Development of Recondensing Cryostat for PAMELA

PAMELA (Particle Accelerator for MEdicaL Applications) is a design study of a novel accelerator for cancer therapy using protons and carbon ions. The accelerator utilizes the nonscaling Fixed Field Alternating Gradient (FFAG) principle and features superconducting combined-function magnets with dipole, quadrupole, sextupole and octupole field components for steering the ion beam. The proton ring for PAMELA will consist of 12 cryostats, each with three sets of the superconducting magnets having a large bore of about 250 mm. We propose to develop these cryostats using the re-condensing technology with the help of closed-cycle cryocoolers. Several issues arise, mainly due to the complex combination of superconducting magnet components and associated current leads. In this paper we address some of the key cryogenic issues and our approach in designing a cryostat suitable for PAMELA.