Atom Sciences, Inc.

Norbert Thonnard

George S Hurst

Harold W Schmitt

G Samuel Hurst

Tom J Whitaker

Marvin G Payne

Steve L Allman

A dosimeter which incorporates new methods for determining neutron dose. Less than one millirad of dose due to neutrons of all energies down to approximately 10.sup.3 eV can be measured, and the response can be adjusted by design of the dosimeter. The dosimeter utilizes the sputtering of material from a target due to the action of the neutrons and measuring of the amount of sputtered material to determine the dose. The sputtered material may be, for example, a noble gas or an inert solid. Various radiator materials can be included to interact with the neutrons so that the resulting charged particles control the sputtering process and hereby increase the sensitivity of the dosimeter. The target material can be, for example, noble-gas-impregnated polycrystalline or amorphous metals. The sputtered material is analyzed using resonance ionization spectroscopy, sputter-initiated resonance ionization spectroscopy or other methods to determine its quantity and hence the neutron dose. Applications include, but are not limited to, personnel neutron dosimetry and stationary neutron monitors.

Neutron dosimeter

An improved method of operating a time-of-flight mass spectrometer. This method, which involves double pulsing, achieves an increase in the resolution of TOF mass spectrometers by compensating for the energy spread of the species extracted from the source and thus the time spread of ions of a specific mass arriving at a detector. According to this improved method, atoms (or molecules) for analysis are rapidly removed from a surface at a first well defined time. These atoms or molecules are then rapidly ionized at a location or region a distance, R, from the surface at a second well defined time after a selected time delay, T.sub.o. The resultant ions first move through a region of uniform electric field of a distance, S.sub.1, and then into a field-free region having a length, S.sub.2, Lastly, ions leaving the field-free region enter a short high energy accelerating region so as to impinge upon an ion detector. The output signal of the detector, as a function of arrival time, is an indication of the mass distribution of the ions and thus the analysis of the atoms or molecules. A proper choice of the uniform electric field and parameters R, S.sub. 1, S.sub.2 and T.sub.o provide compensation for the energy spread of ionized species and thus a reduction in time spread of ions at the detector. Certain special cases for enhanced resolution are described, as well as operation of the TOF according to the improved method to achieve atom enrichment of a specific mass.

Double pulsed time-of-flight mass spectrometer

Method and apparatus for determining small quantities of specific atoms with isotopic selectivity. According to the method described herein, atoms are rapidly released from an atom bank containing the same, and are then converted to ions utilizing resonance ionization as achieved with photon beams having specific wave lengths. These ions are extracted from the ionization region and are accelerated and implanted into a second atom bank. For further selectivity, the atoms are then rapidly released from the second bank, ionized with another photon beam of selected wave length to provide ionization of the desired species, with these ions then being extracted, subjected to acceleration, and implanted into the first atom bank. Typically the number of electrons emitted from the atom banks during implantation is used as a measure of the number of atoms of the selected species. In the preferred embodiments, a combination of mass selectivity by ionization together with a mass separator provides for the most rapid and most sensitive method for determining a small quantity of atoms in the presence of a large quantity of atoms.

Growing community of inventors

Anderson County, TN, United States of America

Norbert Thonnard