[mcstas-users] Radial collimator at primary side

Walz, Erik Erik.Walz at frm2.tum.de
Tue Aug 17 08:36:22 CEST 2021


Dear All,

We currently are trying to use a radial collimator in front of the  
sample (primary side) to achieve a defined gauge volume width at the  
sample position. Thus, the collimator is rotated and the neutrons  
enter from the opposite side than usual. Unfortunately, results make  
no sense at all. If we turn the collimator the other way around as a  
test, we see a reasonable image on the detector, so the component  
itself seems to be logically defined.

The file is attached below. We would be very grateful about tips or  
suggestions to solve the issue for using a radial collimator at the  
primary side.

Best regards,

Erik Walz

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# TITLE *Iron-Fe-[IM3-M] Swanson, H.E.;Tatge, E.[1954] [Iron alpha phase]
# CELL 2.886000 2.886000 2.886000 90.000000 90.000000 90.000000
# SPCGRP I M 3 M   CUBIC STRUCTURE
# ATOM FE 1 0.000000 0.000000 0.000000
# SCATTERING FACTOR  COEFFICIENTS: FE     F= 0.945 CM-12
# Reference: Acta Crystallographica (1954) 7, 464-464
#
# Physical parameters:
# sigma_coh 11.22   coherent scattering cross section (single atom) in [barn]
# sigma_inc 0.4     incoherent scattering cross section (single atom) in [barn]
# sigma_abs 2.56    absorption scattering cross section (single atom) in [barn]
# density   7.87    in [g/cm^3]
# weight    55.84   in [g/mol] (single atom)
# multiplicity 2    in [atoms/unit cell]
# Vc        24.04   volume of unit cell in [A^3]
# v_sound   4910    in [m/s]
# v_sound_l 4994    velocity of longitudinal sound in [m/s]
# v_sound_t 2809    velocity of transversal sound in [m/s]
# T_m       1811    melting temperature in [K]
# T_b       3134    boiling temperature in [K]
# At_number 26      atomic number Z
# lattice_a 2.886   lattice parameter a in [Angs]
#
# Format parameters: Lazy format <http://icsd.ill.fr>
# column_j 17 multiplicity 'j'
# column_d 6  d-spacing 'd' in [Angs]
# column_F 13 norm of scattering factor |F| in [barn^0.5]
# column_h 1
# column_k 2
# column_l 3
#
# H  K  L  THETA  2THETA D VALUE  1/D**2 SIN2*1000  H  K  L INTENSITY         /F(HKL)/       A(HKL)      B(HKL) PHA.ANG. MULT   LPG
  1  1  0  14.18  28.37   2.0407  0.2401    60.03   1  1  0    1000.0              1.8         1.78         0.00    0.00 12  17.18
  2  0  0  20.27  40.55   1.4430  0.4803   120.06   2  0  0     229.2              1.7         1.68         0.00    0.00  6   8.88
  2  1  1  25.11  50.22   1.1782  0.7204   180.09   2  1  1     561.4              1.6         1.58         0.00    0.00 24   6.13
  2  2  0  29.34  58.68   1.0204  0.9605   240.13   2  2  0     194.0              1.5         1.49         0.00    0.00 12   4.78
  3  1  0  33.22  66.44   0.9126  1.2006   300.16   3  1  0     286.8              1.4         1.40         0.00    0.00 24   3.98
  2  2  2  36.88  73.76   0.8331  1.4408   360.19   2  2  2      73.9              1.3         1.32         0.00    0.00  8   3.47
  3  2  1  40.41  80.82   0.7713  1.6809   420.22   3  2  1     354.0              1.2         1.24         0.00    0.00 48   3.13
  4  0  0  43.87  87.74   0.7215  1.9210   480.25   4  0  0      36.3              1.2         1.17         0.00    0.00  6   2.89
  3  3  0  47.31  94.62   0.6802  2.1611   540.28   3  3  0      60.8              1.1         1.10         0.00    0.00 12   2.73
  4  1  1  47.31  94.62   0.6802  2.1611   540.28   4  1  1     121.6              1.1         1.10         0.00    0.00 24   2.73
  4  2  0  50.79 101.57   0.6453  2.4012   600.31   4  2  0     104.1              1.0         1.04         0.00    0.00 24   2.63
  3  3  2  54.35 108.70   0.6153  2.6414   660.34   3  3  2      91.0              1.0         0.98         0.00    0.00 24   2.60
  4  2  2  58.08 116.15   0.5891  2.8815   720.38   4  2  2      81.6              0.9         0.92         0.00    0.00 24   2.63
  4  3  1  62.06 124.11   0.5660  3.1216   780.41   4  3  1     150.7              0.9         0.87         0.00    0.00 48   2.73
  5  1  0  62.06 124.11   0.5660  3.1216   780.41   5  1  0      75.4              0.9         0.87         0.00    0.00 24   2.73
  5  2  1  71.61 143.22   0.5269  3.6019   900.47   5  2  1     152.6              0.8         0.77         0.00    0.00 48   3.52
  4  4  0  78.54 157.07   0.5102  3.8420   960.50   4  4  0      50.4              0.7         0.72         0.00    0.00 12   5.24
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