dorsal/arxiv
View SchemaField Emission in CEBAF's Superconducting RF Cavities and Implications for Future Accelerators
| Authors | Jay Benesch |
|---|---|
| Categories | |
| ArXiv ID | physics/0606141 |
| URL | https://arxiv.org/abs/physics/0606141 |
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.
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"abstract": "Field emission is one of the key issues in superconducting RF for particle\naccelerators. When present, it limits operating gradient directly or via\ninduced heat load at 2K. In order to minimize particulate contamination of and\nthus field emission in the CEBAF SRF cavities during assembly, a cold ceramic\nRF window was placed very close to the accelerating cavity proper. As an\nunintended consequence of this, the window is charged by field-emitted\nelectrons, making it possible to monitor and model field emission in the CEBAF\ncavities since in-tunnel operation began. From January 30, 1995, through\nFebruary 10, 2003, there were 64 instances of spontaneous onset or change in\ncavity field emission with a drop in usable gradient averaging 1.4 (sigma 0.8)\nMV/m at each event. Fractional loss averaged 0.18 (sigma 0.12) of pre-event\ngradient. This event count corresponds to 2.4 events per century per cavity, or\n8 per year in CEBAF. It is hypothesized that changes in field emission are due\nto adsorbed gas accumulation. The possible implications of this and other\nobservations for the International Linear Collider (ILC) and other future\naccelerators will be discussed.",
"arxiv_id": "physics/0606141",
"authors": [
"Jay Benesch"
],
"categories": [
"physics.acc-ph"
],
"title": "Field Emission in CEBAF\u0027s Superconducting RF Cavities and Implications for Future Accelerators",
"url": "https://arxiv.org/abs/physics/0606141"
},
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