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Brightness of Horizontal (H5) and Vertical (H1) Cold Sources

Brightness of Horizontal (H5) and Vertical (H1) Cold Sources. Ken Andersen. H5. H1. Extract Brightness from Neutron Measurement. Needs end-of-guide position with chopper and TOF analysis Readily available on H1: Figaro, D17, PF1B Not so readily available on H5 (IN15?)

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Brightness of Horizontal (H5) and Vertical (H1) Cold Sources

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  1. Brightness of Horizontal (H5) and Vertical (H1) Cold Sources Ken Andersen

  2. H5 H1

  3. ExtractBrightnessfrom Neutron Measurement • Needs end-of-guide position with chopper and TOF analysis • Readilyavailable on H1: Figaro, D17, PF1B • Not soreadilyavailable on H5 (IN15?) • Propagatebackwards • Correct for attenuationthroughwindowmaterials etc. • Scaleusing Au-foil measurement

  4. Use spectrummeasured on Figaro (H172)

  5. Detector spectrumcorrected for chopper opening time Δt Δt distance time

  6. Al Bragg edgesmeasured on D17

  7. Al window transmission T=0.875 ⇒t=20mm

  8. Al window transmission

  9. Detector efficiency Windowthickness = 10mm - half of the total 20mm

  10. Air attenuation Ageronmeasurementat 60% humidity 50cm through air

  11. Attenuationthrough frame-overlapmirror 0.7mm Si at 3° angle

  12. Final correctedspectrum Flux (arb. units)

  13. Propagatebackwardsthrough guide

  14. Gold foil measurement August 2007 after installation of H17 guides at VS position: entrance intolevel C casemate H171 (Figaro) Φcapt=1.07×1010 n/cm2/s H172 (Granit) Φcapt=1.57×1010n/cm2/s

  15. Evaluate capture flux at VS and rescale

  16. Comparison of capture fluxes

  17. Spectral flux at Granit monochromator

  18. Brightnesses of HCS & VCS

  19. Summary • Previousestimate of 8.9Å flux at Granit was about right • Ageron VCS brightnessisslightlylow • needs 50% readjustment in the 1.5-4Å range • needs 20% readjustmentaround 9Å • HCS and VCS brightnesses are probably about the same (within 30%)

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