ITEP, Moscow
All known ion beam transport systems for medical applications with or without GANTRY are very large, complicated and expensive. Its cost is comparable with accelerator facility itself. It stimulates search of beam transport and distribution systems that allow reducing their cost and sizes considerably keeping treatment efficiency. Two such transport system are considered in the present paper. The first one is based on bend magnets that are rotated around their center of mass with movement of patient in horizontal position around of magnets. The second one uses stationary magnets with movement of patient in horizontal position in vertical plane. It is shown that the proposed ion transport systems provide treatment efficiency comparable with GANTRY at considerably lower sizes, mechanical complexity and cost.
ORNL, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC05-00OR22725
The SNS Ring has now been operating for about 2.5 years, and our march continues to increase the beam power to the design value of 1.4 MW. The Ring is a loss-limited machine, and in general the radioactivation levels are good, but there are some unanticipated hot spots that we are working to relieve. Beam optics functions have been measured using the model independent and orbit response matrix methods, and our results will be compared to the ideal model. High-intensity beam profiles measurements show space-charge effects, and these will be compared to model calculations. We will also discuss the status of equipment upgrades that are now in progress in the high-energy beam transport momentum dump, the injection-dump beam line, and in the ring-to-target beam line.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
Wire Scanner Monitors (WSMs) and Bunch Shape Monitors (BSMs) are going to be installed in the entrance part of ACS (Annular Coupled Structure) section at the energy upgraded J-PARC linac. WSMs are used to measure transverse beam profiles, and BSMs are used to measure longitudinal beam profiles. Both are used to match beams from upstream SDTL (Separated-type Drift Tube Linac) accelerator cavities to ACS. Only a BSM will be installed in the beggining and the best location for the BSM has been chosen through studies of the tuning schemes.
G.H. Gillespie Associates, Inc., Del Mar, California
STAAR/AWR Corporation, Mequon
Funding: Work at G. H. Gillespie Associates, Inc. funded by the U.S. Department of Energy SBIR grant number DE-FG02-05ER84360
An automated procedure for the calculation of particle transfer maps using computed magnetic field data has been developed for several types of magnetic quadrupoles. The Automated Transfer Map Generator (ATMG) software used for these calculations combines the Analyst program and specialized modules of the Particle Beam Optics Laboratory (PBO Lab). Analyst's scripted solids capability is used to develop models of different magnet concepts. The geometry and material attributes for a given magnet concept are encapsulated by a small number of magnet parameters. Quadrupoles of the same basic concept can be simulated by using different values for the magnet parameters. The three-dimensional magnetic field solver (MS3p) of the Analyst program is used to obtain the fields. New PBO Lab modules are used to automate the field computation, and then calculate the transfer maps and matrices through third-order using the Venturini-Dragt method. Examples for three different types of magnetic quadrupole lenses are presented: electromagnetic air-core, electromagnetic iron-core, and rare-earth permanent magnet quadrupoles.
NIRS, Chiba-shi
TIT, Yokohama
The screen monitor system is an important tool for beam diagnostic of the high-energy-beam transport line at the Heavy-Ion Medical Accelerator in Chiba (HIMAC). We have developed a very thin fluorescent film and high speed charge-coupled-device camera. Because the fluorescent film is very thin (ZnS:Ag 2mg/cm3), the beam is measured with semi-non-destructively. Consequently we can use more than two monitors at the same time and multiple locations. Moreover we employ a high-speed three-processer for image processing, the system can be applied for online monitoring and interlock system (100Hz). When the beam profile measured by this system is inevitably changed over the setting tolerance during therapeutic irradiation for the patient, the beam is immediately turned off. The design and measurement result by irradiation test are discussed.
ORNL, Oak Ridge, Tennessee
Funding: *SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
The new SNS Allison emittance scanner measures emittances of 65 kV ion beams over a range of ± 116 mrad. Its versatile control system allows for time-dependent emittance measurements synchronized by an external trigger, and therefore is suited for studying pulsed systems. After a programmable delay the system acquires a variable array of beam current measurements, each averaged over a changeable time span. The baseline of the current measurements are determined by averaging a fraction of 1 ms shortly before the start of the ion beam pulse. This paper presents the time evolution of emittance ellipses during the 1 ms H- beam pulses emerging from the SNS test LEBT, which is important for loss considerations. In addition it presents the time evolution of emittance ellipses during the 3 week active lifetime of an SNS H- source, which is an operational issue. Additional emittance data characterize the dependence on the electron-dump voltage, the extractor voltage, and the LEBT lens voltages, all of which were critical for reaching the 38 mA baseline H- beam current. Emittance data for the dependence on the beam current highlight the challenges for the SNS power upgrade.
KEK, Ibaraki
KURRI, Osaka
Straight section in scaling FFAG accelerator has been explored and scaling law for straight section has been investigated. Under these studies, dispersion suppressed straight section, which could be useful for efficient RF acceleration, can be designed in ordinary scaling FFAG ring accelerator.
LBNL, Berkeley, California
LLNL, Livermore, California
Funding: Supported in part by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
In 1958, Courant and Snyder analyzed the problem of alternating-gradient beam transport and treated a model without focusing gaps or space charge.* We extend their work to include the effect of gaps (still neglecting space charge) and obtain exact solutions for the matched envelopes.** We assume a periodic lattice of quadrupole doublets. The focus sections have piecewise-constant field strength and equal lengths, but the zero-field drift sections have arbitrary length ratio. We obtain and show the exact envelope results as functions of z for various field strengths, occupancies (eta), and gap-length ratios. We show the peak envelope excursion as a function of field strength or phase advance (σ) for various cases. There is a broad σ range over which the minimum peak varies less than ± 1%. For eta = 1, this range is 64 to 98 degrees; for eta = 0.5, it is 62 to 96 degrees. In the lowest stable band, the optimum field strength rises by 37.6% when eta is reduced from 1.0 to 0.5 and rises by 76.0% if also one gap has zero length. In the second stable band, the higher field strength accentuates the remarkable compression effect predicted for the FD (gapless) model.**
*E.D. Courant and H.S. Snyder, Ann. Phys. 3, 1 (1958).
**The present work extends a recent envelope analysis carried out without gaps (O.A. Anderson and L.L. LoDestro, submitted to Phys. Rev. ST-AB).
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
A scaling fixed field alternating gradient (FFAG) accelerator provides large momentum acceptance despite of constant field in time. Optical functions are nearly the same for large momentum range. We have designed a straight beam transport (BT) line using a scaling FFAG type magnet which has a field profile of x^k, where x is the horizontal coordinate and k is the field index. This BT line has very large momentum acceptance as well, for example ±50%, and optical functions do not practically depends on momentum. We also designed a dispersion suppressor at the end by the combination of a unit cell with different field index k so that the momentum dependence of orbits should be eliminated at the exit. An obvious application of this design is the BT line between FFAG accelerator and gantry of a particle therapy facility. However, we also consider it for the transport of muon beams, which have large emittance and momentum spread. This could be an alternative to the conventional BT line with solenoid or quadrupole because of the strong focusing nature of quarupole and the large momentum acceptance like solenoid.
IF-UFRGS, Porto Alegre
Funding: Work supported by CNPq, Brazil and the US-AFOSR under Grant No. FA9550-06-1-0345.
In this paper, we investigate the combined envelope-centroid dynamics of relativistic continuous charged beams transported through a uniform focusing field and surrounded by a conducting wall. For such beams, the conducting wall screens the electric field but allows magnetic field penetration, enhancing the induced charges effect on the beam transport. As a consequence, in contrast to the case of nonrelativistic beams where the walls are shown to have little effect*, relativistic beams may have their centroid motion severely affected, leading to limitations in the total current and area occupied by the beam inside the conductor. Self-consisted simulation are used to verify the findings.
*K. Fiuza, F. B. Rizzato, and R. Pakter, Phys. Plasmas, 13, 023101 (2006).
Muons, Inc, Batavia
Hampton University, Hampton, Virginia
JLAB, Newport News, Virginia
Fermilab, Batavia
Funding: Work supported in part in part by DOE contract DE-AC02-07CH11359 and DOE STTR Grant DE-FG02-05ER86253
In order to achieve cooling of muons in addition to 6D helical cooling channel (HCC) [1], we develop a technique based on a parametric resonance. The use of parametric resonances requires alternating dispersion, minimized at locations of thin absorbers, but maximized in between in order to compensate for chromatic aberrations [2]. These solutions can be combined in an Epicyclic Helical Cooling Channel (EHCC) that meets requirements of alternating dispersion of beam periodic orbit with best conditions for maintenance of stable beam transport in a continuous solenoid-type field [3]. We discuss here basic features and new simulation results for EHCC.
LANL, Los Alamos, New Mexico
Funding: This work is supported by the U. S. Department of Energy, Contract DE-AC52-06NA25396.
The Los Alamos Neutron Science Center simultaneously provides both H- and H+ beams to several user facilities. Opposite polarity beams are usually accelerated in the linac during the same macropulse when beam-loading limitations are not exceeded. Presently, the Weapons Neutron Research (WNR) H- and Isotope Production Facility (IPF) H+ beams are accelerated simultaneously during the same macropulse. The amplitude of the cavity field in the last 201-MHz buncher, located in the common transport just upstream of the DTL, is a compromise between the optimal values for each beam. Recent beam dynamics studies have shown that implementing a debuncher cavity in the H- low-energy beam transport would allow for more optimal operation of both beams. For this application where space is limited, a compact 201-MHz quarter-wave cavity will be used. This paper will report on the beam dynamics simulations performed and the quarter-wave cavity design being developed to address this issue.
SIGMAPHI S.A., Vannes
CEA, Gif-sur-Yvette
Funding: ANR contract nb : NT05-141853
This paper presents an alternative design of the magnet for the RACCAM project. The aim of this collaboration is to study and build a prototype of a scaling spiral FFAG as a possible medical machine for hadron therapy. The magnet was first designed with a variable gap to produce the desired field law B=B0(r/r0)^k. The key feature in the “scaling” behavior of the magnet is in getting the fringe field extent to be proportional to the radius. Although the fringe field is increasing with gap dimension, we have obtained quit constant tunes in both horizontal and vertical by using a variable chamfer. An alternative magnet design was then proposed with parallel gap and distributed conductors on the pole to create the required field variation. This solution requires about 40 conductors along the pole and much more power than the gap shaping solution. We expect a much better tune constancy even without variable chamfer. We can think about an “hybrid” magnet with parallel gap at small radii and gap shaping afterward. Such a solution could take advantages of both solutions.