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SANS polarization analysis at V4 SANS instrument of HMI Berlin

Measurement Science and Technology, ISSN: 1361-6501, Vol: 19, Issue: 3
2008
  • 18
    Citations
  • 0
    Usage
  • 15
    Captures
  • 0
    Mentions
  • 0
    Social Media
Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    18
    • Citation Indexes
      18
  • Captures
    15

Conference Paper Description

The V4 instrument has recently been upgraded with a He spin filter cell, placed directly in the homogeneous field B of the sample magnet, to enhance the SANSPOL option for polarization analysis. The prototype setup was still affected by: (a) a quick relaxation of the He nuclear polarization in the cell with a time constant of only ≈130 min which significantly changes the spin filter transmissions T and T for neutrons polarized parallel I and anti-parallel I to B, and (b) the absence of a flipping aid behind the sample. The usual polarization analysis procedure, expecting virtually time-independent transmissions and a second flipping device, is therefore not applicable. We present an alternative way of polarization analysis, developed especially for this case of a spin filter cell with insufficient time stability, and not requiring a second flipper. A concentrated Co-ferrofluid sample 'MFT3N' was measured with the spin filter cell for 5.5 h. From the time-dependent change of I and I caused by the change of T and T , the spin-flip and non-spin-flip components of the scattering were calculated by fitting procedures. The two-dimensional flip patterns obtained represent the purely magnetic scattering contribution, featuring the typical (sin αcos α) angular behavior expected for superparamagnetic systems. © 2008 IOP Publishing Ltd.

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