Subject: grey filter factor

Carol Anne,

Let GF be defined as the grey filter seting (31 for fully open).
The transmission fraction is then T=(1+GF)/32

Let F be the probability of an accepted event following a grey filter event.
This is not like the random case, but depends on the way Ib has implemented
his table:

F= (31-GF)/(1+GF) for GF>15   and F=1 for GF<=15

The new correction factor to be applied to get the corrected count rate 
is then:

CF = 1/(1- A*F), where A is determined to be 0.10 for JEM-X1 and 0.11 
for JEM-X2.
(see attached plots of  observed rates  compared to expected, that is  
then  (1-A*F), where
we then can read A off as the  level part of the curve).

So the "true" rate R is R_true=R_current*CF = R_obs/LIVE *CF

Søren

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