• M.A. Palmer, J.P. Alexander, M.G. Billing, J.R. Calvey, C.J. Conolly, J.A. Crittenden, J. Dobbins, G. Dugan, N. Eggert, E. Fontes, M.J. Forster, R.E. Gallagher, S.W. Gray, S. Greenwald, D.L. Hartill, W.H. Hopkins, D.L. Kreinick, B. Kreis, Z. Leong, Y. Li, X. Liu, J.A. Livezey, A. Lyndaker, J. Makita, M.P. McDonald, V. Medjidzade, R.E. Meller, T.I. O'Connell, S.B. Peck, D.P. Peterson, G. Ramirez, M.C. Rendina, P. Revesz, D.H. Rice, N.T. Rider, D. L. Rubin, D. Sagan, J.J. Savino, R.M. Schwartz, R.D. Seeley, J.W. Sexton, J.P. Shanks, J.P. Sikora, E.N. Smith, C.R. Strohman, H.A. Williams
  CLASSE, Ithaca, New York
• F. Antoniou, S. Calatroni, M. Gasior, O.R. Jones, Y. Papaphilippou, J. Pfingstner, G. Rumolo, H. Schmickler, M. Taborelli
  CERN, Geneva
• D. Asner
  Carleton University, College of Natural Sciences, Ottawa, Ontario
• L. Boon, A.F. Garfinkel
  Purdue University, West Lafayette, Indiana
• J.M. Byrd, C.M. Celata, J.N. Corlett, S. De Santis, M.A. Furman, A. Jackson, R. Kraft, D.V. Munson, G. Penn, D.W. Plate, M. Venturini
  LBNL, Berkeley, California
• B.T. Carlson
  Grove City College, Grove City, Pennsylvania
• T. Demma
  INFN/LNF, Frascati (Roma)
• R.T. Dowd
  ASCo, Clayton, Victoria
• J.W. Flanagan, P. Jain, K. Kanazawa, K. Kubo, K. Ohmi, H. Sakai, K. Shibata, Y. Suetsugu, M. Tobiyama
  KEK, Ibaraki
• D. Gonnella
  Clarkson University, Potsdam, New York
• W. Guo
  BNL, Upton, Long Island, New York
• K.C. Harkay
  ANL, Argonne
• R. Holtzapple
  CalPoly, San Luis Obispo, CA
• J.K. Jones, A. Wolski
  Cockcroft Institute, Warrington, Cheshire
• D. Kharakh, J.S.T. Ng, M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California
• M.C. Ross, C.-Y. Tan, R.M. Zwaska
  Fermilab, Batavia
• L. Schächter
  Technion, Haifa
• E.L. Wilkinson
  Loyola University, Chicago, Illinois

The Cor­nell Elec­tron Stor­age Ring (CESR) has been re­con­fig­ured as a test ac­cel­er­a­tor (Ces­r­TA) for a pro­gram of elec­tron cloud (EC) re­search at ultra low emit­tance. The in­stru­men­ta­tion in the ring has been up­grad­ed with local di­ag­nos­tics for mea­sure­ment of cloud den­si­ty and with im­proved beam di­ag­nos­tics for the char­ac­ter­i­za­tion of both the low emit­tance per­for­mance and the beam dy­nam­ics of high in­ten­si­ty bunch trains in­ter­act­ing with the cloud. Fi­nal­ly a range of EC mit­i­ga­tion meth­ods have been de­ployed and test­ed. Mea­sure­ments of cloud den­si­ty and its im­pact on the beam under a range of con­di­tions will be pre­sent­ed and com­pared with sim­u­la­tions. The ef­fec­tive­ness of a range of mit­i­ga­tion tech­niques will also be dis­cussed.

Slides

• O.B. Malyshev
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• N.A. Collomb, J.M. Lucas, S. Postlethwaite
  STFC/DL, Daresbury, Warrington, Cheshire
• M. Korostelev
  The University of Liverpool, Liverpool
• A. Wolski
  Cockcroft Institute, Warrington, Cheshire
• K. Zolotarev
  BINP SB RAS, Novosibirsk

A vac­u­um ves­sel de­sign of wig­gler sec­tions should meet a few chal­leng­ing spec­i­fi­ca­tion. The SR power of about 40 kW is gen­er­at­ed in each wig­gler. Ex­pand­ing fan of SR ra­di­a­tion reach­es the beam vac­u­um cham­ber walls in the fol­low­ing wig­gler and may cause the fol­low­ing prob­lem: mas­sive power dis­si­pa­tion on vac­u­um cham­ber walls in­side the cryo­genic ves­sel, ra­di­a­tion dam­age of su­per­con­duct­ing coil, high pho­to-elec­tron pro­duc­tion rate that cause an e-cloud build-up to un­ac­cept­able level. There­fore this power should be ab­sorbed in the places where these ef­fects are tol­er­a­ble or man­age­able. A few pos­si­ble so­lu­tions for tack­ling all SR re­lat­ed prob­lems as well as vac­u­um de­sign are dis­cussed in the paper in de­tails.

• O.B. Malyshev
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• N.A. Collomb, J.M. Lucas, S. Postlethwaite
  STFC/DL, Daresbury, Warrington, Cheshire
• M. Korostelev
  The University of Liverpool, Liverpool
• A. Wolski
  Cockcroft Institute, Warrington, Cheshire
• K. Zolotarev
  BINP SB RAS, Novosibirsk

A 374-m long wig­gler sec­tion is a key part of ILC damp­ing ring that should alloy reach­ing a low beam emit­tance for the ILC ex­per­i­ment. Syn­chrotron ra­di­a­tion gen­er­at­ed by the beam in the wig­glers should be ab­sorbed by dif­fer­ent com­po­nents of vac­u­um ves­sel, in­clud­ing spe­cial­ly de­signed ab­sorbers. The op­ti­mi­sa­tion of the me­chan­i­cal de­sign, vac­u­um sys­tem and an­ti-e-cloud mit­i­ga­tion re­quires ac­cu­rate cal­cu­la­tion of the SR power dis­tri­bu­tion. The an­gu­lar power dis­tri­bu­tion from a sin­gle wig­gler was cal­cu­lat­ed with in-house de­vel­oped soft­ware. Then the su­per­po­si­tion of SR from all wig­glers al­lows cal­cu­lat­ing power dis­tri­bu­tion for all com­po­nents along the wig­gler sec­tion and the down­stream straight sec­tion.

• M. Korostelev, O.B. Malyshev, A. Wolski
  Cockcroft Institute, Warrington, Cheshire
• N.A. Collomb, J.M. Lucas, S. Postlethwaite
  STFC/DL, Daresbury, Warrington, Cheshire
• A.J.P. Thorley
  The University of Liverpool, Liverpool

The lon­gi­tu­di­nal wake fields have been cal­cu­lat­ed by using 3D code, CST Par­ti­cle Stu­dio, for a num­ber of dif­fer­ent vac­u­um cham­ber com­po­nents of the 6.4 km ILC damp­ing ring de­sign. Based on the re­sults, stud­ies of bunch length­en­ing and sin­gle-bunch in­sta­bil­i­ties have been car­ried out. Bunch length­en­ing from a par­ti­cle track­ing code are com­pared with re­sults from nu­mer­i­cal so­lu­tion of the Haissin­s­ki equa­tion. The track­ing code is used to pre­dict the thresh­old for sin­gle-bunch in­sta­bil­i­ties.

• M. Korostelev, A. Wolski
  Cockcroft Institute, Warrington, Cheshire

A new lat­tice de­sign for the ILC damp­ing ring has been de­vel­oped since the be­gin­ning of 2008 as a lower cost al­ter­na­tive to the pre­vi­ous OCS6 de­sign. The lat­tices for the elec­tron and positron damp­ing rings are iden­ti­cal, and are de­signed to pro­vide an in­tense, 5 GeV beam with low emit­tance at ex­trac­tion. The lat­est de­sign, pre­sent­ed in this paper, pro­vides suf­fi­cient dy­nam­ic aper­ture for the large positron beam at in­jec­tion. The lat­tice also meets the en­gi­neer­ing re­quire­ments for ar­range­ment of the positron ring di­rect­ly above the elec­tron ring in the same tun­nel, using com­mon gird­ers for the mag­nets in the two rings, but with the beams cir­cu­lat­ing in op­po­site di­rec­tions.

• K.G. Panagiotidis, A. Wolski
  Cockcroft Institute, Warrington, Cheshire
• M. Korostelev, K.G. Panagiotidis
  The University of Liverpool, Liverpool

One of the major chal­lenges for the In­ter­na­tion­al Lin­ear Col­lid­er (ILC) damp­ing rings is the at­tain­ment of the 2 pm ver­ti­cal emit­tance spec­i­fi­ca­tion. To achieve such an ul­tra-low ver­ti­cal emit­tance a high­ly ef­fec­tive di­ag­nos­tics and cor­rec­tion sys­tem is need­ed. How­ev­er, since both BPMs and cor­rec­tors have also neg­a­tive im­pacts on the de­sign (cost, com­plex­i­ty, impedance), it is im­por­tant to un­der­stand how the num­ber and lo­ca­tions of both these com­po­nents af­fect the cor­rec­tion. In this paper we pre­sent the re­sults of sim­u­la­tions for the Tech­ni­cal De­sign Phase base­line damp­ing rings lat­tice (DCO4), aimed at un­der­stand­ing the ef­fec­tive­ness of orbit, dis­per­sion, and cou­pling cor­rec­tion for dif­fer­ent de­sign and op­er­a­tion sce­nar­ios.

• Y. Giboudot, R. Nilavalan
  Brunel University, Middlesex
• T.R. Edgecock
  STFC/RAL, Chilton, Didcot, Oxon
• A. Wolski
  The University of Liverpool, Liverpool

The Non Scal­ing Fixed Field Al­ter­nat­ing Gra­di­ent EMMA has a com­pact lin­ear lat­tice. Ef­fect of Fringe Field on the beam has to be stud­ied care­ful­ly. A nu­mer­i­cal mag­net­ic field map is gen­er­at­ed by mag­net mea­sure­ments or mag­net de­sign soft­wares. We de­vel­oped a tech­nique that pro­duces from the nu­mer­i­cal field map, a dy­nam­i­cal map for a par­ti­cle trav­el­ling in the en­tire EMMA cell for a ref­er­ence en­er­gy with­out ac­cel­er­a­tion. Since the beam dy­nam­ics change with en­er­gy, a set of maps have been pro­duce with dif­fer­ent ref­er­ence en­er­gies be­tween 10 and 20MeV. For each ref­er­ence en­er­gy, sim­u­lat­ed tune and time of flight (TOF) have been com­pared with re­sults in Zgoubi - track­ing di­rect­ly through nu­mer­i­cal field map. The range of va­lid­i­ty of a sin­gle map has been in­ves­ti­gat­ed by track­ing par­ti­cle with large en­er­gy de­vi­a­tion. From that, a sen­si­ble ac­cel­er­a­tion scheme has been im­ple­ment­ed.

yoel.giboudot@stfc.ac.uk

• L. Zang
  Cockcroft Institute, Warrington, Cheshire
• I.R. Bailey
  Lancaster University, Lancaster
• M. Korostelev, A. Wolski
  The University of Liverpool, Liverpool

CLIC will need of order 10 to the 14 positrons per sec­ond to achieve its spec­i­fied lu­mi­nos­i­ty. For such a chal­lenge, an un­du­la­tor based scheme has been pro­posed as one of the op­tions for the positron source. As CLIC may op­er­ate over a wide range of en­er­gy (from 0.5 TeV to 3 TeV), there is a large mar­gin for us to push the per­for­mance of the whole sys­tem to be more ef­fi­cient. We re­port on the un­du­la­tor pa­ram­e­ters and op­ti­miza­tion of com­po­nents of the source such as con­ver­sion tar­get, AMD, solenoid and cap­ture RF for dif­fer­ent op­er­a­tional sce­nar­ios. In ad­di­tion to max­i­miz­ing the positron yield the po­lar­iza­tion of the positron beam are also con­sid­ered.

• A. Wolski, M. Korostelev, K.G. Panagiotidis
  The University of Liverpool, Liverpool

BPMs ca­pa­ble of high res­o­lu­tion turn-by-turn bunch po­si­tion mea­sure­ments are be­com­ing in­creas­ing­ly wide­ly used in elec­tron stor­age rings. Anal­y­sis of the data from a set of such BPMs fol­low­ing the ex­ci­ta­tion of a co­her­ent be­ta­tron os­cil­la­tion can yield use­ful in­for­ma­tion for tun­ing the op­tics and im­prov­ing ma­chine per­for­mance. This ap­proach to op­tics mea­sure­ment has the ben­e­fits that the data col­lec­tion is very fast, and anal­y­sis can be local, so that ap­pli­ca­tion is as easy for a large ring as for a small one. Here, we de­scribe a tech­nique for using turn-by-turn BPM data to de­ter­mine lat­tice func­tions that de­scribe the local cou­pling in a stor­age ring; this may be help­ful, for ex­am­ple, for achiev­ing low ver­ti­cal emit­tance. We dis­cuss the prin­ci­ples of the tech­nique, give some ex­am­ples, and dis­cuss pos­si­ble lim­i­ta­tions aris­ing from BPM gain and cou­pling er­rors.

• Y. Giboudot
  Brunel University, Middlesex
• I. Kirkman, A. Wolski
  The University of Liverpool, Liverpool

The Non Scal­ing Fixed Field Al­ter­nat­ing Gra­di­ent (NS-FFAG) EMMA ac­cel­er­a­tor has a pure­ly lin­ear lat­tice and thus al­lows im­por­tant tune vari­a­tion. The cross­ing of res­o­nances dur­ing ac­cel­er­a­tion is a key char­ac­ter­is­tic of the beam dy­nam­ics. An ac­cu­rate mea­sure­ment of the tune is there­fore manda­to­ry. How­ev­er com­mon­ly used mea­sure­ment tech­niques re­quires the beam to per­form an im­por­tant num­ber of turns in the ma­chine. Sim­u­la­tions have shown that fast de­co­her­ence of the beam re­quires the study of an­oth­er mea­sure­ment tech­nique. The model in­de­pen­dent anal­y­sis (MIA) has been in­ves­ti­gat­ed. The sin­gu­lar value de­com­po­si­tion (SVD) of a ma­trix com­posed of sim­u­lat­ed BPMs read­ing of var­i­ous bunch­es tra­jec­to­ries gives a de­scrip­tion of the op­tics func­tion at each Beam Po­si­tion Mon­i­tor. In­clud­ing mis­align­ment er­rors and elec­tron­ic noise, an ac­cu­rate value of the tune has been de­rived from sta­tis­ti­cal treat­ment re­peat­ing this pro­cess few hun­dreds of time.

yoel.giboudot@stfc.ac.uk