Author: Velthaus, V.
Paper Title Page
TU1C2
 Surface Treatment Procedures to Mitigate Ion-Induced Desorption in Heavy Ion Accelerators  
 
  • V. Velthaus, M. Bender, C. Trautmann
    GSI, Darmstadt, Germany
  
  Ion-in­duced des­orp­tion is a se­ri­ous lim­i­ta­tion for sta­ble op­er­a­tion of high beam in­ten­si­ties in heavy ion syn­chro­trons. Next gen­er­a­tion heavy ion ac­cel­er­a­tors like FAIR or SPI­RAL2 are de­signed for in­ten­si­ties that are or­ders of mag­ni­tude higher than the in­ten­sity of ex­ist­ing ma­chines. Hence, ion-in­duced des­orp­tion be­comes a big chal­lenge. To bet­ter un­der­stand and con­trol the in­flu­ence of ma­te­r­ial and sur­face fac­tors, des­orp­tion mea­sure­ments with swift heavy ions (Ca and Au at 4.8 MeV/u) were con­ducted with focus on oxy­gen-free cop­per and tung­sten sam­ples. The sur­faces were treated by dif­fer­ent com­bi­na­tions of milling, lap­ping, pol­ish­ing, etch­ing and sput­ter­ing. Some of the sam­ples were coated by car­bon, ti­ta­nium ni­tride or TiZrV. For all tested sam­ples des­orp­tion yields (num­ber of re­leased mol­e­cules per im­pact­ing ion) for H2, H2O, CO, CO2, O2 and Ar will be pre­sented. For cop­per, sur­face clean­ing by sput­ter­ing with 5 keV argon ions re­duces the des­orp­tion yield sig­nif­i­cantly. An­other promis­ing method to re­duce ion-in­duced des­orp­tion is ther­mal an­neal­ing at 400 °C for about 4 h under ul­tra-high vac­uum con­di­tions. Suit­able an­neal­ing and clean­ing pa­ra­me­ters will be pre­sented.  
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