UMD, College Park, Maryland
Beam halo is one of the major limiting factors to the effective transport of intense beams. In this paper, we use the WARP particle-in-cell code to numerically investigate the effect of different initial particle distributions on the properties of mismatch-induced halo. In particular, we use equilibrium and non-equilibrium distributions, the latter prompted by experimental measurements of the beam distribution in the University of Maryland Electron Ring (UMER). In both cases, we observe the phase space structure expected in the case of resonances between beam envelope oscillations and single-particle trajectories.
CERN, Geneva
UPC, Barcelona
A 50 GeV proton synchrotron machine to replace the current PS (PS2) is foreseen in the framework of the LHC complex upgrade. For high intensity beams, losses constitute a great concern in terms of hands-on maintenance and radioactivation. To minimize the uncontrolled losses all around the ring a collimation system is required. Lattice design and collimation studies are carried out in parallel in order to optimize the cleaning efficiency. To this end the robustness of the system is tested for different lattice configurations against orbit errors and optics distortions.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
A 3GeV Rapid-Cycling Synchrotron (RCS) in Japan Proton Accelerator Research Complex (J-PARC) has been commissioned since September 2007. The most important issue in the beam study is to reduce unnecessary beam loss and to keep the beam line clean for the sake of maintenance and upgrade of the machines. From experience of the former accelerators, the average beam loss should be kept at an order of 1 watt per meter for hands-on maintenance. Since it is very difficult to control the beam loss at such a low level, the only measure we can take is to localize any of the losses in a restricted area, where deliberate modules should be provided for quick coupling and remote handling in order to mitigate the personal doses. Accordingly, we have designed the beam collimation system for the purpose of the beam loss localization. We report the performance of the beam collimation system of RCS through the first commissioning results and the residual doses around RCS components.
Fermilab, Batavia, Illinois
Slip stacking injection for high intensity operation of the Fermilab Main Injector produces a small fraction of beam which is not captured in buckets and accelerated. A collimation system has been implemented with a thin primary collimator to define the momentum aperture at which this beam is lost and four massive secondary collimators to capture the scattered beam. The secondary collimators define tight apertures and thereby capture a fraction of other lost beam. The system was installed in 2007 with commissioning continuing in 2008. The collimation system will be described including simulation, design, installation, and commissioning. Successful operation and operational limitations will be described.
IHEP Beijing, Beijing
The Rapid Cycling Synchrotron of the China Spallation Neutron Source is a high intensity proton machine, with the accumulated particles of 1.9*1013. The injection by the H- stripping method is performed in one of the four long uninterrupted dispersion-free straight-sections. The phase space painting technique is used for all the three phase planes to alleviate the space charge effects. In order to reduce the beam loss during the injection, the transverse and longitudinal halo of the linac beam is collimated in the Linac Ring Beam Transport line. The transverse beam halo collimation is based on a method of using periodic triplet cells and foil scrapers, which has the advantages of low beam loss in the beam line, deep halo collimation allowing almost no H- particles missing the injection foil, and possible proton applications of the scraped beam halo. A new simulation code SCOMT has also been developed to tackle the transfer, conversion and multiple scattering of the mixed H-, H0 and proton beams in the beam line. The large momentum spread of the linac beam is reduced by a debuncher and the longitudinal beam halo is collimated by a momentum collimator in the bending section.
ORNL, Oak Ridge, Tennessee
Since the start of neutron production in October of 2006, the average beam power level has increased from ~ 5 kW to over 500 kW. This increased has been realized by increases in the beam current, pulse length and repetition rate. Equipment issues encountered during this ramp-up will be discussed along with mitigation efforts. A major concern in the power ramp up has been minimization of uncontrolled beam loss. The beam loss levels, loss reduction efforts, and experience levels with residual activation will be discussed. Also the operational run cycles will be discussed, with an evolution in emphasis from beam-studies to neutron production.
CERN, Geneva
The Large Hadron Collider (LHC) will collide two protons beam with an energy of 7 TeV each. The stored energy and intensity exceeds the quench level of the superconducting magnets and the damage level of the machine components by far. Therefore a robust and reliable collimation system is required which controls the losses to the superconducting magnets below the quench limit and to protect the accelerator components from damage in the event of beam loss. The layout and design of the LHC collimation system is presented and the expected system performance is shown. The calculated losses around the ring were provided as input for energy deposition studies in the cleaning insertions itself but also close to experimental insertions. In addition the results from studies on proton losses originating from p-p interaction in the experiments are shown.
BNL, Upton, Long Island, New York
ORNL, Oak Ridge, Tennessee
The charge to this working group was the following:
- Summarize the state of the art in H- charge-exchange injection.
- Summarize recent developments and future possibilities for novel injection techniques.
- Summarize the problems encountered, the needs for further development and improvements in injection and extraction of high-intensity beams.
- Summarize the state-of-the art in collimation system design.
- Summarize the status of benchmarking of collimation system efficiency and performance.