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