Dosimeter
First Claim
1. A radiation dosimeter comprising a pair of silicon insulated gate field effect transistors integrated into the same substrate, each having a gate, a source, and a drain, means for measuring a first differential threshold voltage between the transistors, means for forward biasing the gate of the first transistor and inhibiting operation of the second, while allowing both to be subjected to ionizing radiation, means for measuring a second differential threshold voltage between the transistors following said irradiation, the difference between said differential threshold voltages being indicative of the radiation dosage.
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Accused Products
Abstract
The invention is a radiation dosimeter and method of operation of its elements comprising a pair of silicon insulated gate field effect transistors integrated into the same substrate, each having a gate, a source and a drain. The dosimeter includes apparatus for measuring a first differential threshold votlage between the transistors, appartus for forward biasing the gate of the first transistor and inhibiting operation of the second, while allowing both to be subjected to ionizing radiation, and apparatus for measuring a second differential threshold voltage between the transistors following the irradiation. The first differential threshold voltage can be subtracted from the second to obtain a measure of the radiation dosage. Threshold drift and offset is thereby substantially eliminated.
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Citations
24 Claims
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1. A radiation dosimeter comprising a pair of silicon insulated gate field effect transistors integrated into the same substrate, each having a gate, a source, and a drain, means for measuring a first differential threshold voltage between the transistors, means for forward biasing the gate of the first transistor and inhibiting operation of the second, while allowing both to be subjected to ionizing radiation, means for measuring a second differential threshold voltage between the transistors following said irradiation, the difference between said differential threshold voltages being indicative of the radiation dosage.
- 2. A radiation dosimeter comprising first and second insulated gate field effect transistors integrated in the same substrate, each having a source, drain and gate, the sources being connected together, means for connecting a first voltage source positively poled toward the gate of the first transistor between its source and gate, and means connecting a second voltage source positively poled toward the gate of the second transistor between its source and gate, the second voltage source having less potential difference than that of the first voltage source, and means connecting the drains of said transistors together.
- 13. A radiation dosimeter comprising a first drain to source, cascade interconnection of a first plurality of insulated gate field effect transistors (IGFETs), and a second drain to source cascade interconnection of a second plurality of insulated gate field effect transistors (IGFETs) similar in number to the first, all integrated into the same substrate, means for positive biasing each of the gates of the first plurality of transistors and for biasing each of the gates of the second plurality of transistors to bias levels less than those of the first plurality of transistors, and means connecting drains of transistors at the ends of the respective cascade interconnections together.
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17. A method of measuring ionizing radiation dosage comprising:
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(a) measuring a first differential threshold voltage between a pair of similar insulated gate field effect transistors integrated into the same substrate, (b) positively biasing the gate of the first transistor and inhibiting operation of the second, while allowing both to be subjected to ionizing radiation, (c) measuring a second differential threshold voltage between the transistors following said irradiation, and (d) subtracting the first from the second differential threshold voltage to obtain a measure of the radiation dosage. - View Dependent Claims (18, 19, 20, 21, 22)
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23. A method of measuring radiation dosage comprising:
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(a) connecting the sources of two insulated gate field effect transistors (IGFETs), integrated in the same substrate, together, (b) connecting the gate of each transistor to its corresponding drain, (c) applying equal currents between the drains and sources of each transistor, (d) measuring a first voltage between the drains of the two transistors, (e) applying a first biasing voltage between the gate and source and drain of the first transistor, poled to positive bias the gate of the first transistor, (f) applying a second biasing voltage which is between zero and a level significantly less than the first biasing voltage between the gate and source and drain of the second transistor, poled to zero bias or positive bias the gate of the second transistor, (g) connecting the drains of the transistors together, (h) allowing both transistors to be subjected to ionizing radiation, (i) removing the application of first and second biasing voltage and disconnecting the drains from each other, (j) repeating steps (b), (c), and (d) but this time in step (d) measuring a second voltage between the drains of the transistor, and (k) subtracting the initially measured voltage of step (d) from the subsequently measured voltage of step (d) to obtain a measure of the radiation dosage recorded by the first transistor. - View Dependent Claims (24)
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Specification