Gamma-Ray Energy Tracking Array GRETINA

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

2. Outline • Principle of gamma ray tracking • Status of GRETINA • Plans of science programs • Summary NN2012

3. g-ray array development • 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 NN2012

4. Principle and advantages of g-ray tracking 3D position sensitive Ge detector shell • 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 Resolve position and energy of interaction points Determine scattering sequence NN2012

5. g-ray tracking is essential Especially for radioactive beam experiments Experimental conditions Large recoil velocity • Fragmentation • Inverse reaction Low beam intensity High background rate • Beam decay • Beam impurity GRETINA capabilities • High position resolution • High efficiency • High P/T • High counting rate • Background rejection NN2012

6. GRETINA $20M funded by DOE NP Array to cover ¼ of 4p solid angle 28 36-fold segmented Ge crystals Mechanical support structure Data acquisition system Data processing software • 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 NN2012

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 NN2012

8. ~ 20 º 8 cm 9 cm GRETINA Ge detector • 36-fold segmented crystal • 4 crystals in one module • 2 crystal shapes • Have 7 modules and 2 spare crystals A-type B-type NN2012

9. Electronics production Digitizer module (LBNL) 14bit, 100 MHz Energy Pole/zero correction Leading edge time Constant fraction time Pulse shape Trigger Timing & Control module (ANL) Fast trigger <350 nsec Trigger decision time <20 sec Trigger conditions Multiplicity Sum energy Hit pattern NN2012

10. Computing Data from GRETINA Detectors 37 segments per detector Segment events Crystal Event Builder Crystal events Signal Decomposition Interaction points 1-28 crystals Data from Auxiliary Detectors Global Event Builder Global Events 63 nodes 2 cpu / node 4 core / cpu 30 Tb storage Tracking Achieved: Processing 20,000 Gamma rays /sec Analysis & Archiving NN2012

11. Set up in Cave 4C NN2012

12. Interaction points Position of interaction points determined by signal decomposition NN2012

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 2nd event NN2012

14. 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= 0.056 Eg(2 → 0) = 1.3131 MeV; t = 0.52 psec • 58Ni, v/c=0.091 Eg(2 → 0) = 1.4544 MeV; t = 0.94 psec • Test acquisition system with auxiliary detector. • Trigger system, clock distribution/synchronization, and data merging using the BGS acquisition system. NN2012

15. Coulomb excitation setup 4 Si detectors Demetrios Sarantites (W.U.) NN2012

16. Doppler correction Coulomb excitation: 58Ni(136Xe,136Xe’)58Ni Corrected for 136Xe Corrected for 58Ni Particle – g angle (deg.) Eg (MeV) NN2012

17. Doppler corrected spectra • Energy resolution → position resolution 58Ni 2 → 0 , 1.454 MeV FWHM = 14 keV 4 → 2 136Xe 2 → 0 , 1.313 MeV FWHM = 8 keV 4 → 2 NN2012

18. Position resolution • GRETINA position resolution of 2.0 – 2.5 mm RMS • determined from gamma-ray energy resolution • after Doppler correction. NN2012

19. GRETINA at BGS • GRETINA set up at BGS target position • Experiment September 7, 2011 – March 23, 2012 NN2012

20. Test experiment • GRETINA – BGS coincidence • Data are acquired using separate systems • Use time stamps to correlate data 2+ 4+ 6+ 144Sm(36Ar,2p2n) 176Pt 190 MeV Tracking Gamma gates, 2+ …. 14+ 8+ 10+ 12+ 14+ 16+ 18+ 20+ NN2012

21. 254No results • Preliminary, ¼ of data analyzed, goals: • Higher spin states • States above 16+ isomer 208Pb(48Ca,2n)254No, 221 MeV Crystal count rate = 25 – 40 kHz Use energy from segments Tracking 8+ 6+ 10+ 12+ 14+ 16+ 18+ NN2012

22. Science campaigns July 2012 2013 NSCL S800 ANL FMA • 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. NN2012

23. Acknowledgements 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 Working Groups and chairs • Physics M. A. Riley    • Detector A. O. Macchiavelli • Electronics D. C. Radford • Software M. Cromaz  • Auxiliary DetectorsD.G. Sarantites Advisory Committee members Con Beausang, Mike Carpenter, Partha Chowdhury, Doug Cline,Augusto Macchiavelli,David Radford (Chair), Mark Riley, Demetrios Sarantites, Dirk Weisshaar, NN2012

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. NN2012