32-Ge- 76
32-Ge- 76 BNL,JAERI EVAL-AUG04 Iwamoto,Herman,Mughabghab+
DIST-MAY10 20090805
----JENDL-4.0 MATERIAL 3243
-----INCIDENT NEUTRON DATA
------ENDF-6 FORMAT
History
09-08 The original data were taken from ENDF/B-VII.0.
(n,p) and (n,a) were recalculated from partial cross
sections.
The total cross section was recalculated from partial
cross sections.
Compiled by K. Shibata (jaea).
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ENDF/B-VII Evaluation, August 2004, O. Iwamoto(BNL,JAERI),
M. Herman(BNL), S.F. Mughabghab (BNL),
P. Oblozinsky(BNL) and A.Trkov(IAEA)
This evaluation is combined result of 2 evaluations.
a) 2004 evaluation in the thermal, resolved resonance and
unresolved resonance regions by Mughabghab. The
URR upper energy range is 570.4 keV, given as neutron
scattering threshold to the 1-st excited level of Ge-76
(562.93 keV).
b) 2004 evaluation in the fast energy region by Iwamoto,
Herman, Oblozinsky and Trkov
Merging of these 2 evaluations was performed as follows:
- Capture cross sections were adopted from evaluation a) up to
the URR upper energy, from evaluation b) at higher energies.
- Total cross sections were adopted from evaluation a) up to
the URR upper energy, from evaluation b) at higher energies.
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RESONANCE ENERGY REGION, S.F. Mughabghab (BNL)
and O. Iwamoto(BNL,JAERI)
MF= 2 RESONANCE PARAMETERS
RESOLVED RESONANCES REGION (1e-5 eV - 30 keV)
Resonance parameters were from ref. [Ma68] applying multilevel
Breit-Wigner formalism.
Bound level were introduce to describe the recommended thermal
capture and scattering cross sections [Mu05].
Resonance energies and widths were modified to reproduce
measured total cross section of natural Ge [Ha80].
Calculated 2200 m/s cross sections and resonance integral
Cross Section (b) Res. Integral (b)
Capture 0.15 1.33
Elastic 8.36
UNRESOLVED RESONANCE REGION (30 keV - 570.4 keV)
Average resonance parameters were obtained from the resolved
energy region as well as systematics [Mu05]. They were adjusted
to fit the capture given in the fast enargy region
Average parameters:
S (10**4) (eV)* (meV)
s-wave 1.5 100
p-wave 2.0 120
d-wave 1.0 100
* Level spacing at the neutron separation energy of target+n
Scattering radius was adjust to fit total cross section in the
fast region
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REFERENCES
[Ma68] Maletskii et al., Soviet Atomic Energy, 24, 207 (1968)
[Mu05] S.F. Mughabghab, "Atlas of Neutron Resonances",
to be published 2005
[Ha80] J.A. Harvey, M. Hockaday, EXFOR 13770.004
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FAST ENERGY REGION, O. Iwamoto(BNL,JAERI), M. Herman(BNL),
P. Oblozinsky(BNL) and A.Trkov(IAEA)
This is entirely new evaluation for Ge-76 in the region up to
20 MeV.
EVALUATION PROCEDURES
Adopted procedures are based on careful theoretical analysis
utilizing available experimental data, including optical model
parameter search and nuclear reaction model calculations.
OM parameter search was performed to reporduce measured total
cross section for natural Ge with the code CCOM by O. Iwamoto.
Nuclear reaction model calculations were performed with the
code EMPIRE-II by M. Herman [He01, He02]. This is modularized
statistical model code that integrates into a single system a
number of important modules and features:
- Spherical OM (code SCAT2 by O. Bersillone), and deformed OM
including coupled-channels model (code ECIS03 by J. Raynal).
- Hauser-Feshbach statistical model including HRTW width
fluctuation correction.
- Qauntum-mechanical MSD TUL model (codes ORION & TRISTAN by
H.Lenske), and MSC NVWY model.
- Exciton model (code DEGAS by E. Betak). This code represents
good approximation to DSD capture model.
- Iwamoto-Harada cluster emission model (code PCROSS).
- Complete gamma-ray cascade after emission of each particle,
including realistic treatment of discrete transitions.
- Access to OM segment of the RIPL-2 library [Ri03].
- Built-in input parameter files, such as masses, level density,
discrete levels, OM parameters and gamma strength functions.
- ENDF-6 formatting (utility code EMPEND by A. Trkov), coupled
to grahpical presentation (utility code ZVView by V.Zerkin).
PARAMETERIZATION
Optical model
- SCAT2 code used for spherical OM parameterization.
- For neutrons OM by Wilmore-Hodgson was modified to reproduce
total cross section for natural Ge.
----------
U=47.76-0.228*E-0.00118*E**2
W=9.17-0.053*E
V_so=7.0
r_u=1.297-0.00076*A+4e-6*A**2-8e-9*A**3
r_w=1.269-0.00037*A+2e-6*A**2-4e-9*A**3
r_so=r_u
a_u=0.66
a_w=0.48
a_so=a_u
----------
- For protons, OM by Koning-Delaroche (RIPL-2:OMP-2405)
- For alpha particles, OM by V.Avrigeanu et al.(RIPL-2:OMP-9600)
Level densities and discrete levels
- Gilbert-Cameron level densities were used with energy dependent
a-parameter proposed by Ignatyk.
The asymptoticvalue of the a-parameter is calculated by the
systematics of Iljinov et al.
- Discrete levels were taken from RIPL-2 level file that is
based on the 1998 version of the ENSDF database.
Other parameters and tuning
- ECIS03 with DWBA option was used to account for direct
contribution to low lying 2+ and 3- discrete levels in (n,n').
Deformation parameters were taken from work of (p,p') analysis
[Ke92].
- Preequilibrium components were calculated using the following
options: Multistep direct and multistep compound models with
default parameters for neutron channel, exciton model with
angular momentum coupling (DEGAS) for proton and gamma
channels, cluster emissin model by Iwamoto and Harada (PCROSS)
for alpha channel
- Gamma-ray strength function of modified Lorentzian version 1
(MLO1) by Plujko in RIPL-2 was used.
RESULTS
MF=3 Neutron cross sections
- EMPIRE calculations were adopted (statistical model, including
multistep/preequilibrium decay and direct processes).
MT=1 Total
- Spherical optical model was adopted.
MT=2 Elastic scattering
- Calculated as (total - sum of partial cross sections).
MT=4, 51-91 Inelastic scattering
- EMPIRE calculations were adopted (statistical model with
multistep direct & multistep compound component, and DWBA
component for low-lying levels).
MT=102 Capture
- EMPIRE calculations were adopted (statistical model with
exciton preequilibrium component as approximation to
direct-semidirect capture with fast neutrons).
MT=16 (n,2n) taken from EMPIRE calculations
MT=17 (n,3n) taken from EMPIRE calculations
MT=22 (n,n'a) taken from EMPIRE calculations
MT=24 (n,2n'a) taken from EMPIRE calculations
MT=28 (n,n'p) taken from EMPIRE calculations
MT=45 (n,n'pa) taken from EMPIRE calculations
MT=103,
600-649 (n,p) taken from EMPIRE calculations
MT=107,
800-849 (n,a) taken from EMPIRE calculations
MT=112 (n,pa) taken from EMPIRE calculations
MF=4 Angular distributions of secondary neutrons
- EMPIRE calculations (including SCAT2 results for elastic
scattering) were adopted.
MF=6 Energy-angle distributions of reaction products
- EMPIRE calculations were adopted.
MF=12 Transition probablility arrays for photon production
- RIPL-2 level data
MF=14 Photon angular distributions
- Isotropic distributions were assumed.
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REFERENCES
[He01] M. Herman "EMPIRE-II Statistical Model Code for Nuclear
Reaction Calculations", in Nuclear Reaction Data and Nuclear
Reactors, eds. N.Paver, M. Herman and A.Gandini, ICTP
Lecture Notes 5 (ICTP Trieste, 2001) pp.137-230.
[He02] M.Herman, R.Capote, P.Oblozinsky, A.Trkov and V.Zerkin,
"Recent Development and Validation of the Nuclear Reaction
Code EMPIRE", in Proc. Inter. Conf. on Nuclear Data for
Science and Technology, October 7-12, 2001, Tsukuba, Japan,
to be published in J.Nucl.Sci.Tech. (2002).
[Ke92] M.A.Kennedy, P.D.Cottle, K.W.Kemper, Phys. Rev. C46 1811
(1992).
[Ri03] "RIPL-2: Reference Input Parameter Library",
to be published, see also "http://www-nds.iaea.org/RIPL-2/".
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