Instructions for using the mcaprog X-Ray Powder Diffraction Scanning Program
	Guy Jennings, jennings@anl.gov
	This document describes the operation of the DOS software for running the powder diffraction system situated in MSD building 223. When you use the powder machine the scanning software should be running already. If it isn't, double-click the mcaprog icon to start it. The main screen should look like this: The upper graph panel shows the diffraction scan being taken, the lower graph panel shows the count rate variation across the multi-element detector channels. (If only one panel is showing, press function key 11 (F11) until the display changes to show both panels.) The blue region on the upper panel shows the range of angles currently being accepted by the detector. The rectangles along the bottom of the screen correspond to the function keys on the keyboard (F1 to F12) and are labelled with the commands that they perform. While the program is scanning many of these keys will be shown in gray - this means that they are not 'active' until the scan has finished.   If the system is properly set up you should only need to press the F2 key to take a scan. If you do, you will see the next screen - the scan parameter dialog: Use the TAB key to move the cursor from one blue data entry field to the next. When you have changed all the parameters that you need, hit RETURN and the scan will begin.   The important parameters for simple scans are: Scan Index: A 'serial number' used when saving the data files. You can set this to zero when you start a new run of data, or just leave it alone. Scan File: The name of the data file to save the data in. You can either enter this afresh for each scan, or use the automatically incrementing serial number. To use the serial number put the characters "%i" (no quotes) somewhere in the file name. This will be replaced by the Scan Index, which is then incremented by one after each scan. For example: if you make the scan file name S%i.DAT then data will be saved in files S1.DAT, S2.DAT, S3.DAT etc. Dump File: Leave this blank unless you know what you are doing! # Scans Set this to 1 unless you know what you are doing! Save in directory: Enter the name of the DOS directory where you want to save the files. Typically this might be something like C:\MYDATA\JULY\ The directory must exist before you try to save data: use the windows file manager to create it if necessary. Alternate: Set to 1 2Position: Set to 0 Scan Notes: Whatever text you like to put here will be saved in the data file More Notes: As above Start From: The starting 2 theta angle for the scan, typically 20° Stop At: The ending 2 theta angle for the scan, typically 70-120° Step By: The distance in 2 theta that the detector moves per step, typically 0.25° - N.B. There is a software bug in the program which causes it to lose track of the detector and/or sample positions if you use steps which are too small. Don't use anything less than 0.01°!!! Show Every: The distance in 2 theta between points in the displayed scan and in the output file, typically 0.001 - 0.1° N.B. There is an upper limit on the number of data points that can be taken in a given scan - if you try to exceed it the program will warn you before increasing the 'show every' parameter to bring the total number of points below the maximum. Count For: The time to count for at each step. DeltaT Set to 0 Format of the Data Files   The scan data files are output in a simple text-only format, an example of the first few lines of a typical scan is shown below: Scan 20.00 to 70.00 by 0.25 T 1.00 dT 0.00 Left 4.7 min First line of notes Second line of notes Angle CountTime CountRate Counts Beam Scaler1 Scaler2 14.25 0.017304492 4623.0771 8 1 0 0 14.3 0.086522459 4160.7694 36 5 0 0 14.35 0.086522459 4160.7694 36 5 0 0 14.4 0.069217968 3467.3078 24 4 0 0 14.45 0.086522459 3582.8847 31 5 0 0 14.5 0.10316139 4459.0324 46 6 0 0 14.55 0.15241264 3477.4018 53 9 0 0 ... Note that the size of the angle steps in the data file is determined by the 'Show Every:' parameter, not by the 'Step By:' parameter. Normally, all you need to worry about is the data in the first and third columns, angle vs count rate. The other columns are only important if you want to know what the counting statistics are, or if your experiment was carried out at a synchrotron source and you have measured the beam current during the scan and wish to normalise the count rates accordingly.