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GRETA @ ReA12 separator
Chris CampbellJuly 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
Crystal Event Builder
Segment events
Crystal events
Signal Decomposition
Interaction points
Global Event Builder
Tracking
37 segmentsper detector
1-28 crystals
Global Events
Data fromAuxiliaryDetectors
Analysis & Archiving
Data fromGRETINADetectors
Specification:
Processing 20,000Gamma rays /sec
60 nodes 2 cpu / node 4 core / cpu
This is where “events” may be defined!
92Mo case: energy resolution in GT is much better at 2 MeV
FWHM inGT at 2 MeVis ~7.8 keV
Simple GS root sort 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
600 ns600 ns
GRETINA leading edge timingThis timing quality is available asprompt signal (~200 ns latency) fora trigger logic.
GRETINA ‘t0’ timing:This timing quality is available after decomposition, i.e. in thedata analysis.
Coincidence with 1.3 MeV γ rayof 60Co source
ener
gy
ener
gy
END
GRETINA experiments with fast beams at NSCL
ϴ [r
ad] i
n G
RETI
NA
energy [keV] (laboratory frame)
Doppler-reconstructed gamma-ray spectrumfor 3-6 interactions in GRETINA for 28Si
γ rays of 28Si at v/c = 0.38 inGRETINA
FWHM: 1%
• Fragmentation data collected with three 9Be targets: 47, 100, 375 mg/cm2
• Coulex of 36Ar on a 197Au target: 184 mg/cm2
MSU 25
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.
MSU 26
36Ar experiment configuration