Recent Activities on Recent Activities on Measurement and Measurement and

Evaluation of Nuclear Evaluation of Nuclear Data at VECCData at VECC

G. MukherjeeG. Mukherjee

Variable Energy Cyclotron CentreVariable Energy Cyclotron Centre

1/AF Bidhan Nagar, Kolkata, India1/AF Bidhan Nagar, Kolkata, India

A modular Setup at VECC for TAGS A modular Setup at VECC for TAGS MeasurementMeasurement

Beta Decay scheme

The beta decay studies

For basic understanding of nuclear structure

Theoretical quantity, for example: Gammow Teller Strength Function B(GT)

Experimental quantity : Strength Function

In Applied Research

For the Calculations of Decay Heat

)()(

i

i

i

i iii

N

E

tNEtf

Decay energy of the nucleus i (gamma, beta or both)

Number of nuclei i at the cooling time t

Decay constant of the nucleus i

E. Nácher et al. PRL 92 (2004) 232501

Beta Feeding can be measured by three methods.

The beta decay studies

Charged particle (beta) measurement using Si(Li) detector

High resolution gamma ray measurement (Intensity difference)

Total Absorption Gamma ray Measurement

The problem of measuring the - feeding using high resolution -ray measurement

ZAN

• We use Ge detector to construct the level scheme populated in the decay• From the intensity balance we deduce the -feeding • What happens if we miss some gamma intensity???

ZAN

Z-1AN+1 Z-1AN+1

Apparent situation

Real situation

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

Solution

Since the gamma detection is the only reasonable way to solve the problem, we need a highly efficient device: A TOTAL ABSORTION SPECTROMETER

1

2

NaI

TAGSHRS

Incomplete Decay scheme. No levels at high energy.

I. N. Izosimov et al., Physics of Atomic Nuclei, Vol. 67, No. 10, 1876 (2004)

Beta Decay of 147Tb: a good example

QEC = 4609 keV

Complete Decay scheme of 147Tb

Incomplete decay scheme leads to wrong estimation of decay heat

4431 keV

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)

The set up has been successfully tested using (sources)

137Cs (one -ray) 22Na (three -rays) 60Co (two -rays) 152Eu (many -rays)

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.

Raw DataRaw data from a single detector (No. 13)

22NaBackground

Calibration

Sum SpectraM 1 M 2 M 3

22Na

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

60Co source data

1.1731.332

Most of the beta decays feeds the 2.5 MeV level

Decay scheme of

152Eu

1530 25 %

128917 %

108622 %

10861289

1530

Comparison of the fission yields of the few radio-toxic fission products in the U233, U235 and Pu239 fission

Nuclide U-233 Pu-239 U-235

Sn-126

1.63E-01 1.10E-01 1.88E-02 2.3 105 y

Sb-126M

7.76E-03 3.02E-03 3.71E-04 19.2 m

Sb-126

7.75E-03 3.03E-03 8.54E-04 12.4 d

I-129

2.16E-03 1.91E-04 4.32E-05 1.6 107 y

Sn-121

2.71E-05 8.18E-05 6.64E-06 27.0 h

Sm-151

8.37E-05 2.54E-05 3.89E-06 90 y

Eu-152

2.03E-07 4.76E-08 3.29E-09 13.5 y

Eu-153

6.15E-04 1.85E-06 6.55E-05 stable

Eu-154

3.75E-05 3.35E-05 1.65E-06 8.6 y

Cs-135 1.05E-02 4.17E-03 8.33E-04 2.3 106 y

Ba-137M

6.87E-03 1.50E-03 2.51E-04 2.55 m

Cd-113M

2.34E-07 1.07E-06 1.42E-08 14.1 y

Tc-99

8.63E-06 6.25E-06 1.64E-05 2.1 105 y

Nb-93M

2.73E-07 2.44E-07 9.69E-09 16.1 y

Nb-94

1.29E-05 8.56E-06 4.46E-07 2.0 104 y

Y-90

2.25E-04 1.15E-04 2.25E-04 64.1 h

Sr-90

1.66E-01 7.89E-02 2.86E-02 28.9 y

Kr-85

2.15E-02 6.94E-03 2.31E-03 3916.8 d

Zr-93

2.58E-03 1.96E-03 2.38E-04 41.6 s

Nb-93

2.73E-07 2.44E-07 9.10E-09 stable

Pr-143

1.52E-04 9.28E-06 2.79E-06 13.6 d

La-141

1.76E-01 3.90E-02 1.96E-02 3.9 h

Ce-143

9.18E-02 1.31E-02 3.06E-02 33.0 h

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

T1/2

ORIGEN 2 code

ENDF-BV data

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.

Workshop on Evaluation of Nuclear Structure and Decay Data

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

Nov. 26 – 29, 2012 at VECC, Kolkata Sponsored by Board of Research in Nuclear Science (BRNS), India

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

• 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

Work plan for Practical sessions

Group-4Ra-215

Group-5At-215 & Rn-215

Practical Groups and Assignments

Group-1Po-215 Group-2

Bi-215

Group-3Ac-215 & Fr-215

Status of the evaluation

Bi-215: - decay and IT decay data sets are completed.-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

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.