CA1219971A - Blast wave densitometer system - Google Patents
Blast wave densitometer systemInfo
- Publication number
- CA1219971A CA1219971A CA000485427A CA485427A CA1219971A CA 1219971 A CA1219971 A CA 1219971A CA 000485427 A CA000485427 A CA 000485427A CA 485427 A CA485427 A CA 485427A CA 1219971 A CA1219971 A CA 1219971A
- Authority
- CA
- Canada
- Prior art keywords
- scintillator
- housing
- photomultiplier tube
- densitometer
- source
- 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
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)
- Measurement Of Radiation (AREA)
Abstract
ABSTRACT
A beta-attenuation densitometer is disclosed. The densitometer includes a source of beta radiation and a beta detector arranged to receive radiation from the source. The detector includes a scintillator that is caused to fluoresce by the radiation and a photomultiplier tube that detects the light emitted by the scintillator. The scintillator and photomultiplier are contained within a light-tight housing. Shock absorbing potting material protects the tube against damage.
A beta-attenuation densitometer is disclosed. The densitometer includes a source of beta radiation and a beta detector arranged to receive radiation from the source. The detector includes a scintillator that is caused to fluoresce by the radiation and a photomultiplier tube that detects the light emitted by the scintillator. The scintillator and photomultiplier are contained within a light-tight housing. Shock absorbing potting material protects the tube against damage.
Description
7~
The present invention relates to densitometers and more particularly to densitometers using the beta attenuation technique and suitable for measuring density in shock waves.
In a beta attenuation densitometer~ a shock wave to be measured is passed between a radioactive source and a detector.
The increase in density in the shock wave causes a decrease in the amount of radiation reaching the radiation detector. The detected radiation is converted to light in a scintillator crystal, and the light is converted to an electrical signal in a photomultiplier, 0 the electrical signal becoming the system output.
Existing densitometers of the type in question have some deficiencies for use in high pressure shock waves because of the severe conditions encountered~ The present invention aims at the peovision of an improved densitometer for use in exceptionally severe conditions, including overpressures of up to 1040 kPa.
According to the present invention there is provided a densitometer comprising:
a source of beta radiation; and a detector including 'U a) a housing spaced from the source of beta eadiation;
b~ a scintillator mounted in the housing to receive radiation from the beta radiation source;
c) a light seal over the scintillator for preventing ambient light from entering the scintillator while 37~
assing beta radiation from the source to the scintillator;
d) a photomultiplier tube in the housing to receive light emitted by the scintillator, the photomultiplier tube having electrical connection pins thereon;
e) electrical means mounted on the pins of the photomultiplier tube; and f) an elastomeric potting compound, opaque to ambient light, securing the photomultiplier tube and the electrical means in the housing with the tube out of contact with the housing.
The isolation of the photomultiplier tube from the housing through the medium of an elastomeric potting compound significantly improves the shock resistance of the densitomer. In ~referred embodiments, the housing is also mounted with an elastomeric shock mounting.
In preferred embodiments~ improvements are provided in the light seal, the geometry of the radiation source and electeomagnetic shielding.
Because the output of the photomultiplier is non-linear, the ~referred embodiment also includes a non-linear amplifier that eompensates for the non-linearity and produces a densitometer output that is linear with respect to the density being measured.
In the accompanying drawings, which illustrate exemplary embodiments of the present invention:
Figure 1 is a schematic diagram, partially in cross section, of one embodiment of the present densitometer mounted in a blast gauge;
3gl7~
Figure 2 is an elevation, partially in cross section, of an alternative embodiment ofthe densitometer; and Figure 3 is anexploded view of an alternative light seal assembly.
Turning to the drawings, and most particularly to Figure 1, there is illustrated a densitometer 10 mounted in a blast gauge 12. The blast gauge has a central passage 14 through which a shock wave 16 is propagated. On one side of the passage 14 is a radioactive source of beta radiation 18. On the opposite side of 0 the passage is a beta detector 20. The detector 20 includes a housing 22 with a top section 24 and a bottom section 26. The top section 24 contains a scintillator 26 that confronts the radioactive source 18 so that beta radiation emitted from the source 18 impinges on the scintillator 26. The scintillator is equipped with a light seal 28 to prevent its activation by ambient light. In this embodiment, the light seal 28 is an aluminized mylar film adhered to the surface of the scintillator 26. The film is covered with a thin coat o black paint and an acrylic material to provide several layers which may be abraded away ~ef~re the mylar light shield is damaged. This is particulary useful under dusty conditions.
The beta radiation entering the scintillator 26 causes the scintillator to fluoresce. The visible light emitted by the scintillator is passed into a photomultiplier tube 30 mounted in the housing adjacent the scintillator. The photomultiplier tube converts the light into electrical energy. The illustrated tube in this embodiment is a KM2946 wi~h a glass envelope 32 and connector pins 34 mounted directly on the envelope. The low noise resistors 36 that make up a dynode divider chain are directly soldered to the pins 34. The leads from the dynode chain are "Mil-Crimped" to provide strain relief.
The bottom end of the tube 30 is potted in the lower housing part 26 with an elastomeric potting compound 38. This provides a shock resistant mounting for the tube in the housing.
The elastomer is opaque to prevent light leakage through the elastomer into the tube. At the upper end of the tube is an O-ring 40 that aligns the tube in the upper part of the housing 24. The O-ring 40 also provides a closed chamber bounded by the tube, the housing and the scintillator 26 that is filled with a hiyh viscosity optical coupling fluid that provides both optimum liyht transmission as well as vibration isolation from the scintillator.
The tube 30 is surrounded by an electromagnetic shield 44.
The housing 20 has an opening 46 adjacent the bottom through which the leads 48 Erom the tube pass. The leads go to a sigll~l conditioning circuit 50 that is non-linear to match the non-linearity of the tube output with respect to density in the passage 14, thus yielding a linear output 52.
An alternative embodiment of the detector, designated 60, is illustrated in Figure 2. The scintillator 62 is removably mounted on the housing 70 by means of a scintillator ring 64 fastened to the top of the housing by machine screws (not illustrated). O-ring seals 66 and 68 ensure a light tight seal between the scintillator, the scintillator ring 64 and the housing 70. The housing 70 i$ in this embodiment made in one part, generally in the configuration of a tube with a bottom co~er 72 The scintillator ring 64 and the housing 70 are equipped with O-ring grooves 74 in their outer surfaces. These accommodate resilient O-rings for mounting the housing, for example in a blast gauge. The electromagnetic shield in this embodiment is a thicker cylinder of high permeability shielding material to provide an improved magnetic shielding capability for certain applications.
The photomultiplier tube 78 is mounted in the housing in the same way as in the embodiment of Figure 1.
Figure 3 illustrates an alternative form of light seal for use in the embodiment of Figure 2. In this embodiment, the scintillator and scintillator ring assemblies are replaced with an alternative assembly that accommodates a metal foil light seal.
As illustrated in the drawing, the assembly 80 includes a scintillator ring 82 with an O-riny groove 84 in its bottom surface to accommodate an O-ring 86. The peripheral surface of the ring 82 is at 88 to accommodate an O-ring 90 analgous to the ring 66 of the embodiment of Figure 2. The ring 82 has a stepped internal bore 92 that accommodates a scintillator 94 with a similarly stepped outer periphery shape. A metal foil light seal 96 is positioned over the scintillator 94~ A gasket 98 engages the top surface of the foil 96 around its periphery to seal the foil against the underside of a ring cover 100. The ring cover 100 is sealed to the scintillator ring 82 by an internal O-ring 102. The complete assembly is held in place on the detectors by two cap screws 104 and 106.
7~
In an alternative embodiment of the detector, not illustrated in the accompanying drawings, the light seal is a vacuum deposited metal layer on the surEace of the scintillator.
For such an embodiment, the scintillator must be a hard crystal, while in other embodiments organic scintillators can be used.
The present invention relates to densitometers and more particularly to densitometers using the beta attenuation technique and suitable for measuring density in shock waves.
In a beta attenuation densitometer~ a shock wave to be measured is passed between a radioactive source and a detector.
The increase in density in the shock wave causes a decrease in the amount of radiation reaching the radiation detector. The detected radiation is converted to light in a scintillator crystal, and the light is converted to an electrical signal in a photomultiplier, 0 the electrical signal becoming the system output.
Existing densitometers of the type in question have some deficiencies for use in high pressure shock waves because of the severe conditions encountered~ The present invention aims at the peovision of an improved densitometer for use in exceptionally severe conditions, including overpressures of up to 1040 kPa.
According to the present invention there is provided a densitometer comprising:
a source of beta radiation; and a detector including 'U a) a housing spaced from the source of beta eadiation;
b~ a scintillator mounted in the housing to receive radiation from the beta radiation source;
c) a light seal over the scintillator for preventing ambient light from entering the scintillator while 37~
assing beta radiation from the source to the scintillator;
d) a photomultiplier tube in the housing to receive light emitted by the scintillator, the photomultiplier tube having electrical connection pins thereon;
e) electrical means mounted on the pins of the photomultiplier tube; and f) an elastomeric potting compound, opaque to ambient light, securing the photomultiplier tube and the electrical means in the housing with the tube out of contact with the housing.
The isolation of the photomultiplier tube from the housing through the medium of an elastomeric potting compound significantly improves the shock resistance of the densitomer. In ~referred embodiments, the housing is also mounted with an elastomeric shock mounting.
In preferred embodiments~ improvements are provided in the light seal, the geometry of the radiation source and electeomagnetic shielding.
Because the output of the photomultiplier is non-linear, the ~referred embodiment also includes a non-linear amplifier that eompensates for the non-linearity and produces a densitometer output that is linear with respect to the density being measured.
In the accompanying drawings, which illustrate exemplary embodiments of the present invention:
Figure 1 is a schematic diagram, partially in cross section, of one embodiment of the present densitometer mounted in a blast gauge;
3gl7~
Figure 2 is an elevation, partially in cross section, of an alternative embodiment ofthe densitometer; and Figure 3 is anexploded view of an alternative light seal assembly.
Turning to the drawings, and most particularly to Figure 1, there is illustrated a densitometer 10 mounted in a blast gauge 12. The blast gauge has a central passage 14 through which a shock wave 16 is propagated. On one side of the passage 14 is a radioactive source of beta radiation 18. On the opposite side of 0 the passage is a beta detector 20. The detector 20 includes a housing 22 with a top section 24 and a bottom section 26. The top section 24 contains a scintillator 26 that confronts the radioactive source 18 so that beta radiation emitted from the source 18 impinges on the scintillator 26. The scintillator is equipped with a light seal 28 to prevent its activation by ambient light. In this embodiment, the light seal 28 is an aluminized mylar film adhered to the surface of the scintillator 26. The film is covered with a thin coat o black paint and an acrylic material to provide several layers which may be abraded away ~ef~re the mylar light shield is damaged. This is particulary useful under dusty conditions.
The beta radiation entering the scintillator 26 causes the scintillator to fluoresce. The visible light emitted by the scintillator is passed into a photomultiplier tube 30 mounted in the housing adjacent the scintillator. The photomultiplier tube converts the light into electrical energy. The illustrated tube in this embodiment is a KM2946 wi~h a glass envelope 32 and connector pins 34 mounted directly on the envelope. The low noise resistors 36 that make up a dynode divider chain are directly soldered to the pins 34. The leads from the dynode chain are "Mil-Crimped" to provide strain relief.
The bottom end of the tube 30 is potted in the lower housing part 26 with an elastomeric potting compound 38. This provides a shock resistant mounting for the tube in the housing.
The elastomer is opaque to prevent light leakage through the elastomer into the tube. At the upper end of the tube is an O-ring 40 that aligns the tube in the upper part of the housing 24. The O-ring 40 also provides a closed chamber bounded by the tube, the housing and the scintillator 26 that is filled with a hiyh viscosity optical coupling fluid that provides both optimum liyht transmission as well as vibration isolation from the scintillator.
The tube 30 is surrounded by an electromagnetic shield 44.
The housing 20 has an opening 46 adjacent the bottom through which the leads 48 Erom the tube pass. The leads go to a sigll~l conditioning circuit 50 that is non-linear to match the non-linearity of the tube output with respect to density in the passage 14, thus yielding a linear output 52.
An alternative embodiment of the detector, designated 60, is illustrated in Figure 2. The scintillator 62 is removably mounted on the housing 70 by means of a scintillator ring 64 fastened to the top of the housing by machine screws (not illustrated). O-ring seals 66 and 68 ensure a light tight seal between the scintillator, the scintillator ring 64 and the housing 70. The housing 70 i$ in this embodiment made in one part, generally in the configuration of a tube with a bottom co~er 72 The scintillator ring 64 and the housing 70 are equipped with O-ring grooves 74 in their outer surfaces. These accommodate resilient O-rings for mounting the housing, for example in a blast gauge. The electromagnetic shield in this embodiment is a thicker cylinder of high permeability shielding material to provide an improved magnetic shielding capability for certain applications.
The photomultiplier tube 78 is mounted in the housing in the same way as in the embodiment of Figure 1.
Figure 3 illustrates an alternative form of light seal for use in the embodiment of Figure 2. In this embodiment, the scintillator and scintillator ring assemblies are replaced with an alternative assembly that accommodates a metal foil light seal.
As illustrated in the drawing, the assembly 80 includes a scintillator ring 82 with an O-riny groove 84 in its bottom surface to accommodate an O-ring 86. The peripheral surface of the ring 82 is at 88 to accommodate an O-ring 90 analgous to the ring 66 of the embodiment of Figure 2. The ring 82 has a stepped internal bore 92 that accommodates a scintillator 94 with a similarly stepped outer periphery shape. A metal foil light seal 96 is positioned over the scintillator 94~ A gasket 98 engages the top surface of the foil 96 around its periphery to seal the foil against the underside of a ring cover 100. The ring cover 100 is sealed to the scintillator ring 82 by an internal O-ring 102. The complete assembly is held in place on the detectors by two cap screws 104 and 106.
7~
In an alternative embodiment of the detector, not illustrated in the accompanying drawings, the light seal is a vacuum deposited metal layer on the surEace of the scintillator.
For such an embodiment, the scintillator must be a hard crystal, while in other embodiments organic scintillators can be used.
Claims (9)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A densitometer comprising:
a source of beta radiation; and a detector including a) a housing spaced from the source of beta radiation;
b) a scintillator mounted in the housing to receive radiation from the beta radiation source;
c) a light seal over the scintillator for preventing ambient light from entering the scintillator while passing beta radiation from the source in the scintillator;
d) a photomultiplier tube in the housing to receive light emitted by the scintillator, the photomultiplier tube having electrical connection pins thereon;
e) electrical means mounted on the pins of the photomultiplier tube; and f) an elastomeric potting compound, opaque to ambient light, securing the photomultiplier tube and the electrical means in the housing with the tube out of contact with the housing.
a source of beta radiation; and a detector including a) a housing spaced from the source of beta radiation;
b) a scintillator mounted in the housing to receive radiation from the beta radiation source;
c) a light seal over the scintillator for preventing ambient light from entering the scintillator while passing beta radiation from the source in the scintillator;
d) a photomultiplier tube in the housing to receive light emitted by the scintillator, the photomultiplier tube having electrical connection pins thereon;
e) electrical means mounted on the pins of the photomultiplier tube; and f) an elastomeric potting compound, opaque to ambient light, securing the photomultiplier tube and the electrical means in the housing with the tube out of contact with the housing.
2. A densitometer according to claim 1, further including an electromagnetic shield surrounding the photomultiplier tube, within the housing.
3. A densitometer according to claim 1, wherein the scintillator and the radiation source are substantially circular.
4. A densitometer according to claim 1, wherein the scintillator comprises europium activated calcium flouride.
5. A densitometer according to claim 1, including elastomeric means for mounting the housing in a gage.
6. A densitometer according to claim 1, wherein the photomultiplier tube includes a glass envelope with connecting pins secured directly to the envelope.
7. A densitometer accordiing to claim 1, further including a non-linear amplifier external to said housing and having an input connected to said photomultiplier tube and an output, the characteristics of the amplifier being such that the amplier output is a linear function of the amount of beta radiation reaching scintilator from the source of beta radiation.
8. A densitometer according to claim 1, wherein the light seal comprises an aluminized mylar film adhered to the scintilator.
9. A densitometer according to claim 1, wherein the light seal comprises a layer of metal vacuum deposits on to the surface of the scintilator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000485427A CA1219971A (en) | 1985-06-26 | 1985-06-26 | Blast wave densitometer system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000485427A CA1219971A (en) | 1985-06-26 | 1985-06-26 | Blast wave densitometer system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1219971A true CA1219971A (en) | 1987-03-31 |
Family
ID=4130843
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000485427A Expired CA1219971A (en) | 1985-06-26 | 1985-06-26 | Blast wave densitometer system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1219971A (en) |
-
1985
- 1985-06-26 CA CA000485427A patent/CA1219971A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |