HIT, Heidelberg, Germany
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.
HU/AdSM, Higashi-Hiroshima, Japan
Hiroshima University, Higashi-Hiroshima, Japan
LBNL, Berkeley, California, USA
The Neutralized Drift Compression Experiment (NDCX-I) generates high intensity ion beams to explore Warm Dense Matter physics. A ~150 kV, ~500 ns ramped voltage pulse is applied to a ~300 keV, 5-10 μs, 25 mA K+ ion beam across a single induction gap. The velocity modulated beam compresses longitudinally during ballistic transport along a space-charge-neutralizing plasma transport line, resulting in ~3A peak current with ~2-3 ns pulse durations (FWHM) at the target plane. Transverse final focusing is accomplished with a ~8 T, 10 cm long pulsed solenoid magnet. Time-dependent focusing in the induction gap, and chromatic aberrations in the final focus optics limit the peak fluence at the target plane for the compressed beam pulse. We report on time-dependent phase space measurements of the compressed pulse in the ballistic transport beamline, and measurement of the time-dependent radial impulses derived from the interaction of the beam and the induction gap voltage. We present results of start-to-end simulations to benchmark the experiments. Fast correction strategies are discussed with application to both NDCX-I and to the new NDCX-II accelerator.
SLAC, Menlo Park, California, USA
CERN, Geneva, Switzerland
Radio Frequency noise induced bunch lengthening can strongly affect the Large Hadron Collider performance through luminosity reduction, particle loss, and other effects. Models and theoretical formalisms demonstrating the dependence of the LHC longitudinal bunch length on the RF station noise spectral content have been presented*,**. Initial measurements validated these studies and determined the performance limiting RF components. For the existing LHC LLRF implementation the bunch length increases with a rate of 1 mm/hr, which is higher than the intrabeam scattering diffusion and leads to a 27% bunch length increase over a 20 hour store. This work presents measurements from the LHC that better quantify the relationship between the RF noise and longitudinal emittance blowup. Noise was injected at specific frequency bands and with varying amplitudes at the LHC accelerating cavities. The experiments presented in this paper confirmed the predicted effects on the LHC bunch length due to both the noise around the synchrotron frequency resonance and the noise in other frequency bands aliased down to the synchrotron frequency by the periodic beam sampling of the accelerating voltage.
*T. Mastorides et.al., "RF system models for the LHC with Application to Longitudinal Dynamics,"
**T. Mastorides et.al., "RF Noise Effects on Large Hadron Collider Beam Diffusion"
Korea Basic Science Institute, Busan, Republic of Korea
Pusan National University, Pusan, Republic of Korea
RIKEN Nishina Center, Wako, Japan
The establishment of a compact linear accelerator is in progress by Korea Basic Science Institute. The main capability of this facility is the production of multiply ionized metal clusters and the generation of intense beams of highly charged ions for material, medical and nuclear physical research. To generate the intense beam of highly charged ions, we will develop an Electron Cyclotron Resonance Ion Source (ECRIS) using 28GHz microwaves. For this ECRIS, the designing of a superconducting magnet, microwave inlet, beam extraction, and plasma chamber were in progress. A superconducting magnet system have also being developed. In this presentation, I report the current status of our compact linear accelerator development and future plan.
Northern Illinois University, DeKalb, Illinois, USA
Muons, Inc, Batavia, USA
JLAB, Newport News, Virginia, USA
ODU, Norfolk, Virginia, USA
BNL, Upton, Long Island, New York, USA
Coherent Electron Cooling (CeC) requires detailed con- trol of the phase between the hadron an the FEL-amplified wave packet. This phase depends on local electron beam parameters such as the energy spread and the peak current. In this paper, we examine the effects of local density variations on the cooling rates for CeC.
Tech-X, Boulder, Colorado, USA
BNL, Upton, Long Island, New York, USA
Next generation ion colliders will require effective cooling of high-energy hadron beams. Coherent electron cooling (CEC) can in principle cool relativistic hadron beams on orders-of-magnitude shorter time scales than other techniques. We present Vlasov-Poisson and delta-f particle-in-cell (PIC) simulations of a CEC modulator section. These simulations correctly capture the subtle time and space evolution of the density and velocity wake imprinted on the electron distribution via anisotropic Debye shielding of a drifting ion. We consider 1D and 2D reduced versions of the problem, and compare the exact solutions of Wang and Blaskiewicz with Vlasov-Poisson and delta-f PIC simulations. We also consider interactions under non-ideal conditions where there is a density gradient in the electron distribution, and present simulations of the ion wake.
* V.N. Litvinenko and Y.S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).
Tech-X, Boulder, Colorado, USA
BNL, Upton, Long Island, New York, USA
PSI, Villigen, Switzerland
Increasing the luminosity of ion beams in particle accelerators is critical for the advancement of nuclear and particle physics. Coherent electron cooling promises to cool high-energy hadron beams significantly faster than electron cooling or stochastic cooling. Here we show simulations of a single pass through a coherent electron cooler, which consists of a modulator, a free-electron laser, and a kicker. In the modulator the electron beam copropagates with the ion beam, which perturbs the electron beam density according to the ion positions. The FEL, which both amplifies and imparts wavelength-scale modulation on the electron beam. The strength of modulated electric fields determines how much they accelerate or decelerate the ions when electron beam recombines with the dispersion-shifted hadrons in the kicker region. From these field strengths we estimate the cooling time for a gold ion with a specific longitudinal velocity.
* Vladimir N. Litvinenko, Yaroslav S. Derbenev, Physical Review Letters 102, 114801 (2009)
UCLA, Los Angeles, California, USA
Laser-Driven Ion Acceleration in thin foils has demonstrated high-charge, low-emittance MeV ion beams with a picosecond duration. Such high-brightness beams are very attractive for a compact ion source or an injector for RF accelerators. However in the case of foils scaling of the pulse repetition rate and improving shot-to-shot reproducibility is a serious challenge. CO2 laser-plasma interactions provide a possibility for using a debris free gas jet for target normal sheath acceleration of ions. Gas jets have the advantage of precise density control around the critical plasma density for 10 um pulses (1019 cm-3) and can be run at 1-10 Hz. The master oscillator–power amplifier CO2 laser system at the UCLA Neptune Laboratory is being upgraded to generate 1 J, 3 ps pulses at 1Hz. For this purpose, a new 8 atm CO2 module is used to amplify a 3 ps pulse to ~10 GW level. Final amplification is realized in a 1-m long TEA CO2 amplifier, for which the bandwidth necessary for 3 ps pulses is provided by the field broadening mechanism. Modeling of the pulse amplification shows that ~0.3 TW power is achievable that should be sufficient for producing 1-3 MeV H+ protons from the gas plasma.
BNL, Upton, Long Island, New York, USA
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
Laser acceleration of ion beams is normally realized via irradiating thin-foil targets with near-IR solid-state lasers with up to petawatt (PW) peak power. Despite demonstration of significant achievements, further progress towards practical application of such beam sources is hindered by the challenges inherent in constructing still more intense and higher-contrast lasers. Our recent studies of the radiation pressure acceleration indicate that the combination of a 10-μm CO2 laser with a gas jet target offers a unique opportunity for a breakthrough in the field. Strong power scaling of this regime holds the promise of achieving the hundreds of MeV proton beams with just sub-PW CO2 laser pulses. Generation of such pulses is a challenging task. We discuss a strategy of the CO2 laser upgrade aimed to providing a more compact and economical hadron source for cancer therapy. This include optimization of the method of the 10μm short-pulse generation, higher amplification in the CO2 gas under combined isotopic and power broadening effects, and the pulse shortening to a few laser cycles (150-200 fs) via self-chirping in the laser-produced plasma and the consecutive dispersive compression.
USC, Los Angeles, California, USA
UCLA, Los Angeles, California, USA
In the non-linear or blow-out regime of a plasma wakefield, the electrons of the accelerated bunch oscillate in a pure ion column. It was demonstrated that a single bunch can emit betatron radiation in the keV to MeV range*. In a drive/witness bunch system, the witness bunch can be injected into the ion column with a transverse momentum or initial radial offset, so that the whole bunch oscillates about the column axis as one marcro-electron. This results in a larger emitted power and higher photon energy. The energy loss due to radiation can be compensated for by the energy gain from the wakefield so that the emission process can be sustained over long distance. Detailed results will be presented about the characteristics of the witness bunch oscillations and radiation through numerical simulations** and calculations.
* S.Q. Wang, et al., Phys. Rev.Let., 88(13), 135004,(2002), D. K. Johnson et al., Phys. Rev. Lett. 97(17), 175003, (2006)
** C.H. Huang, et al., J. Comp. Phys., 217(2), 658, (2006)
Cockcroft Institute, Warrington, Cheshire, United Kingdom
The University of Liverpool, Liverpool, United Kingdom
The exact determination of the time structure of ever shorter bunches in accelerators and light sources such as for example the X-FEL, the ILC or CLIC is of high importance for the successful operation of these next-generation machines. It is also a key to the optimization of existing scientific infrastructures. The exact measurement of the time structure poses a number of challenges to the beam diagnostics system: The monitors should be non-destructive, easy to maintain and provide time resolutions down to the femtosecond regime. Several DITANET partners are active in this field. This contribution gives examples of the network’s research activities in this area with a focus on the LHC longitudinal density monitor, beam profile monitoring using electro-optics techniques and the exploitation of diffraction radiation for non-invasive diagnostics.
Cockcroft Institute, Warrington, Cheshire, United Kingdom
The University of Liverpool, Liverpool, United Kingdom
Low energetic ion beam are very attractive for a large number of fundamental physics experiments. The development of beam instrumentation for such beams poses many challenges due to the very low currents down to only a few thousands of particles per second and the resulting very low signal levels. Within DITANET, several institutions aim at pushing low energy, low intensity diagnostics beyond the present state-of-the-art. This contribution gives examples from the progress across the DITANET network in this research area.
On behalf of the DITANET consortium.
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
We report on a study of the behavior of a secondary emission chamber (SEC). We show the dependence of the SEC signal on the charge and velocity of the primary beam for beams of protons, and heavy ions including Helium, Neon, Chlorine and Iron. We fill the SEC with a selection of different gases including Hydrogen, Helium, Nitrogen, Argon, and air, studying the SEC response when it is acting as an ion chamber. We also investigate the behavior of the SEC at intermediate pressures between 10-8 torr and atmospheric pressure.
BNL, Upton, Long Island, New York, USA
A residual gas fluorescence beam profile monitor at the relativistic heavy ion collider (RHIC) has successfully recorded vertical beam sizes of Au-ion beams from 3.85 to 100 GeV/n during the 2010 beam runs. Although the fluorescence cross section of Au-ion is sufficiently large, the low residual gas in a typical vacuum chamber of <10-9 torr produces necessary weak fluorescence photons. However, with adequate CCD exposure time, the vertical beam profiles are captured to provide an independent measurement of the RHIC beam size and emittance. This beam diagnostic technique, utilizing the Au-ion beam induced fluorescence from residual gas where hydrogen is still the dominant constituent in nearly all vacuum system, represents a step towards the realization of a truly noninvasive beam monitor for high-energy particle beams.
Fermilab, Batavia, USA
CERN, Geneva, Switzerland
ESS, Lund, Sweden
SLAC, Menlo Park, California, USA
LBNL, Berkeley, California, USA
Cornell University, Ithaca, New York, USA
We report on an alternative way to measure beam fluence at NDCX-I, which is necessary for numerical simulation and planning of warm-dense-matter (WDM) experiments. So far the NDCX-I beam fluence has been characterized using a fast Faraday cup, radiation from a scintillator and tungsten foil calorimeter techniques. The present beam intensity is sufficient to melt and partially evaporate a 150 nm thick gold foil. Thermal emission (function of temperature) of the gold foil in the visible spectrum was measured during beam irradiation. A distinct shelf in the thermal emission intensity was observed after 600 ns, indicating that the sample reached the melting temperature. Using known heat capacity and latent heat of melting, the beam flux fully determines the duration of the melting shelf and the moment it appears. Using this technique we estimate an average 260 kW/cm2 beam flux over 10μs, which is consistent with values provided by the other methods.
BNL, Upton, Long Island, New York, USA
Power Supply checkout is a necessary, pre-beam, time-critical function. At odds are the desire to decrease the amount of time to perform the checkout while at the same time maximizing the number and types of checks that can be performed and analyzing the results quickly (in case any problems exist that must be addressed). Controls and Power Supply Group personnel have worked together to develop tools to accomplish these goals. Power Supply checkouts are now accomplished in a time-frame of hours rather than days, reducing the number of person-hours needed to accomplish the checkout and making the system available more quickly for beam development.
RadiaBeam, Santa Monica, USA
Penn State University, University Park, Pennsylvania, USA
BNL, Upton, Long Island, New York, USA
FRIB, East Lansing, Michigan, USA
MIT, Middleton, Massachusetts, USA
We present the design of future high-energy high-luminosity electron-hadron collider at RHIC called eRHIC. We plan on adding 20 (potentially 30) GeV energy recovery linacs to accelerate and to collide polarized and unpolarized electrons with hadrons in RHIC. The center-of-mass energy of eRHIC will range from 30 to 200 GeV. The luminosity exceeding 1034 cm-2 s-1 can be achieved in eRHIC using the low-beta interaction region with a 10 mrad crab crossing. We report on the progress of important eRHIC R&D such as the high-current polarized electron source, the coherent electron cooling and the compact magnets for recirculating passes. A natural staging scenario of step-by-step increases of the electron beam energy by builiding-up of eRHIC's SRF linacs and a potential of adding polarized positrons are also presented.
BNL, Upton, Long Island, New York, USA
Kink instability presents one of the limiting factors from achieving higher luminosity in ERL based electron ion collider (EIC). However, we can take advantage of the flexibility of the linac and design a feedback system to cure the instability. This scheme raises the threshold of kink instability dramatically and provides for higher luminosity. We studied the effectiveness of this system and its dependence on the amplitude and phase of the feedback. In this paper we present results of theses studies of this scheme and describe its theoretical and practical limitations.
UCLA, Los Angeles, California, USA
At the Neptune Laboratory at UCLA, we have developed a high-power CO2 MOPA laser system which produces world record multi-terawatt 10um pulses. The CO2 laser pulses consist of a train of 3ps pulses separated by 18ps, each with a peak power of up to 4TW and a total pulse train energy of ~100J. These relativistic laser pulses are applied for Laser Driven Ion Acceleration in an H2 gas jet operated around the critical density of 1019 cm-3 for 10um light using the Target Normal Sheath Acceleration mechanism. The laser is focused into the gas jet reaching a normalized field strength of a0~2 in vacuum. For these conditions, protons with a maximum energy of 25MeV and a narrow energy spread of ΔE/E < 1% are recorded. Initial analysis of these experimental results shows a stronger scaling of the proton energy than that predicted from the ponderomotive force, and highlights the importance of an accumulated effect of multiple CO2 laser pulses lasting over 100ps. The temporal dynamics of the overdense plasma slab are probed with a picosecond 532nm pulse and the results will be discussed.
University of Huddersfield, Huddersfield, United Kingdom
Cockcroft Institute, Warrington, Cheshire, United Kingdom
Manchester University, Manchester, United Kingdom
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
Muons, Inc, Batavia, USA
ESS Bilbao, Bilbao, Spain
UPV-EHU, Leioa, 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
Elytt Energy, Madrid, Spain
ANL, Argonne, USA
ANL, Argonne, USA
ANL, Argonne, USA
Fermilab, Batavia, USA
We have been extending and refining our model of vacuum breakdown and gradient limits and will describe recent developments. The model considers a large number of mechanisms but finds that vacuum arcs can be described fairly simply and self consistently, however simulations of individual mechanisms can be, in some cases, involved. Although based on accelerator rf data, we believe our model of vacuum arcs should have general applicability.
Fermilab, Batavia, USA
NSCL, East Lansing, Michigan, USA
NSCL, East Lansing, Michigan, USA
FRIB, East Lansing, Michigan, USA
The driver linac for the Facility for Rare Isotope Beams (FRIB) at MSU will produce primary beams of ions at ≥200 MeV/u for nuclear physics research. A dc ion beam from an ECR ion source will be pre-bunched upstream of the radio frequency quadrupole linac. A multi-harmonic buncher (MHB) was designed for this purpose, using experience gained with a similar buncher for the ReA3 re-accelerator linac, which is presently being commissioned at MSU. The FRIB MHB resonator operates with three frequencies (40.25 MHz, 80.5 MHz, and 120.75 MHz) to produce an approximately linear sawtooth in the voltage as a function of time. The three resonant frequencies are produced via two quarter-wave resonators with a common gridless gap: one resonator is driven at its fundamental mode at 40.25 MHz and its first higher-order mode (120.75 MHz), while the other is driven only at its fundamental mode of 80.5 MHz. The electromagnetic design of the MHB resonator will be presented, including the electrode design and tuning mechanisms.
Muons, Inc, Batavia, USA
JLAB, Newport News, Virginia, USA
A 20-50 MV integrated transverse voltage is required for the Electron-Ion Collider. The most promising of the crab cavity designs that have been proposed in the last five years are the TEM type crab cavities because of the higher transverse impedance. The TEM design approach is extended here to a hybrid crab cavity that includes the input power coupler as an integral part of the design. A prototype was built with Phase I monies and tested at JLAB. The results reported on, and a system for achieving 20-50 MV is proposed.
JLAB, Newport News, Virginia, USA
SLAC, Menlo Park, California, USA
A superconducting cavity of the same shape as used for the development of superconducting photo injectors has been built for the studies of high magnetic field induced Q slope due to the local heating. The multipactoring problem has been observed on the TE011 mode, 3.3GHz with magnetic field barriers. To understand and overcome this problem, 3D multipactoring simulations by Omega3P and Track3P have been done and found these to be one-point multipactors pulled out from the flat bottom surface by finite normal component of electric field. Asymmetric coupling ports on the side of the beam tube could have caused the distortion of the TE011 mode. The thermometry measurement later confirmed the predicted impact locations. A structure modification has been adopted based on the simulation prediction. More experimental results with the new geometry will allow further comparison with the 3D multipactoring simulations.
BNL, Upton, Long Island, New York, USA
The ion trapping effect is an important effect in energy recovery linac (ERL). The ionized residue gas molecules can accumulate at the vicinity of the electron beam pass and deteriorate the quality of the electron beam. In this paper, we present simulation results to address this issue in eRHIC and find best beam pattern to eliminate this effect.
IMP, Lanzhou, People's Republic of China
BNL, Upton, Long Island, New York, USA
ANL, Argonne, USA
Purdue University, West Lafayette, Indiana, USA
The APS Upgrade calls for the development and commissioning of a superconducting undulator (SCU) at the Advanced Photon Source (APS), a 7-GeV electron synchrotron. Operation of an SCU at Angstromquelle Karlsruhe (ANKA), also an electron ring, suggests that electron multipacting is consistent with the observed heat load and pressure rise, but this effect is not predicted by an electron cloud generation code. At APS it was found that while the cloud code POSINST agreed fairly well with retarding field analyzer (RFA) data for a positron beam (operated 1996-98), the agreement was less satisfactory for the electron beam. The APS data suggest that the photoelectron model is not complete. Given that the heat load is a critical parameter in designing the cryosystem for the SCU and given the experience at ANKA, a study is underway to minimize the possible contribution to the heat load by the electron cloud at the APS, the photoelectrons in particular. In this talk, the results from POSINST are presented. Preliminary tracking of the photon flux using SYNRAD3D for the APS SCU chamber is presented, and possible ways to mitigate the photoelectrons are discussed.
AES, Medford, NY, USA
ANL, Argonne, USA
TechSource, Santa Fe, New Mexico, USA
The upgrade for the ATLAS facility is designed to increase the efficiency and intensity of beams for the user facility*, **. This will be accomplished with a new CW normal conducting RFQ, which will increase both transverse and longitudinal acceptance of the LINAC. This RFQ must operate over a wide range of power levels to accelerate ion species from protons to uranium. The RFQ design is a split coaxial structure and is made of OFE copper. The geometry of the design must be stable during operation. Engineering studies of the design at different RF power levels were conducted to ensure that the geometry requirements were met. Frequency shift analysis was also completed to determine the effects of high power levels. Thermal stress analysis was completed to show that the structure frequency is repeatable.
*P.N. Ostroumov, et.al, “A New Atlas Efficiency and Intensity Upgrade Project,” SRF2009, tuppo016
**P.N. Ostroumov, et.al., “Efficiency and Intensity Upgrade of the Atlas Facility,” LINAC 2010, MOP045
INFN/LNS, Catania, Italy
GANIL, Caen, France
The single bunch selector of the Spiral2 driver uses high impedance travelling wave electrodes driven by fast pulse generators. The characteristic impedance of 100 Ω has been chosen to reduce the total power, but this non standard value requires the development of custom feed-through and transitions to connect the pulse generators and the matching load to the electrodes. The paper reviews the design of these devices.
BNL, Upton, Long Island, New York, USA
Heavy ion beams from one of the BNL Tandem Van de Graaff accelerators will be made available for radiobiology studies on cell cultures. Energy losses need to be minimized both in the vacuum window and in the air in order to achieve the ranges required for the cells to be studied. This is particularly challenging for ions heavier than iron. The design is presented of a 0.4” diameter Havar film window that will satisfy these requirements. Films as thin as 80μinches were successfully pressure tested. The final thickness to be used may be slightly larger to help in achieving pin hole free windows. We discuss design considerations and present pressure and vacuum test results as well as tests with heavy ion beams.
LLNL, Livermore, California, USA
LBNL, Berkeley, California, USA
PPPL, Princeton, New Jersey, USA
UMD, College Park, Maryland, USA
Intense heavy-ion beams have long been considered a promising driver option for inertial-fusion energy production. This paper briefly compares inertial confinement fusion (ICF) to the more-familiar magnetic- confinement approach and presents some advantages of using beams of heavy ions to drive ICF instead of lasers. Key design choices in heavy-ion fusion (HIF) facilities are discussed, particularly the type of accelerator. We then review experiments carried out at Lawrence Berkeley National Laboratory (LBNL) over the past thirty years to understand various aspects of HIF driver physics. A brief review follows of present HIF research in the US and abroad, focusing on a new facility, NDCX-II, being built at LBNL to study the physics of warm dense matter heated by ions, as well as aspects of HIF target physics. Future research directions are briefly summarized.
Fermilab, Batavia, USA
CERN, Geneva, Switzerland
ESS, Lund, Sweden
LLNL, Livermore, California, USA
UCLA, Los Angeles, California, USA
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
UCSD, La Jolla, California, USA
A two-stage Laser Wakefield Accelerator (LWFA) has been developed, which utilizes the ionization induced injection mechanism to produce high energy, narrow energy spread electron beams when the electron density is equal in both stages. However, when the densities are not equal these high quality beams are not observed. As the electron density varies across the interface between the adjacent stages the size of the ion cavity is expected to change; this results in either a reduction of the peak electron energy (for a density decrease), or in the exclusion of previously trapped charge from the first wake period (for a density increase). The latter case can be overcome if the interaction length before the density interface exceeds a threshold determined by the densities in each stage, and may provide a mechanism for enhanced energy gain.
ORNL, Oak Ridge, Tennessee, USA
ORNL RAD, Oak Ridge, Tennessee, USA
In recent years, a number of laser based H- beam diagnostics systems have been developed in the Spallation Neutron Source (SNS). This talk reviews three types of laser based diagnostics at SNS: the laser wire profile monitors at superconducting linac (SCL), the laser transverse emittance scanner at high energy beam transport (HEBT), and the laser bunch shape monitor at medium energy beam transport (MEBT). Measurement performance will be reported and major technical challenges in the design, implementation, and operation of laser based diagnostics at accelerator facilities will be addressed.
BNL, Upton, Long Island, New York, USA
CERN, Geneva, Switzerland
LBNL, Berkeley, California, USA
The Luminosity Monitors for the high luminosity regions in the LHC have been operating to monitor and optimize the luminosity since the beginning of the 2009 run. The device is a gas ionization chamber, which has the ability to resolve bunch-by-bunch luminosity as well as survive the extreme levels of radiation at nominal high intensity LHC operations. The chambers are installed at the zero degree collision angle inside the neutral absorbers 140 m from the interaction point and monitor showers produced by high energy neutral particles from the collisions. A second device, a photo-multiplier based system (PMT) located directly behind the gas ionization chamber, has been also used at low luminosities. We will present operational results for the ionization chambers for both pp and Pb-Pb collisions. These measurements include signal, noise and background studies, and correlation between the gas ionization detector and the PMT. Also, comparison with ongoing modeling efforts will be included.
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.
ANL, Argonne, USA
BNL, Upton, Long Island, New York, USA
An Electron Beam Ion Source (EBIS) being developed at the Argonne National Laboratory (ANL) will be used to charge breed rare isotopes from a 1 Ci 252Cf source, the Californium Rare Isotope Breeder Upgrade (CARIBU). Simulations have been performed using commercially available software, TriComp, to ensure the electron collector is properly designed to dissipate the electron beam power and provide adequate acceptance for the injected ion beam.
ORNL RAD, Oak Ridge, Tennessee, USA
ORNL, Oak Ridge, Tennessee, USA
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.
JLAB, Newport News, Virginia, USA
In this paper, we report the first study of beam related instabilities in lepton ring of the proposed electron-ion collider beyond the 12 GeV upgrade of CEBAF at Jefferson lab. The design parameters are consistent with PEP-II. Present studies reveal that coupled bunch and two stream instabilities are important issues and we need feedback system.
Fermilab, Batavia, USA
ANL, Argonne, USA
* V. Lebedev, "Intrabeam Stripping in H− Linacs", LINAC2010
** P. Ostroumov, "TRACK, The Beam Dynamics Code", PAC2005
LBNL, Berkeley, California, USA
High charge-state heavy-ion beams are of interest and used for a number of accelerator applications. Some accelerators produce the beams downstream of the ion source by stripping bound electrons from the ions as they pass through a foil or gas. In other accelerator systems, ions of charge state >1 are produced directly in the ion source. Heavy-ion inertial fusion (HIF) would benefit from low-emittance, high current ion beams with charge state >1. For these accelerators, the desired dimensionless perveance upon extraction from the emitter is ~0.001, and the electrical current of the beam pulse is ~ 1 A. For accelerator applications where high charge state and very high current are desired, space charge effects might present unique challenges. For example, in a stripper, the separation of charge states might create significant nonlinear space-charge forces which would impact the beam brightness. We will report on the particle-in-cell simulation of the formation of such beams for HIF, and review the possible technical approaches.
LLNL, Livermore, California, USA
LBNL, Berkeley, California, USA
A one-dimensional Vlasov-Poisson model for sheet beams is presented to provide a simple framework for analysis of space-charge effects. Centroid and rms envelope equations including image charge effects are derived and reasonable parameter equivalences with commonly employed 2D transverse models of unbunched beams are established. This sheet beam model is applied to analyze several problems of fundamental interest. First, a sheet beam thermal equilibrium distribution in a continuous focusing channel is constructed and shown to have analogous properties to two- and three-dimensional thermal equilibrium models in terms of the equilibrium structure and Deybe screening properties. Second, the simpler formulation for sheet beams is exploited to explicitly calculate the distribution of particle oscillation frequencies within a thermal equilibrium beam. It is shown that as space-charge intensity increases, the frequency distribution becomes broad which suggesting robust stability properties for beams with strong space-charge.
MPI-P, München, Germany
PPPL, Princeton, New Jersey, USA
IMP, Lanzhou, People's Republic of China
Particles in a storage ring oscillate in the longitudinal and transverse dimensions. Therefore, the beam parameters, such as tune, momentum spread, emittance and their evolution can be obtained by analyzing the beam signals in frequency domain. In this paper, the simulation result of transverse beam spectrum in HIRFL-CSR is reported, including the influence of electron cooling, power supply ripple and the misalignment between ion and electron beams. Transverse coupling would occur if the longitudinal magnetic field of electron cooling device can not be compensated. And the distribution of ion beam in transverse space is a circle due to the misalignment between ion and electron beams. In this paper, main interest is focused on the effect of power supply ripple. The tune ripple form is the sine ware with the frequency of 50Hz which is equal to that of the industrial frequency in the simulation firstly. And then different forms of current ripple of power supply are simulated for comparative analysis. Tune shift will be induced by the power supply ripple. In this paper, those factors which may affect the accumulation of HIRFL-CSR are simulated in transverse beam spectrum.
Far-Tech, Inc., San Diego, California, USA
FAR-TECH, Inc is developing a hybrid, quasi-3D model to model charge breeding of an ion beam in an electron cyclotron resonance ion source. The model is a combination of 3D mapping of the plasma background calculated by GEM1D* and 3D tracking of the ion trajectories with MCBC**. The 3D electron distribution function and electric field of the background plasma are calculated self-consistently. The test beam ions are then tracked in it using MCBC which includes Coulomb, ionization and charge exchange collisions. The exact ion trajectories in the plasma and steady state 3D ion distribution at the extraction aperture are predicted and compared with previous simulations and experiments.
* D. H. Edgell et al., Rev. Sci. Instrum. 73, 641, 2002.
** J. S. Kim et al., Rev. Sci. Instrum. 79, 02B906, 2008.
Northern Illinois University, DeKalb, Illinois, USA
JLAB, Newport News, Virginia, USA
ANL, Argonne, USA
MPI-K, Heidelberg, Germany
JINR/DLNP, Dubna, Moscow region, Russia
Aarhus University, Aarhus, Denmark
JINR, Dubna, Moscow Region, Russia
The University of Liverpool, Liverpool, United Kingdom
Cockcroft Institute, Warrington, Cheshire, United Kingdom
At present, the only place in the world where experiments utilising low-energy antiprotons can be performed is the AD at CERN. The MUSASHI trap, as part of the ASACUSA collaboration, enables access to antiproton energies in the order of a few hundreds of eV. Whilst MUSASHI produces cutting-edge research, the available beam quality and luminosity is not sufficient for collision experiments on the level of differential cross sections. A small electrostatic ring, and associated electrostatic acceleration section, is being designed and developed by the QUASAR Group. It will serve as a prototype for the future ultra-low energy storage ring (USR), to be integrated at the facility for low-energy antiproton and ion research (FLAIR). This small AD recycler ring will be unique due to its combination of size, electrostatic nature and energy of the circulating particles. In this contribution, the design of the ring is described and details about the injection section are given.
IAP, Frankfurt am Main, Germany
Funneling is a method to increase low energy beam currents in multiple stages. The Frankfurt Funneling Experiment is a model of such a stage. The experiment is built up of two ion sources with electrostatic lens systems, a Two-Beam-RFQ accelerator, a funneling deflector and a beam diagnostic system. The two beams are bunched and accelerated in a Two-Beam RFQ. A funneling deflector combines the bunches to a common beam axis. Current work is the construction and beam tests of a new beam transport system between RFQ accelerator and deflector. With extended RFQ-electrodes the drift between the Two-Beam-RFQ and the rf-deflector will be minimized and therefore unwanted emittance growth reduced. First rf-measurements with the improved Two-Beam-RFQ will be presented.
LANL, Los Alamos, New Mexico, USA
NSCL, East Lansing, Michigan, USA
Kress GmbH, Biebergemuend, Germany
GSI, Darmstadt, Germany
FRIB, East Lansing, Michigan, USA
IAP, Frankfurt am Main, Germany
The Facility for Rare Isotope Beams (FRIB) is currently in the preliminary design phase at Michigan State University (MSU). FRIB consists of a driver LINAC for the acceleration of heavy ion beams, followed by a fragmentation target station and a ReAccelerator facility (ReA3). ReA3 comprises gas stopper systems, an Electron Beam Ion Trap (EBIT) charge state booster, a room temperature radio frequency quadrupole (RFQ), a LINAC using superconducting quarter wave resonators and an achromatic beam transport and distribution line to the new experimental area. Beams from ReA3 will range from 3 MeV/u for heavy ions to about 6 MeV/u for light ions. The ReA3 RFQ, which is of the 4 rod type, is designed to accelerate ions with an Q/A of 0.2 to 0.5 from 12 keV/u to 600 keV/u. The RFQ operates at a frequency of 80.5 MHz and power levels up to 120 kW at 10% duty factor. In this paper we will report on commissioning results from the ReA3 RFQ using a H2+ and He+ beam from an auxiliary ion source.
ORNL, Oak Ridge, Tennessee, USA
The Oak Ridge Isochronous Cyclotron (ORIC) has been in operation for nearly fifty years at the Oak Ridge National Laboratory (ORNL). Presently, it serves as the driver accelerator for the ORNL Holifield Radioactive Ion Beam Facility (HRIBF), where beams are produced using the Isotope Separation Online (ISOL) technique for post-acceleration by the HRIBF 25URC tandem accelerator. Operability and reliability of ORIC are critical issues for the success of HRIBF and have presented increasingly difficult operational challenges for the facility in recent years. Earlier this year, a trim coil failure rendered ORIC inoperable for several months. This presented HRIBF with the opportunity to undertake various repairs and maintenance upgrades aimed at restoring the full functionality of ORIC and improving the reliability to a level better than what had been typical over the previous decade. In this paper, we present details of these efforts, including the replacement of the entire trim coil set and measurements of their radial field profile. Comparison of measurements and operating tune parameters with setup code predictions will also be presented.
LBNL, Berkeley, California, USA
The Neutralized Drift Compression Experiment (NDCX-II) is an induction accelerator project currently in construction at Lawrence Berkeley National Laboratory for warm dense matter (WDM) experiments investigating the interaction of ion beams with matter at high temperature and pressure. The machine consists of a lithium injector, induction accelerator cells, diagnostic cells, a neutralized drift compression line, a final focus solenoid, and a target chamber. The machine relies on a sequence of acceleration waveforms to longitudinally compress the initial ion pulse from 600 ns to less than 1 ns in ~ 12 meters. Radial confinement of the beam is achieved with 2.5 T solenoids. In the initial hardware configuration, 30-50 nC of Li+ will be accelerated to 1.2 MeV and allowed to drift-compress to a peak current of ~ 20 A. Construction of the accelerator will be completed in the summer of 2011 and will provide a worldwide unique opportunity for ion-driven warm dense matter experiments as well as research related to novel beam manipulations for heavy ion fusion drivers. The basic design of the machine and the current status of the construction project will be presented.
CLASSE, Ithaca, New York, USA
Cornell University, Ithaca, New York, USA
Northern Illinois University, DeKalb, Illinois, USA
ANL, Argonne, USA
Tech-X, Boulder, Colorado, USA
ORNL RAD, Oak Ridge, Tennessee, USA
ORNL, Oak Ridge, Tennessee, USA
The H- linac for the Spallation Neutron Source (SNS) includes an electrostatic low-energy beam transport (LEBT) subsystem. The ion source group at SNS is developing a solenoid-based LEBT, which will include MHz frequency chopping of the partly-neutralized, 65~keV, 60~mA H- beam. Particle-in-cell (PIC) simulations using the parallel VORPAL framework are being used to explore the possibility of beam instabilities caused by the cloud of neutralizing ions generated from the background gas, or by other dynamical processes that could increase the emittance of the H- beam before it enters the radio-frequency quadrupole (RFQ) accelerator.
Institute for Plasma Research, Bhat, Gandhinagar, India
Pandit Deendayal Petroleum University, Gandhinagar, India
sbanerje@ipr.res.in
sudhir@ipr.res.in
Institute for Plasma Research
BNL, Upton, Long Island, New York, USA
IAP, Frankfurt am Main, Germany
The construction and initial commissioning phase of a new heavy ion preinjector was completed at Brookhaven in September, 2010, and the preinjector is now operational. This preinjector, using an EBIS source to produce high charge state heavy ions, provided helium and neon ion beams for use at the NASA Space Radiation Laboratory in the Fall of 2010, and gold and uranium beams are being commissioned during the 2011 run cycle for use in RHIC. The EBIS operates with an electron beam current of up to 10 A, to produce mA level currents in 10 to 40 μs beam pulses. The source is followed by an RFQ and IH linac to accelerate ions with q/m > 0.16 to an energy of 2 MeV/amu, for injection into the Booster synchrotron. The performance of the preinjector is presented, including initial operational experience for the NASA and RHIC programs.
BNL, Upton, Long Island, New York, USA
Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka, Japan
The Electron Beam Ion Source (EBIS) at Brookhaven National Laboratory is a new heavy ion-projector for RHIC and NASA Space Radiation Laboratory. Laser Ion Source (LIS) with solenoid can supply many kinds of ion from solid targets and is suitable for long pulse length with low current as ion provider for RHIC-EBIS. In order to understand a plasma behavior for fringe field of solenoid, we measure current, pulse width and total ion charges by a new ion probe. The experimental result indicates that the solenoid confines the laser ablation plasma transversely.
BNL, Upton, Long Island, New York, USA
For high intensity circular proton machines, one of the major limitations is the charge exchange injection foil. The number of foil hits due to circulating beam may cause the foil to fail and cause radiation due to multiple nuclear scattering and energy straggling. This paper will describe methods to estimate these quantities without going through lengthy simulations.
LBNL, Berkeley, California, USA
The NDCX-II accelerator has been designed for target heating experiments in the warm dense matter regime. It will use a large diameter (≈ 10.9 cm) Li+ doped alumino-silicate source with a pulse duration of 0.5 μs, and beam current of ≈ 93 mA. Characterization of a prototype lithium alumino-silicate sources is presented. Using 6.35 mm diameter prototype emitters (coated and sintered on a ≈ 75% porous tungsten substrate), at a temperature of ≈1275° C, a space-charge limited Li+ beam current density of ≈ 1 mA/cm2 was measured. At higher extraction voltage, the source is emission limited at around ≈ 1.5 mA/cm2, weakly dependent on the applied voltage. The lifetime of the ion source is ≈ 50 hours while pulsing the extraction voltage at 2 to 3 times per minute. Measurements under these conditions show that the lifetime of the ion source does not depend only on beam current extraction, and lithium loss may be dominated by neutral loss or by evaporation. The thickness of the coating does not affect the emission density. It is inferred that pulsed heating, synchronized with the beam pulse rate may increase the life time of a source.
LBNL, Berkeley, California, USA
A microwave ion source has been designed and constructed for use with a sealed-tube, high-yield neutron generator. When operated with a tritium-deuterium gas mixture the generator will be capable of producing 5 · 1011 n/s in non-proliferation applications. Microwave ion sources are well suited for such a device because they can produce high extracted beam currents with a high atomic fraction at low gas pressures of 0.2 − 0.3 Pa required for sealed tube operation. The magnetic field strength for achieving electron cyclotron resonance (ECR) condition, 87.5 mT at 2.45 GHz microwave frequency, was generated and shaped with permanent magnets surrounding the plasma chamber and a ferromagnetic plasma electrode. This approach resulted in a compact ion source that matches the neutron generator requirements. The needed proton-equivalent extracted beam current density of 40 mA/cm2 was obtained at moderate microwave power levels of ∼ 400W. Results on magnetic field design, pressure dependency and atomic fraction measured for different wall materials are presented.
Muons, Inc, Batavia, USA
ORNL, Oak Ridge, Tennessee, USA
In this project we are developing an RF H− surface plasma source (SPS) with saddle (SA) RF antenna which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with a small AlN test chamber and different antennasandmagneticfieldconfigurationsweretestedin the SNS ion source Test Stand. A prototype SA SPS was installed in the Test Stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency of 1.6 mA/kW. Control experiments with H− beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma source (TPS) has been designed. A Saddle antenna SPS with water cooling is being fabricated for high duty factor testing.
ORNL RAD, Oak Ridge, Tennessee, USA
University of Tennessee, Knoxville, Tennessee, USA
ORNL, Oak Ridge, Tennessee, USA
The RF ion source at Spallation Neutron Source has been upgraded to meet higher beam power requirement. One important subsystem for efficient operation of the ion source is the 2MHz RF impedance matching network. The real part of the antenna impedance is very small and is affected by plasma density for 2MHz operating frequency. Previous impedance matching network for the antenna has limited tuning capability to cover this potential variation of the antenna impedance since it employed a single tuning element and an impedance transformer. A new matching network with two tunable capacitors has been built and tested. This network can allow precision matching and increase the tunable range without using a transformer. A 5-element broadband matching network also has been designed, built and tested. The 5-element network allows wide band matching up to 50 kHz bandwidth from the resonance center of 2 MHz. The design procedure, simulation and test results are presented.
ORNL, Oak Ridge, Tennessee, USA
ORNL RAD, Oak Ridge, Tennessee, USA
Running routinely with ~40-mA, 1-MW beams, the SNS linac is fed from the ion source with ~1ms long, ~50-mA H− beam pulses at 60 Hz. This requires the daily extraction of ~230 C of H− ions, which exceeds the routine daily production of other H− accelerator sources by almost an order of magnitude. The source service cycle has been extended from 2, to 3, to 4, and up to 5.6 weeks without age-related failures. The 7-9 kC of H− ions delivered in single service cycles exceed the service cycle yields of other accelerator sources. The paper discusses the findings as well as the issues and their mitigations, which enabled the simultaneous increase of the beam current, the duty factor, the availability, and the service cycle.
PPPL, Princeton, New Jersey, USA
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.
PPPL, Princeton, New Jersey, USA
LLNL, Livermore, California, USA
Columbia University, New York, USA
Neutralized drift compression offers an effective means for particle beam focusing and current amplification. In neutralized drift compression, a linear longitudinal velocity tilt is applied to the beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam intensity can increase more than a factor of 100 in the longitudinal direction. We have performed an analytical study of how errors in the velocity tilt acquired by the beam in the induction bunching module limits the maximum longitudinal compression. It is found in general that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may limit the compression to a factor of one hundred. However, part of pulse where the errors are small may compress to much higher values determined by the initial thermal spread of the beam pulse. Examples of slowly varying and rapidly varying errors compared to the beam pulse duration are studied.
BNL, Upton, Long Island, New York, USA
Tech-X, Boulder, Colorado, USA
JLAB, Newport News, Virginia, USA
Coherent electron cooling (CEC) has a potential to significantly boost luminosity of high-energy, high-intensity hadron-hadron and electron-hadron colliders*. In a CEC system, a hadron beam interacts with a cooling electron beam. A perturbation of the electron density caused by ions is amplified and fed back to the ions to reduce the energy spread and the emittance of the ion beam. To demonstrate the feasibility of CEC we propose a proof-of-principle experiment at RHIC using one of JLab’s SRF cryo-modules. In this paper, we describe the experimental setup for CeC installed into one of RHIC's interaction regions. We present results of analytical estimates and results of initial simulations of cooling a gold-ion beam at 40 GeV/u energy via CeC.
* Vladimir N. Litvinenko, Yaroslav S. Derbenev, Physical Review Letters 102, 114801
MIT/PSFC, Cambridge, Massachusetts, USA
SLAC, Menlo Park, California, USA
LLNL, Livermore, California, USA
BNL, Upton, Long Island, New York, USA
The high-brightness design of NSLS-II requires uncorrelated vertical RMS motion of the multipole magnets on a girder to be less than 25 nm. Also, the highly nonlinear lattice requires alignment of the multipole magnets to 30 microns. The speaker will describe the stability of the girder-magnets assembly and the factors affecting it, such as ambient ground motion and temperature fluctuations in the storage ring. Technical solutions to achieve the desired stability will be presented as well.
LBNL, Berkeley, California, USA
A unique application of the pulsed-wire measurement method has been implemented for alignment of 2.5T pulsed solenoid magnets. The magnetic axis measurement has been shown to have a resolution of better than 25 μm. The accuracy of the technique allows for the identification of inherent field errors due to, for example, the winding layer transitions and the current leads. The alignment system is developed for the induction accelerator NDCX-II under construction at LBNL, an upgraded Neutralized Drift Compression eXperiment for research on warm dense matter and heavy ion fusion. Precise alignment is essential for NDCX-II, since the ion beam has a large energy spread associated with the rapid pulse compression such that misalignments lead to corkscrew deformation of the beam and reduced intensity at focus. The ability to align the magnetic axis of the pulsed solenoids to within 100 μm of the induction cell axis has been demonstrated.
FZJ, Jülich, Germany
ANL, Argonne, USA
ATLAS (Argonne Tandem Linac Accelerator System) upgrade requires several substantial developments in accelerator technologies, such as CW heavy ion RFQ and high-performance cryomodule with low-beta cavities. The upgrade project is well advanced. The physics and engineering design of the RFQ are complete and fabrication of OFE copper parts is in progress. The 3.9-meter length RFQ is composed from 5 strongly coupled segments. High-temperature furnace brazing of the segments is planned for the summer of 2011. The RFQ design includes several innovative features such as trapezoidal vane tip modulation, compact output radial matcher to form an axially symmetric beam. The upgrade project also includes development and construction of a cryomodule containing seven 72.75 MHz SC quarter wave cavities designed for the geometrical β= 0.077 and four SC solenoids. The cavity is designed to obtain an accelerating voltage higher than 2.5 MV. The prototype cavity together with high-power capacitive coupler and piezoelectric tuner has been developed, fabricated and is being tested. This paper reports innovative design features of both RFQ and SRF linac and current status of the project.
ORNL, Oak Ridge, Tennessee, USA
NSCL, East Lansing, Michigan, USA
JLAB, Newport News, Virginia, USA
ORNL RAD, Oak Ridge, Tennessee, USA
The SNS SCL is reliably operating at 0.93 GeV output energy with an energy reserve of 10MeV with high availability. Most of the cavities exhibit field emission, which directly or indirectly (through heating of end groups) limits the gradients achievable in the high beta cavities in normal operation with the beam. One of the field emission sources would be surface contaminations during surface processing for which mild surface cleaning, if any, will help in reducing field emission. An R&D effort is in progress to develop in-situ surface processing for the cryomodules in the tunnel without disassembly. As the first attempt, in-situ plasma processing has been applied to the CM12 in the SNS SRF facility after the repair work with a promising result. This paper will report the R&D status of plasma processing in the SNS.
Cockcroft Institute, Warrington, Cheshire, United Kingdom
MPI-K, Heidelberg, Germany
UNM, Albuquerque, New Mexico, USA
The University of Liverpool, Liverpool, United Kingdom
Ions offer an increased precision in radiotherapy due to their specific depth-dose properties. This precision can only be fully exploited if exact knowledge of the particle beam properties, as well as the exact range of the particles in the inhomogeneous target, is available. The QUASAR Group has addressed the key issues in a number of different ways: Using a monolithic active pixel sensor, designed for dead time-free operation, we have developed a beam monitoring system capable of monitoring pulsed and continuous beams at typical therapeutic energies and intensities in real time during patient treatment; using a non-intrusive detector system based on the VELO detector, we will measure variations in beam properties without intersecting the beam core altogether; using liquid ionization chambers, we aim at obtaining information on the biological quality of the beam; using a simple set-up based on a silicon pixel detector, developed for the ALICE experiment, we have demonstrated the feasibility of detecting the distal edge of the Bragg peak in antiproton beams by detecting the pions resulting from pbar-nucleon annihilations. This paper gives an overview of these studies.
KURRI, Osaka, Japan
University of Fukui, Faculty of Engineering, Fukui, Japan
ITEP, Moscow, Russia
Intense heavy ion beam is an efficient tool to generate high energy density states in macroscopic amounts of matter. As result it enables to study astrophysical processes in the laboratory under controlled and reproducible conditions. For advanced experiments in high energy density physics the cylindrical target irradiated by hollow cylindrical beam is required. A new method for RF rotation of the ion beam is applied for the formation of the required hollow beam. The RF system consisting of two four-cell H-mode cavities with a resonant frequency of 297 MHz was chosen. The layout of the suggested rotating system for hollow beam formation including focusing elements is presented. The particle dynamics simulation was carried out for expecting beam parameters at ITEP Terawatt Accumulator project (ITEP TWAC). The results of simulation is considered in this paper.
BNL, Upton, Long Island, New York, USA
Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka, Japan
Warm Dense Matter (WDM) is a growing rapidly science field, which is related to planetary science and inertial fusion. It is difficult to expect the behavior because the state with high density and low temperature is completely different from ideal condition. The well-defined WDM generation is required to understand it. Moderate energy ion beam (~ 0.3 MeV/u) slightly above Bragg peak is an advantageous method for WDM because of the uniform energy deposition. Direct Plasma Injection Scheme (DPIS) with a linear accelerator has a potential for the beam parameter. The design of linear accelerator for WDM is presented.
BINP SB RAS, Novosibirsk, Russia
BNL, Upton, Long Island, New York, USA
As part of the search for a phase transition or critical point on the QCD phase diagram, an energy scan including 5 different energy settings was performed during the 2010 RHIC heavy ion run. While the top beam energy for heavy ions is at 100 GeV/n and the lowest achieved energy setpoint was significantly below RHICs injection energy of approximately 10 GeV/n, we also provided beams for data taking in a medium energy range above injection energy and below top beam energy. This paper reviews RHIC experience and challenges for RHIC medium energy operations that produced full experimental data sets at beam energies of 31.2 GeV/n and 19.5 GeV/n.
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 low-energy physics program at the Relativistic Heavy Ion Collider (RHIC), motivated by a search for the QCD phase transition critical point, requires operation at low energies. At these energies, large nonlinear magnetic field errors and large beam sizes produce low beam lifetimes. A variety of beam dynamics effects such as Intrabeam Scattering (IBS), space charge and beam-beam forces also contribute. All these effects are important to understand beam lifetime limitations in RHIC at low energies. During the low-energy RHIC physics run in May-June 2010 at beam γ=6.1 and γ=4.1, gold beam lifetimes were measured for various values of space-charge tune shifts, transverse acceptance limitation by collimators, synchrotron tunes and RF voltage. This paper summarizes our observations and initial findings.
BNL, Upton, Long Island, New York, USA
Fermilab, Batavia, USA
Electron cooling was proposed to increase the luminosity of RHIC operation for heavy ion beam energies below 10 GeV/nucleon. The electron cooling system needed should be able to deliver an electron beam of adequate quality in a wide range of electron beam energies (0.9-5 MeV). An option of using an electrostatic accelerator for cooling heavy ions in RHIC was studied in detail. In this paper, we describe the requirements and options to be considered in the design of such a cooler for RHIC, as well as the associated challenges. The expected luminosity improvement and limitations with such electron cooling system are also discussed.
JLAB, Newport News, Virginia, USA
Northern Illinois University, DeKalb, Illinois, USA
Cockcroft Institute, Warrington, Cheshire, United Kingdom
GOO Zaryad, Novosibirsk, Russia
ANL, Argonne, USA
ODU, Norfolk, Virginia, USA
SLAC, Menlo Park, California, USA
An electron-ion collider (MEIC) is envisioned as the primary future of the JLab nuclear science program beyond the 12 GeV upgraded CEBAF. The present MEIC design selects a ring-ring collider option and covers a CM energy range up to 51 GeV for both polarized light ions and un-polarized heavy ions, while higher CM energies could be reached by a future upgrade. The MEIC stored colliding ion beams, which will be generated, accumulated and accelerated in a green field ion complex, are designed to match the stored electron beam injected at full energy from the CEBAF in terms of emittance, bunch length, charge and repetition frequency. This design strategy ensures a high luminosity above 1034 s−1cm-2. A unique figure-8 shape collider ring is adopted for advantages of preserving ion polarization during acceleration and accommodation of a polarized deuteron beam for collisions. Our recent effort has been focused on completing this conceptual design as well as design optimization of major components. Significant progress has also been made in accelerator R&D including chromatic correction and dynamical aperture, beam-beam, high energy electron cooling and polarization tracking.
BNL, Upton, Long Island, New York, USA
Two electron lenses for a head-on beam-beam compensation are being planned for RHIC; one for each circulating proton beam. The transverse profile of the electron beam will be Gaussian up to a maximum radius of re=3σ. Simulations and design of the electron gun with Gaussian radial emission current density profile and of the electron collector are presented. Ions of the residual gas generated in the interaction region by electron and proton beams will be removed by an axial gradient of the electric field towards the electron collector. A method of optical observation the transverse profile of the electron beam is described.
BNL, Upton, Long Island, New York, USA
As the worlds’s first high energy polarized proton col- lider, RHIC has made significant progresses in measuring the proton spin structure in the past decade. In order to have better understanding of the contribution of u quark and d quark to the proton spin structure, collisions of high energy polarized neutron beams are required. In this paper, we discuss the perspectives of accelerating polarized light ions, like deuteron, Helium-3 and tritium. We also repre- sent simulation studies of accelerating polarized Helium-3 in RHIC.
Brookhaven National Lab., Upton, NY 11973
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.
BNL, Upton, Long Island, New York, USA
BINP SB RAS, Novosibirsk, Russia
Basic limitations on the high-intensity H− ion beam production were experimentally studied in charge-exchange collisions of the neutral atomic hydrogen beam in the Na- vapor jet ionizer cell. These studies are the part of the polarized source upgrade (to 10 mA peak current and 85% polarization) project for RHIC. In the source the atomic hydrogen beam of a 3-5 keV energy and total (equivalent) current up to 5 A is produced by neutralization of proton beam in pulsed hydrogen gas target. Formation of the proton beam (from the surface of the plasma emitter with a low transverse ion temperature ~0.2 eV) is produced by four-electrode spherical multi-aperture ion-optical system with geometrical focusing. The hydrogen atomic beam intensity up to 1.0 A /cm2 (equivalent) was obtained in the Na-jet ionizer aperture of a 2.0 cm diameter. At the first stage of the experiment H− beam with 36 mA current, 5 keV energy and ~1.0 cm-mrad normalized emittance was obtained using the flat grids and magnetic focusing. The experimental results of the high-intensity neutral hydrogen beam generation and studies of the charge-exchange polarization processes of this intense beam will be presented.
NSCL, East Lansing, Michigan, USA
FRIB, East Lansing, Michigan, USA
The Facility for Rare Isotope Beams (FRIB) will be a world-leading, DOE national users facility for the study of nuclear structure, reactions and astrophysics on the campus of Michigan State University. A superconducting, heavy-ion, driver linac will be used to provide stable beams of >200 MeV/u at beam powers up to 400 kW (~650 electrical micro-amps for uranium) that will be used to produce rare isotopes by in flight fragment separation. The selected rare isotopes will be used at velocity (~0.5 c), stopped, or reaccelerated. FRIB is a challenging technical project. An overview of the project, project challenges, and mitigating strategies will be presented.
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
Stony Brook University, Stony Brook, USA