Gamma-Ray Energy Tracking Array GRETINA

The 11th International Conference on Nucleus-Nucleus Collisions

May 27- June1, 2012, San Antonio TX

I-Yang LeeLawrence Berkeley National Laboratory

Outline

• Principle of gamma ray tracking• Status of GRETINA• Plans of science programs• Summary

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-ray array development

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The resolving power is a measure of the ability to observe faint emissions from rare and exotic nuclear states. Tracking array was endorsed by DOE/NSF 2002 and 2007 Long Range Plans

Principle and advantages of -ray tracking

• Efficiency (50% ) Proper summing of

scattered gamma rays, no solid angle lost to suppressors

• Peak-to-background (60%) Reject Compton events

• Position resolution (1-2 mm) Position of 1st interaction

• Polarization Angular distribution of the 1st scattering

• Counting rate (50 kHz) Many segments

3D position sensitiveGe detectorshell

Resolve position and energy of interaction points

Determine scatteringsequence

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ray tracking is essential

GRETINA capabilities

• High position resolution

• High efficiency

• High P/T• High counting rate• Background rejection

Experimental conditions Large recoil velocity

– Fragmentation– Inverse reaction

Low beam intensity

High background rate Beam decay Beam impurity

Especially for radioactive beam experiments

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GRETINA

Start Construction June 2005 Start of Operation April 2011 Engineering and commissioning

runs at LBNL until March 2012 Operation at: July 2012 -2013

NSCL MSU ATLAS ANL

$20M funded by DOE NPArray to cover ¼ of 4 solid angle28 36-fold segmented Ge crystalsMechanical support structureData acquisition systemData processing software

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Collaborating Institutions• Lawrence Berkeley Laboratory

– Lead laboratory

• Argonne National Laboratory– Trigger system– Calibration and online monitoring

software– Tracking program upgrade

• Michigan State University– Detector testing

• Oak Ridge National Laboratory– Liquid nitrogen supply system– Data processing software

• Washington University– Target chamber

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GRETINA Ge detector

B-type

A-type

• 36-fold segmented crystal• 4 crystals in one module• 2 crystal shapes• Have 7 modules and 2 spare crystals

8 cm

9 cm

~ 20 º

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Electronics production

Trigger Timing & Control module (ANL)Fast trigger <350 nsecTrigger decision time <20 secTrigger conditions Multiplicity Sum energy Hit pattern

Digitizer module (LBNL)14bit, 100 MHzEnergyPole/zero correctionLeading edge timeConstant fraction timePulse shape

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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

Achieved:Processing 20,000Gamma rays /sec

63 nodes 2 cpu / node 4 core / cpu30 Tb storage

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Set up in Cave 4C

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Interaction points

Position of interaction points determined by signal decomposition

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Tracking example

Event with 17 interaction points given by decomposition. Tracking constructed 4 good gamma rays from 13 points.

/global/data1x/gretina/Cave4CApr11/Run056/Global.dat 2nd event

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Coulomb excitation

58Ni(136Xe,136Xe’)58Ni, 500 MeV, 0.6 mg/cm2

Ni detected at 4 Si detectors at 40°(3), 35.9°(1) with Corresponding Xe angles of 24.4°, 24.9°

@̶ 136Xe, v/c= 0.056E(2 → 0) = 1.3131 MeV; = 0.52 psec

@̶ 58Ni, v/c=0.091E(2 → 0) = 1.4544 MeV; = 0.94 psec

Test acquisition system with auxiliary detector.@̶ Trigger system, clock distribution/synchronization, and data merging using the BGS acquisition system.

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Coulomb excitation setup

Demetrios Sarantites (W.U.)

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4 Si detectors

Doppler correction

Corrected for 136Xe Corrected for 58Ni

E (MeV)

Part

icle

–

ang

le (d

eg.)

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Coulomb excitation: 58Ni(136Xe,136Xe’)58Ni

Doppler corrected spectra

58Ni 2 → 0 , 1.454 MeVFWHM = 14 keV

136Xe 2 → 0 , 1.313 MeVFWHM = 8 keV

4 → 2

4 → 2

Energy resolution → position resolution

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Position resolution

GRETINA position resolution of 2.0 – 2.5 mm RMS determined from gamma-ray energy resolution after Doppler correction.

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GRETINA at BGS GRETINA set up at BGS target position Experiment September 7, 2011 – March 23, 2012

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Test experiment

4+2+

6+

10+

8+

12+

14+16+

20+18+

144Sm(36Ar,2p2n) 176Pt 190 MeVTrackingGamma gates, 2+ …. 14+

GRETINA – BGS coincidence Data are acquired using separate systems Use time stamps to correlate data

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254No results

208Pb(48Ca,2n)254No, 221 MeVCrystal count rate = 25 – 40 kHzUse energy from segmentsTracking

6+ 8+

10+

12+

14+ 16+18+

Preliminary, ¼ of data analyzed, goals:@̶ Higher spin states@̶ States above 16+ isomer

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Science campaigns

ANL FMANSCL S800 July 2012 2013

Single particle properties of exotic nuclei – knock out, transfer reactions.

Collectivity – Coulomb excitation, lifetime, inelastic scattering.

24 experiments approved for a total of 3351 hours.

Structure of Nuclei in 100Sn region. Structure of superheavy nuclei. Neutron-rich nuclei – CARIBU beam, deep-inelastic reaction, and fission.

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Acknowledgements

Advisory Committee members

Con Beausang, Mike Carpenter, Partha Chowdhury, Doug Cline, Augusto Macchiavelli, David Radford (Chair),

Mark Riley, Demetrios Sarantites, Dirk Weisshaar,

Working Groups and chairs• Physics M. A. Riley   • Detector A. O. Macchiavelli• Electronics D. C. Radford• Software M. Cromaz • Auxiliary Detectors D.G. Sarantites

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Work force Sergio Zimmermann, John Anderson, Thorsten Stezeberger,Augusto Macchiavelli, Stefanos Paschalis, Chris Campbell,

Heathre crawford, Carl Lionberger, Mario Cromaz, Torben Lauritsen,Steve Virostek, Tim Loew, Dirk Weisshaar, David Radford

Summary

• GRETINA is completed, engineering runs and commissioning runs were carried out.

• A number improvements and optimizations were implemented successfully.

• Exciting period of physics campaigns schedule through 2013 at MSU and ANL.

• GRETINA/GRETA will be a major instrument for the next generation of facility such as FRIB.

• Gamma-ray tracking arrays will have large impact on a wide area of nuclear physics.

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