1. Beam-Synchronous Data Acquisition (BS-DAQ)
at SwissFEL injector facility

2. BS-DAQ, what is the problem?
Pulsed machines such as SwissFEL test injector, run at high rep rates
test injector machine is a mix of 100Hz and 10 Hz subsystems
SwissFEL machine will be at 100Hz
Data generated at separated IOCs distributed over the facility
IOCs communicate via Ethernet-based protocol
Pulse-to-pulse Data Acquisition, requires real-time behavior
non-deterministic communication (e.g. CA) cannot be tolerated
Data-to-pulse assignment (pulse marking) is essential:
allows correlated studies of the machine behavior

3. BS-DAQ, the solution
Collect the acquired data at individual IOCs: local buffering
to avoid no-deterministic cross-IOC communication
Timing system (MRF event system) plays important role:
precise, distributed triggering (when to measure/actuate)
reliable, synchronous communication for DAQ controls (62.5 MB/s)
Unique pulse ID generation/distribution by the timing system to distinguish pulse-to-pulse data
Collected data along with pulse IDs, buffered at IOCs, is retrieved by CA after DAQ completion

4. BS-DAQ Mechanism IOC EVG IOC_A IOC_B EVR EVR subsystem A subsystem B
CA (controls net)
command
Master Timing: central point of BS-DAQ controls
Client, after DAQ:
retrieve data
analyze
Events + sync data
IOC_A
IOC_B
EVR
buffer
triggers
EVR
buffer
Events help triggering at the right time but not making sure that the acquired data belong to the same pulse also real-time collection by Ethernet is a problem
2. Solve the problem by using and combining sync data feature of the event system
select
select
H/W_1
H/W_3
H/W_2
H/W_4
subsystem A
subsystem B
CA (controls net)

5. BS-DAQ terminology
PV represents an EPICS channel (data to be acquired)
IOC is an EPICS based system (Input Output Controller)
slot refers to collection of resources assigned to a user of BS-DAQ
BS-DAQ users C
slot 0 B
slot 2 A
slot 1
time
IOC_1
IOC_N
PV_2
PV_5
PV_1
PV_6
PV_3
PV_4
PV_m ….
PV_j
Buffer 1
Buffer 2
Buffer n
Buffer 1
Buffer 2
Buffer n

6. BS-DAQ Mechanism PULSE_1 PULSE_2 PULSE_3 IOC_1 PV_1 PV_2 PV_3 IOC_2
IOC_n
PV_7
PV_8
PV_9
user defined PV set for a BS-DAQ slot
PV_2
PV_6
PV_7
PV_2
PV_6
PV_7
PULSE_1
PULSE_2
PULSE_3
What user gets:
What user wants:
PV_2
PV_6
PV_7
PV_2
PV_6
PV_7
PV_2
PV_6
PV_7
PULSE_1
PULSE_2
PULSE_3
start
start
start
Pulser RF
Diag.
Pulser RF
Diag.
Pulser RF
Diag. … … …

7. BS-DAQ Low-level Config/Controls
Several users can perform simultaneous BS-DAQ in dedicated slots
Users need to lease BS-DAQ slots and must free them when finished
Slot configuration & controls (start/stop, etc.) are totally independent

8. BS-DAQ Configuration & Controls
All done by EPICS standard records and/or mechanisms:
compress record as buffering object (waveforms are handled too!)
no self-bustled C code whatever..
record scanning on Event at HIGH PRIO
No need to know PV of interest ahead of IOC init
specify which PV goes to which buffer at runtime
Each PV buffer has also a dedicated pulse ID buffer:
pulse ID buffering occurs after data is buffered on every pulse
can tell us exactly what pulses were missed in a DAQ
is a synchronized time reference (with100Hz rate)
helps quick, first-level DAQ verification
Linux-based PC systems also participate in BS-DAQ
PCI-EVR provides access to timing system
EPICS IOC runs exactly the same BS-DAQ software

9. BS-DAQ Usage Generic IOC S/W application package
is maintained and installed from a central location
does not modify existing IOC S/W only adds to it
couple of macros to be specified by IOC responsible
Low level config./controls provided through medm
Machine experts use Matlab for config./control/retrieval/analysis
automated procedure involves:
Find and Lease a free slot
Locate IOC for each PV of ineterest
Find a free buffer for each PV and assign it to the DAQ slot
Specify no. DAQs, spacing, defer cycles, etc.
Start/stop/resume/abort
Retrieve data + pulse ID buffers for each PV
Consistency checks / analysis
Free the DAQ slot

10. Thanks!