Using polarized 3 He spin filter at the SNS - Update on current development W.T. Hal Lee Spallation Neutron Source

- March ’06 Experiment at SCD, IPNS - 3He analyzer for use on the Magnetism Reflectometer - A plausible setup on HYSPEC OUTLINE

March ’06 Experiment at SCD, IPNS Polarized neutron diffraction study of the ferromagnetic semiconductor Yb 14 MnSb 11 V.O. Garlea 1, G.L. Jones 2, B. Collett 2, W.C. Chen 3,5, T.R. Gentile 3, P.M.B. Piccoli 4, M.E. Miller 4, A.J. Schultz 4, H.Y. Yan 5, X. Tong 5, M. Snow 5, B.C. Sales 1, S.E. Nagler 1, W.T. Lee 6, C. Hoffmann 6 1 HFIR, Oak Ridge National Laboratory, Oak Ridge, TN Hamilton College, Clinton, NY NIST Center for Neutron Research, Gaithersburg, MD IPNS, Argonne National Laboratory, Argonne, IL IUCF, Indiana University, Bloomington, IN SNS, Oak Ridge National Laboratory, Oak Ridge, TN 37831

In 2004, we tested online continuous optical pumping that kept the 3 He polarization stable for days using a compact online system. In 2005, an improved setup optimized at the instrument resulted in close to the highest 3He polarization archived in a prior off-line test – and remained stable for days. In 2005, we tested fast-switching of 3He polarization by adiabatic fast passage (AFP). We repeatedly switch between spin+ & spin- neutron filtering modes without using a neutron spin flipper. Previously… 2 AFP/10 min2 AFP/4 min

Experiment setup at SCD, IPNS * Laser Polarizer (light) 3He cell inside B- field & AFP coil Detector Unpolarized Neutron Polarized Neutron Sample magnet refrigurator Polarized Neutron Co Fe Analyzer

Experiment setup at SCD, IPNS 3 He polarization: 60% Online continuous optical pumping AFP 3 He polarization switching Cold sample to 6K 3kG sample field Sample magnet Detectors Neutrons Laser

Many of the peaks are magnetic Data analysis is underway… #11978#11968 h,k,lInt(+)Int(-)I(+)/I(-)lambda (A) 10,0, ,2, ,2, ,3, We have made the transition from developing a 3 He polarizer to carrying out polarized neutron scattering measurements. Snap shot of the scattering experiment The experiment: Measure magnetic moments on Mn & Sb Spin+Spin -

Construction of a 3 He-based neutron polarization analyzer for use at the Magnetism Reflectometer W. T. Hal Lee, SNS T. Gentile, W.C. Chan, NIST G. L. Jones, Hamilton College

Laser optics Coils & Shield Oven 3 He Neutron Beam Operates at neutron wavelengths from 1.8 Å to 6 Å Online continuous optical pumping during experiment to maximize and maintain a non-decaying 3 He polarization. The analyzer cell is in a uniform holding field enclosed in m-metal magnetic shielding to mitigate external magnetic interference. Use adiabatic-fast-passage for both NMR polarization monitoring and 3 He polarization flipping. This will enable the system to analyze spin-up and spin-down neutrons with fast-switching from one mode to the other. The system is located inside the detector housing. All operations will occur online 3He analyzer for Magnetism Reflectometer

“Chianti”: Max 3He polarization=74.5% for 53 W of narrowed light T1=270 h Pressure = 1.82 bar 11.7 cm ID, 8.1 cm inside length 12.9 cm OD, 10 cm outside length, 4 cm tip-off length 3He analyzer for Magnetism Reflectometer

Laser Beam Split Grating Output to 3 He cell Lase r Reflective Grating 4 2 Polarizing Beam Splitter Cube At 60 W, with 20 W feedback and 40 W output, At nm, Narrowed peak intensity = 2.25 x total un-narrowed peak intensity

Individual components tested. Polarizing 3 He test in April Laser optics Coils & Shield Oven 3 He Neutron Beam

A plausible scheme for 3 He-based neutron polarization analyzer for HYSPEC W. T. Hal Lee, SNS M. Hagen, SNS L. Passell, BNL

3He analyzer for HYSPEC Gas return Polarizing Polarized gas supply A SEOP based filling station Optical pumping may be difficult due to the shape of the cell. Refilling may be the solution. Filling station example: Max 3 He polar. =0.75, optimized at 1.5 Å. T1=200 hours, refill 75% volume every 5 hours. (Plot: for 2 Å neutrons) 3 He cell Local filling Sample Coil

HYSPEC 2 pairs of coils with diameter 400 mm & 350 mm separated by 400 mm. By applying appropriate currents to the coils, field uniformity similar to a pair of 400 mm diameter Helmholtz coils can be obtained.

SNS Instrument Layout 17 - SEQUOA 16 Vacant Field Sensitive 3 He filter, magnet magnet SERGIS SESANS Mandi Vision  -SANS 2 - Backscattering Spectrometer 1B - NOMAD 3 - SNAP 4A - Magnetism Refl. 4B - Liquids Refl. 5 - CNCS 6 - SANS 7 – Vacant 8 – Vacant 9 - VULCAN 18 - ARCS 14A, 14B, 15 HYSPEC 13 - Fundamental Physics 12 - SCD 11A – POWGEN3 10 – Vacant New concept 1A – Vacant 11B – Vacant NSE

Substantial reduction of fringe field in both radial and axial directions Shielding factor Self-shielded split-pair 10 Tesla superconducting magnet study - Results