DE102006015499A1 - Thermoluminescent dosimeter for determining a dose of natural and/or artificial rays uses a card-shaped element to include a laser-induced fluorescence-based detector in the area of an associated retaining device - Google Patents

Abstract

Encapsulation is brought about through bottom (5) and top (6) plastic ethylene tetrafluoroethylene foils bonded to each other through thermal melting with high light -transmitting capacity and low inherent thermo-luminescence. One or more foil consists of a fluoric thermoplast. There are top (2) and bottom (3) plates, thermoluminescent dosimeter detectors (4) based on laser-induced fluorescence, i.e. magnesium, copper and phosphorus, bottom and top plastic foils and diverse rivets (7). An independent claim is also included for producing a thermoluminescent dosimeter.

Description

The The invention relates to a thermoluminescence dosimeter for detection the dose of natural and / or artificial Rays.

thermoluminescence have been in use for a variety of years for a variety of rays which persons are exposed to. This concerns α-, β-, γ-rays and neutron beams.

Of the DE-A 24 52 900 can be seen from a dosimetric map, the one or multiple thermoluminescence dosimeters, using the a predetermined code is individually identifiable or are. The dosimeters used are enclosed in encapsulated form of a substrate, wherein a synthetic resin polymer is used arrives.

In US-A 3,577,161 describes a radiation dosimeter, wherein as a detector lithium fluoride (LiF) in combination with lithium hydride (LiH) is used.

In DE-A 31 00 868 a Thermolumineszenzdosimeter with acting as Betafenster thin cover with a thickness of max. 1 mg / cm ² and an adjoining thin thermoluminescent Dosimeterscheibe and two subsequent other TLD discs of greater thickness, of which the calculated last window from the window has a thickness of at least 90 mg / cm ² .

Provided The detector material is in encapsulated form, come for decades Materials such as PTFE are used, but they have a number of disadvantages entail. One of the disadvantages is that PTFE is not in transparent Form is present, but rather has a milky appearance. Regarding the Workability is noted that PTFE is not thermoplastic (ie injection molding, extrusion) is processable, but in the field its softening point tends to smudge, so that in procedural Thermal encapsulation of the detectors may not occur homogeneous connection between two PTFE films is given.

thermoluminescence are often used for personal protection and must be specified intervals be evaluated as to which radiation exposure the respective person been suspended within a certain period of time. To the Insert here card readers, in which often nitrogen predeterminable temperature, over several time periods, on the substrate forming the detector via the PTFE film (s) acts. After a given calculation scheme, the respective Determined load value. These devices have been around for many decades in use.

exemplary reference is made to US-A 4,835,388.

As already mentioned, the encapsulated substrates are under certain Conditions warmed up, being natural Temperature limits on the one hand with respect of the film material (PTFE) and on the other hand of the substrate used given are. PTFE has a softening point which is about 330 ° C, wherein upon exposure to temperature on the respective substrate (e.g. LiF: Mg, Cu, P) decreases the efficiency already at about 280 ° C. Card readers as well Devices for thermal encapsulation of the detectors must on These conditions are set to allow the thermoluminescence dosimeter further uses can be.

PTFE films in the case of thermoluminescence dosimeters as standard material for encapsulation the substrates are used have a slightly milky structure and a poor overall heat transfer, so that the evaluation of the encapsulated substrates for a relatively long time lasts. Usual reading cycles The substrates in such card readers are 45 seconds.

in the Regard to yourself constantly expanding use cases for thermoluminescence dosimeter can there are longer waiting times when evaluating the cards, which is rather undesirable is.

aim the subject of the invention is a thermoluminescence dosimeter to determine the dose of natural and / or artificial To further develop rays to the effect that through the use of different Films / film combinations the evaluation time of the encapsulated substrates across from The prior art can be significantly reduced, creating a increased Throughput speed and associated cost savings given is. The thermoluminescence dosimeters are said to go beyond that easy and inexpensive be produced.

This object is achieved by a thermoluminescence dosimeter for determining the dose of natural and / or artificial rays, formed by an approximately card-shaped element, which includes at least one encapsulated detector arranged in the region of an associated recess based on LiF, wherein the encapsulation by each other by thermal Melt-bondable films with high light transmittance and low Eigenhermolumineszenz is brought about by which at least one consists of at least one fluorothermoplastics.

advantageous Further developments of the subject invention are the dependent claims remove.

This Goal is also achieved by a method of producing a Thermolumineszenzdosimeters by at least one slide on a plate-shaped aid excited and then with an embossed pattern is provided, a plurality of detectors, in particular in the form of chips or discs, in the embossed Wells are introduced, then at least one more Film including the respective detector on the first Applied film and placed on it another plate-shaped aid is heated, this system up to melting temperature of the films and subsequently Pressed under pressure, the films at the same time Fixation of the detectors are homogeneously interconnected.

advantageous Further developments of the method according to the invention are associated with the associated subclaims remove.

ever After use, the encapsulated detectors are isolated (for example two side by side) and with prefabricated associated recesses, about card-shaped trained elements, if necessary, using further Films, adhesives or the like, brought into operative connection.

To the Use either only Fluorthermoplastfolien or film combinations with single material thickness <100 microns, in particular <50 microns. The have used films compared to pure PTFE films, a high transparency, that is high light transmission and have very little inherent luminescence.

By The use of different types of films / film combinations can be used Residence times of the cards when reading the radiation dose considerably faster enforced, saving up to 60% of the time, which brings a significant cost savings.

The used films are in the temperature range between 240 and 300 ° C preferably melt-technically connectable to each other, wherein the in the card reader applicable temperatures then do not exceed this melting point allowed to.

With the film of the invention can Various detectors are brought into operative connection. Of particular advantage, however, are detectors based on LiF, but especially based on LiF with additions of Mg, Cu, P, since the same in connection with the film / film combination according to the invention bring optimal readout characteristics.

At least one of the films used is formed by a Ethylene tetrafluoroethylene (abbreviation ETFE). This material is formed by a fluorinated copolymer consisting of the monomers tetrafluoroethylene and ethylene. ETFE is a PTFE derivative. films From this plastic have a low weight and compared With PTFE films a high light and UV transmission.

alternative may also be a flat film based on a copolymer of tetrafluoroethylene and perfluorinated co-components (MFA). Compared with pure PTFE is an almost universal chemical resistance, a high thermal stability and given a good antiadhesiveness. The film can be welded, for example, in a thermo-pulse process.

Conceivable are also foil combinations. For example, an ETFE film with simultaneous encapsulation of the detectors with an MFA film welding technology get connected.

A more foil combination is for certain applications, such as increased Temperature in card readers, conceivable, with the heated Gas (nitrogen) facing film through a PTFE film and a the read-out area facing film formed by an ETFE or MFA film becomes. Straight MFA films form an excellent hotmelt adhesive for PTFE.

Of the Subject of the invention is illustrated by an embodiment and is described as follows. Show it

1 and 2 Different views or sections of a card-shaped thermoluminescence dosimeter.

The 1 and 2 show the basic structure of a card-shaped thermoluminescent 1 , Visible is an upper plate 2 , a lower plate 3 , TLD detectors 4 based on LiF (Mg, Cu, P), a lower plastic film 5 , an upper plastic film 6 as well as various rivets 7 , It can also be seen an adhesive layer 8th and a barcode 9 , In this example, the films used are to be used 5 . 6 made of ETFE, which under fixation of the detectors 4 melted together before joining them between the plates 2 . 3 be inserted and thus by riveting a composite is generated.

Alternatively, it is also possible for one of the slides 5 . 6 ETFE and for the other 6 . 5 Use MFA as material and both foils 5 . 6 weld technology to connect with each other.

For certain applications, namely, when in card readers with respect to the gas used higher temperatures, eg> 250 ° C, given, it may be useful to the gas facing the film 5 made of PTFE and the read-out area facing film 6 from ETFE or MFA manufacture or use.

Of the Specialist becomes dependent from the application, select the appropriate slides.

1

thermoluminescence

2

upper plate

3

lower plate

4

TLD detector

5

lower Plastic film

6

upper Plastic film

7

rivet

8th

adhesive layer

9

barcode

Claims (16)

Thermoluminescence dosimeter for determining the dose of natural and / or artificial rays, formed by an approximately card-shaped element ( 1 ), which has at least one encapsulated detector (in the region of an associated recess) ( 4 ) based on LiF, wherein the encapsulation by interconnecting by thermal fusion films ( 5 . 6 ) having high light transmittance and low intrinsic luminescence, of which at least one ( 5 . 6 ) consists of at least one fluorothermoplastic. Dosimeter according to claim 1, characterized in that each foil ( 5 . 6 ) has a material thickness <100 .mu.m, in particular <50 .mu.m. Dosimeter according to claim 1 or 2, characterized in that the detector ( 4 ) is formed by LiF with additions of Mg and / or Cu and / or P. Dosimeter according to one of claims 1 to 3, characterized in that the films ( 5 . 6 ) the detector ( 4 ) fix in the course of their connection process in a predetermined position by melting. Dosimeter according to one of claims 1 to 4, characterized in that the compound of the films ( 5 . 6 ) in the temperature range of 240 to 300 ° C can be brought. Dosimeter according to one of claims 1 to 5, characterized in that the respective detector ( 4 ) is in the form of a pressed chip or disk. Dosimeter according to one of claims 1 to 6, characterized in that the respective film ( 5 . 6 ) is formed by ethylene and tetrafluoroethylene (ETFE). Dosimeter according to one of claims 1 to 6, characterized in that the respective film ( 5 . 6 ) is formed by a copolymer of tetrafluoroethylene and perfluorinated cocomponent (MFA). Dosimeter according to one of claims 6 or 7, characterized in that the film ( 5 ) in operative connection with a PTFE film ( 6 ) can be brought. Dosimeter according to one of claims 1 to 9, characterized in that the light transmission of the film ( 5 . 6 ) is in the range of 350 to 600 nm depending on the selected material thickness. Dosimeter according to one of claims 1 to 10, usable in a read-out device, in which nitrogen in the temperature range of 200 to 280 ° C at predetermined time intervals over one of the films ( 5 ) on the respective detector ( 4 ) acts. Process for the preparation of a thermoluminescence dosimeter in which at least one film ( 5 or 6 ) is stretched on a plate-shaped aid and then provided with an embossing pattern, several detectors ( 4 ), in particular in the form of chips or disks, are introduced into the impressed recesses, then at least one further film ( 6 or 5 ) involving the respective detector ( 4 ) on the first slide ( 5 or 6 ) is applied and then another plate-shaped aid is applied, this system up to melting temperature of the films ( 5 . 6 ) and then pressed under the influence of pressure, the films ( 5 . 6 ) with simultaneous fixation of the detectors ( 4 ) are homogeneously interconnected. Method according to claim 12, characterized in that the encapsulated detectors ( 4 ) separated depending on the application and with prefabricated, associated recesses having, approximately plate-shaped elements ( 2 . 3 ), if necessary using further films, adhesives ( 8th ) or the like are brought into operative connection. A method according to claim 12 or 13, characterized in that two of the same material existing plastic films ( 5 . 6 ) are homogeneously interconnected by melting. A method according to claim 12 or 13, characterized in that two of different material existing plastic films ( 5 . 6 ). Method according to one of claims 12 to 15, characterized in that the foil to be provided with the embossing pattern ( 6 ) is formed by a PTFE film which is coated with an ETFE or MFA film ( 5 ) with simultaneous fixation of the detectors ( 4 ) is connected.