Abstract
The Rare Isotope Accelerator (RIA) facility project includes a cw 1.4 GeV driver linac and a 100 MV postaccelerator both based on superconducting (SC) cavities operating at frequencies from 48 to 805 MHz. In these linacs more than 99% of the total voltage is provided by SC cavities. An initial acceleration is provided by room temperature radio frequency quadrupoles. The driver linac is designed for acceleration of any ion species, from protons up to 900 MeV to uranium up to 400 MeV/u. The novel feature of the driver linac is an acceleration of multiple charge-state heavy-ion beams in order to achieve 400 kW beam power. This paper presents design features of a medium-energy SC heavy-ion linac taking the RIA driver linac as an example. The dynamics of single and multiple charge-state beams are detailed, including the effects of possible errors in rf field parameters and misalignments of transverse focusing elements. The important design considerations of such linac are presented. Several new conceptual solutions in beam dynamics in SC accelerating structures for heavy-ion applications are discussed.
Highlights
The principal requirements for a high-power mediumenergy superconducting (SC) accelerator are that it be capable of producing beams of any ion, including uranium, at energies of 400 MeVnucleon and a total beam power of 400 kW
Except for the injector radio frequency quadrupole (RFQ), the entire linac is based on SC accelerating structures, which enable cost-effective cw operation, and, as discussed below, have numerous additional advantages for this application
It was shown that the front end of the driver linac can be designed for the acceptance of two charge states of uranium beam from the electron cyclotron resonance (ECR) ion source, doubling the available uranium beam power [10]
Summary
The principal requirements for a high-power mediumenergy superconducting (SC) accelerator are that it be capable of producing beams of any ion, including uranium, at energies of 400 MeVnucleon and a total beam power of 400 kW. The longitudinal and transverse acceptance of the highb section is ϳ100 times larger than the input beam emittance, which is determined by the ion source and injector RFQ Such an immense margin for emittance growth makes possible a novel operating mode for the linac, in which the beam contains multiple charge states [6,7]. [6,7], full 3D numerical simulations show such an operation to be straightforward, entailing a modest increase of longitudinal and transverse emittance, which remains well within the linac acceptance It should be ECR RFQ Low -β Section. It was shown that the front end of the driver linac can be designed for the acceptance of two charge states of uranium beam from the electron cyclotron resonance (ECR) ion source, doubling the available uranium beam power [10]. (vi) A special transition section is designed between the first two cryostats of low-b linac where beam energy is low and beam matching is extremely critical to the length of the drift space
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