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