| Paper |
Title |
Page |
| TUAX04 |
Test of a prototype active damping system for the e-p instability at the LANL PSR
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94 |
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- R. J. Macek, R. C. McCrady, S. B. Walbridge, J. Zaugg
LANL, Los Alamos, New Mexico
- S. Assadi, C. Deibele, S. Henderson, M. A. Plum
ORNL, Oak Ridge, Tennessee
- J. M. Byrd
LBNL, Berkeley, California
- M. T.F. Pivi
SLAC, Menlo Park, California
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Our collaboration from LANL, SNS, LBNL and SLAC has developed and successfully tested a prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability at the Los Alamos Proton Storage Ring (PSR). This system was able to improve the instability threshold (as measured by the RF buncher voltage) by ~30%. Beam leakage into the gap at lower RF buncher voltage and resulting higher growth rates from more trapped electrons is the likely cause of this limitation. We will describe the system configuration and results of several experimental tests of system performance. We will also discuss our studies and analysis of the factors limiting system performance.
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| TUAZ05 |
Comparison of Graphite and Diamond Structured Carbon Stripper Foils under Operational Conditions at the Los Alamos PSR
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112 |
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- T. Spickermann, M. J. Borden, R. J. Macek
LANL, Los Alamos, New Mexico
- C. S. Feigerle
University of Tennessee, Knoxville, Tennessee
- R. W. Shaw
ORNL, Oak Ridge, Tennessee
- I. Sugai
KEK, Ibaraki
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In the Los Alamos Proton Storage Ring H–Ions merge with circulating protons in a bending magnet and are stripped of their two electrons in a carbon stripper foil. The circulating protons continue to interact with the foil. Despite efforts to minimize the number of these foil hits, like “painting” of the vertical phase space, they can not totally be eliminated. As a result foil heating and radiation damage limit the lifetime of these foils. In recent years LANL has collaborated with KEK to improve the graphite foils in use at PSR and these foils now last typically for two months. Recently an alternative in the form of diamond structured carbon foils has been proposed for use at SNS. Depending on the grain size these are referred to as microcrystalline or nanocrystalline foils. Both types have been tested in PSR, with quite different results. While the microcrystalline foil failed catastrophically before production beam currents were reached the nanocrystalline foil was successfully used in normal operation for several weeks. Advantages of the diamond foil concept as well as some noteworthy differences that we observed with respect to the LANL graphite foils will be discussed here.
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| THAW04 |
Experimental Characterization of the “1st Pulse” e-p Instability at the LANL PSR
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311 |
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- R. J. Macek, A. A. Browman, D. H. Fitzgerald, R. C. McCrady, T. Spickermann, J. Zaugg
LANL, Los Alamos, New Mexico
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A puzzling aspect of the e-p instability at PSR is the so called “1st Pulse” instability phenomenon. It shows up on the first beam pulse after a period (10 to 30 minutes or more) of beam off time. This pulse has a significantly lower threshold than subsequent beam pulses that follow with the standard time separation. While the standard PSR operation for Lujan Center operation is unaffected by this phenomenon, it does interfere with some high intensity, single pulse experiments using PSR beam. We will summarize the present experimental data characterizing this phenomenon as compared with the typical e-p instability observed at higher repetition rates at PSR and discuss some possible explanations.
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