The Spallation Neutron Source (SNS) will be the world's leading pulsed neutron source, with design beam power capability of 1.4 MW. The SNS Construction Project was completed in June 2006. The accelerator complex was successfully commissioned during the construction phase of the project in seven discrete commissioning runs. The facility is now in the first of a three year performance ramp-up phase, in which the beam power, reliability and operating time will be increased to the baseline design values of 1.4 MW, 90% and 5000 hours respectively. Meanwhile, neutron scattering instruments are being constructed and commissioned in preparation for full user operations in 2009. The progress toward bringing the SNS to its full capabilities will be presented.
Jefferson Lab, Newport News, Virginia
CEBAF is a 5-pass, recirculating cw electron linac operating at ~6 GeV. The 12-GeV Upgrade is a $300M project anticipated to receive Critical Decision 2 approval in late summer of 2007 and begin construction activities in 2008; funding for the project is provided by the DOE Office of Nuclear Physics which will double the beam energy. The new energy reach will permit significant extensions in research into non-perturbative aspects of QCD. Areas of interest are Generalized Parton Distributions (GPDs), measurements at high-xBjorken, and the use of hybrid mesons to explore the nature of quark confinement. The upgrade includes: doubling the accelerating voltages of the linacs by adding 10 new high-performance cryomodules plus the requisite expansion of the 2K cryogenics plant and rf power systems, upgrading the beam transport system from 6 GeV to 12 GeV capability through extensive re-use of existing hardware, adding one recirculation arc, adding a new experimental area and the beamline to it, building new experimental equipment for the GPD, high-xBjorken, and hybrid mesons programs. The presentation will touch on the science and give some details of the accelerator plans.
KEK, Ibaraki
CEA, Gif-sur-Yvette
LANL, Los Alamos, New Mexico
LBNL, Berkeley, California
LLNL, Livermore, California
Jefferson Lab, Newport News, Virginia
PKU/IHIP, Beijing
A free-electron laser based on a superconducting linac is under construction in Peking University. To increase FEL output power, energy recovery is chosen as one of the most potential and popular ways. The design of a beam transport system for energy recovery is presented, which is suitable for the Peking University construction area. Especially, a chicane structure is chosen to change path length at ±20 degree and M56 in the arc is adjusted for fully bunch compression.
SLAC, Menlo Park, California
Linear-field non-scaling FFAGs are proposed for multi-GeV muon acceleration and order hundred MeV/u proton or carbon medical applications. The periodic lattices, which have large momentum acceptance (factor >3), employ cells comprised of combined function magnets. In one implementation, rectangular-shaped quadrupoles are used, with the dipole component generated by off-setting the magnet centre. This feature, coupled with the large radial aperture, gives rise to orbits with large displacement and/or divergence from the quadrupole centre. The angles may be so large that there is a partial interchange of longitudinal and radial momenta. We examine two methods to devise maps (through the body field) that are third order in radial coordinate and higher order in momentum. The WKBJ approximation is concluded to be no better than the usual linear transfer matrix. A Green's function approach is carried through to non-linear mappings for the dynamical variables, which are coupled. The first partial derivative of this map (relates to tune variation) produces a linear transfer matrix which must have unity determinant. For the FFAG application, the map is comparable with numerical integration.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
JAEA/LINAC, Ibaraki-ken
KEK, Ibaraki
JAEA, Ibaraki-ken
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
JAEA, Ibaraki-ken
JAEA/LINAC, Ibaraki-ken
CERN, Geneva
CERN and RAL are working in parallel to develop Front Ends for future particle accelerators. At CERN the Front End will be part of LINAC4, a potential replacement for the Linac2 accelerator, whilst at RAL the Front End is intended to demonstrate that a high current, high quality chopped beam is achievable and that the design could be used as part of a Proton Driver for a future Neutrino Factory. The two Front End designs have many similarities and basically consist of four main components: an H- ion source, a Low Energy Beam Transport (LEBT) matching into a Radio-Frequency Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT) line with a fast beam chopper. The beam choppers are different in the two designs and it is important to compare the effectiveness of the two methods of operation. This paper describes a simulation study of high intensity beam dynamics and beam transport when the RAL and CERN MEBT designs are each fed into the same CERN structure for LINAC4.
IUCF, Bloomington, Indiana
The Low Energy Neutron Source (LENS) at Indiana University is producing neutrons by using a 7 MeV proton beam incident on a Beryllium target. The Proton Delivery System is currently being upgraded. A new DTL section will be added to increase proton beam energy from 7 to 13 MeV. A 3 MeV RFQ and 13 MeV DTL will be powered by 1 MW klystrons. The goal of this upgrade is a 13 MeV, 20 mA proton beam with duty factor more than 1%. At this power level it becomes increasingly important to make a proton beam that is uniformly distributed to prevent excessive thermal stress at the surface of the Be target. To achieve this goal two octupole magnets are being implemented in the LENS beam transport line. In this paper we discuss the experimental results of the beam intensity redistribution as well as some features inherent in tuning of the nonlinear beamline and our operational experience.
LLNL, Livermore, California
A compact Dielectric Wall Accelerator (DWA), with field gradient up to 100 MV/m, is being developed to accelerate proton bunches for use in cancer therapy treatment. The injector first generates a few nanosecond long and 40 pQ proton bunch, which is then compressed in the compression section at the end of the injector. Finally the bunch is accelerated in the high-gradient DWA accelerator to energy up to 70 - 250 MeV. The Particle-In-Cell (PIC) code LSP is used to model several aspects of this design. First, we use LSP to determine the needed voltage waveform in the A-K gap that will produce a proton bunch with the requisite charge. We then model pulse compression and shaping in the section between the A-K gap and the DWA. We finally use LSP to model the beam transport through the DWA.
ORNL, Oak Ridge, Tennessee
The chopper system for the Spallation Neutron Source (SNS) provides a gap in the beam for clean extraction from the accumulator ring. It consists of a pre-chopper in the low energy beam transport and a faster chopper in the medium energy beam transport (MEBT). The original "meander line" design of the MEBT chopper deflector was successfully tested with low power beam during the SNS linac commissioning but turned out to be unsuitable for high power beam operation due to poor cooling of the copper strip line through the dielectric substrate. We developed a new deflecting structure, with higher deflection efficiency and with rise and fall time easily customizable to match the available high voltage pulse generator. In this paper we describe design, implementation and beam tests results of the new MEBT chopper deflector.
LLNL, Livermore, California
University of Missouri - Rolla, Rolla, Missouri
As part of our ongoing development of the Dielectric Wall Accelerator, we are studying the performance of multilayer high-gradient insulators. These vacuum insulating structures are composed of thin, alternating layers of metal and dielectric, and have been shown to withstand higher gradients than conventional vacuum insulator materials. This paper describes these structures and presents some of our recent results.
ACCEL, Bergisch Gladbach
IF-UFRGS, Porto Alegre
We start by analyzing the image effects of a cylindrical conducting pipe on a continuous beam with elliptical symmetry. In particular, we derive an exact expression for the self-field potential of the beam inside the pipe without using any sort of multipole expansion. By means of a variational method, the potential for beams with varying density profiles along an elliptical shape is used to search for equilibrium solutions for intense beams. For that, we assume a uniform focusing in the smooth-focusing approximation. A curious result is that the product of the rms sizes along the ellipsis semi-axis stays constant as the pipe radius is varied. Finally, we prove that despite the nonlinear forces imposed by the image charges of an arbitrary shape conducting pipe, intense beams in uniform focusing fields preserve a uniform density in the equilibrium.
TRIUMF, Vancouver
The Enge function can be used to parametrize any element with well-defined edges. If an element is too short, however, there is no unambiguous definition of the effective edge. We first demonstrate that very little fringe field detail is needed to obtain accurate maps even up to fifth order. Then we go on to show a simple fitting algorithm that works well for short as well as long quadrupoles. The results are true whether the quads are magnetic or electrostatic.
CEA, Pontfaverger-Moronvilliers
JAEA/LINAC, Ibaraki-ken
JAEA, Ibaraki-ken
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
TIT, Yokohama
Utsunomiya University, Utsunomiya
For researches in high energy density physics and inertial confinement fusion by using heavy ion beams, high-current beam dynamics should be understood well. The heavy ion beam is longitudinally compressed by a head-to-tail velocity tilt applied from high-power induction voltage modules. In this study, emittance growth due to the longitudinal bunch compression is numerically investigated by using a particle-in-cell simulation. The code developed is dealt with three dimensional particle motions, and 2D transverse electric field is solved by Poisson equation coupled with 1D longitudinal electric field. We indicate the particle dynamics due to the non-linear longitudinal-transverse coupling effect around the stagnation point in the longitudinal compression.
Voss Scientific, Albuquerque, New Mexico
Jefferson Lab, Newport News, Virginia
Particle beam modeling in accelerators has been the focus of much effort (at great expense) since the 1950s. Several generations of tools have resulted from this process, each leveraging both the understanding provided by predecessors and the availability of increasingly powerful computer hardware. Nonetheless, the process remains on-going, in part due to innovations in accelerator design, construction, and operation that result in machines not easily described by existing tools. We discuss a novel response to this issue, which was encountered when Jefferson Lab began operation of its energy-recovering linacs. As such machines are not conveniently described using legacy software, a machine model was been built using Microsoft Excel. This interactive simulation can query data from the accelerator, use it to compute machine parameters, analyze difference orbit data, and evaluate beam properties. It can also derive new accelerator tunings and rapidly evaluate the impact of changes in machine configuration. As it is spreadsheet-based, it can be easily user-modified in response to changing requirements. Examples for the JLab IR Upgrade FEL are presented.
BNL, Upton, Long Island, New York
Uniform irradiation of biological or material samples with charged particle beams is desired by experimentalist because it reduces radiation-dose-errors which are introduced by a non-uniform irradiation of the samples. In this paper we present results of uniform beams produced in the NASA SPACE RADIATION LABORATORY (NSRL) at the Brookhaven National Laboratory (BNL) by a method which was conceived theoretically and tested experimentally at BNL. This method* of producing uniform beams in the transverse beam direction, is based on purely magnetic focusing of the beam and requires no collimation of the beam or any other type of beam interaction with materials. The method is favorably compared with alternative methods** of producing uniform beam distributions normal to the beam direction and can be applied to the whole energy spectrum of the charged particle beams that are delivered by the Booster synchrotron at BNL.
*Uniform Particle Beam Distribution Produced by Octupole Focusing N. Tsoupas et. al. NSE: 126, 71-79 (1997)
**Review of Ion Beam Therapy: Present and Future J. Alonso LBNL EPAC 2000
IF-UFRGS, Porto Alegre
We analyze the dynamics of inhomogeneous, magnetically focused high-intensity beams of charged particles. While for homogeneous beams the whole system oscillates with a single frequency, any inhomogeneity leads to propagating transverse density waves which eventually result in a singular density build up, causing wave breaking and jet formation. The theory presented in this paper allows to analytically calculate the time at which the wave breaking takes place. It also gives a good estimate of the time necessary for the beam to relax into the final stationary state consisting of a cold core surrounded by a halo of highly energetic particles.
LANL, Los Alamos, New Mexico
TechSource, Santa Fe, New Mexico
In order to better understand the two stream e-p instability issue in the LANSCE Proton Storage Ring, a new diagnostic instrument has been developed to measure the electron cloud formation and trapping in a quadrupole magnet at the LANSCE, PSR. The device called the Electron Cloud Detector (ECD) was fabricated and has successfully been installed in the PSR. Along with the Electron Cloud Detector, an additional device was developed to manipulate electrons ejected from the quadrupole and allow additional information to be obtained from ECD measurements. This paper will discuss the mechanical design and fabrication issues encountered during the course of developing both devices.