1. NPDGamma: Data Acquisition System October 15th, 2010 NPDGamma Collaboration Meeting ORNL

2. Reminder of LANL SNS transition issues The asymmetry is not energy-dependent, so why do we care to preserve the time structure of the data? –LANSCE: used a 3 He polarizer, so P n =P n (λ) –RFSF: in its absence, can take data until run out of memory, then save it. But, since we flip spins, need knowledge of time. At LANSCE: each pulse was 50ms –10 ms of each pulse were made of up fast neutrons, not used for the experiment (need E n <15meV) – used to read out the ADCs. –35-40ms used for pedestals SNS: 16.67ms pulses, all the neutrons are useful –No time to read out the ADCs! –Need a different strategy for pedestal data

3. Solution Data Increment – 1 spin sequence (rather than 1 accelerator pulse) Read ADCs after each spin sequence, 11% dead time Implemented and tested with noise data ~13 hours of noise data

4. Accelerator Info: Proton Current SNS Standard: Network Broadcasts via UDP DAS group uses standard software for every beamline to read and decode UDP packets Less than ideal for NPDGamma (reading wireless packets and reintegrating them into the data stream post-production) Secret Alternative: 2 VME modules that will allow us to get whichever accelerator information we want and insert it into our data stream Modules acquired (FREE!!), working on software for VME1

5. Auxiliary Information ETC Selected, processed signals (TTL) Choppers, etc Example: #39 – regardless of beam #61 – only if there are neutrons RTDL (real time data link) Event Link “all events for a scheduled proton charge for all possible frequencies” Beam information

6. Auxiliary Information Read the appropriate register for proton current RTDL (real time data link) Event Link “all events for a scheduled proton charge for all possible frequencies” Beam information RTDL VME Module New code Saved as part of runXXXXX-1.dat event file

7. Putting it all together Several data files One from each VME crate Target Info B-field Synchronize clocks on all the computers (I’d prefer if non-detector files could also have T0-based data structure) All data files are collected at the end of each run Online Analysis: read into a data “tree” – different data types make up different branches Online Analysis Status – large chunk of code to analyze the data (read in detector arrays, reconstruct signals, form asymmetries) has been written Must integrate with the altered GUI

8. Online Analysis Tim reworked the GUI to include a command line interface Team Members: Chris Crawford * Nadia Fomin Chad Gillis SeptimiuBalascuta

9. Online Analysis - continued At the end of each run, a summary file is created with some key histograms as well as statistics Summary file is copied out from ORNL and entered into the e-log e-log is online at UTK and is accessible from anywhere. an online cumulative asymmetry is also continuously updated Progress: ssh tunnels set up, working on scripts to create entries

10. Summary 60 Hz operation – implemented Accelerator information – in progress Online analysis – a large part is in place, some integration necessary