| Paper |
Title |
Other Keywords |
Page |
| TUAX06 |
Electron cloud and single-bunch instabilities in the Relativistic Heavy Ion Collider
|
electron, vacuum, emittance, ion |
117 |
| |
- J. Wei, M. Bai, M. Blaskiewicz, P. Cameron, R. Connolly, A. Della Penna, W. Fischer, H.-C. Hseuh, H. Huang, R. C. Lee, R. J. Michnoff, V. Ptitsyn, T. Roser, T. Satogata, S. Tepikian, S. Y. Zhang
BNL, Upton, Long Island, New York
- U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- L. Wang
SLAC, Menlo Park, California
| |
Electron cloud is one of the leading mechanisms that limit the performance of high intensity circular accelerators and colliders. Electron cloud in RHIC is in an intermediate regime sharing features of both the long-bunch (PSR) and short-bunch (photon factories) machines. Vacuum-pressure rises, transverse tune shifts, and electron flux are observed at injection, upon transition crossing, and at top energy. Transverse emittance growth, fast instabilities, and beam loss also occur upon transition crossing. Mitigation measures are implemented both to reduce the production of electron cloud and to control the beam stability. This paper summarizes the observation and initial analysis of the electron-cloud effects at RHIC.
|
|
|
|
| TUAY05 |
Application of the extreme value theory to estimate beam loss in an ion linac, using large scale Monte Carlo simulations
|
linac, quadrupole, simulation, beam-transport |
107 |
| |
- R. Duperrier, D. Uriot
CEA, Gif-sur-Yvette
| |
The influence of random perturbations of high intensity accelerator elements on the beam losses is considered. This paper presents the error sensitivity study which has been performed for the SPIRAL2 linac in order to define the tolerances for the construction. The proposed driver aims to accelerate a 5 mA deuteron beam up to 20 A. MeV and a 1 mA ion beam for q/A = 1/3 up to 14.5 A. MeV. It consists in an injector (two ECRs sources + LEBTs with the possibility to inject from several sources + Radio Frequency Quadrupole) followed by a superconducting section based on an array of independently phased cavities where the transverse focalization is performed with warm quadrupoles. The correction scheme and the expected losses are described. The Extreme Value Theory is used to estimate the expected beam losses. The described method couples large scale computations to obtain probability distribution functions. The bootstrap technique is used to provide confidence intervals associated to the beam loss predictions. With such a method, it is possible to measure the risk to loose a few watts in this high power linac (up to 200 kW).
|
|
|
|
| TUAZ02 |
High-Intensity Beam Collimation and Targetry
|
collimation, target, proton, radiation |
74 |
| |
- N. V. Mokhov
Fermilab, Batavia, Illinois
| |
Principles, design criteria and realization are described for reliable collimation systems for the high-power accelerators (Fermilab Booster and Main Injector, SNS, J-PARC), hadron colliders (Tevatron and LHC) and e+e- linear colliders (ILC). Factors affecting the expected and achieved collimation performances are analyzed. Functionality of collimators as the key elements of the machine protection system are considered using as an example a recent beam accident case in the Tevatron. A substantial progress on the crystal collimation front is described. The key issues are considered in design of high-power target systems and achieving their best performance. Simulation code requirements and recent benchmarking results are presented. A status of conventional neutrino targets and neutrino factory target concepts is described along with performed and planned beam tests. Overview of the target and collimator material beam tests concludes this report.
|
|
|
|
| TUAZ05 |
Comparison of Graphite and Diamond Structured Carbon Stripper Foils under Operational Conditions at the Los Alamos PSR
|
proton, injection, radiation, electron |
112 |
| |
- 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
| |
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.
|
|
|
|
| TUBZ01 |
The Beam Diagnostics System for J-PARC Synchrotrons
|
proton, injection, electron, pick-up |
128 |
| |
|
|
| WEAX01 |
Resonance trapping due to space charge and synchrotron motion, in theory, simulations, and experiments
|
resonance, emittance, synchrotron, space-charge |
167 |
| |
- G. Franchetti, I. Hofmann
GSI, Darmstadt
| |
With the development of high intensity accelerator, the role of space charge effect in a nonlinear lattice gained special attention, as in the FAIR project at GSI, where long term storage of high intensity beams is required. The simultaneous presence of space charge and a nonlinear lattice creates an unprecedented challenge for ring designers as well as a new area of studies in beam physics. We present our understanding of the effect of space charge and chromaticity on the nonlinear beam dynamics of a bunched beam.
|
|
|
|
| WEAY02 |
Electron cooling of 8 GeV antiprotons at Fermilab’s Recycler: Results and operational implications
|
electron, antiproton, emittance, extraction |
182 |
| |
- L. R. Prost, D. R. Broemmelsiek, A. V. Burov, K. Carlson, C. Gattuso, M. Hu, T. K. Kroc, J. R. Leibfritz, S. Nagaitsev, S. M. Pruss, G. W. Saewert, C. W. Schmidt, A. V. Shemyakin, M. Sutherland, V. Tupikov, A. Warner
Fermilab, Batavia, Illinois
| |
Electron cooling of 8 GeV antiprotons at Fermilab’s Recycler storage ring is now routinely used in the collider operation. It requires a 0.1-0.5 A, 4.3 MeV DC electron beam that reduces the longitudinal phase-space of the circulating antiproton beam. This paper first describes the characteristics of the electron beam that was achieved to successfully cool antiprotons as well as its necessary stability. Then, results from various cooling force measurements along with comparison to a simple non-magnetized model will be presented. Finally, operational aspects of the implementation of electron cooling at the Recycler will be discussed, such as regulation of the cooling rate and the influence of the electron beam on the antiprotons lifetime.
|
|
|
|
| WEAZ01 |
Overview of beam loss mechanisms in injection and extraction
|
injection, extraction, linac, emittance |
172 |
| |
|
|
| WEAZ03 |
DESIGN AND TESTS OF A LOW-LOSS MULTI-TURN EJECTION FOR THE CERN PS
|
extraction, septum, kicker, emittance |
192 |
| |
- M. Giovannozzi
CERN, Geneva
| |
Following the positive results of the three-year measurement campaign at the CERN Proton Synchrotron, the study of a possible implementation of the proposed multi-turn extraction based on beam splitting with stable islands in the transverse phase space was undertaken. A substantial reduction of beam losses, with respect to the present extraction scheme, should be achieved with the proposed technique when delivering the high-intensity proton beams required for the planned CERN Neutrino to Gran Sasso Project. Major modifications to the ring layout are foreseen, such as a new design of the extraction bumps including also the installation of three additional kickers to create a closed-bump over the five turns used to extract the split beam. The ring aperture was reviewed and improvements are proposed to reduce possible beam losses between beam splitting and extraction. The goal consists of implementing the proposed changes by beginning of 2008 and to commission the novel extraction during the 2008 PS physics run.
|
|
|
|
| WEAZ05 |
Very Fast Beam Losses at HERA, and what has been done about it
|
power-supply, luminosity, quadrupole, interaction-region |
215 |
| |
- K. Wittenburg, M. Werner
DESY, Hamburg
| |
During the Luminosity upgrade of HERA in 2000/2001 more than 50 new magnets were installed close to the interaction region to provide a stronger focussing of the two beams. Some of these magnets are located at very large values of the betatron function and therefore act with a large gain on the beam. Sudden changes in the power supply currents had led to very fast beam losses, creating quenches and increased radiation levels. This talk will discuss the improvements made to the HERA machine protection system to make sure that the beam is dumped in time in case of these events.
|
|
|
|
| WEBY01 |
Commisioning of Electron Beam Cooling at S-LSR
|
electron, ion, proton, feedback |
247 |
| |
- T. Shirai, S. Fujimoto, M. Ikegami, A. Noda, H. Souda, M. Tanabe, H. Tongu
Kyoto ICR, Uji, Kyoto
- H. Fadil, M. Grieser
MPI-K, Heidelberg
- T. Fujimoto, S. I. Iwata, S. Shibuya
AEC, Chiba
- I. N. Meshkov, I. A. Seleznev, A. V. Smirnov, E. Syresin
JINR, Dubna, Moscow Region
- K. Noda
NIRS, Chiba-shi
| |
S-LSR is a new compact ion cooler ring at Kyoto University. The circumference is 22.557 m. The commissioning of the electron cooling was started using the 7 MeV proton beam from November, 2005. The total length of the electron cooler is 1.63 m. In order to maximize the effective cooling length in the limited space, the magnetic field of the solenoid and the troid coils was calculated precisely by the 3D code. The electrostatic deflector for the electron and the steering magnet for the ion are placed in the troid. The performances of these devices are evaluated by the cooling measurements. Experiments using the electron cooling are also stared. One is an induction sweep cooling of the proton beam. It is an cooling with the assist of the induction acceleration and possible to reduce the cooling time of the hot ion beams like secondary particles. We also observe the behavior of the cooled ion beam in the small ion number case and the large ion number case. We discuss about the possibility of the phase transition of the proton in the former case and discuss about the coherent instability conditions in the latter case.
|
|
|
|
| THAZ03 |
Safe LHC Beam Commissioning
|
injection, dumping, extraction, collimation |
306 |
| |
- J. A. Uythoven, R. Schmidt
CERN, Geneva
| |
Due to the large amount of energy stored in magnets and beams, safe operation of the LHC is essential. The commissioning of the LHC machine protection system will be an integral part of the general LHC commissioning program. A brief overview of the LHC Machine Protection System will be given, identifying the main components: the Beam Interlock System, the Beam Dumping System, the Collimation System, the Beam Loss Monitoring system and the Quench Protection System. An outline is given of the commissioning strategy of these systems during the different commissioning phases of the LHC: without beam, injection and the different phases with stored beam depending on beam intensity and beam energy.
|
|
|
|
| THAZ04 |
Commissioning and Operational Scenarios of the LHC Beam Loss Monitor System
|
collimation, simulation, superconducting-magnet, ion |
314 |
| |
- E. B. Holzer
CERN, Geneva
| |
One of the most critical elements for the protection of CERN’s Large Hadron Collider (LHC) is its beam loss monitoring (BLM) system. It aims to prevent the super conducting magnets from quenching and to protect the machine components from damages, as a result of critical beam losses. The contribution will discuss the commissioning procedures of the BLM system and the envisaged operational scenarios. About 4000 monitors will be installed around the ring. The specification for the BLM system includes a factor of 2 absolute precisions on the prediction of the quench levels, a wide range of integration times (100 us to 100 s) and a fast (one turn) trigger generation. When the loss rate exceeds a pre-defined threshold value, a beam abort is requested. Magnet quench and damage levels vary as a function of beam energy and loss duration. Consequently, the beam abort threshold values vary accordingly. By measuring the loss pattern, the BLM system helps to identify the loss mechanism. Furthermore, it will be an important tool for commissioning, machine setup and studies. Special monitors will be used for the setup and control of the collimators.
|
|
|
|
| FRAP02 |
Summary of Working Gropu B
|
space-charge, simulation, resonance, linac |
363 |
| |
- S. M. Cousineau
ORNL, Oak Ridge, Tennessee
|
|
| FRAP03 |
Summary of Working Group C+G (Part I)
|
extraction, target, collimation, injection |
365 |
| |
- N. V. Mokhov
Fermilab, Batavia, Illinois
- K. Hasegawa
JAEA, Ibaraki-ken
- S. Henderson
ORNL, Oak Ridge, Tennessee
- R. Schmidt
CERN, Geneva
- M. Tomizawa
KEK, Ibaraki
- K. Wittenburg
DESY, Hamburg
|
|