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Several high quality electronic units were previously acquired on an individual basis from various manufacturers. As the second research effort in a planned complementary series of papers, the capability of the total array of equipment to accomplish reliable measurements of nuclear radiation was established.To evaluate the performance of the electronic units when assembled into a working coincidence system with associated test and analysis units, positron emitter, was employed with a copper converter as the source of annihilation gamma rays. The annihilation pair gamma-ray energies was precisely 0.511 MeV and the rays were emitted in opposite directions simultaneously. With a range of results that must be attained known, the equipment was arranged, meticulously calibrated and many coincidence counts completed under widely varied conditions. Resolving time and angular resolution were used as the standards for evaluation of the equipment capability. The resolving time was 29.5 nanoseconds while the angular resolution was 14 degrees. These values indicate a very good capability to proceed with many varieties of nuclear radiation research.

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Les sursauts gamma sont des sources astrophysiques parmi les plus brillantes du ciel. Dans le modèle standard actuel, leur émission prompte (X et gamma) est due à des particules chargées accélérées au sein de jets relativistes émis à la formation de trous noirs de masses stellaire. L'émission rémanente observée de la radio aux X serait due à l'interaction de ces jets avec le milieu interstellaire. Le LAT, détecteur à création de paire du télescope spatial Fermi, permet depuis juin 2008 l'étude du ciel gamma de 20 MeV à plus de 300 GeV avec des performances inégalées. Le GBM, détecteur de sources transitoires de Fermi (8 keV à 40 MeV) a observé ~450 sursauts gamma, dont ~18 ont été observés jusqu'au domaine du GeV. Une localisation précise de ces sursauts et la synergie de Fermi avec les autres observatoires permettent l'étude des rémanences associées et une meilleure interprétation des observations. L'étude de sursauts gamma de 8 keV au domaine du GeV est présentée. Les localisations obtenues avec le LAT sont étudiées ainsi que leurs erreurs. Des analyses spectrales des émissions promptes combinant les données du GBM et du LAT sont exposées, ainsi que leur interprétation. Une analyse alternative basée sur une sélection relâchée des données LAT est présentée et caractérisée. L'utilisation des événements d'énergies inférieures à 100 MeV améliore l'analyse temporelle et spectrale des émissions promptes. La recherche d'émission gamma prolongée est présentée, ainsi que l'étude de l'émission rémanente de GRB 090510 observé des UV au GeV par Fermi et Swift. Enfin, un modèle d'émission prompte par les chocs internes, développé à l'IAP, est comparé aux observations de Fermi. / Gamma-Ray Bursts (GRB) are among the brightest gamma-ray sources in the sky. The current standard framework associates their prompt gamma-ray emission to charged particles accelerated in relativistic jets issued by newly-formed stellar-mass black holes. The radio to X-ray afterglow emission is due to the interaction between these jets and the interstellar medium.The LAT, pair-creation instrument onboard Fermi gamma-ray space telescope, performs unprecedented observation of the gamma-ray sky at energies of 20 MeV to over 300 GeV since its launch in june 2008. Fermi's transient sources detector, GBM, observed prompt emissions of ~450 GRB between 8 keV and 40 MeV. ~18 of these GRB were also studied up to GeV energies with the LAT. Accurate GRB localizations and Fermi's synergy with other observatories allows the study of GRB afterglows, and therefore a better interpretation of these observations.The analyses of GRB emissions between 8 keV to GeV energies is presented here. Localizations based on LAT data and their biases are studied. Spectral analyses of combined GBM and LAT data are shown, and their theoretical interpretations explained.An alternative analysis based on a relaxed selection of LAT data is presented and fully characterized. It allows to recover and use low-energy LAT statistics in temporal and spectral analyses of GRB prompt emission.Searches for long-lived high-energy emission from GRB are presented. The analysis of GRB 090510 afterglow emission from eV to GeV energies is described.Finally, Fermi bright GRB prompt emissions are compared to an internal shock model developed at IAP.

The purpose of this investigation was to provide a method for determining the relative intensities of all gamma rays in a particular spectrum, and thereby determine the relative transition probabilities.