Showing papers on "Fluence published in 1978"

Low temperature irradiation of Nb3Sn and V3Si with high energy sulphur ions

Abstract: The critical temperature Tc, the transition width To and the residual resistance R0 of Nb3Sn and V3Si have been measured as functions of the fluence of 20 MeV sulphur ions below 20 K and isochronal annealing up to 290 K. The temperature dependence of the resistivity is reported for samples with different irradiation-induced states of damage. Tφ and the thermal part of the resistivity are unambiguously correlated to the Tcversus fluence behavior. At high fluences the Tc of Nb3Sn again shows a minimum as a function of fluence, as reported earlier for oxygen irradiation. The temperature coefficient of the resistivity changes from positive to negative when the Tc of Nb3Sn passes through the minimum. A qualitatively different annealing behavior of Tc and R0 is observed for samples irradiated to Tc. values before and after the minimum. Highly damaged Nb3Sn shows an increase of R0 with increasing annealing temperature. The results are compared with A15 irradiations with different projectiles and with heavy ion irradiations of superconducting elements.

The accumulation of disorder, subject to saturation and sputter limitation, in ion irradiated solids

Abstract: The depth distribution of disorder and the depth integrated disorder produced by ion irradiation of solids is analysed theoretically as a function of increasing ion fluence when disorder saturation processes operate at all depths and the solid surface is continuously uniformly eroded by sputtering. The resulting defining equations are evaluated numerically for a Gaussian approximation to the disorder depth function with parameters appropriate to low, equal and high projectile: substrate mass ratio conditions, for several values of sputtering coefficient and effective atom displacement energy. It is shown that the form, if not the magnitude, of the integrated disorder/projectile fluence function is only weakly dependent upon these parameters. More meaningful comparison with depth resolved disorder functions is, however, possible and such a comparison is made for 100 keV Sb projectiles on a Si substrate.

Superconductivity in irradiated A-15 compounds at low fluences. I. Neutron-irradiated V 3 Si

Abstract: The behavior of the superconducting transition temperature T c of singlecrystal and polycrystalline V3Si was investigated as a function of low-fluence neutron irradiation. It is found that the initial degradation of T c is sample-dependent, some specimens showing no degradation in T c up to a fluence of 2 × 1018 n/cm2. This and many other earlier observations on low-fluence behavior are explained in terms of a recently proposed model of radiation damage in A-15 compounds.

Irradiation effects in high-purity InSb

Abstract: Galvanomagnetic and thermoelectric results are reported for high-purity InSb electron-irradiated at 10 K. Damage results have been studied for a fluence up to 2.7 × 1018 e/cm2 and the defect recovery has been investigated between 50 and 220 K. The effects of electrically active defects on the transport properties of InSb are discussed; these are apparently more complicated than has been believed previously; there is strong evidence for a semiconductor-to-metal transition at low temperatures and high defect concentrations.

Silicon Detector Compensation by Nuclear Transmutation.

Abstract: : The effects of nuclear transmutation doping in high quality detector grade silicon have been studied. A theoretical treatment of the variations of electrical parameters with fluence and the experimental isochronal annealings of float zone Si, transmutation doped are presented. It is found that several annealing stages observed previously only in Czochralski Si are also observed in this lightly compensated float zone Si. A large concentration of acceptors is produced as a result of thermal irradiation and annealing to 500 C. This concentration is independent of fluence and appears to be related to residual Si impurities previously undetected by electrical, optical or neutron activation analysis experiments. Defect decoration of oxygen or carbon impurities is believed to be the source of these acceptors. Techniques have been devised to produce very high resistivities as a result of high precision nuclear transmutation compensation in nominally undoped material.

The role of radiative transfer in pulsed laser plasma-target interactions

Abstract: The plasma generated when a 2024 aluminum target was irradiated with the beam from a cold cathode electron beam laser (CCEBL) has been investigated with spectroscopic techniques. The target was designed to form the end plate of a differentially pumped slit assembly attached to a McPherson Model 225 visible-u.v.-v.u.v. monochromator. A pinhole in the center of the plate permitted plasma radiation to enter the monochromator from the back side of the target. Calibration with tungsten, deuterium and argon standards permitted quantitative plasma radiance measurements to be made in the region 115–600 nm using a range of diffraction gratings and photomultiplier tubes. The total radiant fluence observed (1 J/cm 2 ) was in reasonable agreement with the 1-1.2J/cm 2 of absorbed thermal fluence determined by independent thermal coupling measurements. Photographic spectra of the plasma (100–620 nm) were recorded and many features identified.