Image Test for Sim-SwiMM (14 May 2004)

The purpose here is to get the ablolute X/Y/Z position of the mask tiles and the detector plane at the same position with those as built. According to some simulations we have performed so far, we have calculated the most appropriate values as following:

detoffx  = -0.007 [cm]
detoffy  = -0.236 [cm]
detoffz  =  0.0   [cm]
maskoffx = -0.114 [cm]
maskoffy = +0.072 [cm]
maskoffz = +0.085 [cm]

Then, we performed simulation test runs with the source at infinity and at three different angles using the newly modified SwiMM geometry, where the mask tiles and the detector plane are shifted by these offsets.

(1) Source on axis, at infinity

   IMXcent  IMYcent     IMXwid   IMYwid    Peak Cts Bkg Var     SNR
  -0.00001 -0.00001    0.00277  0.00277   1612290.3  9853.0   163.8
= (-0.00057 deg, -0.00057 deg)

delta angle = (-0.034 arcmin, 0.034 arcmin)

(2) Source at 45 degrees from axis, phi = 0, at infinity (i.e. along BAT_X)

   IMXcent  IMYcent     IMXwid   IMYwid    Peak Cts Bkg Var     SNR
   1.00000  0.00000    0.00281  0.00281    609987.1  5541.2   110.2
= (45.0000 deg, 0.00000 deg)

delta angle = (0.000 arcmin, 0.000 arcmin)

(3) Source at 30 degrees from axis, phi = 90, at infinity (i.e. along BAT_Y)

   IMXcent  IMYcent     IMXwid   IMYwid    Peak Cts Bkg Var     SNR
  -0.00001 -0.57737    0.00284  0.00284    660457.7  8208.3    80.9
= (-0.00057 deg, 30.00085 deg) 

delta angle = (-0.034 arcmin, 0.051 arcmin)

Conclusion

The source location accuracy is < 0.1 arcmin obtained in the simulation with the new Sim-SwiMM geometry. Note that this is verified only for the simulation with the source at infinity. For the near field run simulation, some more checks will be needed for the source location accuracy and the consistency with the actual calibration data.

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