CENTRO ATOMICO BARILOCHE ARGENTINA MODELING AND MEASUREMENTS OF

CENTRO ATOMICO BARILOCHE - ARGENTINA

MODELING AND MEASUREMENTS OF NEUTRONIC PROPERTIES OF NEW CRYOGENIC NEUTRON MODERATORS J. R. Granada, F. Cantargi, S. Petriw, J. Dawidowski Centro Atómico Bariloche Comisión Nacional de Energía Atómica & CONICET ARGENTINA CENTRO ATOMICO BARILOCHE - ARGENTINA

Ny. R - SOME RESEARCH ACTIVITIES Total Cross Section Measurement and Calculation (subthermal to epithermal range) [+T] Neutron Diffraction [+T] Deep Inelastic Neutron Scattering [+T] Non Destructive Hydrogen Content Determination Scattering Kernels for Hydrogeneous Materials CENTRO ATOMICO BARILOCHE - ARGENTINA

Scattering Kernels for Hydrogeneous Materials Previous Related Experience: THE SYNTHETIC SCATTERING FUNCTION [J. R. Granada, Phys. Rev. B 31, 4167 (1985)] CENTRO ATOMICO BARILOCHE - ARGENTINA

TOTAL CROSS SECTIONS Light water and plexiglass at room temperature ANGULAR DISTRIBUTIONS Experiment performed at the Orphee reactor (λ=0. 7045 Ả)

DIFFUSION PARAMETERS Pulse decay time for a traditional “Hokkaido configuration” DIFFUSION PARAMETERS Decay constant of heavy water at room temperature J. Nucl. Mat. 139, 158 (1986)

Multiple scattering corrections to the observed spectra (MARI experiment) Phys. Rev. B 58, 706 (1998)

CENTRO ATOMICO BARILOCHE - ARGENTINA

SYNTHETIC SCATTERING KERNELS Phys. Rev. B 31, 4167 (1985) CENTRO ATOMICO BARILOCHE - ARGENTINA

CENTRO ATOMICO BARILOCHE - ARGENTINA

Cryogenic Moderators Cross sections calculated through ‘synthetic model’ compared with exp. data at different temperatures

Development of New Cold Neutron Moderators (Main objective of the ACo. M collaboration) SCATTERING KERNELS FOR ADVANCED MODERATOR MATERIALS CENTRO ATOMICO BARILOCHE - ARGENTINA

NJOY Calculations Synthetic Frequency Spectrum Combination of experimental and synthetic contributions Continuous part associated to traslational and rotational motions of the molecular system Vibrational modes (discretes) CENTRO ATOMICO BARILOCHE - ARGENTINA

NJOY • (library ENDF) • s scattering • mass • Scattering proc • SFS Gaussian approx. 100 phonons S(Q, w) [SFS] LEAPR S(Q, w) [SFS] integrals THERMR s(E) kernels [SFS] library ACE [SFS] ACER

Solid Methane: applications of the SFS concept

Solid Methane: using SFS Neutron spectra at different temps calculated with MCNP using SFS´based libraries.

Light Water Ice Cross Sections obtained from SFS

Clathrate Neutron X-sections and spectra calculated with the use of a Synth. Frequency Spectrum

Clathrate, Methane and Ice at 20 K

Cryogenic Moderators Cross sections calculated through ‘synthetic model’ compared with exp. data at different temperatures

Cryogenic Moderators Neutron spectra from moderator substances at different temperatures (calculated)

Calculated spectra of typical cryogenic moderators for the “Hokkaido Configuration”

SCATTERING KERNELS FOR ADVANCED MODERATOR MATERIALS Latest Development of New Cold Neutron Moderators CENTRO ATOMICO BARILOCHE - ARGENTINA

Neutron Scattering Kernel for Solid Methane in phase II Rolando Granada Centro Atomico Bariloche ARGENTINA CENTRO ATOMICO BARILOCHE - ARGENTINA

CENTRO ATOMICO BARILOCHE - ARGENTINA

The scattering law of a molecular system R lν(t) denotes the position of the atom v within the molecule l , can be written as the sum of inter (l l´)- and intra (l l´)- molecular contributions (also referred to as the outer and inner terms, respectively). The intermediate scattering function is CENTRO ATOMICO BARILOCHE - ARGENTINA

Carbon self Hydrogen self Interference caused by Proton spin correlations g. Г = 1 for disordered molecules = 3 for ordered molecules CENTRO ATOMICO BARILOCHE - ARGENTINA

CH 4 II Calculated components of σT(E) for CH 4 II at 4 K CENTRO ATOMICO BARILOCHE - ARGENTINA

CH 4 II Comparison of calculated σT(E) with experimental data of Grieger et al. J. Chem. Phys. 109, 3161 (1998) CENTRO ATOMICO BARILOCHE - ARGENTINA

CH 4 II Temperature dependence of σT at low energies caused by spin correlations Open circles: this work Closed circl. : Grieger exper. Lines: Ozaki calculations CENTRO ATOMICO BARILOCHE - ARGENTINA

CENTRO ATOMICO BARILOCHE - ARGENTINA

Neutron Cross Section Libraries for Aromatic Systems of interest as Cold Neutron Moderators F. Cantargi, J. R. Granada, L. A. Rodríguez Palomino, S. Petriw, M. M. Sbaffoni Centro Atomico Bariloche ARGENTINA CENTRO ATOMICO BARILOCHE - ARGENTINA

MESITYLENE • Good moderator for a cold neutron source good resistance to radiation (S. Kulikov, E. Shabalin, V. Melikhov, E. Kulagin, Proceedings of the ICANS-XVI Meeting, Neuss, Germany, 2003) high protonic density low-energy excitations (I. Natkaniec, Proceedings of the ACo. M 6 Meeting, ESS-FZ Julich, 2002) easy handling CENTRO ATOMICO BARILOCHE - ARGENTINA