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
Theoretical quantity, for example:
Gammow Teller Strength Function B(GT)
Experimental quantity : Strength Function
In Applied Research
For the Calculations of Decay Heat
f (t )  i Ei i N i (t )
Ei
i
Decay energy of the nucleus i
(gamma, beta or both)
Decay constant of the nucleus i
N i Number of nuclei i at the cooling
time t
E. Nácher et al. PRL 92 (2004) 232501
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
The problem of measuring the b- feeding
using high resolution g-ray measurement
b+
b+
ZAN
ZAN
g2
g1
Z-1AN+1
Apparent situation
Real situation
g1
Z-1AN+1
• We use Ge detector to construct the level scheme
populated in the decay
• From the g intensity balance we deduce the b-feeding
• What happens if we miss some gamma intensity???
Experimental difficulties:
Pandemonium Effect
Real
Feeding
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:
Apparent
Feeding
• 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
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
Beta Decay of 147Tb: a good example
TAGS
HRS
QEC = 4609 keV
Incomplete Decay scheme.
No levels at high energy.
I. N. Izosimov et al., Physics of Atomic Nuclei, Vol. 67, No. 10, 1876 (2004)
4431 keV
Complete Decay scheme of
147Tb
Incomplete decay scheme leads to
wrong estimation of decay heat
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)
Raw Data
Raw data from a single detector (No. 13)
22Na
Background
Calibration
M1
M2
M3
Sum Spectra
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
1.173
1.332
Most of the beta
decays feeds the 2.5
MeV level
Decay scheme
of 152Eu
1530
1289
1086
25 %
17 %
22 %
1086
1289
1530
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
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
T1/2
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
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
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
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
Practical Groups and Assignments
Group-1
Po-215
Group-2
Bi-215
Group-3
Ac-215 & Fr-215
Group-4
Ra-215
Group-5
At-215 & Rn-215
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
Summary
•A modular total absorption gamma spectrometer has been
set up at VECC using 50 BaF2 detectors.
• Data were taken for 4 sources (137Cs,
using this set up.
60Co, 22Na, 152Eu)
• 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
well.
60Co
• The set up is ready to be used for “offline” measurement.