The Widget

Figure 9.1 shows the Sweep menu.

Figure 9.1: The Sweep Widget

Here is the explanation of the items:

 Scan name: A button that displays the current scan name. The generic part can be changed by click this button. The scan name is actually the name of the directory that stores the MCA files.

In addition, Files.lis contains the motor positions and the corresponding MCA file names and also the counter values. A temporary version of the file, Files_temp.lis is maintained. It can be used by an analysis program.

 Sample time: For non-sweep measurements this is just the gate time for the MCAs and the counters at some fixed position. For sweep-mode operation the sample time is an input for the calculation of the slew rate that is used during the sweeps. Another input is the number of intervals.

 Inner loop motor: This frame allows the user to specify the details for the sweeps. A motor can be selected by a click on the button, the limits of the sweeps can be supplied and the size of the interval.

 Middle, outer loop motor: Used for defining 2D or 3D scans. These motors are not used in the sweep mode.

 Comment: The comment is stored in the MCA files.

 Statistics: This frame is of importance for sweep-mode measurements only. It is filled after the scan parameters are supplied and the Test button is pressed.

 St+Ovrhd: The total sample time of a sweep including the IOT and some extra time.

 Move: The time it takes for the motor to move over the sweep range with the default slew rate.

 Back: The time it takes for the motor to move back, including backlash.

 Slew: The default slew rate.

 Slew sweep: The adjusted slew rate that takes the sample time, the number of intervals and the overhead time into account.

 NP extra: The user may add some extra intervals to the sweep. Use Options->Configure to specify this value. The extra points have been introduced to make sure that all sweeps have the same number of points. As a consequence the last MCA spectra of a sweep may be measured at the same position.

 NP inner: The number of intervals of the sweep.

 NP middle: The number of points of the 'middle' loop.

 NP outer: The number of points of the 'outer' loop.

 Swp+back: Sweep time plus time to move back.

 Total: 'Swp+back' times the number of sweeps.

 Elapsed: Elapsed time of the scan. This includes the time that is used for the movements.

 St total: The total sample time. It is updated at the and of each sweep.

 Sweep total: The total time which was spent in the inner loop. It is updated at the end of each sweep.

 Coverage: The ratio of 'St total'/'Sweep total'. For sweep mode measurements this ratio should be near 100% whixch would mean that the MCAs were active during all the time the sweep motor was moving. The ration is updated at the end of each sweep. Time that is used for middle and outer loop movements has no effect on the coverage.

In case of non-sweep mode scans the ratio can be smaller. This is because the MCAs are only active when the motors stand still. The time that is used for motor movements reduces the ratio.

 IOT: The user supplied value of the IOT (I/O time).

 IOTCurr: The current value of the IOT.

 IOTMean: The mean value of the IOT.

 Sweep: This checkbutton enables/disables the sweep mode.

 Move: Every motor has an entry field to specify a new position. Pressing this button starts the move.

 Start: Starts the measurement.

 Stop: Interrupts the measurement.

 Test: Fills the 'Statistics' frame.

 Exit: Destroys the widget.

The problem for setting up a sweep is to determine the IOT. This can be done with the ConfigureXIA widget from the Options menu. The IOT can be measured, as a first guess, and then it is monitored during a test sweep, then set by the user. If IOT is too low, dp is constantly inceasing and the motion terminates too early. If IOT is too high, there is a feedback for every point and the motion terminates too late. A typical value is 0.02s.