The silicon detector calibration file

The configuration files for the segmented silicon detector sidet_calibration_stxm[i,o].dat are used in converting the raw data (volts) for each detector segment into calibrated data (kHz). Basically, all the values will be copied into each recorded data file.

Some of the values have to be determined only once for each new detector installed, by following the instructions about detector calibration in the silicon detector manual^13.1. The IDL program detcal_gui can write them directly into a calibration file (which has to be copied manually to the appropriate location), or they can be entered into the file by hand. Others have to be updated frequently by re-calibrating the detector with the appropriate button in the microscope control program (because the leakage current in the silicon chip can change due to ambient temperature variations). After you have changed the former ones, you will have to restart sm_server, to make them become activated.

For more information about the silicon detector calibration, see Sec. 10.7 or the silicon detector manual at http://xray1.physics.sunysb.edu/user/manuals.php.

The values are (parameter example):

• calibration_time "Mon May 09 19:12:08 2005"
  A string containing data and time of the last calibration.
• u0_mvolts -126.253,-70.742,-78.201,...
  This vector of exactly 16 floats (one for each ADC channel) gives the extrapolated output voltage of the individual silicon detector segments for zero dwell time (no physical meaning). Values have to be specified in the order of detector segments (NOT ADC channels), where insignificant entries are ignored, but have to be present. They are written by the software at calibration.
• c_idark_mvolts_per_ms 86.828,40.614,60.830,...
  This vector of exactly 16 floats (one for each ADC channel) gives the dark signal per dwell time of the individual silicon detector segments, which is produced by the leakage current of the silicon chip. Values have to be specified in the order of detector segments (NOT ADC channels), where insignificant entries are ignored, but have to be present. They are written by the software at calibration.
• mvolts_per_femtocoulomb 10.060,10.170,9.917,48.954,...
  This vector of exactly 16 floats (one for each ADC channel) gives the voltage per charge collected in the individual silicon detector segments. Values have to be specified in the order of detector segments (NOT ADC channels), where insignificant entries are ignored, but have to be present. They have to be entered by hand or by detcal_gui.
• ev_per_femtocoulomb 22594.25
  A scalar double giving the photon energy necessary to produce a certain amount of charge in the chip (3.62 eV per electron-hole-pair in silicon). This value has to be entered by hand (or by detcal_gui) and should never change from the value above unless we happened to use a material other than silicon for the detector chips in the future. This parameter is not copied directly to the data file. Instead, we write photons_per_femtocoulomb to the datafile, which is ev_per_femtocoulomb divided by the photon energy of the scan (central energy in scans where the energy changes).
• deadtime_ms 0.101
  A scalar float giving the dead time of the silicon detector. The detector needs this time at the beginning of the integration cycle to get rid of the charge collected for the previous pixel, and is not sensitive to photons meanwhile. This value has to be entered by hand (or by detcal_gui). It can be read from the settings of the Quantum Composers timing module as delay plus width of the S2 pulse.
• crosstalk_matrix
  1.0000,0.0000,0.0000,...
  0.0000,1.0000,0.0000,...
  0.0000,0.0000,1.0000,...
  ...,...,...,
  This vector of exactly 16x16 floats gives the geminate crosstalk between silicon detector segments. Values have to be specified in matrix order pertaining to the order of detector segments (NOT ADC channels). Where insignificant entries are ignored, but have to be present. They have to be entered by hand or by detcal_gui.