Presentation on theme: "ReA12 separator Chris Campbell July 12, 2014."— Presentation transcript:
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 -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 Crystal Event Builder Segment events Crystal events Signal Decomposition Interaction points Global Event Builder Tracking 37 segments per detector 1-28 crystals Global Events Data from Auxiliary Detectors Analysis & Archiving Data from GRETINA Detectors Specification: Processing 20,000 Gamma rays /sec 60 nodes 2 cpu / node 4 core / cpu This is where “events” may be defined!
92 Mo case: energy resolution in GT is much better at 2 MeV FWHM in GT at 2 MeV is ~7.8 keV Simple GS root sort GS sort using side channels Double gated spectra (GT not full statistics) 12 C( 84 Kr[394MeV],4n) 92 Mo v/c ~8.5% (4.7 MeV/u)
GRETINA timing 600 ns GRETINA leading edge timing This timing quality is available as prompt signal (~200 ns latency) for a trigger logic. GRETINA ‘t0’ timing: This timing quality is available after decomposition, i.e. in the data analysis. Coincidence with 1.3 MeV γ ray of 60 Co source energy
GRETINA experiments with fast beams at NSCL ϴ [rad] in GRETINA energy [keV] (laboratory frame) Doppler-reconstructed gamma-ray spectrum for 3-6 interactions in GRETINA for 28 Si γ rays of 28 Si at v/c = 0.38 in GRETINA FWHM: 1% Fragmentation data collected with three 9 Be targets: 47, 100, 375 mg/cm2 Coulex of 36 Ar on a 197 Au target: 184 mg/cm2
Closed packed configuration Source data collected with all modules in one hemisphere in a close- packed 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. MSU25