Beams Document 3614-v1

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Instability Study in the Recycler

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Submitted by:
Lionel R. Prost
Updated by:
Lionel R. Prost
Document Created:
21 May 2010, 07:51
Contents Revised:
21 May 2010, 11:59
Metadata Revised:
21 May 2010, 12:02
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Instabilities have been observed in the Recycler during the extraction proces for large stashes when under relatively strong cooling.
Here, we summarize a set of measurements which aim was to measure the instabilities phase density threshold under various RF configuration close to those use during the extraction process. Because the instability phase density threshold is sensitive to the pbars distribution, we rely on the tomography analysis to extract the longitudinal emittance of the cooled beam. It also allows a true comparison between very different RF configuration.
From these measurements we conclude that the 'mined bucket' stage is the most prone to go unstable while the 'cold beam' configuration is very robust. Although some quantitative results show that the model is adequate to describe the instabilities in the Recycler, more measurements are needed to refine our understanding of the instability limits.
At the same time, we identify a couple of possible ways to increase the instability limit. For instance, by changing the chromaticity during the last stages of extraction or modifying the RF structure so as to minimize the 'zero-potential' length between the bunches to be extracted and the remaining mined bunches.
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Referenced by:
  • Beams-doc-604: Increasing the Range of Recycler IBEAM
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