ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source is designed to produce 1.4 MW of beam power on a mercury target produced in short (1 μSec) pulses at 60 Hz with a 1 GeV beam. Since the initial beam operations in Oct. 2006, the Spallation Neutron Source has operated production runs with beam power up to 520 kW. Apart from equipment issues, the primary challenge in power ramp up is beam loss. Suspected causes of observed beam loss will be discussed. While not contributing to beam loss at present operational parameters, evidence of collective effects is seen at higher intensities, and will be presented. Other issues of interest at high intensity include foil survivability, and maintaining acceptable power density on the neutron production target
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
The Japan Proton Accelerator Research Complex (J-PARC) consists of Linac, 3-GeV rapid cycling synchrotron (RCS) and 50-GeV main ring synchrotron (MR). The J-PARC has been beam-commissioned since November 2006. The Linac and RCS have recently completed initial tunings of the basic parameters, and are now in transition from commissioning to operation and also to the challenging phase for aiming at the higher current operation. The MR also has recently started initial tunings in the storage mode. In this talk, the current status of the J-PARC beam commissioning will be outlined together with experimental data obtained in the actual beam tuning procedures.
CERN, Geneva
With LHC coming into operation very soon an upgrade plan for the whole CERN accelerator complex has been proposed to allow full exploitation of the LHC potential in the future as well as giving increased support to traditional and possible new experiments at lower beam energies. This plan foresees replacing during the period 2011 - 2017 all the accelerators in the LHC injector chain (Linac2, Booster, PS) by new machines (Linac4, SPL and PS2) except for the last - the SPS. In this scenario the SPS should be able to reliably accelerate twice higher beam intensity than achieved so far and therefore significant improvements to the machine performance, in addition to the increased injection energy due to PS2, should be found and implemented at the same time scale. The present status of proposals and ongoing studies for all accelerator injector chain is described with main emphasis on the SPS challenges and upgrade plans.
Fermilab, Batavia, Illinois
Project X is a concept for an intense 8 GeV proton source that provides beam for the Fermilab Main Injector and an 8 GeV physics program. The source consists of an 8 GeV superconducting linac that injects into the Fermilab Recycler where multiple linac beam pulses are stripped and accumulated. The 8 GeV linac consists of a low energy front end possibly based on superconducting technology and a high energy end composed of ILC-like cryomodules.
EPFL, Lausanne
CERN, Geneva
BNL, Upton, Long Island, New York
Since 2003, single bunches of protons with high intensity and low longitudinal emittance have been observed to suffer from heavy losses in less than one synchrotron period after injection in the CERN Super Proton Synchrotron (SPS) when the vertical chromaticity is corrected. This fast instability does not limit the current performance of the SPS, but would be a major limitation in case of an anticipated upgrade of the SPS, which requires bunches of 4·1011 protons (p). Besides, the characteristics of this instability are also complementary indicators of the value of the SPS beam coupling impedance. MOSES analytical calculations, HEADTAIL macroparticle tracking simulations, as well as several measurement campaigns in the SPS indicate that this instability may be due to a coupling between transverse modes ‘-2’ and ‘-3’. The aim of this contribution is to report improvements of the SPS impedance model used by HEADTAIL simulations, and to find out more characteristics of the measured instability in order to assess whether the observed instability in the SPS is indeed a Transverse Mode Coupling Instability (TMCI).
GSI, Darmstadt
In the talk we report on an extensive experimental campaign performed at GSI on the SIS18 synchrotron. We measured the evolution of beam properties over 1 second storage of several beams for several working points in the vicinity of a machine resonance. With this data we benchmark our code predictions and test the understanding of the underlying beam degradation mechanisms.
KEK, Ibaraki
The J-PARC Main Ring should provide high beam power with strict limitation of the particle losses during the operation, including the injection and acceleration processes,caused by the machine imperfections and the space charge effects. The linear coupling resonance [1,1,43] has been identified as the most serious resonance for the MR operation, which leads to significant particle losses during the injection process. Effect of the sextupole resonances, caused by the machine imperfection, is much smaller. The 4th order resonances, mainly 4Qx, 4Qy and 2Qx-2Qy, excited by the space charge of the low energy beam, lead to additional particle losses. The correction procedure to minimize the effect of the sum coupling resonance [1,1,43] by using four independent skew quadrupole magnets has been studied. The particle losses for different machine operation scenario have been estimated, including the injection and acceleration processes. The study of the combined effect of the MR imperfections and the space charge of the beam with moderate beam power has been performed by using the PTC_ORBIT code, installed for the KEK super computer HITACHI SR11000.
CERN, Geneva
Recent developments relative to the injection and storage of the 160 MeV Linac4 high brightness beam for LHC into the CERN PS Booster are reviewed. This talk reports simulations made with the Orbit code. Focus is on H- charge exchange injection and following beam emittance evolution at 160 MeV. Injection is done via a painting scheme for optimal shaping of the initial particle distribution. Next, benchmarking of Orbit and Accsim simulations with measurements performed in the PS Booster on a stored beam at 160 MeV are discussed.
ORNL, Oak Ridge, Tennessee
Operating at 0.5 MW beam power on target, the Spallation Neutron Source (SNS) is already the world's most powerful pulsed neutron source. However, we are only one third of the way to full power. As we ramp toward full power, the control of the beam and beam loss in the ring will be critical. In addition to practical considerations, such as choice of operating point, painting scheme, and rf bunching, it may be necessary to understand and mitigate collective effects due to space charge, impedances, and electron clouds. In dedicated high intensity beam study shifts, we have already observed resistive wall, impedance driven, and electron cloud activity. The analysis and simulation of this data are important ongoing activities at SNS. This talk will discuss the status of this work, as well as other considerations necessary to the successful full power operation of SNS.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Presently, it runs at beam powers of 0.2 MW, with upgrades in place to supply increased powers for the new Second Target Station. Studies are also underway for major upgrades in the megawatt regime. Underpinning this programme of operations and upgrades is a study of the high intensity effects that impose the limitations on beam power. This paper summarises work looking at the key topics of half integer resonance, image effects and injection painting under high space charge conditions, plus progress on overall machine modelling. A core aim of the work is to experimentally confirm simulations and theory, therefore progress on modelling the machine in both operational and specially configured modes is reported. Closely related diagnostics studies are also described, as is initial work on instabilities. Finally, future plans are summarised.
CERN, Geneva
In the CERN Proton Synchrotron (PS), a slow beam loss of few percents is still observed on the long injection flat-bottom with the nominal beam for LHC after fine tuning of the working point. The understanding of space-charge effects is therefore of paramount importance to try and alleviate this limitation. This is why controlled benchmarking space-charge experiments were performed in the last few years. The results are presented in detail with a particular emphasis on the maximum achievable space-charge tune shift with long lifetime. On the contrary, space-charge effects usually play a minor role in high-energy machines like the CERN Super Proton Synchrotron (SPS). However, they could potentially become a limitation for the heavy ion beams needed for the LHC. Therefore, experimental studies on space-charge limitations were also performed in the SPS in the last few years. The results are discussed in detail in the present paper. Furthermore, it is worth mentioning that observations similar to the ones measured in the PS in the presence of space-charge were also measured in the SPS with electron cloud.
CIAE, Beijing
PSI, Villigen
Abstract: Space charge effects play an important role in high intensity cyclotrons, as the most important collective effects. For cyclotrons with small turn separation, single bunch space charge effects are not the only contribution. The interaction of radially neighboring bunches are also present but their effect has, in greater detail, not yet been investigated. In this paper, for the first time, a new PIC based self-consistent numerical simulation model is presented, which covers neighboring bunch effects and is implemented in a three-dimensional object-oriented parallel code OPAL-cycl, a flavor of the OPAL framework. Apart from the full 3D tracking mode with space charge, the code is also capable to do single particle tracking and betatron tune calculation for ordinary cyclotron machine design. We present simulation results from the PSI 590 MeV Ring cyclotron in the light of the ongoing high intensity upgrade program, with the goal of 1.8 MW CW on target. We will also compare calculations with measurements from the Ring cyclotron.
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.
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.
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.
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.
Fermilab, Batavia, Illinois
Since January 2008 Fermilab's Main Injector has switched from 2 to 10 batch slip Stacking as an upgrade to 400 KW operation at 120 GeV. Currently the beam power has reached 350 KW and efforts are continuing in order to reach 400 KW. The current performance and the future plans for reaching 700 KW will be described.
KEK, Ibaraki
Beam commissioning of J-PARC Main Ring (MR) has been started in May, 2008. The 3-GeV beams extracted from the rapid cycling synchrotron (RCS) are injected into the MR and captured by rf, and then extracted to a 3-GeV beam dump. In this paper, we present results of the first-stage commissioning run from May to June 2008. After five months shutdown for installation of fast extraction and slow extraction devices, the second-stage commissioning run will be started in December 2008.
Fermilab, Batavia, Illinois
Fermilab plans to boost the power of Main Injector beam to about 2 MW by building a new SC 8 GeV linac. Its H- beam will be strip injected and accumulated in upgraded Recycler ring, and then transferred to Main Injector for further acceleration to 120 GeV. Beam physics issues related to high intensity operation of Recycler ring and Main Injector are considered.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
ISIS is the world’s most productive spallation neutron source, at the Rutherford Appleton Laboratory in the UK. Presently, it runs at beam powers of 0.2 MW, with upgrades in place to supply increased powers for the new Second Target Station due to start operation in 2008. This paper outlines favoured schemes for major upgrades to the facility in the megawatt regime, with options for 1, 2 and 5 MW. The ideas centre around new 3.2 GeV RCS designs that can be employed to increase the energy of the existing ISIS beam to provide powers of ~1 MW or, possibly as a second upgrade stage, accumulate and accelerate beam from a new 0.8 GeV linac for 2-5 MW beams. Summaries of ring designs are presented, along with studies and simulations to assess the key loss mechanisms that will impose intensity limitations. Important factors include injection, RF systems, instabilities, longitudinal and transverse space charge.
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.