HU/AdSM, Higashi-Hiroshima, Japan
Hiroshima University, Higashi-Hiroshima, Japan
PPPL, Princeton, New Jersey, USA
A recently developed novel perturbative Hamiltonian transformation method which allows the determination of approximate matched kinetic quasi-equilibrium solutions for an intense charged particle beam propagating through a periodic focusing quadrupole lattice is presented.* Using this method we have identified numerically the class of self-consistent periodic kinetic 'equilibria' for intense beam propagation in alternating-gradient focusing systems, and extended the nonlinear perturbative particle simulation method to intense beam propagation in such systems. The new method has been implemented in the nonlinear perturbative particle-in-cell code BEST which is used to study properties of the newly constructed beam 'equilibria'. The results of these studies are presented and analyzed in detail.
* E.A. Startsev, R.C. Davidson and M. Dorf, Phys. Rev. ST Accel. Beams 13, 064402 (2010).
BNL, Upton, Long Island, New York, USA
CERN, Geneva, Switzerland
CINVESTAV, Mérida, Mexico
A major concern for the implementation of crab crossing in a future high-luminosity LHC (HL-LHC) is machine protection in an event of a fast crab-cavity failure. Certain types of abrupt crab-cavity phase and amplitude changes are simulated to characterize the effect of failures on the beam and the resulting particle-loss signatures. The time-dependent beam loss distributions around the ring and particle trajectories obtained from the simulations allow for a first assessment of the resulting beam impact on LHC collimators and on sensitive components around the ring. The simulation results are used to derive tolerances on the maximum rate of change in crab-cavity phase and amplitude which can be allowed with regard to machine safety.
BNL, Upton, Long Island, New York, USA
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
JAI, Oxford, United Kingdom
The international Muon Ionization Cooling Experiment (MICE), under construction at the Rutherford Appleton Laboratory in Oxfordshire (UK), is a test of a prototype cooling channel for a future Neutrino Factory. The experiment aims to achieve, using liquid hydrogen absorbers, a 10% reduction in transverse emittance, measured to an accuracy of 1% by two scintillating fibre trackers within 4 T solenoid fields. Step IV of MICE will begin in 2012, producing the experiment's first cooling measurements. Step IV uses an absorber focus coil module, placed between the two trackers, to house liquid hydrogen or solid absorbers. The performance of Step IV using various absorber materials was simulated. Multiple scattering in high Z absorbers was found to mismatch the beam with the lattice optics, which was largely corrected by re-tuning the MICE lattice accordingly.
MIT/PSFC, Cambridge, Massachusetts, USA
We present the design of an overmoded photonic band gap (PBG) accelerator cavity, made from a 2D lattice of sapphire rods supported between copper plates, that operates in a TM02-like mode at 17 GHz. The cavity does not support the lower-frequency TM01-like mode. Higher-order modes are damped effectively by removing rods from the lattice so that only the operating mode is supported with a high quality factor. The TM02 cavity mitigates the high pulsed heating of the copper surface seen in some metal-rod TM01 PBG cavities, which may be an advantage for high-gradient operation. We discuss plans for testing a 17 GHz TM02 standing-wave cavity at gradients above 100 MV/m.
JLAB, Newport News, Virginia, USA
Muons, Inc, Batavia, USA
BNL, Upton, Long Island, New York, USA
Recirculating Linear Accelerators (RLA) are an efficient way of accelerating short-lived muons to multi-GeV energies required for Neutrino Factories and TeV energies required for Muon Colliders. To reduce the number of required return arcs, we employ a Non-Scaling Fixed-Field Alternating-Gradient (NS-FFAG) arc lattice design. We present a complete linear optics design of a muon RLA with two-pass linear NS-FFAG droplet return arcs. The arcs are composed of symmetric cells with each cell designed using combined function magnets with dipole and quadrupole magnetic field components so that the cell is achromatic and has zero initial and final periodic orbit offsets for both passes’ energies. Matching to the linac is accomplished by adjusting linac quadrupole strengths so that the linac optics on each pass is matched to the arc optics. We adjust the difference of the path lengths and therefore of the times of flight of the two momenta in each arc to ensure proper synchronization with the linac. We investigate the dynamic aperture and momentum acceptance of the arcs.
UCLA, Los Angeles, California, USA
BNL, Upton, Long Island, New York, USA
Particle Beam Lasers, Inc., Northridge, California, USA
A racetrack muon ring cooler for a muon collider is considered. The achromatic cooler uses both dipoles and solenoids. We describe the ring lattice and show the results of beam dynamic simulation that demonstrates a large aperture for acceptance. We also examine the 6D cooling of the muon beam in the cooler and discuss the prospects for the future.
UCLA, Los Angeles, California, USA
BNL, Upton, Long Island, New York, USA
Particle Beam Lasers, Inc., Northridge, California, USA
We present a four-sided ring cooler that employs both dipoles and solenoids to provide robust 6D muon cooling of large emittance beams in order to design and build a muon collider. Our studies show strong 6D cooling adequate for components of a muon collider front end.
UCLA, Los Angeles, California, USA
BNL, Upton, Long Island, New York, USA
It is widely believed that a neutrino factory would deliver unparallel performance in studying neutrino mixing and would provide tremendous sensitivity to new physics in the neutrino sector. Here we will describe and simulate the front-end of the neutrino factory system, which plays critical role in determining the number of muons that can be accepted by the downstream accelerators. In this system, a proton bunch on a target creates secondaries that drift into a capture transport channel. A sequence of rf cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to nearly equal central energies, and initiates ionization cooling. For this, the muon beams are transported through sections containing high-gradient cavities and strong focusing solenoids. In this paper we present results of optimization and variation studies toward obtaining the maximum number of muons for a neutrino factory by using a compact transport channel.
Stratakis et al. Phys. Rev. ST Accel. Beams 14, 011001 (2011).
IIT, Chicago, Illinois, USA
UCR, Riverside, California, USA
BNL, Upton, Long Island, New York, USA
Recent progress in six-dimensional (6D) cooling simulations for the Muon Collider based on the RFOFO ring layout is presented. In order to improve the performance of the cooling channel a tapering scheme is studied that implies changing the parameters such as cell length, magnetic field strength, RF frequency, and the amount of the absorbing material along the cooling channel. This approach allows us to keep the cooling rates high throughout the process. The results of the simulations carried out in G4beamline are presented.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
UCR, Riverside, California, USA
IIT, Chicago, Illinois, USA
In the Muon Ionization Cooling Experiment (MICE), muons are cooled by passing through material, then through RF cavities to compensate for the energy loss; which reduces the transverse emittance. It is planned to demonstrate longitudinal emittance reduction via emittance exchange in MICE by using a solid wedge absorber in Step IV. Based on the outcome of previous studies, the shape and material of the wedge were chosen. We address here further simulation efforts for the absorber of choice as well as engineering considerations in connection with the absorber support design.
SLAC, Menlo Park, California, USA
Stanford University, Stanford, California, USA
We present results for the fabrication of a silicon woodpile accelerator structure. The structure was designed to have an accelerating mode at 3.95 μm, with a high characteristic impedance and an accelerating gradient of 530 MeV/m. The fabrication process uses standard nanofabrication techniques in a layer-by-layer process to produce a three-dimensional photonic crystal with 400 nm features. Reflection spectroscopy measurements reveal a peak spanning from three to five microns, and are show good agreement with simulations.
* Sears, PRST-AB, 11, 101301, (2008).
** Cowan, PRST-AB, 11, 011301, (2008).
*** McGuinness, J. Mod. Opt., vol. 56, is. 18, pp. 2142, (2009).
**** Lin, Nature, 394, pp. 251 (1998).
SLAC, Menlo Park, California, USA
Photonic band gap (PBG) fibers with hollow core defects are being designed and fabricated for use as laser driven accelerators because they appear capable of providing gradients of several GeV/m at picosecond pulse lengths. While we expect to have fiber down to 1.5-2.0 micron wavelengths we still lack a viable means for efficient coupling of laser power into these structures. The reasons for this include the very different character of these TM-like modes from those familiar in the telecom field and the fact that the defect must function as both a longitudinal waveguide for the accelerating field and a transport channel for the particles. We discuss the status of our coupling work in terms of what has been done and the options we are pursuing for both end and side coupling. In both basic coupler types, the symmetry of the PBG crystal leads to significant differences between this and the telecom field. We show that side coupling provides more possibilities and is preferred. Our motivation is to test new fiber for gradient, mode content and throughput on the NLCTA at SLAC.
Fermilab, Batavia, USA
CLASSE, Ithaca, New York, USA
Numerous storage ring diagnostic operations require synchronous excitation of beam motion. An example is the lattice phase measurement, which involves synchronous detection of the driven betatron motion. In the CESR storage ring, the transverse tunes continuously vary by several times their natural width. Hence, synchronous beam excitation is impossible without active feedback control. The digital tune tracker consists of a direct digital frequency synthesizer which drives the beam through a transverse kicker, and is phase locked to the detected betatron signal from a quad button position detector. This ensures synchronous excitation, and by setting the correct locking phase, the excitation can be tuned to peak resonance. The fully digital signal detection allows a single bunch amid a long train to be synchronously driven, which allows lattice diagnostics to be performed which include collective effects. The collective effects potentially of interest in CESR include wakefield couplings within the train, and plasma effects such as ion trapping and electron cloud trapping.
JLAB, Newport News, Virginia, USA
With inauguration of the CEBAF Element Database(CED) in Fall 2010, Jefferson Lab computer scientists have taken a first step toward the eventual goal of a model-driven accelerator. Once fully populated, the database will be the primary repository of information used for everything from generating lattice decks to booting iocs to building controls screens. A requirement influencing the CED design is that it provide access to not only present, but also future, and eventually past, configurations of the accelerator. To accomplish this, an introspective database schema was designed that allows new elements, types, and properties to be defined on-the-fly with no changes to table structure. Used in conjunction with Oracle Workspace Manager, it allows users to query data from any time in the database history with the same tools used to query the present configuration. Users can also check-out workspaces to use as staging areas for upcoming machine configurations. All Access to the CED is through a well-documented API that is translated automatically from original C++ into native libraries for script languages such as perl, php, and TCL making access to the CED easy and ubiquitous.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
BNL, Upton, Long Island, New York, USA
We present a lattice design of a CW Electron Recovery Linacs (ERL) for future electron-hadron colliders eRHIC and LHeC. In eRHIC, an six-pass ERL installed in the existing Relativistic Heavy Ion Collider (RHIC) tunnel will collide 5-30 GeV polarized electrons with RHIC’s 50-250 (325) GeV polarized protons or 20-100 (130) GeV/u heavy ions. In LHeC, a stand-along 3-pass 60 GeV CW ERL will collide polarized electrons with 7 TeV protons. After collision, electron beam energy is recovered and electrons are dumped at low energy. Two superconducting linacs are located in the two straight sections in both ERLs. . The multiple arcs are made of Flexible Momentum Compaction lattice (FMC) allowing adjustable momentum compaction for electrons with different energies. The multiple arcs, placed above each other, are matched to the two linacs straight sections with splitters and combiners.
MAX-lab, Lund, Sweden
AMACC, Uppsala, Sweden
CLS, Saskatoon, Saskatchewan, Canada
PPPL, Princeton, New Jersey, USA
LLNL, Livermore, California, USA
Handong Global University, Pohang, Republic of Korea
LANL, Los Alamos, New Mexico, USA
The effect of a weakly coupled periodic lattice in terms of achieving emittance exchange between the transverse and longitudinal directions is investigated using the generalized Courant-Snyder theory for coupled lattices.
* H. Qin, M. Chung, and R. C. Davidson, PRL. 103, 224802 (2009).
** H. Qin and R. C. Davidson, PRST-AB 12, 064001 (2009).
ANL, Argonne, USA
The Advanced Photon Source (APS) is a third-generation storage-ring-based x-ray source that has been operating for more than 13 years and is enjoying a long period of stable, reliable operation. While APS is presently providing state-of-the-art performance to its large user community, we must plan for improvements and upgrades to stay at the forefront scientifically. Significant improvements should be possible through upgrades of beamline optics, detectors, and end-station equipment. In this paper, we discuss the evolutionary changes that are envisioned for the storage ring itself. These include short-pulse x-rays, long straight sections, superconducting undulators, improved beam stability, and higher current. With these and other changes, we anticipate significant improvements in capacity, flux, and brightness, along with the ability to perform unique time-resolved experiments.
LBNL, Berkeley, California, USA
The Advanced Light Source (ALS) at Berkeley Lab is one of the earliest 3rd generation light sources. Over the years substantial upgrades have been implemented to keep the facility at the forefront of soft x-ray sources. The most recent one is a multi-year upgrade, that includes new and replacement x-ray beamlines, a replacement of many of the original insertion devices and many upgrades to the accelerator. The accelerator upgrade that affects the ALS performance most directly is the ALS brightness upgrade, which will reduce the horizontal emittance from 6.3 to 2.2 nm. This will result in a brightness increase by a factor of three for bend magnet beamlines and at least a factor of two for insertion device beamlines and will keep the ALS competitive with newer sources.
LBNL, Berkeley, California, USA
UNAL, Bogota D.C, Colombia
Action and phase orbit correction method is implemented to detect magnetic errors in LHC orbits of late 2009 run. The last achievements in the theory of action and phase jump analysis have been included to reduce action and phase plots noise and to increase precision on the calculation of linear errors. The validation of the implementation is performed by MAD-X simulations of the LHC lattice V6.5, where dipole and quadrupole errors are included and recovered within 0.02%. Then, the implementation is applied to experimental orbits, taken from the 2009 run during November and December, where several interaction regions are analyzed.
orblancog@bt.unal.edu.co, Universidad Nacional de Colombia
jfcardona@unal.edu.co, Professor, Universidad Nacional de Colombia
Texas A&M University, College Station, Texas, USA
A design is being developed to prototype for a dipole for this purpose: a block-coil dipole with 13 T short- sample field, 11 T working field, and 6 cm aperture. The dipole is a natural application of the high-field dipole strategy developed at Texas A&M, using simple pancake windings, flux-plate suppression of low-field multipoles, and bladder preloading. A short model dipole is planned.
BNL, Upton, Long Island, New York, USA
We are designing two electron lenses (E-lens) to compensate for the large beam-beam tune spread from proton-proton interactions at IP6 and IP8 in the Relativistic Heavy Ion Collider (RHIC). They will be installed in RHIC IR10. First, the layout of these two E-lenses is introduced. Then the effects of e-lenses on proton beam are discussed. For example, the transverse fields of the e-lens bending solenoids and the fringe field of the main solenoids will shift the proton beam. For the effects of the e-lens on proton beam trajectory, we calculate the transverse kicks that the proton beam receives in the electron lens via Opera at first. Then, after incorporating the simplified E-lens lattice in the RHIC lattice, we obtain the closed orbit effect with the Simtrack Code.
MAX-lab, Lund, Sweden
SLAC, Menlo Park, California, USA
University of Delhi, Delhi, India
Fermilab, Batavia, USA
BNL, Upton, Long Island, New York, USA
To increase luminosity in the Relativistic Heavy Ion Collider’s (RHIC’s) polarized proton 250 GeV operations, we are considering reducing beta* to 0.65 m at the interaction points (IPs), and increasing bunch intensity. The new working point near the 2/3 integer will used on the ramp to preserve polarization. In addition, we plan to adjust the betatron-phase advances between IP6 and IP8 to (k+1/2)*PI so to lower the dynamic beta-beat from the beam-beam interaction. The effects of all these changes will impact the dynamic aperture, and hence, it must be evaluated carefully. In this article, we present the results of tracking the dynamic aperture with the proposed lattices.
BNL, Upton, Long Island, New York, USA
The NSLS-II magnet multipole specifications were determined based on analysis of nonlinear beam dynamics. The required field quality does not exceed what was specified for the existing third-generation light sources. While the prototype magnets have met these specifications, the magnets from mass production could potentially have bigger errors which exceed certain tolerances. In this paper we discuss the results of recent calculations to provide further insight into the acceptable range of the magnet multipoles based on the physics requirements.
Fermilab, Batavia, USA
LBNL, Berkeley, California, USA
ORNL, Oak Ridge, Tennessee, USA
In this paper we report the effects on beam dynamics from two intrinsic multipole components of a quadrupole magnet – dodecapole and psedu-octupole, in a quadrupole doublet lattice. Weak resonances at transverse phase advances 60°; and 90°; per cell, which may contribute to halo formation and beam loss in a linac, are shown from multi-particle tracking simulations. Although the net effect of the psedu-octupole component alone is very small due to substantial cancellations within the same magnet, its existence may significantly enhance the weak resonances which are induced by the dodecapole component of quadrupole magnets. The combined contributions of these two magnetic field components may not be simply linear-scaled because of the extreme nonlinear nature.
SLAC, Menlo Park, California, USA
Alternative chicane-type beamlines are proposed for exact emittance exchange between horizontal phase space (x,x') and longitudinal phase space (z, delta). Methods to achieve exact phase space exchanges, i.e. mapping x to z, x' to delta, z to x and delta to x' are suggested. Some applications of the phase space exchanger and the feasibility of an emittance exchange experiment with the proposed beamline at SLAC are discussed.
UMD, College Park, Maryland, USA
The University of Maryland Electron Ring (UMER) is a research accelerator designed to operate with extreme space charge. The existence of high-precision experimental measurements of tune, dispersion, chromaticity, response matrix elements, and other parameters*, **, *** has prompted a revision of the models used to describe the machine. Due to the low energy (10 keV) of the electrons, the dipole and quadrupole magnets used are air-core printed-circuit coils whose fields we calculate using a Biot-Savart solver. Different levels of approximations for the magnetic fields have been developed. We present simulation results from the particle-in-cell code WARP, and from the accelerator code, ELEGANT. These are compared both against simpler models as well as experimental results. The improved modeling has significantly reduced the discrepancies between simulation and experiment.
* D.F. Sutter, et al., Proc. PAC 2009
** C. Wu, et al., Proc. PAC 2009
*** S. Bernal, et al., Proc. AAC 2010
ANL, Argonne, USA
Recently there was a situation at the APS when one sextupole power supply failed during top-up operation (all magnets at the APS have separate power supplies). The beam was not lost but the lifetime decreased significantly to the point where it was hard for the injectors to provide enough charge for top-up injections. Luckily, the power supply was able to reset quickly, and the operation was not compromised. One can anticipate similar failures in the future when it would not be possible to reset the power supply. In such a case, the APS would need to operate with lower lifetime until the next intervention period. Here we present an optimization of the sextupole distribution in the vicinity of the failed sextupole that allows us to partially recover the lifetime. A genetic optimization algorithm that involves simultaneous optimization of the dynamic and energy apertures was used*. Experimental tests are also presented.
* M. Borland et al., "Application of Direct Methods of Optimizing Storage Ring Dynamic and Momentum Apertures," Proc. ICAP2009, to be published.
ANL, Argonne, USA
A method that tracks particles directly through a general magnetic field described in a 3D field table was added to the code elegant recently. It was realized by converting an arbitrary particle's motion to a combination of free-drift motion and centripetal motion through the coordinate system rotation and using a general linear interpolation tool developed at the Advanced Photon Source (APS). This method has been tested by tracking particles through conventional magnetic elements (dipole, sextupole, etc.) to verify reference coordinate system conversions, tracking accuracy, and long-term tracking stability. Results show a very good agreement between this new method and the traditional method. This method is not designed to replace mature traditional methods that have been used in most tracking codes. Rather, it is useful for magnets with complicated field profiles or for studying edge effects.
BNL, Upton, Long Island, New York, USA
In this paper we present a multiobjective approach to the dynamic aperture (DA) optimization. Taking the NSLS- II lattice as an example, we have used both sextupoles and quadrupoles as tuning variables to optimize both on-momentum and off-momentum DA. The geometric and chromatic sextupoles are used for nonlinear properties while the tunes are independently varied by quadrupoles. The dispersion and emittance are fixed during tunes variation. The algorithms, procedures, performances and results of our optimization of DA will be discussed and they are found to be robust, general and easy to apply to similar problems.
BNL, Upton, Long Island, New York, USA
Dynamic aperture (DA) optimization with direct particle tracking is a straight forward approach when the computing power is permitted. It can have various realistic errors included and is more close than theoretical estimations. In this approach, a fast and parallel tracking code could be very helpful. In this presentation, we describe an implementation of storage ring particle tracking code TESLA for beam dynamics optimization. It supports MPI based parallel computing and is robust as DA calculation engine. This code has been used in the NSLS-II dynamics optimizations and obtained promising performance.
CLASSE, Ithaca, New York, USA
Cornell University is planning to build an Energy Recovery Linac (ERL) hard x-ray lightsource operating at 5 GeV. Simulations of its approximately 3 km of electron beamline that incorporate a host of reasonable alignment and field errors, and their compensation by an orbit correction scheme, are presented. These simulations start with realistic particle distributions just after injection and track them through acceleration, the production of undulator radiation, deceleration (energy recovery), and finally transport to the beam stop. To this realistic model, single error sources are further added with increasing magnitudes in order to establish alignment and field tolerance estimates.
Fermilab, Batavia, USA
ORNL, Oak Ridge, Tennessee, USA
Nonlinear optics is a promising idea potentially opening the path towards achieving super high beam intensities in circular accelerators. Creation of a tune spread reaching 50% of the betatron tune would provide strong Landau damping and make the beam immune to instabilities. Recent theoretical work* have identified a possible way to implement stable nonlinear optics by incorporating nonlinear focusing elements into a specially designed machine lattice. In this report we propose the design of a test accelerator for a proof-of-principle experiment. We discuss possible studies at the machine, requirements on the optics stability and sensitivity to imperfections.
* V. Danilov and S. Nagaitsev, Phys. Rev. ST Accel. Beams 13, 084002 (2010)
MIT, Cambridge, Massachusetts, USA
Adiabatic thermal equilibrium is an important state of a charged-particle beam. The rigid-rotor thermal beam equilibrium in a uniform magnetic focusing field is established. The equivalent kinetic and warm-fluid theories of adiabatic thermal beam equilibrium in a periodic solenoidal magnetic focusing field are discussed. Good agreement between theories and experiment is found. The warm-fluid theory of adiabatic thermal beam equilibrium in an alternating-gradient quadrupole magnetic focusing field is discussed. For the periodic solenoidal magnetic focusing field, charged-particle dynamics in the adiabatic thermal beam equilibrium are studied numerically and compared with those in the Kapchinskij-Vladimirskij (KV) type beam equilibrium. Numerical evidence is presented, indicating almost complete elimination of chaotic particle motion in the adiabatic thermal beam equilibrium.
PPPL, Princeton, New Jersey, USA
LLNL, Livermore, California, USA
A variety of masks were installed on the Paul Trap Simulator Experiment (PTSX) cesium ion source in order to perform experiments with modified transverse distribution functions. Masks were used to block injection of ions into the PTSX chamber, thereby creating injected transverse beam distributions that were either hollow, apertured and centered, apertured and off-center, or comprising five beamlets. Experiments were performed using either trapped plasmas or the single-pass, streaming, mode of PTSX. The transverse streaming current profiles clearly demonstrated centroid oscillations. Further analysis of these profiles also shows the presence of certain collective beam modes, such as azimuthally symmetric radial modes. When these plasmas are trapped for thousands of lattice periods, the plasma quickly relaxes to a state with an elevated effective transverse temperature and is subsequently stable. Both sinusoidal and periodic step function waveforms were used and the resulting difference in the measured transverse profiles will be discussed.
Tech-X, Boulder, Colorado, USA
BNL, Upton, Long Island, New York, USA
We have benchmarked UAL-SPINK against Zgoubi and a list of well understood spin physics results. Along the way we addressed issues relating to longitudinal dynamics and orbit bump and distortion handling as well as appropriate slicing necessary for the TEAPOT-SPINK spin orbit integrator. We have also ported this TEAPOT-SPINK algorithm to the GPU’s. We present the challenges associated with this work.
USTC/NSRL, Hefei, Anhui, People's Republic of China
Fermilab, Batavia, USA
LBNL, Berkeley, California, USA
CLASSE, Ithaca, New York, USA
Cornell University, Ithaca, New York, USA
Electron cloud buildup is a primary concern for the performance of the damping rings under development for the International Linear Collider. We have performed synchrotron radiation profile calculations for the 6.4-km DC04 and 3.2-km DSB3 lattice designs using the SYNRAD utility in the Bmad accelerator software library. These results are then used to supply input parameters to the electron cloud modeling package ECLOUD. Contributions to coherent tune shifts from the field-free sections and from the dipole and quadrupole magnets have been calculated, as well as the effect of installing solenoid windings in the field-free regions. For each element type, SYNRAD provides ring occupancy, average beam sizes, beta function values, and beta-weighted photon rates for the coherent tune shift calculation. An approximation to the antechamber design has been implemented in ECLOUD as well, moving the photoelectron source point to the edges of the antechamber entrance and removing cloud particles which enter the antechamber.
PPPL, Princeton, New Jersey, USA
BNL, Upton, Long Island, New York, USA
A number of recent machine designs, including ‘‘nano-beams'', sub-millimeter ‘‘low-beta'' IRs, etc., require high accuracy on beam orbit and beam size, reliable evaluation of machine parameters, dynamic apertures, etc. This can only be achieved using high precision simulation tools. Stepwise ray-tracing methods are in this category of tools, stochastic synchrotron radiation and its effects on an electron beam in a storage ring are simulated here in that manner. Benchmarking of the method against analytical model expectations, using a Chasman-Green cell, is presented.
BNL, Upton, Long Island, New York, USA
A model of the Alternating Gradient Synchrotron is being developed based on stepwise ray-tracing numerical tools. It provides a realistic representation of the lattice, and accounts for the two helical partial Siberian snake insertions. The aim is to make this stepwise ray-tracing based model an aid for the understanding of the AGS, in matter of both beam dynamics and polarization transmission.
LBNL, Berkeley, California, USA
This is a feasibility study of using a modern Graphics Processing Unit (GPU) to parallelize the accelerator particle tracking code. To demonstrate the massive parallelization features provided by GPU computing, a simplified TracyGPU program is developed for dynamic aperture calculation. Performances, issues, and challenges from introducing GPU are also discussed.
LBNL, Berkeley, California, USA
As Cloud services gain in popularity for enterprise use, vendors are now turning their focus towards providing cloud services suitable for scientific computing. Recently, Amazon Elastic Compute Cloud (EC2) introduced the new Cluster Compute Instances (CCI), a new instance type specifically designed for High Performance Computing (HPC) applications. At Berkeley Lab, the physicists at the Advanced Light Source (ALS) have been running Lattice Optimization on a local cluster, but the queue wait time and the flexibility to request compute resources when needed are not ideal for rapid development work. To explore alternatives, for the first time we investigate running the Lattice Optimization application on Amazon’s new CCI to demonstrate the feasibility and trade-offs of using public cloud services for science.
Fermilab, Batavia, USA
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
BNL, Upton, Long Island, New York, USA
The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The linac needs to deliver 15 nC in 80 - 150 bunches to the booster every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source. We have developed a scheme to transversely stack two bunch trains in the NSLS-II booster in order to alleviate the charge requirements on the linac. This scheme has been outlined previously. In this paper we show particle tracking simulations of the tracking scheme. We show that the booster lattice has sufficient orbit correction and dynamic aperture at injection to maintain the charge and emittance of the first beam while it circulates waiting for the next train to arrive. We also show simulations of the booster ramp with a stacked beam for a variety of lattice errors and injected beam parameters. In all cases the performance of the proposed stacking method is sufficient to reduce the required charge from the linac. For this reason the injection system of the NSLS-II booster is being designed to include this feature.
UCLA, Los Angeles, California, USA
BNL, Upton, Long Island, New York, USA
Limitations on the maximum achievable accelerating gradient of microwave cavities can influence the performance, length, and cost of particle accelerators. Gradient limitations are widely believed to be initiated by electron emission from the cavity surfaces. Here, we show that field emission is effectively suppressed by applying a tangential magnetic field to the cavity walls, so higher gradients can be achieved. Numerical simulations indicate that the magnetic field prevents electrons leaving these surfaces and subsequently picking up energy from the electric field. Implementation of the proposed concept into prospective particle accelerator applications is studied by two specific examples - a multi TeV lepton-antilepton collider and a linear muon accelerator driver for an intense neutrino source.
Fermilab, Batavia, USA
University of Pune, Pune, India
Shivaji University, Nanomaterials Reasearch Laboratory, Kolhapur, India
BNL, Upton, Long Island, New York, USA
In this article we perform simulation studies to investigate the effects of betatron phase advances between the beam-beam interaction points on half-integer resonance driving terms, second order chromaticity and dynamic aperture in RHIC. The betatron phase advances are adjusted with artificial matrices inserted in the middle of arcs. The lattices for 2011 polarized proton (p-p) run and 2010 RHIC Au-Au runs are used in this study. We also scan the betatron phase advances between IP8 and the electron lens for the proposed Blue ring lattice with head-on beam-beam compensation.
BNL, Upton, Long Island, New York, USA
In this article we will answer the following questions: 1) what is the source of second order chromaticities in RHIC? 2) what is the dependence of second order chromaticity on the on-momentum β-beat? 3) what is the dependence of second order chromaticity on β* at IP6 and IP8? To answer these questions, we use the perturbation theory to numerically calculate the contributions of each quadrupole and sextupole to the first, second, and third order chromaticities. Possible methods to locally reduce chromatic effects in RHIC rings are shortly discussed.
BNL, Upton, Long Island, New York, USA
Beam experiments have been performed in RHIC to determine some key parameters of the RHIC electron lenses, and to test the capability of verifying lattice modifications by beam measurements. We report the status and recent results of these experiments.
BNL, Upton, Long Island, New York, USA
Electron lenses for head-on beam-beam compensation will be installed in IP 10 at RHIC. Compensation of the beam-beam effect experienced at IP 8 requires betatron phase advances of ∆ψ=k·π between the proton-proton interaction point at the IP 8, and the electron lens at IP 10. This paper describes the lattice solutions for both the BLUE and the YELLOW ring to achieve this goal.
Fermilab, Batavia, USA
Requirements and operating conditions for a Muon Collider Ring (MCR) pose significant challenges to superconducting magnets. The dipole magnets should provide a high magnetic field to reduce the ring circumference and thus maximize the number of muon collisions during their lifetime. One third of the beam energy is continuously deposited along the lattice by the decay electrons at the rate of 0.5 kW/m for a 1.5-TeV c.o.m. MCR. Unlike dipoles in proton machines, the MCR dipoles should allow this dynamic heat load to escape the magnet helium volume in horizontal plane predominantly towards the ring center. Two alternative designs, one based on the open mid-plane approach with block type coils and absorber outside the coils, and another based on the traditional large-aperture cos-theta approach with a shifted beam pipe and absorber inside the coil aperture were developed for the MCR designed for a luminosity of 1034 cm-2s−1. This paper presents the analysis and comparison of radiation effects in MCR based on the two dipole magnets. Tungsten masks in the interconnect regions are used in both cases to mitigate the unprecedented dynamic heat deposition and radiation in the magnet coils.
ANL, Argonne, USA
The Advanced Photon Source (APS) is a 7-GeV electron storage ring light source that operates with an effective emittance of 3.1 nm using optics with distributed dispersion. Lower emittance is desirable for some x-ray experiments, but is difficult using conventional optics adjustments because of the required strength of quadrupoles and sextupoles. Changing the damping partition number by changing the rf frequency is another approach, but is incompatible with distributed dispersion because it would require simultaneous realignment of all APS beamlines. In this paper, we evaluate a new approach to changing the damping partition number using a systematic orbit bump in all sectors.
ANL, Argonne, USA
The Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source. Operation for users is delivered at a nominal current of 100 mA in one of three bunch patterns. The APS Upgrade calls for a minimum planned operating current of 150 mA, with an option to deliver beam up to 200 mA. The high-current threshold in the storage ring has been explored, and storage ring components have been identified that either drive collective instabilities or are subjected to excessive beam-drive higher-order-mode (HOM) heating. In this paper, we describe machine studies at 150 mA in a special lattice that simulates the upgraded APS. We also describe the accelerator upgrades that are required to accommodate 200-mA operation, as well as the ongoing machine studies plan.
ANL, Argonne, USA
The Advanced Photon Source (APS) is a 7-GeV storage ring light source that has been in operation for over a decade. In the near future, the ring may be upgraded, including changes to the lattice such as provision of several long straight sections (LSSs). Use of deflecting cavities for generation of short x-ray pulses is also considered. Because APS beamlines are nearly fully built out, we have limited freedom to place LSSs in a symmetric fashion. Arbitrarily placed LSSs will drastically reduce the symmetry of the optics and would typically be considered unworkable. We apply a recently developed multi-objective direct optimization technique that relies on particle tracking to compute the dynamic aperture and Touschek lifetime. We show that this technique is able to tune sextupole strengths and select the working point in such a way as to recover the dynamic and momentum acceptances. We also show the results of experimental tests of lattices developed using these techniques.
BNL, Upton, Long Island, New York, USA
NSLS-II is a third generation light source that is under construction at the Brookhaven National Laboartory. The 3GeV 792m long 30-cell storage ring will be commissioned in 2014. The emittance is lowered from 2nm to 1nm by three 7m damping wigglers. This paper will discuss the future emittance reduction approaches for NSLS-II. One option is installing more damping wigglers; an alternative solution is to manipulate the damping partition by shifting the chromatic quadrupoles horizontally. Both methods can lower the emittance effectively; however, the second method does not occupy the user straights. When the quarupoles are moved, the orbit and thus the vacuum chamber need to be redesigned, and beam dynamics could be affected. In the paper we will compare the lattice properties for the two options, and address the potential issues.
BNL, Upton, Long Island, New York, USA
We propose an upgrade R&D project for NSLSII to generate sub-pico-second short x-ray pulses using laser slicing. In this paper we discuss the basic parameters for this system and present a specific example for a viable design and its performance. Since the installation of the laser slicing system into the storage ring will break the symmetry of the lattice, we demonstrate it is possible to recover the dynamical aperture to the original design goal of the ring.
SLAC, Menlo Park, California, USA
SLAC is investigating long-range options for building a high performance light source machine while reusing the existing linac and PEP-II tunnels. One previously studied option is the PEP-X low emittance storage ring. The alternative option is based on a superconducting Energy Recovery Linac (ERL) and the PEP-X design. The ERL advantages are the low beam emittance, short bunch length and small energy spread leading to better qualities of the X-ray beams. Two ERL configurations differed by the location of the linac have been studied. Details of the lattice design and the results of beam transport simulations with the coherent synchrotron radiation effects are presented
BNL, Upton, New York, USA
The NSLS-II storage ring lattice is comprised of 30 DBA cells arranged in 15 superperiods. There are 15 long straight sections (9.3m) for injection, RF and insertion devices and 15 shorter straights (6.6m) for insertion devices. In the baseline lattice, the short straights have small horizontal and vertical beta functions but the long straights have large horizontal beta function optimized for injection. In this note, we explore the possibility of maintaining three long straights with large horizontal beta function while providing the other 12 long straights with smaller horizontal beta function to optimize the brightness of insertion devices. Our study considers the possible linear lattice solutions as well as characterizing the nonlinear dynamics. Results are reported on optimizations of dynamic aperture required for good injection efficiency and adequate Touschek lifetime.
BNL, Upton, New York, USA
The NSLS-II storage ring lattice is comprised of 30 DBA cells arranged in 15 superperiods. There are 15 long straight sections (9.3m) for injection, RF and insertion devices and 15 shorter straights (6.6m) for insertion devices. In the baseline lattice, the short straights have small horizontal and vertical beta functions but the long straights have large horizontal beta function optimized for injection. In this note, we explore the possibility of installing additional quadrupoles at the center of selected long straight sections in order to provide two low-beta source locations for undulators. The required modification to the linear lattice is discussed as well as the preservation of adequate dynamic aperture required for good injection efficiency and adequate Touschek lifetime.
Hampton University, Hampton, Virginia, USA
Muons, Inc, Batavia, USA
Current and future synchrotron radiation light sources and free electron laser facilities are in need of improvements in Electron Gun Technology, especially regarding the cost and efficiency of photoinjectors. The generation of Surface Acoustic Waves (SAW) on piezoelectric substrates is known to produce strong piezoelectric fields that propagate on the surface of the material. These fields significantly reduce the recombination probability of electrons and holes which can result in enhanced quantum efficiency of photoemission. Additional advantages are provided by the mobility of charge carriers that can be controlled by SAW. It is expected that this novel feature will result in enhanced efficiency of photocathode operation, leading to the production of intense, low emittance electron bunches at a high repetition rate using laser excitation.