SCALERS.DAT Lines 21-41
Line 21-23 (peaking cycles, P/B and minimum intensities)
30 30 30 30 "maximum peaking cycles"
5. 5. 5. 5. "minimum peak to background"
10. 10. 10. 10. "minimum peak intensity"
These parameters are used to define additional peak centering default parameters for the interval halving and parabolic peak center. The maximum peaking cycles is used to specify the maximum number of interval halving attempts the program will make to find the peak center. If the number of peaking cycles is small or the peak start size is small or the peak is too far from the starting position, the peak center may fail. The allowable range is 5 to 50 maximum peak cycles.
The minimum peak to background is the minimum peak to background ratio that the program will attempt a peak center on. The values must be greater than 1.5.
The minimum peak intensity is the minimum peak intensity in counts per second that the program will attempt a peak center on. The values must be greater than 10 counts per second.
Line 24-25 (PHA baseline, window default voltages)
1. 1. 1. 1. "default PHA baseline voltages"
10. 10. 10. 10. "default PHA window voltages"
The default baseline and window PHA values are specified on this line. The values must be greater than zero.
Line 26-27 (PHA gain and bias defaults)
16. 16. 64. 32. "default PHA gain"
1350. 1880. 1850. 1350. "default detector bias"
The default gain and bias values are specified on this line. The values must be greater than zero.
Line 28-31 (PHA baseline, window, gain and bias scale factors)
1. 1. 1. 1. "PHA baseline full scale factors"
1. 1. 1. 1. "PHA window full scale factors"
1. 1. 1. 1. "PHA gain scale factors"
1. 1. 1. 1. "Detector bias scale factors"
The PHA scale factors are used for PHA hardware that does not accept 0 to 10 volt control voltages. If the PHA hardware does give a 10 volt output for a 10 volt input control voltage then the scale factors will be 1. If the PHA hardware outputs full scale (10 volts) using a lower input control voltage, then the scale factors should be adjusted. For example, if the PHA hardware wants a .33 volt input to output 10 volts, then set the appropriate PHA scale factor to .33 for that channel. The values must be greater than 0.0.
These parameters are no longer utilized by any of the current instrument interfaces.
Line 32 (spectrometer Roland circle radius in mm)
127. 127. 127. 127. "Roland Circle (mm)"
The values on this line are used to specify the spectrometer Roland circle. These values are not used at this time. The values must be greater than 0.0.
Line 33 (crystal flip delays in seconds)
0 0 0 0 "Crystal flip delays"
The values on this line are used to define the type and duration of the crystal flip delay used to wait for a crystal flip to complete. If the value is greater than zero then the program will simply delay for the duration specified before allowing the program to continue.
Line 34 (spectrometer offset warning factors)
400. 400. 400. 400. "Spec offset warning factors"
The values on this line are used to define the size of the maximum offset for a spectrometer from its theoretical position for the purposes of printing a warning message to the log window. If the actual spectrometer position offset is less than the spectrometer range (as defined in the MOTORS.DAT file) divided by this spectrometer offset warning factor then the warning will not be printed. The default value is 400.
Line 35 (Cameca integer deadtimes)
0 0 0 0 "Cameca integer deadtimes"
This line is used to explicitly specify the integer deadtime constants used to set the Cameca PHA hardware (non-extendible or "enforced" deadtime. Therefore this data is used only by the Cameca SX100/SXFive hardware interface and the values are not accessible from within the program. These integer deadtime values are distinct from the single precision deadtimes specified on line 72-77 below which are used to perform the actual deadtime correction in the analysis routines.
The typical procedure is to set the deadtimes on the Cameca PHA hardware all to zero and then to measure the "intrinsic" deadtime of the system using a range of beam currents from approximately 10 to 200 nA on a pure metal x-ray line such as Si Ka (PET and TAP) or Ti Ka (PET and LIF). A sufficient counting time should be used to obtain .2% precision or better. The best method is to find the "worst case" deadtime for each spectrometer since the deadtimes may vary somewhat as a function of detector bias and x-ray line energy.
Assume that the "intrinsic" deadtimes measured (when all spectrometers are set to "DTIM"=0) are 2.23, 3.14, 3.45, 3.78 and 2.15. The next step would be to set the DTIM deadtime parameter for each spectrometer to a value large enough to completely "mask" this intrinsic" deadtime, that is values of 3, 4, 4, 4 and 3. Now since these integer deadtime are not accurately set by the Cameca hardware, the operator must now re-run the deadtime calibration measurement using these new values and note the actual deadtimes. In this case depending on the instrument, the measured deadtimes will be somewhat larger, say, 3.75, 4.65, 4.12, 4.89 and 3.32.
In the example just described, the "DTIM" values of 3, 4, 4, 4 and 3 should be entered on line 35 for setting the Cameca hardware and the measured values that correspond to them, that is, 3.75, 4.65, 4.12, 4.89 and 3.32 should be entered on line 13 above to use in the software correction.
The integer "DTIM" deadtime values must be between zero and ten. If a value of zero is read, then the program will load the single precision deadtime from line 13 and truncate to integer each value for setting the Cameca PHA hardware to an approximate value.
Lines 36-41 (Bias scan low and high, gain scan low and high, scan baseline and window values)
0 0 0 0 "unused"
1500 1500 1500 1500 "Bias scan low limits"
1800 1800 1800 1800 "Bias scan high limits"
4 4 4 4 "Gain scan low limits"
128 128 128 128 "Gain scan high limits"
4. 4. 4. 4. "Scan baselines"
0.1 0.1 0.1 0.1 "Scan windows"
These lines are used to specify the PHA bias and gain scan parameters used in the PHA dialogs. This characterization of the detector electronics is essential for non-Cameca (JEOL) instruments where the gain can only be adjusted in coarse steps. Normally one sets the bias scan baseline at 4 volts, the window at 0.1volts above the baseline and scans the detector bias between 1500 and 1800 volts to determine what bias value is necessary for the x-ray peak to obtain a 4 volt level. Note, the low bias scan voltage must be above the bias “plateau” for the correct determination of the bias value.
For other instruments the gain can be scanned to determine the actual gain necessary for a given detector bias. Both scan procedures use the same scan baseline and windows settings. The default count time and interval values are specified in the PROBEWIN.INI file in the [pha] section. Contact Paul Carpenter or John Donovan for more information on this issue.