Scan Functions¶
So far Py4Syn can handle three scan types:
- Scan
- All devices must have the same number of steps and they will step toguether. You can specify as many devices as you want, there’s no limitation with this.
- The only restriction is that the used devices must implement the IScannable interface. For more information about IScannable Interface please check
py4syn.epics.IScannable.
- Mesh
- No concern about devices number of steps. You can specify as many devices as you want.
- The only restriction is that the used device must implement the IScannable interface. For more information about IScannable Interface please check
py4syn.epics.IScannable.
- Time
- No devices, scan runs over time. User specify the counting time and delay time in seconds, both default to 1.
Handling the Data¶
At Py4Syn all the scan data is stored in a memory dictionary in order to ensure great speed. Data inside the SCAN_DATA dictionary is organized as follows:
| Index | Content |
|---|---|
| ‘points’ | Array of points, [0, 1, 2, 3...N] |
| ‘scan_object’ | Reference to the Scan object |
| devices mnemonic | For each device used in the scan an entry to store this device value across the scan is created, e.g. SCAN_DATA[‘tth’] represents the array of tth positions |
| counters mnemonic | For each counter registered an entry to store this device value across the scan is created, e.g. SCAN_DATA[‘mon’] represents the array of mon values |
| ‘scan_start’ | Timestamp of scan start |
| ‘scan_end’ | Timestamp of scan end |
| ‘scan_duration’ | Scan duration. (‘scan_end’ - ‘scan_start’) |
| Any other user data | Any value you want, but beware that this values must be created using the py4syn.utils.scan.createUserDefinedDataField() method in order to be saved in the file. |
Callbacks¶
There are 7 callbacks available:
- Pre Scan Callback
- This callback is executed at the beginning of the scan
- Pre Point Callback
- This callback is executed before the point (before motors movement, or any other device setup)
- Pre Operation Callback
- This callback is executed before the operation, before launching the counters
- Operation Callback
- This is the main callback, it’s executed while the counters are running
- Post Operation Callback
- This callback is executed after the operation, after the counters stop and before the plot and screen update
- Post Point Callback
- This callback is executed right after the operation callback and before a new movement
- Post Scan Callback
- This callback is executed at the end of the scan
If one wants to define specific callbacks it’s possible by following the recipe below:
# Creating my function that will be executed in the choosen callback
# This function needs to receive a parameter **kwargs
def myCallback(**kwargs):
scanObject = kwargs['scan']
indexArray = kwargs['idx']
positionArray = kwargs['pos']
print('Message from my callback')
# This shows how to move back to the default callback from py4syn
setPreScanCallback(defaultPreScanCallback)
# Set my function to the operation callback
setOperationCallback(mycallback)
# Run the scan with the new configurations
scan('m1', 0, 180, 10, 1)
Attention
By overwriting an existing callback you assume that you will handle all the operations that you have overwritten. Also, user is responsible by the dead-time generated by the custom callbacks.
Special variables in the Scan module¶
In the Scan module there are some GLOBAL variables that can be read and configured. To access this variables you can either use the scan module or the appropriate getter and setter methods.
| Variable | Content | Getter | Setter |
|---|---|---|---|
| SCAN_DATA | Ordered Dictionary that contains all scan related data | getScanData() | |
| SCAN_CMD | String with the last scan command executed | getScanCommand() | |
| SCAN_COMMENT | String with a comment to be added to the scan file | getScanComment() | setScanComment() |
| SCAN_PLOTTER | Scan Object to be used when plotting data | getScanPlotter() | setScanPlotter() |
| SCAN_PLOTTER_AXIS | Axis index to be used in the plotter | getScanPlotterAxis() | setScanPlotterAxis() |
| FILENAME | String that represents the filename to be used, if None stores only in memory. See setOutput for more information. | getOutput() | setOutput() |
| XFIELD | String that represents the Mnemonic of the X axis. See setX for more information. | getX() | setX() |
| YFIELD | String that represents the Mnemonic of the Y axis. See setY for more information. | getY() | setY() |
| FWHM | Double that represents the FWHM value. | getFwhm() | |
| FWHM_AT | Double that represents the FWHM position. | getFwhmAt() | |
| COM | Double that represents the COM (Center of Mass) value. | getCom() | |
| PEAK | Double that represents the Peak value. | getPeak() | |
| PEAK_AT | Double that represents the Peak position. | getPeakAt() | |
| MIN | Double that represents the Minimum value. | getMin() | |
| MIN_AT | Double that represents the Minimum value position. | getMinAt() | |
| FITTED_DATA | Array that represents the best fit values. | getFittedData() | |
| FIT_RESULT | ModelFit with fit result information. | getFitResult() | |
| FIT_SCAN | Boolean that represents if we should or not fit the scan data at end. Default is True | getFitScan() | setFitScan() |
| PRINT_SCAN | Boolean that represents if we should or not print to the terminal the scan information. Default is True | getPrintScan() | setPrintScan() |
| PLOT_GRAPH | Boolean that represents if we should or not create the real-time plot. Default is True | getPlotGraph() | setPlotGraph() |
| PRE_SCAN_CALLBACK | Function pointer for the Pre Scan Callback. Default is defaultPreScanCallback. | getPreScanCallback() | setPreScanCallback() |
| PRE_POINT_CALLBACK | Function pointer for the Pre Point Callback. Default is None. | getPrePointCallback() | setPrePointCallback() |
| PRE_OPERATION_CALLBACK | Function pointer for the Pre Operation Callback. Default is None. | getPreOperationCallback() | setPreOperationCallback() |
| OPERATION_CALLBACK | Function pointer for the Operation Callback. Default is defaultOperationCallback. | getOperationCallback() | setOperationCallback() |
| POST_OPERATION_CALLBACK | Function pointer for the Post Operation Callback. Default is None. | getPostOperationCallback() | setPostOperationCallback() |
| POST_POINT_CALLBACK | Function pointer for the Post Point Callback. Default is None. | getPostPointCallback() | setPostPointCallback() |
| POST_SCAN_CALLBACK | Function pointer for the Post Scan Callback. Default is defaultPostScanCallback | getPostScanCallback() | setPostScanCallback() |