摘要:
A method and apparatus for detecting slow neutrons by monitoring Lyman alpha radiation produced by the 3He(n,tp) nuclear reaction induced by neutrons incident on a gas cell containing 3He or a mixture of 3He and other atoms and/or molecules. Such a method and/or apparatus includes the use of, for example, liquid 3He and 4He mixtures as a scintillation counter for the sensitive detection of neutrons using Lyman alpha radiation produced by the 3He(n,tp) reaction. The radiation can be detected with high efficiency with an appropriate photo-detector, or alternatively, it can be converted to radiation at longer wavelength by absorption in scintillation materials, with the radiation channeled to a photodetector. Because of the simplicity of the system and the fact that the radiation production mechanisms can be measured and/or calculated independently, the method and/or apparatus also has the potential for service as a calculable absolute detector.
摘要:
A method and apparatus for detecting slow neutrons by monitoring Lyman alpha radiation produced by the 3He(n,tp) nuclear reaction induced by neutrons incident on a gas cell containing 3He or a mixture of 3He and other atoms and/or molecules. Such a method and/or apparatus includes the use of, for example, liquid 3He and 4He mixtures as a scintillation counter for the sensitive detection of neutrons using Lyman alpha radiation produced by the 3He(n,tp) reaction. The radiation can be detected with high efficiency with an appropriate photo-detector, or alternatively, it can be converted to radiation at longer wavelength by absorption in scintillation materials, with the radiation channeled to a photodetector. Because of the simplicity of the system and the fact that the radiation production mechanisms can be measured and/or calculated independently, the method and/or apparatus also has the potential for service as a calculable absolute detector.
摘要:
The present invention relates to apparatus and methods for use in highly sensitive and efficient neutron detection, that includes using trigger reactions to initiate far-ultraviolet (FUV) optical emissions. In some embodiments of the present invention, a method for the detection of slow neutrons includes absorption of a slow neutron with a high neutron capture-cross-section nucleus, decay of the compound nucleus into energetic particles, creation of excimers from the energetic particles reacting with a background gas to form excimers, radiative decay of excimers resulting in emission of FUV radiation, and detection of the FUV radiation using an optical detector.
摘要:
A hoist having a motor, gear reduction unit, drum, and an emergency brake on the drum or on a drive-coupled element close to the drum. A brake-actuating mechanism is operated in response to a mechanical out-of-sync detector with mechanical inputs directly from the motor shaft and drum shaft or a shaft coupled to the drum. The detector has an output shaft which signals to actuate the brake actuator when there is a variation in the relative angular velocities between the two input shafts to the detector to set the brake. In one embodiment, the output shaft rotation provided from the variation in the relative velocities of the input shafts also provides the force for applying the emergency brake. In another embodiment, the brake is set by a large force spring which is controlled by a trigger mechanism. In still other embodiments, the mechanical detector is driven by an overspeed or speed-sensitive clutch, and/or by an electrically operated clutch.
摘要:
An ultrasensitive mass spectrometry method based on multiphoton sub-Doppler resonance ionization to measure abundance sensitivities. The method preferentially ionizes a selected isotope in a sample by using Doppler-free resonant multiphoton ionization to produce an enhanced ratio of selected isotopes. Background species are separately ionized and rejected. As necessary or desired, selected isotope ions are preferentially ionized by using a second Doppler-free resonant multiphoton ionization to provide an additional isotope enhancement. The ions produced are injected into a mass spectrometer. Isotopic spectrum analysis of the ions is performed by the spectrometer and the ions are then detected by a detector such as a particular photon multiplier capable of observing a single ion. In one embodiment, at least one of the steps of preferentially ionizing the selected isotope is accomplished by two counter propagating laser beams of slightly different frequencies. Further improved sensitivity is achieved by: (1) using a frequency offset of the laser frequency in an amount proportional to the laser intensity to overcome AC Stark shifts, and (2) withdrawing ions for mass separation from only the central portion of the laser interaction volume.
摘要:
A solid state amplifier includes at least one junction field effect transistor and an impedance network coupled between a signal input terminal of the amplifier and a gate terminal of the transistor. The network includes a p-n junction device having a region of conductivity opposite to that of the gate of the transistor coupled to the gate terminal, the p-n junction being shunted by a resistor coupled in parallel therewith. The network minimizes signal distortion which would otherwise be introduced to the signal output of the amplifier when an inductive load is present in the output circuit of the amplifier.
摘要:
An ultrasensitive mass spectrometry method based on multiphoton sub-Doppler resonance ionization is used to measure abundance sensitivities. The method preferentially ionizes a selected isotope in a sample by using Doppler-free resonant multiphoton ionization to produce an enhanced ratio of selected isotopes. As necessary or desired, selected isotope ions are preferentially ionized by using a second Doppler-free resonant multiphoton ionization to provide an additional isotope enhancement. The ions produced are injected into a mass spectrometer (24). Isotopic spectrum analysis of the ions is performed by the spectrometer (24) and the ions are then detected by a detector (26) such as a particular photon multiplier capable of observing a single ion. In one embodiment, at least one of the steps of preferentially ionizing the selected isotope is accomplished by two counter propagating laser beams of slightly different frequencies.