5.3. TAS configuration file
RESTRAX needs a number of additional parameters compared to the matrix method of Cooper&Nathans. These parameters describe in more details the TAS components and their distances. They are stored in the configuration file ( restrax46.cfg by default). RESTRAX prompts for this file upon startup, later on the CFG command can be used to update the configuration, when the *.cfg file has been modified.
A new configuration file can be generated by filling a form on the RESTRAX server.
5.3.1. Configuration file format
The file consists of a sequence of line pairs. The first line (ignored by RESTRAX) contains a header with parameter names, in the second one the parameter values are given in the corresponding order in a free number format (do not put decimal dot where integer is expected!). All dimensions are given in [cm] except of the curvatures [1/m] of guides and focusing devices.
title (max.60 characters):
sample setup for RESTRAX 4.6
This caption would appear in the printed output.
source (shape,diameter,width,height):
0 10. 8. 8.
shape | circular (0), rectangular (1) or elliptical (2) |
diameter | used if shape=0 | width, height | used if shape >=1 |
n-guide (use,dist,length,hor1,hor2,ver1,ver2,ro,gh,gv,refh,refv):
0 10. 6300. 2.5 2.5 5. 15. 2.4E-4
1 1 1 1
This line describes the first collimator section between source and monochromator. Together with the "collimator 1" it describes a neutron guide or an in-pile collimation system. The first parameter is an integer specifying the presence of this section (>0 yes, 0 no). The other parameters have a meaning common to all collimator components (cf. below).
monochromator (chi,aniz.,poiss.,thick.,height,length,segments H&V):
0.0 1 0.3 0.3 12.0 10.0 1 3
chi | crystal cutting angle [deg], 0 for the symmetric Bragg reflection |
aniz | ratio of the vertical and horizontal mosaicity |
poiss | Poisson number for the elastically bent crystals (usually about 0.3) |
thick.,height,length | monochromator dimensions |
segments H&V | number of crystal segments in horizontal and vertical direction; if the crystal is perfect (ETAM=0), only vertical segments are considered and the horizontal curvature is interpreted as elastic bending |
analyzer(chi,aniz.,poiss.,thick.,height,length,segments H&V):
0.0 1 0.3 0.3 12.0 10.0 1
3
Analyzer parameters. Syntax and meaning are the same as for the monochromator.
detector (shape,diameter,width,height):
1 4.0
3.0 5.0
Detector window. Syntax and meaning are the same as for the source.
distances (l1,l2,l3,l4):
900. 210. 150. 70.
Distances between the source, monochromator, sample , analyzer and detector. If the n-guide is present, the first distance is measured from its exit, otherwise from the source.
1st collimator (dist,length,hor1,hor2,ver1,ver2,ro,gh,gv,refh,refv):
236. 534. 8.05 5. 9.05 11. 0. 0. 0
. 1 1
2nd collimator (dist,length,hor1,hor2,ver1,ver2,ro,gh,gv,refh,refv):
87. 35. 4. 4. 7. 7. 0. 0. 0.
1 1
3nd collimator (dist,length,hor1,hor2,ver1,ver2,ro,gh,gv,refh,refv):
60. 35. 4. 4. 7. 7. 0. 0. 0.
1 1
4th collimator (dist,length,hor1,hor2,ver1,ver2,ro,gh,gv,refh,refv):
35. 20. 4. 4. 12. 12. 0. 0. 0.&nbs
p; 1 1
These 4 items describe the collimators between the source (after n-guide), monochromator, sample , analyzer and detector. The meaning of parameters is described in the section on collimator components.