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S pin P olarized I nelastic N eutron S pectrometer

S pin P olarized I nelastic N eutron S pectrometer. Sungil Park, Seung-Hun Lee, and Peter Gehring. Basic principles of T riple A xis S pectroscopy Multiplexing detection modes for TAS 1. Horizontally focusing mode 2. Position-sensitive-detector (PSD) mode

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S pin P olarized I nelastic N eutron S pectrometer

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  1. Spin Polarized Inelastic Neutron Spectrometer Sungil Park, Seung-Hun Lee, and Peter Gehring • Basic principles of Triple Axis Spectroscopy • Multiplexing detection modes for TAS • 1. Horizontally focusing mode • 2. Position-sensitive-detector (PSD) mode • Data Analysis using DAVE http://www.ncnr.nist.gov/instruments/spins/

  2. d2s dWdw (Q,w) The Objective: To Measure the Neutron Scattering Cross Section Scattering triangle : Energy and momentum are conserved in the scattering process Now, how to determine ki, kf, and 2q ? • Triple-axis spectroscopy (TAS) • Time-of-flight spectroscopy (TOF)

  3. A single point at a time Sample Single Detector Neutron Source Analyzer Monochromator Conventional Triple-Axis Spectroscopy (TAS)

  4. Advantages and Shortcomings of conventional TAS Advantages: TAS is ideally suited for probing small regions of phase space Simple To Understand Shortcoming: Low data collection rate Recent Improvements Multicrystal analyzer Position-Sensitive Detector

  5. Sample D2q Monochromator Single Detector L = distance from sample to HF analyzer wa = total width of HF analyzer D2q = wa sinqa/L ~ 9 degree for Ef=5 meV at SPINS Multicrystal Analyzer Horizontally Focusing (HF) Analyzer Mode Relaxed Q-resolution Useful for studying systems with short-range correlations

  6. Sample Position-Sensitive Detector D2qi hw ~1meV Flat Analyzer qai qa Q Probes scattering events at different energy and momentum transfers simultaneously Multiplexing Detection System for TAS qai = qa + D2qi = qa - atan(x sinqa/(L+xcosqa)) kfi = ta/2sinqai Qi = ki - kfi Survey (hw-Q) space by changing the incident energy and scattering angle

  7. S.-H. Lee et al., PRL 2000 • Using Multiplexing Detection Mode • Repetitive 2q Scans with changing Ei. • Energy scans with changing T.

  8. PSD Data Analysis & Visualization Using DAVE http://www.ncnr.nist.gov/dave/

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