1. Event Mode Data Acquisition System Richard Riedel, Oak Ridge National Laboratory

2. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Event Mode In a Nutshell  Every neutron detected is time stamped and saved without histogramming.  Other variables are also time stamped producing a movie like data set at run end.

3. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Why Event Mode?  This what detectors do (where and when a neutron is detected)  “Electronic time-focusing of pulsed-source neutron chopper data: binning to minimize effects of proton pulse and chopper opening time variations” JM Carpenter NIM vol 429 2001  Pulse Probe Techniques  Cross-Correlation Techniques. (Corelli, which measures single crystal diffuse scattering using cross correlation to provide elastic discrimination)  Offers novel approaches to typical data acquisition problems

4. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Histogram Original Space nor Time resolution necessarily preserved… histogramming is a destroyer of information

5. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Also Need Hardware Gating from preamp or shaper gate control Histogram neutrons only when temperature is within some range of setpoint

6. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Event Based System Requirements  No hardware histogramming.  Ability to timestamp detected neutrons.  Log with time/date stamp ancillary variables (i.e. temp, magnetic fields etc.).

7. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Event Mode Paradigms  Gating is done at the reduction/analysis level not in the DAS hardware.  Histogramming is done at the reduction/analysis and can be modified as needed without affecting the underlying data. scattering data temperature logs gated data software with sort criteria data from file stream or live stream

8. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY d  /sin  Pixel ID tof sine lookup Event Increment this bin Software: a few multiplies, additions and if statements  Variables can be calculated without histogramming first.  Its easier to throw data out then to look at data that was never collected. Could put a software gate here.

9. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Event Mode Data Format Time Stamp [31:0]Uncorrected time of flight Position Index [31:0]Pixel ID of detected neutron Standard neutron event data generated by all detector electronics at the SNS Pulse ID [63:0]Pulse ID from accelerator Zero Based Starting Index [63:0]Index of starting neutron event structure that was produced with the above pulse ID Standard pointer array which associates a pulse ID with a set of event data. Array of event structure + Array of pulse info structure

10. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY SNS Implementation Detector Electronics Detectors Common Data Format Independent of Detector System UDP Broadcast Common C++ Code (Command Handling Data transfer functions.) Class xxx Class yyy Class zzz C++ Abstraction Classes

11. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Broadcasting the Data Stream Active Client (DFS)Passive Client Preprocessor Session Header Header ACK Data Packet #0 Packet #0 ACK Guaranteed Delivery To One Point Data Packet #n-1 Packet #n-1 ACK

12. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Transmission Benchmarks

13. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Sample Live Views From Control Computer SNAP.5M pixel Anger Camera Mag. Refl. 2D He3 Gas Detector Both instruments see same event format!

14. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Additional Listeners Can Do Real Time Independent Work

15. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Most Interesting Applications Require Additional Time Stamped Data + = Position,TOF Pulse Information Event DataChopper Phase Temperature, Stress… SNS DAS streams, event data…… Cross, AutoCorrelations, Dynamics, Phase Transitions, Kinetics and Transient Phenomenon

16. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Adding Chopper Phases/Other Variables  Requires DAS Hardware Sync signal.  Require Access To Accelerator Time Stamp Broadcast.  Requires Computer Clock to be synced with accelerator High Frequency Signals Low Frequency Signals

17. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Stress Strain Example 1000 33 1010 35 1020 31 1025 33 1000 34 1008 34 Strain Transducers Stress Strain Preprocessor Proton Pulses Strain Sample Times time Stress Waveform Sync. Pulse PulseID Broadcast Data Set=two binary files 124567980 0 124568869 4 Data Set PulseID VULCAN will have the capability to do cross correlation technique

18. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY How Time Synchronization Is Done Timing PC Control Computer Preprocessor Satellite Computers: Chopper, Sample Environment etc. Accelerator Time Stamp (60Hz) Interrupt Based Driver/Service (50usec latency) NTP only ETC Tier 0Tier 1 Tier 2 NTP NTP sets local time, UDP broadcast sends accelerator time stamp NTP to sync computer time,date clock UDP broadcast for computers that must associate additional data with accelerator time stamp (pulseid).

19. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Final File Set + Pairs of binary files Neutron data pulseid Chopper Phases pulseid X Variable pulseid not the same!

20. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY SQL Like Queries are Possible  SELECT pulses FROM run3100 WHERE temperature > 10 AND temperature < 20;  SELECT tof FROM run3100 WHERE pixelid=1101 OR pixelid=1102;  Would require a abstraction of file system. (Embryonic SQL queries available now for current values).

21. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Who Else Runs An Event DAQ? Particle Physics. Event Data ATLAS DAQ system Reduction, Data Sorting, Analysis NOMAD rates…up to 500MB/s