The Solid - State Ionization Chamber

Shallow diffused silicon p-n junction detectors have been used as room-temperature particle spectrometers for protons, alpha particles, heavy ions, and fission fragments. By the use of high base resistivity devices operated at high reverse biases (> 200 volts), the width of the sensitive volume has been extended beyond 0.5 mm, permitting linear response to protons up to 9 mev. Improved diffusion techniques have resulted in more shallow diffusion depths so that the "window effect" is reduced, extending the low energy response to below 200 kev for alpha particles. Use of low-noise amplifiers has permitted observation of half-widths of the pulse height-distribution equivalent to 18 kev.