GRETA @ ReA12 separator Chris Campbell July 12, 2014 GRETINA Design • 7 modules of 4 crystals each • 6 x 6 external segmentation • Covers ≈ 1π steradian solid angle (to • • cover 4π will take 30 modules - GRETA). Modules can be placed at 58.3º (4), 90º (8), 121º (4), and 148º (5 positions) . On-line processing gives g-ray energy and position. Gretina DAQ (I) Each of the 28 crystals has: • Separate VME backplane and IOC • Slow control in EPICS • Reads & timesorts digitizer data • Passes data to compute cluster • 4 LBNL Digitizer Modules • 10 channels (9 segments + core) • 1 Flash ADC / ch, 14bit 100MHz • On-board FPGA filters • Leading Edge (trigger primitive) • Energy (trapezoid) • Pole-zero correction • Baseline Restoration • Event data includes: • Timestamp • Filter data • Waveform subset Gretina DAQ (II): Computing Data from GRETINA Detectors Segment events 37 segments per detector Crystal Event Builder Crystal events Signal Decomposition Interaction points Data from Auxiliary Detectors Global Event Builder Global Events 60 nodes 2 cpu / node 4 core / cpu Specification: Processing 20,000 Gamma rays /sec 1-28 crystals Tracking Analysis & Archiving This is where “events” may be defined! 92Mo case: energy resolution in GT is much better at 2 MeV Simple GS root sort FWHM in GT at 2 MeV is ~7.8 keV GS sort using side channels Double gated spectra (GT not full statistics) 12C(84Kr[394MeV],4n)92Mo v/c ~8.5% (4.7 MeV/u) (Find) GRETINA in S3 GRETINA timing GRETINA leading edge timing GRETINA ‘t0’ timing: This timing quality is available as prompt signal (~200 ns latency) for a trigger logic. This timing quality is available after decomposition, i.e. in the data analysis. energy energy Coincidence with 1.3 MeV γ ray of 60Co source 600 ns 600 ns END GRETINA experiments with fast beams at NSCL ϴ [rad] in GRETINA γ rays of 28Si at v/c = 0.38 in GRETINA energy [keV] (laboratory frame) • Fragmentation data collected with three 9Be targets: 47, 100, 375 mg/cm2 • Coulex of 36Ar on a 197Au target: 184 mg/cm2 Doppler-reconstructed gamma-ray spectrum for 3-6 interactions in GRETINA for 28Si FWHM: 1% Closed packed configuration • Source data collected with all modules in one hemisphere in a closepacked configuration. • More crystals are surrounded by other crystals, thus this configuration more closely approximates GRETA. • Analysis of this data will improve understanding of the geometry dependence of GRETINA performance. MSU 25 36Ar experiment configuration MSU 26