1. Gamma-Ray Energy Tracking Array GRETINA The 11 th International Conference on Nucleus-Nucleus Collisions May 27- June1, 2012, San Antonio TX I-Yang Lee Lawrence Berkeley National Laboratory

2. Outline Principle of gamma ray tracking Status of GRETINA Plans of science programs Summary May 28, 2012NN20122

3.  -ray array development May 28, 2012NN20123  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

4. 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 1 st interaction Polarization Angular distribution of the 1 st scattering Counting rate (50 kHz) Many segments 3D position sensitive Ge detector shell Resolve position and energy of interaction points Determine scattering sequence May 28, 2012NN20124

5.  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 May 28, 2012NN20125

6. 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 NP Array to cover ¼ of 4  solid angle 28 36-fold segmented Ge crystals Mechanical support structure Data acquisition system Data processing software 6May 28, 2012NN2012

7. 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 May 28, 2012NN20127

8. 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 May 28, 2012NN20128

9. Electronics production Trigger Timing & Control module (ANL) Fast trigger <350 nsec Trigger decision time <20  sec Trigger conditions Multiplicity Sum energy Hit pattern Digitizer module (LBNL) 14bit, 100 MHz Energy Pole/zero correction Leading edge time Constant fraction time Pulse shape May 28, 2012NN20129

10. 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 Achieved: Processing 20,000 Gamma rays /sec 63 nodes 2 cpu / node 4 core / cpu 30 Tb storage May 28, 2012NN201210

11. Set up in Cave 4C May 28, 2012NN201211

12. Interaction points Position of interaction points determined by signal decomposition May 28, 2012NN201212

13. 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 2 nd event May 28, 2012NN201213

14. Coulomb excitation  58 Ni( 136 Xe, 136 Xe’) 58 Ni, 500 MeV, 0.6 mg/cm 2  Ni detected at 4 Si detectors at 40°(3), 35.9°(1) with Corresponding Xe angles of 24.4°, 24.9° ̶ 136 Xe, v/c= 0.056 E  (2 → 0) = 1.3131 MeV;  = 0.52 psec ̶ 58 Ni, v/c=0.091 E  (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. May 28, 2012NN201214

15. Coulomb excitation setup Demetrios Sarantites (W.U.) May 28, 2012NN201215 4 Si detectors

16. Doppler correction Corrected for 136 XeCorrected for 58 Ni E  (MeV) Particle –  angle (deg.) May 28, 2012NN201216 Coulomb excitation: 58 Ni( 136 Xe, 136 Xe’) 58 Ni

17. Doppler corrected spectra 58 Ni 2 → 0, 1.454 MeV FWHM = 14 keV 136 Xe 2 → 0, 1.313 MeV FWHM = 8 keV 4 → 2  Energy resolution → position resolution May 28, 2012NN201217

18. Position resolution  GRETINA position resolution of 2.0 – 2.5 mm RMS determined from gamma-ray energy resolution after Doppler correction. May 28, 2012NN201218

19. GRETINA at BGS  GRETINA set up at BGS target position  Experiment September 7, 2011 – March 23, 2012 May 28, 2012NN201219

20. Test experiment 4+4+ 2+2+ 6+6+ 10 + 8+8+ 12 + 14 + 16 + 20 + 18 + 144 Sm( 36 Ar,2p2n) 176 Pt 190 MeV Tracking Gamma gates, 2 + …. 14 +  GRETINA – BGS coincidence  Data are acquired using separate systems  Use time stamps to correlate data May 28, 2012NN201220

21. 254 No results 208 Pb( 48 Ca,2n) 254 No, 221 MeV Crystal count rate = 25 – 40 kHz Use energy from segments Tracking 6+6+ 8+8+ 10 + 12 + 14 + 16 + 18 +  Preliminary, ¼ of data analyzed, goals: ̶ Higher spin states ̶ States above 16 + isomer May 28, 2012NN201221

22. Science campaigns ANL FMANSCL S800 July 20122013  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 100 Sn region.  Structure of superheavy nuclei.  Neutron-rich nuclei – CARIBU beam, deep-inelastic reaction, and fission. May 28, 2012NN201222

23. 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 May 28, 2012NN201223 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

24. 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. May 28, 2012NN201224