Time dependent Monte Carlo calculations of the ORELA (Oak Ridge Electron Linear Accelerator) target neutron spectrum
The time dependent spectrum of neutrons in the water-moderated Oak Ridge Electron Linear Accelerator (ORELA) target has been calculated using a modified version of the MORSE multi-group Monte Carlo code with an analytic hydrogen scattering model. Distributions of effective neutron distance traversed in the target are estimated with a time and energy dependent algorithm from the leakage normal to the target face. These data are used in the resonance shaped analyses of time-of-flight cross section measurements to account for the experimental resolution function. The 20 MeV--10 eV energy range is adequately represented in the MORSE code by the 174 group VITAMIN-E cross section library with a P{sub 5} expansion. An approximate representation of the ORELA positron source facility, recently installed near the target, has been included in the calculations to determine any perturbations the positron source might create in the computed neutron distributions from the target. A series of coupled Monte Carlo calculations was performed from the target to the positron source and back to the target using a next-event estimation surface source for each step. The principal effect of the positron source was found to be an increase in the distance for the lower energy neutron spectra, producing no real change in the distributions where the ORELA source is utilized for experiments. Different configurations for the target were investigated in order to simulate the placement of a shadow bar in the neutron beam. These beam configurations included neutrons escaping from : (1) the central tantalum plates only, (2) the entire target with the tantalum plates blocked out, and (3) only a small area from the water. Comparisons of the current data with previous calculations having a less detailed model of the tantalum plates have been satisfactory. 10 refs.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 7057521
- Report Number(s):
- CONF-900970-1; ON: DE90015156; TRN: 90-025543
- Resource Relation:
- Conference: International conference on Monte Carlo methods in neutron and photon transport, Budapest (Hungary), 25-28 Sep 1990
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
43 PARTICLE ACCELERATORS
ELECTRON BEAM TARGETS
NEUTRON LEAKAGE
NEUTRON SPECTRA
MONTE CARLO METHOD
LINEAR ACCELERATORS
POSITRON SOURCES
TANTALUM
TIME DEPENDENCE
ACCELERATORS
ELEMENTS
METALS
PARTICLE SOURCES
RADIATION SOURCES
SPECTRA
TARGETS
TRANSITION ELEMENTS
651000* - Nuclear Physics
430300 - Particle Accelerators- Auxiliaries & Components