RADCARD

Lithium fluoride thermoluminescent phosphor is recognised universally as an excellent material for broad dosimetric applications. It exhibits high sensitivity for general applications, low background, resistivity against environmental conditions and tissue-equivalence.

Lithium fluoride doped with magnesium and titanium (LiF:Mg,Ti) is produced by our company using a proprietary method. It is manufactured in the form of solid pellets of 4.5 mm diameter (other diameters on request) with any required thickness in the range of 0.2 - 1.5 mm (standard 0.9 mm), under the code name MTS (Mg, Ti, sintered), with an additional symbol representing the isotopic content of lithium: MTS-N (natural abundance), MTS-6 (⁶Li-enriched), MTS-7 (⁷Li-enriched). It is also available in the form of powder under the code names MT-N, MT-6 and MT-7. All these materials are indefinitely re-usable and exhibit similar dosimetric characteristics such as energy response for photons, fading and TL efficiency. The main features of MTS pellets are listed overleaf. A very important feature of our detectors is that they are exchangeable with other well known LiF:Mg,Ti phosphors and pellets commonly used in many laboratories (e.g. TLD-100). They may be read out with any typical TL reader, both with hot gas (e.g. Alnor DOSACUS or Harshaw 5500) and resistance (e.g. Harshaw 3500, Toledo or Solaro) heating systems.

Thus our MTS-N, MTS-6 and MTS-7 pellets can easily replace materials produced by other manufactures in all cases when their virtues such as higher sensitivity and lower prices are crucial.

MCP-type ultra-high sensitivity thermoluminescent pellets are the latest development in radiation protection dosimetry. They are an important supplementary dosimetry tool to the standard LiF:Mg,Ti type pellets (MTS-N) especially for low-dose measurements and are unmatched in the range below tens of µGy. Featuring a low, stable zero reading with a detection threshold of 50 nGy (200 times better than the standard LiF:Mg,Ti), they are 30 times more sensitive to gamma ray doses.

Our MCP-type ultra-high sensitivity detectors are solid circular pellets of 4.5 mm diameter with any required thickness in the range 0.3 - 1.5 mm (standard 0.9 mm).

The detectors consisting of 100% LiF:Mg,Cu,P TL phosphor are manufactured under the code name MCP (Mg, Cu, P), with an additional symbol, representing the isotopic content of lithium: MCP-N (natural abundance), MCP-6 (⁶Li-enriched), MCP-7 (⁷Li-enriched). The excellent dosimetric properties of the phosphor are enhanced by our original, carefully tested and controlled sintering procedure. The phosphor is also available in the form of powder.

The MCP chips are rather sensitive to thermal treatment which makes it important to use an annealing oven with good temperature stability. A summary of TL properties of MCP materials is given in the table overleaf. The extremely high sensitivity of MCP detectors opens new possibilities in the study of very low doses, e.g., of the variations of natural background throughout the day or monitoring of doses of persons briefly visiting nuclear installations. In measurements of doses below 1 µGy the natural gamma background should be taken into account.

The thin layer MCP-Ns (LiF:Mg,Cu,P) TL dosimeters designed in Krakow and manufactured exclusively in our company for measuring personal dose equivalent Hp (0.07) in weakly penetrating radiation fields [1-3]. These detectors show:

• Flat energy response for X-rays and for beta-rays
• High sensitivity to allow reliable measurement of doses in the microgray range
• Good reproducibility and mechanical stability

Detectors have a form of circular pellets with diameter 4.5 mm. Each pellet consists of two layers: a thin radiation sensitive part bonded to a thick base made of not activated LiF to which 2% of graphite was added in order to suppress any spurious luminescence. The effective thickness of the sensitive layer is about 8.5 mg. cm². The overall thickness of the pellet is between 0.5 mm and 0.9 mm depending on requirements of the customer.

1. Burgkhardt B., Piesch E., Bilski P., Budzanowski M. and Olko P.

Properties of New Thin Sandwich Detectors for Beta and Neutron Dosimetry . Proc. FS IRPA Jahrestagung, Karlsruhe 1994 (in German)

2. Bilski P., Olko P., Burgkhardt B. and Piesch E.

Ultra-Thin LiF:Mg,Cu,P Detectors for Beta Dosimetry. Radiat.Meas. 24 439-443 (1995).

3. Bilski P., Budzanowski M., Olko P. and Christensen P.

Properties of Different Thin-Layer LiF:Mg,Cu,P TL Detectors for Beta Dosimetry. Radiat.Prot.Dosim. 66 101-104 (1996).