ORNL, Oak Ridge, Tennessee, USA
A review of the Spallation Neutron Source (SNS) linac beam dynamics is presented. It describes transverse and longitudinal beam optics, losses, activation, and comparison between the initial design and the existing accelerator. The SNS linac consists of normal conducting and superconducting parts. The peculiarities in operations with the superconducting part of the SNS linac (SCL), estimations of total losses in SCL, the possible mechanisms of these losses, and the progress in the transverse matching are discussed.
Fermilab, Batavia, USA
Muon Collider (MC) is a promising candidate for the next energy frontier machine. However, in order to obtain peak luminosity in the 1034cm-2s-1 range the collider lattice design must satisfy a number of stringent requirements. In particular the expected large momentum spread of the muon beam and the very small β* call for a careful correction of the chromatic effects. Here we present a particular solution for the interaction region (IR) optics whose distinctive feature is a three-sextupole local chromatic correction scheme. The scheme may be applied to other future machines where chromatic effects are expected to be large.
SLAC, Menlo Park, California, USA
LLNL, Livermore, California, USA
The XTA (X-Band Test Area) is being assembled in the NLCTA tunnel of the SLAC National Laboratory to serve as a test facility for new RF guns. The first gun to be tested will be an upgraded version of the 5.6 cell, 200MV/m peak field X-band designed at SLAC in 2003 for the Compton Scattering experiment run in ASTA. This new version includes some features implemented in 2006 on the LCLS gun such as racetrack couplers, increased mode separation and elliptical irises. These upgrades were discussed in collaboration with LLNL since the same gun will be used as a driver for the LLNL Gamma-ray Source. Our beamline includes an X-band accelerating section which takes the electron beam up to 100 MeV and an electron beam measurement station. Other X-Band guns such as the UCLA Hybrid gun will be characterized at our facility.
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.
Hampton University, Hampton, Virginia, USA
JLAB, Newport News, Virginia, USA
Muons, Inc, Batavia, USA
Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a high-luminosity muon collider. For the implementation of PIC, we earlier developed an epicyclic twin-helix channel with correlated behavior of the horizontal and vertical betatron motions and dispersion. We now insert absorber plates with short energy-recovering units located next to them at the appropriate locations in the twin-helix channel. We first demonstrate conventional ionization cooling in such a system with the optics uncorrelated. We then adjust the correlated optics state and induce a parametric resonance to study ionization cooling under the resonant condition.
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.
SLAC, Menlo Park, California, USA
SLAC, Menlo Park, California, USA
UCLA, Los Angeles, California, USA
USC, Los Angeles, California, USA
The ideal drive beam current profile for the plasma wakefield accelerator (PWFA) has been predicted by 1D and 2D simulations to be characterized by a triangular ramp that rises linearly from head to tail, followed by a sharp drop. A technique for generating such bunches experimentally was recently demonstrated. We present here an adaptation of this scheme to generate ramped bunches using the 23 GeV electron beam produced in the first two-thirds of the SLAC linac, and discuss plans to implement this scheme for high transformer ratio demonstration experiments at the FACET plasma wakefield accelerator facility.
SLAC, Menlo Park, California, USA
FACET is a new facility under construction at the SLAC National Accelerator Laboratory. The FACET beam line is designed to provide 23 GeV tightly focused and compressed electron and positron bunches for beam driven plasma wakefield acceleration research and other experiments. Achieving optimal beam parameters for various experimental conditions requires the optics capability for tuning in a sufficiently wide range. This will be achieved by using optics tuning systems (knobs). Design of such systems for FACET is discussed.
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
POSTECH, Pohang, Kyungbuk, Republic of Korea
PAL, Pohang, Kyungbuk, Republic of Korea
The X-ray is focused by two zone plates in 1B2 beamline to image electron beam in PLS. From numerical study, we can determine the optical limit of resolution with the same specifications of Fresnel zone plates in 1B2 beamline. The width of Airy pattern and the outmost width of zone plates are turned out to be not good parameters to determine the resolution of the imaging system with a zone plate. The resolution of the entire imaging system 1B2 beamline will be revealed as 682 nm.
BNL, Upton, Long Island, New York, USA
In 2009 a beam-energy monitor was installed in the high energy beam transport (HEBT) line at the Brookhaven National Lab linac. This device measures the energies of electrons stripped from the 40mA H− beam by background gas. Electrons are stripped by the 1.7x10-7torr residual gas at a rate of ~2.4x10-8/cm. Since beam electrons have the same velocities as beam protons, the beam proton energy is deduced by multiplying the electron energy by mp/me=1836. A 183.6MeV H− beam produces 100keV electrons. In 2010 we installed an optics plates containing a laser and optics to add beam-profile measurement capability via photodetachment. Our 100mJ/pulse, Q-switched laser neutralizes 70% of the beam during its 10ns pulse. The chamber in which the laser light passes through the ion beam is upstream of a dipole magnet which deflects the electrons into a biased retarding-grid (V<125kV) Faraday-cup detector. To measure beam profiles, a narrow laser beam is stepped across the ion beam removing electrons from the portion of the H− beam intercepted by the laser. The laser also gives us energy measurements on the 0.2mA polarized proton beam.
BNL, Upton, Long Island, New York, USA
Fermilab, Batavia, USA
Beam-profile diagnostics are being developed for a superconducting (SC) radiofrequency (RF) Test Accelerator that is currently under construction at the New Muon Lab (NML) at Fermilab. The facility’s design goals include the replication of the pulse train proscribed for the International Linear Collider (ILC). An RF photoelectric gun based on the DESY design will generate the beam. In test-beam mode a low-power beam will be characterized with intercepting radiation converter screens: either a 100-micron thick YAG:Ce single crystal scintillator or a 1-micron thin Al optical transition radiation (OTR) foil. This prototype station was constructed by RadiaBeam Technologies under a contract with Fermilab. In both cases the screen surface was normal to the beam direction followed by a downstream 45-degree mirror that directed the radiation into the optical system. The optical system has better than 20 (10) micron rms spatial resolution when covering a vertical field of view of 18(5) mm. These initial tests were performed at the A0 Photoinjector at a beam energy of ~15 MeV and with micropulse charges from 25 to 500 pC for beam sizes of 45 to 250 microns. Example results will be presented.
Fermilab, Batavia, USA
A console application using the phasing of Turn-by-Turn signals from the different BPMs has been tested at the Fermilab Booster. This techinique allows the on-line detection of the beam tunes during the fast Booster ramp in conditions where other algorithms were unsuccessful. The application has been recently expanded to include the computation of the linear coupling coefficients. Algorithm and measurement results are presented.
RadiaBeam, Santa Monica, USA
CLASSE, Ithaca, New York, USA
KEK, Ibaraki, Japan
MAX-lab, Lund, Sweden
CERN, Geneva, Switzerland
KIT, Karlsruhe, Germany
CLASSE, Ithaca, New York, USA
LANL, Los Alamos, New Mexico, USA
An Emittance EXchanger (EEX), like a chicane, can be used for bunch compression. However, it offers a unique characteristic: the R56 term in an EEX vanishes, which decouples the final longitudinal position from the particles’ energies, thereby suppressing the microbunch instability. Also, it can provide simultaneous compression in both the longitudinal and one transverse dimensions, where, for example, the final longitudinal size is smaller than the initial horizontal size and the final horizontal size is smaller than the initial longitudinal size. In this scheme, there is no dependence on an energy slew needed for compressing the beam, simplifying the rf requirements. A bunch-compression scheme using two EEXs is presented, including CSR calculations.
NRL, Washington, DC, USA
UMD, College Park, Maryland, USA
SAIC, Billerica, Massachusetts, USA
Beam-Wave Research, Inc., Union City, USA
We explore periodically cusped magnetic (PCM) fields in the regime of a Ka-Band coupled-cavity travelling wave tube (beam current = 3.5A, voltage = 19.5kV, 10:1 beam aspect ratio). We use finite-element beam optics code MICHELLE to simulate the 3-dimensional beam optics for the beam transport within a PCM field. Realistic 3-dimensional magnetic fields have been considered to determine the practicality of these designs. We present the methodology used to focus and transport a thermal beam from a shielded-cathode, high aspect-ratio electron gun.
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.
University of Connecticut, Storrs, Connecticut, USA
JLAB, Newport News, Virginia, USA
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)
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
LLNL, Livermore, California, USA
A 130 keV injector is developed for the NDCX-II facility. It consists of a 10.9 cm diameter lithium doped alumina-silicate ion source heated to ~1300 °C and 3 electrodes. Other components include a segmented Rogowski coil for current and beam position monitoring, a gate valve, pumping ports, a focusing solenoid, a steering coil and space for inspection and maintenance access. Significant design challenges including managing the 3-4 kW of power dissipation from the source heater, temperature uniformity across the emitter surface, quick access for frequent ion source replacement, mechanical alignment with tight tolerance, and structural stabilization of the cantilevered 27” OD graded HV ceramic column. The injector fabrication is scheduled to complete by May 2011, and assembly and installation is scheduled to complete by the beginning of July.
ORNL, Oak Ridge, Tennessee, USA
ORNL RAD, Oak Ridge, Tennessee, USA
This paper presents an overview of experimental and theoretical studies on laser stripping that have been conducted up to the present time in the SNS project. The goal of this work is to develop techniques to achieve the experimental preconditions necessary for the successful realization of a future intermediate experiment on laser stripping. The experimental work consists of the tuning and measurement of H־ beam parameters in readiness for the intermediate experiment, and also takes into account the features and possibilities of the SNS accelerator.
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
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.
NSCL, East Lansing, Michigan, USA
Notre Dame University, Notre Dame, Iowa, USA
LBNL, Berkeley, California, USA
FRIB, East Lansing, Michigan, USA
DIANA (Dakota Ion Accelerators for Nuclear Astrophysics) is a next generation nuclear astrophysics accelerator facility proposed to be built as part of the US DUSEL (Deep Underground Science and Engineering Laboratory) project. The scientific goals of DIANA are focused on experiments related to nucleosynthesis processes. Reaction cross-sections at stellar temperature are extremely low, which makes these experiments challenging. Small signal rates are overwhelmed by large background rates associated with cosmic ray-induced reactions, background from natural radioactivity in the laboratory environment, and the beam-induced background on target impurities. By placing the DIANA facility deep underground (1.4 km) the cosmic ray induced background can be eliminated. In addition, the DIANA accelerator is being designed to achieve large laboratory reaction rates by delivering high ion beam currents (up to 100 mA) to a high density super-sonic jet-gas target (up to 1018 atoms/cm2). Two accelerators are coupled to enable measurements over a wide energy range from 30 keV to 3 MeVin a consistent manner. The accelerators design and its technical challenges are presented.