Author: Olvegaard, M.     [Olvegård, M.]
Paper Title Page
MOCL3 Emittance and Momentum Diagnostics for Beams with Large Momentum Spread 37
 
  • M. Olvegård, V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  
  In the drive beam com­plex of CLIC, but also in plasma wake­field ac­cel­er­a­tors, the mo­men­tum spread can be on the order of tens of per­cent while con­ven­tional di­ag­nos­tic meth­ods often as­sume a very small mo­men­tum spread. This leads to sys­tem­atic mis­in­ter­pre­ta­tions of the mea­sure­ments. Spec­trom­e­try and emit­tance mea­sure­ments based on quadru­pole scan rely on mea­sur­ing the beam size, which de­pends on the beam en­ve­lope. This, in turn, de­pends on the mo­men­tum dis­tri­b­u­tion. We have stud­ied the sys­tem­atic er­rors that arise and de­vel­oped novel al­go­rithms to cor­rectly an­a­lyze these mea­sure­ments for ar­bi­trary mo­men­tum dis­tri­b­u­tions. As an ap­pli­ca­tion we con­sider the CLIC drive beam de­cel­er­a­tor, where ex­trac­tion of up to 90% of the ki­netic en­ergy leads to a very large mo­men­tum spread. We study a mea­sure­ment of the time-re­solved mo­men­tum dis­tri­b­u­tion, based on sweep­ing the beam in a cir­cu­lar pat­tern and record­ing the beam size on a screen using op­ti­cal tran­si­tion ra­di­a­tion. We pre­sent the al­go­rithm to ex­tract the time-re­solved mo­men­tum dis­tri­b­u­tion, to­gether with sim­u­la­tion re­sults to prove its ap­plic­a­bil­ity.  
slides icon Slides MOCL3 [2.984 MB]  
 
MOPF30 Novel Diagnostics for Breakdown Studies 287
 
  • M. Jacewicz, Ch. Borgmann, M. Olvegård, R.J.M.Y. Ruber, V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  • J.W. Kovermann
    CERN, Geneva, Switzerland
  
  The phe­nom­e­non that cur­rently pre­vents achiev­ing high ac­cel­er­at­ing gra­di­ents in high en­ergy ac­cel­er­a­tors such as the CLIC lin­ear col­lider is elec­tri­cal break­down at very high elec­tri­cal field. The on­go­ing ex­per­i­men­tal work is try­ing to bench­mark the the­o­ret­i­cal mod­els fo­cus­ing on the physics of vac­uum break­down which is re­spon­si­ble for the dis­charges. The CLIC col­lab­o­ra­tion has com­mis­sioned a ded­i­cated 12 GHz test-stand to val­i­date the fea­si­bil­ity of ac­cel­er­at­ing struc­tures and ob­serve the char­ac­ter­is­tics of the RF dis­charges and their erod­ing ef­fects on the struc­ture. A ver­sa­tile sys­tem for de­tec­tion of the dark and break­down cur­rents and light emis­sion is being de­vel­oped for the test-stand. It con­sists of a col­li­ma­tion sys­tem with an ex­ter­nal mag­netic spec­trom­e­ter for mea­sure­ment of the spa­tial and en­ergy dis­tri­b­u­tions of the elec­trons emit­ted from the ac­cel­er­a­tion struc­ture dur­ing a sin­gle RF pulse. These mea­sure­ments can be cor­re­lated with e.g. the lo­ca­tion of the break­down in­side the struc­ture using in­for­ma­tion from the in­ci­dent, re­flected and trans­mit­ted RF pow­ers giv­ing a com­plete pic­ture of the vac­uum break­down phe­nom­e­non.