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Title: Beam tests of beampipe coatings for electron cloud mitigation in Fermilab Main Injector

Electron cloud beam instabilities are an important consideration in virtually all high-energy particle accelerators and could pose a formidable challenge to forthcoming high-intensity accelerator upgrades. Dedicated tests have shown beampipe coatings dramatically reduce the density of electron cloud in particle accelerators. In this work, we evaluate the performance of titanium nitride, amorphous carbon, and diamond-like carbon as beampipe coatings for the mitigation of electron cloud in the Fermilab Main Injector. Altogether our tests represent 2700 ampere-hours of proton operation spanning five years. Three electron cloud detectors, retarding field analyzers, are installed in a straight section and allow a direct comparison between the electron flux in the coated and uncoated stainless steel beampipe. We characterize the electron flux as a function of intensity up to a maximum of 50 trillion protons per cycle. Each beampipe material conditions in response to electron bombardment from the electron cloud and we track the changes in these materials as a function of time and the number of absorbed electrons. Contamination from an unexpected vacuum leak revealed a potential vulnerability in the amorphous carbon beampipe coating. We measure the energy spectrum of electrons incident on the stainless steel, titanium nitride and amorphous carbon beampipes. We findmore » the electron cloud signal is highly sensitive to stray magnetic fields and bunch-length over the Main Injector ramp cycle. In conclusion, we conduct a complete survey of the stray magnetic fields at the test station and compare the electron cloud signal to that in a field-free region.« less
Authors:
 [1] ;  [2] ;  [1] ;  [1]
  1. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Indiana Univ., Bloomington, IN (United States)
Publication Date:
OSTI Identifier:
1253001
Report Number(s):
FERMILAB-PUB--15-366-AD-APC; arXiv:1507.07281
Journal ID: ISSN 0018-9499; 1385164
Grant/Contract Number:
AC02-07CH11359
Type:
Accepted Manuscript
Journal Name:
IEEE Transactions on Nuclear Science
Additional Journal Information:
Journal Volume: 63; Journal Issue: 2; Journal ID: ISSN 0018-9499
Publisher:
Institute of Electrical and Electronics Engineers (IEEE)
Research Org:
Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS