Heavy-Ion Beam Acceleration of Two-Charge States from an Ecr Ion Source

This paper describes a design for the front end of a superconducting (SC) ion linac which can accept and simultaneously accelerate two charge states of uranium from an ECR ion source. This mode of operation increases the beam current available for the heaviest ions by a factor of two. We discuss the 12 MeV/u prestripper section of the Rare Isotope Accelerator (RIA) driver linac including the LEBT, RFQ, MEBT and SC sections, with a total voltage of 112 MV. The LEBT consists of two bunchers and electrostatic quadrupoles. The fundamental frequency of both bunchers is half of the RFQ frequency. The first buncher is a multiharmonic buncher, designed to accept more than 80% of each charge state and to form bunches of extremely low longitudinal emittance (rms emittance is lower than 0.2 keV/u nsec) at the output of the RFQ. The second buncher is located directly in front of the RFQ and matches the velocity of each charge-state bunch to the design input velocity of the RFQ. We present full 3D simulations of a two-charge-state uranium beam including space charge forces in the LEBT and RFQ, realistic distributions of all electric and magnetic fields along the whole prestripper linac, and the effects of errors, evaluated for several design options for the prestripper linac. The results indicate that it is possible to accelerate two charge states while keeping emittance growth within tolerable limits.Comment: LINAC2000, MOD0

Multiple Charge State Beam Acceleration at Atlas

A test of the acceleration of multiple charge-state uranium beams was performed at the ATLAS accelerator. A 238U+26 beam was accelerated in the ATLAS PII linac to 286 MeV (~1.2 MeV/u) and stripped in a carbon foil located 0.5 m from the entrance of the ATLAS Booster section. A 58Ni9+ 'guide' beam from the tandem injector was used to tune the Booster for 238U+38. All charge states from the stripping were injected into the booster and accelerated. Up to 94% of the beam was accelerated through the Booster linac, with losses mostly in the lower charge states. The measured beam properties of each charge state and a comparison to numerical simulations are reported in this paper.Comment: LINAC2000, MOD0

Multiple-Charge Beam Dynamics in an Ion Linac

There is demand for the construction of a medium-energy ion linear accelerator based on superconducting rf (SRF) technology. It must be capable of producing several hundred kilowatts of CW beams ranging from protons to uranium. A considerable amount of power is required in order to generate intense beams of rare isotopes for subsequent acceleration. At present, however, the beam power available for the heavier ions would be limited by ion source performance. To overcome this limit, we have studied the possibility of accelerating multiple-charge-state (multi-Q) beams through a linac. We show that such operation is made feasible by the large transverse and longitudinal acceptance which can be obtained in a linac using superconducting cavities. Multi-Q operation provides not only a substantial increase in beam current, but also enables the use of two strippers, thus reducing the size of linac required. Since the superconducting (SC) linac operates in CW mode, space charge effects are essentially eliminated except in the ECR/RFQ region. Therefore an effective emittance growth due to the multi-charge beam acceleration can be minimized

Feasibility study of a 2 GeV superconducting H−H^{-} linac as injector for the CERN PS

This preliminary feasibility study is based on the availability of the CERN LEP2 superconducting RF system after LEP de-commissioning. The option that is explored is to use this system as part of a high energy H- linac injecting at 2 GeV into the CERN PS, with the aim of reliably providing at its output twice the presently foreseen transverse beam brightness at the ultimate intensity envisaged for LHC. This requires the linac to be pulsed at the PS repetition rate of 0.8 Hz with a mean beam current of 10 mA which is sufficient for filling the PS in 240 ms (i.e. about 100 turns) with the ultimate intensity foreseen for injection for the LHC. The linac is composed of two RFQs with a chopping section, a room temperature DTL, a superconducting section with reduced beta cavities up to 1 GeV, and a section of LEP2 cavities up to 2 GeV. This study deals, in particular, with the problems inherent in H- acceleration up to high energy and in the pulsed operation of SC cavities. Means for compensating microphonic vibrations in the SC cavities are considered, with the aim of reducing the final overall energy spread to the tight requirements for injection into a synchrotron. Other possible applications of such a machine are also briefly reviewed, that make use of its potential for working at a higher duty cycle than required for LHC alone

Multiplicities of secondaries in interactions of 1.8 GeV/nucleon Fe-56 nuclei with photoemulsion and the cascade evaporation model

A nuclear photographic emulsion method was used to study the charge-state, ionization, and angular characteristics of secondaries produced in inelastic interactions of Fe-56 nuclei at 1.8 GeV/nucleon with H, CNO, and AgBr nuclei. The data obtained are compared with the results of calculations made in terms of the Dubna version of the cascade evaporation model (DCM). The DCM has been shown to satisfactorily describe most of the interaction characteristics for two nuclei in the studied reactions. At the same time, quantitative differences are observed in some cases

Target fragments in collisions of 1.8 GeV/nucleon Fe-56 nuclei with photoemulsion nuclei, and the cascade-evaporation model

Nuclear photographic emulsion is used to study the dependence of the characteristics of target-nucleus fragments on the masses and impact parameters of interacting nuclei. The data obtained are compared in all details with the calculation results made in terms of the Dubna version of the cascade-evaporation model (DCM)

Report of the study group on a superconducting proton linac as a PS Injector

A proposal was made at the end of 1996 to use the large inventory of RF hardware available after the decommissioning of LEP-2 for the construction of a 2 GeV Superconducting Proton Linac (SPL) to inject directly into the PS [1.1]. The brightness of the beam in the PS at low energy would double, helping the injector complex to satisfy the requirements of the LHC and benefiting the planned proton physics programme. Additional users could also be accommodated thanks to the capability of the SPL to operate at a much larger duty factor than that required for high-energy physics. Consequently, a small study group has been set up to analyse the major technical aspects of the SPL design as well as the processes of injection and capture in the PS. This report summarises the work done so far, and provides some information about the other possible uses of the SPL beam. The feasibility of such a cascade of accelerators is confirmed, although an in-depth design study is still required before the realistic performance and detailed design of that facility can be announced