Abstract: Cross Section Library CLES

1. Name of Library
CLES: cross section library of moderator meterails for low-energy neutron sources


2. Description of Library
It consists of 36 sets of 140-group-constants(energy-averaged cross
sections) for seven different moderator materials in liquid and solid
phases at given temperatures
- Liquid 4He at 0.1, 0.3, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5 K,
- Liquid ortho-, para- and normal-H2 at 14.0, 20.4 K,
- Liquid ortho-, para- and normal-D2 at 18.7, 23.6 K,
- Solid CH4 at 20.4, 50.0, 90.7 K,
- Liquid CH4 at 90.7, 111.7 K,
- Liquid H2O at 278, 300, 325, 350 K,
- Liquid D2O at 278, 300, 325, 350 K.
All the sets are generated in the following form/1/:
- Neutron energy range between 0.1 -eV and 10 MeV,
- Total of 140 energy groups at equal logarithmic energy intervals(i.e. 10 groups
per energy decade),
- Expansion of the angular distribution of scattered neutrons in Legendre polynomials
up to order 3,
- Weighting energy spectrum by a combination of Maxwellian, 1/E and fission
spectra for neutron energy E,
- Microscopic cross sections(b/molecule) in terms of text format(2 MB/set) and
ANISN-type cross section table (length IHM=282, position IHT=3, groups
IGM=140) though not multiplied by the Legendre factor (2l + 1).


3. Method of Group Constant Generation
The high-energy part for E - 1 eV(energy group g - 70) and the low-energy part
for E - 10 eV(g - 60) are made up separately and then combined into one set.
The overlapping energy region between 1 and 10 eV is prepared to make a gradual
transition between the two parts. The high-energy part is produced using the
Japanese evaluated nuclear data library JENDL-3.3/2/ and the nuclear data processing
program NJOY/3/. The low-energy part is created by use of double-differential
scattering cross section models developed theoretically for liquid and solid moderator
materials. Low-energy neutron scattering by molecular dynamics inherent to each
material is fully taken into account and the calculated cross-section results are compared
with many experimental measurements, both double-differential and total, at
liquid and solid temperatures. Slowing-down and thermalization properties are also
examined with neutron energy spectra calculated numerically for moderator models.
All the results are reported in research papers on scientific journals, which are given
for each material by paper(s) on cross section model and spectral analysis: liquid
4He/4/5/, liquid H2/6/7/, liquid D2/8/9/, solid CH4/10/11/, liquid CH4/10/11/,
liquid H2O/12/13/, and liquid D2O/14/13/. Numerical methods for calculation of
low-energy neutron scattering cross sections are described in detail and illustrated
with physical cross section models/1/.


4. Related Program
A fortran program, CLES.trans.for, is available to produce cross section tables for
specific neutron transport calculations, both deterministic and Monte Carlo. The
major recipes are as follows:
- Listing the total cross sections of scattering and absorption, the group-togroup
transfer cross sections, and the upper- and lower-energy boundaries for
all groups,
- Multiplying microscopic scattering cross sections -s (b/molecule) by the factor
(2l + 1) to construct an ANISN-type cross section table,
- Calculating macroscopic scattering cross sections ��s = N-s (1/cm) by the
input value for number density N (molecules/cm3): although an equilibrium
or theoretical value of N for each material at given temperature is preset, it
may be necessary to give any other values in practical cases such as boiling
liquid and non-crystalline solid/7,11/,
- Varying the magnitudes of absorption cross section -a (b/molecule) according
to the expression p-a + q(vth=v) with two arbitrary constants p (as a factor)
and q (b/molecule) for neutron speeds v at E and vth at E = 25 meV/13/,
- Merging two group-constant sets in a new one for mixed materials such as,
for instance, liquid normal H2 with a para:ortho ratio of 1:3/7/, liquid normal
D2 with a para:ortho ratio of 1:2/9/ and liquid D2O contaminated with liquid
H2O/13/.


5. References
/1/N.Morishima: Numerical Methods for Calculation of Low-Energy Neutron
Scattering Cross Sections, J. Neutron Res. 13(2005) 225-240.
/2/K.Shibata et al.: Japanese Evaluated Nuclear Data Library Version 3 Revision-
3: JENDL-3.3, J. Nucl. Sci. Technol. 39(2002) 1125-1136.
/3/R.E.MacFarlane, D.W.Muir: The NJOY Nuclear Data Processing System,
Version 91, LA-12740-M, Los Alamos National Laboratory, October 1994.
/4/N.Morishima, Y.Abe: Evaluation of Cold-Neutron Scattering Cross Sections
for Liquid 4He at Temperatures between 1 and 4.2 K, Nucl. Instr. and Method-
A, 397(1997) 354-364; Y.Abe, N.Morishima: Ultracold and Cold Neutron Cross
Sections of Liquid 4He at Low Temperatures down to 0.1 K, Nucl. Instr. and
Method-A, 459(2001) 256-264; N.Morishima, M.Sakakibara: Ultracold Neutron
Production by the Phonon Excitation in Superfluid 4He at Temperatures
below 1 K, J. of Neutron Res. 8(2000) 233-243.
/5/Y.Abe, N.Morishima: Neutronic Study of UCN Production and Storage in a
Liquid 4He Source, Nucl. Instr. and Method-A, 481(2002) 414-421.
/6/N.Morishima, D.Mizobuchi: Cross Section Models for Cold Neutron Scattering
from Liquid H2 and D2, Nucl. Instr. and Method-A, 350(1994) 275-285;
N.Morishima, A.Nishimura: On the Yield of Cold and Ultracold Neutrons for
Liquid H2 at Low Temperatures near the Melting Point, Nucl. Instr. and
Method-A, 426(1999) 638-641.
/7/N.Morishima, Y.Matsuo: Cold Neutron Production in Liquid para- and normal-
H2 Moderators, Nucl. Instr. and Method-A, 490(2002) 308-315.
/8/N.Morishima: Cold and Thermal Neutron Scattering Cross Sections of Liquid
H2 and D2 at Temperatures between Melting and Boiling Points, Ann.
Nucl. Energy, 27(2000) 505-516; N.Morishima, Y.Nishikawa: Cold and Thermal
Neutron Scattering Cross Sections of Liquid H2 and D2. II: Improvement
on Coherent Scattering, Ann. Nucl. Energy, 31(2004) 737-745.
/9/Y.Matsuo, N.Morishima, Y.Nagaya: Neutronic Study of Spherical Cold Neutron
Sources composed of Liquid H2 and D2, Nucl. Instr. and Method-A,
496(2003) 446-451.
/10/N.Morishima, Y.Sakurai: Cross-Section Model for Cold Neutron Scattering
in Solid and Liquid CH4, Nucl. Instr. and Method-A, 490(2002) 527-537.
/11/N.Morishima, T.Mitsuyasu: Cold Neutron Production in Solid and Liquid
CH4 Moderators, Nucl. Instr. and Method-A, 517(2004) 295-300; T.Mitsuyasu,
N.Morishima, Y.Nagaya: Cold Neutron Production in Solid and Liquid CH4
Moderators II: on the Reentrant-Hole Configuration, Nucl. Instr. and Method-
A, 537(2005) 610-613 (2005).
/12/Y.Edura, N.Morishima: Cold and Thermal Neutron Scattering in Liquid Water:
Cross-Section Model and Dynamics of Water Molecules, Nucl. Instr. and
Method-A, 534(2004) 531-543.
/13/Y.Edura, N.Morishima: Generation of Neutron Multigroup Constants in the
Energy Range 0.1 -eV-10 MeV for Light and Heavy Water at Four Different
Temperatures, Nucl. Instr. and Method-A, 560(2006) 485-493.
/14/Y.Edura, N.Morishima: Cold and Thermal Neutron Scattering in Liquid
Water-II: Scattering Laws and Group Constants for H2O and D2O, Nucl. Instr.
and Method-A, 545(2005) 309-318.


6. Name and Establishment of Authors
N.Morishima
Department of Nuclear Engineering, Kyoto University,
Yoshida, Sakyo-ku, Kyoto 606-8501, Japan


7. Data File Available
The data file consists of 36 group-constant sets(72MB), a fortran program CLES.trans.
for(23KB) and this abstract as a CLES.abstract.pdf(61KB).


8. Subject Categories and Keywords
- V. Particle accelerator
- Z. Nuclear data
Cross Sections, Group Constant, Ultracold Neutron, Cold Neutron, Cryogenic Moderator,
Neutron Source