New improvements leading to higher polarization frozen spin HD targets at the LEGS facility

摘要

Double polarization experiments at the Laser Electron Gamma Source (LEGS) at Brookhaven National Laboratory have been performed with polarized photon beams and a polarized Hydrogen Deuteride (HD) frozen spin target. After polarizing at 15 T and 17 mK and subsequently reaching a frozen spin mode, a target was cold extracted (at 2.5 K and 0.016 T) and installed into an In-Beam Cryostat (IBC) which held the target at 0.7 T and 1.25 K. In-beam relaxation times of 13 days for polarized hydrogen and 36 days for polarized deuterium have been measured. Data were taken with 30% polarized-H and 6% polarized-D, although higher polarization levels have been achieved. Several new improvements are being implemented to improve the operating parameters of polarized HD targets. These include the fabrication of a vibration isolator to lower the polarizing temperature, the purchase of a new IBC to reach longer in-beam relaxation times with higher field and lower temperature (1 T and 200 mK), the construction of a new cold transfer cryostat with a higher field (0.13 T) to reduce polarization loss during target transfers, and the installation of a much improved NMR system for polarization calibration and online monitoring. A summary of the existing data, the ongoing modifications and projection for future performance will be discussed.