| Paper |
Title |
Page |
| TUPCH145 |
The MUCOOL RF Program
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1358 |
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- J. Norem
ANL, Argonne, Illinois
- A. Bross, A. Moretti, B. Norris, Z. Qian
Fermilab, Batavia, Illinois
- D. Li, S.P. Virostek, M.S. Zisman
LBNL, Berkeley, California
- R.A. Rimmer
Jefferson Lab, Newport News, Virginia
- R. Sandstrom
DPNC, Genève
- Y. Torun
IIT, Chicago, Illinois
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Efficient muon cooling requires high RF gradients in the presence of high (~3T) solenoidal fields. The Muon Ionization Cooling Experiment (MICE) also requires that the x-ray production from these cavities is low, in order to minimize backgrounds in the particle detectors that must be located near the cavities. These cavities require thin Be windows to ensure the highest fields on the beam axis. In order to develop these cavities, the MUCOOL RF Program was started about 6 years ago. Initial measurements were made on a six-cell cavity and a single-cell pillbox, both operating at 805 MHz. We have now begun measurements of a 201 MHz pillbox cavity. This program has led to new techniques to look at dark currents, a new model for breakdown and a general model of cavity performance based on surface damage. The experimental program includes studies of thin Be windows, conditioning, dark current production from different materials, magnetic-field effects and breakdown. We will present results from measurements at both 805 and 201 MHz.
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| TUPCH146 |
The Interactions of Surface Damage on RF Cavity Operation
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1361 |
| |
- J. Norem, A. Hassanein, Z. Insepov
ANL, Argonne, Illinois
- A. Bross, A. Moretti, Z. Qian
Fermilab, Batavia, Illinois
- D. Li, M.S. Zisman
LBNL, Berkeley, California
- R.A. Rimmer
Jefferson Lab, Newport News, Virginia
- D.N. Seidman, K. Yoon
NU, Evanston, Illinois
- Y. Torun
IIT, Chicago, Illinois
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Studies of low frequency RF systems for muon cooling has led to a variety of new techniques for looking at dark currents, a new model of breakdown, and, ultimately, a model of RF cavity operation based on surface damage. We find that cavity behavior is strongly influenced by the spectrum of enhancement factors on field emission sites. Three different spectra are involved: one defining the initial state of the cavity, the second determined by the breakdown events, and the third defining the equilibrium produced as a cavity operates at its maximum field. We have been able to measure these functions and use them to derive a wide variety of cavity parameters: conditioning behavior, material, pulse length, temperature, vacuum, magnetic field, pressure, gas dependence. In addition we can calculate the dependence of breakdown rate on surface field and pulse length. This work correlates with data from Atom Probe Tomography. We will describe this model and new experimental data.
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