| 摘要 |
<p>Photocell for X-rays and gamma rays consists of an e.g. Al foil covered on either side with a 35 to 40 mu thick layer of Se doped with oxygen. An Al layers e.g. 0.2 mu thick is sputtered on top of this to act as an electrode. A potential of 200-300 volts is applied between the Al surface layers and the central foil. An ammeter measures the current from the centre foil and thus gives the resistance of the layers. The photocell has a good dark resistance facilitating the measurement of low X-ray intensities. The photocells absorbs approx 10% of the X-rays passing through it. For X-rays of 50 KeV, the sensitivity is 50 times heat of known ionisation, chambers.</p> |
