Semiconductor radiation detector
AssigneeThe Regents of the University of California
InventorsLeon Kaufman, Kenneth E. Hosier, Jr.
Life of this patent
Estimating the term…
Abstract
An electrical charge amplifier including a filter circuit is AC coupled to a semiconductor (CdTe) detector and generates a voltage pulse in response to an electrical charge generated in the detector by an incident pulse of radiation. The filter allows only frequencies within a predetermined range to contribute to the voltage pulse. The selected range of frequencies is determined in accordance with the duration of the incident radiation pulse such that the voltage pulse faithfully represents the magnitude of incident radiation in spite of undersirable detector characteristics which would otherwise introduce distortions. Exemplary charge amplifier and detector structures are also described.
Claims59
A radiation detecting apparatus for use in detecting incident radiation pulses of predetermined duration, said detector comprising:
- a semiconductor detector which generates electrical charge in response to incident radiation, said detector being disposed to receive at least a portion of said radiation pulses;
- signal processing means, AC coupled electrically to said semiconductor detector for generating an output electrical signal accurately representing said incident radiation,
- said signal processing means including filter means for allowing only frequency components within a predetermined range of frequencies to contribute to said output electrical signal, said range of frequencies being determined in accordance with the duration of said incident radiation pulses so that said output electrical signal is undistorted by variations in internal electrical characteristics of the semiconductor detector.
Apparatus of the type including (a) means for generating pulses of penetrating radiation having predetermined duration, (b) a detector disposed to receive a portion of said radiation, said detector exhibiting at least one of the adverse high current leakage, tailing, polarization, or memory properties, and (c) signal processing means responsive to electrical signals generated by the detector for providing an output electrical signal accurately representing the intensity of the radiation received by said detector, wherein:
- said signal processing means is AC coupled to said detector and includes filter means for allowing only frequency components within a predetermined range of frequencies to contribute to said output electrical signal, said range of frequencies being in accordance with said radiation pulse duration so that distortion in said output signal due to said exhibited detector properties are substantially eliminated.
A tomographic scanner for providing a plurality of radiation beam transmission/absorption measurements taken along each of plural paths with a cross-section of a three-dimensional body and for computing from such measurements the relative radiation absorptions occurring at incremental areas disposed within said cross-section, said tomographic scanner comprising:
- means for generating a pulsed beam of said radiation, said beam pulses being of predetermined duration;
- a semiconductor detector, disposed to receive said radiation after passage through said body, the raw output of said detector exhibiting undesirable electrical characteristics;
- signal processing means, AC coupled to said detector, for generating an output signal accurately representing the amount of radiation incident on said detector;
- said signal processing means including filter means for blocking signals for frequencies not within a predetermined range of frequencies from contributing to said output signal, said range of freequencies being determined in accordance with the duration of said radiation pulses so that said output signal is substantially undistorted by said undesirable characteristics of said detector;
- means for effecting a change in the geometric relationship between at least two of said radiation beam, detector, or body, such that said detector receives radiation from along a plurality of different paths through said body;
- and
- data processing means, receptive of said output signal for computing said relative radiation absorptions.
In a tomographic scanner of the type including (a) a source of penetrating radiation, (b) radiation detectors disposed for detecting the radiation after passage through the body along different paths, and (c) data processing means for computing relative radiation absorptions at incremental areas within a cross-section of the body, the improvement wherein:
- said source includes means for generating pulses of said radiation, said pulses having a predetermined duration;
- and
- said detectors comprise a wafer of cadmium telluride having fist and second opposing surfaces with one of said opposing surfaces having a cathode electrode disposed thereon and the other of said opposing surfaces having at least one anode electrode disposed thereon;
- means for developing a bias voltage across said wafer;
- signal processing means, AC coupled to one of said electrodes, for generating an output signal accurately representing radiation incident on the detector, said signal processing means including filter means allowing only signal components from said detector within a predetermined range of frequencies to contribute to said output signal, said range of frequencies being determined to accordance with the duration of said radiation pulse so that the output signal provides an accurate representation of the incident radiation undistorted by adverse internal electrical characteristics of said cadmium telluride wafer.
An apparatus for measuring the intensity of incident radiation pulses having a predetermined duration, said apparatus comprising:
- a wafer of a material selected from the group consisting of CdTe and HgI2 having first and second surfaces defining a predetermined thickness;
- a first conductive layer deposited on said first surface;
- a second conductive layer deposited on said second surface, said second conductive layer including a plurality of individual electrically isolated sections, each serving as a separate electrode to said wafer, whereby a plurality of individual detectors are provided on said wafer;
- and
- a plurality of signal processing means each respectively electrically coupled to a corresponding one of said separate electrodes, for detecting and processing electrical signals presented at said electrodes and for providing output signals accurately representing the intensity of radiation incident on each detector.
In an apparatus for providing a measurement of radiation transmission/absorption by a cross-section of a body disposed between a pulsed radiation source and a detector, an improved detector comprising:
- a wafer of CdTe, having a surface disposed towards said source;
- a first conductive layer disposed on a first surface of the wafer and serving as a first electrode to said wafer;
- a plurality of individual electrically separate conductive layers disposed on another surface of the wafer, said plurality of layers being spaced apart along the length of said second surface and each serving as an electrode to said wafer, whereby an array of individual detectors is provided on said wafer;
- and
- signal processing means AC coupled to each of said plurality of conductive layers for processing the electrical signals presented thereat and for providing corresponding plural output signals which are substantially accurate representations of the radiation incident on each corresponding individual detector.
Apparatus for providing a measurement of relative radiation transmission/absorption by a body, said apparatus comprising:
- means for generating pulses of radiation, said pulses being of a predetermined duration and being directed to irradiate said body;
- detector means, disposed to receive at least a portion of the radiation pulses transmitted through said body, for accumulating an electrical charge in response to said transmitted radiation incident thereon, said charge accumulation being a function of varying time response characteristics within the detector means;
- and
- charge sensitive amplifier and frequency filter means, for generating an output electrical signal in response to said accumulated charge which is substantially independent of said varying time response characteristics.
A method for detecting incident radiation pulses of predetermined duration, comprising the steps of:
- disposing a semiconductor detector to receive at least a portion of said radiation, said semiconductor detector generating an electrical charge in response to said received radiation;
- generating an electrical output signal indicative of said charge;
- and
- filtering out components of said electrical output signal not in accordance with the duration of said radiation pulses so that said electrical output signal is substantially undistorted by characteristics of said semiconductor detector.
An apparatus for measuring the intensity of incident radiation pulses having a predetermined duration, said apparatus comprising:
- a wafer of material selected from the group of CdTe and HgI2 having first and second surfaces defining a predetermined thickness;
- a first conductive layer deposited on said first surface;
- and
- a second conductive layer deposited on said second surface, said second conductive layer including a plurality of individual electrically isolated sections, each serving as a separate electrode to said wafer, whereby a plurality of individual detectors are provided on said wafer.
In an apparatus for providing a measurement of radiation transmission/absorption by a cross-section of a body disposed between a pulsed radiation source and a detector, an improved detector comprising:
- a wafer of a material selected from the group consisting of CdTe and HgI2 having a surface disposed towards said source;
- a first conductive layer disposed on a first surface of the wafer and serving as a first electrode to said wafer;
- and
- a plurality of individual electrically separated conductive layers disposed on a second surface of the wafer, said plurality of layers being spaced apart along the length of said second surface, each serving as an electrode to said wafer, whereby an array of individual detectors is provided on said wafer.
A method for providing a measurement of radiation transmission-absorption by a cross-section of a body, comprising the steps of:
- generating pulses of radiation of predetermined duration;
- directing said radiation pulses to irradiate said body;
- disposing a semiconductor detector to receive at least a portion of said radiation transmitted through said body, said semiconductor detector generating an electrical charge in response to said received radiation;
- generating an electrical output signal indicative of said charge;
- and
- filtering out components of said electrical output signal not in accordance with the duration of said radiation pulses so that said electrical output signal is substantially undistorted by characteristics of said semiconductor detector.
A method for providing a measurement of radiation transmission/absorption by a cross-section of a body, comprising the steps of:
- generating pulses of radiation of predetermined duration;
- directing said radiation pulses of irradiate said body;
- disposing a wafer of material selected from the group of CdTe and HgI2 to receive at least a portion of said radiation transmitted through said body;
- disposing on one side of said wafer a plurality of spaced apart electrodes and on an opposing surface a common electrode, respective electrical charges being developed between said plurality of electrodes and said common electrode;
- generating respective electical output signals indicative of said respective electrical charges;
- and
- filtering said respective electrical output signals to develop respective filtered electrical output signals having only frequency components within a predetermined range of frequencies in accordance with the duration of said radiation pulses;
- and
- processing said filtering electrical output signals to provide an accurate representation of the intensity of the radiation.
A method for using in an apparatus for measuring relative radiation transmission/absorption of a body a radiating detector having at least one of the adverse properties of high current leakage, tailing, polarization, or memory properties, comprising the steps of:
- directing pulses of radiation to irradiate said body, said pulses being of predetermined duration;
- disposing said radiation detector to receive at least a portion of said radiation transmitted through said body, said radiation detector generating an electrical charge in response to said received radiation;
- generating an electrical output signal indicative of said electrical charge;
- filtering said electrical output signal to develop a filtered output signal containing only frequency components within a range of frequencies in accordance with said predetermined duration of said radiation pulse such that frequency components associated with said adverse properties of said detectors are substantially eliminated from said filtered output signal;
- and
- processing said filtered output signal to provide an accurate representation of said transmission/absorption.
A method for providing simultaneous measurements of radiation transmission/absorption in a plurality of adjacent cross-sections of a body, comprising the steps of:
- directing pulses of radiation to irradiate said respective cross-sections;
- disposing a wafer of material selected from the group of CdTe and HgI2 having disposed on one surface thereof a plurality of spaced apart electrodes and on an opposing surface a common electrode, such that each of said plurality of electrodes receives a radiation transmitted through a respective one of said cross-sections, and develops a respective electrical charge in said wafer in accordance with said received radiation;
- generating respective electrical output signals indicative of said respective electrical charges;
- and
- filtering said respective electrical output signals to develop respective filtered electrical output signals having only frequency components within a predetermined range of frequencies in accordance with the duration of said radiation pulses;
- and
- processing said respective filtered electrical output signals to provide respective representations of the transmission/absorption of said respective cross-sections.
A method for providing simultaneous measurements of radiation transmission/absorption of a body at a plurality of effective energy levels, comprising the steps of:
- directing pulses of radiation to irradiate said body, said pulses being of predetermined duration;
- disposing a wafer of material selected from the group of CdTe and HgI2 having a common electrode on one opposing surface, such that at least a portion of said radiation pulse transmitted through said body is incident on a surface of said wafer transverse to said one surface and said opposing surface to develop respective charges between said plural electrodes and said common electrode in accordance with the intensity of the radiation passing into the region of said wafer between respective ones of said plurality of electrodes and said common electrode;
- disposing on one side of said wafer a plurality of spaced apart electrodes and on an opposing surface a common electrode, respective electrical charges being developed between said plurality of electrodes and said common electrode;
- generating respective electrical output signals indicative of said respective electrical charges;
- and
- filtering said respective electrical output signals to develop respective filtered electrical output signals having only frequency components within a predetermined range of frequencies in accordance with the duration of said radiation pulses;
- and
- processing said respective filtered electrical output signals to provide accurate representations of said radiation transmission/absorption at the energy levels associated with said radiation passing through respective distances of CdTe.
Dependencies are inferred from the claim text.