IPAC2022 - List of Keywords (ECR)

Paper	Title	Other Keywords	Page
MOPOPT004	Development of a New Clusterization Method for the GEM-TPC Detector	detector, electron, experiment, electronics	233
	M. Luoma, F. Garcia, A. Jokinen, R. Turpeinen, J. Äystö HIP, University of Helsinki, Finland T. Blatz, H. Flemming, K. Götzen, C. Karagiannis, N. Kurz, S. Löchner, C. Nociforo, C.J. Schmidt, H. Simon, B. Voss, P. Wieczorek, M. Winkler GSI, Darmstadt, Germany D. Chokheli Georgian Technical University, Tbilisi, Georgia T. Grahn, S. Rinta-Antila JYFL, Jyväskylä, Finland
	The Facility for Antiproton and Ion Research FAIR, in Darmstadt Germany, will be one of the largest accelerator laboratories worldwide. The Superconducting FRagment Separator (Super-FRS)* is one of its main components. The Super-FRS can produce, separate and deliver high-energy radioactive beams with intensities up to 1e11 ions/s, covering projectiles from protons up to uranium and it can be used as an independent experimental device. The Gas Electron Multiplier-based Time Projection Chambers (GEM-TPC) in twin configuration is a newly developed beam tracking detector capable of providing spatial resolution of less than 1 mm with a tracking efficiency close to 100% at 1 MHz counting rate. The GEM-TPC (HGB4) was tested at the FRagment Separator (FRS), with 238U beam at 850 MeV/u. A new clusterization method was developed, for the first time and used for an analysis. This method allowed to access to waveforms of each strip signal within a single trigger in an event-by-event basis. The procedures involved in this method will be shown in details. * H.Geissel et al., The Super-FRS project at GSI, Nucl. Instr. and Meth. in Phys., vol. B204, pp. 71-85, 2003.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOPT004
About •	Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 23 June 2022
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MOPOTK009	Basic Design Choices for the BESSY III MBA Lattice	emittance, lattice, dipole, sextupole	449
	B.C. Kuske, M. Abo-Bakr, P. Goslawski HZB, Berlin, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association. Lattice development efforts for the 2.5GeV, low emittance successor of BESSY II, are ongoing at HZB for 2 years. The basic choice of a multi-bend achromat lattice is indispensable due to the emittance goal of 100pm, required to generate diffraction limited radiation up to 1keV. Hard boundary conditions for the design are a reasonably short circumference of ~350m due to the accessible construction properties in vicinity to Bessy II and 16 super-periods to not step behind the number of existing experimental stations. Additionally, the Pysikalisch Technische Bundesanstalt, the long-term partner of HZB, requests homogeneous dipoles as a calculable and traceable source of radiation for metrology applications. The configuration of the two building blocks of MBA lattices - unit cell and dispersion suppression cell - has been thoroughly studied from basic principles. It was found that gradient free bending dipoles are the better choice for the BESSY III lattice, opposite to the concepts of comparable projects. This work summarizes and explains the findings of our investigations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOTK009
About •	Received ※ 21 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 11 June 2022 — Issue date ※ 13 June 2022
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MOPOTK027	Characterization of Various GaN Samples for Photoinjectors	cathode, electron, polarization, brightness	500
	M.B. Andorf, I.V. Bazarov, S.J. Levenson, J.M. Maxson Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA J. Encomendero, D. Jena, V.V. Protasenko, H.G. Xing Cornell University, Ithaca, New York, USA
	Funding: DOE-HEP DESC0021002 DOE-NP DE-SC0021425 Photoemission properties (quantum efficiency, spectral response, and lifetime) of various GaN based photocathodes are summarized, including p-doped samples in its hexagonal phase, cubic GaN and a more exotic 2-D hole gas sample. The 2-D hole contains no dopant impurity but achieves high conductivity via polarization fields produced at the heterojunction of GaN and AlN. For efficient electron production, cesium is used to achieve Negative Electron Affinity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOTK027
About •	Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 26 June 2022
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TUOXSP1	Origin and Mitigation of the Beam-Induced Surface Modifications of the LHC Beam Screens	electron, radiation, cryogenics, MMI	780
	V. Petit, P. Chiggiato, M. Himmerlich, S. Marinoni, H. Neupert, M. Taborelli, L.J. Tavian CERN, Meyrin, Switzerland
	All over Run 2, the LHC beam-induced heat load on the cryogenic system exhibited a wide scattering along the ring. Studies ascribed the heat source to electron cloud build-up, indicating an unexpected high Secondary Electron Yield (SEY) of the beam screen surface in some LHC regions. The inner copper surface of high and low heat load beam screens, extracted during the Long Shutdown 2, was analysed. On the low heat load ones, the surface was covered with the native Cu2O oxide, while on the high heat load ones CuO dominated at surface, and it exhibited a very low carbon coverage. Such chemical modifications increase the SEY and inhibit a proper conditioning of the affected surfaces. Following this characterisation, the mechanisms for CuO build-up in the LHC beam pipe were investigated on a newly commissioned cryogenic system allowing electron irradiation, surface chemical characterisation by X-ray Photoelectron Spectroscopy and SEY measurements on samples held below 15 K. In parallel, curative solutions against the presence of CuO in the LHC beam screens were explored, which could be implemented in-situ to recover a proper conditioning and lower the beam-induced heat load.
	Slides TUOXSP1 [2.669 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUOXSP1
About •	Received ※ 17 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 05 July 2022
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TUPOST043	A Novel Method for Detecting Unidentified Falling Object Loss Patterns in the LHC	operation, network, Windows, machine-protect	953
	L. Coyle, F. Blanc, D. Di Croce, T. Pieloni EPFL, Lausanne, Switzerland L. Coyle, A. Lechner, D. Mirarchi, M. Solfaroli Camillocci, J. Wenninger CERN, Meyrin, Switzerland
	Understanding and mitigating particle losses in the Large Hadron Collider (LHC) is essential for both machine safety and efficient operation. Abnormal loss distributions are telltale signs of abnormal beam behaviour or incorrect machine configuration. By leveraging the advancements made in the field of Machine Learning, a novel data-driven method of detecting anomalous loss distributions during machine operation has been developed. A neural network anomaly detection model was trained to detect Unidentified Falling Object events using stable beam, Beam Loss Monitor (BLM) data acquired during the operation of the LHC. Data-driven models, such as the one presented, could lead to significant improvements in the autonomous labelling of abnormal loss distributions, ultimately bolstering the ever ongoing effort toward improving the understanding and mitigation of these events.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST043
About •	Received ※ 19 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 21 June 2022
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TUPOPT039	Characterization of Diamond with Buried Boron-Doped Layer Developed for Q-Switching an X-Ray Optical Cavity	cavity, FEL, laser, lattice	1097
	R.A. Margraf, A. Halavanau, Z. Huang, J. Krzywiński, J.P. MacArthur, G. Marcus, M.L. Ng, A.R. Robert, R. Robles, T. Sato, D. Zhu SLAC, Menlo Park, California, USA Z. Huang, F. Ke, R. Robles, Y. Zhong Stanford University, Stanford, California, USA S.-K. Mo, Y. Zhong LBNL, Berkeley, California, USA P. Pradhan ANL, Lemont, Illinois, USA A.R. Robert MAX IV Laboratory, Lund University, Lund, Sweden M.D. Ynsa UAM, Madrid, Spain
	Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515. X-ray Free-Electron Laser Oscillators (XFELOs) and X-ray Regenerative Amplifier FELs (XRAFELs) are currently in development to improve longitudinal coherence and spectral brightness of XFELs. These schemes lase an electron beam in an undulator within an optical cavity to produce X-rays. X-rays circulate in the cavity and interact with fresh electron bunches to seed the FEL process over multiple passes, producing progressively brighter and more spectrally pure X-rays. Typically, the optical cavities used are composed of Bragg-reflecting mirrors to provide high reflectivity and spectral filtering. This high reflectivity necessitates special techniques to out-couple X-rays from the cavity to deliver them to users. One method involves "Q-switching" the cavity by actively modifying the reflectivity of one Bragg-reflecting crystal. To control the crystal lattice constant and thus reflectivity, we use an infrared laser to heat a buried boron layer in a diamond crystal. Here, we build on earlier work in Krzywinski et al.* and present the current status of our Q-switching diamond, including implantation with 9 MeV boron ions, annealing, characterization and early tests. *Krzywinski et al., "Q-switching of X-Ray Optical Cavities by using Boron Doped Buried Layer under a Surface of a Diamond Crystal," Proceedings of FEL2019, Hamburg, Germany, TUP033, 2019.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT039
About •	Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 08 July 2022
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TUPOTK009	Development of Superconducting CH Cavity Preparation at IAP	cavity, simulation, coupling, vacuum	1208
	P. Müller, H. Podlech IAP, Frankfurt am Main, Germany K. Aulenbacher, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu HIM, Mainz, Germany W.A. Barth, M. Basten, V. Gettmann, T. Kürzeder, M. Miski-Oglu GSI, Darmstadt, Germany
	Funding: HIC for FAIR, BMBF Contr. No. 05P21RFRB2 and HFHF Goethe University (GU), Gesellschaft für Schwerionenforschung (GSI) and Helmholtz Institut Mainz (HIM) work in collaboration on the Helmholtz Linear Accelerator (HELIAC). A new superconducting (sc) continous wave (cw) high intensity heavy ion linear accelerator (Linac) will provide ion beams with maximum duty factor up to beam energies of 7.3 MeV/u. The acceleration voltage will be provided by sc Crossbar-H-mode (CH) cavities, developed of Institute for Applied Physics (IAP) at GU. Cavity preparation is researched and optimized towards widely used elliptical multicell cavities. A standardized preparation protocol for CH cavities is researched in collaboration between GU, GSI and HIM on a 360 MHz 19 gap CH prototype. Baseline measurements and a 120°C 48 hour bake produced higher maximum gradient, higher intrinsic quality factor and a shorter cavity conditioning phase. As a critical preparation step, High Pressure Rinsing (HPR) with ultra pure water will be performed at HIM and is currently in preparation. HPR cycles are currently tested on a CH dummy with a new nozzle layout that is optimized towards CH cavity geometry.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK009
About •	Received ※ 08 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 18 June 2022 — Issue date ※ 02 July 2022
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TUPOTK011	Commissioning of a New Magnetometric Mapping System for SRF Cavity Performance Tests	cavity, SRF, niobium, superconducting-cavity	1215
	J.C. Wolff, J. Eschke, A. Gössel, D. Reschke, L. Steder, L. Trelle DESY, Hamburg, Germany W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program. Magnetic flux trapped in the niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity for flux trapping is mainly determined by the treatment and the geometry of the cavity as well as the niobium grain size and orientation. To potentially improve the flux expulsion characteristics of SRF cavities and hence the efficiency of future accelerator facilities, further studies of the trapping behavior are essential. For this purpose a magnetometric mapping system to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities has been developed and is currently in the commissioning phase at DESY. Contrary to similar approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs. Furthermore, the signal-to-noise ratio (SNR) and consequently the measuring sensitivity can be enhanced by shorter analog signal lines, less thermal noise and the Mu-metal shielding of the cryostat. In this contribution test results gained by a prototype of the mapping system are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK011
About •	Received ※ 10 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 29 June 2022
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TUPOTK012	Nitrogen Infusion Sample R&D at DESY	cavity, niobium, vacuum, accelerating-gradient	1219
	C. Bate University of Hamburg, Hamburg, Germany A. Ermakov, D. Reschke, J. Schaffran DESY, Hamburg, Germany W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program. Many accelerator projects such as the ILC would benefit from cavities with reduced surface resistance (high Q-values) while maintaining a high accelerating gradient. A possible way to meet the requirements is the so-called nitrogen-infusion procedure on Niobium cavities. However, a fundamental understanding and a theoretical model of this method are still missing. One important parameter is the residual resistance ratio (RRR) which is related to the impurity content of the material. We report the investigated RRR on samples in a wide temperature range in a vacuum and under a nitrogen atmosphere. This comparison made it possible to make statements about the differences in the concentration of nitrogen by varying the temperature. The samples are pure cavity-grade niobium and treated in the same manner as cavities. For this purpose, a small furnace dedicated to sample treatment was set up to change and explore the parameter space of the infusion recipe. Care was taken to achieve the highest level of purity possible in the furnace and in a pressure range of 1.0·10^-8 mbar in order to meet the high requirements of nitrogen infusion.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK012
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 01 July 2022
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TUPOTK034	Evaluating the Effects of Nitrogen Doping and Oxygen Doping on SRF Cavity Performance	cavity, SRF, niobium, simulation	1287
	H. Hu, Y.K. Kim University of Chicago, Chicago, Illinois, USA D. Bafia Fermilab, Batavia, Illinois, USA
	Superconducting radiofrequency (SRF) cavities are resonators with extremely low surface resistance that enable accelerating cavities to have extremely high quality factors (Q₀). High Q₀ decreases the capital required to keep the accelerators cold by reducing power loss. The performance of SRF cavities is largely governed by the surface composition of the first §I{100}{nm} of the cavity surface. Impurities such as oxygen and nitrogen have been observed to yield high Q₀, but their precise roles are still being studied. Here, we compare the performance of cavities doped with nitrogen and oxygen in terms of surface composition and heating behavior with field. A simulation of the diffusion of oxygen into the bulk of the cavity was built using COMSOL Multiphysics software. Simulated results were compared to the actual surface composition of the cavities as determined from secondary ion mass spectrometry analysis. Understanding how these impurities affects performance allows us to have further insight into the underlying mechanisms that enable these surface treatments to yield high Q₀.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK034
About •	Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 30 June 2022
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TUPOMS054	Data Augmentation for Breakdown Prediction in CLIC RF Cavities	operation, cavity, network, experiment	1553
	H.S. Bovbjerg, M. Shen, Z.H. Tan Aalborg University, Aalborg, Denmark A. Apollonio, H.S. Bovbjerg, T. Cartier-Michaud, W.L. Millar, C. Obermair, D. Wollmann CERN, Meyrin, Switzerland C. Obermair TUG, Graz, Austria
	One of the primary limitations on the achievable accelerating gradient in normal-conducting accelerator cavities is the occurrence of vacuum arcs, also known as RF breakdowns. A recent study on experimental data from the CLIC XBOX2 test stand at CERN proposes the use of supervised machine learning methods for predicting RF breakdowns. As RF breakdowns occur relatively infrequently during operation, the majority of the data was instead comprised of non-breakdown pulses. This phenomenon is known in the field of machine learning as class imbalance and is problematic for the training of the models. This paper proposes the use of data augmentation methods to generate synthetic data to counteract this problem. Different data augmentation methods like random transformations and pattern mixing are applied to the experimental data from the XBOX2 test stand, and their efficiency is compared.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS054
About •	Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 15 June 2022
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WEPOTK016	Studies of ECR Plasmas and Materials Modification Using Low Energy Ion Beam Facility at IUAC	plasma, electron, ion-source, cyclotron	2074
	P. Tripathi, P. Kumar, S.K. Singh IUAC, New Delhi, India
	The ECR ion sources are widely used to produce high intensities of highly charged positive ions. To increase their performance further, several techniques are employed. The addition of a lighter gas into the main plasma (so-called gas mixing) shows a substantial effect on the charge state distribution of highly charged ions. Although many theoretical models were used to explain this gas mixing effect, yet it is not fully understood. The low energy ion beam facility (LEIBF) at Inter-University Accelerator Centre (IUAC), New Delhi, India, which comprises a 10 GHz all-permanent magnet NANOGAN ECR source placed on a high voltage platform (400kV) has been used to develop several plasmas for the physical understanding of ions production and their confinement in a strong magnetic field. Further, the LEIBF allows us to extract ion beams from the plasma in the energy range of a few keV to tens of MeV for novel ion-matter interaction experiments. In this paper, the charge state distribution studies (relevant to gas mixing effect) of various atomic species at optimized ion source tuning parameters along with some interesting results on materials synthesis/modification using ion beams is presented. A. G. Drentje, Review of Scientific Instruments 74, 2631 (2003)/ **P. Kumar et al., Pramana 59(5):805-809(2002)/
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK016
About •	Received ※ 31 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 28 June 2022 — Issue date ※ 06 July 2022
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WEPOMS018	Minimum Emittance Growth during RF-Phase Slip	synchrotron, emittance, focusing, operation	2276
	S.R. Koscielniak TRIUMF, Vancouver, Canada
	This paper is concerned with finding operations consistent with the absolute minimum emittance growth. The system is an RF bucket containing a bunch of hadrons in a synchrotron; and the operation performed is to sweep the RF phase. As a result, the bunch centroid moves from one value of position and momentum to another. For given start and end points, we shall find the ideal RF phase-slip time-variation that minimizes emittance growth of the bunch
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS018
About •	Received ※ 27 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 25 June 2022
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THPOST020	Visualisation of Pareto Optimal Spaces and Optimisation Solution Selection Using Parallel Coordinate Plots	cavity, impedance, GUI, RF-structure	2487
	S.J. Smith, R. Apsimon, G. Burt, M.J.W. Southerby Cockcroft Institute, Lancaster University, Lancaster, United Kingdom S. Setiniyaz Cockcroft Institute, Warrington, Cheshire, United Kingdom S. Setiniyaz Lancaster University, Lancaster, United Kingdom
	In this paper, we build on previous work where multi-objective genetic algorithms were used to optimise RF cavities using non-uniform rational basis splines (NURBS) to improve the cavity geometries and reduce peak fields. These optimisations can produce thousands of Pareto optimal solutions, from which a final cavity solution must be selected based on design criteria, such as accelerating gradient and power requirements. As all points are considered equally optimal, this can prove difficult without further analysis. Here we focus on the visualisation of the Pareto optimal points and the final solution selection process. We have found that the use of clustering algorithms and parallel coordinate plots (PCPs) provide the best way to represent the data and perform the necessary trade-offs between the peak fields and shunt impedance required to pick a final design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOST020
About •	Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 29 June 2022
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THPOPT029	Study on the Performance Improvement of Alkali Antimonide Photocathodes for Radio Frequency Electron Guns	cathode, electron, experiment, laser	2640
	R. Fukuoka, K. Ezawa, Y. Koshiba, M. Washio Waseda University, Tokyo, Japan K. Sakaue The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan
	Semiconductor photocathodes such as Cs-Te and Cs-K-Sb are used as electron sources in accelerators to generate high brightness beams using radio frequency (rf) electron guns. Alkali antimonide photocathodes have a high quantum efficiency (Q.E.) of ~10%, and their excitation wavelength is in the visible light region (532 nm), so that they are expected to reduce the requirements on the optical system and increase the amount of charge compared to Cs-Te. However, alkali antimonide photocathodes have a short lifetime and degrade under poor vacuum conditions, so it is essential to improve durability by protective film coatings. Therefore, we are currently working on the fabrication of high Q.E. alkali antimonide photocathodes that can withstand the Q.E. reduction during coating. In this presentation, we will report the results of comparison between the fabricated alkali antimonide photocathode and Cs-Te photocathode, and future prospects.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOPT029
About •	Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 09 July 2022
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THPOPT067	Propagation of Gaussian Wigner Function Through a Matrix-Aperture Beamline	radiation, synchrotron, emittance, synchrotron-radiation	2755
	B. Nash, D.T. Abell, P. Moeller, I.V. Pogorelov RadiaSoft LLC, Boulder, Colorado, USA N.B. Goldring STATE33 Inc., Portland, Oregon, USA
	Funding: This work is supported by the US Department of Energy, Office of Basic Energy Sciences under Award No. DE-SC0020593. We develop a simplified beam propagation model for x-ray beamlines that includes partial coherence as well as the impact of apertures on the beam. In particular, we consider a general asymmetric Gaussian Schell model, which also corresponds to a Gaussian Wigner function. The radiation is thus represented by a 4x4 symmetric second moment matrix. We approximate rectangular apertures by Gaussian apertures, taking care that the loss in flux is the same for the two models. The beam will thus stay Gaussian through both linear transport and passage through the apertures, allowing a self-consistent picture. We derive expressions for decrease in flux and changes in second moments upon passage through the aperture. We also derive expressions for the coherence lengths and analyze how these propagate through linear transport and Gaussian apertures. We apply our formalism to cases of low emittance light source beamlines and develop a better understanding about trade-offs between coherence length increase and flux reduction while passing through physical apertures. Our formulae are implemented in RadiaSoft’s Sirepo Shadow application allowing easy use for realistic beamline models.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOPT067
About •	Received ※ 09 June 2022 — Accepted ※ 11 June 2022 — Issue date ※ 17 June 2022
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THPOTK025	Heat Loads Measurement Methods for the ESS Elliptical Cryomodules SAT at Lund Test Stand	cavity, cryogenics, cryomodule, SRF	2819
	N. Elias, X.T. Su ESS, Lund, Sweden W. Gaj, P. Halczynski, M. Sienkiewicz, F.D. Skalka IFJ-PAN, Kraków, Poland
	The Site Acceptance Testing of all ESS elliptical cryomodules is done at Lund Test Stand. The cryogenic heat loads (static and dynamic) are an essential part of the acceptance criteria. We present complementary measurement methods for evaluating the cryogenic heat loads and discuss a qualitative comparison between them. We also present a summary of the results of these methods for one of the cryomodules.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK025
About •	Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 10 July 2022
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THPOTK029	Role of Surface Chemistry in Conditioning of Materials in Particle Accelerators	electron, radiation, site, multipactoring	2829
	G. Sattonnay, S. Bilgen, S. Della Negra, D. Longuevergne, B. Mercier, I. Ribaud Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	For the vacuum scientists and the accelerator community, finding solutions to mitigate pressure rises induced by electron, photon and ion desorption and beam instabilities induced by ion and electron clouds is a major issue. Along the time, changes in the surface chemistry of vacuum chambers are observed during beam operations in particle accelerators, leading to modifications of: outgassing rates, stimulated desorption processes and a decrease of secondary emission yields (SEY). To understand the role of the surface chemistry of air exposed materials in the electron conditioning process, typical air exposed materials used in particle accelerators : thin film coatings (NEG and TiN), copper (and its oxides Cu2O and CuO) and Niobium were conditioned by low energy electron irradiation for a better understanding of Ecloud effect. First, SEY was measured to understand the changes of surface conditioning upon particle irradiation; then, surface chemistry evolution after electron irradiation was investigated by both XPS and TOF-SIMS analyses using the ANDROMEDE facility at IJCLab. Finally, the relationship between the surface chemistry and the conditioning phenomenon will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK029
About •	Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 22 June 2022 — Issue date ※ 05 July 2022
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THPOTK039	The Effect of Activation Duration on the Performance of Non-Evaporable Getter Coatings	vacuum, injection, experiment, target	2854
	E.A. Marshall, O.B. Malyshev, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Non-evaporable getter (NEG) coatings can be activated at temperatures as low as 140°C. However, better pumping properties are achieved using higher temperatures, between 150-300 °C. This paper investigates whether using an increased activation duration can improve the NEG properties obtained using lower activation temperatures, and so decrease the energy and temperature requirement. This could allow a greater range of materials to be used in particle accelerator systems. Our findings have shown that increasing activation duration from 24 hrs to 1 week at 160 °C produces an improvement in the NEG pumping properties.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK039
About •	Received ※ 01 June 2022 — Accepted ※ 10 June 2022 — Issue date ※ 17 June 2022
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THPOTK062	Thermal Modeling and Benchmarking of Crystalline Laser Amplifiers	laser, simulation, experiment, software	2921
	D.T. Abell, D.L. Bruhwiler, P. Moeller, R. Nagler, B. Nash, I.V. Pogorelov RadiaSoft LLC, Boulder, Colorado, USA Q. Chen, C.G.R. Geddes, C. Tóth, J. van Tilborg LBNL, Berkeley, USA N.B. Goldring STATE33 Inc., Portland, Oregon, USA
	Funding: This work is supported by the US Department of Energy, Office of High Energy Physics under Award Numbers DE-SC0020931 and DE-AC02-05CH11231. Ti:sapphire crystals constitute the lasing medium of a class of lasers valued for their wide tunability and ultra-short, ultra-high intensity pulses. When operated at high power and high repetition rate (1kHz), such lasers experience multiple effects that can degrade performance. In particular, thermal gradients induce a spatial variation in the index of refraction, hence thermal lensing. Using the open-source finite-element code FEniCS*, we solve the relevant partial differential equations to obtain a quantitative measure of the disruptive effects of thermal gradients on beam quality. We present thermal simulations of a pump laser illuminating a Ti:sapphire crystal. From these simulations we identify the radial variation in the refractive index, and hence the extent of thermal lensing. In addition, we present analytic models used to estimate the effect of thermal gradients on beam quality. This work generalizes to other types of crystal amplifiers. S. Cho, et al., Appl. Phys. Express, 11:092701, 2018. M. Born & E. Wolf, Principles of Optics, Cambridge Univ. Press, 1980. * The FEniCS computing platform, https://fenicsproject.org
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK062
About •	Received ※ 13 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 17 June 2022
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THPOMS003	Upgrade of a Proton Therapy Eye Treatment Nozzle Using a Cylindrical Beam Stopping Device for Enhanced Dose Rate Performances	scattering, proton, simulation, radiation	2937
	E. Gnacadja, C. Hernalsteens, N. Pauly, E. Ramoisiaux, R. Tesse, M. Vanwelde ULB, Bruxelles, Belgium C. Hernalsteens CERN, Meyrin, Switzerland
	Proton therapy is a well established treatment method for ocular cancerous diseases. General-purpose multi-room systems which comprise eye-treatment beamlines must be thoroughly optimized to achieve the performances of fully dedicated systems in terms of depth-dose distal fall-off, lateral penumbra, and dose rate. For eye-treatment beamlines, the dose rate is one of the most critical clinical performances, as it directly defines the delivery time of a given treatment session. This delivery time must be kept as low as possible to reduce uncertainties due to undesired patient movement. We propose an alternative design of the Ion Beam Applications (IBA) Proteus Plus (P+) eye treatment beamline, which combines a beam-stopping device with the already existing scattering features of the beamline. The design is modelled with Beam Delivery SIMulation (BDSIM), a Geant4-based particle tracking and beam-matter interactions Monte-Carlo code, to demonstrate that it increases the maximum achievable dose rate by up to a factor §I{3} compared to the baseline configuration. An in-depth study of the system is performed and the resulting dosimetric properties are discussed in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOMS003
About •	Received ※ 20 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 26 June 2022
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THPOMS057	Using Co-Moving Collisions in a Gear-Changing System to Measure Fusion Cross-Sections	luminosity, neutron, experiment, collider	3105
	E.A. Nissen JLab, Newport News, Virginia, USA
	Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a license to publish or reproduce this manuscript. In this work we look at a possible use for a system that collides beams moving in the same direction using a gear-changing synchronization method as a means of measuring low energy phenomena, such as fusion cross sections. Depending on the energies used this process will allow for interactions for any desired charge state of the target nuclei. Earlier concepts for low energy interactions to study focused on beams crossing at an angle to give the low energy interactions, as well as general investigations of comoving collisions. This proposal would use gear-changing, a method involving two different harmonic numbers of bunches in each collider ring, to have the same types of collisions, with a luminosity equal that of a head-on machine. In this work we detail the design considerations for such a machine, leveraging experimental experience with a co-moving, gear-changing system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOMS057
About •	Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 14 June 2022
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Paper

Title

Other Keywords

Page

MOPOPT004

Development of a New Clusterization Method for the GEM-TPC Detector

detector, electron, experiment, electronics

233

M. Luoma, F. Garcia, A. Jokinen, R. Turpeinen, J. Äystö
HIP, University of Helsinki, Finland
T. Blatz, H. Flemming, K. Götzen, C. Karagiannis, N. Kurz, S. Löchner, C. Nociforo, C.J. Schmidt, H. Simon, B. Voss, P. Wieczorek, M. Winkler
GSI, Darmstadt, Germany
D. Chokheli
Georgian Technical University, Tbilisi, Georgia
T. Grahn, S. Rinta-Antila
JYFL, Jyväskylä, Finland

The Facility for Antiproton and Ion Research FAIR, in Darmstadt Germany, will be one of the largest accelerator laboratories worldwide. The Superconducting FRagment Separator (Super-FRS)* is one of its main components. The Super-FRS can produce, separate and deliver high-energy radioactive beams with intensities up to 1e11 ions/s, covering projectiles from protons up to uranium and it can be used as an independent experimental device. The Gas Electron Multiplier-based Time Projection Chambers (GEM-TPC) in twin configuration is a newly developed beam tracking detector capable of providing spatial resolution of less than 1 mm with a tracking efficiency close to 100% at 1 MHz counting rate. The GEM-TPC (HGB4) was tested at the FRagment Separator (FRS), with 238U beam at 850 MeV/u. A new clusterization method was developed, for the first time and used for an analysis. This method allowed to access to waveforms of each strip signal within a single trigger in an event-by-event basis. The procedures involved in this method will be shown in details.
* H.Geissel et al., The Super-FRS project at GSI, Nucl. Instr. and Meth. in Phys., vol. B204, pp. 71-85, 2003.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOPT004

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Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 23 June 2022

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MOPOTK009

Basic Design Choices for the BESSY III MBA Lattice

emittance, lattice, dipole, sextupole

449

B.C. Kuske, M. Abo-Bakr, P. Goslawski
HZB, Berlin, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association.
Lattice development efforts for the 2.5GeV, low emittance successor of BESSY II, are ongoing at HZB for 2 years. The basic choice of a multi-bend achromat lattice is indispensable due to the emittance goal of 100pm, required to generate diffraction limited radiation up to 1keV. Hard boundary conditions for the design are a reasonably short circumference of ~350m due to the accessible construction properties in vicinity to Bessy II and 16 super-periods to not step behind the number of existing experimental stations. Additionally, the Pysikalisch Technische Bundesanstalt, the long-term partner of HZB, requests homogeneous dipoles as a calculable and traceable source of radiation for metrology applications. The configuration of the two building blocks of MBA lattices - unit cell and dispersion suppression cell - has been thoroughly studied from basic principles. It was found that gradient free bending dipoles are the better choice for the BESSY III lattice, opposite to the concepts of comparable projects. This work summarizes and explains the findings of our investigations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOTK009

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Received ※ 21 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 11 June 2022 — Issue date ※ 13 June 2022

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MOPOTK027

Characterization of Various GaN Samples for Photoinjectors

cathode, electron, polarization, brightness

500

M.B. Andorf, I.V. Bazarov, S.J. Levenson, J.M. Maxson
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J. Encomendero, D. Jena, V.V. Protasenko, H.G. Xing
Cornell University, Ithaca, New York, USA

Funding: DOE-HEP DESC0021002 DOE-NP DE-SC0021425
Photoemission properties (quantum efficiency, spectral response, and lifetime) of various GaN based photocathodes are summarized, including p-doped samples in its hexagonal phase, cubic GaN and a more exotic 2-D hole gas sample. The 2-D hole contains no dopant impurity but achieves high conductivity via polarization fields produced at the heterojunction of GaN and AlN. For efficient electron production, cesium is used to achieve Negative Electron Affinity.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOTK027

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Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 26 June 2022

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TUOXSP1

Origin and Mitigation of the Beam-Induced Surface Modifications of the LHC Beam Screens

electron, radiation, cryogenics, MMI

780

V. Petit, P. Chiggiato, M. Himmerlich, S. Marinoni, H. Neupert, M. Taborelli, L.J. Tavian
CERN, Meyrin, Switzerland

All over Run 2, the LHC beam-induced heat load on the cryogenic system exhibited a wide scattering along the ring. Studies ascribed the heat source to electron cloud build-up, indicating an unexpected high Secondary Electron Yield (SEY) of the beam screen surface in some LHC regions. The inner copper surface of high and low heat load beam screens, extracted during the Long Shutdown 2, was analysed. On the low heat load ones, the surface was covered with the native Cu2O oxide, while on the high heat load ones CuO dominated at surface, and it exhibited a very low carbon coverage. Such chemical modifications increase the SEY and inhibit a proper conditioning of the affected surfaces. Following this characterisation, the mechanisms for CuO build-up in the LHC beam pipe were investigated on a newly commissioned cryogenic system allowing electron irradiation, surface chemical characterisation by X-ray Photoelectron Spectroscopy and SEY measurements on samples held below 15 K. In parallel, curative solutions against the presence of CuO in the LHC beam screens were explored, which could be implemented in-situ to recover a proper conditioning and lower the beam-induced heat load.

Slides TUOXSP1 [2.669 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUOXSP1

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Received ※ 17 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 05 July 2022

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TUPOST043

A Novel Method for Detecting Unidentified Falling Object Loss Patterns in the LHC

operation, network, Windows, machine-protect

953

L. Coyle, F. Blanc, D. Di Croce, T. Pieloni
EPFL, Lausanne, Switzerland
L. Coyle, A. Lechner, D. Mirarchi, M. Solfaroli Camillocci, J. Wenninger
CERN, Meyrin, Switzerland

Understanding and mitigating particle losses in the Large Hadron Collider (LHC) is essential for both machine safety and efficient operation. Abnormal loss distributions are telltale signs of abnormal beam behaviour or incorrect machine configuration. By leveraging the advancements made in the field of Machine Learning, a novel data-driven method of detecting anomalous loss distributions during machine operation has been developed. A neural network anomaly detection model was trained to detect Unidentified Falling Object events using stable beam, Beam Loss Monitor (BLM) data acquired during the operation of the LHC. Data-driven models, such as the one presented, could lead to significant improvements in the autonomous labelling of abnormal loss distributions, ultimately bolstering the ever ongoing effort toward improving the understanding and mitigation of these events.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST043

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Received ※ 19 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 21 June 2022

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TUPOPT039

Characterization of Diamond with Buried Boron-Doped Layer Developed for Q-Switching an X-Ray Optical Cavity

cavity, FEL, laser, lattice

1097

R.A. Margraf, A. Halavanau, Z. Huang, J. Krzywiński, J.P. MacArthur, G. Marcus, M.L. Ng, A.R. Robert, R. Robles, T. Sato, D. Zhu
SLAC, Menlo Park, California, USA
Z. Huang, F. Ke, R. Robles, Y. Zhong
Stanford University, Stanford, California, USA
S.-K. Mo, Y. Zhong
LBNL, Berkeley, California, USA
P. Pradhan
ANL, Lemont, Illinois, USA
A.R. Robert
MAX IV Laboratory, Lund University, Lund, Sweden
M.D. Ynsa
UAM, Madrid, Spain

Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
X-ray Free-Electron Laser Oscillators (XFELOs) and X-ray Regenerative Amplifier FELs (XRAFELs) are currently in development to improve longitudinal coherence and spectral brightness of XFELs. These schemes lase an electron beam in an undulator within an optical cavity to produce X-rays. X-rays circulate in the cavity and interact with fresh electron bunches to seed the FEL process over multiple passes, producing progressively brighter and more spectrally pure X-rays. Typically, the optical cavities used are composed of Bragg-reflecting mirrors to provide high reflectivity and spectral filtering. This high reflectivity necessitates special techniques to out-couple X-rays from the cavity to deliver them to users. One method involves "Q-switching" the cavity by actively modifying the reflectivity of one Bragg-reflecting crystal. To control the crystal lattice constant and thus reflectivity, we use an infrared laser to heat a buried boron layer in a diamond crystal. Here, we build on earlier work in Krzywinski et al.* and present the current status of our Q-switching diamond, including implantation with 9 MeV boron ions, annealing, characterization and early tests.
*Krzywinski et al., "Q-switching of X-Ray Optical Cavities by using Boron Doped Buried Layer under a Surface of a Diamond Crystal," Proceedings of FEL2019, Hamburg, Germany, TUP033, 2019.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT039

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Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 08 July 2022

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TUPOTK009

Development of Superconducting CH Cavity Preparation at IAP

cavity, simulation, coupling, vacuum

1208

P. Müller, H. Podlech
IAP, Frankfurt am Main, Germany
K. Aulenbacher, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, M. Basten, V. Gettmann, T. Kürzeder, M. Miski-Oglu
GSI, Darmstadt, Germany

Funding: HIC for FAIR, BMBF Contr. No. 05P21RFRB2 and HFHF
Goethe University (GU), Gesellschaft für Schwerionenforschung (GSI) and Helmholtz Institut Mainz (HIM) work in collaboration on the Helmholtz Linear Accelerator (HELIAC). A new superconducting (sc) continous wave (cw) high intensity heavy ion linear accelerator (Linac) will provide ion beams with maximum duty factor up to beam energies of 7.3 MeV/u. The acceleration voltage will be provided by sc Crossbar-H-mode (CH) cavities, developed of Institute for Applied Physics (IAP) at GU. Cavity preparation is researched and optimized towards widely used elliptical multicell cavities. A standardized preparation protocol for CH cavities is researched in collaboration between GU, GSI and HIM on a 360 MHz 19 gap CH prototype. Baseline measurements and a 120°C 48 hour bake produced higher maximum gradient, higher intrinsic quality factor and a shorter cavity conditioning phase. As a critical preparation step, High Pressure Rinsing (HPR) with ultra pure water will be performed at HIM and is currently in preparation. HPR cycles are currently tested on a CH dummy with a new nozzle layout that is optimized towards CH cavity geometry.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK009

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Received ※ 08 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 18 June 2022 — Issue date ※ 02 July 2022

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TUPOTK011

Commissioning of a New Magnetometric Mapping System for SRF Cavity Performance Tests

cavity, SRF, niobium, superconducting-cavity

1215

J.C. Wolff, J. Eschke, A. Gössel, D. Reschke, L. Steder, L. Trelle
DESY, Hamburg, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
Magnetic flux trapped in the niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity for flux trapping is mainly determined by the treatment and the geometry of the cavity as well as the niobium grain size and orientation. To potentially improve the flux expulsion characteristics of SRF cavities and hence the efficiency of future accelerator facilities, further studies of the trapping behavior are essential. For this purpose a magnetometric mapping system to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities has been developed and is currently in the commissioning phase at DESY. Contrary to similar approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs. Furthermore, the signal-to-noise ratio (SNR) and consequently the measuring sensitivity can be enhanced by shorter analog signal lines, less thermal noise and the Mu-metal shielding of the cryostat. In this contribution test results gained by a prototype of the mapping system are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK011

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Received ※ 10 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 29 June 2022

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TUPOTK012

Nitrogen Infusion Sample R&D at DESY

cavity, niobium, vacuum, accelerating-gradient

1219

C. Bate
University of Hamburg, Hamburg, Germany
A. Ermakov, D. Reschke, J. Schaffran
DESY, Hamburg, Germany
W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
Many accelerator projects such as the ILC would benefit from cavities with reduced surface resistance (high Q-values) while maintaining a high accelerating gradient. A possible way to meet the requirements is the so-called nitrogen-infusion procedure on Niobium cavities. However, a fundamental understanding and a theoretical model of this method are still missing. One important parameter is the residual resistance ratio (RRR) which is related to the impurity content of the material. We report the investigated RRR on samples in a wide temperature range in a vacuum and under a nitrogen atmosphere. This comparison made it possible to make statements about the differences in the concentration of nitrogen by varying the temperature. The samples are pure cavity-grade niobium and treated in the same manner as cavities. For this purpose, a small furnace dedicated to sample treatment was set up to change and explore the parameter space of the infusion recipe. Care was taken to achieve the highest level of purity possible in the furnace and in a pressure range of 1.0·10^-8 mbar in order to meet the high requirements of nitrogen infusion.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK012

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Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 01 July 2022

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TUPOTK034

Evaluating the Effects of Nitrogen Doping and Oxygen Doping on SRF Cavity Performance

cavity, SRF, niobium, simulation

1287

H. Hu, Y.K. Kim
University of Chicago, Chicago, Illinois, USA
D. Bafia
Fermilab, Batavia, Illinois, USA

Superconducting radiofrequency (SRF) cavities are resonators with extremely low surface resistance that enable accelerating cavities to have extremely high quality factors (Q₀). High Q₀ decreases the capital required to keep the accelerators cold by reducing power loss. The performance of SRF cavities is largely governed by the surface composition of the first §I{100}{nm} of the cavity surface. Impurities such as oxygen and nitrogen have been observed to yield high Q₀, but their precise roles are still being studied. Here, we compare the performance of cavities doped with nitrogen and oxygen in terms of surface composition and heating behavior with field. A simulation of the diffusion of oxygen into the bulk of the cavity was built using COMSOL Multiphysics software. Simulated results were compared to the actual surface composition of the cavities as determined from secondary ion mass spectrometry analysis. Understanding how these impurities affects performance allows us to have further insight into the underlying mechanisms that enable these surface treatments to yield high Q₀.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK034

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Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 30 June 2022

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TUPOMS054

Data Augmentation for Breakdown Prediction in CLIC RF Cavities

operation, cavity, network, experiment

1553

H.S. Bovbjerg, M. Shen, Z.H. Tan
Aalborg University, Aalborg, Denmark
A. Apollonio, H.S. Bovbjerg, T. Cartier-Michaud, W.L. Millar, C. Obermair, D. Wollmann
CERN, Meyrin, Switzerland
C. Obermair
TUG, Graz, Austria

One of the primary limitations on the achievable accelerating gradient in normal-conducting accelerator cavities is the occurrence of vacuum arcs, also known as RF breakdowns. A recent study on experimental data from the CLIC XBOX2 test stand at CERN proposes the use of supervised machine learning methods for predicting RF breakdowns. As RF breakdowns occur relatively infrequently during operation, the majority of the data was instead comprised of non-breakdown pulses. This phenomenon is known in the field of machine learning as class imbalance and is problematic for the training of the models. This paper proposes the use of data augmentation methods to generate synthetic data to counteract this problem. Different data augmentation methods like random transformations and pattern mixing are applied to the experimental data from the XBOX2 test stand, and their efficiency is compared.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS054

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Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 15 June 2022

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WEPOTK016

Studies of ECR Plasmas and Materials Modification Using Low Energy Ion Beam Facility at IUAC

plasma, electron, ion-source, cyclotron

2074

P. Tripathi, P. Kumar, S.K. Singh
IUAC, New Delhi, India

The ECR ion sources are widely used to produce high intensities of highly charged positive ions*. To increase their performance further, several techniques are employed. The addition of a lighter gas into the main plasma (so-called gas mixing) shows a substantial effect on the charge state distribution of highly charged ions. Although many theoretical models were used to explain this gas mixing effect, yet it is not fully understood. The low energy ion beam facility (LEIBF) at Inter-University Accelerator Centre (IUAC), New Delhi, India, which comprises a 10 GHz all-permanent magnet NANOGAN ECR source placed on a high voltage platform (400kV) has been used to develop several plasmas for the physical understanding of ions production and their confinement in a strong magnetic field**. Further, the LEIBF allows us to extract ion beams from the plasma in the energy range of a few keV to tens of MeV for novel ion-matter interaction experiments. In this paper, the charge state distribution studies (relevant to gas mixing effect) of various atomic species at optimized ion source tuning parameters along with some interesting results on materials synthesis/modification using ion beams is presented.
*A. G. Drentje, Review of Scientific Instruments 74, 2631 (2003)/ **P. Kumar et al., Pramana 59(5):805-809(2002)/

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK016

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Received ※ 31 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 28 June 2022 — Issue date ※ 06 July 2022

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WEPOMS018

Minimum Emittance Growth during RF-Phase Slip

synchrotron, emittance, focusing, operation

2276

S.R. Koscielniak
TRIUMF, Vancouver, Canada

This paper is concerned with finding operations consistent with the absolute minimum emittance growth. The system is an RF bucket containing a bunch of hadrons in a synchrotron; and the operation performed is to sweep the RF phase. As a result, the bunch centroid moves from one value of position and momentum to another. For given start and end points, we shall find the ideal RF phase-slip time-variation that minimizes emittance growth of the bunch

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS018

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Received ※ 27 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 25 June 2022

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THPOST020

Visualisation of Pareto Optimal Spaces and Optimisation Solution Selection Using Parallel Coordinate Plots

cavity, impedance, GUI, RF-structure

2487

S.J. Smith, R. Apsimon, G. Burt, M.J.W. Southerby
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
S. Setiniyaz
Cockcroft Institute, Warrington, Cheshire, United Kingdom
S. Setiniyaz
Lancaster University, Lancaster, United Kingdom

In this paper, we build on previous work where multi-objective genetic algorithms were used to optimise RF cavities using non-uniform rational basis splines (NURBS) to improve the cavity geometries and reduce peak fields. These optimisations can produce thousands of Pareto optimal solutions, from which a final cavity solution must be selected based on design criteria, such as accelerating gradient and power requirements. As all points are considered equally optimal, this can prove difficult without further analysis. Here we focus on the visualisation of the Pareto optimal points and the final solution selection process. We have found that the use of clustering algorithms and parallel coordinate plots (PCPs) provide the best way to represent the data and perform the necessary trade-offs between the peak fields and shunt impedance required to pick a final design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOST020

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Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 29 June 2022

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THPOPT029

Study on the Performance Improvement of Alkali Antimonide Photocathodes for Radio Frequency Electron Guns

cathode, electron, experiment, laser

2640

R. Fukuoka, K. Ezawa, Y. Koshiba, M. Washio
Waseda University, Tokyo, Japan
K. Sakaue
The University of Tokyo, Graduate School of Engineering, Bunkyo, Japan

Semiconductor photocathodes such as Cs-Te and Cs-K-Sb are used as electron sources in accelerators to generate high brightness beams using radio frequency (rf) electron guns. Alkali antimonide photocathodes have a high quantum efficiency (Q.E.) of ~10%, and their excitation wavelength is in the visible light region (532 nm), so that they are expected to reduce the requirements on the optical system and increase the amount of charge compared to Cs-Te. However, alkali antimonide photocathodes have a short lifetime and degrade under poor vacuum conditions, so it is essential to improve durability by protective film coatings. Therefore, we are currently working on the fabrication of high Q.E. alkali antimonide photocathodes that can withstand the Q.E. reduction during coating. In this presentation, we will report the results of comparison between the fabricated alkali antimonide photocathode and Cs-Te photocathode, and future prospects.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOPT029

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Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 09 July 2022

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THPOPT067

Propagation of Gaussian Wigner Function Through a Matrix-Aperture Beamline

radiation, synchrotron, emittance, synchrotron-radiation

2755

B. Nash, D.T. Abell, P. Moeller, I.V. Pogorelov
RadiaSoft LLC, Boulder, Colorado, USA
N.B. Goldring
STATE33 Inc., Portland, Oregon, USA

Funding: This work is supported by the US Department of Energy, Office of Basic Energy Sciences under Award No. DE-SC0020593.
We develop a simplified beam propagation model for x-ray beamlines that includes partial coherence as well as the impact of apertures on the beam. In particular, we consider a general asymmetric Gaussian Schell model, which also corresponds to a Gaussian Wigner function. The radiation is thus represented by a 4x4 symmetric second moment matrix. We approximate rectangular apertures by Gaussian apertures, taking care that the loss in flux is the same for the two models. The beam will thus stay Gaussian through both linear transport and passage through the apertures, allowing a self-consistent picture. We derive expressions for decrease in flux and changes in second moments upon passage through the aperture. We also derive expressions for the coherence lengths and analyze how these propagate through linear transport and Gaussian apertures. We apply our formalism to cases of low emittance light source beamlines and develop a better understanding about trade-offs between coherence length increase and flux reduction while passing through physical apertures. Our formulae are implemented in RadiaSoft’s Sirepo Shadow application allowing easy use for realistic beamline models.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOPT067

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Received ※ 09 June 2022 — Accepted ※ 11 June 2022 — Issue date ※ 17 June 2022

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THPOTK025

Heat Loads Measurement Methods for the ESS Elliptical Cryomodules SAT at Lund Test Stand

cavity, cryogenics, cryomodule, SRF

2819

N. Elias, X.T. Su
ESS, Lund, Sweden
W. Gaj, P. Halczynski, M. Sienkiewicz, F.D. Skalka
IFJ-PAN, Kraków, Poland

The Site Acceptance Testing of all ESS elliptical cryomodules is done at Lund Test Stand. The cryogenic heat loads (static and dynamic) are an essential part of the acceptance criteria. We present complementary measurement methods for evaluating the cryogenic heat loads and discuss a qualitative comparison between them. We also present a summary of the results of these methods for one of the cryomodules.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK025

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Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 10 July 2022

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THPOTK029

Role of Surface Chemistry in Conditioning of Materials in Particle Accelerators

electron, radiation, site, multipactoring

2829

G. Sattonnay, S. Bilgen, S. Della Negra, D. Longuevergne, B. Mercier, I. Ribaud
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

For the vacuum scientists and the accelerator community, finding solutions to mitigate pressure rises induced by electron, photon and ion desorption and beam instabilities induced by ion and electron clouds is a major issue. Along the time, changes in the surface chemistry of vacuum chambers are observed during beam operations in particle accelerators, leading to modifications of: outgassing rates, stimulated desorption processes and a decrease of secondary emission yields (SEY). To understand the role of the surface chemistry of air exposed materials in the electron conditioning process, typical air exposed materials used in particle accelerators : thin film coatings (NEG and TiN), copper (and its oxides Cu2O and CuO) and Niobium were conditioned by low energy electron irradiation for a better understanding of Ecloud effect. First, SEY was measured to understand the changes of surface conditioning upon particle irradiation; then, surface chemistry evolution after electron irradiation was investigated by both XPS and TOF-SIMS analyses using the ANDROMEDE facility at IJCLab. Finally, the relationship between the surface chemistry and the conditioning phenomenon will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK029

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Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 22 June 2022 — Issue date ※ 05 July 2022

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THPOTK039

The Effect of Activation Duration on the Performance of Non-Evaporable Getter Coatings

vacuum, injection, experiment, target

2854

E.A. Marshall, O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Non-evaporable getter (NEG) coatings can be activated at temperatures as low as 140°C. However, better pumping properties are achieved using higher temperatures, between 150-300 °C. This paper investigates whether using an increased activation duration can improve the NEG properties obtained using lower activation temperatures, and so decrease the energy and temperature requirement. This could allow a greater range of materials to be used in particle accelerator systems. Our findings have shown that increasing activation duration from 24 hrs to 1 week at 160 °C produces an improvement in the NEG pumping properties.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK039

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Received ※ 01 June 2022 — Accepted ※ 10 June 2022 — Issue date ※ 17 June 2022

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THPOTK062

Thermal Modeling and Benchmarking of Crystalline Laser Amplifiers

laser, simulation, experiment, software

2921

D.T. Abell, D.L. Bruhwiler, P. Moeller, R. Nagler, B. Nash, I.V. Pogorelov
RadiaSoft LLC, Boulder, Colorado, USA
Q. Chen, C.G.R. Geddes, C. Tóth, J. van Tilborg
LBNL, Berkeley, USA
N.B. Goldring
STATE33 Inc., Portland, Oregon, USA

Funding: This work is supported by the US Department of Energy, Office of High Energy Physics under Award Numbers DE-SC0020931 and DE-AC02-05CH11231.
Ti:sapphire crystals constitute the lasing medium of a class of lasers valued for their wide tunability and ultra-short, ultra-high intensity pulses. When operated at high power and high repetition rate (1kHz), such lasers experience multiple effects that can degrade performance. In particular, thermal gradients induce a spatial variation in the index of refraction, hence thermal lensing*. Using the open-source finite-element code FEniCS***, we solve the relevant partial differential equations to obtain a quantitative measure of the disruptive effects of thermal gradients on beam quality. We present thermal simulations of a pump laser illuminating a Ti:sapphire crystal. From these simulations we identify the radial variation in the refractive index, and hence the extent of thermal lensing. In addition, we present analytic models used to estimate the effect of thermal gradients on beam quality. This work generalizes to other types of crystal amplifiers.
* S. Cho, et al., Appl. Phys. Express, 11:092701, 2018.
** M. Born & E. Wolf, Principles of Optics, Cambridge Univ. Press, 1980.
*** The FEniCS computing platform, https://fenicsproject.org

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK062

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Received ※ 13 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 17 June 2022

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THPOMS003

Upgrade of a Proton Therapy Eye Treatment Nozzle Using a Cylindrical Beam Stopping Device for Enhanced Dose Rate Performances

scattering, proton, simulation, radiation

2937

E. Gnacadja, C. Hernalsteens, N. Pauly, E. Ramoisiaux, R. Tesse, M. Vanwelde
ULB, Bruxelles, Belgium
C. Hernalsteens
CERN, Meyrin, Switzerland

Proton therapy is a well established treatment method for ocular cancerous diseases. General-purpose multi-room systems which comprise eye-treatment beamlines must be thoroughly optimized to achieve the performances of fully dedicated systems in terms of depth-dose distal fall-off, lateral penumbra, and dose rate. For eye-treatment beamlines, the dose rate is one of the most critical clinical performances, as it directly defines the delivery time of a given treatment session. This delivery time must be kept as low as possible to reduce uncertainties due to undesired patient movement. We propose an alternative design of the Ion Beam Applications (IBA) Proteus Plus (P+) eye treatment beamline, which combines a beam-stopping device with the already existing scattering features of the beamline. The design is modelled with Beam Delivery SIMulation (BDSIM), a Geant4-based particle tracking and beam-matter interactions Monte-Carlo code, to demonstrate that it increases the maximum achievable dose rate by up to a factor §I{3} compared to the baseline configuration. An in-depth study of the system is performed and the resulting dosimetric properties are discussed in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOMS003

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Received ※ 20 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 26 June 2022

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THPOMS057

Using Co-Moving Collisions in a Gear-Changing System to Measure Fusion Cross-Sections

luminosity, neutron, experiment, collider

3105

E.A. Nissen
JLab, Newport News, Virginia, USA

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a license to publish or reproduce this manuscript.
In this work we look at a possible use for a system that collides beams moving in the same direction using a gear-changing synchronization method as a means of measuring low energy phenomena, such as fusion cross sections. Depending on the energies used this process will allow for interactions for any desired charge state of the target nuclei. Earlier concepts for low energy interactions to study focused on beams crossing at an angle to give the low energy interactions, as well as general investigations of comoving collisions. This proposal would use gear-changing, a method involving two different harmonic numbers of bunches in each collider ring, to have the same types of collisions, with a luminosity equal that of a head-on machine. In this work we detail the design considerations for such a machine, leveraging experimental experience with a co-moving, gear-changing system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOMS057

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Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 14 June 2022

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