Keiichi Shidara

Excess Noise in Amorphous Selenium Avalanche Photodiodes

Excess noise in amorphous Selenium avalanche photodiodes (a-Se APD) has been measured in a frequency range from 3 kHz to 30 kHz. The deduced excess noise factors, including dependences on photocurrent, frequency, applied electric field and the a-Se layers thickness, agreed with McIntyres theoretical values.

Development of the Super-HARP Camera, a Rival to the Human Eye, for the Next Generation of Broadcasting

NHK has developed a new high-performance camera tube for producing superior pictures, with a sensitivity 100 times that of conventional camera tubes or charge-coupled devices (CCDs). The new tube, called the Super-HARP, uses the phenomenon of avalanche multiplication in a thin target layer and is capable of producing high picture quality in a wide range of conditions, from daylight to moonlight. Its sensitivity has made it possible to develop many new kinds of programs, and it will certainly bring about changes in the basic techniques of TV program production and studio lighting.

Characteristics of a new high-sensitivity X-ray imaging tube for video topography

A new type of high-sensitivity X-ray imaging tube having an amorphous selenium photoconductive layer with a thickness of 8 µm has been fabricated. Signal charges induced by X-ray photons can be avalanche-multiplied in the photoconductive layer under a large electric field. The sensitivity of the tube reaches the level of individual X-ray photon detection. For the detection of such a small number of X-ray photons, a new kind of noise is generated due to the fluctuation of absorption depth in the photoconductive layer under the operation conditions of avalanche multiplication. Signal-to-noise ratio can be improved by the accumulation of signal charges in the photocon-ductive layer. An example of real-time X-ray topography by weak X-rays using this experimental tube is demonstrated.

A Blocking Contact on a Scanning Side of Photoconductive Pick-up Tube Target

As2Se3薄膜の表面をイオンボンバードすることにより, 走査側のブロッキング層を形成する実験を行った.正孔だけでなく電子の移動度も比較的大きいSe膜の上にこのブロッキング層を設けたターゲットは, 暗電流が少なくなり焼付きも良好であった.また残像も良好で, 大部分が容量性残像とみなせる領域に達していた.この残像はバイアスライトにより軽減できるが, メッシュ電極に塗布した螢光体により, この効果をうる実験も行った.

Camera Tube using Photoconductor As2Se3

光導電物質としてAs2Se3 (三セレン化砒素) の蒸着膜を用いた撮像管を試作したので, その結果を報告する.試作管は, 低暗電流, 低残像で感度も高く, 解像度もよい.電極構造は従来のビジコンと同じであるから, 小形, 軽量であり, 操作も容易である.As2Se3の禁止帯幅は狭いので, 赤色光に対しても感度があり, カラーカメラ用として期待される.