• M.A. Palmer, M.G. Billing, R.E. Meller, M.C. Rendina, N.T. Rider, D. L. Rubin, J.P. Shanks, C.R. Strohman
  CLASSE, Ithaca, New York
• R. Holtzapple
  CalPoly, San Luis Obispo, CA

The beam po­si­tion mon­i­tor (BPM) sys­tem at the Cor­nell Elec­tron Stor­age Ring (CESR) has been up­grad­ed for use in both CESR Test Ac­cel­er­a­tor (Ces­r­TA) and Cor­nell High En­er­gy Syn­chrotron Source (CHESS) op­er­a­tions. Ces­r­TA op­er­ates with elec­tron and positron bunch trains with as lit­tle as 4ns bunch spac­ing. CHESS op­er­ates with si­mul­ta­ne­ous counter-ro­tat­ing elec­tron and positron trains with 14ns bunch spac­ing. The up­grad­ed BPM sys­tem pro­vides high res­o­lu­tion mea­sure­ment ca­pa­bil­i­ty as is need­ed for the Ces­r­TA ultra low emit­tance op­er­a­tions, turn-by-turn dig­i­ti­za­tion of mul­ti­ple bunch­es for beam dy­nam­ics stud­ies, and the ca­pa­bil­i­ty for re­al-time dual beam mon­i­tor­ing in CHESS con­di­tions. In ad­di­tion to stan­dard po­si­tion mea­sure­ment ca­pa­bil­i­ty, the sys­tem is also re­quired to mea­sure be­ta­tron phase by syn­chronous de­tec­tion of a driv­en beam for op­tics di­ag­no­sis and cor­rec­tion. This paper de­scribes the char­ac­ter­is­tics of the BPM hard­ware up­grade, per­for­mance fig­ures of the elec­tron­ics de­signed for this pur­pose and the over­all sta­tus of the up­grade ef­fort. Ex­am­ples of key mea­sure­ment types and the anal­y­sis of data ac­quired from the new in­stru­ments will also be pre­sent­ed.

• 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

• J.A. Crittenden, J.R. Calvey, G. Dugan, D.L. Kreinick, Z. Leong, J.A. Livezey, M.A. Palmer, D. L. Rubin, D. Sagan
  CLASSE, Ithaca, New York
• M.A. Furman, G. Penn, M. Venturini
  LBNL, Berkeley, California
• K.C. Harkay
  ANL, Argonne
• R. Holtzapple
  CalPoly, San Luis Obispo, CA
• M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California

The Cor­nell Elec­tron Stor­age Ring Test Ac­cel­er­a­tor (Ces­r­TA) pro­gram has in­clud­ed ex­ten­sive mea­sure­ments of co­her­ent tune shifts for a va­ri­ety of elec­tron and positron beam en­er­gies, bunch cur­rent lev­els, and bunch train con­fig­u­ra­tions. The tune shifts have been shown to re­sult pri­mar­i­ly from the in­ter­ac­tion of the beam with the space-charge field of the beam-in­duced low-en­er­gy elec­tron cloud in the vac­u­um cham­ber. Com­par­i­son to sev­er­al ad­vanced elec­tron cloud sim­u­la­tion pro­gram pack­ages has al­lowed de­ter­mi­na­tion of the sen­si­tiv­i­ty of these mea­sure­ments to phys­i­cal pa­ram­e­ters such as the syn­chrotron ra­di­a­tion flux, its in­ter­ac­tion with the vac­u­um cham­ber wall, the beam emit­tance and lat­tice op­tics, as well as to those of the var­i­ous con­tri­bu­tions to the elec­tron sec­ondary yield model. We re­port on progress in un­der­stand­ing the cloud buildup and decay mech­a­nisms in mag­net­ic fields and in field-free re­gions, ad­dress­ing quan­ti­ta­tive­ly the pre­cise de­ter­mi­na­tion of the phys­i­cal pa­ram­e­ters of the mod­elling. Val­i­da­tion of these mod­els will serve as es­sen­tial input in the de­sign of damp­ing rings for fu­ture high-en­er­gy lin­ear col­lid­ers.

• J.P. Shanks, D. L. Rubin, D. Sagan
  CLASSE, Ithaca, New York

We are de­vel­op­ing tech­niques for mea­sur­ing and cor­rect­ing emit­tance di­lut­ing op­ti­cal and align­ment er­rors in the Ces­r­TA stor­age ring. Our prin­ci­ple mea­sure­ment method is to res­o­nant­ly ex­cite the beam at all three nor­mal mode fre­quen­cies and then to ex­tract the am­pli­tude and phase of each mode at all 100 beam po­si­tion mon­i­tors. We re­con­struct be­ta-func­tions, be­ta­tron phase ad­vance, cou­pling pa­ram­e­ters, dis­per­sion, and BPM tilts from the data. A com­plete char­ac­ter­i­za­tion in­clud­ing data col­lec­tion and anal­y­sis can be done in a few min­utes. To mea­sure the emit­tance, an x-ray beam size mon­i­tor ca­pa­ble of mea­sur­ing the size of a sin­gle bunch on a turn by turn basis pro­vides a real time mea­sure with a res­o­lu­tion on the order of a few mi­crons. This res­o­lu­tion cor­re­sponds to a few pm emit­tance. Our abil­i­ty to iden­ti­fy align­ment and op­ti­cal er­rors is lim­it­ed by sys­tem­at­ic mea­sure­ment er­rors. We re­port on the sta­tus of our ef­forts to un­der­stand and elim­i­nate sys­tem­at­ic er­rors, the ac­cu­ra­cy of our char­ac­ter­i­za­tion of the ma­chine op­tics, and our suc­cess at re­duc­ing sources of emit­tance di­lu­tion.