![]() Methods have been devised based on nuclear-physics constants related to the main and impurity nuclides. The measurable features and the accuracy of measuring those features along with certification procedures are discussed for fission fragment sources containing /sup 252/Cf and /sup 244/Cm. Representative systems utilizing gridded Fisch ionization chambers, surface barrier silicon diodes, or thin film plastic scintillators have been identified and evaluated as being suitable for this application. The kinetic energy and mass of fission fragments can readily by determined by the E - dE/dX measurement technique. By measuring SEU in coincidence with the kinetic energy and the mass, or just the kinetic energy, of the more » oppositely emitted fission fragment, /sup 252/Cf can be used to provide an accurate determination of both the mass of the fragment and its LET as it penetrates the DUT. This paper presents a new approach, which utilizes the properties of the californium fission process to significantly reduce the uncertainties inherent in current testing systems. Testing with /sup 252/Cf spontaneous fission fragments is far less expensive and more readily accessible than accelerator testing, but uncertainties associated with currently used averages over the fragment distribution severely limit the validity of californium testing. « lessĬonsiderable effort is now being expended at accelerators to test microelectronics for single event upset (SEU) from energetic heavy ions. A review of experimental data on these two quantities is provided. Therefore, the potential advantage of californium rests upon its lower OER. It is commonly believed that one of the limitations of radiotherapy is the presence of a hypoxic fraction of cells in tumours. From numerous experiments it has been established that the OER of fast neutrons is lower than that of gamma rays. The OER is a measure for comparison of the doses required for a specific biological endpoint in the absence and in the presence of oxygen. Laboratory studies of RBE can provide a useful guide to the doses to be applied in clinical practice with californium radiation. The RBE is a measure for comparison of the doses of californium and radium gamma rays needed for a specific biological endpoint. The two quantities of practical interest are the relative biological effectiveness, RBE, and more » the oxygen enhancement ratio, OER. Since the discovery of /sup 252/Cf and its production for biological research in the late sixties, several tens of reports on responses of many biological systems to treatments with Cf-neutrons have been published. The effective half-life dominated by alpha decay is about 2.66 year. Californium decays by alpha emission and by spontaneous fission where fission fragments, X and gamma rays and neutrons are emitted. ![]() Source holder : from height adjust rod to source centre : 8 cms.The isotope californium-252 was first isolated and characterized after the nuclear explosion which took place in the Eniwetok Island complex in November 1952.All plates have the provision to place the source adjust rod at the centre or mid-point or edge of the bell-jar. ![]() Hence maximum board size 18 X 18 cms (including any plugs & sockets)īoard should have feet of at least 5cm to allow for cabling.īoards should sit horizontal and NOT mounted vertically.īNC bulkhead vacuum connectors (socket to socket) Bell jar :27cm diameter base, 20 cm high (+ 10 cm radius dome).These laser-based systems will be able to map the chip topography and will not carry with them the inherent radiation hazards associated with the partially-sealed Cf-252 sources. As the CASE system is a low rate pre-test facility that cannot be focussed onto particular regions of interest on the chip studies are now being carried out into the use of laser-based test systems. As memory density and processor complexity increases more and more metallisation layers are being used which makes it more difficult for the fission products to penetrate through to the sensitive volume. To increase the fission product fluence at the device under test (DUT) the device itself needs to be decapsulated and the CASE system operated in an evacuated bell jar. The average Linear Energy Transfer (LET) of the fission products is 43 MeV/(mg/cm 2 ). The spontaneous fissioning 252Cf sources used have typical activities of 1 - 2 ♜i (40-50kBq) with the following properties :ĭecays by alpha emission (96.9%) to 248Cm or spontaneous fission (3.1%)Īn average of 3.7 neutrons per fission with an average energy of 2.3MeV.Ĭf-252 has a very high specific activity (ie 1 gram equals 20TBq (537Ci)).Īt 1m a 1 ♜i source produces a dose equivalent of 23.3 µSv/hr (n's)& 1.6 µSv/hr (γ's). Californium Assessment for Single event Effects ![]()
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