Author: Zimmermann, R.
Paper Title Page
MOPC077 Commissioning of Multibunch Feedback Systems at the Fast Ramping Stretcher Ring ELSA 250
 
  • A. Roth, F. Frommberger, N. Heurich, W. Hillert, M. Schedler, R. Zimmermann
    ELSA, Bonn, Germany
  
  Funding: Supported by German Research Foundation through SFB/TR 16 and by Helmholtz Alliance through HA-101.
At the Elec­tron Stretch­er Fa­cil­i­ty ELSA of Bonn Uni­ver­si­ty, an ex­ter­nal beam of ei­ther un­po­lar­ized or po­lar­ized elec­trons is sup­plied to hadron physics ex­per­i­ments. The ELSA stretcher­ring op­er­ates in the en­er­gy range of 1.2 to 3.5 GeV and achieves a duty cycle of up to 80% using a fast en­er­gy ramp of 4 GeV/s. Under these con­di­tions, an in­crease of the in­ter­nal beam cur­rent from an ac­tu­al value of 20 mA up to 200 mA is planned. Such an up­grade is main­ly lim­it­ed by the ex­ci­ta­tion of multi­bunch in­sta­bil­i­ties. As one ac­tive coun­ter­ac­tion, we have in­stalled state-of-the-art bunch-by-bunch feed­back sys­tems for the lon­gi­tu­di­nal, as well as for both trans­verse planes. The de­tailed setup with all main com­po­nents and first re­sults of the com­mis­sion­ing of the sys­tems will be pre­sent­ed. In par­tic­u­lar, the per­for­mance of the lon­gi­tu­di­nal feed­back with a sta­bi­lized syn­chrotron fre­quen­cy dur­ing the fast en­er­gy ramp will be dis­cussed. 		 
 
MOPO004 A Longitudinal Kicker Cavity for a Bunch-by-bunch Feedback System at ELSA 484
 
  • N. Heurich, W. Hillert, A. Roth, R. Zimmermann
    ELSA, Bonn, Germany
  
  At the Elec­tron Stretch­er Fa­cil­i­ty ELSA of Bonn Uni­ver­si­ty, a lon­gi­tu­di­nal bunch-by-bunch feed­back sys­tem is cur­rent­ly being in­stalled in order to damp multi­bunch in­sta­bil­i­ties and to en­able a fu­ture in­ten­si­ty up­grade of up to 200 mA. As a main com­po­nent, a lon­gi­tu­di­nal kick­er cav­i­ty was de­vel­oped and man­u­fac­tured. The kick­er re­quires a band­width of 250~MHz tak­ing into ac­count the bunch spac­ing of 2 ns at ELSA. Ex­ist­ing de­signs used at other fa­cil­i­ties were op­ti­mized in view of the con­sid­er­ably larg­er bunch lenght at ELSA. The choice of 1.125 GHz as a cen­ter fre­quen­cy is a re­sult of these con­sid­er­a­tions. With the re­sult­ing low qual­i­ty fac­tor, the de­sign had to be op­ti­mized in order to max­i­mize the shunt impedance. The lon­gi­tu­di­nal feed­back is suc­ces­ful­ly work­ing with the pro­to­type in­stalled in the stretch­er ring. The de­sign and de­tailed sim­u­la­tions of the ge­om­e­try are dis­cussed and lab­o­ra­to­ry mea­sure­ments are pre­sent­ed.  
 
TUPC074 A New Counting Silicon Strip Detector System for Precise Compton Polarimetry 1171
 
  • R. Zimmermann, W. Hillert, J.C. Wittschen
    ELSA, Bonn, Germany
  
  Funding: Supported by the German Research Foundation within the SFB/TR16
A Comp­ton po­larime­ter is cur­rent­ly being in­stalled at the Elec­tron Stretch­er Fa­cil­i­ty ELSA to mon­i­tor the de­gree of po­lar­iza­tion of the stored elec­tron beam. For this pur­pose, cir­cu­lar­ly po­lar­ized light that is emit­ted by a laser and backscat­tered off the beam has to be de­tect­ed. Above all, as a re­sult of ELSA's beam en­er­gies, it is nec­es­sary to mea­sure the shift of the cen­ter of the pho­ton spa­tial dis­tri­bu­tion which is ob­tained when the po­lar­iza­tion of the laser is switched from left-hand to right-hand cir­cu­lar po­lar­iza­tion with an ac­cu­ra­cy of a few mi­crons. In order to meet the re­quired spec­i­fi­ca­tions, a new count­ing sil­i­con strip de­tec­tor sys­tem has been de­vel­oped in co­op­er­a­tion with the SiLab/ATLAS group of the Physics In­sti­tute of the Uni­ver­si­ty of Bonn. In this con­tri­bu­tion, the de­sign of the sys­tem will be pre­sent­ed and first re­sults will be shown.