Author: Vagin, P.
Paper Title Page
MOP006
 Coherent Accelerator-based High Field THz Radiation at FLASH II  
 
  • T. Golz, V. B. Asgekar, B. Faatz, G. Geloni, N. Stojanovic, M. Tischer, P. Vagin, M. Vogt
    DESY, Hamburg, Germany
  • M. Gensch
    HZDR, Dresden, Germany
  • P. Vobly
    BINP SB RAS, Novosibirsk, Russia
  
  Funding: BMBF grant no. 05K10CHC + 05K10KEB + 05K12CH4
Lin­ear ac­cel­er­a­tor based light sources with their tun­able broad spec­tral range (THz to hard X-rays regime) and their abil­ity to gen­er­ate ul­tra-short pulses with peak in­ten­si­ties many or­ders of mag­ni­tude higher then syn­chro­tron sources, gave rise to a new field of ul­tra­fast physics. In the THz range, the abil­ity of 4th gen. light sources to gen­er­ate pulses with e-field strengths up to 1 GV/m opened the door to the field of non-lin­ear THz spec­troscopy and THz-con­trolled ma­te­r­ial sci­ence. The main ad­van­tage of ac­cel­er­a­tor-based THz is its scaleabil­ity. As the process is not bound to a par­tic­u­lar medium, but oc­curs in the ac­cel­er­a­tor vac­uum, it by­passes the lim­i­ta­tion of table top sources. In ad­di­tion, it has been demon­strated that co­her­ent THz ra­di­a­tion can be gen­er­ated along fem­tosec­ond X-ray pulses in 4th Gen­er­a­tion X-ray Light sources such as FLASH [1,2,3] and LCLS [4]. This opens up the op­por­tu­nity for nat­u­rally syn­chro­nized THz pump X-ray probe ex­per­i­ments on a few fem­tosec­ond time scale [1,2,4]. Here we pre­sent the de­sign for the THz source at FLASH2, which takes new find­ings [5] and chal­lenges into ac­count that we face dur­ing the ra­di­a­tion trans­port to the ex­per­i­men­tal hall. 		 
 
MOP008 Temperature Effects of the FLASH2 Undulators 34
 
  • M. Tischer, A. Schöps, P. Vagin
    DESY, Hamburg, Germany
  
  FELs are very sen­si­tive to small changes in the res­o­nance con­di­tion of the emit­ted ra­di­a­tion. As a con­se­quence, per­ma­nent mag­net un­du­la­tors in FELs usu­ally re­quire ex­ten­sive tem­per­a­ture con­trol in order to as­sure sta­ble op­er­a­tion con­di­tions. In prin­ci­ple, the tem­per­a­ture de­pen­dence of per­ma­nent mag­net ma­te­r­ial is well known but more things need to be con­sid­ered like dif­fer­ent ther­mal ex­pan­sion of var­i­ous me­chan­i­cal parts or ther­mally in­duced de­for­ma­tion which do not only af­fect the K pa­ra­me­ter but also the field qual­ity. We have per­formed tem­per­a­ture de­pen­dent mag­netic mea­sure­ments in a range from 19 to 28 de­grees Cel­sius and have an­a­lyzed the mag­netic per­for­mance of the un­du­la­tor. The re­sults of this case study can be trans­ferred to all FLASH2 un­du­la­tors and shall allow for a sim­ple tem­per­a­ture de­pen­dent gap cor­rec­tion in order to make the spec­tral prop­er­ties in­sen­si­tive to tem­per­a­ture changes of the in­ser­tion de­vices.