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Frentrup, W.

Paper Title Page
WEPD011 Mini-beta Sections in the Storage Ring BESSY II 3108
 
  • J. Bahrdt, W. Frentrup, A. Gaupp, M. Scheer, F. Schäfers, G. Wüstefeld
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
  
 

At BESSY II pho­ton en­er­gies above 2keV can be pro­duced only with bend­ing mag­nets, a per­ma­nent mag­net wig­gler, su­per­con­duct­ing (SC) wave­length shifters and a SC-wig­gler. The wig­gler bril­liance suf­fers from the depth of field ef­fect and the bend­ing mag­nets and wave­length shifters pro­duce the X-rays only with a sin­gle pole. Ex­per­i­ments such as HIgh Ki­net­ic En­er­gy pho­to­elec­tron spec­troscopy (HIKE) or mi­crospec­troscopy on nanos­truc­tured ma­te­ri­als de­mand a high bril­liance and flux as it is pro­vid­ed by a small pe­ri­od cryo­genic un­du­la­tor. This paper dis­cuss­es the re­quire­ments for the op­er­a­tion of small gap cryo­genic de­vices at BESSY II. A scheme with two ad­ja­cent, ver­ti­cal low beta sec­tions in­side of one of the long straight sec­tions is sug­gest­ed. The straight is di­vid­ed into two parts by a quadrupole triple in the cen­ter. An optic with an in­creased, ver­ti­cal beta tune by 0.5 is present­ly stud­ied. The op­tics out­side of the low beta sec­tion and the hor­i­zon­tal tune are kept un­changed.

  
WEPD012 Cryogenic Design of a PrFeB-Based Undulator 3111
 
  • J. Bahrdt, H.-J. Baecker, M. Dirsat, W. Frentrup, A. Gaupp, D. Pflückhahn, M. Scheer, B. Schulz
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
  • F.J. Grüner, R. Weingartner
    LMU, Garching
  • D. Just
    Technische Universität Berlin, Berlin
  • F.H. O'Shea
    UCLA, Los Angeles, California
  
 

In col­lab­o­ra­tion with the Lud­wig-Max­i­m­il­ian-Uni­ver­si­ty Mu­nich a cryo­genic PrFeB- based un­du­la­tor has been built. The 20-pe­ri­od de­vice has a pe­ri­od length of 9mm and a fixed gap of 2.5mm. The un­du­la­tor has re­cent­ly been in­stalled at the laser plas­ma ac­cel­er­a­tor at the Max-Planck-In­sti­tute for Quan­tenop­tik. The op­er­a­tion of a small gap de­vice at a high emit­tance elec­tron beam re­quires sta­ble mag­net­ic ma­te­ri­al. A high co­er­civ­i­ty is achieved with PrFeB- ma­te­ri­al which is cooled down to 50K. This tem­per­a­ture is 100K lower as com­pared to the tem­per­a­ture of a Nd­FeB-based cryo­genic un­du­la­tor. In this paper we pre­sent the me­chan­ic and cryo­genic de­sign and com­pare the pre­dic­tions with mea­sured data. The re­sults are ex­trap­o­lat­ed to a 2m-long vari­able gap un­du­la­tor.