  Three different thermoluminescent measuring systems have been compared with
respect to the differences in temperature profiles, spectral sensitivities, as
well as linearity of dose response characteristics. The comparison was
performed using the Harshaw 3500, Riso DA-20 and RA94 TLD readers. The
instruments were tested for the readouts of highly irradiated LiF:Mg,Cu,P (MCP)
TL detectors, which require readout up to 550 C, in case of doses exceeding 1
kGy. It was found that the Harshaw 3500 can be used, without any additional
light attenuation, for the measurements of MCP detectors exposed to doses up to
about 5 Gy. For the other two readers the upper dose limit is about 5 times
lower. It was also found that the Harshaw 3500 shows the best thermal stability
considering the peak maximum position. For the ultra-high doses the differences
in the spectral characteristics of the applied optical filters and
photomultipliers, in conjunction with an evolution of the MCP TL emission
spectrum with increasing dose, significantly influence the shape of TL glow
curves measured with the Riso reader. The detailed characteristic of the
compared TLD readers, at high-dose high-temperature range is discussed.
