CA1078974A - Economic solid state alpha detector for monitoring radon gas and its daughter products - Google Patents
Economic solid state alpha detector for monitoring radon gas and its daughter productsInfo
- Publication number
- CA1078974A CA1078974A CA292,152A CA292152A CA1078974A CA 1078974 A CA1078974 A CA 1078974A CA 292152 A CA292152 A CA 292152A CA 1078974 A CA1078974 A CA 1078974A
- Authority
- CA
- Canada
- Prior art keywords
- phosphor
- light
- solid state
- radon
- alpha
- 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.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/20—Measuring radiation intensity with scintillation detectors
- G01T1/2018—Scintillation-photodiode combinations
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- High Energy & Nuclear Physics (AREA)
- Molecular Biology (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Photometry And Measurement Of Optical Pulse Characteristics (AREA)
Abstract
Abstract In the detection of Radon gas it is common for the radon sample to be admitted to a dark chamber the sides of which are coated with a 'phosphor' (silver activated zinc sulphide or equivalent).
the resultant light flashes(caused by the alpha emanation striking the 'phosphor') are then counted by a highly sensitive light detector such as a photo multiplier tube. The auxiliary circuitry for the photo multiplier tube is expensive, there is a problem of the phosphor being contaminated by build up of Radon daughters and a problem of light contamination in changing chambers in the field .
In this invention, a less sensitive but economical solid state optical sensor is used and an increase in sensitivity obtained by depositing the 'phosphor' directly upon the optical detector. This may then be sealed with a thin metallic deposit that is opaque to light but semi transparent to alpha emanation. The reduced sensit-ivity due to reduced surface area may be compensated for by longer periods of observation.
the resultant light flashes(caused by the alpha emanation striking the 'phosphor') are then counted by a highly sensitive light detector such as a photo multiplier tube. The auxiliary circuitry for the photo multiplier tube is expensive, there is a problem of the phosphor being contaminated by build up of Radon daughters and a problem of light contamination in changing chambers in the field .
In this invention, a less sensitive but economical solid state optical sensor is used and an increase in sensitivity obtained by depositing the 'phosphor' directly upon the optical detector. This may then be sealed with a thin metallic deposit that is opaque to light but semi transparent to alpha emanation. The reduced sensit-ivity due to reduced surface area may be compensated for by longer periods of observation.
Description
107897~ Richard Brancker Research Ltd ECONOMIC SOLID STATE ALP~A DETECTOR FOR MONITORING
RADO~ GAS AND I~S_DAUGH~ER PRODUC~S _ Specification ~his invention relates to an econimical device for detecting alpha emanation from Radon ga~ and its daughter products.
It is common in the detection of Radon gas (Rn 222 or Rn 220) for the sample to be admitted to a dark chamber, the sides of which are coated with Silver activated Zinc Sulphide (or an equivalent 'phosphor') with the resultant 'light flashes' (produced as the alpha emanations from the radon gas strike the phosphor) being counted by a sensitive optical detector such as a photo multiplier tube.
In the above it is advantageous to use as lar~e a chamber as possible with respect to the mean free path of alpha in air so as to contain as much radon as possible (usually 4 to 5 cm in diameter). In order to detect weak light flashes at the extremities the optical detector has to be very sensitive and is usually of necessity a photo multiplier tube. The photo multiplier tube, though considerably more sensative than a solid state optical de~ector, requires expensive auxilliary circuitry in the form of a stable high voltage supply, overload protection circuitry, etc.
Specification page 1 of 3 ' .
; ' i~ ~897'~ Richard Brancker Research Ltd.
The second disadvantage of the current method is that the chamber must at all times be kept 'dark' since light also activates the 'phosphori and the activity due to exposure to light may take some 5 to 20 minutes to decay to a useable background. In certain field instruments where the chamber has to be periodically changed due to radon daughter contam-ination, this can prove a maJor problem.
I believe that it is possible to achieve reasonable sensitivity with a simple solid state optical detector such as a photo diode providing the 'phosphori (Silver activated Zinc Sulphide) is deposited as a thin layer directly upon the optical detector.
~he effects of light may now also be overcome by adding a thin metalic deposit over this layer of 'phosphor'. ~his metallic layer will be transparent to alpha emanations and yet opaque to light.
In general therefore the invention consists of taking a standard photo-diode (or other optical sensor) and depositing upon its surface a thin layer of silver activated zinc sulphide and in turn depositing upon this a thin metalic coating of a thickness aust sufficient to satisfactorily inhibit the entry of light.
Specification page 2 of 3 - , ;
-~
RADO~ GAS AND I~S_DAUGH~ER PRODUC~S _ Specification ~his invention relates to an econimical device for detecting alpha emanation from Radon ga~ and its daughter products.
It is common in the detection of Radon gas (Rn 222 or Rn 220) for the sample to be admitted to a dark chamber, the sides of which are coated with Silver activated Zinc Sulphide (or an equivalent 'phosphor') with the resultant 'light flashes' (produced as the alpha emanations from the radon gas strike the phosphor) being counted by a sensitive optical detector such as a photo multiplier tube.
In the above it is advantageous to use as lar~e a chamber as possible with respect to the mean free path of alpha in air so as to contain as much radon as possible (usually 4 to 5 cm in diameter). In order to detect weak light flashes at the extremities the optical detector has to be very sensitive and is usually of necessity a photo multiplier tube. The photo multiplier tube, though considerably more sensative than a solid state optical de~ector, requires expensive auxilliary circuitry in the form of a stable high voltage supply, overload protection circuitry, etc.
Specification page 1 of 3 ' .
; ' i~ ~897'~ Richard Brancker Research Ltd.
The second disadvantage of the current method is that the chamber must at all times be kept 'dark' since light also activates the 'phosphori and the activity due to exposure to light may take some 5 to 20 minutes to decay to a useable background. In certain field instruments where the chamber has to be periodically changed due to radon daughter contam-ination, this can prove a maJor problem.
I believe that it is possible to achieve reasonable sensitivity with a simple solid state optical detector such as a photo diode providing the 'phosphori (Silver activated Zinc Sulphide) is deposited as a thin layer directly upon the optical detector.
~he effects of light may now also be overcome by adding a thin metalic deposit over this layer of 'phosphor'. ~his metallic layer will be transparent to alpha emanations and yet opaque to light.
In general therefore the invention consists of taking a standard photo-diode (or other optical sensor) and depositing upon its surface a thin layer of silver activated zinc sulphide and in turn depositing upon this a thin metalic coating of a thickness aust sufficient to satisfactorily inhibit the entry of light.
Specification page 2 of 3 - , ;
-~
Claims
Claim 1, the only claim on file is hereby amended to read as follows:-1. A photosensitive device such as a photodiode upon the surface of which a thin layer of alpha sensitive phosphor such as silver activated zinc sulphide is deposited, and that a thin metallic deposit is in turn provided upon this thin layer of phosphor, with the result that the phosphor is sealed from light.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA292,152A CA1078974A (en) | 1977-12-01 | 1977-12-01 | Economic solid state alpha detector for monitoring radon gas and its daughter products |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA292,152A CA1078974A (en) | 1977-12-01 | 1977-12-01 | Economic solid state alpha detector for monitoring radon gas and its daughter products |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078974A true CA1078974A (en) | 1980-06-03 |
Family
ID=4110189
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA292,152A Expired CA1078974A (en) | 1977-12-01 | 1977-12-01 | Economic solid state alpha detector for monitoring radon gas and its daughter products |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1078974A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6897448B2 (en) * | 2002-08-29 | 2005-05-24 | Kno-Rad, Inc. | Radiation detector |
-
1977
- 1977-12-01 CA CA292,152A patent/CA1078974A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6897448B2 (en) * | 2002-08-29 | 2005-05-24 | Kno-Rad, Inc. | Radiation detector |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |