**5. The radio-photoluminescence model**

The luminescence materials used in either TLD or OSLD have an ordered crystal structure with lattice defects. From the glow curve, which is generated after annealing, one has the information on the electron distribution functions at different energy trap(s). The luminescence models for TLD and OSLD are developed based on this information. However, RPLGD is a mixture of inorganic amorphous solid and does not have lattice structure and lattice luminescence centers. Therefore we cannot get the information on electron trip(s) distribution function to establish the luminescence model for RPLGD. We can only establish the radio-photoluminescence model based on the energy of the excitation source and the energy of the released visible light.

After excited with 337.1 nm pulse ultra-violet laser, RPLGD emits 600 – 700 nm visible lights. From the emitted lights we know the energy gap between the excited energy levels which electrons jump to and the energy levels at color centers is between 1.78 and 2.07 eV. Becker assumed there are many continuous energy levels at the color centers of the RPLGD (Becker), as shown in Figure 6. It shows the electrons in the valence band are excited to the conduction band after irradiation. When electrons return to the valence band, portions of electrons are captured by the electron trap(s) located at P shell and Q shell, and then form color centers. After excitation, the electrons in color centers jump to higher energy level, emit fluoresce, then return to the original color centers. RPLGD is manufactured via the process of melting various compounds under high temperature, different from the manufacture process of TLD or OSLD which is via process of long-crystal formation. Hence, the color centers of PRLGD are not built at the lattice. There are no formal reports on the

Radio-Photoluminescence Glass Dosimeter (RPLGD) 561

GD-450 are the same as that of SC-1; to estimate radiation energy and to lower the energy dependence effect. The GD-450 dosimeters are the major personal dosimeters used in Japan.

Fig. 7. Three types of RPLGD; above: SC-1 system for environmental radiation monitor; below left: GD-450 system for personal dose monitor; and below right: small volume Dose

The Dose Ace type RPLGD is mainly for research purposes. It is a cylindrical shape with three different models; GD-302M, GD-352M, and GD-301. The GD-302M and GD-352M have a length of 12 mm and a diameter of 1.5 mm, while GD-301 has a length of 8.5 mm and a diameter of 1.5 mm. GD-301 and GD-302M, without filters in capsule, are used to measure the dose of high energy photons as in radiotherapy. However, there is a Tin filter in the capsule for GD-352M to lower the energy dependence effect. The GD-352M can be used for measuring the dose from low energy photons as in diagnostic radiology. In the process of dose readout, based on the dose values, the dose ranges are divided into two categories, low dose range (10 Gy – 10 Gy) and high dose range (1 Gy - 500 Gy).The readout system can automatically distinguish the dose range according to different readout magazine used by the users. On the top of that, there are different readout areas in RPLGD for different dose ranges too. The readout area for high dose range is located at between 0.4 mm and 1 mm, a total length of 6 mm and a total volume of 0.47 mm3, from the non-series end in the

Ace system for research

luminescence model for RPLGD. We believe that the color centers of RPLGD may be structured among the orbital electrons in the compound. The various continuous energy levels are formed with different bonding structures among elements. Those energy levels can store free electron energy which is produced by the excitation process. Therefore, its excitation energy gap has a continuous value (from 1.78 to 2.07 eV) which releases 600 nm – 700 nm visible lights.

Fig. 6. There are many continuous energy levels in RPLGD color centers.
