IPAC2021 - Classification: MC3: Novel Particle Sources and Acceleration Techniques / A16 Advanced Concepts

Paper	Title	Page
MOPAB101	Hollow and Flat Electron Beam Generation at FACET-II	376
	A. Halavanau, S.J. Gessner, C.E. Mayes SLAC, Menlo Park, California, USA J.B. Rosenzweig UCLA, Los Angeles, California, USA
	In this proceeding, we investigate hollow and flat electron beam generation at FACET-II facility. We focus on the case of a circular beamlet arrangement, also known as ’necklace’ beams. We study, via numerical simulations, the resulting e-beam dynamics in the FACET-II photoinjector, beam propagation through the high energy section, as well as possible experimental applications of the ’necklace’ beams. Finally, we evaluate the feasibility of high charge flat beam generation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB101
About •	paper received ※ 23 May 2021 paper accepted ※ 27 July 2021 issue date ※ 23 August 2021
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MOPAB153	Laser Microfabrication for Accelerator Applications	535
	S.P. Antipov, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	Laser microfabrication allows high precision ablation of materials at sub-mm scale. When laser pulse length is shorter than about 10 picoseconds the heat affected zone is minimized and ablation occurs without melting. Work-pieces processed in this fashion exhibit less structural damage and are expected to have a higher damage thresholds. In this paper we will review several case studies of laser-microfabricated components for accelerator and x-ray applications. Ablated materials include diamond, quartz, tungsten, copper, YAG:Ce and silicon.
	Poster MOPAB153 [2.781 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB153
About •	paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 29 August 2021
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MOPAB154	Multi-Cell Accelerating Structure Driven by a Lens-Focused Picosecond THz Pulse	537
	S.P. Antipov, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	Recently, gradients on the order of 1 GV/m level have been obtained in a form of a single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). Such high-intensity radiation can be utilized for charged particle acceleration. However, these pulses are short in time (~1ps) and broadband, therefore a new accelerating structure type is required. In this paper, we propose a novel structure based on focusing of THz radiation in accelerating cell and stacking such cells to achieve a long-range interaction required for an efficient acceleration process. We present an example in which a 100 microJoule THz pulse produces a 600 keV energy gain in 5 mm long 10 cell accelerating structure for an ultra-relativistic electron. This design can be readily extended to non-relativistic particles. Such structure had been laser microfabricated and appropriate dimensions were achieved.
	Poster MOPAB154 [1.283 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB154
About •	paper received ※ 27 May 2021 paper accepted ※ 05 July 2021 issue date ※ 14 August 2021
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MOPAB162	The First Trial of XY-Coupled Beam Phase Space Matching for Three-Dimensional Spiral Injection	553
	M.A. Rehman, K. Furukawa, H. Hisamatsu, T. Mibe, H. Nakayama, S. Ohsawa, N. Saito, K. Sasaki KEK, Ibaraki, Japan H. Hirayama, H. Iinuma, K. Oda Ibaraki University, Ibaraki, Japan R. Matsushita The University of Tokyo, Graduate School of Science, Tokyo, Japan N. Saito J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	Funding: Work supported by "Grant in Aid" for Scientific Research, JSPS (KAKENHI# 26287055, KAKENHI#19H00673) The most recent measurement of muon g-2 results in a 3.8σ discrepancy with the equally precise theoretical prediction. The J-PARC muon g-2/EDM experiment (E34) is in preparation to decipher this discrepancy and unravel the new physics beyond the standard model. The precision goal for g-2 is 0.1 ppm. To achieve this precision goal a novel 3-D spiral injection scheme has been devised to inject and store the beam into a small diameter MRI-type storage magnet for E34. The new injection scheme features smooth injection with high storage efficiency for the compact magnet. However, the spiral injection scheme is an unproven idea, therefore, a Spiral Injection Test Experiment (SITE) at KEK Tsukuba Campus is underway to establish this injection scheme. Due to the axial symmetric field of the solenoid magnet, a strongly XY-coupled beam is required. To produce the required phase space for the solenoid-type storage magnet, a beam transport line consisting of three rotatable quadrupole magnets has been designed and built for SITE. The vertical beam size reduction by means of phase space matching and other geometrical information has been successfully measured by the wire scanners.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB162
About •	paper received ※ 20 May 2021 paper accepted ※ 28 May 2021 issue date ※ 01 September 2021
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MOPAB164	Miniature, High Strength Transport Line Design for Laser Plasma Accelerator-Driven FELs	561
	S. Fatehi, A. Bernhard, A.-S. Müller, M.S. Ning KIT, Karlsruhe, Germany
	Funding: This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research). Laser-plasma acceleration is an outstanding candidate to drive the next-generation compact light sources and FELs. To compensate large chromatic effects using novel compact beam optic elements in the beam transport line is required. We aim at designing miniature, high strength, normal conducting and superconducting transport line magnets and optics for capturing and matching LPA-generated electron bunches to given applications. Our primary application case is a demonstration experiment for transverse gradient undulator (TGU) FELs, to be performed at the JETI laser facility, Jena, Germany. In this contribution, we present the current design of the beam transport line magnets and the beam optics calculations. Laser Plasma Accelerators, FELs, Magnets, Beam Dynamics, Superconductivity, transverse gradient undulator
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB164
About •	paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 20 August 2021
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MOPAB165	Identical Focusing of Train of Relativistic Positron Gaussian Bunches in Plasma	565
	D.S. Bondar KhNU, Kharkov, Ukraine V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: The study is supported by the National Research Fundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299). Focusing of both electron and positron bunches in an electron-positron collider is necessary. The focusing mechanism in the plasma, in which all electron bunches are focused identically, has been proposed earlier. This mechanism is considered for positron bunches by using simulation with LCODE. Three types of lenses with different trains of cosine profile positron bunches are considered depending on the bunch length, the distance between bunches, and their charge. It has been shown that all positron bunches are focused identically at special parameters of the first positron bunch, wherein the middle of bunches are focused weaker than their fronts. V. I. Maslov et al. PAST. 3(2012) 159. ** K. V. Lotov, Phys. Plas. 5 (1998) 785.
	Poster MOPAB165 [2.272 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB165
About •	paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 17 August 2021
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MOPAB169	Generating 510 MW of X-Band Power for Structure-Based Wakefield Acceleration Using a Metamaterial-Based Power Extractor	578
	J.F. Picard, I. Mastovsky, M.A. Shapiro, R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA M.E. Conde, D.S. Doran, J.G. Power, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid TechLabs, Solon, Ohio, USA X. Lu Northern Illinois University, DeKalb, Illinois, USA
	Funding: Research sponsored under Award No. DE-SC0015566 by U.S. Department of Energy, Office of Science, Office of High Energy Physics and Contract No. DE-AC02-06CH11357 by the Office of Science. We present our recent results generating 510 MW of power at 11.7 GHz using a metamaterial-based metallic power-extractor for application in structure-based wakefield acceleration (SWFA). SWFA is a novel acceleration scheme in which high-charge electron bunches are passed through a power extractor structure to produce a high-intensity wakefield. This wakefield can then be used to accelerate a witness bunch in the same beamline or passed to a separate acceleration beamline. MIT’s approach uses a specialized metamaterial for the power extractor design. By using a metamaterial, we can overcome some of the challenges faced by other SWFA techniques. Here, we discuss the Stage 3 experiment. The Stage 1 and Stage 2 experiments successfully demonstrated the functionality of the metamaterial approach by generating high power RF pulses using the 65 MeV electron beam at the Argonne Wakefield Accelerator (AWA) facility. The 510 MW result from Stage 3 experiment is the highest power generated to-date for SWFA at AWA, and was enable by significant design improvements, including an all-copper structure, fully-symmetric coupler design, and breakdown risk-reduction treatment.
	Poster MOPAB169 [8.882 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB169
About •	paper received ※ 08 May 2021 paper accepted ※ 16 July 2021 issue date ※ 25 August 2021
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MOPAB173	Physics Program and Experimental for AWAKE Run 2	586
	P. Muggli MPI, Muenchen, Germany
	Run 1 experimental results demonstrate many characteristics of the self-modulation (SM) in plasma of a long, 400GeV SPS proton bunch. Externally injected, 19MeV electrons were accelerated to 2GeV. Based on these results, we are assembling a physics and experiment program aiming at producing a multi-GeV electron bunch with emittance and energy spread sufficiently low for possible early applications to high-energy physics experiments. Plans include two plasmas, the first for SM, the second for acceleration, and of scalable length, separated by an injection region. The first plasma includes a density step to maintain large-amplitude wakefields after saturation of the SM process. Seeding of the SM process may be obtained from an electron bunch. The 150MeV witness electron bunch from an S-band gun, X-band linac has parameters that produce plasma electron blow out and loading of the wakefields in order to minimize final energy spread and emittance*. We are studying the possibility of using a helicon plasma source for the accelerator, a source that can in principle be very long (100s of m). AWAKE, PRL 122, 054802 (2019), Turner, PRL 122, 054801 (2019), Turner, PRAB 23, 081302, (2020), Braunmueller PRL 125, 264801 (2020) AWAKE, Nature 561, 363 (2018) *Olsen, PRAB 21, 011301 (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB173
About •	paper received ※ 18 May 2021 paper accepted ※ 28 May 2021 issue date ※ 02 September 2021
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TUXB05	Intense Channeling Radiation as a Tool for a Hybrid Crystal-Based Positron Source for Future Colliders
	L. Bandiera, A. Mazzolari, M. Romagnoni, A.I. Sytov INFN-Ferrara, Ferrara, Italy L. Bomben, V. Mascagna INFN MIB, MILANO, Italy G. Cavoto INFN-Roma, Roma, Italy I. Chaikovska, R. Chehab Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France D. De Salvador Univ. degli Studi di Padova, Padova, Italy L.G. Foggetta INFN/LNF, Frascati, Italy E. Lutsenko, M. Prest Università dell’Insubria & INFN Milano Bicocca, Como, Italy M. Soldani Università degli Studi di Ferrara, Ferrara, Italy V.V. Tikhomirov INP BSU, Minsk, Belarus E. Vallazza INFN-Trieste, Trieste, Italy
	There is a strong need for intense positron sources for future colliders. A crystal-based hybrid positron source could be an alternative to conventional sources based on the e^- conversion into e⁺ in a thick target. The basic idea of the hybrid source is to split the e⁺ converter into a gamma-quanta radiator plus a gamma-to-positron converter. In such a scheme an e^- beam crosses a thin axially oriented crystal with emission of "channeling radiation", characterized by a considerably larger amount of photons w.r.t. standard bremsstrahlung. The net result is an increase in the number of e⁺ produced at the converter target. In the hybrid scheme, only photons reach the converter, thereby reducing the Peak Energy Deposition Density (PEDD) in the target. Here we present the results of a test conducted at the DESY TB with 5.6 GeV e^- interacting with a W crystal. A huge enhancement in the radiated energy and in the photon emission has been recorded and reproduced with Monte Carlo simulations*. This study is relevant for the design of the FCC-ee positron source. Indeed, through Monte Carlo, we also investigated the best parameters of the crystal radiator suited for the FCC-ee e⁺ source. R. Chehab et al. PAC’89,10.1109/PAC.1989.73147 X.Artru et al. NIMB 266 (2008) 3868 * A. Sytov, V. Tikhomirov, L. Bandiera PRAB 22 (2019) 064601
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THPAB051	Vertical Septum Magnet Design for the APS Upgrade	3862
	M. Abliz, M. Borland, H. Cease, G. Decker, A.K. Jain, M.S. Jaski, M. Kasa, J.S. Kerby, U. Wienands, A. Xiao ANL, Lemont, Illinois, USA J.W. Amann SLAC, Menlo Park, California, USA D.J. Harding Fermilab, Batavia, Illinois, USA
	The vertical injection scheme proposed for the APS Upgrade (APS-U) Project requires a challenging septum magnet that must meet stringent beam physics, magnetic field leakage, and vacuum requirements. The current iteration of this magnet design includes an enlarged stored-beam chamber aperture of 9 mm x 12 mm and a reduction of the septum thickness to 1.5 mm. The enlarged aperture accommodates a non-evaporable getter (NEG)-coated stored beam chamber to better achieve the required vacuum. A prototype septum magnet has been built and measurements confirm the cancellation of a peak leakage field even though the value is six times larger than the design. The leakage field measured at the upstream (US) end cancels the downstream (DS) end as was expected by design. The measured and simulated leakage field and the stored beam trajectories are reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB051
About •	paper received ※ 14 May 2021 paper accepted ※ 01 September 2021 issue date ※ 27 August 2021
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THPAB062	Long-Wave IR Terawatt Laser Pulse Compression to Sub-Picoseconds	3893
	I. Pogorelsky, M. Babzien, M.A. Palmer, M.N. Polyanskiy BNL, Upton, New York, USA
	Funding: U.S. Department of Energy under contract DE-SC0012704 We report an experiment and simulations on post-compression of 2 ps, 0.15 TW CO₂ laser pulses to 480 fs, ~0.25 TW by means of a self-phase modulation accompanied by a negative group dispersion in KCl and BaF2 optical slabs. In addition, down to 130 fs fine pulse structure, but at lower conversion efficiency, has been observed through self-compression in a bulk NaCl crystal. The obtained results surpass by far previous achievements in the ultra-fast long-wave IR laser technology
	Poster THPAB062 [2.675 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB062
About •	paper received ※ 12 May 2021 paper accepted ※ 18 June 2021 issue date ※ 24 August 2021
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THPAB071	Physics Goals of DWA Experiments at FACET-II	3922
	J.B. Rosenzweig, H.S. Ancelin, G. Andonian, A. Fukasawa, C.E. Hansel, G.E. Lawler, W.J. Lynn, N. Majernik, J.I. Mann, P. Manwani, Y. Sakai, O. Williams, M. Yadav UCLA, Los Angeles, California, USA S.V. Baryshev Michigan State University, East Lansing, Michigan, USA S. Baturin Northern Illinois University, DeKalb, Illinois, USA M.J. Hogan, B.D. O’Shea, D.W. Storey, V. Yakimenko SLAC, Menlo Park, California, USA
	Funding: This work supported by DOE HEP Grant DE-SC0009914, The dielectric wakefield acceleration (DWA) program at FACET produced a multitude of new physics results that range from GeV/m acceleration to the discovery of high field-induced conductivity in THz waves, and beyond, to a demonstration of positron-driven wakes. Here we review the rich program now developing in the DWA experiments at FACET-II. With increases in beam quality, a key feature of this program is extended interaction lengths, near 0.5 m, permitting GeV-class acceleration. Detailed physics studies in this context include beam breakup and its control through the exploitation of DWA structure symmetry. The next step in understanding DWA limits requires the exploration of new materials with low loss tangent, large bandgap, and improved thermal characteristics. Advanced structures with photonic features for mode confinement and exclusion of the field from the dielectric, as well as quasi-optical handling of coherent Cerenkov signals is discussed. Use of DWA for laser-based injection and advanced temporal diagnostics is examined.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB071
About •	paper received ※ 25 May 2021 paper accepted ※ 28 July 2021 issue date ※ 22 August 2021
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THPAB130	Design of a Very Low Energy Beamline for NA61/SHINE	4017
	C.A. Mussolini, N. Charitonidis CERN, Geneva, Switzerland P. Burrows JAI, Oxford, United Kingdom P. Burrows Oxford University, Physics Department, Oxford, Oxon, United Kingdom Y. Nagai Colorado University at Boulder, Boulder, Colorado, USA Y. Nagai ELTE, Budapest, Hungary E.D. Zimmerman CIPS, Boulder, Colorado, USA
	A new, low-energy beamline branch is currently under consideration for the H₂ beamline at the CERN North Area. This new branch would extend the capabilities of the current infrastructure enabling the study of particles in the very low, 1-13 GeV/c, momentum range. The design of this new beamline involves various stages. Firstly, a study of the secondary targets to maximise the yield of secondary hadrons. Secondly, the development of high acceptance transverse optics with high momentum resolution on the order of a few %. Finally, we discuss the first considerations on instrumentation to enable particle identification and background rejection. The first experiment to profit from this new line could be NA61/SHINE, but other possible future fixed target experiments or test-beams installed in the downstream zones could also use the low-energy particles provided. The aim is to arrive at a complete design of this branch by the end of 2021, which, pending the approval of the CERN scientific committees, could be envisaged for construction after 2024. This timescale is compatible with requests for measurements by various large international collaborations, in the next 10-year horizon.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB130
About •	paper received ※ 15 May 2021 paper accepted ※ 27 July 2021 issue date ※ 27 August 2021
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THPAB131	Spatio-Temporal Measurements of THz Pulses	4021
	G.A. Hine ORNL, Oak Ridge, Tennessee, USA
	Funding: This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory under Contract No. DEAC05-00OR22725. The 3D characterization of single-cycle Terahertz (THz) pulses in its transverse and temporal dimensions is presented. The high fields and short wavelengths of THz pulses make them an intriguing prospect for novel accelerator technologies. Effective application for free-space THz pulses requires high beam quality and concomitant measuring techniques. The combination of conventional electro-optic sampling to measure the temporal profile and detectors like microbolometer focal plane arrays to measure the transverse profile does not capture the correlations that can arise in single-cycle THz pulses. To capture these correlations, a modified version electro-optic sampling using a CCD is implemented. THz pulses generated by optical rectification in organic crystals are measured using this technique and their spatiotemporal correlations characterized.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB131
About •	paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 17 August 2021
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Paper

Title

Page

Hollow and Flat Electron Beam Generation at FACET-II

376

A. Halavanau, S.J. Gessner, C.E. Mayes
SLAC, Menlo Park, California, USA
J.B. Rosenzweig
UCLA, Los Angeles, California, USA

In this proceeding, we investigate hollow and flat electron beam generation at FACET-II facility. We focus on the case of a circular beamlet arrangement, also known as ’necklace’ beams. We study, via numerical simulations, the resulting e-beam dynamics in the FACET-II photoinjector, beam propagation through the high energy section, as well as possible experimental applications of the ’necklace’ beams. Finally, we evaluate the feasibility of high charge flat beam generation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB101

About •

paper received ※ 23 May 2021 paper accepted ※ 27 July 2021 issue date ※ 23 August 2021

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MOPAB153

Laser Microfabrication for Accelerator Applications

535

S.P. Antipov, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

Laser microfabrication allows high precision ablation of materials at sub-mm scale. When laser pulse length is shorter than about 10 picoseconds the heat affected zone is minimized and ablation occurs without melting. Work-pieces processed in this fashion exhibit less structural damage and are expected to have a higher damage thresholds. In this paper we will review several case studies of laser-microfabricated components for accelerator and x-ray applications. Ablated materials include diamond, quartz, tungsten, copper, YAG:Ce and silicon.

Poster MOPAB153 [2.781 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB153

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paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 29 August 2021

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MOPAB154

Multi-Cell Accelerating Structure Driven by a Lens-Focused Picosecond THz Pulse

537

S.P. Antipov, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

Recently, gradients on the order of 1 GV/m level have been obtained in a form of a single cycle (~1 ps) THz pulses produced by conversion of a high peak power laser radiation in nonlinear crystals (~1 mJ, 1 ps, up to 3% conversion efficiency). Such high-intensity radiation can be utilized for charged particle acceleration. However, these pulses are short in time (~1ps) and broadband, therefore a new accelerating structure type is required. In this paper, we propose a novel structure based on focusing of THz radiation in accelerating cell and stacking such cells to achieve a long-range interaction required for an efficient acceleration process. We present an example in which a 100 microJoule THz pulse produces a 600 keV energy gain in 5 mm long 10 cell accelerating structure for an ultra-relativistic electron. This design can be readily extended to non-relativistic particles. Such structure had been laser microfabricated and appropriate dimensions were achieved.

Poster MOPAB154 [1.283 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB154

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paper received ※ 27 May 2021 paper accepted ※ 05 July 2021 issue date ※ 14 August 2021

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MOPAB162

The First Trial of XY-Coupled Beam Phase Space Matching for Three-Dimensional Spiral Injection

553

M.A. Rehman, K. Furukawa, H. Hisamatsu, T. Mibe, H. Nakayama, S. Ohsawa, N. Saito, K. Sasaki
KEK, Ibaraki, Japan
H. Hirayama, H. Iinuma, K. Oda
Ibaraki University, Ibaraki, Japan
R. Matsushita
The University of Tokyo, Graduate School of Science, Tokyo, Japan
N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

Funding: Work supported by "Grant in Aid" for Scientific Research, JSPS (KAKENHI# 26287055, KAKENHI#19H00673)
The most recent measurement of muon g-2 results in a 3.8σ discrepancy with the equally precise theoretical prediction. The J-PARC muon g-2/EDM experiment (E34) is in preparation to decipher this discrepancy and unravel the new physics beyond the standard model. The precision goal for g-2 is 0.1 ppm. To achieve this precision goal a novel 3-D spiral injection scheme has been devised to inject and store the beam into a small diameter MRI-type storage magnet for E34. The new injection scheme features smooth injection with high storage efficiency for the compact magnet. However, the spiral injection scheme is an unproven idea, therefore, a Spiral Injection Test Experiment (SITE) at KEK Tsukuba Campus is underway to establish this injection scheme. Due to the axial symmetric field of the solenoid magnet, a strongly XY-coupled beam is required. To produce the required phase space for the solenoid-type storage magnet, a beam transport line consisting of three rotatable quadrupole magnets has been designed and built for SITE. The vertical beam size reduction by means of phase space matching and other geometrical information has been successfully measured by the wire scanners.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB162

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paper received ※ 20 May 2021 paper accepted ※ 28 May 2021 issue date ※ 01 September 2021

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MOPAB164

Miniature, High Strength Transport Line Design for Laser Plasma Accelerator-Driven FELs

561

S. Fatehi, A. Bernhard, A.-S. Müller, M.S. Ning
KIT, Karlsruhe, Germany

Funding: This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research).
Laser-plasma acceleration is an outstanding candidate to drive the next-generation compact light sources and FELs. To compensate large chromatic effects using novel compact beam optic elements in the beam transport line is required. We aim at designing miniature, high strength, normal conducting and superconducting transport line magnets and optics for capturing and matching LPA-generated electron bunches to given applications. Our primary application case is a demonstration experiment for transverse gradient undulator (TGU) FELs, to be performed at the JETI laser facility, Jena, Germany. In this contribution, we present the current design of the beam transport line magnets and the beam optics calculations.
Laser Plasma Accelerators, FELs, Magnets, Beam Dynamics, Superconductivity, transverse gradient undulator

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB164

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paper received ※ 19 May 2021 paper accepted ※ 25 May 2021 issue date ※ 20 August 2021

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MOPAB165

Identical Focusing of Train of Relativistic Positron Gaussian Bunches in Plasma

565

D.S. Bondar
KhNU, Kharkov, Ukraine
V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: The study is supported by the National Research Fundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299).
Focusing of both electron and positron bunches in an electron-positron collider is necessary. The focusing mechanism in the plasma, in which all electron bunches are focused identically, has been proposed earlier*. This mechanism is considered for positron bunches by using simulation with LCODE**. Three types of lenses with different trains of cosine profile positron bunches are considered depending on the bunch length, the distance between bunches, and their charge. It has been shown that all positron bunches are focused identically at special parameters of the first positron bunch, wherein the middle of bunches are focused weaker than their fronts.
* V. I. Maslov et al. PAST. 3(2012) 159.
** K. V. Lotov, Phys. Plas. 5 (1998) 785.

Poster MOPAB165 [2.272 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB165

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paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 17 August 2021

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MOPAB169

Generating 510 MW of X-Band Power for Structure-Based Wakefield Acceleration Using a Metamaterial-Based Power Extractor

578

J.F. Picard, I. Mastovsky, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA
M.E. Conde, D.S. Doran, J.G. Power, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid TechLabs, Solon, Ohio, USA
X. Lu
Northern Illinois University, DeKalb, Illinois, USA

Funding: Research sponsored under Award No. DE-SC0015566 by U.S. Department of Energy, Office of Science, Office of High Energy Physics and Contract No. DE-AC02-06CH11357 by the Office of Science.
We present our recent results generating 510 MW of power at 11.7 GHz using a metamaterial-based metallic power-extractor for application in structure-based wakefield acceleration (SWFA). SWFA is a novel acceleration scheme in which high-charge electron bunches are passed through a power extractor structure to produce a high-intensity wakefield. This wakefield can then be used to accelerate a witness bunch in the same beamline or passed to a separate acceleration beamline. MIT’s approach uses a specialized metamaterial for the power extractor design. By using a metamaterial, we can overcome some of the challenges faced by other SWFA techniques. Here, we discuss the Stage 3 experiment. The Stage 1 and Stage 2 experiments successfully demonstrated the functionality of the metamaterial approach by generating high power RF pulses using the 65 MeV electron beam at the Argonne Wakefield Accelerator (AWA) facility. The 510 MW result from Stage 3 experiment is the highest power generated to-date for SWFA at AWA, and was enable by significant design improvements, including an all-copper structure, fully-symmetric coupler design, and breakdown risk-reduction treatment.

Poster MOPAB169 [8.882 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB169

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paper received ※ 08 May 2021 paper accepted ※ 16 July 2021 issue date ※ 25 August 2021

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MOPAB173

Physics Program and Experimental for AWAKE Run 2

586

P. Muggli
MPI, Muenchen, Germany

Run 1 experimental results demonstrate many characteristics of the self-modulation (SM) in plasma of a long, 400GeV SPS proton bunch*. Externally injected, 19MeV electrons were accelerated to 2GeV**. Based on these results, we are assembling a physics and experiment program aiming at producing a multi-GeV electron bunch with emittance and energy spread sufficiently low for possible early applications to high-energy physics experiments. Plans include two plasmas, the first for SM, the second for acceleration, and of scalable length, separated by an injection region. The first plasma includes a density step to maintain large-amplitude wakefields after saturation of the SM process. Seeding of the SM process may be obtained from an electron bunch. The 150MeV witness electron bunch from an S-band gun, X-band linac has parameters that produce plasma electron blow out and loading of the wakefields in order to minimize final energy spread and emittance***. We are studying the possibility of using a helicon plasma source for the accelerator, a source that can in principle be very long (100s of m).
*AWAKE, PRL 122, 054802 (2019), Turner, PRL 122, 054801 (2019), Turner, PRAB 23, 081302, (2020), Braunmueller PRL 125, 264801 (2020)
**AWAKE, Nature 561, 363 (2018)
***Olsen, PRAB 21, 011301 (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB173

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paper received ※ 18 May 2021 paper accepted ※ 28 May 2021 issue date ※ 02 September 2021

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TUXB05

Intense Channeling Radiation as a Tool for a Hybrid Crystal-Based Positron Source for Future Colliders

L. Bandiera, A. Mazzolari, M. Romagnoni, A.I. Sytov
INFN-Ferrara, Ferrara, Italy
L. Bomben, V. Mascagna
INFN MIB, MILANO, Italy
G. Cavoto
INFN-Roma, Roma, Italy
I. Chaikovska, R. Chehab
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
D. De Salvador
Univ. degli Studi di Padova, Padova, Italy
L.G. Foggetta
INFN/LNF, Frascati, Italy
E. Lutsenko, M. Prest
Università dell’Insubria & INFN Milano Bicocca, Como, Italy
M. Soldani
Università degli Studi di Ferrara, Ferrara, Italy
V.V. Tikhomirov
INP BSU, Minsk, Belarus
E. Vallazza
INFN-Trieste, Trieste, Italy

There is a strong need for intense positron sources for future colliders. A crystal-based hybrid positron source could be an alternative to conventional sources based on the e^- conversion into e⁺ in a thick target. The basic idea of the hybrid source is to split the e⁺ converter into a gamma-quanta radiator plus a gamma-to-positron converter*. In such a scheme an e^- beam crosses a thin axially oriented crystal with emission of "channeling radiation", characterized by a considerably larger amount of photons w.r.t. standard bremsstrahlung**. The net result is an increase in the number of e⁺ produced at the converter target. In the hybrid scheme, only photons reach the converter, thereby reducing the Peak Energy Deposition Density (PEDD) in the target. Here we present the results of a test conducted at the DESY TB with 5.6 GeV e^- interacting with a W crystal. A huge enhancement in the radiated energy and in the photon emission has been recorded and reproduced with Monte Carlo simulations***. This study is relevant for the design of the FCC-ee positron source. Indeed, through Monte Carlo, we also investigated the best parameters of the crystal radiator suited for the FCC-ee e⁺ source.
* R. Chehab et al. PAC’89,10.1109/PAC.1989.73147
** X.Artru et al. NIMB 266 (2008) 3868
*** A. Sytov, V. Tikhomirov, L. Bandiera PRAB 22 (2019) 064601

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THPAB051

Vertical Septum Magnet Design for the APS Upgrade

3862

M. Abliz, M. Borland, H. Cease, G. Decker, A.K. Jain, M.S. Jaski, M. Kasa, J.S. Kerby, U. Wienands, A. Xiao
ANL, Lemont, Illinois, USA
J.W. Amann
SLAC, Menlo Park, California, USA
D.J. Harding
Fermilab, Batavia, Illinois, USA

The vertical injection scheme proposed for the APS Upgrade (APS-U) Project requires a challenging septum magnet that must meet stringent beam physics, magnetic field leakage, and vacuum requirements. The current iteration of this magnet design includes an enlarged stored-beam chamber aperture of 9 mm x 12 mm and a reduction of the septum thickness to 1.5 mm. The enlarged aperture accommodates a non-evaporable getter (NEG)-coated stored beam chamber to better achieve the required vacuum. A prototype septum magnet has been built and measurements confirm the cancellation of a peak leakage field even though the value is six times larger than the design. The leakage field measured at the upstream (US) end cancels the downstream (DS) end as was expected by design. The measured and simulated leakage field and the stored beam trajectories are reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB051

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paper received ※ 14 May 2021 paper accepted ※ 01 September 2021 issue date ※ 27 August 2021

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THPAB062

Long-Wave IR Terawatt Laser Pulse Compression to Sub-Picoseconds

3893

I. Pogorelsky, M. Babzien, M.A. Palmer, M.N. Polyanskiy
BNL, Upton, New York, USA

Funding: U.S. Department of Energy under contract DE-SC0012704
We report an experiment and simulations on post-compression of 2 ps, 0.15 TW CO₂ laser pulses to 480 fs, ~0.25 TW by means of a self-phase modulation accompanied by a negative group dispersion in KCl and BaF2 optical slabs. In addition, down to 130 fs fine pulse structure, but at lower conversion efficiency, has been observed through self-compression in a bulk NaCl crystal. The obtained results surpass by far previous achievements in the ultra-fast long-wave IR laser technology

Poster THPAB062 [2.675 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB062

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paper received ※ 12 May 2021 paper accepted ※ 18 June 2021 issue date ※ 24 August 2021

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THPAB071

Physics Goals of DWA Experiments at FACET-II

3922

J.B. Rosenzweig, H.S. Ancelin, G. Andonian, A. Fukasawa, C.E. Hansel, G.E. Lawler, W.J. Lynn, N. Majernik, J.I. Mann, P. Manwani, Y. Sakai, O. Williams, M. Yadav
UCLA, Los Angeles, California, USA
S.V. Baryshev
Michigan State University, East Lansing, Michigan, USA
S. Baturin
Northern Illinois University, DeKalb, Illinois, USA
M.J. Hogan, B.D. O’Shea, D.W. Storey, V. Yakimenko
SLAC, Menlo Park, California, USA

Funding: This work supported by DOE HEP Grant DE-SC0009914,
The dielectric wakefield acceleration (DWA) program at FACET produced a multitude of new physics results that range from GeV/m acceleration to the discovery of high field-induced conductivity in THz waves, and beyond, to a demonstration of positron-driven wakes. Here we review the rich program now developing in the DWA experiments at FACET-II. With increases in beam quality, a key feature of this program is extended interaction lengths, near 0.5 m, permitting GeV-class acceleration. Detailed physics studies in this context include beam breakup and its control through the exploitation of DWA structure symmetry. The next step in understanding DWA limits requires the exploration of new materials with low loss tangent, large bandgap, and improved thermal characteristics. Advanced structures with photonic features for mode confinement and exclusion of the field from the dielectric, as well as quasi-optical handling of coherent Cerenkov signals is discussed. Use of DWA for laser-based injection and advanced temporal diagnostics is examined.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB071

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paper received ※ 25 May 2021 paper accepted ※ 28 July 2021 issue date ※ 22 August 2021

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THPAB130

Design of a Very Low Energy Beamline for NA61/SHINE

4017

C.A. Mussolini, N. Charitonidis
CERN, Geneva, Switzerland
P. Burrows
JAI, Oxford, United Kingdom
P. Burrows
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
Y. Nagai
Colorado University at Boulder, Boulder, Colorado, USA
Y. Nagai
ELTE, Budapest, Hungary
E.D. Zimmerman
CIPS, Boulder, Colorado, USA

A new, low-energy beamline branch is currently under consideration for the H₂ beamline at the CERN North Area. This new branch would extend the capabilities of the current infrastructure enabling the study of particles in the very low, 1-13 GeV/c, momentum range. The design of this new beamline involves various stages. Firstly, a study of the secondary targets to maximise the yield of secondary hadrons. Secondly, the development of high acceptance transverse optics with high momentum resolution on the order of a few %. Finally, we discuss the first considerations on instrumentation to enable particle identification and background rejection. The first experiment to profit from this new line could be NA61/SHINE, but other possible future fixed target experiments or test-beams installed in the downstream zones could also use the low-energy particles provided. The aim is to arrive at a complete design of this branch by the end of 2021, which, pending the approval of the CERN scientific committees, could be envisaged for construction after 2024. This timescale is compatible with requests for measurements by various large international collaborations, in the next 10-year horizon.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB130

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paper received ※ 15 May 2021 paper accepted ※ 27 July 2021 issue date ※ 27 August 2021

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THPAB131

Spatio-Temporal Measurements of THz Pulses

4021

G.A. Hine
ORNL, Oak Ridge, Tennessee, USA

Funding: This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory under Contract No. DEAC05-00OR22725.
The 3D characterization of single-cycle Terahertz (THz) pulses in its transverse and temporal dimensions is presented. The high fields and short wavelengths of THz pulses make them an intriguing prospect for novel accelerator technologies. Effective application for free-space THz pulses requires high beam quality and concomitant measuring techniques. The combination of conventional electro-optic sampling to measure the temporal profile and detectors like microbolometer focal plane arrays to measure the transverse profile does not capture the correlations that can arise in single-cycle THz pulses. To capture these correlations, a modified version electro-optic sampling using a CCD is implemented. THz pulses generated by optical rectification in organic crystals are measured using this technique and their spatiotemporal correlations characterized.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB131

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paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 17 August 2021

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