[en] Three gamma-ray experiments flown on balloons between August 1975 and August 1976 are described in detail. The successful Transatlantic balloon flight enabled a rate of < 2 x 10³ bursts year^-1 with energies > 7 x 10^-7 ergs cm^-2 to be established. This result is discussed in the light of other work. The choice of γ-ray detector for optimum sensitivity is presented. In addition various techniques for determining the arrival direction of gamma-ray bursts are compared. A new balloon borne γ-ray burst telescope is proposed. The design, testing and results of the beam calibration of a new drift chamber detector system for high energy (> 50 MeV) γ-rays are presented. A projected angular resolution of 0.8⁰ was obtained at 300 MeV. Techniques for the measurement of γ-ray energies are discussed in relation to this instrument. Finally the use of drift chambers in an integrated free flying satellite is illustrated, and the expected performance is presented. (author)

[en] Position sensitive detectors can be fabricated from long blocks of scintillator, but these require elaborate mechanical treatment. We describe the results of a Monte Carlo simulation, which predicts a simple way to fabricate bars with the desired attenuation. (orig.)

[en] A large area (6000 sq cm) actively shielded low energy gamma-ray telescope is going to be built by an Anglo-Italian collaboration. The telescope, named ZEBRA, will be capable of producing images of the X and gamma ray sky in the energy range 0.015-20 MeV with an intrinsic angular resolution of a few tenths of a degree. A prototype detector has been built in order to experimentally study the main characteristics of the detection plane. The preliminary results obtained during a balloon flight from Trapani, Sicily in July 1981 are presented

[en] The response of a Camtrac (coded-aperture-mask track-chamber) telescope to monoenergetic gamma-rays in the energy region 20 to 400 MeV has been investigated. Preliminary results indicate that a point-spread function of a few arcmin can be achieved over an acceptance cone of 25 deg. Background generated in the mask is less than 4 percent for an E to the -2nd spectrum and does not degrade the angular resolution. 15 references

[en] Apart from the requirement for a new, high angular-resolution gamma-ray telescope for the more precise location of known COS-B gamma-ray sources, there is also a need for another instrument that can be used in a search for the gamma-ray emission from specific X-ray-emitting objects. If there is to be any hope of relating gamma ray emission to specific candidate X-ray objects, then an angular resolution of typically a few minutes of arc is required to resolve adjacent sources in crowded regions of the sky such as the galactic centre. Efforts to improve the angular resolution of track-chamber telescopes are compared. For energies close to 1 MeV telescopes have either used collimators to restrict the field of view or have made use of the kinematics of the Compton scattering process to determine the direction of the incident photon. The use of coded aperture techniques in high angular resolution X-ray astronomy telescopes is reviewed. A practical telescope for astronomy at high energies described by Carter is mentioned. At low energies an imaging telescope could be constructed by making use of position-sensitive detectors initially developed for use in medical physics. Such a telescope is outlined in general terms and its benefits and uses given. (U.K.)

[en] The authors' previous Monte Carlo method is applied to the computation of the statistical distribution of the numbers of secondary electrons emitted in reflection from three alkali halides when bombarded with primary electrons in the 100eV to 1000eV energy range. Three basic types of distributions are predicted, all reducing to a single quasi-exponential type for sufficiently high primary energy. Supporting experimental evidence from single electron spectra in photo and electron multipliers is provided. (Auth.)

[en] The authors discuss their study of the low temperature preparation of transition metal sulfides. They are specifically interested in these sulfides for their use in both secondary batteries and as catalytic materials. The production of sulfide powders from the metal and sulfur can be difficult, this is particularly true for TiS₂, VS₂ and MoS₃j. In the case of TiS₂ titanium metal is quite inert to sulfur until temperatures of at least 600⁰C are obtained. Even at this temperature, probably a consequence of oxide layer formation, the reaction proceeds slowly and usually requires several days before completion. They felt that the use of a plasma assisted process could allow the less costly production of TiS₂ from H₂S at low thermal temperatures

[en] The rotation modulation collimator is an accepted instrument for use in gamma-ray astronomy. Recently an adaption of this technique has been suggested which should improve the angular resolution and sensitivity by introducing some position sensitivity into the detection plane. A prototype of this instrument, the rotation modulation collimator, has been constructed and laboratory images generated in order to assess the potention for astronomical applications. (orig.)

[en] A non-generational genetic algorithm (GA) has been developed for fuel management optimisation of Advanced Gas-Cooled Reactors, which are operated by British Energy and produce around 20% of the UK's electricity requirements. An evolutionary search is coded using the genetic operators; namely selection by tournament, two-point crossover, mutation and random assessment of population for multi-cycle loading pattern (LP) optimisation. A detailed description of the chromosomes in the genetic algorithm coded is presented. Artificial Neural Networks (ANNs) have been constructed and trained to accelerate the GA-based search during the optimisation process. The whole package, called GAOPT, is linked to the reactor analysis code PANTHER, which performs fresh fuel loading, burn-up and power shaping calculations for each reactor cycle by imposing station-specific safety and operational constraints. GAOPT has been verified by performing a number of tests, which are applied to the Hinkley Point B and Hartlepool reactors. The test results giving loading pattern (LP) scenarios obtained from single and multi-cycle optimisation calculations applied to realistic reactor states of the Hartlepool and Hinkley Point B reactors are discussed. The results have shown that the GA/ANN algorithms developed can help the fuel engineer to optimise loading patterns in an efficient and more profitable way than currently available for multi-cycle refuelling of AGRs. Research leading to parallel GAs applied to LP optimisation are outlined, which can be adapted to present day LWR fuel management problems

[en] A prototype imaging telescope of a kind that could be used in a future-γ-ray astronomy mission has been tested using a quasi-point source of 20 MeV γ radiation. The results have demonstrated the ability to reconstruct images of the source at various positions within the field of view of the telescope. The point-spread function of the telescope was improved by nearly two orders of magnitude over that of a track chamber alone through the use of a coded aperture mask. This work has demonstrated for the first time the possibility of achieving arc minute source location with future γ-ray space telescopes. This would enable point-like γ-ray sources to be located with that precision while extended objects could be mapped with a resolution of about 10 arc min. (orig.)