Compact detector for radon and radon daughter products

Abstract

A compact low cost track registration detector for radon gas and radon daughter products includes a housing with a removable closure cap for retaining a strip of track registration material having the property of forming damage tracks along paths traversed by alpha particles. The strip is retained within the housing by integrally formed upstanding ribs located closely adjacent diametrically opposite inner side wall portions of the housing, a first set of ribs forming a pedestal support and second set of longer ribs providing transverse support. A microporous filter impervious to particles and radon daughter products admits only radon gas to the interior of the housing. The apertured closure cap has a central solid portion providing a radiation shield for the upper surface of the strip to enable the lower exposure surface to be readily distinguished after the detector has been retrieved from an exposure site. The housing is fabricated from a pure polyethylene material free from any residual alpha particle radiation. A flexible strip wrapped about the exterior of the housing affords both a hanging strap and an information sheet for user entry of exposure information.

What is claimed is: .[.1. An improved compact track registration detector for radon gas, said detector comprising: 
     
        means into said housing interior..]. 2. .[.The invention of claim 1.]. .Iadd.An improved compact track registration detector for radon gas, said detector comprising: a housing having an open mouth, a bottom and side walls defining an interior volume;   means for providing longitudinal and lateral support within said housing adjacent the inner side wall surfaces and said mouth;   track registration means supported in the interior of said housing by said support means, said track registration means having the property of forming damage tracks therein along paths traversed by alpha particles;   microporous filter means positioned across the mouth of said housing for preventing entry of radon daughters and particulate matter into said housing interior so that substantially only gases enter said volume;   an apertured cap removably received on the mouth end of said housing for retaining said filter means and said track registration means in place adjacent said mouth,   said housing having internal wall surfaces dimensioned to optimize the registration of alpha particles from radon present in said housing interior and from radon daughter products present in said housing interior which are a result of the decay of radon gas admitted through said filter means into said housing interior; and .Iaddend.   wherein said support means comprises a first plurality of upstanding ribs each terminating in an upper support surface and a second plurality of upstanding ribs flanking said first plurality of ribs and each terminating   
     
     
        in an upper surface located above said upper support surface. 3. The invention of claim 2 wherein said ribs are integrally formed with said 
     
     
        housing. 4. .[.The invention of claim 1.]. .Iadd.An improved compact track registration detector for radon gas, said detector comprising: a housing having an open mouth, a bottom and side walls defining an interior volume;   means for providing longitudinal and lateral support within said housing adjacent the inner side wall surfaces and said mouth;   track registration means supported in the interior of said housing by said support means, said track registration means having the property of forming damage tracks therein along paths traversed by alpha particles;   microporous filter means positioned across the mouth of said housing for preventing entry of radon daughters and particulate matter into said housing interior so that substantially only gases enter said volume;   an apertured cap removably received on the mouth end of said housing for retaining said filter means and said track registration means in place adjacent said mouth,   said housing having internal wall surfaces dimensioned to optimize the registration of alpha particles from radon present in said housing interior and from radon daughter products present in said housing interior which are a result of the decay of radon gas admitted through said filter means into said housing interior; and .Iaddend.   wherein said apertured cap includes a solid central portion providing a radiation shield for the top surface of said track registration material to enable the exposed bottom surface of said track registration material   
     
     
        to be easily distinguished after exposure. 5. The invention of claim .[.1.]. .Iadd.4 .Iaddend.wherein said housing is fabricated from a 
     
     
        material substantially devoid of alpha emitting substances. 6. The 
     
     
        invention of claim 5 wherein said housing material is polyethylene. 7. .[.The invention of claim 1.]. .Iadd.An improved compact track registration detector for radon gas, said detector comprising: a housing having an open mouth, a bottom and side walls defining an interior volume;   means for providing longitudinal and lateral support within said housing adjacent the inner side wall surfaces and said mouth;   track registration means supported in the interior of said housing by said support means, said track registration means having the property of forming damage tracks therein along paths traversed by alpha particles;   microporous filter means positioned across the mouth of said housing for preventing entry of radon daughters and particulate matter into said housing interior so that substantially only gases enter said volume;   an apertured cap removably received on the mouth end of said housing for retaining said filter means and said track registration means in place adjacent said mouth,   said housing having internal wall surfaces dimensioned to optimize the registration of alpha particles from radon present in said housing interior and from radon daughter products present in said housing interior which are a result of the decay of radon gas admitted through said filter means into said housing interior; and .Iaddend.   wherein said filter means comprises a water repellent embossed laminate of microporous polypropylene material having a pore volume of about forty-five percent with pore sizes of about 0.04 by about 0.20 micrometer   
     
     
        and a thickness of about 200 micrometers. 8. .[.The invention of claim 1.]. .Iadd.An improved compact track registration detector for radon gas, said detector comprising: a housing having an open mouth, a bottom and side walls defining an interior volume;   means for providing longitudinal and lateral support within said housing adjacent the inner side wall surfaces and said mouth;   track registration means supported in the interior of said housing by said support means, said track registration means having the property of forming damage tracks therein along paths traversed by alpha particles;   microporous filter means positioned across the mouth of said housing for preventing entry of radon daughters and particulate matter into said housing interior so that substantially only gases enter said volume;   an apertured cap removably received on the mouth end of said housing for retaining said filter means and said track registration means in place adjacent said mouth,   said housing having internal wall surfaces dimensioned to optimize the registration of alpha particles from radon present in said housing interior and from radon daughter products present in said housing which are a result of the decay of radon gas admitted through said filter means into said housing interior; and .Iaddend.   wherein said track registration material comprises a strip of solid material having an alpha particle sensitivity range with an upper limit of   
     
     
        about 8 MEV. 9. The invention of claim 8 wherein said material has an 
     
     
        alpha particle sensitivity range with a lower limit of about 0.1 MEV. 10. A compact track registration detector for radon gas, said detector comprising: a housing having a removable closure cap for retaining a strip of track registration material having the property of forming damage tracks therein along paths traversed by alpha particles;   a microporous filter means for preventing entry into the interior of said housing of radon daughters and particulate matter so that substantially only gases enter the interior volume of said housing; and   a flexible mounting/indicia strip normally wrapped about the exterior of said housing for enabling said detector to be removably attached to a mounting surface, said strip having surface regions arranged to enable predetermined information to be recorded thereon serving to identify   
     
     
        predetermined exposure information. 11. The invention of claim 10 wherein said housing has an open mouth, a bottom and side walls defining said interior volume, and means for providing longitudinal and lateral support 
     
     
        in said interior volume adjacent the inner side wall surfaces. 12. The invention of claim 11 wherein said support means comprises a first plurality of upstanding ribs each terminating in an upper support surface and a second plurality of upstanding ribs flanking said first plurality of ribs and each terminating in an upper surface located above said upper 
     
     
        support surface. 13. The invention of claim 12 wherein said ribs are 
     
     
        integrally formed with said housing. 14. The invention of claim 10 wherein said enclosure cap includes a solid central portion providing a radiation shield for the top surface of said track registration material to enable the exposed bottom surface of said track registration material to be 
     
     
        easily distinguished after exposure. 15. The invention of claim 10 wherein said housing is fabricated from a material substantially devoid of alpha 
     
     
        emitting substances. 16. The invention of claim 15 wherein said housing 
     
     
        material is polyethylene. 17. The invention of claim 10 wherein said filter means comprises a water repellent embossed laminate of microporous polypropylene material having a pore volume of about forty-five percent, with pore sizes of about 0.04 by about 0.20 micrometer and a thickness of 
     
     
        about 200 micrometers. 18. The invention of claim 10 wherein said track registration material comprises a strip of solid material having an alpha 
     
     
        particle sensitivity range with an upper limit of about 8 MEV. 19. The invention of claim 18 wherein said track registration material has an alpha particle sensitivity range with a lower limit of about 0.1 MEV. 
     
     
        .Iadd.20.  A compact track registration detector for radon gas comprising: a housing including an open mouth and enclosing walls defining an interior volume: a track registration element supported at said mouth within said interior volume and comprising a material having the property of forming damage tracks along paths traversed by alpha particles impacting a registration surface formed on said track registration element, a microporous filter means positioned across said mouth of said housing above and next to said registration element for preventing entry of radon daughter products and other particulate matter into the interior volume of said housing so that substantially only gases enter into said interior volume; and support means including an apertured cap on said housing orienting said track registration surface in relation to said filter means and mouth such that the directional exposure of said surface allows detectable, permanent damage tracks thereon substantially only of alpha particles originating from gases passing through said filter means into said interior volume and from decay products of such gases deposited therein, while substantially excluding damage tracks detectable at said surface by alpha particles emitted from locations on a side of said track registration element opposite said registration surface. .Iaddend. 
     
     
        .Iadd.  .  The detector according to claim 20 wherein said track registration surface is directed away from said filter means in order to prevent exposure of said registration surface to alpha particles reaching said surface which have not originated from said gases and decay products 
     
     
        thereof. .Iaddend. .Iadd.22.  The detector according to claim 20, wherein said apertured cap is removably received on the mouth of said housing for retaining said filter means and said track registration means in place 
     
     
        adjacent said mouth. .Iaddend. .Iadd.23.  A compact track registration detector for radon gas comprising: a housing including an open mouth and enclosing walls defining an interior volume: a track registration element supported adjacent said mouth within said interior volume and comprising a material having the property of forming damage tracks along paths traversed by alpha particles impacting a registration surface formed on said track registration element, a microporous filter means positioned across said mouth of said housing above said registration element for preventing entry of radon daughter products and other particulate matter into the interior volume of said housing so that substantially only gases enter into said interior volume; and support means orienting said track registration surface in relation to said filter means and mouth such that the directional exposure of said surface allows detectable, permanent damage tracks thereon substantially only of alpha particles originating from gases passing through said filter means into said interior volume and from decay products of such gases deposited therein and means shielding a second surface of said element opposite from said registration surface for substantially excluding damage tracks on said second surface by alpha particles emitted from locations on a side of said track registration element opposite said registration surface. .Iaddend.