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Title: Measurement of internal dark current in a 17 GHz, high gradient accelerator structure

Abstract

We report the measurement of the internal dark current in a 17 GHz, high gradient accelerator cavity and its comparison with theory. The cavities were fabricated from copper and had a sidewall that was either uncoated or coated with diamond-like carbon or TiN. The dark current was monitored by a downstream detector and by detectors behind two small slits made in the cavity side wall. With an increasing gradient, the downstream current increased monotonically, as expected for field emission. The variation of the internal, side dark current was not monotonic but showed the onset of peaks at gradients near 45 and 65 MV/m. These were identified as the N = 2 and N = 1 single point multipactor resonances. The total internal dark current was estimated at ∼15–30 A. The magnitude of the internal dark current and its dependence on the gradient were in good agreement with simulations using the CST code as well as an in-house code. Processing to a higher gradient, ∼90 MV/m, eliminated the N = 2 mode, but the N = 1 mode persisted. The coated sidewall cavities showed the same multipactor resonances as the uncoated structure. However, at the highest gradient achieved in testing, themore » coated structures showed a modest reduction in the internal dark current.« less

Authors:
; ;
Publication Date:
DOE Contract Number:  
SC0015566
Research Org.:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP)
Subject:
43 PARTICLE ACCELERATORS
OSTI Identifier:
1881438
DOI:
https://doi.org/10.7910/DVN/Q4DO2E

Citation Formats

Xu, Haoran, Shapiro, Michael A., and Temkin, Richard J. Measurement of internal dark current in a 17 GHz, high gradient accelerator structure. United States: N. p., 2019. Web. doi:10.7910/DVN/Q4DO2E.
Xu, Haoran, Shapiro, Michael A., & Temkin, Richard J. Measurement of internal dark current in a 17 GHz, high gradient accelerator structure. United States. doi:https://doi.org/10.7910/DVN/Q4DO2E
Xu, Haoran, Shapiro, Michael A., and Temkin, Richard J. 2019. "Measurement of internal dark current in a 17 GHz, high gradient accelerator structure". United States. doi:https://doi.org/10.7910/DVN/Q4DO2E. https://www.osti.gov/servlets/purl/1881438. Pub date:Thu Jun 27 00:00:00 EDT 2019
@article{osti_1881438,
title = {Measurement of internal dark current in a 17 GHz, high gradient accelerator structure},
author = {Xu, Haoran and Shapiro, Michael A. and Temkin, Richard J.},
abstractNote = {We report the measurement of the internal dark current in a 17 GHz, high gradient accelerator cavity and its comparison with theory. The cavities were fabricated from copper and had a sidewall that was either uncoated or coated with diamond-like carbon or TiN. The dark current was monitored by a downstream detector and by detectors behind two small slits made in the cavity side wall. With an increasing gradient, the downstream current increased monotonically, as expected for field emission. The variation of the internal, side dark current was not monotonic but showed the onset of peaks at gradients near 45 and 65 MV/m. These were identified as the N = 2 and N = 1 single point multipactor resonances. The total internal dark current was estimated at ∼15–30 A. The magnitude of the internal dark current and its dependence on the gradient were in good agreement with simulations using the CST code as well as an in-house code. Processing to a higher gradient, ∼90 MV/m, eliminated the N = 2 mode, but the N = 1 mode persisted. The coated sidewall cavities showed the same multipactor resonances as the uncoated structure. However, at the highest gradient achieved in testing, the coated structures showed a modest reduction in the internal dark current.},
doi = {10.7910/DVN/Q4DO2E},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {6}
}

Works referencing / citing this record:

Measurement of internal dark current in a 17 GHz, high gradient accelerator structure
journal, February 2019