A cryostat to hold frozen-spin polarized HD targets in CLAS: HDice-II

• DOI: 10.1016/j.nima.2015.12.063
• Publication Date: 2016-01-07T17:47:35Z
• Authors: M.M. Lowry; C.D. Bass; A. D׳Angelo; A. Deur; G. Dezern; C. Hanretty; D. Ho; T. Kageya; D. Kashy; M. Khandaker; V. Laine; T. O׳Connell; O. Pastor; P. Peng; A.M. Sandorfi; D. Sokhan; X. Wei; M. Zarecky
• Keywords: Dilution refrigerator; Cryostat; Cryogenic temperature; Cryogenics

The design, fabrication, operation, and performance of a helium-3/4 dilution refrigerator and superconducting magnet system for holding a frozen-spin polarized hydrogen deuteride target in the Jefferson Laboratory CLAS detector during photon beam running is reported. The device operates both vertically (for target loading) and horizontally (for target bombardment). The device proves capable of maintaining a base temperature of 50 mK and a holding field of 1 Tesla for extended periods. These characteristics enabled multi-month polarization lifetimes for frozen spin HD targets having proton polarization of up to 50% and deuteron up to 27%.