The Jefferson Lab frozen spin target

Abstract

A frozen spin polarized target, constructed at Jefferson Lab for use inside a large acceptance spectrometer, is described. The target has been utilized for photoproduction measurements with polarized tagged photons of both longitudinal and circular polarization. Protons in TEMPO-doped butanol were dynamically polarized to approximately 90% outside the spectrometer at 5 T and 200-300 mK. Photoproduction data were acquired with the target inside the spectrometer at a frozen-spin temperature of approximately 30 mK with the polarization maintained by a thin, superconducting coil installed inside the target cryostat. A 0.56 T solenoid was used for longitudinal target polarization and a 0.50 T dipole for transverse polarization. Spin-lattice relaxation times as high as 4000 hours were observed. We also report polarization results for deuterated propanediol doped with the trityl radical OX063.

Polarization Observables in γp → K+ + Λ and K+ + Σ0 Using Circularly Polarized Photons on a Polarized Frozen Spin Target

“…The FROST target consists of butanol cooled to a temperature of approximately 30 mK by means of a 3 He/ 4 He dilution refrigerator in order to maintain polarization with long relaxation times. [3] The decay products of the K + Λ and K + Σ 0 final states were detected in CLAS in Hall B of JLab [4] and data was gathered on all single and double polarization observables. The detector was built around a superconducting torus magnet, providing a field-free region around its center where the target was located.…”

Latest results from FROST at Jefferson Lab

“…A program of measurements for meson photoproduction at Jefferson Lab that used the photon tagger (capable of providing circularly and linearly polarized, as well as unpolarized, photon beams) [3] and the CEBAF Large Acceptance Spectrometer (CLAS) spectrometer in Hall B [4] has been extended by the development of a FROzen Spin Target (FROST) [5]. The hydrogen content in butanol (C 4 H 9 OH) beads, doped with the paramagnetic radical TEMPO, was used for meson production target protons in a cryogenic target.…”

A Frozen Spin Target for Neutron Diffraction Measurements of Proteins Crystals

“…The tails will be custom made, as will the sample space, including the holding coil. The coil will be hand wound, constructed of thin super conductor thermally attached to the still radiation shield, similar to the one used in reference [5]. The goal for the holding field is 0.5 T. The main difference is that the low energy neutrons would be absorbed by the Formvar insulation of the wire, so a gap for the scattered particles must remain unobstructed.…”