The NCNR Spin-Polarized Triple-Axis Spectrometer (SPINS)

The SPINS instrument is located at the heart of the cold neutron guide hall of the NIST Center for Neutron Research.

SPINS

The NCNR Spin-Polarized Triple-Axis Spectrometer (SPINS)

The SPINS instrumentwith a super-conducting magnet.

Incident Energy 14 ~ 2 meV ( 2.4 ~ 6.1 Å )

Energy Resolution 0.02 ~ 1 meV

Special Equipments Supermirror Transmission

Polarizer A stack of single crystal Si plates

with Fe/Si supermirror coatings

Multi-crystal Analyzer 11 Horizontally Focusing PG

Blades Position Sensitive Detector

3He, 20 × 25 cm2

Filters PG or Be filters before sample Be or BeO filters after sample

The SPINS Operation Modes I:Conventional Triple-Axis Spectroscopy (TAS)

TAS is ideally suited for probing small regions of phase space

Shortcoming: Low data collection rate

A single point at a time

Multicrystal analyzer and position-sensitive detector

Improvement

Monochromator

Sample

Analyzer

Single DetectorNeutron Source

The SPINS Operation Modes II: Horizontally Focusing (HF) Analyzer Mode

Monochromator

Multicrystal Analyzer

Sample

Single Detector

L = distance from sample to HF analyzerwa = total width of HF analyzer

2 = wa sina/L ~ 9 degree for Ef=5 meV at SPINS

Relaxed Q-resolution

Useful for studying systems with short-range correlations

The SPINS Operation Modes III: Multiplexing Detection System for TAS

Sample

Flat Analyzer

Position-SensitiveDetector

2i

aa

ia

i = a + 2i = a - atan(x sina/(L+xcosa))kf

i = a/2sinai

Qi = ki - kfi

Survey (h-Q) space by changing theincident energy and scattering angle

Probes scattering events at different energy and momentum transfers simultaneously

h

Q

~1meV

The SPINS Operation Modes IV: Position-Sensitive Detector in Two-Axis Mode

The PSD measures Ei-Ecutoff

Ei

S(Q,) d

Large angular acceptance = w / L ~ 11o for SPINS

SampleLow-pass Filter

PSD

L

w

Be or BeO

The filter passes only those neutrons with 0 < Ef < Ecutoff