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MOPAB068 Collective Effects Studies for the SOLEIL Upgrade impedance, synchrotron, storage-ring, cavity 274
 
  • A. Gamelin, D. Amorim, P. Brunelle, W. Foosang, A. Loulergue, L.S. Nadolski, R. Nagaoka, R. Ollier, M.-A. Tordeux
    SOLEIL, Gif-sur-Yvette, France
  
  The SOLEIL up­grade pro­ject aims to re­place the ac­tual SOLEIL stor­age ring by a 4th gen­er­a­tion light source. The pro­ject has just fin­ished its con­cep­tual de­sign re­port (CDR) phase*. Com­pared to the SOLEIL stor­age ring, the up­graded stor­age ring de­sign in­cludes many new fea­tures of 4th gen­er­a­tion light sources that will im­pact col­lec­tive ef­fects, such as re­duced beam pipe aper­tures, a smaller mo­men­tum com­paction fac­tor and the pres­ence of har­monic cav­i­ties (HC). To mit­i­gate them, we rely on sev­eral damp­ing mech­a­nisms pro­vided by the syn­chro­tron ra­di­a­tion, the trans­verse feed­back sys­tem, and the HC (Lan­dau damp­ing and bunch length­en­ing). This ar­ti­cle pre­sents a first es­ti­mate of the col­lec­tive ef­fects im­pact of the up­graded de­sign.
* Conceptual Design Report: Synchrotron SOLEIL Upgrade, 2021, in press. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB068  
About • paper received ※ 17 May 2021       paper accepted ※ 02 June 2021       issue date ※ 12 August 2021  
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MOPAB079 Experience of the First Six Years Operations and Plans in NSlS-II operation, cavity, MMI, vacuum 308
 
  • G.M. Wang
    BNL, Upton, New York, USA
  
  NSLS-II is a 3 GeV third-gen­er­a­tion syn­chro­tron light source at BNL. The stor­age ring was com­mis­sioned in 2014 and began its rou­tine op­er­a­tions in the De­cem­ber of the same year. Since then, we have been con­tin­u­ously in­stalling and com­mis­sion­ing new in­ser­tion de­vices, their front-ends, and beam­lines. At this point, the fa­cil­ity hosts 28 op­er­at­ing beam­lines from var­i­ous ra­di­a­tion sources, in­clud­ing damp­ing wig­gler, IVU, EPU, 3PW, and bend­ing mag­nets for in­frared beam­lines. Over the past six years, the stor­age ring per­for­mance con­tin­u­ously im­proved, in­clud­ing 500 mA with lim­ited in­ser­tion de­vices close due to RF power lim­i­ta­tion and rou­tinely 400 mA top off op­er­a­tion, >95% op­er­a­tion re­li­a­bil­ity, main­te­nance of beam mo­tion short- and long-term sta­bil­ity. In this paper, we re­port NSLS-II ac­cel­er­a­tor op­er­a­tions ex­pe­ri­ence and plans for fu­ture fa­cil­ity de­vel­op­ments.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB079  
About • paper received ※ 17 May 2021       paper accepted ※ 21 June 2021       issue date ※ 25 August 2021  
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MOPAB087 Design of a Multi-Bunch Feedback Kicker in SPEAR3 kicker, impedance, simulation, coupling 327
 
  • K. Tian, J.B. Langton, NL. Parry, J.A. Safranek, J.J. Sebek
    SLAC, Menlo Park, California, USA
  
  The new Multi-bunch feed­back kick­ers have been de­signed to re­place the cur­rent de­vice loaned from ALS. In this paper, we first pre­sent the spec­i­fi­ca­tion of the kick­ers based on the beam physics re­quire­ments. Then the me­chan­i­cal de­sign of the kicker is elab­o­rated. Nu­mer­i­cal sim­u­la­tions, both in time do­main and in fre­quency do­main, are con­ducted for eval­u­at­ing the shunt im­ped­ance and beam cou­pling im­ped­ance of the kicker. Sur­face heat­ing in­duced from the beam or the ex­ter­nal source is es­ti­mated from the nu­mer­i­cal re­sults as well.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB087  
About • paper received ※ 19 May 2021       paper accepted ※ 11 June 2021       issue date ※ 01 September 2021  
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MOPAB088 Beam-Based Measurement on the Performance of Ferrite Dampers in an In-Vacuum Undulator damping, HOM, radiation, vacuum 331
 
  • K. Tian, A. Ringwall, J.J. Sebek
    SLAC, Menlo Park, California, USA
  
  In this paper, we first pre­sent the track­ing stud­ies for SPEAR3 with the new BL17 ID and es­ti­mate its im­pact on the dy­namic aper­ture of the low emit­tance lat­tice. Then the fer­rite dampers in­stal­la­tions in the de­vice is briefly re­viewed. After that, we will show that, based on beam-based mea­sure­ments, the per­for­mance of the dampers is as being ex­pected from ear­lier nu­mer­i­cal stud­ies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB088  
About • paper received ※ 19 May 2021       paper accepted ※ 18 June 2021       issue date ※ 24 August 2021  
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MOPAB275 Study on Supports of BPM Displacement Measurement System for HLS simulation, acceleration, factory, storage-ring 870
 
  • C.H. Wang, P. Lu, B.G. Sun, T.Y. Zhou
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  
  Funding: National Synchrotron Radiation Laboratory
HLS is the sec­ond-gen­er­a­tion light source with en­ergy of 800 MeV and emit­tance of less than 40 nm-rad. In order to im­prove the beam orbit sta­bil­ity and cor­rect the er­rors in­tro­duced in the or­bital feed­back sys­tem due to move­ment of the vac­uum cham­ber and BPM, a sys­tem for mea­sur­ing BPM dis­place­ment will be built. It re­quires a high de­gree of me­chan­i­cal and ther­mal sta­bil­ity for its sup­ports. The sup­port should have a higher eigen-fre­quency to min­i­mize the am­pli­fi­ca­tion of ground vi­bra­tion. In this paper, a se­ries of sim­u­la­tion, in­clud­ing fi­nite el­e­ment analy­sis (FEA), mea­sure­ment and analy­sis have been done upon the sup­port to make sure it can meet the re­quire­ments of the sta­bil­ity of the BPM dis­place­ment mea­sure­ment sys­tem. 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB275  
About • paper received ※ 18 May 2021       paper accepted ※ 21 May 2021       issue date ※ 26 August 2021  
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MOPAB362 Atomistic Modeling of the Coupling Between Electric Fields and Bulk Plastic Deformation in Rf Structures simulation, experiment, coupling, framework 1125
 
  • S. Bagchi, D. Perez
    LANL, Los Alamos, New Mexico, USA
  
  Funding: LANL-LDRD
A no­table bot­tle­neck in achiev­ing high-gra­di­ent RF tech­nol­ogy is dic­tated by the onset of RF break­down. While bulk me­chan­i­cal prop­er­ties are known to sig­nif­i­cantly af­fect break­down propen­sity, the un­der­ly­ing mech­a­nisms cou­pling RF fields to bulk plas­tic de­for­ma­tion in ex­per­i­men­tally rel­e­vant thermo-elec­tri­cal load­ing con­di­tions re­main to be iden­ti­fied at the atomic scale. Here, we pre­sent re­sults of large-scale mol­e­c­u­lar dy­nam­ics sim­u­la­tions (MD) to in­ves­ti­gate pos­si­ble modes of cou­pling. We con­sider the ac­ti­va­tion of Frank-Read (FR) sources, which leads to dis­lo­ca­tion mul­ti­pli­ca­tion, under the ac­tion of bi-ax­ial ther­mal stresses and sur­face elec­tric-field. With a charge-equi­li­bra­tion for­mal­ism in­cor­po­rated in a clas­si­cal MD model, we show that a sur­face elec­tric field act­ing on an ei­ther pre­ex­ist­ing or dis­lo­ca­tion-in­duced sur­face step, can gen­er­ate a long-range re­solved shear stress field in­side the bulk of the sam­ple. We in­ves­ti­gate the feed­back be­tween step growth fol­low­ing dis­lo­ca­tion emis­sion and sub­se­quent ac­ti­va­tions of FR sources and dis­cuss the regimes of crit­i­cal length-scales and den­si­ties of dis­lo­ca­tions, where such a mech­a­nism could pro­mote RF break­down pre­cur­sors. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB362  
About • paper received ※ 19 May 2021       paper accepted ※ 10 June 2021       issue date ※ 19 August 2021  
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TUXA06 Loss of Transverse Landau Damping by Diffusion in High-Energy Hadron Colliders wakefield, damping, hadron, collider 1286
 
  • S.V. Furuseth, X. Buffat
    CERN, Geneva, Switzerland
  • S.V. Furuseth
    EPFL, Lausanne, Switzerland
  
  Cir­cu­lar hadron col­lid­ers rely on Lan­dau damp­ing to sta­bi­lize the beams. Lan­dau damp­ing de­pends strongly on the bunch dis­tri­b­u­tion, which is often as­sumed to be Gauss­ian in the trans­verse planes. In this paper, we in­tro­duce and ex­plain an in­sta­bil­ity mech­a­nism ob­served in the LHC, where Lan­dau damp­ing is even­tu­ally lost due to a dif­fu­sion that mod­i­fies the trans­verse bunch dis­tri­b­u­tion. The mech­a­nism is caused by a wide-spec­trum noise that ex­cites the trans­verse mo­tion of the beam, which con­se­quently pro­duces wake­fields that drive a nar­row-spec­trum dif­fu­sion. It is shown that this dif­fu­sion ef­fi­ciently low­ers the sta­bil­ity di­a­gram at the fre­quency of the least sta­ble co­her­ent mode, lead­ing to a loss of Lan­dau damp­ing after a la­tency. A semi-an­a­lyt­i­cal model agrees with mea­sure­ments in ded­i­cated la­tency ex­per­i­ments per­formed in the LHC. This in­sta­bil­ity mech­a­nism ex­plains the need for a sta­bil­ity mar­gin in oc­tu­pole cur­rent in the LHC, rel­a­tive to the amount needed to sta­bi­lize a Gauss­ian beam. We de­tail the im­pact of this mech­a­nism and pos­si­ble mit­i­ga­tions for the LHC and HL-LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA06  
About • paper received ※ 19 May 2021       paper accepted ※ 25 June 2021       issue date ※ 10 August 2021  
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TUPAB001 DAΦNE Commissioning for SIDDHARTA-2 Experiment luminosity, optics, collider, positron 1322
 
  • C. Milardi, D. Alesini, O.R. Blanco-García, M. Boscolo, B. Buonomo, S. Cantarella, A. D’Uffizi, A. De Santis, C. Di Giulio, G. Di Pirro, A. Drago, L.G. Foggetta, G. Franzini, A. Gallo, S. Incremona, A. Michelotti, L. Pellegrino, L. Piersanti, R. Ricci, U. Rotundo, L. Sabbatini, A. Stecchi, A. Stella, A. Vannozzi, M. Zobov
    INFN/LNF, Frascati, Italy
  • J. Chavanne, G. Le Bec, P. Raimondi
    ESRF, Grenoble, France
  
  DAΦNE, the Fras­cati lep­ton col­lider, has com­pleted the prepara­tory phase in order to de­liver lu­mi­nos­ity to the SID­DHARTA-2 de­tec­tor. DAΦNE col­lid­ing rings rely on a new in­ter­ac­tion re­gion, which im­ple­ments the well-es­tab­lished Crab-Waist col­li­sion scheme, and in­cludes a low-beta sec­tion equipped with newly de­signed per­ma­nent mag­net quadrupoles, and vac­uum com­po­nents. Di­ag­nos­tics tools have been im­proved, es­pe­cially the ones used to keep under con­trol the beam-beam in­ter­ac­tion. The hor­i­zon­tal feed­back in the positron ring has been po­ten­ti­ated in order to achieve a higher positron cur­rent. Lu­mi­nos­ity di­ag­nos­tics have been also up­dated so to be com­pat­i­ble with the new de­tec­tor de­sign. The com­mis­sion­ing was ini­tially fo­cused on re­cov­er­ing the op­ti­mal dy­nam­i­cal vac­uum con­di­tions, out­lin­ing align­ment er­rors, and op­ti­miz­ing ring op­tics. For this rea­son, a de­tuned op­tics, fea­tured by re­laxed low-b con­di­tion at the in­ter­ac­tion point and Crab-Waist Ses­tupoles off, has been ap­plied. In a sec­ond stage a low-b op­tics has been im­ple­mented to test col­li­sions with a pre­lim­i­nary setup of the ex­per­i­ment de­tec­tor. Ma­chine prepa­ra­tion and the first lu­mi­nos­ity re­sults are pre­sented and dis­cussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB001  
About • paper received ※ 19 May 2021       paper accepted ※ 09 June 2021       issue date ※ 10 August 2021  
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TUPAB019 A High-Resolution, Low-Latency, Bunch-by-Bunch Feedback System for Nano-Beam Stabilization cavity, dipole, kicker, collider 1378
 
  • R.L. Ramjiawan, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, P. Burrows, G.B. Christian, C. Perry
    JAI, Oxford, United Kingdom
  • D.R. Bett
    CERN, Geneva, Switzerland
  • N. Blaskovic Kraljevic
    ESS, Lund, Sweden
  • G.B. Christian
    DLS, Oxfordshire, United Kingdom
  
  A low-la­tency, bunch-by-bunch feed­back sys­tem em­ploy­ing high-res­o­lu­tion cav­ity Beam Po­si­tion Mon­i­tors (BPMs) has been de­vel­oped and tested at the Ac­cel­er­a­tor Test Fa­cil­ity (ATF2) at the High En­ergy Ac­cel­er­a­tor Re­search Or­ga­ni­za­tion (KEK), Japan. The feed­back sys­tem was de­signed to demon­strate nanome­ter-level ver­ti­cal sta­bi­liza­tion at the focal point of the ATF2 and can be op­er­ated using ei­ther a sin­gle BPM to pro­vide local beam sta­bi­liza­tion, or by using two BPMs to sta­bi­lize the beam at an in­ter­me­di­ate lo­ca­tion. The feed­back cor­rec­tion is im­ple­mented using a stripline kicker and the feed­back cal­cu­la­tions are per­formed on a dig­i­tal board con­structed around a Field Pro­gram­ma­ble Gate Array (FPGA). The feed­back per­for­mance was tested with trains of two bunches, sep­a­rated by 280ns, at a charge of ~1nC, where the ver­ti­cal off­set of the first bunch was mea­sured and used to cal­cu­late the cor­rec­tion to be ap­plied to the sec­ond bunch. The BPMs have been demon­strated to achieve an op­er­a­tional res­o­lu­tion of ~20nm. With the ap­pli­ca­tion of sin­gle-BPM and two-BPM feed­back, beam sta­bi­liza­tion of below 50nm and 41nm re­spec­tively has been achieved with a la­tency of 232ns.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB019  
About • paper received ※ 18 May 2021       paper accepted ※ 09 June 2021       issue date ※ 14 August 2021  
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TUPAB020 A Sub-Micron Resolution, Bunch-by-Bunch Beam Trajectory Feedback System and Its Application to Reducing Wakefield Effects in Single-Pass Beamlines wakefield, electron, cavity, kicker 1382
 
  • D.R. Bett, P. Burrows, C. Perry, R.L. Ramjiawan
    JAI, Oxford, United Kingdom
  • D.R. Bett
    CERN, Geneva, Switzerland
  • K. Kubo, T. Okugi, N. Terunuma
    KEK, Ibaraki, Japan
  
  A high-pre­ci­sion in­tra-bunch-train beam orbit feed­back cor­rec­tion sys­tem has been de­vel­oped and tested at the KEK Ac­cel­er­a­tor Test Fa­cil­ity, ATF2. The sys­tem uses the ver­ti­cal po­si­tion of the bunch mea­sured at two beam po­si­tion mon­i­tors to cal­cu­late a pair of kicks which are ap­plied to the next bunch using two up­stream kick­ers, thereby cor­rect­ing both the ver­ti­cal po­si­tion and tra­jec­tory angle. Using trains of two elec­tron bunches sep­a­rated in time by 187.6ns, the sys­tem was op­ti­mised so as to sta­bi­lize the beam off­set at the feed­back BPMs to bet­ter than 350nm, yield­ing a local tra­jec­tory angle cor­rec­tion to within 250n­rad. The qual­ity of the cor­rec­tion was ver­i­fied using three down­stream wit­ness BPMs and the re­sults were found to be in agree­ment with the pre­dic­tions of a lin­ear lat­tice model used to prop­a­gate the beam tra­jec­tory from the feed­back re­gion. This same model pre­dicts a cor­rected be am jit­ter of c.1nm at the focal point of the ac­cel­er­a­tor. Mea­sure­ments with a beam size mon­i­tor at this lo­ca­tion demon­strate that re­duc­ing the tra­jec­tory jit­ter of the beam by a fac­tor of 4 also re­duces the in­crease in the mea­sured beam size as a func­tion of beam charge by a fac­tor of ~1.6.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB020  
About • paper received ※ 13 May 2021       paper accepted ※ 01 July 2021       issue date ※ 11 August 2021  
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TUPAB083 Dual Energies in the LCLS Copper Linac linac, quadrupole, klystron, betatron 1570
 
  • F.-J. Decker, C. Bianchini Mattison, D.K. Bohler, A. Brachmann, W.S. Colocho, S. Condamoor, M.L. Gibbs, K.H. Kim, A.A. Lutman, T.J. Maxwell, J.A. Mock, H.-D. Nuhn, J.C. Sheppard, H. Smith, T.J. Smith, M. Stanek, S. Zelazny, Z. Zhang, C.M. Zimmer
    SLAC, Menlo Park, California, USA
  
  For LCLS-II two un­du­la­tors were in­stalled at SLAC, one for soft and one for hard x-rays. Be­fore the su­per­con­duct­ing linac gets turned on the cop­per linac is pro­vid­ing beams at 120 Hz to these two beam des­ti­na­tions. The 120 Hz can be split in many dif­fer­ent ra­tios be­tween soft and hard via a pulsed mag­net. To get an op­ti­mized beam for the quite dif­fer­ent pho­ton en­er­gies the pulsed linac com­po­nents like mod­u­la­tors and RF can pro­vide many dif­fer­ent beam pa­ra­me­ters, mainly en­er­gies and bunch lengths for the two un­du­la­tor lines. How this was im­ple­mented with tim­ing se­tups of trig­gers and fi­nally after the split the nec­es­sary match­ing of the trans­verse phase space will be dis­cussed.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB083  
About • paper received ※ 19 May 2021       paper accepted ※ 27 May 2021       issue date ※ 21 August 2021  
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TUPAB254 Limiting Coherent Longitudinal Beam Oscillations in the EIC Electron Storage Ring electron, cavity, emittance, hadron 2046
 
  • B. Podobedov
    Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
  • M. Blaskiewicz
    BNL, Upton, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
We study co­her­ent lon­gi­tu­di­nal beam os­cil­la­tions in the EIC elec­tron stor­age ring (ESR). We show that to avoid un­ac­cept­able hadron emit­tance growth due to fi­nite cross­ing angle, the am­pli­tude of these os­cil­la­tions needs to be lim­ited to a frac­tion of a mil­lime­ter. Using an an­a­lyt­i­cal model we es­ti­mate the am­pli­tude of these os­cil­la­tions under the two sce­nar­ios: 1) the beam is pas­sively sta­ble and the os­cil­la­tions are dri­ven by RF phase noise only; 2) a cou­pled-bunch in­sta­bil­ity, presently ex­pected in the ESR, is damped by a lon­gi­tu­di­nal feed­back sys­tem. We show that, for the 2nd sce­nario, com­fort­able spec­i­fi­ca­tions for RF phase noise and feed­back sen­sor noise will be suf­fi­cient to main­tain the os­cil­la­tion am­pli­tude within the re­quired lim­its. 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB254  
About • paper received ※ 12 May 2021       paper accepted ※ 18 June 2021       issue date ※ 26 August 2021  
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TUPAB263 The Phase Loop Status of the RF System in CSNS/RCS proton, cavity, space-charge, MMI 2076
 
  • L. Huang, X. Li, S. Wang
    IHEP, Beijing, People’s Republic of China
  • M.T. Li, H.Y. Liu
    IHEP CSNS, Guangdong Province, People’s Republic of China
  • Y. Liu
    DNSC, Dongguan, People’s Republic of China
  
  The Rapid Cy­cling Syn­chro­tron (RCS) of the China Spal­la­tion Neu­tron Source (CSNS) is a high in­ten­sity pro­ton ac­cel­er­a­tor. The ac­cel­er­a­tion sys­tem con­sists of eight fer­rite loaded cav­i­ties. The RCS is the space charge dom­i­nant ma­chine and it is mit­i­gated through the bunch fac­tor op­ti­miza­tion in the beam com­mis­sion­ing, so the in­jected beam will oc­cupy a larger bucket size and un­avoid­able mis­match with the bucket, thus the di­pole os­cil­la­tion is ex­cited. The phase loop scheme is de­signed to re­strict the os­cil­la­tion in the RF sys­tem, but the trans­mis­sion ef­fi­ciency is re­duced by the phase loop and the bunch fac­tor also in­creases, so the phase loop scheme is stud­ied. To keep the phase loop but also main­tain the trans­mis­sion ef­fi­ciency, we op­ti­mized the orig­i­nal phase loop scheme, but the beam loss still in­creases small when the loop on.  
poster icon Poster TUPAB263 [1.548 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB263  
About • paper received ※ 13 May 2021       paper accepted ※ 02 June 2021       issue date ※ 21 August 2021  
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TUPAB302 Arrival Time Stabilization at Flash Using the Bunch Arrival Corrector Cavity (BACCA) cavity, electron, laser, SRF 2194
 
  • B. Lautenschlager, L. Butkowski, M.K. Czwalinna, B. Dursun, M. Hierholzer, S. Pfeiffer, H. Schlarb, Ch. Schmidt
    DESY, Hamburg, Germany
  
  For pump-probe and seed­ing ex­per­i­ments at free elec­tron lasers, a fem­tosec­ond pre­cise bunch ar­rival time sta­bil­ity is manda­tory. To sta­bi­lize the ar­rival times a fast lon­gi­tu­di­nal intra bunch-train feed­back (L-IBFB) using bunch ar­rival time mon­i­tors is ap­plied. The elec­tron bunch en­ergy prior to a bunch com­pres­sion chi­cane is mod­u­lated by su­per­con­duct­ing radio fre­quency (SRF) cav­i­ties to com­pen­sate fast ar­rival time fluc­tu­a­tions of the sub­se­quent bunches. A broad­band nor­mal con­duct­ing RF cav­ity was in­stalled in front of the first bunch com­pres­sion chi­cane at FLASH. The L-IBFB uses the nor­mal con­duct­ing cav­ity for small but fast en­ergy cor­rec­tions to­gether with the SRF cav­i­ties for larger and slower cor­rec­tions. Cur­rent mea­sure­ments show ar­rival time sta­bil­i­ties of the elec­tron bunches to­wards 5 fs (rms) at the end of the linac, if the nor­mal con­duct­ing cav­ity acts to­gether with the SRF cav­i­ties in the L-IBFB sys­tem.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB302  
About • paper received ※ 19 May 2021       paper accepted ※ 23 June 2021       issue date ※ 26 August 2021  
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TUPAB306 Status of Beam-Based Feedback Research and Development for Continuous Wave SRF Linac ELBE controls, electron, cavity, LLRF 2200
 
  • A. Maalberg, M. Kuntzsch
    HZDR, Dresden, Germany
  • E. Petlenkov
    TalTech, Tallinn, Estonia
  
  The su­per­con­duct­ing elec­tron lin­ear ac­cel­er­a­tor ELBE at Helmholtz-Zen­trum Dres­den-Rossendorf is a ver­sa­tile light source op­er­ated in con­tin­u­ous wave mode. As the de­mand on the beam sta­bil­ity in­creases, the im­prove­ment of the beam con­trol schemes cur­rently in­stalled at ELBE be­comes highly rel­e­vant. This im­prove­ment can be achieved by an up­grade of the ex­ist­ing dig­i­tal Mi­croTCA.4-based LLRF con­trol scheme by beam-based feed­back. By pre­sent­ing both the de­sign and im­ple­men­ta­tion de­tails of the new con­trol scheme this con­tri­bu­tion re­ports the sta­tus of the work in progress.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB306  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 30 August 2021  
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WEPAB117 Injection Feedback for a Storage Ring injection, HOM, kicker, simulation 2870
 
  • A. Moutardier, C. Bruni, I. Chaikovska, S. Chancé, N. Delerue, E.E. Ergenlik, V. Kubytskyi, H. Monard
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  
  Funding: Research Agency under the Equipex convention ANR-10-EQPX-0051.
We re­port on an in­jec­tion feed­back scheme for the ThomX stor­age ring pro­ject. ThomX is a 50-MeV-elec­tron ac­cel­er­a­tor pro­to­type which will use Comp­ton backscat­ter­ing in a stor­age ring to gen­er­ate a high flux of hard X-rays. Given the slow beam damp­ing (in the ring), the in­jec­tion must be per­formed with high ac­cu­racy to avoid large be­ta­tron os­cil­la­tions. A home­made an­a­lytic code is used to com­pute the cor­rec­tions that need to be ap­plied be­fore the beam in­jec­tion to achieve a beam po­si­tion ac­cu­racy of a few hun­dred mi­crom­e­ters in the first beam po­si­tion mon­i­tors (BPMs). In order to do so the code needs the in­for­ma­tion pro­vided by the ring’s di­ag­nos­tic de­vices. The it­er­a­tive feed­back sys­tem has been tested using MadX sim­u­la­tions. Our sim­u­la­tions show that a per­for­mance that matches the BPMs’ ac­cu­racy can be achieved in less than 50 it­er­a­tions in all cases. De­tails of this feed­back al­go­rithm, its ef­fi­ciency and the sim­u­la­tions are dis­cussed. 		 
poster icon Poster WEPAB117 [2.422 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB117  
About • paper received ※ 28 May 2021       paper accepted ※ 01 July 2021       issue date ※ 25 August 2021  
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WEPAB123 Multi-Bunch Resistive Wall Wake Field Tracking via Pseudomodes in the ALS-U Accumulator Ring injection, damping, simulation, kicker 2893
 
  • M.P. Ehrlichman, S. De Santis, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, D. Wang
    LBNL, Berkeley, USA
  
  For the ALS-U pro­ject, par­ti­cles will be in­jected from the booster to the ac­cu­mu­la­tor ring uti­liz­ing an in­jec­tion scheme that leaves the stored and in­jected par­ti­cles with a non-triv­ial tran­sient. This tran­sient re­quires that multi­bunch feed­back be masked for those buck­ets into which charge is in­jected. The mask­ing sig­nif­i­cantly di­min­ishes the damp­ing ca­pa­bil­ity of the multi­bunch feed­back sys­tem. This prob­lem is ex­ac­er­bated by the large in­jec­tion tran­sient. The higher order re­sis­tive wall wake fields in the ac­cu­mu­la­tor ring ex­ceed the ra­di­a­tion damp­ing time. To study whether the beam will re­main multi­bunch sta­ble dur­ing an in­jec­tion cycle, a multi­bunch track­ing sim­u­la­tion is used that sim­u­lates the multi­bunch feed­back sys­tem and also pseudo­mode rep­re­sen­ta­tion of re­sis­tive wall wake fields.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB123  
About • paper received ※ 20 May 2021       paper accepted ※ 01 September 2021       issue date ※ 23 August 2021  
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WEPAB134 Experimental Studies of the In-Vacuum-Cryogenic Undulator Effect on Beam Instabilities at BESSY II undulator, vacuum, damping, impedance 2929
 
  • M. Huck, J. Bahrdt, A. Meseck, G. Rehm, M. Ries, A. Schälicke
    HZB, Berlin, Germany
  
  A new in-vac­uum cryo­genic per­ma­nent mag­net un­du­la­tor (CP­MU17) has been in­stalled in sum­mer 2018 in the BESSY II stor­age ring at HZB. Such a small gap in-vac­uum un­du­la­tor de­vice in­creases the im­ped­ance of the stor­age ring and can con­tribute to the in­sta­bil­i­ties that ad­versely af­fect the beam qual­ity and the de­vice it­self. To iden­tify and ex­plore the ef­fects of CP­MU17 on the in­sta­bil­i­ties at BESSY II, grow-damp and drive-damp ex­per­i­ments have been con­ducted using the in­stalled bunch-by-bunch feed­back sys­tem. In this paper, the first re­sults of the mode and gap analy­sis of these stud­ies with a brief overview of other im­ped­ance stud­ies will be pre­sented.  
poster icon Poster WEPAB134 [1.079 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB134  
About • paper received ※ 17 May 2021       paper accepted ※ 02 July 2021       issue date ※ 23 August 2021  
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WEPAB239 Effect of Chromaticity and Feedback on Transverse Head-Tail Instability impedance, coupling, damping, storage-ring 3189
 
  • V.V. Smaluk, G. Bassi, A. Blednykh, A. Khan
    BNL, Upton, New York, USA
  
  Funding: This work was supported by the US Department of Energy under contract DE-SC0012704.
The head-tail in­sta­bil­ity caused by the beam in­ter­ac­tion with short-range wake­fields is a major lim­i­ta­tion for the sin­gle-bunch beam in­ten­sity in cir­cu­lar ac­cel­er­a­tors. The com­bined ef­fect of the trans­verse feed­back sys­tems and chro­matic­ity sup­press­ing the in­sta­bil­ity is dis­cussed. The­o­ret­i­cal and ex­per­i­men­tal stud­ies of the head-tail in­sta­bil­ity and meth­ods of its mit­i­ga­tion are re­viewed. Re­sults of ex­per­i­men­tal stud­ies of the trans­verse mode cou­pling car­ried out at NSLS-II are com­pared with the the­o­ret­i­cal model and nu­mer­i­cal sim­u­la­tions. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB239  
About • paper received ※ 19 May 2021       paper accepted ※ 24 June 2021       issue date ※ 12 August 2021  
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WEPAB290 Pointing Stabilization Algorithms Explored and Implemented with the Low Energy RHIC Electron Cooling Laser laser, operation, electron, cathode 3336
 
  • L.K. Nguyen
    BNL, Upton, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The elec­tron beam for the Low En­ergy RHIC elec­tron Cooler (LEReC) at Brookhaven Na­tional Lab­o­ra­tory (BNL) is gen­er­ated by a high-power fiber laser il­lu­mi­nat­ing a pho­to­cath­ode, with a total prop­a­ga­tion dis­tance of 34 m sep­a­rat­ing the laser out­put and the pho­to­cath­ode. This prop­a­ga­tion is fa­cil­i­tated by three in­de­pen­dent laser ta­bles that have vary­ing re­sponses to changes in time of day, weather, and sea­son. Align­ment drifts in­duced by these en­vi­ron­men­tal changes are mit­i­gated by an ac­tive "slow" point­ing sta­bi­liza­tion sys­tem found along the length of the trans­port, and this in-house sys­tem was com­mis­sioned as part of the full laser trans­port in 2019, as pre­vi­ously re­ported*. In 2020, the sys­tem be­came fully op­er­a­tional along­side LEReC, the world’s first elec­tron cooler in a col­lider, and helped es­tab­lish the trans­verse sta­bil­ity of the elec­tron beam re­quired for cool­ing. A sum­mary of the dif­fer­ent slow sta­bi­liza­tion al­go­rithms, which were con­tin­u­ally re­fined dur­ing the run in order to achieve long-term cen­ter-of-mass sta­bil­ity of the laser spot on the pho­to­cath­ode to within 10 mi­crons RMS, is pro­vided.
* L. K. Nguyen et al., "Active Pointing Stabilization Techniques Applied to the Low Energy RHIC Electron Cooling Laser Transport at BNL", presented at NAPAC’19, paper THYBA6. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB290  
About • paper received ※ 19 May 2021       paper accepted ※ 02 July 2021       issue date ※ 24 August 2021  
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WEPAB330 A Multirange Low Noise Transimpedance Amplifier for Sirius Beamlines impedance, operation, FEM, synchrotron 3447
 
  • L.Y. Tanio, F.H. Cardoso, M.M. Donatti
    LNLS, Campinas, Brazil
  
  In a typ­i­cal syn­chro­tron beam­line, the in­ter­ac­tion of pho­ton beams with dif­fer­ent ma­te­ri­als gen­er­ates free elec­tric charges in de­vices such as ion­iza­tion cham­bers, pho­to­di­odes, or even iso­lated metal­lic struc­tures (e.g., blades, blocks, foils, wires). These free charges can be mea­sured as elec­tric cur­rent to di­ag­nose the pho­ton beam in­ten­sity, pro­file, po­si­tion, or sta­bil­ity. Sir­ius, the new 3GeV fourth-gen­er­a­tion Brazil­ian light source, may ac­com­mo­date up to 38 beam­lines, which com­bined will make use of hun­dreds of in­stru­ments to mea­sure such low-in­ten­sity sig­nals. This work re­ports on the de­sign and test re­sults of a tran­sim­ped­ance am­pli­fier de­vel­oped for low cur­rent mea­sure­ments at Sir­ius’ beam­lines. The de­vice pre­sents low noise, high ac­cu­racy, and good tem­per­a­ture sta­bil­ity pro­vid­ing 5 se­lec­table ranges (from 500pA to 7.3mA) to mea­sure bipo­lar cur­rents achiev­ing fem­toam­pere res­o­lu­tion under cer­tain con­di­tions. Con­sid­er­ing low band­width ap­pli­ca­tions, the re­sults sug­gest noise per­for­mance com­pa­ra­ble to com­mer­cial bench in­stru­ments. Ad­di­tion­ally, the pro­ject de­f­i­n­i­tions and plans for the de­vel­op­ment of a fam­ily of low cur­rent am­me­ters will be dis­cussed.  
poster icon Poster WEPAB330 [2.642 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB330  
About • paper received ※ 19 May 2021       paper accepted ※ 16 June 2021       issue date ※ 21 August 2021  
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THXB02 Beam Arrival Stability at the European XFEL FEL, laser, timing, electron 3714
 
  • M.K. Czwalinna, J. Kral, B. Lautenschlager, J. Müller, H. Schlarb, S. Schulz, B. Steffen
    DESY, Hamburg, Germany
  • R. Boll, H. Kirkwood, J. Koliyadu, R. Letrun, J. Liu, F. Pallas, D.E. Rivas, T. Sato
    EuXFEL, Schenefeld, Germany
  
  Free elec­tron laser fa­cil­i­ties, such as the Eu­ro­pean XFEL, make in­creas­ingly high de­mands on the longterm tem­po­ral sta­bil­ity and uni­for­mity of the elec­tron bunches, as pump-probe ex­per­i­ments mean­while aim for tim­ing sta­bil­i­ties of few fem­tosec­onds resid­ual jit­ter only. For a beam-based feed­back con­trol of the lin­ear ac­cel­er­a­tor, elec­tro-op­ti­cal bunch ar­rival-time mon­i­tors are de­ployed, achiev­ing a time res­o­lu­tion bet­ter than 3 fs. In a first at­tempt, we re­cently demon­strated a beam-based feed­back sys­tem, re­duc­ing the ar­rival time jit­ter of the elec­tron bunches to the 10 fs level with sta­ble op­er­a­tion over hours. For pump-probe ex­per­i­ments it is cru­cial to equally ver­ify this new level of pre­ci­sion in the FEL pulse ar­rival time with in­de­pen­dent meth­ods. In this work, we are dis­cussing first re­sults from ex­am­in­ing the fa­cil­ity-wide tem­po­ral sta­bil­ity at the Eu­ro­pean XFEL, with at­ten­tion to the con­tri­bu­tions of var­i­ous sub-sys­tems and on the dif­fer­ent time scales.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB02  
About • paper received ※ 19 May 2021       paper accepted ※ 20 July 2021       issue date ※ 23 August 2021  
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THPAB063 Laser Transport System of Shanghai Laser Electron Gamma Source (SLEGS) laser, detector, controls, scattering 3897
 
  • H.H. Xu, G.T. Fan
    SSRF, Shanghai, People’s Republic of China
  
  Shang­hai Laser Elec­tron Gamma Source (SLEGS) *, based on laser Comp­ton scat­ter­ing (LCS), as one of beam­lines of Shang­hai Syn­chro­tron Ra­di­a­tion Fa­cil­ity (SSRF) in phase II, is under con­struc­tion now. The tech­ni­cal de­sign of its laser in­jec­tion sys­tem has been im­ple­mented and op­ti­mized con­sec­u­tively over the last few years. In order to in­ject the 10640 nm CO2 laser into the in­ter­ac­tion point from the laser hutch out­side the stor­age ring’s shield­ing, a laser trans­port sys­tem longer than 20 m using re­lay-imag­ing tele­scopes is de­signed. There are two op­er­a­tion mode in SLEGS. One is backscat­ter­ing mode, which will make the laser and elec­tron bunch col­lide at 180° with flux higher than 107 gamma/s. The other mode is slant­ing mode, which mainly in­her­its the de­sign used in the pro­to­type**. In this paper, a brief sum­mary of the laser trans­port sys­tem is given. The sys­tem con­tains sev­eral mod­ules to per­form beam ex­pan­sion, com­bin­ing, mon­i­tor­ing and real-time ad­just­ment. The de­sign mod­els, sim­u­la­tion study of the laser qual­ity through the trans­porta-tion, and the ex­per­i­men­tal re­sults are pre­sented.
* Y. Xu, W. Xu, et al., NIM A, 578, 457 (2007).
** H.H. Xu, J.H. Chen, et al., Transaction on Nuclear Science, IEEE, 63, 906 (2016). 		 
poster icon Poster THPAB063 [2.508 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB063  
About • paper received ※ 19 May 2021       paper accepted ※ 24 June 2021       issue date ※ 27 August 2021  
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THPAB257 Fast Orbit Corrector Power Supply in MTCA.4 Form Factor for Sirius Light Source controls, power-supply, hardware, target 4307
 
  • A.F. Giachero, G.B.M. Bruno, L.M. Russo, D.O. Tavares
    LNLS, Campinas, Brazil
  
  A new fast orbit feed­back (FOFB) hard­ware ar­chi­tec­ture has been pur­sued at Sir­ius. The fast cor­rec­tor mag­nets’ are fed by power sup­ply mod­ules which are placed in the same Mi­croTCA.4 crates where the BPM dig­i­tiz­ers and FOFB con­trollers are lo­cated. Each chan­nel is made of a 3-Watt lin­ear am­pli­fier whose out­put cur­rents are dig­i­tally con­trolled by the same FPGA where the dis­trib­uted orbit feed­back con­troller is processed. The am­pli­fier is spec­i­fied to reach up to 10 kHz small-sig­nal band­width on a 3.5 mH in­duc­tance mag­net and ±1 A full scale, which trans­lates to 30 urad de­flec­tion on Sir­ius’ 3 GeV beam. Such a high level of in­te­gra­tion aims at min­i­miz­ing the over­all la­tency of the FOFB loop while lever­ag­ing the crate in­fra­struc­ture, namely elec­tron­ics en­clo­sure, DC power, cool­ing, and hard­ware man­age­ment sup­port al­ready pro­vided by the MTCA.4 crates. The fast cor­rec­tor power sup­ply chan­nels are placed on Rear Tran­si­tion Mod­ules (RTMs) which are at­tached to the front AMC FPGA mod­ule where the FOFB con­troller is im­ple­mented. This paper will de­scribe the main de­sign con­cepts and re­port on the ex­per­i­men­tal re­sults of the first pro­to­types.  
poster icon Poster THPAB257 [48.881 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB257  
About • paper received ※ 22 May 2021       paper accepted ※ 27 July 2021       issue date ※ 20 August 2021  
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THPAB258 Status of Time-Domain Simulation for the Fast Orbit Feedback System at the HEPS simulation, vacuum, power-supply, emittance 4311
 
  • Y. Wei, Z. Duan, X.Y. Huang, Y. Jiao
    IHEP, Beijing, People’s Republic of China
  
  High En­ergy Pho­ton Source (HEPS) is a com­plex de­signed at ul­tra-low emit­tance. A fast orbit feed­back sys­tem is pro­posed to meet the re­quire­ment of beam orbit sta­bil­ity at the sub-mi­cron level. In this paper, we pre­sent our work on set­ting up an orbit feed­back process com­bined with noise model, sys­tem mod­el­ing, and par­ti­cle track­ing in the time do­main. RF phase pa­ra­me­ter is ad­justed to­gether with fast cor­rec­tors to mit­i­gate the orbit fluc­tu­a­tion due to en­ergy vi­bra­tion. The pre­lim­i­nary re­sults are shown here. By the fol­low­ing op­ti­miza­tion, we hope to pro­vide an ef­fec­tive tool to spec­ify and con­fig­ure the FOFB sys­tem with the sim­u­la­tion.  
poster icon Poster THPAB258 [1.334 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB258  
About • paper received ※ 19 May 2021       paper accepted ※ 27 July 2021       issue date ※ 31 August 2021  
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THPAB309 New Working Tune Feedback System for TLS quadrupole, insertion, insertion-device, radiation 4394
 
  • S.J. Huang, Y.K. Lin, Y.C. Lin
    NSRRC, Hsinchu, Taiwan
  
  TLS stor­age ring has two sets of work­ing tun­ing feed­back sys­tems: one is used to cor­rect the work­ing tune de­vi­a­tion caused by in­ser­tion de­vice U90; an­other sys­tem uses a local trim coil to cor­rect the work­ing tune de­vi­a­tion caused by all in­ser­tion de­vices. This ar­ti­cle de­scribes a new work­ing tune feed­back sys­tem in TLS that can cor­rect the work­ing tune ef­fec­tively back to the re­quired con­di­tions for op­er­a­tion; the two ex­ist­ing feed­back sys­tems do not cause prob­lems. We can both avoid in­creas­ing the local ra­di­a­tion dose and de­creas­ing the in­jec­tion ef­fi­ciency.  
poster icon Poster THPAB309 [0.831 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB309  
About • paper received ※ 15 May 2021       paper accepted ※ 02 July 2021       issue date ※ 23 August 2021  
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THPAB311 Using Linear Regression to Model the Parameters of the Flat Wires in TLS-EPU56 injection, undulator, hardware, electron 4399
 
  • S.J. Huang, Y.H. Chang, T.Y. Chung
    NSRRC, Hsinchu, Taiwan
  • Y.W. Chen
    Academia Sinica, Taipei, Taiwan
  
  Al­though a the­o­ret­i­cal cal­cu­la­tion might pre­dict the set cur­rents of the flat wires, which are used to com­pen­sate the de­vi­a­tion in the Be­ta­tron tune caused by the el­lip­ti­cally po­lar­ized un­du­la­tor (EPU), those set cur­rents must still be tuned in re­al­ity. To ap­proach this re­al­ity, a strat­egy of Ma­chine Learn­ing was adopted, which in­cluded col­lect­ing real-con­di­tion data and using a lin­ear-re­gres­sion model to ad­just the pa­ra­me­ters of the flat wires. After train­ing the model, the pre­dic­tions in vari­ables tune x, tune y and beam size x were com­pared with the re­quired amount of cor­rec­tion of the EPU at var­i­ous gaps and phases. To prove the fea­si­bil­ity of this method, a test was per­formed under the real con­di­tions of ac­cel­er­a­tor Tai­wan Light Source (TLS).  
poster icon Poster THPAB311 [1.226 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB311  
About • paper received ※ 13 May 2021       paper accepted ※ 28 June 2021       issue date ※ 30 August 2021  
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THPAB337 Resonance Control System for the PIP-II IT HWR Cryomodule cavity, controls, cryomodule, resonance 4446
 
  • P. Varghese, B.E. Chase, P.M. Hanlet, H. Maniar, D.J. Nicklaus, S. Sankar Raman
    Fermilab, Batavia, Illinois, USA
  • L.R. Doolittle, S. Paiagua, C. Serrano
    LBNL, Berkeley, California, USA
  
  The HWR (half-wave-res­onator) cry­omod­ule is the first one in the su­per­con­duct­ing sec­tion of the PIP-II LINAC pro­ject at Fer­mi­lab. PIP-II IT is a test fa­cil­ity for the pro­ject where the in­jec­tor, warm front-end, and the first two su­per­con­duct­ing cry­omod­ules are being tested. The HWR cry­omod­ule com­prises 8 cav­i­ties op­er­at­ing at a fre­quency of 162.5 MHz and ac­cel­er­at­ing beam up to 10 MeV. Res­o­nance con­trol of the cav­i­ties is per­formed with a pneu­mat­i­cally op­er­ated slow tuner which com­presses the cav­ity at the beam ports. He­lium gas pres­sure in a bel­lows mounted to an end wall of the cav­ity is con­trolled by two so­le­noid valves, one on the pres­sure side and one on the vac­uum side. The res­o­nant fre­quency of the cav­ity can be con­trolled in one of two modes. A pres­sure feed­back con­trol loop can hold the cav­ity tuner pres­sure at a fixed value for the de­sired res­o­nant fre­quency. Al­ter­nately, the feed­back loop can reg­u­late the cav­ity tuner pres­sure to bring the RF de­tun­ing error to zero. The res­o­nance con­troller is in­te­grated into the LLRF con­trol sys­tem for the cry­omod­ule. The con­trol sys­tem de­sign and per­for­mance of the res­o­nance con­trol sys­tem are de­scribed in this paper.  
poster icon Poster THPAB337 [4.426 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB337  
About • paper received ※ 12 May 2021       paper accepted ※ 26 July 2021       issue date ※ 27 August 2021  
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