[en] The switching time of certain semiconductor devices may be reduced without significantly increasing the forward voltage drop or the leakage current by irradiating the device with a monoenergetic radiation source in such a way that the depth of maximum defect generation is adjacent to the PN junction of the device. The radiation source is preferrably a proton or alpha particle source, although there are certain cases where higher molecular weight particles, such as nitrogen ions, may be more desirable. The dosage level of irradiation is ideally between 1 x 10¹⁰ and 5 x 10¹¹ protons per square centimeter, or between 1 x 10⁹ and 5 x 10¹⁰ alpha particles per square centimeter. The method is particularly useful when applied to thyristors and devices including thyristors. (LL)

No abstract available

[en] The recovery charge of power diodes and thyristors is tailored and matched by irradiation through a major surface of the semiconductor body with a given radiation source, preferably of electron radiation, to a dosage corresponding to between about 1 x 10¹² and 8 x 10¹² electrons per centimeter square with 2 MeV electron radiation. The recovery charge of each device of a group of a type of diode or thyristor is first measured and the group divided into subgroups according to the measured recovery charge of each device. The devices of at least one subgroup is then irradiated by a radiation source to dosages corresponding to between about 1 x 10¹² and 8 x 10¹² electrons per centimeter square with 2 MeV electron radiation. The recovery charge of each irradiated device is again measured to determine the incremental change of recovery charge as a function of irradiation dosage. A recovery charge of another device of the type of diode or thyristor is then measured, and the device irradiated with a radiation source to a determined dosage corresponding to a desired incremental change in recovery charge to tailor the recovery charge of said device to a desired value

[en] Irradiated regions are formed in materials such as semiconductor bodies by nuclear radiation where the irradiated regions are of a desired thickness, dosage and dosage gradient, a desired distance from a selected surface of the material. A nuclear radiation beam from a given radiation source radiating particles with molecular weight of at least one (1) is provided that can penetrate the material through a selected surface to a depth greater than the maximum depth of the irradiated region from the selected surface. A beam modifier is formed of a given material and non-uniform shape to modify the energy of the radiation beam on transmission therethrough to form a transmitted radiation beam capable of forming an irradiated region of a desired thickness and dosage gradient in the material a given distance from the selected surface on irradiation of the material through the selected surface with the transmitted radiation beam. The material in which the desired irradiated region is to be formed is positioned with the selected surface thereof to be exposed to the radiation beam from the radiation source on transmission through the beam modifier. The material is thereafter irradiated through the beam modifier and through the selected surface with the radiation beam , preferably while the beam modifier and material are moved relative to each other through a predetermined motion, to form in the material an irradiated region of desired thickness, dosage and dosage gradient, a desired distance from the selected surface. The irradiated region thus formed in semiconductor bodies are particularly of value in changing the electrical characteristics without substantial change of other electrical characteristics

[en] The present invention provides a method of forming an irradiated region of a desired thickness, dosage and dosage gradient in a material such as semiconductor body a desired distance from a selected surface thereof. The invention is particularly useful in tailoring irradiated regions to simulate radiation effects on material properties produced by fast neutrons of a fusion reaction, and in forming irradiated regions changing the electrical characteristics of semiconductor bodies without affecting other electrical characteristics of the body. The method is commenced by providing a radiation beam from a given radiation source radiating particles capable of penetrating a material through a selected surface to greater than the maximum desired distance of the irradiated region from the selected surface. Preferably, such nuclear radiation source is protons or alpha particles produced by a Van de Graaff accelerator forming a substantially monoenergetic radiation beam. The irradiated region is formed by positioning the selected surface of the material to be exposed to the radiation beam through a beam modifier, which is preferably made of aluminum. The beam transmitted through the beam modifier thus irradiates the material through the selected surface and forms the desired irradiated region within the material. The thickness of the irradiated region, i.e., its linear dimension along the path of the radiation beam, and its distance from the selected surface are accurately controlled by the energy of the radiation source and varied thickness of the beam modifier. The dosage is controlled with precision by the contour of the beam modifier and the predetermined relative movement between the beam modifier and material during the irradiation

[en] The concentration of uranium in a moving stream is determined by agglomerating background microbubbles out of the 6 to 10 micron size range, counting microbubbles in the stream which are about 6 to about 10 microns in size, exposing the stream to a radiation source to cause uranium fission fragments to produce microbubbles, counting microbubbles which are about 6 to about 10 microns in size, and subtracting one count from the other and multiplying by a calibration constant. The subtraction can be performed on an earlier first count so that both counts are made on the same volume. The radiation exposure can be automatically increased when the difference between the first and second counts is low

[en] This patent deals with the method and apparatus for measuring the burn-up of nuclear fuel. A curve giving the calculated relationship between the fast neutron emission rate and the burn-up of fuel is prepared. The fast neutron counting rate from a sample of nuclear fuel of known burn-up is measured and the proportionality ratio between that measurement and the fast neutron emission given by the curve for the same burn-up is determined. The fast neutron counting rate of nuclear fuel of unknown burn-up is then measured and multiplied by the proportionality ratio to determine the fast neutron emission rate, from which the unknown burn-up is then determined by means of the curve

[en] A method of reducing the reverse recovery charge of thyristors without substantially increasing forward voltage drop by first determining the depth of the anode pn junction from a major surface adjoining a cathode emitter region. The depth of maximum defect generation in thyristor on irradiation through the major surface with a given radiation source radiating particles with molecular weight greater than one, preferably proton or alpha particles, and adjusting the energy level at the major surface of the thyristor from the radiation source to provide the depth of maximum defect generation adjacent the anode pn junction and preferably in the anode base region within 20 micrometers of the anode pn junction or in the anode emitter region within 15 micrometers of the anode pn junction. Thereafter the thyristor is irradiated through said major surface with the adjusted energy level from the radiation source to a given dosage to reduce the reverse recovery stored charge of the thyristor without substantially increasing the forward voltage drop

[en] This patent describes a nuclear reactor having a pressure vessel, and a core within the pressure vessel for generating a flux of neutrons and comprising: means for generating fission fragments at a rate proportional to an intensity of the flux; for generating light signals in response to a known fraction of the fission fragments, the light generating means having a thickness approximately on the order of a maximum penetration range of the fission fragments in the light generating means; means, optically coupled to the light signal generating means, for generating electrical signals in response to the light signals; and means, electrically coupled to the electrical signal generating means, for processing the electrical signals to determine intensity

[en] This patent describes a method of measuring the burnup of nuclear fuel. It comprises: measuring the fast neutron counting rate of the nuclear fuel; reading the burnup off a curve which expresses the relationship between neutron emission rate and burnup for a nuclear fuel of comparable history, where the emission rate which corresponds to the neutron counting rate is obtained by multiplying the neutron counting rate by the ratio of the neutron emission rate given by the curve for nuclear fuel of comparable history and known burnup to its similarly measured counting rate, and is defined by the formula n/s = l.34 x 10^-3 3.92 where n/s equals neutron emission rate