![]() ![]() Of these observables, the prompt neutron spectrum, prompt neutron multiplicity, prompt gamma spectrum, and prompt gamma multiplicity are crucial for accurate transport simulations of criticality and nonproliferation applications. As the CGMF code was recently integrated into the MCNP6.2 transport code, great emphasis has been placed on providing optimal parameters to CGMF such that many different observables are accurately represented. « lessĬGMF is a Monte Carlo code that simulates the decay of primary fission fragments by emission of neutrons and gamma rays, according to the Hauser-Feshbach equations. The methods and means of measurement provide for certifying routine fission fragment sources on fragment radiation activity with errors of 1.3% for 0.95 confidence probability. spectra is measured by a silicon surface-barrier detector. The more » latter method measures activity from the alpha emission where the. Certification and measurement methods based on ionization chambers and radiometers containing semiconductor detectors and a method which employs spectrometry and alpha radiation measurement were comparatively evaluated for efficiency and energy resolution. The basic certified quantity is the fragment radiation activity. Data are given for these nuclides, including their alpha decay and spontaneous fission half-lives and their. 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. The isotope californium-252 was first isolated and characterized after the nuclear explosion which took place in the Eniwetok Island complex in November 1952. ![]()
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