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Recent Activities on Measurement and Evaluation of Nuclear Data at VECC

Recent Activities on Measurement and Evaluation of Nuclear Data at VECC. G. Mukherjee Variable Energy Cyclotron Centre 1/AF Bidhan Nagar, Kolkata, India. A modular Setup at VECC for TAGS Measurement. Beta Decay scheme. The beta decay studies. For basic understanding of nuclear structure.

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Recent Activities on Measurement and Evaluation of Nuclear Data at VECC

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  1. Recent Activities on Measurement and Evaluation of Nuclear Data at VECC G. Mukherjee Variable Energy Cyclotron Centre 1/AF Bidhan Nagar, Kolkata, India

  2. A modular Setup at VECC for TAGS Measurement Beta Decay scheme

  3. The beta decay studies For basic understanding of nuclear structure In Applied Research For the Calculations of Decay Heat Theoretical quantity, for example: Gammow Teller Strength Function B(GT) Experimental quantity : Strength Function Decay energy of the nucleus i (gamma, beta or both) Decay constant of the nucleus i Number of nuclei i at the cooling time t E. Nácher et al. PRL 92 (2004) 232501

  4. The beta decay studies Beta Feeding can be measured by three methods. Charged particle (beta) measurement using Si(Li) detector High resolution gamma ray measurement (Intensity difference) Total Absorption Gamma ray Measurement

  5. The problem of measuring the b- feeding using high resolution g-ray measurement b+ b+ ZAN ZAN Apparent situation g2 g1 Real situation g1 Z-1AN+1 Z-1AN+1 • We use Ge detector to construct the level scheme populated in the decay • From the g intensity balance we deduce theb-feeding • What happens if we miss some gamma intensity???

  6. Experimental difficulties: Pandemonium Effect • Introduced by the work of Hardy et al (Phys. Lett 71B (1977) 307). Their study questions the possibility of building correctly a level scheme from a beta decay experiment using conventional techniques. • Several factors can contribute to this problem: • if the feeding occurs at a place where there is a high density of levels, there is a large fragmentation of the strength among different levels and there is a large number of decay paths, which makes the detection of the weak gamma rays difficult • we can have gamma rays of high energy, which are hard to detect Real Feeding Apparent Feeding

  7. Solution Since the gamma detection is the only reasonable way to solve the problem, we need a highly efficient device: A TOTAL ABSORTION SPECTROMETER g1 g2 NaI

  8. Beta Decay of 147Tb: a good example QEC = 4609 keV TAGS HRS Incomplete Decay scheme. No levels at high energy. I. N. Izosimov et al., Physics of Atomic Nuclei, Vol. 67, No. 10, 1876 (2004)

  9. 4431 keV Complete Decay scheme of 147Tb Incomplete decay scheme leads to wrong estimation of decay heat

  10. The TAGS Setup at VECC • 50 BaF2 detectors: 25 on each side • An array of 5 x 5 in each side • Dimension of each BaF2 : • 3.5 x 3.5 x 5 cm3 • Compact geometry with 4 pi coverage • Array efficiency = 86% for 662 keV (137Cs) Uniqueness of the setup Use of BaF2 detectors: Excellent timing resolution Large Granularity: Multplicity fold gate can be used to distinguish “sum Peak” from “single peak” of similar energy. The set up has been successfully tested using (sources) 137Cs (one g-ray) 22Na (three g-rays) 60Co (two g-rays) 152Eu (many g-rays)

  11. Background Raw Data Raw data from a single detector (No. 13) 22Na

  12. Calibration

  13. Sum Spectra M  1 M  2 M  3 22Na

  14. Simulation • GEANT-3 Simulation. • Exact geometry of the detection system. • Absorbing materials in the system. (Perspex etc. not included) • Resolution of the detectors. • 60Co source • Relative intensities of the gamma rays (100 for both). • Low energy Threshold (50 keV). • Multiplicity condition as per data

  15. 60Co source data 1.173 1.332 Most of the beta decays feeds the 2.5 MeV level

  16. Decay scheme of 152Eu 25 % 1530 17 % 1289 22 % 1086 1086 1289 1530

  17. T1/2 Comparison of the fission yields of the few radio-toxic fission products in the U233, U235 and Pu239 fission ORIGEN 2 code ENDF-BV data Highlighted ones are important from decay heat point of view (larger fractional decay heat values suggested by ORIGEN 2). Sadhna Mukerji et al., RPDD, BARC, Mumbai

  18. Possibilities 1.For nuclei having short half lives (~ ms - sec) “Online” Measurement using gas jet system 2.For nuclei having long half lives (~ d - y) Offline Measurement by making “source” The set up is ready to be used for “offline” measurement.

  19. Workshop on Evaluation of Nuclear Structure and Decay Data Nov. 26 – 29, 2012 at VECC, Kolkata Sponsored by Board of Research in Nuclear Science (BRNS), India Composition: Lectures and Practical sessions Assignment: A = 215 Topics: ENSDF Evaluation Methodology ENSDF Policies, NSDD Network Web, NuDat, Bibliographic Data base and XUNDL Nuclear Theory for experimentalist and evaluators Experimental techniques for gamma-ray spectroscopy Speakers: J.K. Tuli, NNDC, BNL USA  A.K. Jain, IIT Roorkee,India  Daniel Abriola, IAEA, Vienna, Austria Balraj Singh, McMaster University, Canada S.K. Basu, VECC, India P.K. Joshi, TIFR, India S.S. Ghugre, UGC-DAE-CSR-KC, Kolkata, India S. Bhattacharya, VECC, Kolkata

  20. More than 70 participants From 19 different institutions and universities in India 35 attended practical sessions 5 Groups with 7 in each for practical sessions Group Leaders: J.K. Tuli, D. Abriola, B. Singh, A.K. Jain, S.K. Basu, S.S. Dhindsa, S. Kumar, P. K. Joshi, G. Mukherjee

  21. Work plan for Practical sessions • Experimentally known nuclides of A=215 Hg-215: Z=80, N=135: only isotope ID; no T1/2 Tl-215: Z=81, N=134: only Isotope ID; no T1/2 Pb-215: Z=82, N=133: isotope ID and T1/2 Bi-215: Z=83, N=132: α, β-, IT decays Po-215: Z=84, N=131: α, β- decays At-215: Z=85, N=130: α decay Rn-215: Z=86, N=129: α decay; in-beam γ-ray Fr-215: Z=87, N=128: α decay; in-beam γ-ray Ra-215: Z=88, N=127: α decay; in-beam γ-ray Ac-215: Z=89, N=126: α decay; in-beam γ-ray Th-211: Z=90, N=125: α decay; in-beam γ-ray Pa-211: Z=91, N=124: isotope ID, T1/2 α-decay parents: A=219 nuclides. α-decay daughters: A=211 nuclides 1

  22. Practical Groups and Assignments Group-1 Po-215 Group-2 Bi-215 Group-3 Ac-215 & Fr-215 Group-5 At-215 & Rn-215 Group-4 Ra-215

  23. Status of the evaluation Bi-215: b- decay and IT decay data sets are completed. a-decay data set is being evaluated Ac-215: Completed and submitted to BS. Fr-215: Ready to be submitted to BS. At-215: Almost ready, not yet submitted. Rn-215: New HI data set has been included. Adopted data set is being evaluated. Ra-215: With BS. Po-215: With JKT. Thank You

  24. Summary • A modular total absorption gamma spectrometer has been set up at VECC using 50 BaF2 detectors. • Data were taken for 4 sources (137Cs, 60Co, 22Na, 152Eu) using this set up. • Because of the large granularity of the array, sum spectra with different multiplicity conditions were obtained. • This helps to identify the “sum” and the “single” peaks of same/similar energies. • GEANT-3 simulation reproduces the sum spectrum of 60Co well. • The set up is ready to be used for “offline” measurement.

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