Gamma-ray spectrometer

Résumé

A gamma-ray spectrometer (GRS) is an instrument for measuring the distribution (or spectrum—see figure) of the intensity of gamma radiation versus the energy of each photon. The study and analysis of gamma-ray spectra for scientific and technical use is called gamma spectroscopy, and gamma-ray spectrometers are the instruments which observe and collect such data. Because the energy of each photon of EM radiation is proportional to its frequency, gamma rays have sufficient energy that they are typically observed by counting individual photons. Gamma-ray spectroscopy Atomic nuclei have an energy-level structure somewhat analogous to the energy levels of atoms, so that they may emit (or absorb) photons of particular energies, much as atoms do, but at energies that are thousands to millions of times higher than those typically studied in optical spectroscopy. (Note that the short-wavelength high-energy end, of the atomic spectroscopy energy range (few eV to few hundred keV), g

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https://en.wikipedia.org/wiki/Gamma-ray_spectrometer

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The main objective of the course is to introduce the concept of space system design and engineering. The course will describe the various subsystems involved in the design of a satellite. It will also describe the techniques of systems engineering that are used to obtain a coherent satellite design.

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Prototype of the novel CAMEA concept-A backend for neutron spectrometers

Paul Gregory Freeman, Felix Groitl, Henrik Moodysson Rønnow

2018

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Prismatic analyser concept for neutron spectrometers

Paul Gregory Freeman, Martin Mansson, Henrik Moodysson Rønnow

Developments in modern neutron spectroscopy have led to typical sample sizes decreasing from few cm to several mm in diameter samples. We demonstrate how small samples together with the right choice of analyser and detector components makes distance collimation an important concept in crystal analyser spectrometers. We further show that this opens new possibilities where neutrons with different energies are reflected by the same analyser but counted in different detectors, thus improving both energy resolution and total count rate compared to conventional spectrometers. The technique can readily be combined with advanced focussing geometries and with multiplexing instrument designs. We present a combination of simulations and data showing three different energies simultaneously reflected from one analyser. Experiments were performed on a cold triple axis instrument and on a prototype inverse geometry Time-of-flight spectrometer installed at PSI, Switzerland, and shows excellent agreement with the predictions. Typical improvements will be 2.0 times finer resolution and a factor of 1.9 in flux gain compared to a focussing Rowland geometry, or of 3.3 times finer resolution and a factor of 2.4 in flux gain compared to a single flat analyser slab. (C) 2014 AIP Publishing LLC.

American Institute of Physics2014

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Power calibration methodology at the CROCUS reactor

Pavel Frajtag, Vincent Pierre Lamirand, Axel Guy Marie Laureau, Oskari Ville Pakari, Andreas Pautz

In the present article, we detail the method used to experimentally determine the power of the CROCUS zero-power reactor, and to subsequently calibrate its ex-core monitor fission chambers. Knowledge of the reactor power is a mandatory quantity for a safe operation. Furthermore, most experimental research programs rely on absolute fission rates in design and interpretation - for instance, tally normalization of reaction rate studies in dosimetry, or normalization of power spectral density in neutron noise measurements. The minimization of associated uncertainties is only achieved by an accurate power determination method. The main experiment consists in the irradiation, and therefore, the activation of several axially distributed Au-197 foils in the central axis of the core, which activities are measured with a High-Purity Germanium (HPGe) gamma spectrometer. The effective cross sections are determined by MCNP and Serpent Monte Carlo simulations. We quantify the reaction rate of each gold foil, and derive the corresponding fission rate in the reactor. The variance weighted average over the distributed foils then provides a calibration factor for the count rates measured in the fission chambers during the irradiation. We detail the calibration process with minimization of respective uncertainties arising from each sub-step, from power control after reactivity insertion, to the calibration of the HPGe gamma spectrometer. Biases arising from different nuclear data choices are also discussed.

E D P SCIENCES2020

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