A REMOTE FIBER OPTIC LASER TLD SYSTEM

A fibre optic laser heated TLD system has been developed for use in re mote in vivo, in situ dosimetry. A high power, near infrared CW semico nductor laser is used to heat TL elements at the distal end of standar d optical fibres. Lengths of up to 200 m are feasible, with overall di ameter as small as 1 mm. The system is multiplexed, with current capab ility of evaluating up to five dosemeter probes in under 30 s, with ex tension to larger numbers a trivial matter. The system is inherently i mmune to electromagnetic interference. The small mass of the TLD eleme nt (almost-equal-to 100 mug) provides for highly localised dose measur ement capability. A wide variety of TLD phosphors are used for various applications requiring high sensitivity, low fading, or a combination of both, providing a useful dose range of 1 mGy to greater than 100 G y. Such applications include radiotherapy dosimetry (external and inte rnal when constructed with a sterile catheter), hazardous and remote e nvironments, such as monitoring ground water or soils tor radioactive contamination.