Some Interesting Work on Capillary Glass Detectors

Some Interesting Work on Capillary Glass Detectors

DOI: 10.4018/978-1-4666-6014-4.ch006
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Abstract

In this chapter, the progress of the development of glass capillary plates is described. In some applications, capillary plates have advantages over GEM or other gaseous detectors. For example, they are compatible with vacuum technology allowing them to be used in sealed gaseous detectors. Prototypes of capillary plates combined with photocathodes sensitive to ultraviolet and visible light were the first to be developed and successfully tested. These detectors resemble vacuum imaging microchannel plates, widely used in many applications. However, the glass capillary plates operate in gas atmosphere and in avalanche mode. This offers a possibility to build large area position-sensitive photomultipliers since at atmospheric pressure there are no serious mechanical constrains on the window. Since glass has a high density, the capillary plate can also be used as efficient convertors of X-rays, and be used at the same time as a multiplication structure for the created primary electrons. Such a device is attractive for X-ray and gamma ray imaging and the first successful tests of a prototype of such a detector are described.
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2. The Use Of Capillary Plates Operating In A Gas Flow

2.1 Capillary Plates as a Preamplification Structure

One interesting feature of capillary glass plates is that their resistivity can be greatly reduced by hydrogen treatment of their inner walls (Sakurai, 1996). This increases their rate characteristics, comparable to or even higher than GEM.

Similar to GEM, capillary plates can be used as a preamplification structure for other gaseous detectors. For example, a hydrogen treated capillary plate has been combined with an MSGC, and stable operation was achieved up to a counting rate of 106 Hz/mm2 (see Figure 1) (Ochi, 2002).

Figure 1.

Gas gains versus counting rate for H2 treated capillary plate, MSGC and for MSGC combined with a capillary plate (Ochi, 2002)

With this cascaded detector high quality X-ray images were obtained with a spatial resolution of ~94μm (RMS) (see Figure 2).

Figure 2.

Examples of the images (standard phantoms) obtained with MSGC combined with conductive capillary plate

In this study, the conversion of X-ray photons to primary electrons occurred in the gas which gives rather low detection efficiency.

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