The proposed Facility for Radioactive Ion Beams (FRIB) [1] will deliver up to 400 kW of any stable isotope to Rare Isotop Beam (RIB) production target. Operational efficiency could, under certain conditions, be improved by a system that can distribute the beam current, variable in a large dynamic range, to several independent targets simultaneously. A possible FRIB Beam Switchyard (BSY) utilizes an RF kicker with subsequent magnetostatic septum system to split the beam on microbunch to micro-bunch basis. The micro-bunches can be differentially loaded at the front-end of the Driver Linac [2]. The detailed analysis of the beam dynamics performance in the proposed BSY system is presented.
With respect to the optical system, the challenging parameters of the Continuous Electron Beam Accelerator Facility (CEBAF), a five pass recirculating electron linac, are the design goals for the emittance and energy spread of its beam. The design goals are an emittance of 2 /times/ 10/sup /minus/9/ m-rad at E < 1 GeV and an energy spread of ..delta..E/E (4sigma) of 10/sup /minus/4/. The nominal operating energy range of the machine is to be from 0.5 to 4 GeV. The optics to make this possible have been developed and are presented by other participants at this conference. The magnetic elements specified by the optics design are not, in general, extraordinary. There are, however, many magnets: 1047 corrector dipoles (/ell/ = 0.15 m, 0.3 m; B/sub 0/ less than or equal to 0.8 kG), 390 major dipoles (/ell/ = 1, 2, and 3 m; 2 less than or equal to B/sub 0/ less than or equal to 6 kG); 707 quadrupoles (0.15, 0.30, 0.6 m; B/sub 0/ less than or equal to 4 kG), 96 sextupoles (/ell/ = 0.3 m, B/sub 0/ less than or equal to 0.2 kG), 26 septa (/ell/ = 1, 2 m; 0.3 less than or equal to B/sub 0/ less than or equal to 6 kG), and one lambertson septum (/ell/ = 1 m; B/sub 0/ approx. = 4 kG), for a total of 2267 individual magnets. Furthermore, the fact that the quadrupoles, sextupoles, and correctors are to be individually powered to provide flexibility in tuning the optics lattice leads to restrictions on their design parameters. To ensure that the required magnetic parameters are achieved, all magnets will be magnetically mapped before installation. Therefore, systems to accurately and rapidly measure the multipoles and major dipoles are required. In this paper, present planning and the results of tests performed on the system to date are outlined. 5 refs., 4 figs.
Niobium quarter-wave resonators (QWRs) and halfwave resonators (HWRs) are being developed at Michigan State University (MSU) for two projects: a 3 MeV per nucleon (MeV/u) superconducting linac for re-acceleration of exotic ions (ReA3, under construction, requiring 15 resonators), and a 200 MeV/u driver linac for the Facility for Rare Isotope Beams (FRIB, under design, requiring 344 resonators). The QWRs (80.5 MHz, optimum β = v/c = 0.041 and 0.085) are required for both ReA3 and FRIB. Both QWRs include stiffening elements and frictional dampers. Nine β = 0.041 QWRs have been fabricated; seven of them have been Dewar tested successfully with a helium vessel for use in ReA3. Production and testing of ten β = 0.085 QWRs is in progress. The HWRs (322 MHz, optimum β = 0.29 and 0.53) are required for FRIB, but not ReA3. Both HWRs are designed for mechanical stiffness and low peak surface magnetic field. A prototype β = 0.53 HWR has been fabricated and tested, and a prototype β = 0.29 HWR is planned.
Betatron function parameterization of symplectic matrices is of recognized utility in beam optical computations. The traditional ''beta functions'' beta, alpha, gamma,(=(1+alpha{sup 2})/beta) and psi (the betratron phase advance) provide an emittance-independent representation of the properties of a beam transport system. They thereby decouple the problem of ''matching'' injected beam envelope properties to the acceptance of a particular transport system from the details of producing a beam of a specific emittance. The definition and interpretation of these parameters becomes, however, more subtle when acceleration effects, especially adiabatic damping (with associated nonsymplecticity of the transfer matrix), are included. We present algorithms relating symplectic representations of beam optics to the more commonly encountered nonsymplectic (x, x', y, y') representation which exhibits adiabatic damping. Betatron function parameterizations are made in both representations. Self-consistent physical interpretations of the betatron functions are given and applications to a standard beam transport program are made.
The reaccelerator system under development at the National Superconducting Cyclotron Laboratory (NSCL) will consist of a helium gas Radioactive Ion Beam (RIB) stopper, an electron beam ion trap, a cw radio frequency quadrupole (RFQ), and a superconducting linac to accelerate RIBs up to 3 MeV/u with charge-to-mass ratios (Q/A) of 0.2 - 0.4. The RFQ will operate in cw mode at a frequency of 80.5MHz to accelerate RIBs from 12 keV/u to 600 keV/u. An external multi-harmonic buncher will be used to achieve a small longitudinal emittance beam out of the RFQ. In this paper, we describe the design of the RFQ and the result of beam dynamics simulation.
A substantially less costly alternative to the Rare Isotope Accelerator (RIA) project has been developed at Michigan State University (MSU). By upgrading the existing facility at the National Superconducting Cyclotron Laboratory (NSCL), it will be possible to produce stable beams of heavy ions at energies of 200 MeV/u with beam power >65 kW. The upgrade will utilize a cyclotron injector and a superconducting driver linac at a base frequency of 80.5 MHz. A charge-stripping foil and multiple-charge-state acceleration will be used for the heavier ions. The 9 MeV/u injector will include an ECR source, a bunching system, and the existing K1200 superconducting cyclotron with axial injection. The superconducting driver linac will largely follow that proposed by MSU for RIA (1), using cavities already designed, prototyped, and demonstrated. Radioactive ion beams will be produced in a high-power target via particle fragmentation. The existing A1900 Fragmentation Separator and experimental areas will be used, along with a new gas stopper and a re-acceleration system.
The Linac-Pulse Stretcher Ring system is evaluated as a design for a high duty factor (> 90%), intense (240 μA), electron accelerator for operation in the 0.5 to multi-GeV (> 4 GeV) region. Options within this system are discussed in light of their predicted initial and operational cost, flexibility, and reliability. The ramifications of the choice of a particular cavity type, accelerating gradient, repetition rate, beam pulse length, and number of beam recirculations for the linac design are discussed both with respect to the linac itself and to the Pulse Stretcher Ring. The Pulse Stretcher Ring concept is analysed in terms of injection schemes (single or multi-turn), extraction methods (half or third integer, chromatic or achromatic), and operation parameters (machine tune and chromaticity).
