Field Emission in CEBAF's SRF Cavities and Implications for Future Accelerators
Abstract
Field emission is one of the key issues in superconducting RF for particle accelerators. When present, it limits operating gradient directly or via induced heat load at 2K. In order to minimize particulate contamination of and thus field emission in the CEBAF SRF cavities during assembly, a cold ceramic RF window was placed very close to the accelerating cavity proper. As an unintended consequence of this, the window is charged by field-emitted electrons, making it possible to monitor and model field emission in the CEBAF cavities since in-tunnel operation began. From January 30, 1995, through February 10, 2003, there were 64 instances of spontaneous onset or change in cavity field emission with a drop in usable gradient averaging 1.4 ({sigma} 0.8) MV/m at each event. Fractional loss averaged 0.18 ({sigma} 0.12) of pre-event gradient. This event count corresponds to 2.4 events per century per cavity, or 8 per year in CEBAF. It is hypothesized that changes in field emission are due to adsorbed gas accumulation. The possible implications of this and other observations for the International Linear Collider (ILC) and other future accelerators will be discussed.
- Authors:
- Publication Date:
- Research Org.:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Org.:
- USDOE - Office of Energy Research (ER)
- OSTI Identifier:
- 876130
- Report Number(s):
- JLAB-ACP-05-463; DOE/ER/40150-3743
TRN: US0600998
- DOE Contract Number:
- AC05-84ER40150
- Resource Type:
- Journal Article
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 43 PARTICLE ACCELERATORS; ACCELERATORS; CAVITIES; CERAMICS; CONTAMINATION; ELECTRONS; FIELD EMISSION; LINEAR COLLIDERS; MONITORS; PARTICULATES; WINDOWS
Citation Formats
Benesch, Jay. Field Emission in CEBAF's SRF Cavities and Implications for Future Accelerators. United States: N. p., 2006.
Web.
Benesch, Jay. Field Emission in CEBAF's SRF Cavities and Implications for Future Accelerators. United States.
Benesch, Jay. 2006.
"Field Emission in CEBAF's SRF Cavities and Implications for Future Accelerators". United States. https://www.osti.gov/servlets/purl/876130.
@article{osti_876130,
title = {Field Emission in CEBAF's SRF Cavities and Implications for Future Accelerators},
author = {Benesch, Jay},
abstractNote = {Field emission is one of the key issues in superconducting RF for particle accelerators. When present, it limits operating gradient directly or via induced heat load at 2K. In order to minimize particulate contamination of and thus field emission in the CEBAF SRF cavities during assembly, a cold ceramic RF window was placed very close to the accelerating cavity proper. As an unintended consequence of this, the window is charged by field-emitted electrons, making it possible to monitor and model field emission in the CEBAF cavities since in-tunnel operation began. From January 30, 1995, through February 10, 2003, there were 64 instances of spontaneous onset or change in cavity field emission with a drop in usable gradient averaging 1.4 ({sigma} 0.8) MV/m at each event. Fractional loss averaged 0.18 ({sigma} 0.12) of pre-event gradient. This event count corresponds to 2.4 events per century per cavity, or 8 per year in CEBAF. It is hypothesized that changes in field emission are due to adsorbed gas accumulation. The possible implications of this and other observations for the International Linear Collider (ILC) and other future accelerators will be discussed.},
doi = {},
url = {https://www.osti.gov/biblio/876130},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}