• D.P. Peterson, J.P. Alexander, C.J. Conolly, N. Eggert, E. Fontes, W.H. Hopkins, B. Kreis, A. Lyndaker, M.P. McDonald, M.A. Palmer, M.C. Rendina, P. Revesz, N.T. Rider, J.J. Savino, R.D. Seeley
  CLASSE, Ithaca, New York
• J.W. Flanagan
  KEK, Ibaraki

We re­port on the de­sign and op­er­a­tion of the Ces­r­TA x-ray beam size mon­i­tor (xBSM). The xBSM res­o­lu­tion must be suf­fi­cient to mea­sure ver­ti­cal beam sizes of order 10um by imag­ing 2-4keV syn­chrotron ra­di­a­tion pho­tons onto a one-di­men­sion­al pho­to­di­ode array. In­stru­men­ta­tion in the evac­u­at­ed x-ray beam line in­cludes up­stream in­ter­change­able op­tics el­e­ments (slits, coded aper­tures, and Fres­nel zone plates), a monochro­ma­tor and an In­GaAs pho­to­di­ode de­tec­tor. The read­out is a beam-syn­chro­nized FADC that is ca­pa­ble of par­al­lel mea­sure­ment of con­sec­u­tive bunch­es with 4ns spac­ing. The xBSM has been used to mea­sure beam sizes dur­ing the Au­gust 2009, Novem­ber 2009, and April 2010 runs. Sin­gle turn mea­sure­ments are fit to char­ac­ter­is­tic image shapes to ex­tract beam sizes in­de­pen­dent of po­si­tion vari­a­tions. The turn-av­er­aged beam size pro­vides feed­back for low-emit­tance tun­ing.

• 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.W. Flanagan, H. Fukuma, H. Ikeda, T.M. Mitsuhashi
  KEK, Ibaraki
• J.P. Alexander, N. Eggert, W.H. Hopkins, M.A. Palmer, D.P. Peterson
  CLASSE, Ithaca, New York
• B. Kreis
  Cornell University, Ithaca, New York
• G.S. Varner
  UH, Honolulu, HI

An x-ray beam size mon­i­tor based on coded aper­ture imag­ing* has been de­vel­oped at Ces­r­TA, for the pur­pose of mak­ing bunch-by-bunch, turn-by-turn mea­sure­ments of low emit­tance beams. Using low-emit­tance beam (~44 pm, or 16 mi­crons at the x-ray source point) we have been able to make de­tailed com­par­isons be­tween the mea­sured mask re­sponse and that pre­dict­ed by the­o­ry, val­i­dat­ing our sim­u­la­tions of the mask re­sponse. In turn, we demon­strate the abil­i­ty to mea­sure both in­te­grat­ed and sin­gle-bunch turn-by-turn beam sizes and po­si­tions for mon­i­tor­ing the progress of the low-emit­tance tun­ing of the ma­chine, and for elec­tron-cloud in­sta­bil­i­ty-re­lat­ed beam dy­nam­ics stud­ies.

* J.W. Flanagan et al., EPAC08, 1029 (2008).