X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
1999-11-19
2002-05-07
Porta, David P. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Absorption
C250S374000, C250S385100
Reexamination Certificate
active
06385282
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a detector for detection of ionizing radiation and to an apparatus for use in planar beam radiography
2. Description of Related Art
A detector and an apparatus of the kind mentioned above are described in copending U.S. application Ser. No. 08/969,554, now U.S. Pat. No. 6,118,125 and copending U.S. application Ser. Nos. 09/443,292, 09/443,294, 09/443,321 and 09/444,569, which are incorporated herein by reference. Another detector and apparatus of the kind mentioned above is disclosed in EP-A1-0 810 631.
The main advantages with gaseous detectors, compared to solid state detectors, are that they are cheap to manufacture and that they can employ gas multiplication to strongly (on orders of magnitude) amplify the signal amplitudes. However, in the gaseous detector, spark discharges can occur in the gas volumes of the detector, due to the strong electric fields created in the detector. Such spark discharges block the detector for a period of time, and can also be harmful for the detector and the electronics.
SUMMARY OF THE INVENTION
The present invention is directed to a detector for detection of ionizing radiation, which employs avalanche amplification, and limits the problems caused by spark discharges.
This and other objects are attained by a detector for detection of ionizing radiation, comprising:
a chamber filled with an ionizable gas,
first and second electrode arrangements provided in said chamber with a space between them, said space including a conversion volume, wherein
at least one of the first and second electrode arrangements comprising a resistive material having a surface facing the other electrode arrangement
an electron avalanche amplification unit arranged between the first and second electrode arrangements, and
at least one of the first and second electric arrangements including read-out elements for detecting electron avalanches.
The present invention is also directed to an apparatus for use in planar beam radiography, comprising at least one detector for detection of ionizing radiation, which employs avalanche amplification, and limits the problems caused by spark discharges.
This and other objects are attained by an apparatus for use in planar beam radiography, comprising
an X-ray source,
a substantially planar beam unit for forming a substantially planar X-ray beam positioned between said X-ray source and an object to be imaged,
a chamber filled with an ionizable gas,
first and second electrode arrangements provided in said chamber with a space between them, said space including a conversion volume, wherein
at least one of the first and second electrode arrangements comprising a resistive material having a surface facing the other electrode arrangement,
an electron avalanche amplification unit arranged between the first and second electrode arrangements, and
at least one of the first and second electric arrangements including read-out elements for detecting electron avalanches.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
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Francke Tom
Peskov Vladimir
Ullberg Christer
Hobden Pamela R.
Porta David P.
Xcounter AB
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