Author: Gilfellon, A.J.
Paper Title Page
THPOJO09 Status of CLARA at Daresbury Laboratory 711
 
  • D. Angal-Kalinin, A.R. Bainbridge, A.D. Brynes, R.K. Buckley, S.R. Buckley, H.M. Castañeda Cortés, J.A. Clarke, L.S. Cowie, K.D. Dumbell, D.J. Dunning, A.J. Gilfellon, A.R. Goulden, J. Henderson, S. Hitchen, F. Jackson, C.R. Jenkins, M.A. Johnson, J.K. Jones, N.Y. Joshi, M.P. King, S.L. Mathisen, J.W. McKenzie, R. Mclean, K.J. Middleman, B.L. Militsyn, K.T. Morrow, A.J. Moss, B.D. Muratori, T.C.Q. Noakes, W.A. Okell, H.L. Owen, T.H. Pacey, A.E. Pollard, M.D. Roper, Y.M. Saveliev, D.J. Scott, B.J.A. Shepherd, R.J. Smith, E.W. Snedden, N. Thompson, C. Tollervey, R. Valizadeh, D.A. Walsh, A.E. Wheelhouse, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • A.R. Bainbridge, A.D. Brynes, J.A. Clarke, L.S. Cowie, K.D. Dumbell, D.J. Dunning, C.R. Jenkins, K.J. Middleman, A.J. Moss, B.D. Muratori, H.L. Owen, Y.M. Saveliev, D.J. Scott, B.J.A. Shepherd, N. Thompson, R. Valizadeh, A.J. Vick, A.E. Wheelhouse
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • A.D. Brynes
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • R.J. Cash, R.F. Clarke, M. Colling, G. Cox, B.D. Fell, S.A. Griffiths, M.D. Hancock, T. Hartnett, J.P. Hindley, C. Hodgkinson, G. Marshall, A. Oates, A.J. Vick, J.T.G. Wilson
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • J. Henderson
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  
  CLARA (Com­pact Lin­ear Ac­cel­er­a­tor for Re­search and Ap­pli­ca­tions) is a test fa­cil­ity for Free Elec­tron Laser (FEL) re­search and other ap­pli­ca­tions at STFC’s Dares­bury Lab­o­ra­tory. The Front End of CLARA has been used for user ex­ploita­tion pro­gramme from 2018. The sec­ond ex­ploita­tion pe­riod in 2021-22 pro­vided a range of beam pa­ra­me­ters to 8 user ex­per­i­ments. We re­port on the sta­tus, fur­ther ma­chine de­vel­op­ment, and fu­ture plans for CLARA in­clud­ing Full En­ergy Beam Ex­ploita­tion (FEBE) beam­line which will pro­vide 250 MeV/c high bright­ness beam for novel ex­per­i­ments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOJO09  
About • Received ※ 19 August 2022 — Revised ※ 28 August 2022 — Accepted ※ 05 September 2022 — Issue date ※ 15 September 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPOJO10 RF Design and Characterisation of the CLARA 10 Hz Gun with Photocathode Load/Lock Upgrade 715
 
  • A.J. Gilfellon, L.S. Cowie, T.J. Jones, B.L. Militsyn, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  The 2.5 cell S-band 10 Hz rep­e­ti­tion rate elec­tron gun (Gun-10) for the CLARA (Com­pact Lin­ear Ac­cel­er­a­tor for Re­search and Ap­pli­ca­tions) fa­cil­ity un­der­went an up­grade dur­ing the sched­uled shut­down pe­riod dur­ing the sum­mer of 2019. The ex­ist­ing pho­to­cath­ode/back plate was re­placed by a new back plate with in­ter­change­able pho­to­cath­ode socket con­nected to a load/lock sys­tem ca­pa­ble of rapid ex­changes of pho­to­cath­ode plugs. Here we out­line mo­ti­va­tion and RF de­sign of the back plate and also de­tail the low power RF test­ing and char­ac­ter­i­sa­tion of the up­graded gun in terms of the un­loaded qual­ity fac­tor, the RF power cou­pling match, the per­cent field flat­ness and the op­er­at­ing fre­quency of the cav­ity, cal­cu­lated from the fre­quency mea­sured in the lab­o­ra­tory. Fi­nally, via sim­u­la­tions using CST MWS and ASTRA, we pro­duce a de­pen­dence of ex­pected beam mo­men­tum vs for­ward power that we pre­dict the gun will de­liver once it goes back on­line.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOJO10  
About • Received ※ 25 August 2022 — Revised ※ 31 August 2022 — Accepted ※ 31 August 2022 — Issue date ※ 16 September 2022
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THPORI15 Operation of the CLARA Linear Accelerator with 2.5 Cell 10 Hz Photocathode Gun with Interchangeable Photocathodes 854
 
  • B.L. Militsyn, D. Angal-Kalinin, A.R. Bainbridge, L.S. Cowie, A.J. Gilfellon, F. Jackson, N.Y. Joshi, K.J. Middleman, K.T. Morrow, T.C.Q. Noakes, M.D. Roper, R. Valizadeh, D.A. Walsh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R.J. Cash, B.D. Fell, T.J. Jones, A.J. Vick
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  Dur­ing com­mis­sion­ing and op­er­a­tion run in 2021-2022 the pho­toin­jec­tor of the CLARA-VELA fa­cil­ity a 2.5 cell cav­ity S-band pho­to­cath­ode gun orig­i­nally de­vel­oped for the APEX ex­per­i­ment was used. The cop­per back wall of the cav­ity also served as the gun pho­to­cath­ode. In order to re­duce sig­nif­i­cant time re­quired for re­place­ment and/or re­ac­ti­va­tion of the pho­to­cath­ode and im­prove the flex­i­bil­ity of the in­jec­tor the gun has been up­graded for op­er­a­tion with DESY/INFN style in­ter­change­able pho­to­cath­odes. This up­grade in­cluded a new de­sign of the cav­ity back wall to ac­com­mo­date the pho­to­cath­ode socket and equip­ping the gun with a load-lock sys­tem. Mod­i­fi­ca­tion of the gun also re­quired re­place­ment of the buck­ing coil, which zeros field in the pho­to­cath­ode emis­sion plane. After the up­grade, the gun was com­mis­sioned and then op­er­ated with a hy­brid Cu/Mo pho­to­cath­ode dur­ing the last two years. Dur­ing win­ter-spring 2022 ex­per­i­men­tal run the gun steadily op­er­ated with a cath­ode field of 60 MV/m, lim­ited by the RF power avail­able and with an off-cen­tre di­a­mond turned pho­to­cath­ode which de­liv­ered sta­ble bunches with a charge of 100 pC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPORI15  
About • Received ※ 24 August 2022 — Revised ※ 08 September 2022 — Accepted ※ 12 September 2022 — Issue date ※ 15 October 2022
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THPORI16 Machine Learning for RF Breakdown Detection at CLARA 858
 
  • A.E. Pollard, D.J. Dunning, A.J. Gilfellon
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  Max­imis­ing the ac­cel­er­at­ing gra­di­ent of RF struc­tures is fun­da­men­tal to im­prov­ing ac­cel­er­a­tor fa­cil­ity per­for­mance and cost-ef­fec­tive­ness. Struc­tures must be sub­jected to a con­di­tion­ing process be­fore op­er­a­tional use, in which the gra­di­ent is grad­u­ally in­creased up to the op­er­at­ing value. A lim­it­ing ef­fect dur­ing this process is break­down or vac­uum arc­ing, which can cause dam­age that lim­its the ul­ti­mate op­er­at­ing gra­di­ent. Tech­niques to ef­fi­ciently con­di­tion the cav­i­ties while min­imis­ing the num­ber of break­downs are there­fore im­por­tant. In this paper, ma­chine learn­ing tech­niques are ap­plied to de­tect break­down events in RF pulse traces by ap­proach­ing the prob­lem as anom­aly de­tec­tion, using a vari­a­tional au­toen­coder. This process de­tects de­vi­a­tions from nor­mal op­er­a­tion and clas­si­fies them with near per­fect ac­cu­racy. Of­fline data from var­i­ous sources has been used to de­velop the tech­niques, which we aim to test at the CLARA fa­cil­ity at Dares­bury Lab­o­ra­tory. De­ploy­ment of the ma­chine learn­ing sys­tem on the high rep­e­ti­tion rate gun up­grade at CLARA has begun.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPORI16  
About • Received ※ 22 August 2022 — Revised ※ 30 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 15 October 2022
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