Author Topic: WDS Detector Dead Time calibration acquisition now in StartWin application  (Read 486 times)

John Donovan

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As many know, proper calibration of the WDS detector dead time constants is important for accurate quantitative analysis, particularly at high beam currents, where count rates can often reach thousands of counts per second.

Previously, calibration of the WDS detector dead time constants was tedious, requiring many manual measurements at multiple beam currents. A few years ago, Paul Carpenter and I automated much of the process by utilizing an Excel spreadsheet macro which calls the Remote Automation Server interface to automatically acquire these calibration data from the instrument. Subsequently, this data is then pasted into another Excel spreadsheet where it is fitted and plotted to calculate the actual dead time constants for each WDS detector, which can then be utilized in quantification software such as Probe for EPMA. These Excel macro acquisition and calculation spreadsheets are posted here:

https://probesoftware.com/smf/index.php?topic=1038.msg6890#msg6890

A full discussion on editing the PFE SCALERS.DAT file (which is where these dead time constants are stored), is here:

https://probesoftware.com/smf/index.php?topic=394.0

Recently however, because Microsoft has increasingly "locked down" the execution of Excel macros and ActiveX servers with each new operating system, Paul Carpenter has suggested that we implement a method for acquiring the necessary dead time calibration data in one of the Probe for EPMA applications.

The Remote ActiveX server is still fully functional and works fine under Windows 7 and Windows 10, but for ease of use we decided that providing a "built-in" method for acquisition of the dead time calibration intensities would be useful.  Therefore the latest version of Probe for EPMA (v. 12.5.5) now includes a new version of StartWin which contains a new button for acquisition of the dead time calibration intensities, as seen here:



To perform a dead time calibration on your instrument simply tune up your WDS spectrometers to a peak of high intensity, usually Si Ka on Si metal using PET and TAP crystals, or Ti Ka on Ti metal using LiF and PET crystals. 

On Cameca instruments, one should set the "enforced" electronic dead time values to as low a value as possible (e.g., using the Cameca SX Configuration software or editing the Cameca "integer" dead times in the SCALERS.DAT file), in order to measure the actual "intrinsic" dead times on each detector, and then selecting an integer dead time slightly larger than the "intrinsic" dead time of the detector. And finally acquiring the actual dead time of the specified "enforced" dead times as described in this post:

https://probesoftware.com/smf/index.php?topic=33.msg2153#msg2153

Note that on the SX100, one can set the integer dead time to zero, but on the SXFive one cannot set it to zero, so simply set it to 1 micro-second. The "intrinsic" dead times on Cameca instruments are around 3 micro-seconds so that is OK.

On JEOL instruments, simply acquire the dead times, since there is no "enforced" electronic dead time feature present to deal with.

Then simply launch the new StartWin application, click the DeadTime button and specify a starting and stopping beam current. The software will then automatically acquire the dead time calibration intensities in the correct format for pasting into the Excel dead time calculation spreadsheet written by Paul Carpenter. 

Note that examples of these Excel acquisition macro and calculation spreadsheets are installed to the Probe Software Remote application folder (usually C:\Program Files (x86)\Probe Software\Remote), but remember, these Excel spreadsheets *must* be copied to a "writable" folder such as the Documents folder, in order that they can be updated (all Windows application folders are always read only!). 

To utilize this new dead time calibration acquisition feature in StartWin, please update as usual from the Probe for EPMA Help menu and please let us know what you think!
John J. Donovan, Pres. 
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John Donovan

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Re: WDS Detector Dead Time calibration acquisition now in StartWin application
« Reply #1 on: December 18, 2018, 12:01:18 pm »
We made a small tweak to the dead time calibration acquisition code in StartWin last night.

Because Paul Carpenter's Excel spreadsheet for calculating the dead time constants is formatted for 5 WDS spectrometers, the cut and paste operation from StartWin to Excel works perfectly for instruments with 5 WDS spectrometers.

But if your instrument has fewer than 5 spectrometers you will need to do some additional copying and pasting to allow the embedded formulas in his Excel spreadsheet to work properly.

So we decided to modify the StartWin dead time calibration acquisition code and automatically generate additional columns for the missing WDS spectrometers, if your instrument has less than 5 WDS spectrometers as seen here:



Question: are we making it just all too easy for everyone?    :-\
« Last Edit: February 11, 2019, 10:21:01 pm by John Donovan »
John J. Donovan, Pres. 
(541) 343-3400

"Not Absolutely Certain, Yet Reliable"