• D. Egger
  EPFL, Lausanne
• A.E. Dabrowski, S. Döbert, D. Egger, T. Lefèvre, O. Mete
  CERN, Geneva

To im­prove the qual­i­ty of the CLIC Test Fa­cil­i­ty 3 drive beam, it has been pro­posed that a photo in­jec­tor re­places the ac­tu­al thermion­ic gun. This would pro­duce a lower emit­tance beam and min­i­mize beam loss­es in the in­jec­tor since the RF bunch­ing and sub‐har­mon­ic bunch­ing sys­tems would not be need­ed any­more. Such a photo in­jec­tor, named PHIN, is cur­rent­ly being de­vel­oped at CERN. One of the dif­fi­cul­ties is to pro­vide a high in­ten­si­ty beam (3.5A) with a sta­ble (0.1%) beam en­er­gy over 1.5us as well as a rel­a­tive en­er­gy spread less than 1%. A 90° spec­trom­e­ter line fea­tur­ing a seg­ment­ed dump and an Op­ti­cal Tran­si­tion Ra­di­a­tion screen has been con­struct­ed and com­mis­sioned in order to study the time evo­lu­tion of the beam en­er­gy along the pulse du­ra­tion. In the fol­low­ing paper, we pre­sent the de­sign as well as the re­sults from the pre­vi­ous two PHIN runs.

• A.E. Dabrowski, S. Bettoni, E. Bravin, R. Corsini, S. Döbert, T. Lefèvre, A. Rabiller, P.K. Skowronski, L. Søby, F. Tecker
  CERN, Geneva
• D. Egger
  EPFL, Lausanne
• A. Ferrari
  Uppsala University, Uppsala
• C.P. Welsch
  The University of Liverpool, Liverpool

The CTF3 fa­cil­i­ty is being built and com­mis­sioned by an in­ter­na­tion­al col­lab­o­ra­tion in order to test the fea­si­bil­i­ty of the pro­posed CLIC drive beam gen­er­a­tion scheme. Cen­tral to this scheme is the use of RF de­flec­tors to in­ject bunch­es into a Delay Loop and a Com­bin­er Ring, in order to trans­form the ini­tial bunch spac­ing of 1.5 GHz from the linac to a final bunch spac­ing of 12 GHz. The op­ti­miza­tion pro­ce­dure re­lies on sev­er­al steps. The ac­tive length of each ring is care­ful­ly ad­just­ed to with­in a few mil­lime­ters ac­cu­ra­cy using a two‐pe­ri­od un­du­la­tor. The trans­verse op­tics of the ma­chine must be set-up in a way so as to en­sure the beam isochronic­i­ty. Di­ag­nos­tics based on op­ti­cal streak cam­eras and RF power mea­sure­ments have been de­signed to mea­sure the lon­gi­tu­di­nal be­haviour of the beam dur­ing the com­bi­na­tion. This paper pre­sents their per­for­mance and high­lights re­cent mea­sure­ments.

• M. Olvegård, E. Bravin, F. Carra, N.C. Chritin, A.E. Dabrowski, A. Dallocchio, S. Döbert, T. Lefèvre
  CERN, Geneva
• E. Adli
  University of Oslo, Oslo

The CLIC study is based on the so‐called two‐beam ac­cel­er­a­tion con­cept and one of the main goals of the CLIC Test Fa­cil­i­ty 3 is to demon­strate the ef­fi­cien­cy of the CLIC RF power pro­duc­tion scheme. As part of this fa­cil­i­ty a Test Beam Line (TBL), present­ly under com­mis­sion­ing, is a small scale ver­sion of a CLIC de­cel­er­a­tor. To per­form as ex­pect­ed the beam line must show ef­fi­cient and sta­ble RF power pro­duc­tion over 16 con­sec­u­tive de­cel­er­at­ing struc­tures. As the high in­ten­si­ty elec­tron beam is de­cel­er­at­ed its en­er­gy spread grows by up to 60%. A novel seg­ment­ed beam dump for time re­solved en­er­gy mea­sure­ments has been de­signed to match the re­quire­ments of the TBL. As a com­ple­ment, a dif­fu­sive OTR screen is also in­stalled in the same spec­trom­e­ter line. The com­bi­na­tion of these two de­vices will pro­vide both a high spa­tial res­o­lu­tion mea­sure­ment of both the en­er­gy and en­er­gy spread and a mea­sure­ment with a few nanosec­onds time re­sponse. This paper de­scribes the de­sign of the new seg­ment­ed dump and pre­sents the re­sults from the first com­mis­sion­ing of the TBL spec­trom­e­ter line.

• M. Micheler, G.A. Blair, G.E. Boorman, V. Karataev, K. Lekomtsev
  JAI, Egham, Surrey
• R. Corsini, A.E. Dabrowski, T. Lefèvre
  CERN, Geneva
• S. Molloy
  Royal Holloway, University of London, Surrey

A setup for the in­ves­ti­ga­tion of Co­her­ent Diffrac­tion Ra­di­a­tion (CDR) from a con­duct­ing screen as a tool for non-in­va­sive lon­gi­tu­di­nal elec­tron beam pro­file di­ag­nos­tics has been de­signed and in­stalled in the Com­bin­er Ring Mea­sure­ment (CRM) line of the CLIC Test Fa­cil­i­ty (CTF3, CERN). In this re­port the sta­tus of the mon­i­tor de­vel­op­ment and re­sults on the in­ter­fer­o­met­ric mea­sure­ments of CDR spec­tra are pre­sent­ed. The CDR sig­nal cor­re­la­tion with an RF pick­up and a streak cam­era is re­port­ed. The fu­ture plans for the sys­tem im­prove­ments are also dis­cussed.

• P.K. Skowronski, S. Bettoni, R. Corsini, A.E. Dabrowski, S. Döbert, A. Dubrovskiy, F. Tecker
  CERN, Geneva
• C. Biscari
  INFN/LNF, Frascati (Roma)
• W. Farabolini
  CEA, Gif-sur-Yvette
• R.J.M.Y. Ruber
  Uppsala University, Uppsala

The ob­jec­tive of the CLIC Test Fa­cil­i­ty CTF3 is to demon­strate the key fea­si­bil­i­ty is­sues of the CLIC two-beam tech­nol­o­gy: the ef­fi­cient gen­er­a­tion of a very high cur­rent drive beam and its sta­ble de­cel­er­a­tion in 12 GHz res­o­nant struc­tures, to pro­duce high-pow­er RF puls­es and ac­cel­er­ate the main beam with an ac­cel­er­at­ing gra­di­ent of 100 MV/m. The con­struc­tion and com­mis­sion­ing of CTF3 has taken place in stages from 2003. Many mile­stones had al­ready been reached, in­clud­ing the first demon­stra­tion at the end of 2009 of a fac­tor 2 x 4 re-com­bi­na­tion of the ini­tial drive beam pulse, thus reach­ing a beam cur­rent of 25 A. In this paper we sum­marise the com­mis­sion­ing high­lights and the is­sues al­ready val­i­dat­ed at the ear­li­er stages. We then show and dis­cuss the lat­est re­sults ob­tained, in view of the com­ple­tion of the CLIC fea­si­bil­i­ty demon­stra­tion due for the end of 2010.

• M. Petrarca, E. Chevallay, A.E. Dabrowski, M. Divall Csatari, S. Döbert, D. Egger, V. Fedosseev, T. Lefèvre, R. Losito, O. Mete
  CERN, Geneva

The high charge PHIN photo in­jec­tor is stud­ied at CERN as an elec­tron source for the CLIC Test Fa­cil­i­ty (CTF3) drive beam as an al­ter­na­tive to the pre­sent thermion­ic gun. The ob­jec­tive of PHIN is to demon­strate the fea­si­bil­i­ty of a laser-based elec­tron source for CLIC. The photo in­jec­tor op­er­ates with a 2.5 cell, 3 GHz RF gun using a Cs2Te pho­to­cath­ode il­lu­mi­nat­ed by UV laser puls­es gen­er­at­ed by am­pli­fy­ing and fre­quen­cy qua­dru­pling the sig­nal from a Nd:YLF os­cil­la­tor run­ning at 1.5GHz. The chal­lenge is to gen­er­ate a beam struc­ture of 1908μbunch­es with 2.33nC perμbunch at 1.5GHz lead­ing to a high in­te­grat­ed train charge of 4446nC and nom­i­nal beam en­er­gy of 5.5MeV with cur­rent sta­bil­i­ty below 1%. In the pre­sent test stand, a seg­ment­ed beam dump has been im­ple­ment­ed al­low­ing a time re­solved mea­sure­ment of the en­er­gy and en­er­gy spread of the elec­tron beam. In this paper we re­port and dis­cuss the mea­sured trans­verse and lon­gi­tu­di­nal beam pa­ram­e­ters for both the full and time gated train of bunch­es, and the ob­tained pho­to­cath­ode quan­tum ef­fi­cien­cy. Laser point­ing and am­pli­tude sta­bil­i­ty re­sults are dis­cussed tak­ing into ac­count cor­re­la­tion be­tween laser and elec­tron beam.

• E. Adli
  University of Oslo, Oslo
• A.E. Dabrowski, S. Döbert, M. Olvegård, D. Schulte, I. Syratchev
  CERN, Geneva
• R.L. Lillestol
  NTNU, Trondheim

The CLIC Test Fa­cil­i­ty 3 Test Beam Line is the first pro­to­type for the CLIC drive beam de­cel­er­a­tor. Sta­ble trans­port of the drive beam under de­cel­er­a­tion is a manda­to­ry com­po­nent in the CLIC two-beam scheme. In the Test Beam Line more than 50% of the total en­er­gy will be ex­tract­ed from a 150 MeV, 28 A elec­tron drive beam, by the use of 16 Power Ex­trac­tion and Trans­fer struc­tures. A num­ber of ex­per­i­ments are fore­seen to in­ves­ti­gate the drive beam char­ac­ter­is­tics under de­cel­er­a­tion in the Test Beam Line, in­clud­ing beam sta­bil­i­ty, beam blow up and the ef­fi­cien­cy of the power ex­trac­tion. Gen­er­al bench­mark­ing of de­cel­er­a­tor sim­u­la­tion and the­o­ry stud­ies will also be per­formed. Spe­cial­ly de­signed in­stru­men­ta­tion in­clud­ing pre­ci­sion BPMs, loss mon­i­tors and a time-re­solved spec­trom­e­ter dump will be used for the ex­per­i­ments. This paper de­scribes the ex­per­i­men­tal pro­gram fore­seen for the Test Beam Line, in­clud­ing the rel­e­vance of the re­sults for the CLIC de­cel­er­a­tor stud­ies.