CTF3 Probe Beam LINAC Commissioning and Operations

The probe beam LINAC, CAL­IFES, of the CLIC Test Fa­cil­i­ty (CTF3) has been de­vel­oped by CEA Saclay, LAL Orsay and CERN to de­liv­er trains of short bunch­es (0.75 ps) spaced by 0.666 ps at an en­er­gy around 170 MeV with a charge of 0.6 nC to the TBTS (Two-beam Test Stand) in­tend­ed to test the high gra­di­ent CLIC ac­cel­er­at­ing struc­tures. Based on 3 for­mer LIL ac­cel­er­at­ing struc­tures and on a newly de­vel­oped RF pho­to-in­jec­tor, the whole ac­cel­er­a­tor is pow­ered with a sin­gle 3 GHz klystron de­liv­er­ing puls­es of 45 MW through a RF pulse com­pres­sion cav­i­ty and a net­work of waveg­uides, split­ters, phase-shifters and an at­ten­u­a­tor. We re­late here re­sults col­lect­ed dur­ing the var­i­ous com­mis­sion­ing and op­er­a­tion pe­ri­ods which led to nom­i­nal per­for­mances and sta­ble beam char­ac­ter­is­tics de­liv­ered to the TBTS. Progress has been made in the laser sys­tem for beam charge and sta­bil­i­ty, in space charge com­pen­sa­tion for emit­tance, in RF com­pres­sion law for en­er­gy and en­er­gy spread. The in­stal­la­tion of a spe­cial­ly de­vel­oped RF power phase shifter for the first ac­cel­er­at­ing struc­ture used in ve­loc­i­ty bunch­ing al­lows the con­trol of the bunch length.