VITESS Tool Generate Mirror Files

This tool generates reflectivity files that are used in the modules 'guide' and 'bender'. The parameters m, R0, Rm, Qc, W (s. Table) and the file name have to be given. If no path is given, the file will be written to the directory .../Vitess/Modules.


Parameter
Unit
Description typical values
R0 reflectivity for 0 <= Q <=Qc 0.99
m factor of supermirror 1 ... 4
Qc
[Ang-1]
crit. momentum transfer 0.02174
Rm reflectivity for Q = m Qc(Ni) 0.6 .... 0.92
W
[Ang-1]
width of the cut-off tange
W=0 causes a sharp cut-off
0 ... 0.004
mirror file name of the file into which the reflectivity curve is written -


For W=0 the reflectivity curve consists of linear functions and a sharp cut-off at Q = m Qc,Ni.

For Q > Qc and W > 0, the reflectivity R is calculated as

     R = 1/2 R0(1 - tanh((Q - m Qc,Ni)/W) (1 - a(Q - Qc))

using

     a = (Rm - R0) / (m Qc,Ni - Qc)

The product m Qc,Ni must be greater or equal Qc, because m is meant to extent the Q range to values greater than Qc.


The figure shows the reflecitvity curve for m=2, R0=0.98, Rm=0.85, Qc=0.021743 Ang-1, W=0.025 Ang-1


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