This program with the MCA hardware via the EPICS MCA record. It requires at least version 2.X of the MCA record, which supports fields for ROI labels and calibration parameters.
The EPICS MCA record presently has device support for the Canberra AIM MCA, which is an NIM module which communicates over Ethernet. There is presently a beta version of device support for the DXP MCA from X-Ray Instrumentation Associates. This is a 4-channel CAMAC module.
This is an early release of the MCA program, and this documentation in particular is in an early draft form.
These controls allow one to turn data acquisition On and Off and to Erase the present spectrum. The Acquisition Setup allows one to set preset live time, preset real time, and/or preset counts between a starting and ending channel.
Markers and Cursor
The program has two markers, which are indicated with short red lines on the display, and one cursor, which is indicated with a longer red line.
The cursor is positioned with the left mouse button, or by typing in a new channel number or energy in the text widgets on the bottom center of the display.
The left marker is positioned with the middle mouse button, (or by pressing the left and right mouse buttons together) or by typing in a new channel number or energy in the text widgets on the bottom center of the display.
The right marker is positioned with the right mouse button, or by typing in a new channel number or energy in the text widgets on the bottom center of the display.
Statistical information on the region of the spectrum between the left and right markers is shown at the bottom of the display. This includes the total counts, background counts, net counts, total counts/second, background counts/second, and net counts/second. It also includes the centroid and and the full width at half maximum (FWHM), which are derived from fitting a Gaussian peak to the background subtracted counts between the left and right markers. Obviously, the centroid and FWHM are most meaningful if the left and right markers are positioned on either side of a single peak.
Regions of Interest (ROIs)
Regions-of-Interest (ROIs) are regions of adjacent channels in the spectrum. The ROIs highlighted in a different color and to which one can quickly move the markers and cursor. They are typically used to highlight interesting peaks.
The MCA program uses the ROI fields which are implemented in the EPICS MCA record. Each ROI in the MCA record has the following properties:
Of these properties, only the start channel, end channel and label are controlled by the IDL MCA program. The Add ROI control creates a new ROI between the left and right markers. The new ROI will be highlighted in a color different from that of the rest of the spectrum. It will be added to the ROIs in the MCA record. Note that the MCA program sorts the ROIs into ascending order of the Start Channel, so the location of other ROIs in the record may change.
The Delete ROI control deletes the ROI which is delimited by the left and right markers. If the markers are not positioned exactly on the edges of an ROI this control has no effect. Use the ROI arrow widgets to position the markers and cursors to the ROI to be deleted.
The right ROI arrow widget moves the markers and cursors to the next ROI. The statistics on the screen will then reflect the counts in this portion of the spectrum. If the next ROI is not visible because the display is zoomed up then the display will be redrawn with this ROI in the center of the screen. This control does nothing if there are no ROIs presently defined.
The left ROI arrow widget is similar to the right ROI arrow control, except that it selects the previous ROI.
The right Zoom arrow widget and left Zoom arrow widget controls expand and contract the horizontal scale by a factor of two each time they are pressed. The zoomed display is centered on the position of the cursor (the longer red line).
The right Shift arrow widget and left Shift arrow widget controls shift the horizontal scale by half a screen width each time they are pressed.
The Display Setup screen allows one to select the vertical scaling (linear,
logarithmic), vertical autoscaling (On/Off), plot line style (dotted, solid or
histogram), plot update rate, and horizontal and vertical plot limits. The
vertical plot limits are disabled if vertical autoscaling is On.
NOTE: This is not currently functional
The MCA program requires that the following environment variables be set:
|| File name to save/restore for MCA program
preferences, such as size, colors, line style,
etc. If environment variable not set then the
||Command to display the MCA help text. This is typically defined as
netscape -remote "openURL(http://cars9.uchicago.edu/software/mca.html)"
||File containing XRF line data. Used by
||Full path to directory containing the JCPDS powder diffraction data
files. Used by |
||The PATH environment variable must contain the directory that contains the files ezca.dll, EzcaScan.dll, ezcaIDL.dll, ca.dll, and com.dll (on Windows), or the equivalent .so files on Linux or Unix.|
||Full path to the file ezcaIDL.dll (Windows) or ezcaIDL.so (Linux or Unix).|
On Unix systems adding lines like the following to your .cshrc file will define these environment variables:
setenv MCA_HELP_COMMAND 'netscape -remote "openURL(cars.uchicago.edu/software/idl/mcaDisplay.html)"' setenv MCA_PREFERENCES ~/mca.preferences setenv XRF_PEAK_LIBRARY /usr/local/idl_user/epics/mca/xrf_peak_library.txt setenv JCPDS_PATH /usr/local/idl_user/epics/mca/jcpds/ setenv EZCA_IDL_SHARE /usr/local/idl_user/epics/extensions/bin/Linux/ezcaIDL.so
On Windows systems go to Control Panel/System/Environment (NT) or Control Panel/System/Advanced/Environment Variables (XP) and add definitions like the following (assuming the IDL MCA code was unpacked in C:\EPICS\IDL_MCA):
MCA_HELP_COMMAND start http://cars9.uchicago.edu/software/idl/mcaDisplay.html MCA_PREFERENCES c:\epics\idl_mca\mca.preferences XRF_PEAK_LIBRARY c:\epics\idl_mca\xrf_peak_library.txt JCPDS_PATH c:\epics\idl_mca\jcpds\ EZCA_IDL_SHARE c:\epics\idl_mca\dlls\ezcaIDL.dll PATH ...;C:\epics\idl_mca\dlls;...
The following table briefly describes all of the files used by the MCA program.
These files can all be
obtained in a
tar file. This file should be untarred in a directory in
your IDL path.
|mcaRecord.ascii||This file contains the definition of the MCA record fields. This file is needed to create
the new version of the MCA record which has fields for calibration parameters and ROI labels.
Note that there has been no change to the C code of the record.
To build the new version of the MCA record:
|atomic_number.pro||Routine to look up the atomic number of an element.|
|atomic_symbol.pro||Routine to look up the atomic symbol of an element.|
|bm3.pro||Routine to solve the third-order Birch-Murnaghan equation of state. This is used for computing the positions of diffraction peaks at high-pressure.|
|epics_mca__define.pro||Structure definitions and methods (procedures and functions) for the object
|get_font_name.pro||Routine to return the name of a font given a description of it.|
|increment_filename.pro||Routine to increment the extension of a filename, assuming the extension is numberic.|
|jcpds||Directory containing files of powder diffraction data for standard materials. Users can add new materials to this directory by copying the format of the existing files.|
|lookup_xrf_line.pro||Routine to look up the energy of an x-ray fluorescence line.|
|mca.pro||The main source file for the MCA program. This is a very simple
routine which simply creates an object of type
|mca__define.pro||Structure definitions and methods (procedures and functions) for the object
|mca_display__define.pro||Structure definitions and methods (procedures and functions) for the object
|popup_program_info.pro||Routine to create a popup widget to display information with an optional timeout.|
|read_jcpds.pro||Routine to read the data files in the
|read_spectrum.pro||Routine to read data files created by the MCA program. Not actually used
by MCA.PRO, but provided as a convenience for users. Returns two arrays,
|xrf_peak_library.txt||The database of XRF energies, used by
The following features are planned for the MCA program in the near future.