High level of 3He polarization maintained in an on-beam 3He spin filter using SEOP

Abstract

Maintaining high levels of 3 He polarization over long periods of time is important to many areas of fundamental and particle beam physics. Long measurement times are often required in such experiments and the data quality is a function of the 3 He polarization. This is the case for neutron scattering where the 3 He can be used to analyze the spin of a scattered neutron beam and relatively small fluxes of polarized neutrons leads to experiment times longer than several days. Consequently the Jülich Centre for Neutron Science (JCNS) is developing spin-exchange optical pumping (SEOP) systems capable of polarizing the 3 He gas in place on a typical neutron instrument. Using a polarizer device we constructed a high level of 3 He polarization of 81 % ±2 %was maintained with good time stability. Such levels of polarization maintained over time will be able to reduce the measurement times for such experiments and eliminate time dependent data corrections.

An ultra-compact in-situ3He polarizer for high Q-range SANS: on-beam test and future upgrades

“…This box also provides environmental protection and increased laser security. Two such lasers are used to pump the large 0.85 liter volume of the 3 He NSF cell used on reflectometer MARIA [12], however for the application in question, where a 0.17 litre cell is used one laser is sufficient. Figure 3.…”

Polarization analysis for the thermal chopper spectrometer TOPAS

“…Due to the high incident neutron energies E ≤ 150 meV corresponding to λ ≥ 0.74Å and the convergent focused incoming beam and large area detector array, TOPAS will use 3 He spin filter cells for both polarization [10] and analysis [11]. The incident beam polarizer will be placed on a guide changer before the final Fermi chopper as shown in Fig.…”

“…4. This 3 He spin filter polarizer is based upon the experience gained with the MARIA insitu polarized 3 He neutron spin filter analyzer [10]. In this system a polarization of 80% was demonstrated and maintained over several days using the glass cell J1.…”

“…The MARIA magic-box is 40 cm wide, 30 cm tall and 70 cm long to accept the 12.5 cm diameter 3 He cell, optics and widearea scattered neutron beam on MARIA. The TOPAS magic-box will have a simple rectangular geometry and be 27 cm tall, 20 cm wide and 50 cm long with a vertical field much like a 2/3 scale version of the magic-box and system described in [10] but will use the upgraded volume Bragg grating narrowed lasers shown in Fig. 2 as in the current revision of the MARIA analyzer and those in [12].…”

In-situ compact3He neutron spin polarizer based on a magneto-static cavity with built-in NMR coils

“…In addition, a 3 He polarizer has a wide acceptance angle and creates a smaller amount of background gamma radiation owing to its low neutron activation [2]. Such merits enable the 3 He polarizer to be widely used for neutron experiments in fundamental particle physics or material researches involving neutron radiography, neutron diffraction, neutron reflectometry, neutron interferometry, and small-angle neutron scattering [3,4].…”