| Paper |
Title |
Page |
| MOCP04 |
LHC Upgrade Options and CARE-HHH Activities
|
49 |
| |
- F. Zimmermann
CERN, Geneva
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| |
The European Accelerator Network on High Energy High Intensity Hadron Beams (CARE HHH) is developing scenarios for luminosity and energy upgrades of the Large Hadron Collider (LHC). The LHC upgrade options under consideration differ in terms of beam parameters, electron-cloud effects, beam-beam compensation, use of crab cavities, and interaction-region layout. Complementary investigations concern injector upgrades, novel magnet technologies, advanced collimation schemes, and ultimate intensity limitations. Flanking these upgrade studies, an accelerator-physics code web repository has been set up, and an extensive simulation-code benchmarking campaign is being prepared.
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| TUAX03 |
Beam loss, emittance growth and halo formation due to the pinched electron cloud
|
84 |
| |
- E. Benedetto, F. Zimmermann
CERN, Geneva
- G. Franchetti
GSI, Darmstadt
- K. Ohmi
KEK, Ibaraki
|
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| |
Electron cloud can cause beam losses and emittance growth in proton or positron storage rings. If the electron density exceeds a certain threshold value, a strong head-tail instability manifests itself, characterized by a rapid beam-size blow-up with a rise time comparable to the synchrotron period. However, even for densities below the coherent-instability threshold, the electron-cloud can give rise to a significant emittance growth. We identified the mechanism for this incoherent growth as one caused by the combined effect of the beam particles synchrotron motion and the longitudinal variation of the tune shift, which is proportional to the pinched electron-cloud distribution along the bunch. This can give rise to the periodic crossing of a resonance, in analogy to halo formation in space-charge dominated beams, or eventually, if the tune shift is sufficiently large, to the crossing of bunch regions where the single-particle motion is linearly unstable.
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| TUBX06 |
Betatron Tune Shift due to Nonlinear Resistive-Wall Wake Field
|
159 |
| |
- F. Zimmermann
CERN, Geneva
|
|
| |
I present formulae for the coherent and incoherent tune shifts of a single bunch traveling between two parallel resistive plates. It is shown that for the parameters of an LHC prototype collimator in the SPS, both the nonlinear wake-field components, calculated by Piwinski, and the correct time dependence, e.g., as derived by Burov and Lebedev, must be taken into account.
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| WEBY04 |
Refined Models of Intrabeam Scattering
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265 |
| |
- F. Zimmermann, F. Ruggiero
CERN, Geneva
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| |
We discuss two extensions of intrabeam-scattering theory. First, starting from the Bjorken-Mtingwa recipe, general formulae are derived for the three electro-magnetic intrabeam scattering growth rates, including non-ultrarelativistic terms and vertical dispersion, but maintaining a Gaussian beam approximation. A few applications demonstrate the importance of the vertical dispersion. Second, aside from electromagnetic interactions, hadrons may also undergo nuclear scattering off each other. We estimate the magnitude of this process, and argue that the loss rate due to “nuclear intrabeam scattering” could become significant in high-energy proton or ion storage rings, such as the LHC.
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| THBW02 |
Electron-Cloud Benchmarking & CARE-HHH Codes
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350 |
| |
- F. Zimmermann
CERN, Geneva
|
|
| |
The state-of-the-art in code benchmarking for various types of electron-cloud simulations is reviewed. In particular, we recall possible meanings of benchmarking, summarize past and more recent code comparisons, present examples of code verifications against machine experiments, describe some remaining uncertainties, and formulate a few goals for the future. The code-benchmarking effort is supported by the CARE-HHH initiative on accelerator physics simulation codes, whose other objectives include a common web repository and the practical extension of simulation codes.
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|
| FRAP01 |
SUMMARY OF WORKING GROUP A AND A+B+D JOINT SESSION
|
358 |
| |
- F. Zimmermann
CERN, Geneva
- A. V. Burov
Fermilab, Batavia, Illinois
|
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| |
We summarize the presentations and discussions of the HB2006 Working Group A, devoted to beam instabilities, and of the joint session of Working Groups A, B (on space charge), and D (beam cooling and experiments). First we review the progress on conventional instabilities and impedances, and then the advances on electron cloud.
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| FRAP08 |
Summary of General Working Group A+B+D with a Focus on Code Benchmarking
|
379 |
| |
- J. Wei
BNL, Upton, Long Island, New York
- I. Hofmann
GSI, Darmstadt
- E. N. Shaposhnikova, F. Zimmermann
CERN, Geneva
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