A silicon diode in a thimble-type mount for measurement of diagnostic x-ray spectra.

A silicon detector which can be used like a thimble chamber has been constructed. The silicon diode chip used here is very small (1.7 x 1.7 x 0.1 mm3), and the construction materials of the detector mount are thin and have low atomic numbers. Thus, the characteristic x-rays from the mount give no distortion on the obtained spectra, and the photons incident on the back surface of the silicon chip can be measured. Furthermore, the perturbation of the x-ray field is small. The energy resolution of the detector is 2.0 keV (full width at half maximum) for 59.5 keV photons at room temperature. Bremsstrahlung spectra (60-100 kV, 1-2 mA) have been measured without using a pinhole collimator; the obtained spectra are in good agreement with those obtained with a Ge detector. The spectrum of the radiation in a water phantom irradiated with 90 kV x-rays has also been measured by inserting the detector in the phantom; the obtained scattered spectrum has been corrected for the angular dependence of detector efficiency. The increase in total photon number due to this correction has been found to be below 2%.