DE102011085943A1 - Scintillation detector for radiometric measuring device, has retroreflection unit that is arranged in end of fiber bundle to perform retroreflection of incident light back to scintillation fiber bundles - Google Patents

Abstract

The detector has scintillation fibers (13) which are provided with scintillation fiber bundles (11). Gamma radiation incident on scintillation fibers is converted into light pulses which propagate to end of scintillation fiber bundles. The end (17) of scintillation fiber bundle is attached to photoelectric transducer which converts light incident to it into electric signal. A retroreflection unit (23) arranged in end (21) of fiber bundle performs retroreflection of incident light back to scintillation fiber bundles. An independent claim is included for radiometric measuring device.

Description

The invention relates to a scintillation detector for a radiometric measuring device for measuring a measured variable, in particular a measuring device for measuring a filling level or a density of a filling material in a container, and / or for monitoring an exceeding or falling below a predetermined limit value for the measured variable a scintillation fiber bundle composed of scintillation fibers, in which radioactive radiation incident on scintillation fibers in the respective scintillation fiber is converted into flashes of light propagating to the ends thereof in the respective scintillation fiber and a photoelectric transducer connected to a first end of the scintillation fiber bundle; Converts light into an electrical signal corresponding to a radiation intensity incident on the scintillation fiber bundle.

Radiometric measuring instruments are usually used whenever conventional measuring instruments can not be used due to particularly rough conditions at the measuring location. Very often z. B. at the site extremely high temperatures and pressures or there are chemically and / or mechanically very aggressive environmental influences that make the use of other measurement methods impossible.

They regularly comprise a radioactive emitter which in operation emits radioactive radiation through the container, and a detector arranged on a side of the container opposite the emitter, which serves to receive a radiation intensity which is dependent on the measurand and passes through the container Convert signal.

Scintillation detectors with a solid, rigid scintillation bar are used today as a detector, at one end of which a photoelectric converter, eg. B. a photomultiplier is connected. The scintillation bar is made of a special plastic, such. As polystyrene (PS) or polyvinyltoluene (PVT), which is optically very pure. Gamma radiation triggers light flashes in the scintillation material whose light is detected by the photomultiplier and converted into electrical impulses. An electronic measuring device is connected to the photomultiplier, which uses the electrical impulses to determine a pulse rate at which the impulses occur. The pulse rate is dependent on the radiation intensity and thus a measure of the measured variable to be determined.

Today scintillation detectors with massive rigid scintillation rods are already in use, in which the free end of the scintillation rod is covered with a planar mirror to increase the light yield. However, since the light impinges on the mirror at different angles, a small portion of the light reflected by the mirror still exits the scintillation bar on the outside, despite the mirror.

In addition, detectors are known in which combined instead of massive Szinitillationsstäben to a Szintillationsfaserbündel scintillation fibers are used. The scintillation fiber bundles are also connected at one end to a photoelectric converter.

A radiometric level gauge with a scintillation detector having a scintillation detector is, for example, in the European patent EP-B 1 068 494 described.

The advantage of these detectors is that scintillation fiber bundles, in contrast to rigid scintillation rods, are flexible, and thus can be optimally adapted in their shape to the spatial conditions both during transport and at the place of use.

However, scintillation fiber bundles have a lower density overall than solid scintillation rods because of the interstices between the individual fibers. Accordingly, the sensitivity of these detectors, which is essentially determined by the total mass of the scintillator material, is lower in these detectors than in detectors with scintillation bars.

Another disadvantage is that only the portion of the light can be detected by measurement, which propagates in the interior of the scintillation fibers in the direction of the photoelectric converter, while emerging in the opposite direction portion of the scintillation light escapes from the fiber ends.

For both scintillation detector types, the light which does not reach the photoelectric converter can not be detected by measurement, and thus leads to a reduction of the sensitivity of the scintillation detector.

It is an object of the invention to provide a scintillation detector with higher sensitivity.

• – einem aus Szintillationsfasern bestehenden Szintillationsfaserbündel, in dem auf Szintillationsfasern auftreffende radioaktive Strahlung in der jeweiligen Szintillationsfaser in Lichtblitze umgewandelt wird, deren Licht sich in der jeweiligen Szintillationsfaser zu deren Enden hin ausbreitet,
• – einem an ein erstes Ende des Szintillationsfaserbündels angeschlossenen photo-elektrischen Wandler, der darauf auftreffendes Licht in ein einer auf das Szintillationsfaserbündel auftreffenden Strahlungsintensität entsprechendes elektrisches Signal umwandelt, und
• – einer an einem dem ersten Ende gegenüberliegenden zweiten Ende des Szintillationsfaserbündels endseitig vorgesehenen Retroreflektionseinrichtung, die eine Retroreflektion von über die Szintiallationsfasern darauf auftreffendem Licht in die Szintillationsfasern zurück bewirkt.

For this purpose, the invention comprises a scintillation detector for a radiometric measuring device for measuring a measured variable, in particular a measuring device for measuring a filling level or a density of a filling material in a container, and / or for monitoring an exceeding or falling below a predetermined limit value for the measured variable, With

• A scintillation fiber bundle consisting of scintillation fibers, in which radioactive radiation incident on scintillation fibers in the respective scintillation fiber is converted into flashes of light whose light propagates in the respective scintillation fiber towards their ends,
• A photo-electric converter connected to a first end of the scintillation fiber bundle and converting light incident thereon into an electrical signal corresponding to a radiation intensity impinging on the scintillation fiber bundle, and
• A retroreflecting device provided at the end opposite the second end of the scintillation fiber bundle, which effects a retroreflection of light incident thereon via the scintillation fibers into the scintillation fibers.

According to a first variant of the invention, the retroreflection device covers a front side of the second end of the scintillation fiber bundle in a planar manner.

According to one embodiment of this variant, the retroreflecting device is a microprismatic film applied flat on the front side.

According to a second variant of the invention, the retroreflecting device comprises a number of retroreflectors, corresponding to a number of the scintillation fibers, which are applied to the ends of the scintillation fibers.

According to one embodiment of the second variant, the retroreflectors are triple prisms.

• – einem Szintillationsstab, in dem darauf auftreffende radioaktive Strahlung in Lichtblitze umgewandelt wird, deren Licht sich zu beiden Enden des Szintillationsstabs hin ausbreitet,
• – einem an ein erstes Ende des Szintillationsstabs angeschlossenen photo-elektrischen Wandler, der darauf auftreffendes Licht in ein einer auf den Szinitillationstab auftreffenden Strahlungsintensität entsprechendes elektrisches Signal umwandelt, und
• – einer an einem dem ersten Ende gegenüberliegenden zweiten Ende des Szintillationsstabs endseitig vorgesehenen Retroreflektionseinrichtung, insb. einer Mikroprismenfolie, die eine Retroreflektion von über den Szintiallationsstab darauf auftreffenden Licht in den Szintillationstab zurück bewirkt.

Furthermore, the invention comprises a scintillation detector for a radiometric measuring device for measuring a measured variable, in particular a measuring device for measuring a filling level or a density of a filling material in a container, and / or for monitoring an exceeding or falling below a predetermined limit value for the measured variable, With

• A scintillation bar, in which radioactive radiation incident thereon is converted into flashes of light, the light of which propagates towards both ends of the scintillation bar,
• A photo-electric converter connected to a first end of the scintillation bar and converting light incident thereon into an electrical signal corresponding to a radiation intensity incident on the scintillation bar, and
• A retroreflecting device, in particular a microprismatic foil, provided at a second end of the scintillation rod opposite the first end, which effects a retroreflection of light impinging thereon via the scintillation rod into the scintillation rod.

In addition, the invention comprises a radiometric measuring device for measuring a measured variable, in particular a filling level or a density, of a filling material in a container, and / or for monitoring an exceeding or falling below a predetermined limit value for the measured variable, with a scintillation detector according to the invention.

• – umfasst letzteres einen radioaktiven Strahler, der im Betrieb radioaktive Strahlung durch den Behälter sendet,
• – ist der Szintillationsdetektor auf einer dem Strahler gegenüberliegenden Seite des Behälters angeordnet, und
• – dient der Szintillationsdetektor dazu eine durch den Behälter hindurch dringende von der Messgröße abhängige Strahlungsintensität zu empfangen und in ein elektrisches Ausgangssignal umzuwandeln.

According to one embodiment of the radioactive measuring device

• The latter comprises a radioactive emitter which, during operation, emits radioactive radiation through the container,
• - The scintillation detector is disposed on a side opposite the radiator side of the container, and
• - The scintillation detector is used to receive an urgent through the container dependent on the measured variable radiation intensity and convert it into an electrical output signal.

The invention and further advantages will now be explained in more detail with reference to the figures of the drawing, in which two embodiments are shown; like parts are provided in the figures with the same reference numerals.

1 shows: a radiometric measuring arrangement;

2 1 shows an end of the scintillation fiber bundle covered by a retroreflecting device on the front side 1 ; and

3 1 shows an end provided with a retroreflector end of a scintillation fiber of the scintillation fiber bundle of FIG 1 ,

The invention relates to a scintillation detector for a radiometric measuring device for measuring a measured variable, in particular a fill level or a density of a filling material located in a container and / or for monitoring an exceeding or falling below a predetermined limit value for the measured variable.

1 shows as an example to this a schematic diagram of a level measuring device with a radiometric level gauge. The measuring arrangement comprises one with a product 1 fillable container 3 and one outside the container 3 mounted radioactive emitters 5 , in the measuring operation radioactive radiation through the container 3 sends. The spotlight 5 includes one Radiation protection container into which a radioactive preparation, eg. As a Co ₆₀ or Cs ₁₃₇ preparation is introduced. The radiation protection container has an opening through which the radiation emerges in a direction of radiation predetermined by the orientation of the opening and the container 3 irradiated. On a spotlight 5 opposite side of the container 3 is a partially sectioned view of an embodiment of a scintillation detector according to the invention 7 arranged. The scintillation detector 7 serves to through the container 3 urgent of the measured variable, here the level in the container 3 , Dependent radiation intensity on a application-specific predetermined by the metrological scintillation detector 7 To receive to be detected area and convert it into an incident thereon radiation intensity corresponding electrical signal. The latter is then one of the scintillation detector 7 connected measuring electronics 9 the radiometric measuring device for further evaluation and / or processing available, which determines the measured variable based on the electrical signal.

The scintillation detector 7 comprises a scintillation fiber bundle 11 consisting of individual scintillation fibers combined into a bundle 13 preferably, in a protective tube 15 are introduced. scintillation 13 are for example available with a round cross-section with a diameter of the order of 1 mm or with a rectangular or square cross-section with a cross-sectional area of the order of 1 mm ² . The scintillation fiber bundle 11 is flexible over its entire length and therefore in its shape optimally in the spatial conditions both during transport and at the place of use, here to the container shape, adaptable. Thus, it is esp. In other hard to mount places mountable, and of course much easier to transport compared to Szintillationsstäben comparable length.

On the scintillation fibers 13 incident radioactive radiation is in the respective scintillation fiber 13 converted into flashes of light whose light is in the respective scintillation fiber 13 spread to the ends.

At a first end 17 of the scintillation fiber bundle 11 is a photoelectric converter 19 connected, the incident thereon light in a on the scintillation fiber bundle 11 impinging radiation intensity corresponding electrical signal converts. The photoelectric converter 19 includes, for example, a photomultiplier or photodiodes, in particular an avalanche photodiode operated in Geiger mode in an array. The first end 17 of the scintillation fiber bundle 11 For this purpose, it is preferably polished flat and a coupling fat with low light loss to the photo-electrical converter 19 connected.

According to the invention is at a first end 17 opposite second end 21 of the scintillation fiber bundle 11 at the end a retroreflecting device 23 provided by the Szintiallationsfasern 13 incident light on the scintillation fibers 13 reflects back.

Retroreflectors cause a reflection of light incident thereon, which is largely independent of the orientation of the retroreflector.

Retroreflections can be achieved by plano-optical angle reflectors, such. B. triple mirror or triple prisms, by retro-reflector, such. As carriers with back-mounted thereon triple prisms, by rotationally symmetrical lens reflectors, as provided for example in cat's eyes, or other retroreflective body, such as. B. biconical constructions are effected.

Due to the orientation of the retroreflecting device 23 independent almost complete total reflection of the retroreflector 23 As a result of incident light, the light impinging thereon is almost 100% in the scintillation fibers 13 of the scintillation fiber bundle 11 reflected back. By comparison, the proportion which is reflected back into the scintillation bar in the scintillation rod covered at the end with planar mirrors covered by planar mirrors is only in the region of 90%.

The retro-reflected light is in the scintillation fibers 13 to the photoelectric converter 19 and is thus available for metrological detection. This leads to a significant increase in the light output. This increases the metrologically detectable amount of light of each individual in the individual scintillation fibers 13 triggered light pulse and thus the detectability of the individual pulses. Accordingly, scintillation detectors according to the invention 7 a significantly higher sensitivity than conventional scintillation detectors.

The retroreflecting device 23 can be formed in various ways, which are basically divided into two groups. A first group includes those retroreflection devices 23a , which is a front side of the second end 21 of the scintillation fiber bundle 11 cover the whole area. 2 shows an embodiment thereof, in which the illustrated retroreflection device 23a an applied on the front side micro prism is. The front side of the Szintillationsfaserbündels 11 preferably polished before applying the micro-prism film.

A second group includes those retroreflection facilities 23b containing one of a number of scintillation fibers 13 corresponding number of individual retroreflectors 25 include, the front side on the fiber ends 27 the individual scintillation fibers 13 are applied. 3 shows as examples of this, one of a single retroreflector 25 closed end of a single scintillation fiber 13 , The illustrated embodiment of the retroreflector 25 is one on the front of the fiber end 27 applied microprism, z. B. a microtripel prism. Right next to the scintillation fiber 13 is in 3 a plan view of the provided with the microtip Prima fiber end 27 shown. The microtip prism has three mutually inclined reflecting surfaces A, B, C, which are in the scintillation fiber 13 converging direction in a peak converge.

The scintillation fibers 13 each have one of an outer fiber cladding 29 surrounded fiber core 31 in which an incident absorbed gamma photon γ triggers a flash of light, its light through multiple reflections on the fiber cladding 29 both directly - as here by the arrow pattern shown by thicker solid lines 33 represented - as well as indirectly - as here by the arrow line shown by thinner lines 35 represented - via a retroreflection at the respective retroreflector 25 in the direction of the photoelectric converter 19 spreads.

The invention can also be used in conjunction with scintillation detectors of the type described above, which instead of the scintillation fiber bundle described above 11 have a solid rigid Szinitallationsstab in which radioactive radiation incident thereon are converted into flashes of light, the light propagates to both ends of the Szintillationsstabs out. Again, a photoelectric transducer is connected to a first end of the scintillation rod, which converts incident light into an electrical signal corresponding to a radiation intensity incident on the scorching rod. In this case, a retroreflecting device, in particular a microprism foil, is provided at the end opposite the first end of the second scintillation bar, which covers the entire end face of the latter.

LIST OF REFERENCE NUMBERS

1

filling

3

container

5

spotlight

7

detector

9

measuring electronics

11

scintillation

13

scintillation

15

Conduit

17

first end of the scintillation fiber bundle

19

photoelectric converter

21

second end of the scintillation fiber bundle

23

Retro reflection device

23a

Retro reflection device

23b

Retro reflection device

25

retroreflector

27

fiber end

29

fiber cladding

31

fiber core

33

directly photo-electrical converter transmitted light

35

indirectly via the retroreflector to the photo-electrical converter transmitted light

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1068494 B [0007]

Claims (8)

Scintillation detector for a radiometric measuring device for measuring a measured variable, in particular a measuring device for measuring a fill level or a density of a in a container ( 3 ) ( 1 ), and / or for monitoring an exceeding or falling below of a predetermined limit value for the measured variable, with - one of scintillation fibers ( 13 ) existing scintillation fiber bundles ( 11 ), in which scintillation fibers ( 13 ) incident radioactive radiation (γ) in the respective scintillation fiber ( 13 ) is converted into flashes of light whose light is reflected in the respective scintillation fiber ( 11 ) to the ends thereof, - one to a first end ( 17 ) of the scintillation fiber bundle ( 11 ) connected photo-electrical converter ( 19 ), the light impinging thereon into the one on the scintillation fiber bundle ( 11 ) converts the corresponding radiation intensity corresponding electrical signal, and - one at a first end ( 17 ) opposite second end ( 21 ) of the scintillation fiber bundle end provided retroreflection device ( 23 . 23a . 23b ) performing a retroreflection over the scintillation fibers ( 13 ) incident thereon light into the scintillation fibers ( 13 ) causes back. Scintillation detector according to claim 1, in which the retroreflecting device ( 23a ) an end face of the second end ( 21 ) of the scintillation fiber bundle ( 11 ) covered over. Scintillation detector according to Claim 2, in which the retroreflecting device ( 23a ) is a flat on the front side applied micro prism sheet. Scintillation detector according to claim 1, in which the retroreflecting device ( 23b ) one of a number of scintillation fibers ( 13 ) corresponding number of retroreflectors ( 25 ), the front side on the ends of the scintillation fibers ( 13 ) are applied. Scintillation detector according to Claim 4, in which the retroreflectors ( 25 ) Are triple prisms. Scintillation detector for a radiometric measuring device for measuring a measured variable, in particular a measuring device for measuring a fill level or a density of a in a container ( 3 ) ( 1 ), and / or for monitoring a predetermined limit for the measured variable, with - a scintillation rod, in which radioactive radiation incident thereon is converted into flashes of light, the light of which spreads to both ends of the scintillation bar, - one on the first end of the scintillation rod connected photoelectric transducer, the light incident thereon in a corresponding to an incident on the Szinitillationstab radiation intensity converts electrical signal, and - at one of the first end opposite the second end of the Szintillationsstabs end provided retroreflecting means, esp. A micro prism film, the causes a retroreflection of incident light on the scintillation rod thereon back into the scintillation rod. Radiometric measuring instrument for measuring a measured variable, in particular a filling level or a density, of a container ( 3 ) ( 1 ), and / or for monitoring an exceeding or falling below of a predetermined limit value for the measured variable, with a scintillation detector according to one of the preceding claims. Radiometric measuring device according to claim 7, - which is a radioactive emitter ( 5 ), which in use radioactive radiation through the container ( 3 ), in which the scintillation detector is mounted on a radiator ( 5 ) opposite side of the container ( 3 ), and - in which the scintillation detector serves to pass through the container ( 3 ) to receive urgent dependent on the measured variable radiation intensity and convert it into an electrical output signal.

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