GSI, Darmstadt
The FAIR accelerator project at GSI should increase the intensity of primary proton and heavy ion beams by up to two orders of magnitude, relative to the existing GSI facility. In addition to the design of the new synchrotrons and storage rings, the intensity upgrade of the existing UNILAC linac and SIS-18 synchrotron plays a key role for the FAIR project. In order to reach the FAIR design beam parameters several challenges related to operation with high brightness, high current beams in SIS-18 and in the new SIS-100 have to mastered. Important issues are
- the minimization of beam loss caused by space charge induced resonance crossing and the identification of appropriate working points.
- The control of coherent beam instabilities in the presence of space charge, image currents and different ring impedance sources.
- Beam quality conservation during the rf cycle.
- The control of dynamic vacuum pressure during operation with medium charge state heavy ions.
Fermilab, Batavia, Illinois
If large enough the beam space charge strongly affects the beam stability in a circular accelerator. It results in a separation of coherent and incoherent tunes and, consequently, instability. Effects of space charge on the beam stability are considered in application to Fermilab Booster, Main injector and Recycler.
GSI, Darmstadt
The head-tail instability is a well known intensity limitation for hadron bunches in synchrotrons. The instability has been observed in several synchrotrons and storage rings. Also for the FAIR synchrotrons the head-tail instability represents a potential intensity limitation. In the SIS-18 and SIS-100 synchrotrons space charge effects together with image currents play an important role for the determination of the instability threshold. In this work we study head-tail modes using 3D particle simulations for SIS100 beam parameters. The unstable modes are driven by the resistive wall impedance. Space-charge and image currents are taken into account. The possibility to include space charge into long-term simulations, which are necessary for head-tail instability studies, is investigated using the HEADTAIL code and the PATRIC code, developed at GSI. Potential instability cures will be discussed.
Fermilab, Batavia, Illinois
Understanding the behavior of high-intensity beams in the Fermilab Main Injector is crucial for the future physics program at the lab. Simulations of the Main Injector including collective effects are a crucial part of this understanding. We are building up a set of integrated simulations of collective effects using the Synergia accelerator simulation framework. As a step in this work we present simulations of space-charge effects combined with impedance effect in the Main Injector.
BNL, Upton, Long Island, New York
A strong interest in running RHIC at low energies in a range of 2.5-25 GeV/nucleon total energy of a single beam has emerged recently. Providing collisions in this energy range, which in RHIC case is termed “low-energy” operation, will help to answer one of the key questions in the field of QCD about existence and location of critical point on the QCD phase diagram. To evaluate the challenges of RHIC operation at such low energies there have been several short test runs during RHIC operations in 2006, 2007 and 2008. The beam lifetime observed during the test runs was clearly limited by machine nonlinearities. This performance can be improved provided sufficient time is given for machine development at these low energies. After the lifetime caused by nonlinearities is improved the strongest limitation comes from transverse and longitudinal Intra-beam Scattering (IBS), and ultimately by the space-charge limit. A significant luminosity improvement can be provided with electron cooling applied directly in RHIC at low energies. This report summarizes various beam dynamics limiting effects and possible improvement with electron cooling.
LBNL, Berkeley, California
We present electron-cloud build-up simulations for the FNAL Main Injector at the location of the RFA electron detector. By comparing our simulated results against measurements for various bunch intensities and beam fill patterns, we determine the likely value of the peak secondary emission yield. We then extrapolate our results to higher intensities, within the range contemplated by the proposed MI upgrade program. We predict a substantial increase of the electron cloud density relative to its present value. We consider two values of the RF frequency, namely 53 and 212 MHz, and compare the electron cloud density for these two frequencies at fixed total beam intensity. We contrast the MI results against those from a similar simulation for the PS2, the first storage ring in the proposed future upgrade of the LHC injector complex. Time permitting, we will briefly comment on effects from the electron cloud on the beam dynamics.
GSI, Darmstadt
Resonant effects caused by space charge may occur in circular as well as linear accelerators for high intensity. In the present work we focus on the so-called space charge structure resonances in 2D approximation, where the driving force is induced by space charge only (emittance exchange, fourth and sixth order structure resonances) and show that they can be described by a common class of scaling laws. A distinctive feature is the presence or absence of trapping of particles, which is also reflected in the power of the scaling law. An important requirement is the fully self-consistent modeling, which describes correctly the evolution of beam core as well as halo.
IUCF, Bloomington, Indiana
Fermilab, Batavia, Illinois
Scaling laws of the emittance growth factor (EGF) for a beam crossing the 6th order systematic space-charge resonances and the random 4th order resonance driven by octupoles are obtained by numerical multi-particle simulations. These scaling laws can be used in setting the minimum acceleration rate, and the maximum tolerable resonance strength for the design of non-scaling fixed-field alternating gradient (FFAG) accelerators.
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.
BNL, Upton, Long Island, New York
NSCL, East Lansing, Michigan
CERN, Geneva
Isochronous cyclotrons, rings for precise nuclear mass spectrometry, and some isochronous-optics light sources with extremely short bunches are operated or proposed to be operated in the isochronous or almost isochronous regime. Also, many hadron synchrotrons run in the isochronous regime for a short period of time each acceleration cycle during transition crossing. The longitudinal motion is “frozen” in the isochronous regime that leads to accumulation of the integral of the longitudinal space charge force. In low-gamma hadron machines, this can cause a fast growth of the beam energy spread even at modest beam intensities. In this paper, I discuss specifics of space charge in the isochronous regime and present experimental results obtained in the Small Isochronous Ring, developed at Michigan State University specifically for studies of space charge in the isochronous regime.
UMD, College Park, Maryland
Space charge can significantly affect the resonant properties of rings. The University of Maryland Electron Ring is a scaled experiment in which we have circulated beams with unprecedented intensities. Here we discuss the resonance analysis performed using the electrostatic particle-in-cell code WARP, to understand the effect of space charge on the ring resonances. Beams with varying degrees of space charge in both the emittance- and space-charge-dominated regimes are attempted. The operating point is scanned to map the tune diagram under various lattice and injection errors. The results of the simulation study are compared to experimental measurements.
Fermilab, Batavia, Illinois
The stable region of the Fermilab Booster beam in the complex coherent-tune-shift plane appears to have been shifted far away from the origin by its intense space charge making Landau damping appear impossible. However, it is shown that the bunching structure of the beam reduces this space-charge shift. As a result, the beam can be stabilized by suitable octupole driven tune spread.
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.
Tech-X, Boulder, Colorado
KEK, Ibaraki
At low current, accelerators are dominated by their independent, separated-function magnets, and hence essentially all accelerator simulation codes have used not time but longitudinal distance, s, as the independent variable. The simulation of space-charge effects within this approach has been at best ad hoc, as it requires a (thoroughly approximate) transformation between a pancake of space charge at fixed s to a particle bunch at fixed t. We shall describe recent modifications to the accelerator simulation code PTC [1] that make it possible to, in effect, perform time-based particle tracking in a code that correctly handles the full geometry and wide dynamic range of current designs for FFAGs. In addition, we shall describe the associated space-charge computation and present initial results from simulations that cover a large energy gain in a model non-scaling FFAG.
[1] E. Forest, Y. Nogiwa, F. Schmidt, "The FPP and PTC Libraries", Proceedings of ICAP 2006.
ANL, Argonne, Illinois
Fermilab, Batavia, Illinois
Large-scale beam dynamics simulations are important in accelerator design and optimization. With the new BG/P supercomputer installed at ANL, tera-scale computing can be easily accessed. In order to make use of this emerging technology to increase the speed and efficiency of accelerator simulations, we have systematized and upgraded our software. In this paper, we will first introduce the new version of the parallel beam dynamic code PTRACK [1] updated to run on BG/P with more than 104 processors. The new PTRACK includes possibility to track ~100,000,000 particles through multiple accelerator seeds in the presence of machine errors. An example of SNS linac simulations will be presented.
[1]. J. Xu, B. Mustapha, V.N. Aseev and P.N. Ostroumov, “Parallelization of a beam dynamics code and ***”, Physics Review Special Topic-Accelerator and Beams 10, 014201, 2007.
ORNL, Oak Ridge, Tennessee
GSI, Darmstadt
The 4ν=1 resonance of a linac is found when the depressed tune is around 90 deg. It is observed that this fourth order resonance is dominating over the better known envelope instability and practically replacing it. Simulation study shows a clear emittance growth by this resonance and its stopband. Experimental measurement of the stopband of this resonance is proposed and conducted in 2008 using the UNILAC at GSI. This study will serve as an excellent benchmarking.
SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
RIKEN/RARF/CC, Saitama
RIKEN Nishina Center, Wako, Saitama
ANL, Argonne, Illinois
The accelerator complex for RIBF factory in RIKEN consists of the four ring cyclotrons with an injector linac. It can boost the energy of output beams from the linac up to 440 MeV/nucleon for light ions and 350 MeV/nucleon for very heavy ions. The first beam from the accelerator complex was successfully extracted at the end of 2006. An 28GHz SC-ECR ion source will be installed at the front end of the injector linac on a 100kV HV platform to increase the beam intensity of very heavy ions such as uranium. Beam dynamics from the ion source to the exit of the injector were simulated using TRACK. How much space charge forces affect on beam qualities in the successive ring cyclotrons will be discussed.
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.
ORNL RAD, Oak Ridge, Tennessee
ORNL, Oak Ridge, Tennessee
Space charge effect has an impact on emittance measurement of low energy H- ion beam injected into the SNS RFQ. This paper presents numerical investigations of space charge effect of the beam on transverse emittance measurement using an Allison style scanner attached to the front-end test stand at SNS. The investigations are based on mathematical modelling the emittance measurement by the scanner taking into account space charge of the beam. We present a method of emittance data analysis that includes the modelling and allows more accurate measurements of the emittance. We also give an example of the emittance measurement with the scanner applying the developed method.
ORNL, Oak Ridge, Tennessee
Charged-particle beam diagnostic devices such as wire scanners and wire harps provide data sets describing the one-dimensional density distributions at a particular location; these data are commonly called profile data. We use these data for further computations, usually beam properties such as position and size. Typically these data require subjective, human, processing to extract meaningful results; this is inefficient and labor intensive. Our ultimate goal is to automate these computations, at least streamline the process. If we hope to implement any type of automation we must make real world considerations. Specifically, we consider information content, noise in the data, and sampling theory. Within this framework we create a general model for the data sets. Using signal processing techniques we identify the minimal sampling requirements for maintaining information content. Using Bayesian analysis we identify the most probable Gaussian signal within the data. We present the major obstacles currently faced concerning robust automation techniques.
TRIUMF, Vancouver
GSI, Darmstadt
CERN, Geneva
32 papers were presented. Rather than summarizing each one individually, we give a few highlights, conditioned by the items in the working group charge, namely:
- Summarize the state of the art in simulation capabilities. What developments are needed?
- Summarize the state of the art in theory. What developments are needed?
- Summarize recent developments in benchmarking experimental data with simulations. What critical experiments and diagnostic developments are needed to further refine the theory and simulations?
- Summarize the state of the art in instability mitigation techniques. What further technology developments are needed?
- Summarize the primary limitations to beam intensity in existing circular machines.
- Summarize the key beam dynamics questions for high-intensity circular machines
- Summarize opportunities for advancing the field.