X-ray or gamma ray systems or devices – Source – Electron tube
Reexamination Certificate
1996-07-15
2001-06-26
Church, Craig E. (Department: 2876)
X-ray or gamma ray systems or devices
Source
Electron tube
C378S143000
Reexamination Certificate
active
06252936
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an X-ray tube, comprising a cathode for generating an electron beam and an anode, having a comparatively thin anode target layer, for generating X-rays in response to the impingement of the electron beam, and also comprising an X-ray exit window.
2. Discussion of the Related Art
An X-ray tube of this kind is known as a target transmission tube from U.S. Pat. No. 4,969,173. An X-ray tube described therein comprises a radiation exit window which is made of, for example beryllium and an inner side of which is provided with a thin layer of metal which acts as the anode target layer. In the anode target layer notably the X-rays are generated, which X-rays emanate directly via the exit window in this case.
A thin anode target layer of this kind may also be provided on an anode support of a suitably thermally conductive material mounted in an X-ray tube. In the case of such thin anode target layers, the degree of dissipation of the heat generated by the incident electron beam has a strong effect on the service life of the tube. This problem is significant in target transmission tubes because of the comparatively poor thermal conductivity of the thin anode target layer itself as well as of the comparatively thin beryllium exit window. In the case of anode target layers provided on a metal anode support the problem of locally excessive temperatures may arise because the transition between the anode target layer and the anode support constitutes a heat barrier.
SUMMARY OF THE INVENTION
It is inter alia an object of the invention to mitigate these drawbacks; to achieve this, an X-ray tube of the kind set forth in accordance with the invention is characterized in that the anode target plate comprises means for enhancing the dissipation of heat.
Because the anode target layer itself is provided with means for enhancing the dissipation of heat, the temperature of this layer as a whole, and notably at the area of the electron target spot, will become less high, so that the layer will be less readily damaged and the service life of the tube is prolonged.
In a preferred embodiment, the means for enhancing the dissipation of heat constitute a metal structure which is provided in or against the anode target plate and which is thermally conductively connected to a wall portion of the X-ray tube or to a suitably thermally conductive anode support. The metal structure is notably a metal gauze which does not have a disturbing effect on the X-ray emission and provides adequate dissipation of heat. When the anode target layer is provided on a window plate, such a gauze structure may also provide a substantial reinforcement of the window, so that the window becomes less vulnerable or can be constructed to be thinner, resulting in an increased transmission.
In a preferred embodiment, a metal layer provided near an electron target face forms part of the means for enhancing the dissipation of heat. The metal layer is provided notably within a substantially annular electron target spot, so that the spot exhibits suitable dissipation of heat to both radial sides and a central part of the window as well as an irradiated part of the window will become considerably less hot.
In a further preferred embodiment, an anti-diffusion layer is provided between the anode target layer and a layer supporting the anode target layer. Using such a layer, a reduction of the thermal conduction between the two layers can be prevented, for example due to the appearance of intermetallic compounds. Such an anti-diffusion layer can also reduce other adverse interactions between the layers; for example, the loss of vacuum-tightness of the window can thus also be prevented. An anti-diffusion layer of this kind is provided notably between a window plate of beryllium and an anode target plate which is provided thereon and which consists of, for example rhodium scandium or another known anode target plate material.
REFERENCES:
patent: 4731804 (1988-03-01), Jenkins
patent: 4969173 (1990-11-01), Valkonet
patent: 5204891 (1993-04-01), Woodruff et al.
patent: 5420906 (1995-05-01), Smit
Gijsbers Jan C.
Jenneskens Theodorus J. J. M.
Smit Hubert H. A.
Barschall Anne E.
Church Craig E.
U.S. Philips Corporation
LandOfFree
X-ray tube with improved temperature control does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with X-ray tube with improved temperature control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and X-ray tube with improved temperature control will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2502169