GRETINA and the Argonne Fragment Mass Analyzer

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GRETINAand the Argonne Fragment Mass Analyzer

• Dariusz Seweryniak

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Comparison with GAMMASPHERE and FMA

• Stable heavy-ion beams up to 10MeV/A
• Higher Ge rates in GRETINA (?)
• Higher FMA efficiency
• Higher yield
• Better Doppler correction (ER,qR)
• Polarization measurements
• FMA focal plane
• GRETINAGAMASPHERE

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Physics

• rp-process nuclei
• NZ nuclei
• Proton emitters
• Trans Uranium nuclei
• n-rich radioactive beams from CARIBU

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Argonne Fragment Mass Analyzer
HPGe
GAMMASPHERE
g
PPAC
E
E
Beam
B
Q
Q
Q
Q
M/Q
Recoils
DE-E
W8msr DE/-20 D(M/Q)10 DM/M1/350
Separates beam from heavy reaction
products Disperses according to M/Q independent
of angle and energy
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FMA efficiency

• Reaction 58Ni58Ni at 250 MeV
• En2 MeV, Ep8.7 MeV, Ea16.3 MeV
• Target-FMA distance 30 cm
• 3p emission 85, 1a emission 30
• Requires placing detectors at backward angles
• Target-FMA with GS 90 cm
• 1a emission 3

Factor of 10 gain (depends on kinematics)
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GRETINA rates
40 kHz per crystal is equivalent to GS We can
provide a very selective (infrequent) trigger!
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Focal plane detection systems

• PPAC/channel plate - X, Y, TOF, DE
• Fast detectors (sub ns)
• Ionization chamber DE, E, Z
• Pulse shape
• Large area Si detector E, TOF
• DSSD ER, TOF, Ep, Ea, Ee, T1/2
• RDT
• Currently 480 channels (only 160 with
  digitizers, more?)
• 20 keV to 200 MeV
• Fast activities with digitizers
• Ge detectors isomers, b-delayed g rays, p-g,
  a-g
• 511-511 suppression
• Isomer tagging
• PiN diodes conversion electrons
• Scintillators - betas

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Electronics issues

• External Trigger
• CP/PPAC 0-2ms after g rays
• Isomers 0-100ms
• Fast decays 0-100ms
• Needs to be combined with g-fold (flexible)
• Legacy ADC read out
• CAMAC (FERA bus)
• VME
• Digitizers?
• LBNL
• XIA
• Other

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Mechanical interface

• Short distance between GRETINA and FMA
• implies(?) placing detectors at backward angles
• Focal plane studies and isomer studies require
  close geometry to increase efficiency
• Several frames?

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Discussion points

• GRETINA maximum rates
• ADC readout
• Digitizers
• External Trigger
• Detector configurations