| Paper |
Title |
Other Keywords |
Page |
| TUBX05 |
Cures for beam instabilities in the CERN SPS and their limitations
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synchrotron, emittance, feedback, injection |
153 |
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- E. N. Shaposhnikova
CERN, Geneva
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The LHC beam in the SPS is unstable with a threshold almost an order of magnitude below the nominal intensity. The cures used to stabilise this beam against coupled bunch instabilities apart from beam feedback, feed-forward and longitudinal damping, include a fourth harmonic RF system and controlled emittance blow-up. The limitations of the two last methods were studied experimentally and are analysed here from the point of view of beam quality requirements at extraction and future intensity increases up to ultimate value.
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| WEBZ01 |
Correction of unevenness in Recycler beam profile
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feedback, synchrotron, impedance, proton |
244 |
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- K. Y. Ng, J. L. Crisp, M. Hu
Fermilab, Batavia, Illinois
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When a beam is confined between two rf barriers in the Fermilab Recycler Ring, it is observed that the longitudinal beam profile between the barriers is in general very uneven (typically about 20% for a beam of intensity 5E11). This leads to the consequence that the momentum-mined antiproton bunches may have an intolerable variation in bunch intensity. It is shown that the observed unevenness in beam profile is the result of a tiny amount (around 2%) of rf potential imperfection and a tiny amount (around 0.5%) of rf beam loading. The beam profile can be made even by feeding back the unevenness of the effective rf potential to the low-level rf.
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| THAY07 |
SC Spoke Cavity
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linac, proton, ion, hadron |
337 |
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- M. P. Kelly
ANL, Argonne, Illinois
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Superconducting (SC) TEM-class spoke cavities have been an area of active research during the past decade with application to cw and pulsed ion linacs required for proposed facilities world-wide. Single- and multi-spoke geometries have been developed for use with ions over the full mass range and with velocities 0.2 < v/c < 0.8. Spoke cavities for this range, generally designed for 4 K operation, have several advantages over 2 K elliptical-cell cavities stemming mostly from the lower operating frequency. However, recent spoke-cavity results in 2 K operation, based on new and evolving cavity processing techniques such as clean assembly and hydrogen degassing, show very low rf losses even for high surface fields (EPEAK ~30 MV/m) required in operations. 2K results indicate even higher voltage gains per cavity with reduced heat loads are possible. Other implications of 2 Kelvin spoke cavity operation for ion linacs are discussed.
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