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.
LANL, Los Alamos, New Mexico
University of Tennessee, Knoxville, Tennessee
TRIUMF, Vancouver
ORNL, Oak Ridge, Tennessee
KEK, Ibaraki
At the 39th ICFA Advanced Beam Dynamics Workshop HB 2006 we reported on first results of a test of nanocrystalline diamond foils developed at ORNL under operational conditions at the Los Alamos Proton Storage Ring (PSR). We have continued these tests during the 2006 and 2007 run cycles and have been able to compare the diamond foils with the foils that are normally in use in PSR, which were originally developed by Sugai at KEK. We have gathered valuable information regarding foil lifetime, foil related beam loss and electron emission at the foil. Additional insight was gained under unusual beam conditions where the foils are subjected to higher temperatures. In the 2007 run cycle we also tested a Diamond-like-Carbon foil developed at TRIUMF. A Hybrid-Boron-Carbon foil, also developed by Sugai, is presently in use with the PSR production beam. We will summarize our experience with these different foil types and offer an outlook for future foil activities at PSR.
ORNL, Oak Ridge, Tennessee
We have performed 3D particle tracking in realistic magnetic field configuration to study particle losses in the SNS ring injection dump beam line and beam profile tilt in the extraction Lambertson septum. The technique is based on accurate 3D modeling of magnet assemblies or beam lines and 3D particle trajectory calculations through the simulated field. The studies have discovered a number of design and operation issues that cause particle losses in the injection region and beam profile tilt through the extraction septum. The remedies to all the problems are also devised. This paper reports our simulation techniques and major findings.
ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
ORNL, Oak Ridge, Tennessee
Beam loss is higher than expected in the Ring injection section and in the injection dump beam line. The primary causes are fairly well understood, and we have made some equipment modifications to reduce the loss. In the ring extraction beam line the beam distribution exhibits cross-plane coupling (tilt), and the cause has been traced to a large skew-quadrupole component in the extraction Lambertson septum magnet. In this talk we will discuss the issues surrounding the ring injection and extraction systems, the solutions we have implemented to date, and our plans for future improvements.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
The 3 GeV RCS(Rapid Cycling Synchrotron) of J-PARC(Japan Protron Accelerator Research Complex) is already in the beam commissioning stage and as designed working as an injector to the 50-GeV MR(Main Ring) as well as delivering stable beam to the spallation neutron target. The overall design strategy together with beam commissioning results of the injection and extraction will be presented.
ORNL, Oak Ridge, Tennessee
With the increase of average power of present and future high intensity proton rings and rapid progress of laser technology, laser-assisted stripping become a real alternative for carbon foils that are used for charge-exchange injection. High efficiency laser stripping, achieved experimentally at Spallation Neutron Source in Oak Ridge, TN, paved the way to full scale devices of such type. This paper presents overview of machines and choices of parameters for future powerful accelerators with possible laser stripping use.
Fermilab, Batavia, Illinois
The Fermilab Project X R&D program is focused on the design of a new proton source utilizing a superconducting linac to accelerate H-minus ions to 8 GeV (K.E) for injection and accumulation into the permanent magnet Recycler ring. The initial linac runs at a 5 Hz rep-rate with a 1 ms pulse length and 9 mA average current which produce a beam power of 360 kW at 8 GeV. This beam power will provide 2.3 MW at 120 GeV from the Main Injector in addition to 200 kW at 8 GeV for an 8 GeV physics program. The challenges faced with the transport and injection of 8 GeV H- will be discussed. The topics will include uncontrolled beam losses and their mitigation in both the transport and injection processes, injection stripping options, and transverse phase space painting options. A review of the issues that have been highlighted and addressed by numerous authors will be presented. The current plans for continued R&D on H- stripping mechanisms and techniques and in collimation and absorber design will be outlined and initial concepts of the design will be discussed. Upgrade plans for Project X call for a 2 MW facility at 8 GeV. The additional challenges faced in the upgrade will be outlined.
KEK, Ibaraki
University of Tennessee, Knoxville, Tennessee
ORNL, Oak Ridge, Tennessee
At the 39th ICFA HB2004 workshop and the EPAC-2006 conference, we reported the lifetime and properties of the HBC (Hybrid type Boron-mixed Carbon) foils, a newly developed material, measured by the use of a 3.2 MeV Ne+ ion beam, which deposits significant energy in the foil due to the heavy ion. The content reported showed superior durability against high temperature damage due to foil deformation, thickness reduction and pinhole production at 1700 ± 100K compared with the cluster foils made by the CADAD method. This time, we measured the lifetime of the HBC-foils and the high quality nanocrystalline diamond foils including commercially available foils at 1800 ± 100K which induces the high temperature damage. The measurements were performed by using the KEK-650 keV high intensity H- and DC beam, which generates the same energy deposition as the RCS of J-PARC. In this workshop, we report the results obtained.
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.
CERN, Geneva
The PS2, foreseen as a replacement of the CERN PS, is designed as a racetrack shaped machine with two long straight sections (LSS) for injection/extraction and RF, respectively. Two injection and three extraction systems are required, and in the present study are designed to fit in either a six-cell FODO or a seven-cell DOFO insertion, with a central triplet in order to fit the complete H- injection in one long drift. This study covers the optimisation of the LSS optics and the arrangement and characteristics of the various insertion elements. The main focus lies on the H- injection embedded in the triplet cell with the design of the chicane and painting bump according to the limits of Lorentz-stripping, excited H0 behaviour and the focusing effects of the chicane dipoles on the overall optics.