scan_info's exp_time is the trigger PERIOD. DDG2 gates for exp_time minus a
readout time, but the Eiger was sent the full exp_time as image_time_us, so
the detector acquired 180 us past the falling edge of its own gate and
finished only 20 us before the next trigger -- that 20 us being JungfrauJoch's
internal board-readout allowance, and the entire margin available. Measured on
a scope as a 172.8 us overhang.
Four independent notions of "readout time" existed:
500 us EIGER*_READOUT_TIME_US validation floor only, no effect on anything
200 us DDG2 DEFAULT_READOUT_TIMES["ab"] sets the gate width
20 us JungfrauJoch deployment config applied internally by JFJoch
- scan parameter readout_time honoured by the Falcon, ignored by DDG2
They are now one. DDG2 derives the gap from the scan's readout_time, floored by
its configured value (scans default it to 0), and exposes effective_readout_times().
The Eiger subtracts the same number from image_time_us. The Falcon already used
the scan value, so it needs no change.
The Eiger's 500 us constant is split in two, because it was doing two jobs: a
MIN_EXP_TIME validation floor keeps today's behaviour exactly, while the new
EIGER_READOUT_TIME defaults to 2e-4 to match the delay generator. The _US suffix
on constants holding seconds is dropped in all three modules.
Both devices log the effective exposure window at on_stage, so a period/exposure
mismatch is visible in the logs rather than only on an oscilloscope.
NOTE: this shortens the delivered exposure by the readout time -- 200 us, i.e.
0.5% at 40 ms -- for scans that do not set readout_time. Users should be told
before this is deployed.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KLnmUurqcNd1FiDY5M2uZr
cSAXS BEC
cSAXS specific plugins and configs for BEC This document guides you through the procedure to spin up BEC at the beamline for a new experiment (e-account). You might want to run cSAXS copy scripts before in case you want to have the former data structure to be preserved.
Overview
- Clone cSAXS BEC repository into e-account (e.g. into ~/Data10/software/.)
- Start Epics iocs
- Start BEC, BEC server and load/modify the device config with relevant hardware
- BEC commands
Clone cSAXS BEC repository
Clone the current cSAXS BEC repository from GIT into the new e-account. Create directory
mkdir ~/Data10/software
cd ~/Data10/software
Clone repository
git clone https://gitlab.psi.ch/bec/csaxs_bec.git
Start epics iocs
You can start up the iocs while the ./setup_bec.sh script is running. Be aware though that the scripts requires you to interact with it.
DelayGenerator
Open a new tab in a terminal in comp1/comp2 or cons1 and follow the commands below:
ssh gac-x12sa@localhost
cd ~/delaygen
iocsh -7.0.6 startup.script
Be aware -7.0.6 is referring to the current epics version and might change in future (SLS 2.0). To start the epics panel (only if needed), run in a new shell
caqtdm -noMsg -macro P=delaygen:,R=DG1: srsDG645.ui
More notes on usages and cabelling of DDGs. Currently 3 generators are used:
- DDG1 for detectors (EXT Enable from SGalil stages, T0 to DDG2, AB for eiger, CD for Falcon, EF for Pilatus_2)
- DDG2 for mcs card (ext. enable from DDG1, AB to mcs card)
- DDG3 for fast shutter and mcs enable (AB short pulse to enable MCS (needed!!), CD to keep FSH open )
Eiger
Open a new tab in a terminal in comp1/comp2 or cons1 and follow the commands below:
ssh gac-x12sa@localhost
cd ~/Software/Eiger/
./launch_ioc
A live view of status and images for std_daq can be found here xbl-daq-29:5000.
Pilatus_2
First, start the cam server. Connect to the computer and follow the instructions printed after connecting:
ssh det@x12sa-pd-2 (Pilatus2)
The cam server will open, wait until you see **. Nex step, open a new tab in a terminal in comp1/comp2 or cons1 and follow the commands below:
ssh gac-x12sa@localhost
cd ~/Software/Pilatus300K/
./launch_epics
FalconX1
Open a new tab in a terminal in comp1/comp2 or cons1 (logged in as the current e-account) and follow the commands:
ssh x12sa-cons-01
cd /ioc/X12SA-PC-FALCONX1/
iocsh -7.0.6 startup.script
Be aware -7.0.6 is referring to the current epics version and might change in future (SLS 2.0)
Start BEC, BEC server and load device config
Step 1 needs to have finished for continuing with these steps. What remains now is to start the bec server. Connect to pc15543 and open a new terminal to run:
cd ~/Data10/software
source bec_venv/bin/activate
bec-server start
tmux attach -t bec
Open another teminal on pc15543 and start BEC:
cd ~/Data10/software
source bec_venv/bin/activate
bec
Note: In case there is a warning after starting BEC that it was not able to import scilog, you will have to pip install scilog in the bec_venv to be able to send printouts to scilog from the command line. Within a new terminal:
cd ~/Data10/software
source bec_venv/bin/activate
pip install scilog
Device config from csaxs-bec plugins
bec.config.update_session_with_file('/sls/X12SA/data/e20639/Data10/software/csaxs-bec/bec_plugins/configs/bec_device_config_sastt.yaml')
bec.config.save_current_session('~/Data10/software/current_config.yaml')
The second command is helpful if you adjust limits of motors, which will then be stored in the config and loaded if a reload of the configuration is needed.
BEC commands
A number of commands that are useful:
To move devices that are added in the config:
umv(dev.samx, 0) #absolute
umvr(dev.samx, 0) #relative
dev.samx.wm #print motor position and limits
dev.samx.limits = [low_limit, high_limit] # To set limits, note, same lower and higher limit, e.g. [0, 0] means no limits!!
Scans:
scans.acquire(exp_time = 0.5, frames_per_trigger=10, readout_time=3e-3) # equivalent to a loopscan 30 0.5
scans.line_scan(dev.samx, -1, 1, steps=20, exp_time=0.5, readout_time=3e-3, relative=True) # optional, add frames_per_trigger =10 for burst acquisition at each step
#Scan 2 motors in a step scan at the same time
scans.line_scan(dev.samx, -1, 1, dev.samy, -1, 1, steps=20, exp_time=0.5, readout_time =3e-3, relative=True) # step scan with 20 steps, again frames_per_trigger can be added for burst at each point
scans.sgalil_grid(start_y = , end_y = , interval_y = , start_x=, end_x=, interval_x =, exp_time=0.5, readout_time=3e-3, relative=True)