| Paper |
Title |
Page |
| MOPCH161 |
Development of a Prototype Superconducting CW Cavity and Cryomodule for Energy Recovery
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436 |
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- P.A. McIntosh, C.D. Beard, D.M. Dykes, B. Todd
CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
- S.A. Belomestnykh
Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
- A. Buechner, P. Michel, J. Teichert
FZR, Dresden
- J.M. Byrd, J.N. Corlett, D. Li
LBNL, Berkeley, California
- T. Kimura, T.I. Smith
Stanford University, Stanford, Califormia
- M. Liepe, V. Medjidzade, H. Padamsee, J. Sears, V.D. Shemelin
Cornell University, Ithaca, New York
- D. Proch
DESY, Hamburg
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Energy Recovery LINAC (ERL) and LINAC-driven FEL proposals and developments are now widespread around the world. Superconducting RF (SRF) cavity advances made over the last 10 years for TESLA/TTF at 1.3 GHz, in reliably achieving accelerating gradients >20 MV/m, suggest their suitability for these ERL and FEL accelerators. Typically however, photon fluxes are maximised from the associated insertion devices when the electron bunch repetition rate is as high as possible, making CW-mode operation at high average current a fundamental requirement for these light sources. Challenges arise in controlling the substantial HOM power and in minimizing the power dissipated at cryogenic temperatures during acceleration and energy recovery, requiring novel techniques to be employed. This paper details a collaborative development for an advanced high-Qo cavity and cryomodule system, based on a modified TESLA cavity, housed in a Stanford/Rossendorf cryomodule. The cavity incorporates a Cornell developed resistive-wall HOM damping scheme, capable of providing the improved level of HOM damping and reduced thermal load required.
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| TUPCH133 |
Comparison of Measured and Calculated Coupling between a Waveguide and an RF Cavity Using CST Microwave Studio
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1328 |
| |
- J. Shi, H. Chen, S. Zheng
TUB, Beijing
- D. Li
LBNL, Berkeley, California
- R.A. Rimmer, H. Wang
Jefferson Lab, Newport News, Virginia
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Accurate predications of RF coupling between an RF cavity and ports attached to it have been an important study subject for years for RF coupler and higher order modes (HOM) damping design. We report recent progress and a method on the RF coupling simulations between waveguide ports and RF cavities using CST Microwave Studio in time domain (Transit Solver). Comparisons of the measured and calculated couplings are presented. The simulated couplings and frequencies agree within ~ 10% and ~ 0.1% with the measurements, respectively. We have simulated couplings with external Qs ranging from ~ 100 to ~ 100, 000, and confirmed with measurements. The method should also work well for higher Qs, and can be easily applied in RF power coupler designs and HOM damping for normal-conducting and superconducting cavities.
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| TUPCH145 |
The MUCOOL RF Program
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1358 |
| |
- 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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| TUPCH148 |
201 MHz Cavity R&D for MUCOOL and MICE
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1367 |
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- D. Li, S.P. Virostek, M.S. Zisman
LBNL, Berkeley, California
- A. Bross, A. Moretti, B. Norris
Fermilab, Batavia, Illinois
- J. Norem
ANL, Argonne, Illinois
- H.L. Phillips, R.A. Rimmer, M. Stirbet
Jefferson Lab, Newport News, Virginia
- M. Reep, D.J. Summers
UMiss, University, Mississippi
- Y. Torun
IIT, Chicago, Illinois
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We describe the design, fabrication and preliminary testing of the prototype 201 MHz copper cavity for a muon ionization cooling channel. Application of the cavity includes the Muon Ionization Cooling Experiment (MICE) as well as cooling channels for a neutrino factory or a muon collider. This cavity was developed by the US MUCOOL collaboration and is being tested in the MUCOOL Test Area (MTA) at Fermilab. In order to achieve a high accelerating gradient, the cavity beam irises are terminated by a pair of curved, thin beryllium windows. Several of the fabrication methods developed for this cavity and the windows are novel and offer significant cost savings compared to conventional construction methods. Cavity thermal and RF performance will be compared to FEA modeling predictions. RF commissioning results will be presented.
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