2D detectors (with Lima)¶

2D detectors (CCD, pixel, …) supported by Lima can be controlled in BLISS via the BLISS Lima class.

This class uses the usual Lima Tango device server to access the detector.

Configuration¶

beamline_configuration/
├── eh2
│   ├── cameras
│   │   ├── andor1.yml
│   │   ├── andor2.yml
│   │   ├── cdte22.yml
│   │   ├── eiger1.yml
│   │   └── mpx22.yml

Example of YAML configuration file:

name: mpx22
class: Lima
tango_url: id42/limaccd/mpx_22
prepare_timeout: 120

Additional parameters¶

Each individual Lima sub-device can be configured directly from the YML file. The section names are the sub-devices names, item keys are the attribute names just like specified in the Tango device:

Saving example¶

saving:
    mode: ONE_FILE_PER_FRAME
    file_format: EDF
    _max_writing_tasks: 4

Processing example¶

processing:
    runlevel_roicounter: 9

Image example¶

image:
    rotation: 90

Accumulation example¶

accumulation:
    max_expo_time: 2

Optional parameters for experts¶

There are 3 extra parameters reserved for the experts !

prepare_timeout: 120
start_waittime: 0.05
disable_bpm: false

With prepare_timeout (default is 3 seconds) you can add an addition preparation time for cameras which can take longer to prepare the acquisition for instance to allocate the requested huge memory for a long scan.

With start_waittime (default is 5ms) you will add an extra waiting time before Bliss fire (trig) the camera. Than can be useful if a detector is not fully started and ready to listen for the trigger just after the call to the startAcq() .

With disable_bpm set to false (default is true) bliss will never activate the Bpm tango device. The Bpm calculation on an image takes about 100ms and this can become a critical when you want to run a camera at fast speed.

Directories mapping¶

Directories mapping allows to replace filesystem paths used by BLISS, in favour of different mappings when Lima is running under Windows for example or on a computer with different mounting points.

Paths specified in SCAN_SAVING will be transformed, in order to pass the good path arguments to Lima:

directories_mapping:
    default:
        - path: /data/visitor
          replace-with: Z:/visitor
        - path: /data/id15
          replace-with: Z:/id15

Configuring scan default chain with Lima devices¶

Default chain configuration can have an acquisition_settings section, which allows to set attributes on the main Lima Tango device at scan preparation time. The item key names correspond to the Tango device attributes.

Setting 2D detectors in external trigger mode only¶

- name: default_chain_eh2
  plugin: default
  chain_config:
    - device: $mpx22
      acquisition_settings:
        acq_trigger_mode: EXTERNAL_TRIGGER_MULTI
      master: $p201_20

Miscellaneous¶

Taking dark (background) images¶

The .take_dark() method of Lima controller objects can be used to take background images, that will be substracted to subsequent frames during acquisition, in order to reduce noise level.

.take_dark accepts the following arguments:

exposure time (in s.)
optional arguments:
- shutter, None by default
- save [bool], True by default

When save is True, current SCAN_SAVING parameters are used to save the background image, and to install it as Lima reference for background substraction. Currently background images are always saved in EDF format. A background_ prefix is added to the image prefix. If save is False, an image is taken but it only stays in memory ; Lima will use this internal image to do background substraction.

The shutter argument allows to pass a BLISS Shutter object, that will be closed while taking the background image. If the shutter was open when passed to the function, it will be re-opened at the end of the take_dark procedure.

Example to add a pseudo axis to drive the Maxipix’s threshold¶

if hasattr(setup_globals,'mpx22'):
    mpxthl = SoftAxis('mpxthl', mpx22.camera,
                       position='energy_threshold',
                       move='energy_threshold')