CA1121922A - Radiation detection device - Google Patents
Radiation detection deviceInfo
- Publication number
- CA1121922A CA1121922A CA000315183A CA315183A CA1121922A CA 1121922 A CA1121922 A CA 1121922A CA 000315183 A CA000315183 A CA 000315183A CA 315183 A CA315183 A CA 315183A CA 1121922 A CA1121922 A CA 1121922A
- Authority
- CA
- Canada
- Prior art keywords
- electrode
- high voltage
- entrance window
- electrically connected
- housing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
26.10.78 PHD 77-126 ABSTRACT:
The invention relates to a radiation detection device, comprising a housing which comprises an entrance window and in which at least one ionization chamber detec-tor is arranged. The detector comprises a flat high-voltage electrode which is directed transversely of the entrance window and a flat collector electrode which is arranged to be at least substantially parallel thereto. The end faces of these electrodes which face the entrance window are in electrically conductive contact with a flat auxiliary electrode which extends parallel, to the entrance window.
As a result, a small direct current flows in the direction transversely of the other electrodes during operation, because the auxiliary electrode has a low electrical con-ductivity. Consequently, the electrical field in the ioni-zation chamber detector is very homogeneous, with the re-sult that optimum adjustment of the detector in respect of measuring speed can be realized.
The invention relates to a radiation detection device, comprising a housing which comprises an entrance window and in which at least one ionization chamber detec-tor is arranged. The detector comprises a flat high-voltage electrode which is directed transversely of the entrance window and a flat collector electrode which is arranged to be at least substantially parallel thereto. The end faces of these electrodes which face the entrance window are in electrically conductive contact with a flat auxiliary electrode which extends parallel, to the entrance window.
As a result, a small direct current flows in the direction transversely of the other electrodes during operation, because the auxiliary electrode has a low electrical con-ductivity. Consequently, the electrical field in the ioni-zation chamber detector is very homogeneous, with the re-sult that optimum adjustment of the detector in respect of measuring speed can be realized.
Description
1 PHD. 77-126 The invention relates to a radiation detection device, comprising a housing which comprises an entrance window and in which there is arranged at least one ioniza-tion chamber detector which comprises a flat high-voltage electrode which is directed transversely of the entrance window and a flat collector electrode which is arranged to be substantially parallel thereto and which comprises an end face which faces the entrance window and which is electrically conductively connected to a contact face which is situated opposite the end face and which forms part of a flat auxiliary electrode which extends parallel to the entrance window.
A radiation detection device of this kind is par-ticularly suitable for use in a computer tomography apparatus in which a body is irradiated from a large number of directions by means of a fan-shaped radiation beam. A
- radiation detection device comprising a large number of detectors serves to measure the radiation absorption of the body along a large number of radiation paths; on the basis of these measuring data, the density distribution of the - irradiated part of the body is calculated and displayed on, for example, a television monitor by means of a computer.
A known radiation detection device of the des-cribed kind has an auxiliary electrode, which is made of an electrically suitably conductive material, extending as far as the vicinity of the high-voltage electrode. This auxi-liary electrode intercepts charge carriers formed by ionization which, in the case of a detector without such an auxiliary electrode, would be incident on the entrance window instead of on the collector electrode, so that they would not contribute to a detector output signal. Because the auxiliary electrode is electrically conductively con-nected to the collector electrode, the charge carriers intercepted by the collector electrode do contribute to the detector output signal. As a result, the detection efficiency of the detector is high in co-mparison with a detector which does not include such an auxiliary elec-,., ~
6~
A radiation detection device of this kind is par-ticularly suitable for use in a computer tomography apparatus in which a body is irradiated from a large number of directions by means of a fan-shaped radiation beam. A
- radiation detection device comprising a large number of detectors serves to measure the radiation absorption of the body along a large number of radiation paths; on the basis of these measuring data, the density distribution of the - irradiated part of the body is calculated and displayed on, for example, a television monitor by means of a computer.
A known radiation detection device of the des-cribed kind has an auxiliary electrode, which is made of an electrically suitably conductive material, extending as far as the vicinity of the high-voltage electrode. This auxi-liary electrode intercepts charge carriers formed by ionization which, in the case of a detector without such an auxiliary electrode, would be incident on the entrance window instead of on the collector electrode, so that they would not contribute to a detector output signal. Because the auxiliary electrode is electrically conductively con-nected to the collector electrode, the charge carriers intercepted by the collector electrode do contribute to the detector output signal. As a result, the detection efficiency of the detector is high in co-mparison with a detector which does not include such an auxiliary elec-,., ~
6~
2 PHD~ 77-126 trode. Radiation which enters the detector vla the entrance window produces a comparatively large number of charge carriers in the immediate vicinity of the entrance window, because the intensity of the radiation, and the associated number of ionizations caused thereby, exponen-tially decreases as a function of the distance from the entrance window in the direction transversely of this window.
In the known detector, the distance between the auxiliary electrode and the high-voltage electrode is smaller than the distance between the collector electrode and the high-voltage electrode. As a result, after appli-cation of a high voltage between the electrodes, the electrical field arising between the auxiliary electrode and the high-voltage electrode will be larger than the electrical field arising between the collector electrode and the high-voltage electrode. The electrical field in the detector thus exhibits a spatial inhomogeneity, with the result that the detector is comparatively slow, be-cause the measuring speed, being proportional to thedrift speed of charge carriers formed by ionization, is limited in the case of high electrical field strengths by space charges caused by avalanches of secondary ioniza-tions and in the case of low electrical field strengths by the value of this field strength.
The invention has for its object to provide a radiation detection device which offers a high detection efficiency and in which said drawback is mitigated. To this end, a radiation detection device of the kind set forth in accordance with the invention is characterized in that a second contact face of the auxiliary electrode having a comparatively high electrical resistance measured in the direction transversely of the collector electrode, is situated opposite an end face of the high-voltage electrode facing the entrance window and is electrically conductively connected to the high-voltage electrode.
~ uring operation of the detec~or, a compara-
In the known detector, the distance between the auxiliary electrode and the high-voltage electrode is smaller than the distance between the collector electrode and the high-voltage electrode. As a result, after appli-cation of a high voltage between the electrodes, the electrical field arising between the auxiliary electrode and the high-voltage electrode will be larger than the electrical field arising between the collector electrode and the high-voltage electrode. The electrical field in the detector thus exhibits a spatial inhomogeneity, with the result that the detector is comparatively slow, be-cause the measuring speed, being proportional to thedrift speed of charge carriers formed by ionization, is limited in the case of high electrical field strengths by space charges caused by avalanches of secondary ioniza-tions and in the case of low electrical field strengths by the value of this field strength.
The invention has for its object to provide a radiation detection device which offers a high detection efficiency and in which said drawback is mitigated. To this end, a radiation detection device of the kind set forth in accordance with the invention is characterized in that a second contact face of the auxiliary electrode having a comparatively high electrical resistance measured in the direction transversely of the collector electrode, is situated opposite an end face of the high-voltage electrode facing the entrance window and is electrically conductively connected to the high-voltage electrode.
~ uring operation of the detec~or, a compara-
3;~2 3 PHD. 77-126 tively small direct current flows from the high-voltage electrode through the auxiliary electrode to ~he collector electrode, with the result that the voltage difference between a point of the auxiliary electrode and the collec-tor electrode linearly increases with the distance betweensaid point and the collector electrode. The electrical field between the high-voltage electrode and the collector electrode is thus homogeneous as far as in the auxiliary electrode as if it were. Since the electrical field in the ionization chamber will be as homogeneous as described before too when the first and the second contact face of the auxiliary electrode are electrically conductively con-nected to a potential which equals the high-voltage elec-trode potential and the collector electrode potential respectively, whereby the contact faces may be situated on ~he side of the auxiliary electrode facing the electrodes or on the side of the auxiliary electrode facing the entrance window as well, the meaning of "electrically con-ductively connected to a contact face" has to be under-stood in a broad sense. When this field is chosen to beso large that avalanches of secondary ionizations are just precluded, the adjustment of the detector is optimum in respect of measuring speed.
A preferred embodiment of the radiation detec-tion device in accordance with the invention is character~
ized in that the collector electrode consists of a flat, electrically insulating support, a flat side of which is provided with an electrically conductive layer in order to intercept charge carriers formed by ionizations in the de-tector, an end face of said support being provided with anearthed metal strip which is electrically conductively connected to the first contact face of the auxiliary elec-trode.
Because the collector electrode of an ionization chamber detector is on average at least substantially at earth potential during operation, the electrical field between the high-voltage electrode and the collector elec-26.10.78 L~ P~ID 77-126 trode is also-homogeneous as far as in the auxiliary elec-trode as if it were in this preferred embodiment of the radiation detection device. Because, moreover, the signal current generated between the electrodes by ionization during operation and the direct curren-t through the auxiliary electrode are isolated from each other, noise on the direct current through the auxiliary electrode, having a high resistance, cannot have an adverse effeet on the signal current.
A very simple radiation detection device in accordance with the invention is characterized in that the auxiliary electrode is formed by a resistance layer which directly contacts the end face of the collector electrode and the end face of the high-voltage electrode.
When the auxiliary electrode is brought into direct contact with the end faces, moreover, vibrations of the high-voltage electrode with respect to the collector electrode during operation are attenuated.
~ The invention will be described in detail here-inafter, by way of example, wi-th reference to the accompa-nying diagrammatic drawing~
Figure 1 is a sectional view of a radiation de-tection device in accordance with the invention, Figure 2 is a sectional view of a preferred em-~odiment of a radiation detection device in accordancewith the invention, and ` Figure 3 is a cross-sectional view of a radia-tion detection device in accordance with the invention, taken along the line III-III in Figure 1, illustrating a 3~ special embodiment of the auxiliary electrode.
Figure 1 is a sectional view of a radiation de-tection device in accordance with the invention, compri-sing a housing 1 which is provided with an entrance window 2 wherethrough radiation to be detected, diagrammatically denoted by arrows 3, can enter the housing. In the housing 1 there is arranged an ionization chamber detector 4 which - comp ises a flat high-voltage electrode 5, directed trans-versely of the entrance window 2, and a flat collector 112~922 26.10.78 5 PHD 77-126 electrode 6 which is arranged to be parallel thereto. Via connection wires 7, passed through electrically insul.ated passages 8 through the housing, a high-voltage source 9 can be connected between the high-voltage electrode 5 and the collector electrode 6, said source generating an homo-geneous electrical field, diagrammatically denoted by arrows 10, in the ionization chamber 4. The ionization chamber detector 4 is filled with a medium which can be ionized, for example Xe-gas, and in which free charge carriers are formed by the incident radiation by ioniza-tionO In the ionization chamber detector 4 these chargecarriers cause an electrical current which causes a vol-tage difference across a resistor 11, said difference being applied to an amplifier 12 in order to generate a detector output signal which can be derived from the out-put 13 of the amplifier 12.
The hi.gh-voltage electrode 5 and the collector electrode 6 are secured in the housing by means of insula-ting holders 14.. End faces 15 and 16, facing the entrance window 2, of the collector electrode 6 and the high-voltage electrode 5, respectively, are electrically con-ductively connected in direct contact.to contact faces 17 and 18, situated opposite the end faces 15 and 16, of a flat auxiliary electrode 19 which extends parallel to the entrance windo~ 2.
The auxiliary electrode 19 consists of an homo-: geneous resistance layer and exhibits, measured in the di-rection transversely of the collector electrode 6, a com-paratively high electrical resistance of, for example, 10 to 10 ohms per cm. As a result, during operation of the detector, a comparatively small direct current flows from the high-voltage electrode 5 to the collector electrode ~, said current causing the voltage difference between a point of the auxiliary electrode 19 and the collector electrode 6 to increase linearly with the distance between this point and the collector electrode 6. The electrical field between the high-voltage electrode 5 and the collec-$or electrode 6 is thus homogeneous as far as in the ~Z~92~ 1 26.10.78 6 PHD 77-126 auxiliary electrode 1CJ as if it were. This f`ield is then adjusted to be so large that the appearance of avalanches Or secondary ionizations in the ionization chamber detec-tor is just precluded. As a result, the adjustment of the detector is optimum in respect of measuring speed. In order to isolate the direct current through the auxiliary electrode 19 from the signal current which is generated by the free charge carriers formed during the ionizations and which, consequently, varies pulse-li~e in the time, the voltage difference appearing across the resistor 11 due to the two currents is applied, via a capacitor 20, to the amplifier 12, with the result that the direct voltage component is blocked.
The space Z1 between the entrance window 2 and the auxiliary electrode 19 and the thickness of the auxiliary electrode 19 are shown in exaggerated form in the drawing, but should be as small as possible, because in the housing 1 filled with medium which can be ionized, a~comparatively large number of free charge carriers is formed in the immediate vicinity of the entrance window 2 by the incoming radiation 3, because the intensity of the radiation and the associated number of ioni~ations caused thereby decreases exponentially in the direction trans-versely of the entrance window 2.
Figure 2 is a sectional view of a preferred embodiment of a radiation detection device in accordance with the invention in which reference numerals correspond-ing to Figure 1 are used for corresponding parts. The co~lector electrode 6 consists of a flat, electrically in-sulating support 25, a flat sicle of which is provided with an electrically conductive layer 26 for intercepting free charge carriers formed by ionization in the detector. The othe~ flat side may also be provided with an electrically conductive layer 27 in order to intercept free charge 3~ carriers formed by ionizations in a neighbouring detector.
The end face 15 of the collector electrode 6 is formed by a metal strip 28 which is electrically conductively connected to the contact face 17 of the auxiliary electro-", 2~2 26.10~78 7 PHD 77-126 de 19 and which is isolated from the electrically conduc-tive layers 26 and 27 by a space 29. The metal strip 28 is connected to earth potential in the same manner as the connection of the collector electrode 6 and the high-voltage electrode 5. Because the collector electrode 6 ofthe ionization chamber detector 4 is on average sub-stantially at earth potential during operation, in this preferred embodiment the electrical field 10 is also homo-geneous as far as in the auxiliary electrode 19 as if it were. Because, moreover, the signal current generated by ionizations and the direct current through the auxiliary electrode are isolated from each other by the space 29, noise on the direct current cannot have an adverse effect on the signal current. Moreover, the capacitor 20 in the circuit shown in ~igure 1 can then be omitted.
~ igure 3 is a cross-sectional view of a radia-tion detection device in accordance with the invention, ~taken along the line III-III in Figur-e 1) illustrating a special embodiment of the auxiliary electrode 19. In ~igure 3, parts which correspond to parts in ~igure 1 are again denoted by corresponding reference numerals. The auxiliary electrode 19 consists o~ a flat, electrically insulating support 30 on which a meandered resistance track is provided. Parts 31 of the resistance track which extend in the direction transversely o~ the collector - electrode 6 exhibit a comparatively high electrical re-sistance of, ~or example, from 10 to 10 ohms per cm, whilst parts 32 thereof which extend in the direction parallel to the collector electrode 6 exhibit a low elec-trical resistance. An auxiliary electrode of this kind can be simply and accurately manufactured, for example, by vapour deposition.
A particularly compact radiation detection device which, moreover, offers a high radiation detection efficïency is characterized in that the resistance layer at the same time forms the entrance window of the radia-tion detection device. Because the window 2 and the space 21 are omitted, radiation 3 entering the ionization L!322 26.10.70 8 PHD 77-126 chamber detector 4 will have been attenuated to a small degree`ol~ly.
Preferably, the end faces 16 and 15 of the high-voltage electrode 5 and the collector electrode 6, respec-tively, are electrically conductively connected to theauxiliary electrode 19 by means of an electrically conduc-tive adhesive (not shown in the Figures), so that vibra-tions are additionally attenuated during operation.
A preferred embodiment of the radiation detec-tion device in accordance with the invention is character~
ized in that the collector electrode consists of a flat, electrically insulating support, a flat side of which is provided with an electrically conductive layer in order to intercept charge carriers formed by ionizations in the de-tector, an end face of said support being provided with anearthed metal strip which is electrically conductively connected to the first contact face of the auxiliary elec-trode.
Because the collector electrode of an ionization chamber detector is on average at least substantially at earth potential during operation, the electrical field between the high-voltage electrode and the collector elec-26.10.78 L~ P~ID 77-126 trode is also-homogeneous as far as in the auxiliary elec-trode as if it were in this preferred embodiment of the radiation detection device. Because, moreover, the signal current generated between the electrodes by ionization during operation and the direct curren-t through the auxiliary electrode are isolated from each other, noise on the direct current through the auxiliary electrode, having a high resistance, cannot have an adverse effeet on the signal current.
A very simple radiation detection device in accordance with the invention is characterized in that the auxiliary electrode is formed by a resistance layer which directly contacts the end face of the collector electrode and the end face of the high-voltage electrode.
When the auxiliary electrode is brought into direct contact with the end faces, moreover, vibrations of the high-voltage electrode with respect to the collector electrode during operation are attenuated.
~ The invention will be described in detail here-inafter, by way of example, wi-th reference to the accompa-nying diagrammatic drawing~
Figure 1 is a sectional view of a radiation de-tection device in accordance with the invention, Figure 2 is a sectional view of a preferred em-~odiment of a radiation detection device in accordancewith the invention, and ` Figure 3 is a cross-sectional view of a radia-tion detection device in accordance with the invention, taken along the line III-III in Figure 1, illustrating a 3~ special embodiment of the auxiliary electrode.
Figure 1 is a sectional view of a radiation de-tection device in accordance with the invention, compri-sing a housing 1 which is provided with an entrance window 2 wherethrough radiation to be detected, diagrammatically denoted by arrows 3, can enter the housing. In the housing 1 there is arranged an ionization chamber detector 4 which - comp ises a flat high-voltage electrode 5, directed trans-versely of the entrance window 2, and a flat collector 112~922 26.10.78 5 PHD 77-126 electrode 6 which is arranged to be parallel thereto. Via connection wires 7, passed through electrically insul.ated passages 8 through the housing, a high-voltage source 9 can be connected between the high-voltage electrode 5 and the collector electrode 6, said source generating an homo-geneous electrical field, diagrammatically denoted by arrows 10, in the ionization chamber 4. The ionization chamber detector 4 is filled with a medium which can be ionized, for example Xe-gas, and in which free charge carriers are formed by the incident radiation by ioniza-tionO In the ionization chamber detector 4 these chargecarriers cause an electrical current which causes a vol-tage difference across a resistor 11, said difference being applied to an amplifier 12 in order to generate a detector output signal which can be derived from the out-put 13 of the amplifier 12.
The hi.gh-voltage electrode 5 and the collector electrode 6 are secured in the housing by means of insula-ting holders 14.. End faces 15 and 16, facing the entrance window 2, of the collector electrode 6 and the high-voltage electrode 5, respectively, are electrically con-ductively connected in direct contact.to contact faces 17 and 18, situated opposite the end faces 15 and 16, of a flat auxiliary electrode 19 which extends parallel to the entrance windo~ 2.
The auxiliary electrode 19 consists of an homo-: geneous resistance layer and exhibits, measured in the di-rection transversely of the collector electrode 6, a com-paratively high electrical resistance of, for example, 10 to 10 ohms per cm. As a result, during operation of the detector, a comparatively small direct current flows from the high-voltage electrode 5 to the collector electrode ~, said current causing the voltage difference between a point of the auxiliary electrode 19 and the collector electrode 6 to increase linearly with the distance between this point and the collector electrode 6. The electrical field between the high-voltage electrode 5 and the collec-$or electrode 6 is thus homogeneous as far as in the ~Z~92~ 1 26.10.78 6 PHD 77-126 auxiliary electrode 1CJ as if it were. This f`ield is then adjusted to be so large that the appearance of avalanches Or secondary ionizations in the ionization chamber detec-tor is just precluded. As a result, the adjustment of the detector is optimum in respect of measuring speed. In order to isolate the direct current through the auxiliary electrode 19 from the signal current which is generated by the free charge carriers formed during the ionizations and which, consequently, varies pulse-li~e in the time, the voltage difference appearing across the resistor 11 due to the two currents is applied, via a capacitor 20, to the amplifier 12, with the result that the direct voltage component is blocked.
The space Z1 between the entrance window 2 and the auxiliary electrode 19 and the thickness of the auxiliary electrode 19 are shown in exaggerated form in the drawing, but should be as small as possible, because in the housing 1 filled with medium which can be ionized, a~comparatively large number of free charge carriers is formed in the immediate vicinity of the entrance window 2 by the incoming radiation 3, because the intensity of the radiation and the associated number of ioni~ations caused thereby decreases exponentially in the direction trans-versely of the entrance window 2.
Figure 2 is a sectional view of a preferred embodiment of a radiation detection device in accordance with the invention in which reference numerals correspond-ing to Figure 1 are used for corresponding parts. The co~lector electrode 6 consists of a flat, electrically in-sulating support 25, a flat sicle of which is provided with an electrically conductive layer 26 for intercepting free charge carriers formed by ionization in the detector. The othe~ flat side may also be provided with an electrically conductive layer 27 in order to intercept free charge 3~ carriers formed by ionizations in a neighbouring detector.
The end face 15 of the collector electrode 6 is formed by a metal strip 28 which is electrically conductively connected to the contact face 17 of the auxiliary electro-", 2~2 26.10~78 7 PHD 77-126 de 19 and which is isolated from the electrically conduc-tive layers 26 and 27 by a space 29. The metal strip 28 is connected to earth potential in the same manner as the connection of the collector electrode 6 and the high-voltage electrode 5. Because the collector electrode 6 ofthe ionization chamber detector 4 is on average sub-stantially at earth potential during operation, in this preferred embodiment the electrical field 10 is also homo-geneous as far as in the auxiliary electrode 19 as if it were. Because, moreover, the signal current generated by ionizations and the direct current through the auxiliary electrode are isolated from each other by the space 29, noise on the direct current cannot have an adverse effect on the signal current. Moreover, the capacitor 20 in the circuit shown in ~igure 1 can then be omitted.
~ igure 3 is a cross-sectional view of a radia-tion detection device in accordance with the invention, ~taken along the line III-III in Figur-e 1) illustrating a special embodiment of the auxiliary electrode 19. In ~igure 3, parts which correspond to parts in ~igure 1 are again denoted by corresponding reference numerals. The auxiliary electrode 19 consists o~ a flat, electrically insulating support 30 on which a meandered resistance track is provided. Parts 31 of the resistance track which extend in the direction transversely o~ the collector - electrode 6 exhibit a comparatively high electrical re-sistance of, ~or example, from 10 to 10 ohms per cm, whilst parts 32 thereof which extend in the direction parallel to the collector electrode 6 exhibit a low elec-trical resistance. An auxiliary electrode of this kind can be simply and accurately manufactured, for example, by vapour deposition.
A particularly compact radiation detection device which, moreover, offers a high radiation detection efficïency is characterized in that the resistance layer at the same time forms the entrance window of the radia-tion detection device. Because the window 2 and the space 21 are omitted, radiation 3 entering the ionization L!322 26.10.70 8 PHD 77-126 chamber detector 4 will have been attenuated to a small degree`ol~ly.
Preferably, the end faces 16 and 15 of the high-voltage electrode 5 and the collector electrode 6, respec-tively, are electrically conductively connected to theauxiliary electrode 19 by means of an electrically conduc-tive adhesive (not shown in the Figures), so that vibra-tions are additionally attenuated during operation.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A radiation detection device comprising:
a housing;
an entrance window in the housing; and an ionization chamber detector in the housing which comprises:
a high voltage electrode which is directed trans-verse to the entrance window;
a collector electrode which is substantially parallel to the high voltage electrode and spaced therefrom, such that radiation entering the housing through the entrance window passes between the electrodes;
an ionizible gas between the electrodes;
a high voltage source having two output terminals, one output terminal being electrically connected to the high voltage electrode;
current measuring means having two terminals, one terminal being electrically connected to the other output terminal of the high voltage source, the other terminal of the current meas-uring means being electrically connected to the collector electrode;
a flat auxiliary electrode situated adjacent and parallel to the entrance window and having a relatively high electrical resistance measured in the direction transverse to the collector electrode, said auxiliary electrode having two ends with one end adjacent the high voltage electrode and the other end adjacent but not directly electrically connected to the collector electrode, said output terminals of said high voltage source being electrically connected to the ends of the auxiliary electrode such that the electric field between the high voltage and PHD. 77-126.
collector electrodes is substantially homogen-eous in the vicinity of the auxiliary elec-trode.
a housing;
an entrance window in the housing; and an ionization chamber detector in the housing which comprises:
a high voltage electrode which is directed trans-verse to the entrance window;
a collector electrode which is substantially parallel to the high voltage electrode and spaced therefrom, such that radiation entering the housing through the entrance window passes between the electrodes;
an ionizible gas between the electrodes;
a high voltage source having two output terminals, one output terminal being electrically connected to the high voltage electrode;
current measuring means having two terminals, one terminal being electrically connected to the other output terminal of the high voltage source, the other terminal of the current meas-uring means being electrically connected to the collector electrode;
a flat auxiliary electrode situated adjacent and parallel to the entrance window and having a relatively high electrical resistance measured in the direction transverse to the collector electrode, said auxiliary electrode having two ends with one end adjacent the high voltage electrode and the other end adjacent but not directly electrically connected to the collector electrode, said output terminals of said high voltage source being electrically connected to the ends of the auxiliary electrode such that the electric field between the high voltage and PHD. 77-126.
collector electrodes is substantially homogen-eous in the vicinity of the auxiliary elec-trode.
2. A radiation detection device as claimed in Claim 1, wherein the high-voltage and collector electrodes are flat plates and wherein the high-voltage electrode has an end face which is adjacent to and electrically connected to the auxiliary electrode.
3. A radiation detection device as claimed in Claim 2, wherein the electrical resistance of the auxiliary elec-trode, is approximately between 108 and 1011 ohms per cen-timeter.
4. A radiation detection device comprising:
a housing;
an entrance window in the housing; and an ionization chamber detector in the housing which comprises:
a high voltage electrode which is directed trans-verse to the entrance window;
a collector electrode which is substantially parallel to the high voltage electrode and spaced therefrom, such that radiation entering the housing through the entrance window passes between the electrodes;
an ionizible gas between the electrodes;
a high voltage source having two output termi-nals, one output terminal being electrically connected to the high voltage electrode;
current measuring means having two terminals, one terminal being electrically connected to the other output terminal of the high voltage source, the other terminal of the current mea-suring means being electrically connected to the collector electrode;
a flat auxiliary electrode situated adjacent and parallel to the entrance window and having two ends with one end adjacent the high voltage electrode and the other end adjacent but not directly electrically connected to the collec-PHD. 77-126.
tor electrode, said output terminals of said high voltage source being electrically con-nected to the ends of the auxiliary electrode such that the electric field between the high voltage and collector electrodes is substan-tially homogeneous in the vicinity of the auxiliary electrode, said auxiliary electrode comprising a meander-shaped resistance track on a flat, electrically insulating support, said resistance track having a relatively high resistance in a direction transverse to the collector electrode and having a relatively low resistance in other directions.
a housing;
an entrance window in the housing; and an ionization chamber detector in the housing which comprises:
a high voltage electrode which is directed trans-verse to the entrance window;
a collector electrode which is substantially parallel to the high voltage electrode and spaced therefrom, such that radiation entering the housing through the entrance window passes between the electrodes;
an ionizible gas between the electrodes;
a high voltage source having two output termi-nals, one output terminal being electrically connected to the high voltage electrode;
current measuring means having two terminals, one terminal being electrically connected to the other output terminal of the high voltage source, the other terminal of the current mea-suring means being electrically connected to the collector electrode;
a flat auxiliary electrode situated adjacent and parallel to the entrance window and having two ends with one end adjacent the high voltage electrode and the other end adjacent but not directly electrically connected to the collec-PHD. 77-126.
tor electrode, said output terminals of said high voltage source being electrically con-nected to the ends of the auxiliary electrode such that the electric field between the high voltage and collector electrodes is substan-tially homogeneous in the vicinity of the auxiliary electrode, said auxiliary electrode comprising a meander-shaped resistance track on a flat, electrically insulating support, said resistance track having a relatively high resistance in a direction transverse to the collector electrode and having a relatively low resistance in other directions.
5. A radiation detection device as claimed in Claim 4, wherein the relatively high resistance portions of the resistance track has a resistance of approximately between 108 and 1011 ohms per centimeter.
6. A radiation detection device as claimed in Claim 3 or 5, wherein the auxiliary electrode also forms the entrance window.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000315183A CA1121922A (en) | 1978-10-31 | 1978-10-31 | Radiation detection device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000315183A CA1121922A (en) | 1978-10-31 | 1978-10-31 | Radiation detection device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1121922A true CA1121922A (en) | 1982-04-13 |
Family
ID=4112807
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000315183A Expired CA1121922A (en) | 1978-10-31 | 1978-10-31 | Radiation detection device |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1121922A (en) |
-
1978
- 1978-10-31 CA CA000315183A patent/CA1121922A/en not_active Expired
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