Supermirror polarizer and beam simulations

Supermirror polarizer and beam simulations

Christopher Crawford (UKy)

NPDGamma Collaboration Meeting

ORNL, 2010-10-15

Outline

McStas simulationsof beam profile

Characterizationof SM polarizerby Swiss Neutronics

Analysis of FP12statistics

FnPB supermirror polarizer

Fe/Si on boron float glass, no Gd

m = 3.0 critical anglen = 45 channelsr = 9.6 m radius of curvaturel = 40 cm lengthd = 0.3mm vane thickness

T=25.8% transmissionP=95.3% polarizationN=2.2£1010 n/s output flux (chopped)

simulations using McStas / ROOT ntuple

McStas Simulations

Transmission Comparison Presented at collab, mtg.2007-02-23

34% -> 26% Transmission

Changes:-Fe/Si coating-No Gd undercoat-No line of sight

Transmission

Comparison of optimal stats. vs. open pedestal

afterchopper,pedestal

Comparison of optimal stats. vs. open pedestal

afterchopper,pedestal

Polarization Comparison Presented at collab, mtg.2007-02-23

95.6%Polarization

Changes:-Fe/Si coating-No Gd undercoat-No line of sight

Polarization Comparison Presented at collab, mtg.2007-02-23

95.6% -> 95.3% Polarization

Changes:-Fe/Si coating-No Gd undercoat-No line of sight

Neutron Flux vs. wavelength, position in vane

from polarimetry MRI proposal

Polarization vs. wavelength, position in vane

Neutron flux vs. Λ, Θx

Polarization vs. Λ, Θx

Beam profile before and after Smpol

before

after

horizontal vertical

Beam profile at 1st lead wall

Beam profile at 2nd lead wall

Beam profile at LH2 target

Horizontal profile vs. dist. from SMpol

Vertical profile vs. dist. from SMpol

SM polarizer characterizationby Swiss Neutronics at PSI

Specifications from SNAG

Waviness

Individual Vanes – 2

Individual Vanes – 6

Individual Vanes – 10

Individual Vanes – 14

Individual Vanes – 19

Individual Vanes – 22

Individual Vanes – 26

Individual Vanes – 26R

Reflectivity profile use in McStas simulations

McStasR+, P

Reflectivity profile use in McStas simulations

McStasR+, P

Transmission measurement at PSI

Polarization measurement at PSI

Polarization measurement data

Measurement of Flux at FP12

Americo Salas Bacci, et al.Technical Note #3

LANSCE FP12 Neutron Flux Measurement

Americo Salas Bacci,Technical Note #3

LANSCE FP12 Neutron Flux – Electronics

Fission Chamber energy spectrum

from Americo

LANSCE FP12 Neutron Flux – Electronics

Comparison of statistics at LANSCE FP12

Calculation based on: David’s estimate 2010-09-24,Americo’s note 2010-10-14, and Gericke, NIMA 611 239 (2009)

2.68x107 n/s cm2 neutron flux at 100 μA, measured with FC

3.5” collimator, 87.6 μA proton current

4966 runs (after cut) x 104/20 Hz

0.88 (air) x 0.90 (Al) x 0.88 (glass) x 0.346 (3He) transmission

0.60 capture in LH2 x 0.3017 geom. factor

0.53 pol. 3He x 0.989 SF eff. / (1+0.25) bkg. dilution

δA = 1.9 x 10-7 from above vs. 2.1 x 10-7 RMS width in A

Comparison of raw counts vs. above estimate?