SLAC, Menlo Park, California, USA
CERN, Geneva, Switzerland
Fermilab, Batavia, USA
One of the key systems of a Muon Collider (MC)- seen as the most exciting options for the energy frontier machine in the post-LHC era - is its interaction region (IR). Designs of its optics, magnets and machine-detector interface are strongly interlaced and iterative. As a result of recent comprehensive studies, consistent solutions for the 1.5 TeV c.o.m. MC IR have been found and are described here. To provide the required momentum acceptance, dynamic aperture and chromaticity, innovative approach was used for the IR optics. Conceptual designs of large-aperture high-field dipole and high-gradient quadrupole magnets based on Nb3Sn superconductor were developed and analyzed in terms of the operation margin, field quality, mechanics, coil cooling and quench protection. Shadow masks in the interconnect regions and liners inside the magnets are used to mitigate unprecedented dynamic heat deposition due to muon decays (~1 kW/m). It is shown that an appropriately designed machine-detector interface with sophisticated shielding in the detector has a potential to substantially suppress the background rates in the MC detector.
Diamond, Oxfordshire, United Kingdom
Northern Illinois University, DeKalb, Illinois, USA
Muons, Inc, Batavia, USA
JLAB, Newport News, Virginia, USA
ODU, Norfolk, Virginia, USA
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.
The University of Texas at Austin, Austin, Texas, USA
Fermilab, Batavia, USA
For future experiments at the intensity frontier, precise and accurate knowledge of beam time structure will be critical to understanding backgrounds. The proposed Mu2e experiment will utilize ~150nsec (FWHM) bunches of 107 protons at 8 GeV with a bunch-to-bunch period of 1.7 microseconds. The out-of-bunch beam must be suppressed by a factor of 10-9 relative to in-bunch beam and continuously monitored. I propose a Cerenkov based particle telescope to measure secondary production from beam interactions in a several tens of microns thick foil. Correlating timing information with beam passage allows the determination of relative beam intensity to arbitrary precision given a sufficiently long integration time. The goal is to verify out-of-bunch extinction to the level 10-6 in the span of several seconds. This allows near real-time monitoring of the initial extinction of the beam slow extracted from Fermilab's Debuncher before a system of AC dipoles and collimators, which will provide the final extinction. The effect on beam emittance is minimal, allowing the necessary continuous measurement. I will present the detector design and results of a test in Fermilab's MI-12 beamline.
Fermilab, Batavia, USA
DELTA, Dortmund, Germany
BNL, Upton, Long Island, New York, USA
The commissioning of the RHIC spin flipper in the RHIC Blue ring during the RHIC polarized proton run in 2009 showed the detrimental effects of global vertical coherent betatron oscillation induced by the 2-AC dipole plus 4-DC dipole configuration *. Additional three AC dipoles were added to the RHIC spin flipper in the RHIC Blue ring during the summer of 2010 to eliminate the vertical coherent betatron oscillations outside the spin flipper [2]. This new design is scheduled to be commissioned during the RHIC polarized proton run in 2011. This paper presents the status of the system as well as latest simulation results.
* M. Bai , T. Roser, C. Dawson, Y. Makdisi, W. Meng, F. Meot, P. Oddo, C. Pai, P. Pile, RHIC Spin Flipper New Design and Commissioning Plan, IPAC10 proceedings, IPAC 2010, Kyoto, Japan, 2010
BNL, Upton, Long Island, New York, USA
The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to control and dynamically tune the magnets. The current implementation and results will be presented.
LBNL, Berkeley, California, USA
CLASSE, Ithaca, New York, USA
Harvard University, Cambridge, Massachusetts, USA
The TE wave propagation method has become a widely used technique for measuring electron cloud density in an accelerator beampipe. In most instances the wave very low power is not capable of affecting the low-energy electrons distribution. During experiments in the CESR Damping Ring Test Accelerator (Cesr-TA), we have observed a particular situation where a resonance between the wave and a dipole magnetic field produces a large modification in the electron cloud distribution that can be measured by other detectors. We believe this resonance is strongly dependent on the geometry of standing waves pattern that discontinuities in the beampipe generate. We present measurements in Cesr-TA, which describe the effect and are in support of our hypothesis.
BNL, Upton, Long Island, New York, USA
Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including reinforcing the magnet base support assembly, a mechanical servo feedback system, and a local beam feedback system at each of the two experimental areas. However, implementation of the mechanical solutions would be expensive, and the local feedback system was insufficient since perturbation amplitudes outside the experimental areas were still problematic. A global 10 Hz orbit feedback system is currently under development at RHIC consisting of 36 beam position monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two counter-rotating rings. A subset of the system consisting of 8 BPMs and 4 corrector magnets in each ring was installed and successfully tested during the RHIC 2010 run; and the complete system is being installed for the 2011 run. A description of the overall system architecture and results with beam will be discussed.
BNL, Upton, Long Island, New York, USA
The shielding for the NSLS-II storage ring will provide adequate protection for the full injected beam losses in two periods of the ring around the injection point, but the remainder of the ring is shielded for lower losses of <10% top-off injection beam current. This will require a system to insure that beam losses do not exceed these levels for a period of time that could cause excessive radiation exposure outside the shield walls. This beam Loss Control and Monitoring system will have beam loss monitors that will measure where the beam charge is lost around the ring, to warn operators if losses approach the design limits. In order to measure the charge loss quantitatively, we propose measuring the electron component of the shower as beam electrons hit the vacuum chamber wall. This will be done using the Cerenkov light as charged particles transit an ultra-pure fused silica rod placed close to the inner edge of the VC. The length of rod will collect the light from many charged particles of the spread out shower resulting from the small glancing angle of the lost beam particles to the VC wall. The design and measurements results of the prototype Cerenkov BLM will be presented.
BNL, Upton, Long Island, New York, USA
The shielding design for the NSLS-II storage ring is designed for the full injected beam losses in two periods of the ring around the injection point, but for the remainder of the ring its shielded for <10% top-off injection beam. This will require a system to insure that beam losses do not exceed these levels for time sufficient to cause excessive radiation exposure outside the shield walls. This beam Loss Control and Monitoring (LCM) system will control the beam losses to the more heavily shielded injection region while monitoring the losses outside this region. To achieve this scrapers are installed in the injection region to intercept beam particles that might be lost outside this region. The scrapers will be thin (< 1Xrad) that will allow low energy electrons to penetrate and the subsequent dipole will separate them from the stored beam. These thin scrapers will reduce the radiation from the scraper compared to thicker scrapers. The dipole will provide significant local shielding for particles that hit inside the gap and a source for the loss monitor system that will measure the amount of beam lost in the injection region.
* Beam Loss Monitors for NSLS-II Storage Ring, S.L. Kramer & P. Cameron, these proceedings
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.
ANL, Argonne, USA
Accelerator-based light sources are some of the largest and most successful scientific user facilities in existence, serving tens of thousands of users each year. These important facilities enable research in diverse fields, including biology, pharmaceuticals, energy conservation and production, data storage, and archaeology. In this tutorial, we briefly review the history of accelerator-based light sources. We present an overview of the different types of accelerator-based light sources, including a description of their various operating principles, as well as a discussion of measures of performance. Technical challenges of current and future light sources are also reviewed.
NRL, Washington, DC, USA
UMD, College Park, Maryland, USA
JLAB, Newport News, Virginia, USA
SLAC, Menlo Park, California, USA
Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, Germany
GOO Zaryad, Novosibirsk, Russia
University of Michigan, Spin Physics Center, Ann Arbor, MI, USA
IUCF, Bloomington, Indiana, USA
Spin dynamics of polarized deuteron beams near depolarization resonances, including a new polarization preservation concept based on specially-designed multiple resonance crossings, has been tested in a series of experiments in the COSY synchrotron. Intricate spin dynamics with sophisticated pre-programmed patterns as well as effects of multiple crossings of a resonance were studied both theoretically and experimentally with excellent agreement. Possible applications of these results to preserve, manipulate and spin-flip polarized beams in synchrotrons and storage rings are discussed.
Fermilab, Batavia, USA
Northern Illinois University, DeKalb, Illinois, USA
Our recent experimental demonstration of a photoinjector electron bunch train with sub-picosecond structures is reported in this paper. The experiment is accomplished by converting an initially horizontal beam intensity modulation into a longitudinal phase space modulation, via a beamline capable of exchanging phase-space coordinates between the horizontal and longitudinal degrees of freedom. The initial transverse modulation is produced by intercepting the beam with a multislit mask prior to the exchange. We also compare our experimental results with numerical simulations.
SLAC, Menlo Park, California, USA
We discuss the properties of the coherent electromagnetic fields of a very short, ultra-relativistic bunch in a rectangular vacuum chamber inside a bending magnet. The analysis is based on the results of a direct numerical solution of Maxwell’s equations together with Newton’s equations. We use a new dispersion-free time-domain algorithm which employs a more efficient use of finite element mesh techniques and hence produces self-consistent and stable solutions for very short bunches. We investigate the fine structure of the CSR fields including coherent edge radiation. This approach should be useful in the study of existing and future concepts of particle accelerators and ultrafast coherent light sources.
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
USTC/NSRL, Hefei, Anhui, People's Republic of China
Osaka University, Osaka, Japan
UCL, London, United Kingdom
RCNP, Osaka, Japan
KEK, Ibaraki, Japan
BNL, Upton, Long Island, New York, USA
Several future accelerator projects at the Relativistic Heavy Ion Collider are being developed using a super-conducting electron energy recovery LINAC along with a superconducting electron gun as the source. All of the projects involve high-current, high-charge operation and require effective higher-order mode (HOM) damping to achieve the performance objectives. Among the HOM designs being developed is a waveguide-type HOM load for the electron gun consisting of a ceramic break surrounded by ferrite tiles. This design is innovative in its approach and achieves a variety of ends including broadband HOM damping and protection of the superconducting cavity from potential damage to the ferrite tiles. Furthermore, the ceramic is an effective thermal transition. This design may be useful in various applications since it readily allows for replacement of the ferrite tiles with other materials and may also be useful for testing the absorbing properties of these materials. In this paper, the details of the design will be discussed along with current modelling and testing results as well as future plans.
CLASSE, Ithaca, New York, USA
Cornell is currently developing a high current Energy Recovery Linac. The baseline 7-cell cavity design for the main linac has already been completed, and prototyping has begun, as of Fall 2010. Previous work showed that increasing the relative cavity-to-cavity frequency spread increases the beam break-up current through the linac. Simulations show that expected machining variations will introduce a relative HOM frequency spread of 0.5·10-3, corresponding to 150 mA of threshold current. The key idea of this work is to increase the relative cavity-to-cavity frequency spread by designing several classes of 7-cell cavities obtained by making small changes to the baseline center cell shape. This allows a threshold current in excess of 450 mA, which is well above the 100 mA goal for the Cornell Energy Recovery Linac.
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.
Texas A&M University, College Station, Texas, USA
The polyhedral cavity is a superconducting cavity structure in which a multi-cell cavity is built from a Roman-arch assembly of arc segments. Each segment has a Tesla-like r-z profile, and is fabricated either by bonding a Nb foil to a Cu substrate wedge or by depositing a Nb surface on the Cu substrate. The segments are assembled with an arrangement of locking rings and alignment pins, with a controlled narrow gap between segments over much of the arc-span of adjoining segments. A tubular channel is machined in the mating surfaces of the Cu wedges. Dipole modes are suppressed by locating along each channel a tube coated with rf-terminating ferrite. A first model of the cavity is being built to investigate mode structure, evaluate alternatives for the Nb surface fabrication, and develop assembly procedures.
USTC/NSRL, Hefei, Anhui, People's Republic of China
BINP SB RAS, Novosibirsk, Russia
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
BNL, Upton, Long Island, New York, USA
PKU/IHIP, Beijing, People's Republic of China
Stony Brook University, Stony Brook, USA
BNL, Upton, Long Island, New York, USA
Fermilab, Batavia, USA
BNL, Upton, Long Island, New York, USA
As a part of the proposed electron lens system for RHIC, two 6 T, 200 mm aperture, 2.5 meter long superconducting solenoids are being designed and built at BNL. Because of several demanding requirements this has become a unique and technologically advanced magnet. For example, the field lines on axis must be straight over the length of the solenoid within ±50 microns. Since this is beyond the normal construction techniques, a correction package becomes an integral part of the design for which a new design has been developed. In addition, a minimum of 0.3 T field is required along the electron beam trajectory in the space between magnets. To achieve this fringe field superconducting solenoidal coils have been added at the two ends of the main solenoid. The main solenoid itself is a challenging magnet because of the high Lorentz forces and stored energy associated with the large aperture and high fields. An innovative structure has been developed to deal with the large axial forces at the ends. This paper will summarize the magnetic design and optimization of the entire package consisting of the main solenoid, the fringe field solenoids, and the corrector system.
Fermilab, Batavia, USA
The Helical Cooling Channel (HCC) was proposed for 6D cooling of muon beams required for muon collider and some other applications. HCC uses a continuous absorber inside superconducting magnets which produce solenoidal field superimposed with transverse helical dipole and helical gradient fields. HCC is usually divided into several sections each with progressively stronger fields, smaller aperture and shorter helix period to achieve the optimal muon cooling rate. This paper presents the design issues of the high field section of HCC with coil separation. The effect of coil spacing on the longitudinal and transverse field components is presented and its impact on the muon cooling is evaluated and discussed. The paper also describes methods for field corrections and their practical limits.
LBNL, Berkeley, California, USA
Fermilab, Batavia, USA
BNL, Upton, Long Island, New York, USA
Particle Beam Lasers, Inc., Northridge, California, USA
BNL, Upton, Long Island, New York, USA
UCLA, Los Angeles, California, USA
For a muon collider with copious decay particles in the plane of the storage ring, open-midplane dipoles (OMD) may be preferable to tungsten-shielded cosine-theta dipoles of large aperture. The OMD should have its midplane completely free of material, so as to dodge the radiation from decaying muons. Analysis funded by a Phase I SBIR suggests that a field of 10-20 T should be feasible, with homogeneity of 1x10-4 and energy deposition low enough for conduction cooling to 4.2 K helium. If funded, a Phase II SBIR would refine the analysis and build and test a proof-of-principle magnet.
Texas A&M University, College Station, Texas, USA
TAMU3 is a block-coil short model dipole which embodies for the first time at high field (>12T) strength the techniques of stress management within the superconducting windings. The dipole consists of two planar racetrack coil assemblies, assembled within the rectangular aperture of a flux return core. Each assembly contains an inner and outer winding, and a high-strength support structure which is integrated within the assembly to intercept the Lorentz stress produced from the inner winding so that it does not accumulate to produce high stress in the outer winding. Iso-static preload is applied by pressurizing a set of thin stainless steel bladders with molten Woods metal and then freezing the metal under pressure. Current technology, difficulties, and present status of construction of magnet assembly will be presented.
ANL, Argonne, USA
The APS booster is a 7-GeV electron synchrotron with 0.5-second cycle time. Both voltage and current ramp modes were in the original design but only the voltage ramp has been commissioned. Two software-based ramp control programs are used to regulate the current waveform to a linear ramp. The system has been operated for user beam operations for many years. Some instability exists in the ramp correction that requires manual intervention from time to time by the operators. Sensitivity of magnet currents to external changes, such as AC line voltage, harmonic interference from the high-power rf system, etc., has been observed. In order to meet the increased single-bunch-charge requirement of the APS upgrade we need more flexible current ramps such as flat porches for injection and extraction and smooth transitions. Recent efforts to develop an energy-saving operation mode also call for ramp improvement. This paper presents test results of a workstation-based current regulation program and an FPGA-based implementation as a future upgrade.
BNL, Upton, Long Island, New York, USA
We designed two electron lenses to apply head-on beam-beam compensation for RHIC; they will be installed near IP10. The electron-beam transport system is an important subsystem of the entire electron-lens system. Electrons are transported from the electron gun to the main solenoid and further to the collector. The system must allow for changes of the electron beam size inside the superconducting magnet, and for changes of the electron position by 5 mm in the horizontal- and vertical-planes.
BNL, Upton, Long Island, New York, USA
A catastrophic failure of the RHIC magnet cooling lines, similar to the LHC superconducting bus failure incident, would pressurize the insulating vacuum in the magnet and transfer line cryostats. Insufficient relief valves on the cryostats could cause a structural failure. A SINDA/FLUINT® model, which simulated the 4.5K/ 4 atm helium flowing through the magnet cooling system distribution lines, then through a line break into the vacuum cryostat and discharging via the reliefs into the RHIC tunnel, had been developed to calculate the helium pressure inside the cryostat. Arc flash energy deposition and heat load from the ambient temperature cryostat surfaces were included in the simulations. Three typical areas: the sextant arc, the Triplet/DX/D0 magnets, and the injection area, had been analyzed. Existing relief valve sizes were reviewed to make sure that the maximum stresses, caused by the calculated maximum pressures inside the cryostats, did not exceed the allowable stresses, based on the ASME Code B31.3 and ANSYS results.
BNL, Upton, Long Island, New York, USA
National Synchrotron Light Source II (NSLS-II), being constructed at Brookhaven National Laboratory, is a 3- GeV, high-flux and high-brightness synchrotron radiation facility with a nominal current of 500 mA. The storage ring vacuum system has extruded aluminium chambers, with ante-chamber for photon fans and distributed NEG strip pumping. Discrete photon absorbers are used to intercept the un-used bending magnet radiation. In-situ bakeout is implemented to achieve fast conditioning during initial commissioning and after interventions.
NTHU, Hsinchu, Taiwan
NCTU, Hsinchu, Taiwan
NSRRC, Hsinchu, Taiwan
IUCF, Bloomington, Indiana, USA
IAP, Frankfurt am Main, Germany
CERN, Geneva, Switzerland
Fermilab, Batavia, USA
CERN, Geneva, Switzerland
The LHC collimation upgrade foresees additional collimators installed in dispersion suppressor regions. To obtain the necessary space for the collimators, a solution based on the substitution of LHC main dipoles for stronger dipoles is being considered. CERN and FNAL have started a joint program to demonstrate the feasibility of Nb3Sn technology for this purpose. The goal of the first phase is the design and construction of a 2-m long single-aperture demonstrator magnet with a nominal field of 11 T at 11.85 kA with 20% margin. This paper describes the magnetic and mechanical design of the demonstrator magnet and summarizes its design parameters.
RadiaBeam, Santa Monica, USA
UCLA, Los Angeles, California, USA
ELETTRA, Basovizza, Italy
Rome University La Sapienza, Roma, Italy
INFN/LNF, Frascati (Roma), Italy
ELSA, Bonn, Germany
Since more than four decades, the University of Bonn supports research at the in-house electron accelerator ELSA. Presently, the polarized electrons gained from an inverted source are accumulated in a stretcher ring and accelerated within a fraction of a second up to 3.2 GeV. During the fast ramping various depolarizing resonances are crossed. By taking several expedient measures (closed orbit correction, tune jumping, etc.) a high polarization degree of up to 65% is reached. One important part of these measures is the harmonic correction of integer resonances. Those resonances are compensated by applying additional horizontal fields, distributed sinusoidally along an one-turn orbit length. In case of an appropriate setting of amplitude and phase, all resonance driving effects should be neutralized completely. First studies have shown that vertical displacements and resulting horizontal fields in the quadrupole magnets, caused by the resonance correction, have to be taken into account as well. With regard to a new correction scheme, the first experimental results confirmed by simulative and theoretical studies will be presented.
KIT, Karlsruhe, Germany
CLASSE, Ithaca, New York, USA
ESS-Bilbao, Zamudio, Spain
ESS Bilbao, Bilbao, Spain
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
Bilbao, Faculty of Science and Technology, Bilbao, Spain
University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
The ESS-Bilbao linac will accelerate H+ and H− beams up to 50 MeV, which need to be transported to three laboratories, where different types of experiments will be conducted. This paper reports on the preliminary design of the transfer line, which is mainly performed based on beam dynamics simulations.
ESS Bilbao, Bilbao, Spain
Bilbao, Faculty of Science and Technology, Bilbao, Spain
University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
ESS-Bilbao, Zamudio, Spain
In this work we present a future upgrade of the ESS-Bilbao multi-source Low Energy Transport System (LEBT). It consists of a set of solenoids and steering dipoles used to match the characteristics of both ion source beams i.e., the Electron Cyclotron Resonance (ECR) H+/D+ source and the H− Penning source, to the input specifications of the RFQ. Different configurations of the geometry and magnetic fields are studied in order to minimize the emittance growth along the LEBT, while providing the beam specifications required by the RFQ.
LBNL, Berkeley, California, USA
ORNL, Oak Ridge, Tennessee, USA
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
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.
Northern Illinois University, DeKalb, Illinois, USA
Muons, Inc, Batavia, USA
JLAB, Newport News, Virginia, USA
ODU, Norfolk, Virginia, USA
Designing and simulating complex magnet systems needed for cooling channels in both neutrino factories and muon colliders requires innovative techniques to correct for both chromatic and spherical aberrations. Optimizing complex systems, such as helical magnets for example, is also difficult but essential. By using COSY INFINITY, a differential algebra based code, the transfer and aberration maps can be examined to discover what critical terms have the greatest influence on these aberrations.
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
USC, Los Angeles, 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.
Fermilab, Batavia, USA
Tech-X, Boulder, Colorado, USA
Fermilab, Batavia, USA
* A. Burov, “Dancing Bunches as van Kampen Modes”, this conference.
BNL, Upton, New York, USA
UNM, Albuquerque, New Mexico, USA
We compare our 2D mean field (Vlasov-Maxwell) treatment of coherent synchrotron radiation (CSR) effects with 1D approximations of the CSR force which are commonly implemented in CSR codes. In our model we track particles in 4D phase space and calculate 2D forces*. The major cost in our calculation is the computation of the 2D force. To speed up the computation and improve 1D models we also investigate approximations to our exact 2D force. Preliminary results are encouraging**. As an application, we present numerical results for the LCLS bunch compressors, where recently detailed measurements of the CSR-induced energy loss and transverse emittance growth have been performed and compared with numerical calculations***.
* Phys. Rev. ST Accel. Beams 12, 080704 (2009)
** http://www.lnf.infn.it/conference/uBI10/
*** Phys. Rev. ST Accel. Beams 12, 030704 (2009)
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.
IUCF, Bloomington, Indiana, USA
IUCEEM, Bloomington, Indiana, USA
SLAC, Menlo Park, California, USA
Fermilab, Batavia, USA
CLASSE, Ithaca, New York, USA
CalPoly, San Luis Obispo, California, USA
Cornell University, Ithaca, New York, USA
The study of electron cloud-related instabilities for the CESR-TA project has required the development of new measurement techniques. The dynamics of the interaction of electron clouds with trains of bunches has been undertaken employing three basic observations. Measurements of tune shifts of bunches along a train has been used extensively with the most recent observations permitting the excitation of single bunches within the train to avoid collective train motion from driving the ensemble of bunches. Another technique has been developed to detect the coherent self-excited spectrum for each of the bunches within a train. This method is particularly useful when beam conditions are near the onset of an instability. The third method was designed to study bunches within the train in conditions below the onset of unstable motion. This is accomplished by separately driving each bunch within the train for several hundred turns and then observing the damping of its coherent motion. These last two techniques have been applied to study both transverse dipole (centroid) and head-tail motion. We will report on the observation methods and give examples of typical results.
Northern Illinois University, DeKalb, Illinois, USA
ANL, Argonne, USA
BINP SB RAS, Novosibirsk, Russia
BNL, Upton, Long Island, New York, USA
Danfysik A/S, Jyllinge, Denmark
IAP, Frankfurt am Main, Germany
BSU, Minsk, Belarus
Fermilab, Batavia, USA
In Fermilab’s electron cooler, a 0.1A, 4.3MeV DC electron beam propagates through the 20 m cooling section, which is immersed in a weak longitudinal magnetic field. A proper adjustment of 200 dipole coils, installed in the cooling section for correction of the magnetic field imperfections, can create a helix-like trajectory with the wavelength of 1-10 m. The longitudinal cooling force is measured in the presence of such helices at different wavelengths and amplitudes. The results are compared with a model calculating the cooling force as a sum of collisions with small impact parameters, where the helical nature of the coherent angle is ignored, and far collisions, where the effect of the coherent motion is neglected. A qualitative agreement is found.
Fermilab, Batavia, USA
Project X, under study at Fermilab, is a multi task SRF beam facility, aiming to provide high intensity protons for rare processes experiments and nuclear physics at low energy, and simultaneously for the production of neutrinos, as well as muon beams in the long term. A beam test facility - former known as High Intensity Neutrino Source (HINS) - is under commissioning for testing critical components of the project, e.g. a beam chopper. In this paper we describe the layout of the test facility and present beam dynamics simulations and measurements.
Northern Illinois University, DeKalb, Illinois, USA
ANL, Argonne, USA
SLAC, Menlo Park, California, USA
The input power of accelerator structure is normally fed through a coupling slot(s) on the outer wall of the accelerator structure via magnetic coupling. While providing perfect matching, the coupling slots may produce non-axial-symmetric fields in the coupler cell that can induce emittance growth as the beam is accelerated in such a field. This effect is especially important for low emittance beams at low energies such as in the injector accelerators for light sources. In this paper, we present studies of multipole fields of different rf coupler designs and their effect on beam emittance for an X-band photocathode gun, being jointly designed with LLNL, and the X-band accelerator structures. We will present symmetrized rf coupler designs for these components to preserve the beam emittance.
CERN, Geneva, Switzerland
BNL, Upton, Long Island, New York, USA
We are presenting the layout and the optics of a beam line to be used as a medical gantry in radiation therapy. The optical properties of the gantry’s beam line are such as to make the beam line achromatic and uncoupled. These two properties make the beam spot size, which is delivered and focused by the gantry, on the tumor of the patient, independent of the angular orientation of the gantry. In this paper we present the layout of the magnetic elements of the gantry, and also present the theoretical basis for the optics design of such a gantry.
* N. Tsoupas et. al. “Uncoupled achromatic tilted S-bend” Presented at the 11th Biennial European Particle Accelerator Conference, Genoa, Italy, June 23-27,2008
Muons, Inc, Batavia, USA
Hampton University, Hampton, Virginia, USA
Fermilab, Batavia, USA
A compact tunable gamma ray source has many potential uses in medical and industrial applications. One novel scheme to produce an intense beam of gammas relies on the ability to create a high flux of positrons, which are produced by an electron beam on a high Z target. We present an innovative system which allows for a nearly arbitrary targeting geometry that supports multiple targets, whose optimal design is allowed to be driven by the physics of the positron production processes, while naturally supporting cooling of the targets.
BNL, Upton, Long Island, New York, USA
To reduce the effect of trajectory perturbations due to vibrations of the final focusing quadrupoles at RHIC, global orbit feedback was successfully prototyped during run-10. The system was tested using transfer functions between the beam position monitors and correctors obtained from the online optical model and a correction algorithm based on singular value decomposition (SVD). In run-11 we plan to self-calibrate the system using SVD matrices derived from orbit response matrix (ORM) measurements acquired real-time using the new FPGA-based signal processing. Comparisons between measurement and model and of feedback performance with the two methods are presented.
BNL, Upton, Long Island, New York, USA
RHIC operated at energies below the nominal ion injection energy of E=9.8 GeV/u in 2010. Earlier test runs and magnet measurements indicated that all defocusing sextupole unipolar power supplies should be reversed to provide the proper sign of chromaticity. However, vertical chromaticity at E=3.85 GeV/u with this power supply configuration was still not optimal. This uncertainty inspired a new machine configuration where only half of the defocusing sextupole power supplies were reversed, taking advantage of the flexibility of the RHIC nonlinear chromaticity correction system to mimic bipolar sextupoles. This configuration resulted in a 30 percent luminosity gain and eliminated the need for further polarity changes for later 2010 low energy physics operations. Here we describe the background to this problem, operational experience, and RHIC online model changes to implement this solution.
BNL, Upton, Long Island, New York, USA
The recently completed RHIC fast global orbit feedback system uses 24 small “window-frame” horizontal dipole correctors. Space limitations dictated a very compact design. The magnetic design and modelling of these laminated yoke magnets is described as well as the mechanical implementation, coil winding, vacuum impregnation, etc. Test procedures to determine the field quality and frequency response are described. The results of these measurements are presented and discussed. A small fringe field from each magnet, overlapping the opposite RHIC ring, is compensated by a correction winding placed on the opposite ring’s magnet and connected in series with the main winding of the first one. Results from measurements of this compensation scheme are shown and discussed.
SLAC, Menlo Park, California, USA
The SUPER-B detector solenoid has a strong 1.5 T field in the Interaction Region (IR) area, and its tails extend over the range of several meters. The main effect of the solenoid field is the coupling of the horizontal and vertical betatron motion which needs to be corrected in order to preserve the small design beam size at the Interaction Point. The additional complications are that: a) due to the crossing angle the solenoid is not parallel to either of the two beams, thus leading to orbit and dispersion perturbations; b) the solenoid overlaps the innermost IR permanent quadrupoles, which will cause additional coupling effects. The proposed correction system provides local compensation of the solenoid effects independently for each side of the IR. It includes “bucking” solenoids to remove the unwanted long solenoid field tails and a set of skew quadrupoles, dipole correctors and anti-solenoids to cancel all linear perturbations to the optics. The details of the correction system design are presented.
CLASSE, Ithaca, New York, USA
We are considering the SC quadrupole where the field formed not only by the current distributions, but with the poles also. This delivers a good quality field in all aperture allowing compact and inexpensive design. This type of quadrupole designed for Cornell ERL could be recommended for ILC also.
UMAN, Manchester, United Kingdom
CERN, Geneva, Switzerland
We report on the suppression of long-range wakefields in the main linacs of the CLIC collider. This structure operates with a 120 degree phase advance per cell. The wakefield is damped using a combination of detuning the frequencies of beam-excited higher order modes and by light damping, through slot-coupled manifolds. This serves as an alternative to the present baseline CLIC design which relies on heavy damping. Detailed simulations of both the optimised surface fields resulting from the monopole mode, and from wakefield damping of the dipole modes, are discussed. We report on fabrication details of a structure consisting of 24 cells, diffusion bonded together. This design, known as CLICDDSA, takes into practical mechanical engineering issues and is the result of several optimisations since the earlier CLICDDS designs. This structure is due to be tested for its capacity to sustain high gradients at CERN.
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
LBNL, Berkeley, California, USA
In the past small storage rings with dipole-magnet-only sources were called second-generation light sources (before insertion devices (IDs) were used). With today's technology, e.g. superconducting dipole magnet of 5 T (e.g., ALS's Superbend *), one could make a smaller ring (say, 60-m circumference) with substantial brightness for dipole-magnet beams. Without IDs, these optimized sources would be designated as between second and third generation. Such rings don't exist yet, but their concept can be compared with other types of compact light sources. Typical parameters of such ring would be 60-m circumference, 2 GeV, several 5-T dipole sources in TME-like cells, and 4x1013 photons/s/0.1% BW at 1 Angstrom. The number of beamlines is variable, but potentially very large, only limited by funding.
* D. Robin et al., NIM A 538, 1-3, (2005), 65-92.
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, New York, USA
BNL, Upton, Long Island, New York, USA
In order to meet the requirements of high average current accelerators, such as the Superconducting Proton Linac (SPL) at CERN and the electron–ion collider (eRHIC) at BNL, a high current 5-cell SRF cavity, called BNL3 cavity, was designed. The optimization process aimed at maximizing the R/Q of the fundamental mode and the geometry factor G under an acceptable RF field level of Bpeak/Eacc or Epeak/Eacc. In addition, a pivotal consideration for the high current accelerators is efficient damping of dangerous higher-order modes (HOM) to avoid inducing emittance degradation, cryogenic loading or beam-breakup (BBU). To transport the HOMs out of the cavity, the BNL3 cavity employs a larger beam pipe, allowing the propagation of HOMs but not the fundamental mode. Moreover, concerning the BBU effect, the BNL3 cavity is aimed at low (R/Q)Qext for dangerous modes, including dipole modes and quadrupole modes. This paper presents the design of the BNL3 cavity, including the optimization for the fundamental mode, and the BBU limitation for dipole and quadrupole modes. The BBU simulation results show that the designed cavity is qualified for high-current, multi-pass machines such as eRHIC.