AareBEC prototype

Prototype of a BEC-integrated replacement for AareDAQ, the Data Acquisition system for MX beamlines at PSI.

Running

In one terminal, run the aare_bec service prototype:

uv venv && source .venv/bin/activate
uv pip install -e .[test]
bec-server start
aare-bec-proto

In another, the client:

source .venv/bin/activate
bec --nogui
bec.config.update_session_with_file("/path/to/config.yaml")

The demo config can be found in src/aare_bec_proto/configs/mx_demo_config.yaml

Simulated MX beamline

src/aare_bec_proto/configs/mx_demo_config.yaml describes a fully simulated MX endstation. It references simulated devices, from ophyd_devices.sim and from aare_bec_proto.devices:

Device	Class	What it is
eiger	ophyd_devices.SimCamera	Area detector, software triggered
aerotech	aare_bec_proto.devices.SimAerotechStage	x/y/z (mm) + unbounded omega (deg)
gonio	aare_bec_proto.devices.SimGoniometer	Smargon head: x/y/z (mm), phi, chi
robot	aare_bec_proto.devices.SimSampleChanger	mount(puck, position) / unmount()
ring_current	ophyd_devices.sim.sim_signals.SetableSignal	Settable scalar, 400 mA by default
fast_shutter	ophyd_devices.sim.sim_signals.SetableSignal	Settable 0/1
energy	ophyd_devices.SimPositioner	5–20 keV

The package registers itself as a BEC plugin ([project.entry-points."bec"]), which is what lets the device server resolve the aare_bec_proto.devices.* classes. It therefore has to be installed in the device server's environment, and BEC only tolerates one bec plugin per environment, so it's not compatible with a beamline plugin such as pxiii_bec. We will migrate any devices to mx_bec or beamline plugins in the future as necessary.

Beamline states and actors

The signals on the simulated devices are numeric on purpose, so they can be fed straight into DeviceWithinLimitsState and then into actors such as the builtin ScanInterlockActor:

from bec_lib.bl_states import DeviceWithinLimitsStateConfig

bec.beamline_states.add(
    DeviceWithinLimitsStateConfig(name="beam_ok", device="ring_current", low_limit=300)
)
bec.beamline_states.add(
    DeviceWithinLimitsStateConfig(name="robot_idle", device="robot", high_limit=0.5)
)

# Lock the primary scan queue whenever either state is not valid
interlock = bec.builtin_actors.scan_interlock
interlock.enabled = True
interlock.add_state_to_interlock("beam_ok", "valid")
interlock.add_state_to_interlock("robot_idle", "valid")

dev.ring_current.set(0)      # -> beam_ok becomes invalid, queue is locked
dev.ring_current.set(400)    # -> lock is released
dev.robot.mount(1, 3)        # -> robot_idle is invalid for mount_time seconds

SimSampleChanger is the template for adding further MX logic: a PSIDeviceBase subclass with integer status signals, verb-named methods exposed through USER_ACCESS, and background work reported through a DeviceStatus.