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Common Features

Lauching Scans

Scans can be launched in two ways:

1) direct execution

fscan(rot, 90., 0.1, 100, 0.02, scan_mode="TIME")

2) set parameters and run

fscan.pars.motor = rot
fscan.pars.start_pos = 90.
fscan.pars.step_size = 0.1
fscan.pars.npoints = 100
fscan.pars.acq_time = 0.02
fscan.pars.scan_mode = "TIME"

fscan.run()

Accessing Parameters

All parameters can be accessed through fscan.pars. All parameters except save_flag are stored as settings. save_flag always defaults to True on bliss session startup. Other parameters keep their values accross bliss restarts.

For parameters like scan_mode or gate_mode, you can retrieve supported modes using fscan.pars.scan_mode_available or fscan.pars.gate_mode_available.

Available methods on parameters:

  • fscan.pars.to_dict()/.from_dict() : get/set all parameters as a dictionnary.
  • fscan.pars.to_file()/.from_file() : load/save all parameters to a yml file.
  • fscan.pars.reset() : resets all parameters to default.

Common Parameters

The following parameters are common to all scans:

parameter default description
save_flag True save or not scan data including images
display_flag True call show() before running scans to print out a resume of scan parameters.
sync_encoder True synchronize musst encoder value with current motor position at the beginning of scan.
home_rotation False if motor used in scan is configured as rotation_motors, a homing is performed at the preparation phase of the scan. The corresponding musst encoder is synchronized just after homing.
acc_margin 0. add a margin to computed acceleration displacement. This can be used to adjust acceleration size or to overcome speed overshoot on some controllers.
sampling_time 0.5 time used for software timer loop of slow (or sampling) counters

All these parameters are stored as settings except save_flag which always default to True on bliss session startup.

Standard Methods

All scans offer the same methods :

  • validate() : validate parameters and computes internal parameters (speed, acceleration, ...).
  • show() : call validate() and display a resume of scan calculated parameters
  • prepare() : prepare the scan and all its devices
  • start() : launch the scan
  • run() : shortcut for prepare() + start()
  • chain_show() : display the acquisition chain as a tree.

Methods available to ease data checking:

  • data_names() : list all data channel names registered during last scan run.
  • list_data() : list all data channel and their size.
  • get_data(data_name) : return numpy array of asked data.

All scans have common properties:

  • pars : user parameters
  • inpars : calculated parameters after validate() call
  • scan : bliss underlying scan object
  • chain : bliss underlying chain object
  • master : fscan underlying scan master object

Scan Metadata

Scan parameters are saved as scan metadata. They can be found under the instrument/fscan_parameters entry of the scan in the HDF5 file. Users can add metadata providing a scan_info dictionnary to the run() method.

fscan.run(my_scan_info)

OR

fscan.prepare(my_scan_info)
fscan.start()

Saving/Loading complete scan state

Two methods exists to load and save full scan state. It means saving/loading of:

  • scan parameters
  • measurement group active counters

  • lima detector state:

    • image parameters (roi, binning, ...)
    • roi counters configuration
    • processing tasks configuration

On loading, the scan parameters are set, lima configuration is restored, and the saved active counters are enabled in measurement group. After loading, save can be executed by launching fscan.run().

Scan state is saved in a yml file. Location of file is specified when calling load/save functions.

fscan.save_scan_state("/data/id15/inhouse1/myexp/xrdct_conf.yml")
...
fscan.load_scan_state("/data/id15/inhouse1/myexp/xrdct_conf.yml")

Diagnostic Methods

For scans involving motors (not ftimescan-like), two specific run functions exists:

  • scope_run() : this will launch the exact motors' movement of the scan and the musst is used as a recorder all along the movement. This can be used to check motor acceleration, speed stability, ...
  • dry_run() : the scan is executed without any counters/detectors. Only the motor(s) and the musst are used. Triggers are generated on the musst. This can be used to debug musst program for instance.