The Scan Widget

Figure 7.1 displays the Scan widget.

Figure 7.1: The TkI Scan Widget

The explanation of the elements:

 Scan name: Scan names are composed of a generic part (prefix) and a combination of numbers and letters that make the name unique. The generic part of the scan name is specified by the user. It can be changed by clicking into the Scan name widget.

 Position frame

 MOT1(Alias): The scan device. The widget is clickable. If invoked, the available motors, virtual motors, etc. are displayed and the user may choose one of them.

 Move to: The scan device is moved to the position that is specified in the adjacent entry widget.

 Limits frame

 Start, Stop, Step width: The scan limits. They can be given in different ways. A selector button (StartStop) offers these modes:

• Start, stop, step width
• Start, stop, np
• Range, np
• Regions
• EXAFS
• SingleShot

Selecting a new mode may change the meaning of the entry widgets. If Regions or EXAFS are selected, the entry widgets are disabled and the Prepare regs button is enabled. Section 7.1.1 displays the widgets and exaplains their items.

 Parameter frame

 Sample time:

 Update: If set to 1, the display is updated at every stop.

 Repeats:

 Wait time: Online waits this time interval after the scan device has been moved to a new position before it calls the during-macro. This feature is intended to reduce the effect of mechanical instabilities.

 Auto return: Where the device is moved after the scan is finished. These are the options:

 No: Remain at the end position of the scan.

 Yes: Go back to the position before the scan started.

 Midpoint: Move to the midpoint (SSA result).

 CMS: Move to the CMS (SSA result).

 Peak: Move to the highest point (SSA result).

 Start: Move to the starting point of the scan.

 Scan Par.: An application dependent parameter.

 Comment: The comment line is displayed on the graphics screen and stored in the output file.

 CM: This checkbutton selects the combined move mode, see figure (7.2). The scan limits are supplied for one motor, the other motor follows. There is a factor between the two scan ranges: CM-factor. This factor can be changed in the options menu (7.8).

 2D: Selects a 2d scan, see figure (7.3). The limits of the outer loop motor can be specified in terms of start, stop and step width or as a list of positions. A file <scanName>.log is created and contains log information about the scan.

 3D: Selects a 3d scan, see figure (7.4). The limits of the outer loop motor can be specified in terms of start, stop and step width or as a list of positions. A file <scanName>.log is created and contains log information about the scan.

 List: The outer loop is specified by a list of commands. That means, before an inner loop scan is started, Online executes a command from the list. Figure 7.5 shows an example for such a list. Notice that the return string 'error' indicates a failure and interrupts the procedure. The list mode can be used with 1D and 2D scans, including CM option. A file <scanName>.log is created and contains log information about the scan.

 Start: Starts a scan.

 Stop: Stops all moves and stop the scan. Pressing the <esc> key has the same effect. The stop_function, see 6.11, is also called.

 Stop rpts: For repeated scans: make this sweep the final sweep.

Figure 7.2: CM Scans (Combined Moves Scans)

Figure 7.3: 2D Scans

Figure 7.4: 3D Scans

Figure 7.5: The Outer Loop List