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Title: Detection and clearing of trapped ions in the high current Cornell photoinjector

Here, we have recently performed experiments to test the effectiveness of three ion-clearing strategies in the Cornell high intensity photoinjector: DC clearing electrodes, bunch gaps, and beam shaking. The photoinjector reaches a new regime of linac beam parameters where high continuous wave beam currents lead to ion trapping. Therefore ion mitigation strategies must be evaluated for this machine and other similar future high current linacs. We have developed several techniques to directly measure the residual trapped ions. Our two primary indicators of successful clearing are the amount of ion current removed by a DC clearing electrode, and the absence of bremsstrahlung radiation generated by beam-ion interactions. Measurements were taken for an electron beam with an energy of 5 MeV and continuous wave beam currents in the range of 1–20 mA. Several theoretical models have been developed to explain our data. Using them, we are able to estimate the clearing electrode voltage required for maximum ion clearing, the creation and clearing rates of the ions while employing bunch gaps, and the sinusoidal shaking frequency necessary for clearing via beam shaking. In all cases, we achieve a maximum ion clearing of at least 70% or higher, and in some cases our datamore » is consistent with full ion clearing.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Cornell Univ., Ithaca, NY (United States)
Publication Date:
Grant/Contract Number:
SC0012493
Type:
Published Article
Journal Name:
Physical Review Accelerators and Beams
Additional Journal Information:
Journal Volume: 19; Journal Issue: 3; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society (APS)
Research Org:
Cornell Univ., Ithaca, NY (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION
OSTI Identifier:
1240215
Alternate Identifier(s):
OSTI ID: 1436130