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Introduction

LCLS2 DAQ supports three types of scans

• epics PV scans using bluesky.

...

RIX PV Scan Script

• "on-the-fly" scans of epics PVs
• detector configuration scans

On-The-Fly Scans

These are the simplest scans to run where the DAQ is free-running and a PV is changed while taking data.  It's advantages are that it is simpler to run and sometimes quicker (since one does not pause the DAQ to move a motor, for example).  A disadvantage is that on a per-shot basis one does not know the precise value of the PV, since the PV is typically only recorded at 1Hz in epicsArch.  An example script to move a PV while the DAQ is taking data:

from epics import caget, caput, cainfo
val = 790000
delta = 7000
import time
while 1:
    val += delta
    caput('IM3K4:PPM:CAM:EVR:TRIG4:TDES',val)
    print(caget('IM3K4:PPM:CAM:EVR:TRIG4:TDES'))
    time.sleep(5)

EPICS PV Step-Scans

EPICS PV step scans use the BlueSky software from BNL (https://nsls-ii.github.io/bluesky/).  In this mode one or more PV's are modified while the DAQ is paused, then data is acquired (either for a fixed number of shots or a fixed time) then the DAQ is paused again and the PV is modified again for the next "step".  BlueSky supports complex coordinated motion of multiple PV's.

An example A python script has been created to demonstrate support for PV scans with the RIX instrument.

...

$ python bluesky_rix.py 

Transient Scan ID: 1     Time: 2020-12-10 18:24:53
Persistent Unique Scan ID: '2092a9ca-160c-4b52-8683-256f699e1e01'
New stream: 'primary'
+-----------+------------+------------+
|   seq_num |       time |     motor1 |
+-----------+------------+------------+
|         1 | 18:24:58.5 |    -10.000 |
|         2 | 18:24:59.6 |     -8.571 |
|         3 | 18:25:00.6 |     -7.143 |
|         4 | 18:25:01.6 |     -5.714 |
|         5 | 18:25:02.7 |     -4.286 |
|         6 | 18:25:03.7 |     -2.857 |
|         7 | 18:25:04.8 |     -1.429 |
|         8 | 18:25:05.8 |      0.000 |
|         9 | 18:25:06.8 |      1.429 |
|        10 | 18:25:07.9 |      2.857 |
|        11 | 18:25:08.9 |      4.286 |
|        12 | 18:25:10.0 |      5.714 |
|        13 | 18:25:11.0 |      7.143 |
|        14 | 18:25:12.0 |      8.571 |
|        15 | 18:25:13.1 |     10.000 |
+-----------+------------+------------+
generator scan ['2092a9ca'] (scan num: 1)

Preparing for a

...

PV Scan

As a general rule, one should always verify that the DAQ is running well in "normal" mode before attempting to run a scan.

...

$ python bluesky_rix.py -h
usage: bluesky_rix.py [-h] [-B PVBASE] [-p {0,1,2,3,4,5,6,7}] [-x XPM]
                      [-C COLLECT_HOST] [-t TIMEOUT] [-c READOUT_COUNT]
                      [-g GROUP_MASK] [--config ALIAS] [-v]

optional arguments:
  -h, --help            show this help message and exit
  -B PVBASE             PV base (default DAQ:NEH)
  -p {0,1,2,3,4,5,6,7}  platform (default 2)
  -x XPM                master XPM (default 0)
  -C COLLECT_HOST       collection host (default drp-neh-ctl001)
  -t TIMEOUT            timeout msec (default 10000)
  -c READOUT_COUNT      # of events to aquire at each step (default 120)
  -g GROUP_MASK         bit mask of readout groups (default 36)
  --config ALIAS        configuration alias (default BEAM)
  -v                    be verbose

Detector Configuration Scans

These scans use the same "step" idea described above for EPICS PV step-scans, but instead alter a detector configuration object on each step.  Currently this has been done for the EPIX area detector to take data in the various gain ranges.