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
Dec 31, 2015
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