Recent advances in the synthesis of diamond films led to the fabrication of new devices that enable the direct measurement of the alpha activity of a corrosive liquid source. Such devices can be directly immersed in radioactive liquid solutions for the in-situ and real time measurement of their alpha activity. We report here on the fabrication of diamond from the chemical vapour deposition (CVD) technique and its use for the monitoring of the alpha activity of a plutonium 239 radioactive source diluted in concentrated nitric acid. Tests have demonstrated the excellent reliability of the CVD diamond detectors, that would give great benefit to the monitoring of the nuclear fuel assembly re-processing, and in particular for corrosive wastes identification and treatment.

Diamond polycrystalline films have been synthesised using the Chemical Vapour Deposition (CVD) technique in order to fabricate new types of photo-detectors for the characterisation of x-ray light sources as encountered in synchrotron experiments. Since diamond exhibits a low absorption to low energy x-ray photons, these devices allow beam position monitoring with very little beam attenuation at photon energies as low as 2 keV. We present here diamond based new devices for four different applications, including (i) semitransparent beam intensity and (ii) position monitors with high position resolution (< 2 µm), (iii) beam profile monitors with 20 µm pitch resolution, and (iv) ultra-fast diamond detectors (response time < 100 ps) that enable the intensity and temporal monitoring of fast x-ray pulses. These devices can be used for in-line characterisation of synchrotron beam line experiments for permanent in-situ monitoring of beam instabilities during experiments as well as for synchrotron machine diagnostics.

Diamond is a resilient material with rather extreme electronic properties. As such it is an interesting candidate for the fabrication of high performance solid state particle detectors. However, the commercially accessible form of diamond, grown by chemical vapour deposition (CVD) methods, is polycrystalline in nature and often displays rather poor electrical characteristics. This paper considers ways in which this material may be used to form alpha particle detectors with useful performance levels. One approach adopted has been to reduce the impurity levels within the feed-stock gases that are used to grow the diamond films. This has enabled significant improvements to be achieved in the mean carrier drift distance within the films leading to alpha detectors with up to 40% collection efficiencies. An alternative approach explored is the use of planar device geometries whereby charge collection is limited to the top surface of the diamond which comprises higher quality material than the bulk of the film. This has lead to collection efficiencies of 70%, the highest yet reported for polycrystalline CVD diamond based detectors. Techniques for improving the characteristics of these devices further are discussed.

In this paper, we present the results of investigations on the use of semiconductors deposited by chemical vapour deposition (CVD) for the fabrication of neutron detectors. For this purpose, 20 μm thick hydrogenated amorphous silicon (a-Si:H) pin diodes and 100 μm thick polycrystalline diamond resistive detectors were fabricated. The detectors were coupled to a neutron-charged particle converter : a layer of either gadolinium or boron (isotope 10 enriched) deposited by evaporation. We have demonstrated the capability of such neutron detectors to operate at neutron fluxes ranging from 101 to 106 neutrons/cm2.s. The fabrication of large area detectors for neutron counting or cartography through the use of multichannel reading circuits is discussed. The advantages of these detectors include the ability to produce large area detectors at low cost, radiation hardness (∼ 4 Mrad for a-Si:H and ∼ 100 Mrad for diamond), and for diamond, operation at temperatures up to 500°C. These properties enable the use of these devices for neutron detection in harsh environments. Thermal neutron detection efficiency up to 22 % and 3 % are expected by coupling a-Si:H diodes and diamond detectors to 3 μm thick gadolinium (isotope 157) and 2 μm thick boron layers, respectively.

There is a growing interest in the deposition and processing of thin films at low temperatures to eliminate the inherent problems associated with high temperature processing. Photo enhanced processing is one of the techniques which has received considerable interest. One of the major limitations of photo processing is the lack of sufficiently intense ultra-violet (UV) sources. To date the low pressure Hg lamp has been the only available source for large area UV processing and this has limited the types and quality of films deposited.

In this paper we will outline the design of a novel, variable wavelength excimer discharge lamp which can be used for depositing thin films over large substrate areas. We shall also discuss the direct (i.e. without intermediate photosensitisation reactions) photo induced deposition of thin silicon dioxide films using SiH4 and N2O which are photo dissociated by 126nm photons generated by the excimer lamp described.