Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Patent
1998-03-20
2000-06-06
Hannaher, Constantine
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
25037009, 2503701, H01L 3100, G01T 124
Patent
active
060721812
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to an ionizing radiation detector, and in particular to a detector suitable for detecting high energy radiation and/or charged or neutral particles.
2. Background of the Invention
A typical prior art detector is shown in FIG. 1. The detector comprises a flat sheet 10 of an insulating material such as diamond, having thin gold electrode coatings 12,14 on its upper and lower surfaces. The upper electrode coating 12 comprises a plurality of parallel readout strips which are aligned in a direction perpendicular to the plane of the paper in the Figure, and the lower electrode coating 14 comprises a further plurality of readout strips aligned in a direction parallel with the plane of the paper. A large potential difference V is maintained between the electrode coatings.
A charged particle following a path 16 through the diamond produces electron-hole pairs 18,20, which separate under the influence of the electric field and induce a charge on the readout strips. The energy of the particle can be determined by the amount of charge which is collected, and its position by the intersection of the upper and lower strips receiving the largest induced charges.
There are a number of disadvantages with this type of detector, in particular its relatively poor charge collection efficiency. The charge collection efficiency is typically limited by the charge intrinsic life time within the diamond, and this can only be made large if expensive diamond is used, having a large recombination length. In addition, the accuracy with which the particle can be located in the x-y plane is limited by the inevitable cross-talk between the readout channels. Finally, the detector is sensitive to particles coming in from a wide range of angles, which means that it is not particularly suited for imaging purposes. If imaging is to be required, it is normally necessary to incorporate a collimator in front of the detector to ensure that particles travelling at an angle to the normal to the detector surface are weeded out. Such collimators not only add to the cost of detection equipment, but also limit its sensitivity.
In an effort to improve detection efficiency, and to avoid the use of collimators, there have been a number of proposals to provide detectors which are deep in comparison with their width. Typically, a bundle or stack of several of these individual detectors are used together. Examples are shown in U.S. Pat. No. 4,891,521 and GB-A1559664. The devices shown in both of these documents appears to be specifically intended for high-rate data taking. The present invention, on the other hand, is concerned with providing a device which is at least in principle capable of extremely high time resolution and spatial resolution when detecting an individual event.
It is an object of the present invention at least to alleviate the problems of the prior art.
SUMMARY OF THE INVENTION
According to the present invention there is provided an ionizing radiation detector comprising a single wafer of a detector material, the wafer having a plurality of parallel sided grooves in a surface thereof thereby defining between the grooves a plurality of parallel sided detector elements, opposing sides of each element carrying opposing readout electrodes; and means for applying a potential difference between the opposing electrodes of each element to create an electric field across the element.
Also according to the present invention there is provided an ionizing radiation (or photo) detector comprising a substrate and a plurality of detector elements, having generally parallel sides, extending outwardly from a surface of the substrate, the sides carrying readout electrodes.
Such detectors of the present invention have many advantages, particularly for the construction of the type of detector working on the photoconducting principle. They are relatively cheap to manufacture, they can provide high sensitivity, extremely fast readouts, and they can provide very accurate positioning information with
REFERENCES:
patent: 3691389 (1972-09-01), Ellis et al.
patent: 3824680 (1974-07-01), Kozlov et al.
patent: 5079425 (1992-01-01), Imai et al.
PCT International Search Report PCT/GB 95/01724.
Choi Peter
Hassard John Francis
Gagliardi Albert
Hannaher Constantine
Imperial College of Science
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