spec

Software for Diffraction

3.9.1. - Scan Miscellany



resume                          # Restart an aborted scan
setscans                        # Set scan-mode options


If a scan is halted by typing the interrupt character (^C), or because of some other error such as hitting a motor limit, you can normally restart the scan by typing resume. You must not have changed the value of any of the internal scan variables in the meantime. If you use resume to continue a relative position scan, such as lup or dscan, the scanned motors will not be returned to the center point when the scan ends, as they otherwise would be.

You also have the option to control how the scan data is displayed on the screen as it is taken. An option to the setscans macro allows the motor positions and scalers contents to be displayed while they are changing during a scan. The rate of updates is set by the UPDATE global variable, just as with the umv and uct macros. An option to the setplot macro, presented earlier, allows real-time plots of the data points to be displayed as they are measured.

Another option selected in the setscans macro lets you choose whether to do prescan motor limit checks with reciprocal space scans. The purpose of these checks is to avoid running into a software motor limit in the middle of a scan. For regular motor scans, the limit checks are done only at the scan endpoints. For reciprocal space scans, the motor positions do not necessarily change monotonically and so the motor limits must be checked at each scan point. Since this checking requires a time-consuming loop at the macro level, you may choose to disable the feature if you are confident your reciprocal space scans will not send a motor outside the ranges defined by software limits.