of several end-stations, whereby the effects can be studied via in-vitro or in-vivo experiments using newly developed detectors, existing phantoms, and test samples. The laser driven ion source and capture systems are key technologies for LhARA. We will discuss ongoing R&D into delivery of a laser driven ion source with the required beam parameters, stability and repetition rate. Following the idea originally outlined by Gabor**, the current plan and status of using large volume, high-density, low-temperature, non-neutral plasmas as beam optics within the capture system will also be presented.
Paper: TUPA060
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA060
About: Received: 12 May 2023 — Revised: 22 May 2023 — Accepted: 22 May 2023 — Issue date: 26 Sep 2023
TUPA061
TWAC : EIC Pathfinder Open European project on Novel dielectric acceleration
1468
Particle accelerators are devices of primary importance in a large range of applications such as fundamental particle physics, nuclear physics, light sources, imaging, neutron sources, and transmutation of nuclear waste. They are also used every day for cargo inspection, medical diagnostics, and radiotherapy worldwide. Electron is the easiest particle to produce and manipulate, resulting in unequaled energy over cost ratio. However, there is an urgent and growing need to reduce the footprint of accelerators in order to lower their cost and environmental impact, from the future high-energy colliders to the portable relativistic electron source for industrial and societal applications. The radical new vision we propose will revolutionize the use of accelerators in terms of footprint, beam time delivery, and electron beam properties (stability, reproducibility, monochromaticity, femtosecond-scale bunch duration), which is today only a dream for a wide range of users. We propose developing a new structure sustaining the accelerating wave pushing up the particle energy, which will enable democratizing the access to femtosecond-scale electron bunch for ultrafast phenomena studies. This light and compact accelerator, for which we propose breaking through the current technological barriers, will open the way toward compact accelerators with an energy gain gradient of more than 100 MeV/m and enlarge time access in the medical environment (preclinical and clinical phase studies).
Paper: TUPA061
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA061
About: Received: 05 May 2023 — Revised: 19 May 2023 — Accepted: 19 May 2023 — Issue date: 26 Sep 2023
TUPA062
Cyclotron resonance accelerator for electron beams
1472
Abstract: Electron Cyclotron Resonance Accelerator (eCRA) simulation results are presented for realistic TE111 cavity geometry and finite space-charge beams that confirm the single-particle idealized solutions. The simulations include cavity openings for RF inputs, beam injection, and pumping; RF input couplings that maximize efficiency; a thin window for exit of the accelerated beam; realistic magnetic field profiles; finite diameter multi-Ampere beams. One simulated example is for a copper cavity with Q0 of about 19,000, with RF input power at each port of 12.5 MW, an 8.0-A, 100 keV beam was found to be accelerated to 2.2 MeV, for a pulsed beam power of 17.6 MW at an efficiency of 67%. A wide variety of applications can be envisioned for MW-class eCRA beams with energies in the range 1-10 MeV. Our first proof-of-principle demonstration of eCRA is to provide beams to generate intense X-ray fluxes to enable the replacement of radioactive sources now widely used for sterilization of medical supplies and foodstuffs. This demonstration will be based on use of available S-band components, although the optimal operating frequency for eCRA could be about 1000 MHz. In any case, the possibility of MW-level average power eCRA beams—even with predicted efficiencies >80%--will depend upon the availability of the required RF sources to drive eCRA.
Paper: TUPA062
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA062
About: Received: 03 May 2023 — Revised: 12 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
TUPA064
Simulations and experimental studies for an X-band short-pulse ultra-high gradient photoinjector
1476
A program is under way at the Argonne Wakefield Accelerator (AWA) facility, in collaboration with Euclid Techlabs and Northern Illinois University (NIU) to develop a GV/m-scale photocathode gun, with the goal of producing bright electron bunches. The novel X-band (11.7 GHz) photo-gun (Xgun) is powered by high-power, short rf pulses (9 ns), which are generated by the AWA drive beam in a wakefield structure. In the first series of experiments, the Xgun produced ~400 MV/m peak field on the photocathode surface. The Xgun has also shown exceptional robustness, with no noticeable breakdown observed after being fully conditioned. As a first step towards achieving a complete understanding of the Xgun's performance, we aim to investigate the fundamentals of photoemission in the high-gradient regime. Systematic simulations will be presented for the near-future photocathode thermal emittance measurements.
Paper: TUPA064
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA064
About: Received: 04 May 2023 — Revised: 19 May 2023 — Accepted: 19 May 2023 — Issue date: 26 Sep 2023
TUPA066
Hydrodynamic model for particle beam-driven wakefield in carbon nanotubes
1480
Charged particles moving through a carbon nanotube may be used to excite electromagnetic modes in the electron gas produced in the cylindrical graphene shell that makes up a nanotube wall. This effect has recently been proposed as a potential novel method of short-wavelength-high-gradient particle acceleration. In this contribution, the existing theory based on a linearised hydrodynamic model for a localised point-charge propagating in a single wall nanotube (SWNT) is reviewed. In this model, the electron gas is treated as a plasma with additional contributions to the fluid momentum equation from specific solid-state properties of the gas. The governing set of differential equations is formed by the continuity and momentum equations for the involved species. These equations are then coupled by Maxwell’s equations. The differential equation system is solved applying a modified Fourier-Bessel transform. An analysis has been realised to determine the plasma modes able to excite a longitudinal electrical wakefield component in the SWNT to accelerate test charges. Numerical results are obtained showing the influence of the damping factor, the velocity of the driver, the nanotube radius, and the particle position on the excited wakefields. A discussion is presented on the suitability and possible limitations of using this method for modelling CNT-based particle acceleration.
Paper: TUPA066
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA066
About: Received: 07 May 2023 — Revised: 16 Jun 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
Wakefield Acceleration in Structured Solids : E336 Experiment at FACET-II
Wakefield acceleration in structured solids (nanotubes and crystals) has a promise of very high accelerating gradients and simultaneous continuous channeling focusing. All that can manifest a new, long thought solution of many challenges faced by advanced acceleration techniques. We outline the concept and present the progress and status of the E336 Experiment at FACET-II.
The Design of the Electron and Positron Source for CERN External Beam Lines
The “standard” way of a high energy positron beam in proton accelerator-driven systems includes two stages. Firstly, the proton beam is directed on a target material. The protons produce neutral pions that after a short decay they decay to 2 gamma rays. At the second stage, these gammas are producing electron-positron pairs on a high-Z (typically Pb) converter. Magnets between the target and the converter considerably reduces though does not totally eliminate the hadron contamination. We propose to use a tungsten oriented crystal as the gamma converter. Since an electromagnetic shower in such a crystal is accelerated*, one can drastically reduce the thickness of the converter preserving nearly the same positron yield compared with the amorphous Pb converter. This will considerably reduce the level of hadron background at the converter exit. Moreover, by adjusting the crystal thickness, one can increase the positron yield in a certain energy range. We demonstrate the simulation results of the new scheme using as an example the production of positrons in the H4 beam line of CERN SPS North Area external beam line carried out with Geant4 simulation toolkit**.
TUPA070
MeV-scale simulations and fabrication tests of woodpile-based waveguide for dielectric laser accelerators
1484
Hollow-core dielectric Electromagnetic Band Gap (EBG) microstructures powered by lasers represent a new and promising area of accelerator research since, thanks to the short optical wavelength and to the dielectric's high damage threshold greater accelerating gradients, with respect to the metallic counterparts, can be achieved. In this paper, we present MeV-scale beam-dynamics simulations and fabrication results relative to a silicon, woodpile-based travelling-wave structure operating at the wavelength 𝜆0 = 5 μm. The simulated CST and HFSS electric field has been evaluated and used as input for a space charge tracking code, in order to perform beam-dynamics evaluations on the beam injection and extraction into the proposed structure as well as the evolution of the main beam parameters. We also report on the fabrication of first Si prototypes of the woodpile structure that are obtained by the innovative Two Photon Polymerization fabrication process. This technique allows to reach resolutions down to hundreds of nanometers, offering the possibility to print Si-rich structures, or woodpile skeletons to be infiltrated with Si by CVD technique.
Paper: TUPA070
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA070
About: Received: 28 Apr 2023 — Revised: 11 May 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
TUPA071
Simulation of tapered co-propagating structures for dielectric laser accelerator
1488
One of the key aspects to provide on chip acceleration in Dielectric Laser Accelerators (DLA) from tens of keV up to MeV energies is the phase velocity tapering. This paper presents the simulated performance of sub-relativistic structures, based on tapered slot waveguides. We engineered channel/defect modification in order to obtain a variable phase velocity matched to the increasing velocity of the accelerated particles. Additionally, we present a hollow-core relativistic electromagnetic band gap (EGB) accelerating waveguide. In DLA structures co-propagating schemes are employed for higher efficiency and smaller footprint compared to the cross-propagating schemes. In this respect, we envisage tapered continuous copropagating structures that simultaneously allow wave launching/coupling, beam acceleration, and transverse focusing. The main figures of merit, such as the accelerating gradient, the total energy gain, and the transverse focusing/defocusing forces, are evaluated and used to guide the optimization of the channel/defect modification. Index terms: Dielectric Laser Accelerators (DLA), Photonic Crystal, Dielectric Waveguides
Paper: TUPA071
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA071
About: Received: 04 May 2023 — Revised: 09 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
Plasma-accelerator-based linear beam cooling systems
Plasma-based accelerators enable compact acceleration of beams to high energy and are being explored as a potential technology for future linear colliders. Conventional linear colliders require damping rings to generate the required beam emittance for particle physics applications. We present and discuss a plasma-based linear radiation damping system that allows cooling of ultrashort bunches compatible with plasma-based accelerators. The plasma accelerating gradients enable relatively compact linear damping systems, and there is a trade-off between system length and the achievable emittance reduction. Final asymptotic normalized transverse beam emittance is shown to be independent of beam energy. The impact of coherent radiation emission is considered.
TUPA075
A w-band corrugated waveguide for wakefield acceleration at the AWA emittance exchange beamline
1492
High gradient radio-frequency structures are of considerable interest in ongoing structure wakefield acceleration research. The prospect of economical accelerators with a small footprint in the sub-terahertz regime shows promise in achieving high gradient and high efficiency, and in that vein, we present a design for a metallic corrugated waveguide designed at 110 GHz. This W-band structure has been optimized in the CST Studio Suite for the maximum achievable gradient of 84.6 MV/m from a nominal Argonne Wakefield Accelerator (AWA) electron bunch at 65 MeV, with a charge of 10 nC and an RMS length of 0.5 mm. When the developed structure is excited with a shaped electron bunch, higher gradient and longer beam propagation distance could be achieved. Simulations are ongoing to test the effects of bunch shaping on the structure's performance, and structure fabrication and cold tests are underway in preparation for a collinear wakefield acceleration experiment at AWA.
Paper: TUPA075
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA075
About: Received: 03 May 2023 — Revised: 12 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA076
Design and test of a metamaterial accelerating structure for Wakefield acceleration
1496
Structure-based wakefield acceleration with nanosecond-long RF pulses is a promising advanced accelerator concept to mitigate the risks of RF breakdown. Advanced structures are required to satisfy the need of a high transient gradient with a short pulse length. A metamaterial (MTM) structure, as a subwavelength periodic structure exhibiting a negative group velocity, could have a higher shunt impedance, thus a higher gradient, compared to structures with the same but positive group velocities. An X-band ‘wagon wheel’ structure has been designed and tested as an accelerating structure for two-beam acceleration. Up to 200 MV/m of gradient has been achieved with an input power extracted from the 65 MeV drive beam at AWA, with a peak power of 115 MW, and a pulse length of 6 ns (FWHM). Evidence has been found towards a new accelerating regime, the breakdown insensitive accelerating regime (BIAR), where breakdown was only observed in the secondary pulse of the transmitted RF signal while the primary pulse (useful for acceleration) was not interrupted. This experiment could lead to high-gradient wakefield acceleration and new knowledge in the breakdown physics in the short-pulse regime.
Paper: TUPA076
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA076
About: Received: 03 May 2023 — Revised: 19 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
TUPA077
Design and modeling of dielectric a wakefield accelerator with plasma ionized witness bunch
1499
A planned experiment at the Argonne Wakefield Accelerator (AWA) facility will demonstrate the plasma photocathode concept, wherein precise laser-based ionization of neutral gas within the wakefield driven by a relativistic particle beam generates a high brightness witness beam, which is accelerated in the wakefield. Replacing the plasma wakefield acceleration component with a dielectric wakefield acceleration scheme can simplify experimental realization by relaxing requirements on synchronization and alignment at the expense of accelerating gradient. However, this places rigorous constraints on drive beam dynamics, specifically charge, size, and relative separation. This paper presents progress on the design of such a hybrid scheme, including improved simulations accounting for anticipated beam properties and revised structure characteristics.
Paper: TUPA077
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA077
About: Received: 04 May 2023 — Revised: 19 May 2023 — Accepted: 19 May 2023 — Issue date: 26 Sep 2023
TUPA080
Demonstration of transverse stability in an alternating symmetry planar dielectric structure
1502
Dielectric wakefield acceleration (DWA) is a promising approach to particle acceleration, offering high gradients and compact sizes. However, beam instabilities can limit its effectiveness. In this work, we present the result of a DWA design that uses alternating gradients to counteract quadrupole-mode induced instabilities in the drive beam. Through simulation and experimental results, we show that this approach is effective at suppressing beam breakup, allowing for longer accelerating structures. We have designed and fabricated a new apparatus for positioning the DWA components in our setup. This allows us to precisely and independently control the gap in both transverse dimensions and consequently the strength of the destabilizing fields. Our results show that the use of alternating gradient structures in DWA can significantly improve its performance, offering a promising path forward for high-gradient particle acceleration.
Paper: TUPA080
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA080
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA081
Commissioning of the RFQcb at the Isolde Offline 2 target test facility
1506
The Offline 2 mass separator laboratory is part of the CERN-ISOLDE Offline facilities - a suite of installations required to perform essential quality control on target and ion source units before irradiation at CERN-ISOLDE. The facility is also used for offline studies as a prerequisite before conducting any beam development on-line, especially establishing systematic effects. The Offline 2 separator resembles the online CERN-ISOLDE Frontend and employs identical services such as beam instrumentation, gas system, laser ionization and the equipment control system. The facility is able to generate dc as well as bunched non-radioactive beams up to an energy of 60 keV. The ion beams can be cooled and bunched in an unmodulated RFQ. In order to study effects of the RFQ buffer gas on the formation of molecular species, a dedicated identification setup is required. This work presents the current status of the commissioning of RFQ and results of its first operation. Furthermore, we show the first results of beam emittance measurements, which are compared to 3D beam dynamic simulations. We present the ongoing installation of a Magnetof ion and Wien filter behind the RFQ, respectively.
Paper: TUPA081
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA081
About: Received: 04 May 2023 — Revised: 22 May 2023 — Accepted: 22 May 2023 — Issue date: 26 Sep 2023
TUPA082
Beam loss monitoring through emittance growth control and feedback with design
1510
Beam intensities and powers being increasingly strong, installations increasingly large, the need to reduce losses and costs (i.e. dimensions) becomes essential. Improvements are possible by increasing the acceptance in the two transverse planes. For example for LEBT lines and radioactive beams, a large geometric acceptance allows efficient transport of reaction products that have large phase space dimensions downstream of the TIS. For low intensities, the flux is preserved to allow maximum intensity on target (reactions with low cross section). We investigate the solution to control the beam line acceptance by measuring the emittance growth and a feedback with the design, e.g. pole shape and high-order modes of the fields. This is possible with detection of very low intensities of the halo and beam loss monitoring.
Paper: TUPA082
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA082
About: Received: 03 May 2023 — Revised: 12 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
TUPA083
Transport studies of low energy radioactive ion beams produced by photofission at ALTO-LEB
1514
The ALTO research platform at the Laboratoire de physique des 2 infinis Irène Joliot Curie (IJCLab) is dedicated to wide-ranging research in nuclear physics, nuclear astrophysics and interdisciplinary activities such as health physics. ALTO-LEB is the low energy beam area of ALTO where neutrons rich exotic nuclei are studied. A new precision experiment is being installed at the ALTOLEB facility : a double Penning trap mass spectrometer MLLTRAP coupled with a RadioFrequency Quadrupole Cooler and Buncher (RFQCB). This last device requires low energy beams with low emittance, low energy dispersion and with few contaminants. This paper focuses on the beam transport at ALTO-LEB, from the target-ion source vault to the RFQCB. Simulations of the ions extraction from the ion source and beam transport calculations are being presented in this work. Those results are also directly connected to the reliability of ALTO-LEB beam lines initiated at IJCLab in 2018.
Paper: TUPA083
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA083
About: Received: 11 Apr 2023 — Revised: 05 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
Study and optimization of an hybrid crystal-based positron source for the FCC-ee
A crystal-based hybrid e+ source could be a good alternative to conventional sources based on the e- conversion into e+ in a thick target and is currently under consideration for the FCC-ee [1]. In a hybrid source an e- beam crosses a thin oriented crystal with emission of channeling radiation, featuring enhanced photon flux w.r.t. Bremsstrahlung [2]. It results in an increase in the number of e+ produced at the converter target positioned after the crystal. This allows to reduce the converter thickness and decrease the deposited energy and Peak Energy Deposition Density (PEDD) in it. Here we present the optimization of the hybrid source for the FCC-ee case performed via Geant4; a W crystal was selected as radiator and different configurations were considered; with/without collimators or with/without a sweeping magnet between the crystal radiator and the converter target. In all these cases, a huge reduction of PEDD in the converter was shown. The Geant4 model was benchmarked with experimental tests at DESY TB with 6 GeV electrons [3] and CERN PS&SPS with 6 and 20 GeV e-beams. The tests were performed for either the W crystal and other alternative crystals, e.g., diamond or Ir. The simulation tool is now ready for more sophisticated simulation of the full chain of the injection system. References [1] I. Chaikovska et al 2022 JINST 17 P05015 [2] R. Chehab, V. Strakhovenko and A. Variola, NIM B 266 (2008) 3868 [3] L. Bandiera et al., Eur. Phys. J. C 82 (2022) 699
TUPA086
A positron source demonstrator for future colliders
1518
Regarding high current e+ sources, the almost universal usage of target-based production schemes combined with conventional capture technology has led to poor transmission efficiencies. This long-standing difficulty to handle the extreme e+ transverse emittance and energy spread has been a major impediment for future, high luminosity lepton collider designs. The PSI Positron Production (P-cubed or P$^3$) experiment, framed in the FCC-ee study, is a demonstrator for a e+ capture system with potential to improve the state-of-the-art e+ yield by an order of magnitude. The experiment will be hosted at the SwissFEL facility at PSI as of 2025, where installation works are ongoing. This paper is an overview of P$^3$, with a particular focus on the novel capture system and its effects on the beam dynamics. A concept for the experiment diagnostics is also introduced.
Paper: TUPA086
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA086
About: Received: 26 Apr 2023 — Revised: 05 Jun 2023 — Accepted: 05 Jun 2023 — Issue date: 26 Sep 2023
TUPA087
A pulsed muon source based on a high-repetition-rate electron accelerator
1522
Muons have been playing an important and unique role in both fundamental physics and applied sciences; Recent results of the muon magnetic anomaly hint at physics beyond the Standard Model; Muon spin rotation techniques have been widely applied to the study of superconductivity and magnetic materials. A typical muon experiment measurement time of 10 muon lifetimes means that an ideal muon source should operate at around 50 kHz in the pulsed mode. However, current muon sources are either driven by several 10 Hz pulsed proton accelerators (e.g. J-PARC) or DC proton accelerators (e.g. PSI), resulting in low-duty cycles for many types of muon experiments. Here we explore the use of a high-repetition-rate pulsed electron beam at the Shanghai SHINE facility as a muon source driver. SHINE is based on an 8-GeV CW superconducting RF linac, with a bunch rate of 1 MHz and a bunch charge of 100 pC. Downstream of undulators, the electron beam is deflected and absorbed in a beam dump. Based on a GEANT4 Monte Carlo simulation, we estimated the maximum intensity of the muon beam to be around $10^{9}$. The main production channels are photo-nuclear and Bethe-Heitler processes and each of these processes generates muon beams with different kinematics and time profiles. Such muon beams can improve the performance of current muon physics experiments such as the muonium to anti-muonium conversion and the muon spin rotation technique.
Paper: TUPA087
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA087
About: Received: 16 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
TUPA088
Feasibility investigation of a low energy laser driven plasma injector for ELSA
1526
The 3.2 GeV electron stretcher facility ELSA at the University of Bonn provides electron beams for fundamental research in hadron, detector and medical physics. The beam is extracted from a storage ring, whose injector consists of a 26 MeV linear accelerator and a 1.2 GeV booster synchrotron. The advent of functional plasma-based electron injectors in the MeV energy range raise the opportunity to replace the conventional Linac, which currently delivers electron pulses of up to 16 nC at a repetition rate of 50 Hz. We conduct a feasibility study of using a plasma based injector for the booster synchrotron. For this, we improve the diagnostic capabilities of the Linac transfer beamline and the injector synchrotron to obtain and verify its acceptance parameters which are to be matched to beam properties from contemporary operated laser plasma accelerator setups. Possible plasma-based facility operating modes are evaluated.
Paper: TUPA088
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA088
About: Received: 03 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
TUPA089
EARLI: design of a laser wakefield accelerator for AWAKE
1529
Following the successful Run 1 experiment, AWAKE has developed a program for Run2 that requires designing and implementing a compact electron source (150 MeV, >= 100 pC) for external injection. The baseline design uses a S- and X-band RF photo-injector gun system. The project EARLI investigates the feasibility of an alternative electron source system using a laser wakefield accelerator (LWFA) to produce this electron bunch. Currently, the EARLI project is in the design phase backed by the preparation of experimental demonstrations to prove the feasibility of this accelerator. The main originality of the chosen approach is that the focus is made exclusively on the final beam-targeted characteristics and the reliability and repeatability of the beam quality. EARLI is a stand-alone injector that consists of three main parts: a laser system, a plasma cell and a transfer line, at the end of which the electron beam is injected in a plasma wave driven by a self-modulated proton bunch. Methods from conventional accelerators are applied to LWFA physics. Each part requires specific expertise, that must be investigated in close coupling with the others. A massive campaign of simulations and optimizations with PIC codes is ongoing while the design of the transfer line, the plasma chamber, diagnostics and the laser are carried out in parallel.
Paper: TUPA089
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA089
About: Received: 08 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
TUPA093
Efficient simulation of multistage plasma accelerators
1533
Plasma accelerators can sustain accelerating gradients of up to ~100 GeV/m. However, reaching the high energies required for future particle colliders requires the acceleration to be performed in multiple plasma stages. Solving the challenges posed by multistage acceleration, such a beam quality preservation, requires the capability of simulating large chains of accelerating stages, something that is typically limited by the high cost of full 3D particle-in-cell codes. Thus, there is a growing need for the development of more efficient models that allow for inexpensive collider studies with reduced physics or dimensionality. Here, we present the implementation of a novel gridless quasistatic algorithm in the Wake-T code that, coupled with a laser envelope solver, allows for accurate and efficient simulations of multistage laser-plasma accelerators with axial symmetry, a critical step toward their realization.
Paper: TUPA093
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA093
About: Received: 03 May 2023 — Revised: 19 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
TUPA094
AWAKE from Run 2a to Run 2b
1537
AWAKE is the first proof-of-concept proton-driven plasma wakefield acceleration experiment. AWAKE’s first phase concluded in 2018, with controlled acceleration of electrons to energies of 2 GeV in a 10-m long plasma cell. AWAKE’s second phase operates since 2021. It has been divided into four stages (Run 2a, Run 2b, Run 2c and Run 2d) to prove step by step good that the required electron beam parameters can be obtained reliably and consistently. The transition from Run 2a to Run 2b, which is scheduled for the first semester of 2023, includes the decommissioning of the current vapor source as well as the installation of a new 10-meter-long step density plasma source. After summarising the motivation for the AWAKE Run 2 programme, this paper will describe the preparation works for such an installation, the challenges linked to the infrastructure and the implementation of scheduling tools for the coordination of the facility.
Paper: TUPA094
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA094
About: Received: 03 May 2023 — Revised: 12 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
TUPA095
Techniques to seed the self-modulation instability of a long proton bunch in plasma
1541
The Advanced Wakefield Experiment (AWAKE) at CERN relies on the seeded Self-Modulation (SM) of a long relativistic proton bunch in plasma, to accelerate an externally injected MeV witness electron bunch to GeV energies. During AWAKE Run 1 (2016-2018) and Run 2a (2021-2022), two seeding methods were investigated experimentally: relativistic ionization front seeding and electron bunch seeding. In the first one, a short laser pulse co-propagates with the proton bunch and ionizes the rubidium vapor, generating the plasma. In the second, a short electron bunch propagates in plasma and drives the seed wakefields. Both seeding methods will be further employed during AWAKE Run 2b (2023-2024) to study their effect on the SM evolution in presence of a plasma density step. In this contribution, we will show the main experimental results and discuss their impact for the future design of the experiment, in particular for Run 2c (starting in 2028), where the plasma will be split in two sections: one dedicated to SM of the proton bunch, and the other to the acceleration process.
Paper: TUPA095
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA095
About: Received: 30 Apr 2023 — Revised: 07 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA097
Characterization of plasma-discharge capillaries for plasma-based particle acceleration
1545
Novel particle accelerators based on plasma technology allow a drastic reduction in size, due to the high accelerating field established inside plasmas, which are created and confined by specific devices. Plasma Wakefield Acceleration experiments are performed at the SPARC_LAB test facility (Laboratori Nazionali di Frascati - INFN) by using gas-filled capillaries, in which the plasma formation is achieved by ionizing hydrogen gas through high voltage pulses. In this work, the characterization of gas-filled plasma-discharge capillaries is presented. Several geometrical configurations are tested, including capillaries with different channel shapes and arrangement of inlets positions for the gas injection. Such configurations are designed in order to enhance the uniformity of the plasma density distribution along the plasma channel, which is necessary to improve particle beam acceleration. Plasma sources are characterized by means of the spectroscopic technique based on the Stark broadening method, which allows to measure the evolution of the plasma density profile along the channel. In addition, the CFD software OpenFoam is used to simulate the dynamics of the neutral gas during the filling of the capillary.
Paper: TUPA097
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA097
About: Received: 06 May 2023 — Revised: 08 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
Control of Electron Injection in LWFA with a Laser-ablated Aluminum Plasma by inserting a thin-layer of different metal.
Laser wakefield acceleration (LWFA) using metal targets has been developed for high-vacuum and high-repetition rate operations compare to the gas targets[1-2]. However, the ionization effect due to high intensity fs laser should be considered as propagating through the plasma and the difference of LWFA mechanisms between aluminum plasma and helium plasma has been investigated with the simulation. The partially ionized aluminum ions are ionized to higher charge state up to Al11+ as the main laser is propagating through the metallic plasma. As comparing to helium plasma case, a lot of electrons are injected into the wake cavity even at lower laser power and the energy of accelerated electrons are decreased. By increasing the plasma density, the charge and the oscillating amplitude of injected electrons can be optimized for betatron radiation. We proposed a structured metal target using a thin Ti or Cu wire in aluminum to improve the beam quality. The aluminum plasma with a thin Ti or Cu plasma zone can be produced by laser ablation. When changing the focal position of fs laser pulse with respect to the position of the thin-layered zone, the injection timing of electrons depleted from Ti or Cu ions can be adjusted. We present and discuss the simulation results depending on the thickness and the position of the thin layer.
Optimization of 200 MeV laser-plasma electron injector target using massive particle-in-cell simulation combined with fluid simulation
As part of the [EuPRAXIA](http://www.eupraxia-project.eu/) project[1], the objective of the PALLAS project is to produce an electron beam at 200 MeV, 30 pC with less than 5% energy spread and lower than 2μm normalised emittance using the IJCLAB-LaseriX laser driver at 10 Hz, 1.5 J and 35 fs. Based on available publications[2,3], we propose a two-chamber gas plasma target with a dopant localised in the first chamber. We then perform on-bench calibrated compressible simulations with the code [OpenFOAM](https://www.openfoam.com) to predict the density profile. The result is then used as input for two massive random scans and a Bayesian optimisation with [SMILEI](https://smileipic.github.io/Smilei/) fast Particle-in-Cell (PIC) simulation varying four input parameters: focal position, laser intensity, dopant concentration and inlet pressure. We further investigate the stability of the optimal working points. The massive amount of PIC results is left as open-source data for further investigation by the scientific community. Such a process can serve as the basis for any input parameters optimisation of a laser-plasma electron source target.
Modeling of Plasma Accelerators with the Exascale Code WarpX
The electromagnetic Particle-In-Cell (PIC) code WarpX has been developed by the U.S. Department of Energy’s Exascale Computing Project, in collaboration with international partners, toward the modeling of plasma accelerators on Exascale Supercomputers. We will give an overview of the code and its latest features, such as collision and QED physics modules. We will also report on the latest algorithmic advances that enable full PIC modeling of plasma accelerators with higher efficiency, including a time-averaged pseudo-spectral PIC solver that enables larger timesteps, a hybrid nodal-staggered PIC loop that provides improved stability, an algorithm to handle particles crossing Perfectly Matched Layers, application of mesh refinement to the modeling of ion motion in a plasma accelerator. All presented features are fully CPU and GPU (Nvidia/AMD/Intel) capable and run to full-scale on the world’s largest supercomputers. The status, examples of applications and future developments will be discussed.
TUPA104
Status and first results from FACET-II towards the demonstration of plasma wakefield acceleration, coherent radiation generation, and probing strong-field QED
1549
FACET-II is a National User Facility at SLAC National Accelerator Laboratory with the goal to develop advanced acceleration and coherent radiation techniques using a 10 GeV electron beam of unprecedented beam intensity with >100 kA peak current and <10 µm spot size, a 10 TW experimental laser system, and a variety of solid, gas and plasma targets. A diverse experimental program will investigate beam-driven plasma wakefield acceleration (PWFA), injection, and control with the aim of demonstrating efficient multi-GeV/m PWFA while preserving emittance and narrow energy spread – as is required to reach the beam parameters for a future linear collider. Complimentary research programs into the application of machine learning for accelerator diagnostics and control, novel techniques for the generation of intense coherent radiation, and probing strong-field quantum electrodynamics (QED) also make use of the facility’s unique beam intensity and laser capabilities. The first year of beam delivery to experiments has focused on user assisted commissioning of beam delivery and experimental systems, including a novel EOS BPM with 10 fs bunch length and 5 µm transverse resolution. This contribution will describe the status of the facility, experimental systems, and novel diagnostics, in addition to reviewing the first scientific developments from User programs including initial progress towards beam-driven PWFA.
Paper: TUPA104
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA104
About: Received: 07 May 2023 — Revised: 14 Jun 2023 — Accepted: 14 Jun 2023 — Issue date: 26 Sep 2023
TUPA105
The EPAC electron transport beamline - physics considerations and design
1553
The Extreme Photonics application Centre (EPAC) is a planned UK national facility. The current intention is for EPAC to use a 1 PW 10Hz laser system to drive laser plasma acceleration with output energies ranging from 100 MeV up to, at least, 5 GeV. The initial design for the electron beam transport of the EPAC facility is presented in this paper. This includes some initial considerations on which type of beam line could be used in order to accommodate as many of the different energies as possible. Subsequently, the 1 GeV option is examined in considerable detail. Field errors as well as misalignments for all magnets in the beam line are examined, both individually and together, as well as multipole errors. Finally, a complete layout of the beam line is produced, this includes all diagnostic locations together with the position of a tape system to remove the laser light post-acceleration.
Paper: TUPA105
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA105
About: Received: 03 May 2023 — Revised: 06 Jun 2023 — Accepted: 06 Jun 2023 — Issue date: 26 Sep 2023
TUPA106
Machine learning-based reconstruction of electron radiation spectra
1557
The photon flux resulting from a high energy electron beam's interaction with a target, such as in the upcoming FACET-II experiments at SLAC National Accelerator Laboratory, should yield, through its spectral and angular characteristics, information about the electron beam's underlying dynamics at the interaction point. This project utilizes data from simulated plasma wakefield acceleration-derived betatron radiation experiments and high-field laser-electron-based radiation production to determine which methods could most reliably reconstruct these key properties. The data from these two cases provide a large range of photon energies; this variation of photon characteristics increases confidence in each analysis method. This work aims to compare several reconstruction methods and determine which best predicts original energy distributions based on simulated spectra.
Paper: TUPA106
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA106
About: Received: 03 May 2023 — Revised: 07 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA107
Studying the basics of plasma physics using long range plasma
1560
Plasma wakefield acceleration (PWFA) is a burgeoning field, attracting much attention as an option to extend acceleration gradients from the present 100 MeV/m level to the TeV/m level. The effort will be expended to resolve the question of the long-term behaviour of the disturbances left behind in the plasma and the time it takes to reach equilibrium after the wakefield interaction occurs. The present limitations on gradient arise from material electromagnetic breakdown thresholds. Methods for exploring the beam's longitudinal and transverse phase space qualities have been developed in the context of an increasing worldwide effort. UCLA LAPD laboratory, with its diagnostics, permits the spatio-temporal resolution of electron density, magnetic field, and electro-magnetic signals in the plasma over long-time scales. We aim to explore intense electron beams for wake excitation available at the LAPD, commissioning the SAMURAI photoinjector and its electron beam production.
Paper: TUPA107
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA107
About: Received: 03 May 2023 — Revised: 15 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA108
Simulation study of betatron radiation for perturbed beams in plasma
1564
Plasma wakefield acceleration (PWFA) is a method for accelerating charged particles using large electric fields sustained by plasma waves (up to hundreds of GV m−1) for the accelerating longitudinal fields. In this project, we will evaluate the impact of perturbations on basic particle motion. These perturbations are affected by any number of terms of the equations of motion. The most important perturbations derive from the fact that the particle beams are not quite monochromatic, the finite spread of energies about the nominal energy. We will discuss the hosing which is a transverse instability due to perturbations. The prototypical parameter set was perturbed in several ways. The main goal of this research is to be able to diagnose the parameters of a beam from the spectral and angular distribution of the betatron radiation which encodes information about the beam-plasma interaction.
Paper: TUPA108
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA108
About: Received: 03 May 2023 — Revised: 18 May 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
TUPA109
EuPRAXIA doctoral network
1567
EuPRAXIA is the first European project that develops a dedicated particle accelerator research infrastructure based on novel plasma acceleration concepts and laser technology. It focuses on the development of electron accelerators and underlying technologies, their user communities, and the exploitation of existing accelerator infrastructures in Europe. It was accepted onto the ESFRI roadmap for strategically important research infrastructures in June 2021 as a European priority. To fully exploit the potential of this breakthrough facility, advances are urgently required in plasma and laser R&D, studies into facility design and optimization, along a coordinated push for novel applications. EuPRAXIA-DN is a new MSCA Doctoral Network for a cohort of 12 Fellows between universities, research centers and industry that will carry out an interdisciplinary and cross-sector plasma accelerator research and training program for this new research infrastructure. This contribution gives an overview of this interdisciplinary network and its research.
Paper: TUPA109
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA109
About: Received: 30 Apr 2023 — Revised: 12 Jun 2023 — Accepted: 12 Jun 2023 — Issue date: 26 Sep 2023
TUPA111
Plasma wakefields produced by transversely asymmetric beams
1571
Particle beams with highly asymmetric emittance ratios are employed at accelerator facilities and are expected at the interaction point of high energy colliders. These asymmetric beams can be used to drive high gradient wakefields in plasmas. In plasma, the high aspect ratio of the drive beam can create a transversely elliptical blowout cavity and the asymmetry in the ion column creates asymmetric focusing in the two transverse planes. The ellipticity of the blowout depends on the ellipticity and normalized charge density of the beam. Simulations are performed to investigate the ellipticity of the wakefield based on the initial driver beam parameters and the corresponding beam transport is discussed.
Paper: TUPA111
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA111
About: Received: 04 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
TUPA114
Extraction of high-charge state neon and krypton from the D-Pace Penning ion source test stand
1574
D-Pace has a self-heated hot-cathode Penning ion source test stand at their Ion Source Test Facility (ISTF). High-charge state production of boron, arsenic, and phosphorous is interesting to the ion implantation industry, as it allows for higher energy implants of these dopants using the same accelerating gradient in a given accelerator system. We use Neon and Krypton as proxy gases to investigate whether the Penning ion source could be used for high-charge state production in ion implanters. We were able to produce charge states up to Ne$^{3+}$ ($>$ 200 $e \mu$A) and Kr$^{6+}$ ($>$ 7 $e \mu$A). The obstacles in using the current Penning ion source test stand are discussed, with comments on how to potentially increase the current output, stability, and lifetime of this ion source.
Paper: TUPA114
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA114
About: Received: 27 Apr 2023 — Revised: 11 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
TUPA115
Development of a spin filter polarimeter for polarization measurement of pulsed H+/D+ ion beam at IMP
1577
Spin is one of the intrinsic properties of particles. However, there are many incomprehensible problems about it. High energy polarized electron-ion collisions will provide unprecedented conditions for the study of spin physics and lead us to the study on the inner structure of matter and fundamental laws of interactions, and other forefronts of natural science. As the Phase II of the HIAF (High Intensity heavy ion Accelerator Facility) project, Electron-Ion Collider in China (EicC)* is under conceptual design phase. The production, acceleration and collision of polarized ions and electrons are essential for EicC accelerator facility. Therefore, R&D work such as key technologies prototyping has already been initiated. A spin polarized ion source for the production of intense proton and deuterium ion beams with high polarization is under development at the Institute of Modern Physics (IMP). Polarization is one of the key characteristics for polarized ion beams. To make the polarization measurement more precise, faster and more convenient, a polarimeter based on nuclear spin filter (SFP for short) is under design, which measures the polarization directly behind the ion source. Scheme of the SFP will be presented, the measurement process, simulations for crucial physical questions and design of theSFP will be discussed.
Paper: TUPA115
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA115
About: Received: 28 Apr 2023 — Revised: 06 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA116
Development of polarized H and D atomic beam source at IMP
1581
Polarized beam is an effective tool in basic research. An Electron-ion collider in China (EicC)*, as a future high energy nuclear physics project, has been proposed. Eicc can provide good research conditions for precision measurements of the partonic structure of nucleon or nuclei and the study on the interactions between nucleons and so on. High quality polarized beam is helpful to the accurate measurement of the relevant experiment date. Polarized proton and deuterium (H&D) beam source is one of the key technologies for EicC. Based on the atomic beam polarized ion source (ABPIS) scheme, a polarized H&D ion source with polarization more than 0.8 and beam current more than 1mA is under construction at the Institute of Modern Physics (IMP), providing theoretical and technical support for the design and construction of Eicc polarized source. In the ABPIS, the separating magnet ensures the electron polarization and the effective transmission of the atomic beam; the radiofrequency transition(RFT) unit ensures that the electronic polarization is converted into deserved nuclear polarization. In order to generate high intensity and high polarization H&D atomic beam, these assemblies need to be precisely designed and optimized. In the paper, an effective method for obtaining the optimal sextupole separating magnet structure will be described in detail; the numerical simulation of the method of adiabatic passage, the design and testing of the RFT units will also be discussed.
Paper: TUPA116
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA116
About: Received: 01 May 2023 — Revised: 09 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA118
AISHa: an ECRIS for nuclear-physics, new clinical protocols and material experiments
1585
The Advanced Ion Source for Hadrontherapy (AISHa) is an ECR ion source operating at 18 GHz, developed with the aim to produce multiply charged ion beams with low ripple, high stability and reproducibility, low maintenance. Due to its unique peculiarity, it is a suitable choice for medical applications, but also to nuclear-physics and material experiments. Two AISHa sources have been realized up to now: the first at INFN-LNS, as a prototype, and the second at the Centro Nazionale di Adroterapia Oncologica (CNAO). The first one, fully commissioned at INFN-LNS, will be used as testbench for the preparation of new beams for Nuclear Physics; R&D activities are also planned within the IONS experiment in order to increase plasma confinement and to refine techniques of non-invasive plasma diagnostics aimed to correlate plasma parameters and beam parameters. The second one recently produced the first beam and it will permit to increase the opportunities provided by the CNAO hospital, with the long-term goal of introducing new ionic species into clinical practice such as helium, oxygen and later also iron and lithium, either useful for bio-spatial research and for experimental and industrial research. In this presentation, the key peculiarity and the experimental results of the Aisha ion source will be presented.
Paper: TUPA118
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA118
About: Received: 08 May 2023 — Revised: 06 Jun 2023 — Accepted: 06 Jun 2023 — Issue date: 26 Sep 2023
TUPA120
Fabrication progress of the prototype spoke cavity for the JAEA-ADS linac
1588
The Japan Atomic Energy Agency (JAEA) has been proposing an accelerator-driven system (ADS) as a future nuclear system to efficiently reduce high-level radioactive waste generated in nuclear power plants. As a first step toward the full-scale design of the CW proton linac for the JAEA-ADS, we are now prototyping a low-beta (around 0.2) single-spoke cavity. The actual cavity fabrication started in 2020. Most of the cavity parts were shaped in fiscal year 2020 by press-forming and machining. In 2021, we started welding the shaped cavity parts together. By preliminarily investigating the optimum welding conditions using mock-up test pieces, each cavity part was joined with a smooth welding bead. So far, we have fabricated the body section and the beam port section of the cavity. By measuring the resonant frequency of the temporarily assembled cavity, we have confirmed that there is no significant problem with the cavity fabrication. In this paper, fabrication progress of the prototype spoke cavity is presented.
Paper: TUPA120
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA120
About: Received: 02 May 2023 — Revised: 10 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA121
Design and optimization of a proton source extraction system for the JAEA-ADS linac
1591
The Japan Atomic Energy Agency (JAEA) is designing a 30 MW continuous wave (cw) superconducting proton linear accelerator (linac) for the Accelerator Driven Subcritical System (ADS) proposal. The JAEA-ADS linac's source must provide a proton beam over 20 mA with an energy of 35 keV and a normalized rms emittance of less than 0.1 π mm mrad. As the extraction system determines the beam properties and quality, systematic optimizations in the geometry and input values of the extraction system design were conducted using the AXCEL-INP 2-D simulation program to satisfy the goal requirements. This work describes the extraction system design and reports the beam dynamics results of the first study for the proton source of the JAEA-ADS linac.
Paper: TUPA121
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA121
About: Received: 27 Apr 2023 — Revised: 09 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA123
ECR ion source with high temperature superconducting REBCO coils
1594
High temperature superconductor REBCO has the property of maintain a high critical current density under strong external magnetic field, which makes a promising material for electromagnets in cyclotron and ECR ion source. Therefore, an ECR ion source using iron-less REBCO coils as electromagnet is under development in Research Center for Nuclear Physics (RCNP), Osaka University. A coil system with 3 circular solenoid coils and 6 racetrack sextupole coils was fabricated, and low-temperature performance tests in 77 K were carried out. The test results upon the stability and capability of magnet field inducing will be presented in this work. The design of the ion source will also be discussed. Results yielded in this research will also be made the best use of the development of a skeleton cyclotron, a compact air-core cyclotron being developed in RCNP, which is also planned to use REBCO coils as electromagnets.
Paper: TUPA123
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA123
About: Received: 30 Apr 2023 — Revised: 08 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA124
Latest PANTECHNIK’s ECR ion sources performances
1597
Electron Cyclotron Resonance Ion Sources (ECRIS) are commonly used as injectors in many accelerator laboratories and industries and therefore, pushing its limit towards very high charge state and intense ions for nuclear and elementary particle physics and low charge state ions for surface treatments & medical purposes. For these applications, several models of ECRIS were designed and developed by PANTECHNIK. This article presents a short description of the latest ECR ion source models delivered to the clients along with their typical beam intensities of low and high charge states of various elements. A focus will be made on our latest Supernanogan source (14.5GHz) which has just been installed at INSP, France. We will present improvements of highly charged ion production as a function of time and the efficiency of the new gas injection design.
Paper: TUPA124
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA124
About: Received: 02 May 2023 — Revised: 12 May 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
TUPA131
High voltage DC gun using distributed Bragg reflector super lattice GaAs photocathode for EIC polarized electron sources
1601
The high-intensity, polarized electron source is a critical component for the electron-ion collider which requires a polarized electron gun with higher voltage and higher bunch charge compared to any existing polarized electron source. At Brookhaven National Laboratory, we have built and successfully conditioned the inverted HVDC photoemission gun up to 350 kV. We report on the performance of GaAs photocathode to generate 70 µA average current and up to 16 nC bunch charge with a long lifetime using a circularly polarized laser at 780 nm wavelength. We discuss the Distributed Bragg Reflector GaAs/GaAsP Super Lattice photocathode performance in the DC gun and the anode bias and voltage impact on the lifetime. The gun also integrated a cathode cooling system for potential application on high-current electron sources. The various novel features are implemented and demonstrated in this polarized HVDC.
Paper: TUPA131
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA131
About: Received: 01 May 2023 — Revised: 08 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA132
Ultra thin Cs3Sb photocathodes with anomalously high quantum efficiency
1605
In this proceeding, we demonstrate the synthesis of epitaxial Cs$_3$Sb films with a high degree of crystallinity on silicon carbide substrates. Films less than 10 nm thin are grown in vacuum and exhibit percent level quantum efficiencies at 532 nm. We find a positive correlation between quantum efficiency and improved crystallinity of the photocathode film, particularly in the longer wavelengths of the visible spectrum. We present a model describing the optical interference effects observed in the SiC - Si substrate multilayer that enhance quantum efficiency of the thin film photocathodes by almost a factor of two at particular wavelengths. Additionally, we characterize the surface and bulk crystallinity of epitaxial Cs$_3$Sb films using both X-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED) in an endeavor to identify relationships between crystalline phases and photocathode performance.
Paper: TUPA132
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA132
About: Received: 05 May 2023 — Revised: 19 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
TUPA133
Alkali-antimonide photocathode transport in a vacuum-sealed canister
1608
The high Quantum Efficiency (QE) and low Mean Transverse Energy (MTE) of alkali antimonide photocathodes enable the production of bright electron beams for a variety of accelerator applications. Growing alkali antimonide photocathodes requires an elaborate growth chamber and an operator with considerable expertise. Moreover, their sensitivity to chemical poisoning requires storage in an ultra-high vacuum environment, which poses a significant challenge to their commercialization. As a step towards commercialization, we developed a “cathode-in-a-can" system to provide photoinjector facilities with high performance, air sensitive photocathodes. This system allows for a cathode to be grown at one facility, shipped in a compact vacuum-sealed canister to another facility, then removed from the canister and transferred to the photoinjector to preserve the cathode’s excellent photo-emitter qualities.
Paper: TUPA133
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA133
About: Received: 05 May 2023 — Revised: 23 May 2023 — Accepted: 23 May 2023 — Issue date: 26 Sep 2023
Correlation between the stoichiometry of $Cs_xSb_y$ and its photoemission properties and oxidation response
Alkali antimonide photocathodes are promising candidates for many high-brightness electron sources due to their low-emittance and high quantum efficiency. However, these materials require ultra-high vacuum (UHV) storage and transport to avoid oxidation, which affects their performance. In this proceeding, we report the synthesis of cesium antimonide cathodes with different stoichiometric ratios. These cathodes are compared in terms of photoemission properties (QE and spectral response) and crystalline structure. The results show that the change in the stoichiometry of the cesium antimonide leads not only to a different spectral response but also demonstrate that cathodes with a lower ratio Cs:Sb are highly resistant to oxygen which makes them great candidates for applications where UHV conditions are not obtainable.
Novel source of electrons in a pyroelectric accelerator
Development of advanced intense and reliable sources of charged particle beams is a direction within accelerator physics on its own right. By changing the temperature of Lithium Tantalate (LiTaO3) single crystal at moderate vacuum conditions leads to generation of strong electric field. The uncompensated polarization during the heating or cooling of the crystal causes the ejection of electrons from the dielectric layer on the surface of the crystal. The electrons ejected either from the crystal or from the target (depending on polarity) are accelerated and gain energy of up to a 100 keV. The energy of these electrons can be determined by measuring the energy spectrum of the X rays that resulted from the electron interactions with the target. The conception of a pyroelectric accelerator enabled us to develop compact (portable) electron source, which does not require an external high-voltage and the use of hazardous materials. It is experimentally confirmed that a crystal installed in a chamber with a residual gas pressure of about 2 mTorr could be used to generate electrons with energy of up to 35 keV. The correlation between monoenergetic electron production and avalanche discharge is discussed. By using double crystal, the combined fields of two polarized crystals will enable us to double the acceleration potential.
TUPA138
Characterisation of a Cs-implanted Cu photocathode
1611
The generation of high--brightness electron beams is a crucial area of particle accelerator research and development. Photocathodes which offer high levels of quantum efficiency when illuminated at visible wavelengths are attractive as the drive laser technology is greatly simplified. The higher laser power levels available at longer wavelengths create headroom allowing use of manipulation techniques to optimise the longitudinal* and transverse** beam profiles, and so minimise electron beam emittance. An example of this are bi-alkali photocathodes which offer quantum efficiency ~ 10% under illumination at 532 nm. Another solution is the use of modified photoemissive surfaces. Caesium has a low workfunction and readily photoemits when illuminated at green wavelengths (~532nm). Caesium oxide has an even lower workfunction and emits at red wavelengths (~635nm). We present data on our work to create a hybrid copper photocathode surface modified by implantation of caesium ions, measuring the surface roughness and probing its structure using MEIS. We measure the energy spread of photoemitted electrons, the QE as a function of illumination wavelength, and the practicality of this surface as a photocathode by assessing its lifetime on exposure to oxygen.
Paper: TUPA138
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA138
About: Received: 10 May 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA139
Thermal and structural analyses of a VHF gun at Tsinghua University
1615
In this paper, a cooling scheme was designed for the THU VHF gun, and simulations of thermal and structural analyses were conducted. A total of 19 independent cooling channels were designed and distributed on the gun to remove the heat generated. The maximum temperature was 67.8 ℃ with a total flow rate of 3.28 L/s and dissipation power of 92.5 kW. The accelerating gap distance decreased by 124 um when heat and vacuum loads were applied. The tuning efficiency was 2.075 kHz/kN, and the maximum stress was 65.2 MPa. It is safe to conclude that the cooling scheme of the THU VHF gun meets the thermal and structural requirements and shows good properties in the temperature, deformation, and stress distributions. Future publications will thoroughly discuss the recent progress of the THU VHF gun.
Paper: TUPA139
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA139
About: Received: 03 May 2023 — Revised: 25 May 2023 — Accepted: 25 May 2023 — Issue date: 26 Sep 2023
TUPA140
Thermodynamic study of ultrafast laser-field emission at nanostructured cathodes
1618
Strong laser-field electron emission enhanced by nanostructures is a growing topic of study, owing to its ability to generate high brightness beams. Experiments have shown that the nanoblade structure, a wedge shape, notably outperforms nanotips in the peak fields achieved. These higher fields result in a brighter emission. In this paper we study the thermodynamics of the electron system restricted to a nanostructure. Thermal diffusion of deposited energy near the apex of the structure is dominated by the electronic distribution on the electron-phonon timescale. We show analytically through use of the temperature-squared heat equation that the nanoblade, owing to its larger opening angle and higher dimensionality, thermomechanically outperforms the nanotip.
Paper: TUPA140
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA140
About: Received: 03 May 2023 — Revised: 07 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
TUPA142
Novel Fabrication Methods and Geometries of Nanoblade Cathodes
1622
Electron beams serve many important roles from free electron lasers to medical imaging. Every time beam brightness is improved, a wide variety of fields take another step forward. Nanopatterned field emission cathodes serve as an excellent opportunity to continue to push the envelope on extreme high brightness beams. Their fabrication is thus of crucial importance to this objective. In the past KOH wet etching was performed to create two atomically sharp ridges. This is done by leveraging the selectivity of KOH to etch along a single plane in the silicon crystal. This process is generally used in micro-machining to create a whole array of atomically sharp ridges and cannot be used to produce less than 2. By adopting a different nanofabrication process, a single ridge can be isolated. Additionally, more flexible nanofabrication techniques can be employed to create novel arrangements of blades, such as concentric rings of ridges.
Paper: TUPA142
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA142
About: Received: 03 May 2023 — Revised: 24 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
TUPA143
Theoretical investigation of real supply current distributions for metallic field emission
1625
Electron field emission and the related process of strong laser-field emission are promising mechanisms for the creation of high brightness beams. These processes deviate from the photoelectric effect in that the normal energy – not the total energy – is the predominant factor determining the likelihood for an electron to ionize. In this paper we continue our investigation of the material normal energy distribution (MNED), which is the supply current as a function of the normal energy. We derive analytical expressions for the MNED and mean transverse energy (MTE) for two cases: that of a smooth Fermi surface, and that of a Bragg plane intersecting Fermi surface in a weakly binding potential. We compare these analytical expressions to results calculated using density-functional theory (DFT) for tungsten and copper surfaces. We find explainable discrepancies between our analytical results and the DFT results for the W(100) direction and the Cu(111) direction, associated with the Fermi surface intersecting a Bragg plane, but otherwise find general agreement.
Paper: TUPA143
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA143
About: Received: 03 May 2023 — Revised: 07 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
CsSb atomically smooth thin films as novel visible light photocathodes
The so-called “green photocathodes”, based on alkali antimonide compounds, are characterized by high efficiency at green light wavelengths (1-10% at 500-550 nm) and excellent charge lifetime, but are easily poisoned in poor vacuum and are usually grown in form of disordered polycrystalline layers. Surface disorder is an extrinsic factor significantly contributing to reduce the transverse beam brightness at the photocathode. State-of-the art deposition techniques have been successfully employed to create smooth and ordered alkali antimonides; for example, epitaxial Cs3Sb photocathodes have been grown by electron diffraction monitored molecular beam epitaxy.* By focusing on structure rather than efficiency, we discovered that atomically smooth films of CsSb can be reproducibly grown on selected substrates. While the quantum efficiency at 505 nm is significantly lower than the Cs3Sb counterpart, this material is still a visible light photocathode (with QE~0.5-1% at 405 nm) and appears to be more robust against contamination. We report a detailed characterization of this phase via x-ray and UV photoemission spectroscopy, angle resolved photoemission spectroscopy and scanning tunneling microscopy.
TUPA145
Beam dynamics studies for the target beamlines of the high brilliance neutron source
1629
Neutrons are an essential tool for studying the structure and dynamics of matter. The High Brilliance neutron Source (HBS) project aims to develop a scalable Compact Accelerator-driven Neutron Source that will enable neutron fluxes at the corresponding instruments comparable to existing fission-based or spallation neutron sources. The full-scale HBS facility is characterized by the simultaneous operation of a suite of neutron instruments subdivided into three target stations, each efficiently operated to deliver different neutron spectra. This is realized by different proton beam timing schemes distributed to the target stations. A corresponding beam line design has been worked out in detail. It will deliver proton beams of up to 100mA and 70MeV from the proton Linac via the target beamlines to the neutron production targets. To ensure the complex pulse structure of the proton beam, a multiplexer magnet system will be installed to generate and distribute the different proton pulse schemes to the target stations. The three individual target stations will be operated at different proton pulse frequencies, where the corresponding proton pulse length is coupled via a fixed duty cycle. Major development steps of this project are the development of a three-field septum magnet, which is an essential part of the multiplexer magnet system, the beam dynamics integration of the multiplexer magnet system into the beamline, and the ion-optical layout of the individual target beamlines.
Paper: TUPA145
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA145
About: Received: 09 Mar 2023 — Revised: 09 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA147
The results of the NSC KIPT subcritical assembly neutron source facility physical start up
1633
Subcritical Assembly Neutron Source facility of the National Science Center “Kharkiv Institute of Physics & Technology” (NSC KIPT), Kharkov, Ukraine is Accelerator Driven System with tungsten or uranium neutron generating target and 100MeV/100kW electron linear accelerator as a driver. The facility physical start up was started in the middle of 2020 fnd completed in August 2022. The program of the facility physical start-up supposes to operate with tungsten neutron generating target and to carry out stepwise fuel element loadings with neutron multiplication factor and reactivity measurements at the end of each loading step. During the physical start up it was supposed to load 38 fuel elements in several loading steps. 200 W electron beam was used for neutron multiplication factor and reactivity measurements. After loading of 37 fuel assemblies the measured value of neutron multiplication factor was 0.941. Because of nuclear safety reasons it was decided to complete the facility physical start up and make some clarifying simulation for 38 loaded in the core fuel assemblies taking into account tolerances for fuel mass, geometry and nuclei data uncertainty to be sure that the value of multiplication factor will be not higher than 0.96. During the the facility start up the results of the reactivity and neutron multiplication factor measurements were in a good agreement with results of Monte-Carlo simulations for NSC KIPT SCA Neutron Source facility.
Paper: TUPA147
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA147
About: Received: 09 May 2023 — Revised: 10 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
TUPA148
Reactivity measurements for the NSC KIPT subcritical neutron source facility
1637
In accordance with the program of NSC KIPT Subcritical Neutron Source physical start up that was approved by State Nuclear Regulator the basic measurement method of reactivity and keff is an area ratio measuring method. In the method, the neutron response of the SCA on the electron beam pulse is measuring. For on-line monitoring of the system reactivity the neutron flux to beam current ratio method was accepted. For brief estimation of the system reactivity and estimation of the critical rate of core loading the one over N method is used. The neutron flux measurement system of NSC KIPT Subcritical Neutron Source is used CFUF34, CFUF54 detector set (6 over graphite reflector inside ADS tank) and CFUF28 (3 outside the core). In the paper, the reactivity and keff measuring methodology and measurement results are presented.
Paper: TUPA148
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA148
About: Received: 09 May 2023 — Revised: 11 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA149
A tungsten neutron-generating target of a neutron source based on a subcritical assembly driven with an electron accelerator
1640
In a subcritical assembly, heavy metals are used to generate additional photo-neutrons using high-energy electrons. One of the options for a neutron-generating target is a set of tungsten plates coated with tantalum. It is promising due to the high neutron yield upon irradiation with high-energy electrons. The operating conditions of a tungsten target exposed to electron beams with an energy of 100 MeV, a pulse beam current of 600 mA, and a power density of 2.5 kW / cm2 impose high demands on the target's tightness, in terms of the release of radioactive products from tungsten to the cooling target water. To protect against chemical corrosion and the ingress of radioactive products of the irradiated material into cooling water, the tungsten target plates are coated with a protective layer of tantalum. The tungsten target worked on a high-energy electron accelerator for 6 months. No radioactive products were detected in chilled water.
Paper: TUPA149
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA149
About: Received: 10 May 2023 — Revised: 11 May 2023 — Accepted: 15 Jun 2023 — Issue date: 26 Sep 2023
TUPA150
Towards optics measurements with a new LEIR BPM system
1644
The LHC Injector Upgrade (LIU) programme forms a cornerstone of the High-Luminosity LHC project. Among its targets, a new Beam Position Monitor (BPM) system has been deployed in the Low Energy Ion Ring (LEIR) to facilitate optics measurements. This paper reports on the commissioning and analysis of turn-by-turn data from the new BPM system. Furthermore, the specific challenges and current limitations in LEIR for achieving long-term coherent excitations with sufficient amplitude for optics measurements are discussed, as well as some of the optics measurements performed so far.
Paper: TUPA150
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA150
About: Received: 03 May 2023 — Revised: 09 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA151
Performance of the Low Energy Ion Ring at CERN with lead ions in 2022
1648
2022 has been a performance consolidation year for the Low Energy Ion Ring (LEIR) at CERN that demonstrated its capability of delivering the target beam parameters required for high luminosity production in the LHC in a reproducible and reliable way. The main steps that have led to the high performance reach of this beam, together with the machine stability improvements deployed, are detailed in this paper.
Paper: TUPA151
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA151
About: Received: 26 Apr 2023 — Revised: 18 May 2023 — Accepted: 18 May 2023 — Issue date: 26 Sep 2023
TUPA153
Investigations of losses on the CERN SPS flat bottom with HL-LHC type beams
1652
The High-Luminosity LHC (HL-LHC) project at CERN aims at doubling the beam intensity and the brightness. To achieve this unprecedented performance, the LHC injectors were upgraded during the Long Shutdown 2 (2019-2021) to overcome limitations such as space charge and beam instabilities. Despite these upgrades, the reduction of beam loss on the flat bottom in the Super Proton Synchrotron (SPS) to reach the target beam parameters remains a challenge, avoiding unnecessary activation. Losses are due to several factors: uncaptured beam in the SPS due to the bunch rotation in the Proton Synchrotron (PS) prior to the transfer, large transient beam loading during multiple SPS injections, and transverse tails reaching aperture limitations. Investigations were conducted with HL-LHC beam parameters, aiming at disentangling the different sources of losses and defining specific observables. Finally, refining the optimal beam parameters for improved transfer between PS and SPS is the objective of the study, as well as the possible need for new hardware such as an additional RF system for beam stability and capture or a dedicated collimation system.
Paper: TUPA153
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA153
About: Received: 02 May 2023 — Revised: 20 Jun 2023 — Accepted: 20 Jun 2023 — Issue date: 26 Sep 2023
TUPA154
Project management structures, processes, and tools for the HL-LHC project
1656
At its restart after a major shutdown in 2029, the LHC will see its interaction regions upgraded by the installation of the HL-LHC equipment, with new Nb3Sn triplets and cold powering system, crab-cavities for crossing angle compensation and luminosity levelling, an upgraded collimation system, and fully remote alignment for the final focusing region. In the following operational runs, the LHC will aim at a tenfold increase of the integrated luminosity compared to the original design. The HL-LHC project features a light project management (PM) structure, with strong delegation of PM tasks to the 19 work-packages structuring the project by expertise areas. Unified processes align the community around a common configuration and performance, while shared tools are applied to budget and schedule management . The paper describes committees and processes applied to run this complex project, within the overall organization and planning of CERN. We explain the procedures ruling decisions and change management in configuration, cost and schedule, detail the responsibility share between project and work-packages and explain how quality standards build a common language across the project.
Paper: TUPA154
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA154
About: Received: 02 May 2023 — Revised: 08 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA155
Budget, procurement and risk management for the HL-LHC project
1660
The HL-LHC project covers the upgrade of the LHC, aiming at collecting an integrated luminosity of 3000 fb-1 equal to a 10-fold increase of the nominal LHC performance. Approved in 2016 for a 950 MCHF budget, the project is shaped by 19 work-packages, covering all expertise areas, from beam dynamics to technical infrastructures. A truly international effort is deployed, where 38 institutes collaborate to supply key technologies, equipment, and manpower. Compensating overcost with saving and descoping, Budget-at-completion has been limited within ~10%. The Make or Buy plan drives procurement, ensuring optimal and timely acquisition conditions through transparency, equality, and competitiveness in accordance with CERN Procurement Rules. Differently from US DoE projects, HL-LHC features no risk contingency, whilst being a technology driver, hence exposed to non-negligible intrinsic risk. Risks are catalogued and followed up, aiming at building resilience, supporting decision making, and applying appropriate cost and schedule risk mitigation measures. The paper describes the methods used in cost, procurement, and risk management, as well as the evolution and challenges in these areas.
Paper: TUPA155
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA155
About: Received: 03 May 2023 — Revised: 07 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA156
An improved procedure for energy matching between PS and SPS at CERN
1663
Energy matching between two hadron synchrotrons is the adjustment of the magnetic bending fields and beam momentum to obtain a correct transfer between the two. Conventionally, energy matching is achieved by turning off the RF system and measuring the revolution frequency of the de-bunching beam in the receiving accelerator. For an ideal circumference ratio, the orbits would then be centred in the two rings. However, this procedure is non transparent, seen that the de-bunched beam cannot be accelerated anymore. Thanks to the Low-Level RF (LLRF) upgrade in the Super Proton Synchrotron (SPS) during the 2019-2021 long shutdown, most LLRF signals have become available in digital form, allowing easy online display, analysis, and storage. In this contribution, we look at the possibility of performing energy matching between the PS and the SPS in a more transparent way, without disabling the RF system. The signals from the beam phase and synchronization loops reveal information on the energy of the beam injected into the SPS. This allows to continuously monitor the transfer frequency error, as well as identify and correct potential long-term drifts.
Paper: TUPA156
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA156
About: Received: 01 May 2023 — Revised: 11 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA157
SPS fixed target spill quality improvements in the longitudinal plane
1667
The SPS proton fixed target beams are spilled via a third integer resonant extraction, for which high momentum spread is beneficial. To increase the momentum spread prior to the slow extraction, the bunches are stretched at the unstable phase by inverting the sign of the RF voltage. The RF phase is then flipped back, and the voltage is turned off when the bunch distribution is rotated to the maximum momentum spread. The past production scheme additionally relied on uncontrolled longitudinal blow-up of the unstable beam during the acceleration ramp. After the major upgrade of the main RF system and a successful impedance reduction campaign, the spill quality was significantly compromised. This contribution summarizes the efforts to recover, and improve, the spill quality. The use of the fourth harmonic RF system and controlled longitudinal emittance blow-up are used for beam stabilization along the ramp. Moreover, RF counter phasing is applied during the first part of the de-bunching to profit from the cavity impedance reduction of the feedback systems.
Paper: TUPA157
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA157
About: Received: 01 May 2023 — Revised: 16 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA158
Beam performance and operational efficiency at the CERN Proton Synchrotron
1671
The injectors for the LHC at CERN underwent a major upgrade during a recent two-year long shutdown in the framework of the LHC Injectors Upgrade (LIU) project. Following this upgrade, the Proton Synchrotron (PS) was restarted in 2021, with the same beam quality as before the upgrade quickly achieved or surpassed. This contribution details the current beam performance for fixed-target and LHC-type beams in the PS and the ongoing activities to improve the operational efficiency by means of automating routine operational tasks.
Paper: TUPA158
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA158
About: Received: 27 Apr 2023 — Revised: 10 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA159
Multi-objective extremum seeking to control drifts in the transverse beam splitting efficiency of the multi-turn extraction at the CERN proton synchrotron
1675
Time-varying fluctuations of the intensity sharing between the islands and the core of the beam extracted via the CERN Proton Synchrotron (PS) Multi-Turn Extraction are the main effects that require manual adjustment for this beam type. To mitigate this, the application of an online controller is explored to further enhance both operational autonomy of the accelerator and physics performance. In this contribution a proof of concept implementation of a multi-objective extremum seeking algorithm is presented. The tuning of the PS parameters, the proper choice of the hyperparameters of the algorithm and the achievements reached during the beam studies are summarised.
Paper: TUPA159
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA159
About: Received: 04 May 2023 — Revised: 19 May 2023 — Accepted: 19 May 2023 — Issue date: 26 Sep 2023
TUPA160
Validation of control loop modeling for power limitation studies with beams for HL-LHC
1679
For HL-LHC intensities, transient beam loading after injection between the Super Proton Synchrotron (SPS) and the Large Hadron Collider (LHC) is expected to push the RF power in the LHC to the limit of the installed system. A detailed understanding of this process is necessary to minimize beam losses during LHC injection. Realistic models of the local SPS and LHC cavity control systems were implemented in the Beam Longitudinal Dynamics (BLonD) simulation suite to model bucket-by-bucket and turn-by-turn transient effects. We show the results of studies and detailed benchmarks of key observables such as bunch-by-bunch spacing, RF power at 2023 beam intensity and transfer functions against theory and measurements.
Paper: TUPA160
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA160
About: Received: 29 Apr 2023 — Revised: 12 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA163
SIS18 operation and recent development
1683
SIS18 will be used as booster for FAIR’s main synchrotron SIS100. In addition, it provides a wide variety of ions from Protons to Uranium for users directly at GSI and FAIR. An upgrade program to enhance the overall performance for the booster operation has been carried out. Part of the upgrade program for booster operation was a complete overhaul of the control system including data supply and timing system. In addition, a new magnetic alloy cavities have been installed for h=2 operation and dual harmonic operation in conjunction with the existing H=4 cavities. The main power supplies have been upgraded to allow reduced cycle times. The vacuum system has been significantly enhanced. Further upgrades and machine studies have been performed to enhance available beam parameters and provide new features for the users. We will report about machine studies and recent operation for FAIR Phase0 experiments utilizing various upgrade measures to enhance overall machine performance.
Paper: TUPA163
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA163
About: Received: 03 May 2023 — Revised: 08 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA164
Simulation and measurement of beam loading effects in magnetic alloy RF cavity of CSNS RCS
1687
Different from the high Q value of ferrite cavity, the Q value of magnetic alloy cavity in CSNS RCS is only about 1.25, the frequency band of impedance is wide, and the beam loading effects is strong. Based on the impedance measurement results, the influence of the beam load effects on the longitudinal distribution of the magnetic alloy cavity in CSNS RCS is studied by simulation, and the induced voltage measured on the machine is consistent with it.
Paper: TUPA164
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA164
About: Received: 08 May 2023 — Revised: 11 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA166
Impact of insertion devices on the SLS 2.0 dynamic aperture
1691
Insertion devices may be also very detrimental for the dynamic aperture of storage rings, since they introduce linear and higher order perturbations on the optics of synchrotrons. It is essential to study these effects to adjust the lattice to compensate for these terms when possible (high order multipole magnets are present in the lattice of the machine), or optimize the design of the IDs to minimize the higher order effects. We applied our analysis to SLS~2.0, the upgrade of the presently running Swiss Light Source (SLS) facility at Paul Scherrer Institut. In particular, we compared the results using an approach based on the calculation of the multipoles computed on the beam reference trajectory and on the kick map calculation.
Paper: TUPA166
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA166
About: Received: 02 May 2023 — Revised: 16 Jun 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA170
Thermal and deformation analysis of a 750 MHz IH-DTL prototype for medical applications
1695
This article presents an IH-DTL prototype, capable of accelerating carbon ion beams from 5 MeV/u to 5.5 MeV/u, for manufacturing and assembling validation in a hadrontherapy linac injector. A multi-physics study is made in CST Studio concerning steady-state thermal, stress and deformation analysis. Convenient water-cooling circuits close to drift tubes are simulated to evaluate field errors and frequency detuning as they can affect directly to beam dynamics.
Paper: TUPA170
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA170
About: Received: 03 May 2023 — Revised: 09 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA171
H11(0) end cells for a 750 MHz IH structure
1699
This article presents a study on the H11(0) end cell of an IH-DTL prototype for accelerating carbon ion beams from 5 to 5.5 MeV/u, which is designed for a hadron therapy linac injector. The voltage across the first and last gap in a drift tube linac tends to drop from a typical uniform voltage distribution along the inner cells. In the case of an IH cavity, the power cost to supply the necessary RF energy in this region is affected by the dimensions of the end cell and gap, as well as the girder undercut. The end cells were modeled in CST Microwave Studio for an appropriate power loss optimization of the most relevant dimensions. The same model also introduced dipole correction based on slanted faces, and transverse fields were analyzed.
Paper: TUPA171
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA171
About: Received: 03 May 2023 — Revised: 11 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA172
SARAF beam commissioning results: injector, MEBT
1703
IAEC/SNRC (Israel) is constructing an accelerator facility, SARAF, for neutron production. It is based on a linac accelerating 5 mA CW deuteron and proton beam up to 40 MeV. As a first phase, IAEC constructed and operated a linac (SARAF Phase I), from which remains an ECR ion source, a Low-Energy Beam Transport (LEBT) line and a 4-rod RFQ. Since 2015, IAEC and CEA (France) are collaborating in the second phase, consisting in manufacturing of the linac. The injector control-system has been recently updated and the Medium Energy Beam Transport (MEBT) line has been installed and integrated to the infrastructure. It has been fully commissioned during the first semester of 2023 for proton and deuteron beams. This paper presents the results of the integration, tests and commissioning of the injector and MEBT.
Paper: TUPA172
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA172
About: Received: 02 May 2023 — Revised: 06 Jun 2023 — Accepted: 06 Jun 2023 — Issue date: 26 Sep 2023
TUPA173
Reverse engineering on IPHI RFQ
1706
The Radio Frequency Quadrupole (RFQ) for the High-Intensity Photon Injector (IPHI) project has been designed and manufactured in the early 2000s. It is now operating at CEA Saclay since 2016 and accelerates a 100-mA continuous beam up to 3 MeV. It is a 6-meter-long, 3 segments vane RFQ, with 352.2 MHz operation frequency and non-constant voltage profile. From this RFQ, a lot of experience has been gained and, based on this feedback, other RFQ were designed at CEA, such as the one for SPIRAL2, LINAC4, or ESS, which are now operating. For maintenance purposes and to simulate the changes before we operate them, a new virtual 3D model has been developed. This model is simplified and may have the same RF performances as the existing one. This paper present this new model.
Paper: TUPA173
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA173
About: Received: 02 May 2023 — Revised: 23 Jun 2023 — Accepted: 23 Jun 2023 — Issue date: 26 Sep 2023
TUPA174
Beam based alignment of focusing solenoids at ARES
1709
ARES is an electron linear accelerator at the SINBAD facility at DESY. It aims to deliver reliable high-brightness beams with energy in the range of 100 to 150 MeV having fs to sub-fs bunch lengths. This is ideal for injection into novel high-gradient acceleration devices such as dielectric laser accelerators and laser-plasma accelerators which feature fields with fs to ps period. The ARES linac has been successfully commissioned. Here we report the results of the beam-based alignment of focusing solenoids of ARES. The alignment is an important part of commissioning and is crucial for the beam quality.
Paper: TUPA174
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA174
About: Received: 01 Apr 2023 — Revised: 21 Jun 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
TUPA175
Injector and synchrotron commissioning of helium ion beams at the MedAustron Ion Therapy Center
1713
MedAustron is a synchrotron-based ion cancer therapy facility located in Austria. Patients are treated with proton and carbon ion beams in an energy range of 62-252 MeV and 120-402 MeV/u, respectively. The facility features three clinical irradiation rooms, among which horizontal and vertical beam lines as well as a proton gantry are available for treatment. A fourth irradiation room is dedicated to non-clinical research. In 2021, a development project started, which aims at commissioning helium ion ($\mathrm{^{4}He^{2+}}$) beam up to the non-clinical irradiation room. A first major milestone was reached by completing the commissioning of helium in the ECR ion source branch, the LEBT and the LINAC section, where the beam is accelerated up to 7 MeV/u. In this work we discuss the challenges and main results achieved during the injector commissioning (i.e. emittance, intensity and transmission efficiency). Furthermore, recent outcomes from the injection of $\mathrm{^{4}He^{2+}}$ beam into the synchrotron as well as acceleration and extraction results are presented.
Paper: TUPA175
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA175
About: Received: 02 May 2023 — Revised: 10 May 2023 — Accepted: 22 Jun 2023 — Issue date: 26 Sep 2023
TUPA176
Alvarez drift tube linac for medical applications in the framework of HITRIplus project
1717
A first beam dynamics and RF design of an Alvarez-type drift tube linac (DTL) has been defined in the framework of the EU project, HITRIplus. Its main application is to be exploited as a carbon (12C4+) and helium (4He2+) ion injector into a compact synchrotron for patient treatment. As a second implementation, helium particle acceleration with a higher duty cycle of 10% enables the possibility for radioisotope production. The 352.2 MHz structure efficiently accelerates two ion species, for A/q=3 and 2, in the energy range of 1÷5 MeV/u and for a beam current of ~0.5 mA. The design extends to a full length of ~7 meters. Permanent magnet quadrupoles are utilized all along the DTL for focusing both ion beams. This paper presents a first-phase analysis towards a realistic DTL design capable of providing full beam transmission and minimum overall emittance increase for two ion beams.
Paper: TUPA176
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA176
About: Received: 08 May 2023 — Revised: 08 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
TUPA177
Comparison of 352 MHz LINAC structures for injection into an ion therapy accelerator
1721
In the frame of ongoing initiatives for the design of a new generation of synchrotron-based accelerators for cancer therapy with ion beams, an analysis of linac designs has been started, to address a critical element with strong impact on performance and cost of the accelerator. The goal is to identify alternatives at lower cost and similar or possibly smaller footprint than the standard 217 MHz injector presently used in all carbon therapy facilities in Europe. As an additional feature, a new linac design can be tailored to produce radioisotopes for treatment and diagnostics in parallel with operation as synchrotron injector. In this paper is analysed the attractive option of moving to 352 MHz frequency, to profit of reliable mechanical designs already developed for protons and of the cost savings that can be obtained using as RF power sources klystrons with a much lower cost per Watt than tubes or solid-state units. The paper will present a Quasi-Alvarez Drift Tube Linac (DTL) version of an injector linac for carbon ions at q/m=1/3 and compare it with recently developed DTL and IH designs. The option of a separated-IH type linac will be also discussed, together with a standard IH design at 352 MHz. Finally, a DTL design at 352 MHz for injection of fully stripped helium ions into the synchrotron will be presented.
Paper: TUPA177
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA177
About: Received: 09 May 2023 — Revised: 09 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA178
Status of the ESS normal conducting linac including beam commissioning to DTL4
1725
The European Spallation Source (ESS) aims to build and commission a 2 MW proton linac ready for neutron production in 2025. Commissioning of the normal conducting section of the linac is underway and previous papers have reported the performance of the microwave-discharge ion source, Radio Frequency Quadrupole (RFQ) and first Drift Tube Linac (DTL) tank. This paper describes the recent assembly, installation, testing and commissioning of an additional threee DTL tanks as well as developments of supporting systems such as RF feedback, control system tools and operating procedures.
Paper: TUPA178
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA178
About: Received: 03 May 2023 — Revised: 08 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA180
Accelerator and beam physics challenges in support of FRIB experiments
1729
The Facility for Rare Isotope Beams (FRIB), a major nuclear physics facility for research with fast, stopped, and reaccelerated rare isotope beams, started operation in May 2022. Since then, five nuclear physics experiments have been successfully accomplished. The experiments with rare isotope beams typically last within 1-2 weeks. Each experiment requires a different primary beam and its energy. It is critical to shortening the accelerator and fragment separator setup time to meet the requirements of the FRIB Users community. Currently, the primary focus in the linac is to reduce the accelerator setup time and ramp up beam power. Many physics applications, including Machine Learning, have been developed and used to set up the accelerator and beamlines. The simultaneous acceleration of multiple charge states of heavy ion beams is routinely used to minimize the beam power deposition on the charge selector slits after the stripper. The challenges in the fragment separator are related to the highly non-linear beam physics due to the large emittance and momentum spread of the isotope beams. Since the iron-dominated SC magnets operate near saturation, the optimization process includes field distributions at different excitation currents. This paper discusses the theoretical and experimental procedures to improve the linac and fragment separator performance.
Paper: TUPA180
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA180
About: Received: 28 Apr 2023 — Revised: 12 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
TUPA181
Linear accelerator for a next generation rare isotope facility
1733
We propose a linear accelerator concept for a Next Generation Nuclear Physics Accelerator Facility - a versatile User Facility with a wide variety and high availability of its instruments and beam time. The concept is based on the simultaneous acceleration of light and heavy ion primary beams. It improves the utilization of the superconducting driver-accelerator capabilities and allows for the simultaneous and complementary rare isotope production in two different targets, namely a thin target for fragmentation of accelerated heavy ion beams, and a thick spallation target for an isotope separation on-line (ISOL) system driven by light ion beams. This approach supports the multi-user operation of the facility, and enables other research driven by light ion beams. The concept is presented as an upgrade of the Facility for Rare Isotope Beams (FRIB, MSU) with a 60-MV compact room-temperature continuous-wave light ion injector. The funneling of the light and heavy ion beams as well as their distribution to production targets is discussed.
Paper: TUPA181
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA181
About: Received: 27 Apr 2023 — Revised: 08 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA183
IOTA Proton Injector Beamline Installation
1737
The IOTA Proton Injector (IPI), currently under installation at the Fermilab Accelerator Science and Technology facility, is a beamline capable of delivering 20-mA pulses of protons at 2.5 MeV to the Integrable Optics Test Accelerator (IOTA) ring. First beam in the IPI beamline is anticipated in 2023, when it will operate alongside the existing electron injector beamline to facilitate further fundamental physics research and continued development of novel accelerator technologies in the IOTA ring. This report details the expected operational profile, known challenges, and the current state of installation.
Paper: TUPA183
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA183
About: Received: 03 May 2023 — Revised: 08 Jun 2023 — Accepted: 08 Jun 2023 — Issue date: 26 Sep 2023
TUPA184
A 1-2 GHz stochastic cooling system for antiprotons and rare isotopes
1740
A 1–2 GHz stochastic cooling system is being de-veloped to provide fast 3D cooling of hot secondary beams (antiprotons at 3 GeV and rare isotope ions at 740 MeV/u) at intensities up to 10^8 particles per cycle. For antiproton cooling, cryogenic plunging pick-up electrodes will be used to improve the ratio of Schott-ky signals to thermal noise. To cool hot rare isotope beams quickly, a two-stage cooling (pre-cooling by the Palmer method and main cooling by the notch-filter method) has been decided. This paper presents the recent R&D highlights of this unique stochastic cool-ing system especially the main sub-systems i.e. two cryogenic plunging slotline pick-ups, one Palmer pick-up, and two slot-ring kickers.
Paper: TUPA184
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA184
About: Received: 02 May 2023 — Revised: 12 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA185
Development of a 704.4 MHz CH cavity using additive manufacturing
1744
A novel 704.4 MHz CH structure is under develop-ment. Due to its relatively small spatial dimensions (22 cm in diameter and 33.7 cm in length), the additive manufacturing (AM) technology is an attractive choice for the construction. For a proof of concept, a simplified model with one stem, one drift tube, and a small part of another stem was printed with copper. This structure was also foreseen for CW operation, so the design of the water-cooling channels inside the drift tubes and stems have been optimized and checked by the Ansys simulation. The progress with the realization of the 704.4 MHz CH structure will be presented.
Paper: TUPA185
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA185
About: Received: 02 May 2023 — Revised: 09 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA186
Advanced basic layout of the Helmholtz LInear Accelerator for cw heavy ion beams at GSI
1747
The design and construction of continuous wave (cw) superconducting (sc) high intensity linacs is a crucial goal of worldwide accelerator technology development. The standalone sc cw heavy ion HElmholtz LInear ACcelerator (HELIAC) is a common project of GSI Helmholtz Centre for Heavy Ion Research and Helmholtz Institute Mainz (HIM) under key support of Goethe University Frankfurt (IAP). In 2017 the first section of the linac has been successfully commissioned and extensively tested with heavy ion beam at GSI, featuring the capability of 216.816 MHz multi-gap Crossbar H-mode (CH) DTL-structures. At present, the first fully equipped cryomodule of the HELIAC is under construction. Six further superconducting CH cavities are being procured. The HELIAC beam dynamics concept foresees a total of twelve CH-cavities in order to accelerate ions with a mass-to-charge ratio of 6 up to a smoothly variable energy in the range 3.5 - 7.5 MeV/u. In this paper, an advanced compact and less complex layout is presented, where the same number of accelerating cavities can be accommodated in three instead of four cryomodules, thus also reducing the number of solenoids and rebunchers, required for beam focusing. In addition, the integration and linking of the HELIAC to the GSI accelerator facility will be outlined.
Paper: TUPA186
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA186
About: Received: 25 Apr 2023 — Revised: 10 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA187
Optimisation of the stem cooling design of the normally conducting Myrrha-CH structures using the example of CH 3
1751
The MYRRHA project (Multi-purpose hYbrid Re-search Reactor for High-tech Applications) is a planned accelerator-driven system (ADS) that will be realised at Mol in Belgium and will demonstrate the feasibility of transmutation of radioactive waste on an industrial scale. The planned accelerator, which is to provide the 600 MeV proton beam, consists of a normal-conducting 17 MeV injector that supplies a superconducting LINAC. In addition to a 4-rod RFQ and two QWR rebunch-ers, 17 CH structures are planned in the injector, 15 of which will be used for acceleration and 2 as rebunchers. Now that the construction of the first two CH structures has been completed and they have been tested with per-formance, the next cavities are being prepared for con-struction. Since the next cavities are operated with more power than CH1 and CH2 due to the higher gap voltages re-quired, the cooling of the stems plays a decisive role for reliable operation due to the required cw operation. For this purpose, an insert was developed in several iterative steps that significantly lowers the maximum temperature on the stems.
Paper: TUPA187
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA187
About: Received: 03 May 2023 — Revised: 08 May 2023 — Accepted: 16 Jun 2023 — Issue date: 26 Sep 2023
TUPA189
Operation of copper cavities at cryogenic temperatures
1754
This work is focused on the anomalous skin effect in copper and how it affects the efficiency of copper-cavities in the temperature range 40-50 K. The quality factor Q of three coaxial cavities was measured over the temperature range from 10 K to room temperature in the experiment. The three coaxial cavities have the same structure, but different lengths, which correspond to resonant frequencies: around 100 MHz, 220 MHz and 340 MHz. Furthermore, the effects of copper-plating and additional baking in the vacuum oven on the quality factor Q are studied in the experiment. A “geometric model” based on a spherical Fermi - surface and using the equivalent skin layer model is presented in the paper to calculate the surface resistance which is relevant for the RF power losses in the cavity walls. Finally, Cavity cooling process about the pulsed heat transport from the surface into the bulk copper is simulated. The motivation is to check the feasibility of an efficient, pulsed, ion linac, operated at cryogenic temperatures.
Paper: TUPA189
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA189
About: Received: 02 May 2023 — Revised: 23 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023
TUPA190
The double drift harmonic buncher (DDHB) and acceptance investigations at linac and cyclotron injections
1758
Particle accelerators demand high particle transmission and reduced longitudinal emittance; hence, effective bunching systems are requested. The concept based on an efficient, compact design called “Double Drift Harmonic Buncher - DDHB” fulfills these two requirements for a c.w. or pulsed beam injection into an RFQ, a DTL, or a cyclotron. The proposal is associated with two buncher cavities separated by a drift space and an additional drift at the end of the system for a longitudinal beam focus at the entrance of the next accelerator unit, whose candidates can be one of those mentioned above. The investigations are focused on exploring accurate acceptance rates. To obtain successful and understandable outputs from the DDHB concept, a new multi-particle tracking beam dynamics code called “Bunch Creation from a DC beam - BCDC” has been developed for detailed investigations of space charge effects. It allows to calculate the transformation of intense dc beams into particle bunches in detail with a selectable degree of space charge compensation at every location. This paper presents the results from various investigations with and without space charge effects.
Paper: TUPA190
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA190
About: Received: 03 May 2023 — Revised: 04 Jun 2023 — Accepted: 21 Jun 2023 — Issue date: 26 Sep 2023
TUPA192
Strategies for SPIRAL2 linac heavy-ion beam tuning
1762
Heavy ions have been accelerated for the first time by SPIRAL2 in 2022. A fast method to tune the linac cavities has been used (< 1 hour by now, < 10’ in the future) to obtain a 7 MeV/A 18O6+ beam (50 microA CW). Then an automatic Q/M beam change procedure has been successfully used to directly produce a 18O7+ beam. The goal was to demonstrate the possibility to tune a beam even if its intensity is too low (<10 microA) to be seen by phasemeters (BPM) along the linac. The linac transmission was ~ 100% for both beams and, as expected, the measured output energy was the same. The same oxygen reference beam tuning has been also used to obtain 80 microA of 40Ar14+ at 7 MeV/A. Again, the same method has been used to tune the linac cavities at the RFQ output energy beam (0.73 MeV/A, no acceleration). These different methods and the one used to tune the linac output energy are presented.
Paper: TUPA192
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA192
About: Received: 03 May 2023 — Revised: 06 May 2023 — Accepted: 11 May 2023 — Issue date: 26 Sep 2023
TUPA193
NEWGAIN project at GANIL-SPIRAL2 : design of the new heavy ion injector for the superconducting linac
1765
A new project, NEWGAIN (NEW GAnil Injector), is under development at GANIL, and aims to build a second injector for heavier beams with A/q up to 7, as an extension of the SPIRAL2 accelerator. With this upgrade, SPIRAL2 will provide high intensity beams, from proton to uranium, thus increasing GANIL international competitiveness both in fundamental science and associated applications. This paper presents the layout and describes the main technical components of the new injector, based on 2 ECR ion sources (one of them existing), two LEBT, one RFQ and a MEBT section to transport the beam into the present MEBT connected to the LINAC.
Paper: TUPA193
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA193
About: Received: 03 May 2023 — Revised: 10 May 2023 — Accepted: 12 May 2023 — Issue date: 26 Sep 2023
TUPA194
RF-acceleration studies for the HBS-linac applying alternating phase focusing concepts
1768
The recent layout of the Jülich High Brilliance Neutron Source (HBS) driver linac is based on short crossbar H-mode (CH) cavities operated at a fixed synchronous phase. In the last decades the computing power for the development of linacs, available to physicists and engineers, has been increased drastically. This also enabled the accelerator community to finally carry out the required R&D to generate further the idea of drift tube linacs with alternating phase focusing (APF) beam dynamics, originally proposed in the 1950s. This focusing method uses the electric fields in between the drift tubes (i.e., gaps) to provide subsequent transverse and longitudinal focusing to the beam along multiple gaps. The beam focusing properties within each gap are adjusted individually by means of the synchronous phase. As a result of the alternating phase focusing method, these linacs can operate completely without internal magnetic lenses. The R&D-program for the high brilliance neutron source HBS offered the opportunity to investigate the APF concept further in order to open this advanced concept for high duty-factor, high intensity hadron beam acceleration. Besides, a prototype APF-interdigital H-mode (IH)-cavity has been designed and is going to be build and tested in the next future.
Paper: TUPA194
DOI: reference for this paper: 10.18429/JACoW-IPAC2023-TUPA194
About: Received: 27 Apr 2023 — Revised: 12 May 2023 — Accepted: 19 Jun 2023 — Issue date: 26 Sep 2023