Electric lamp and discharge devices: systems – Cathode ray tube circuits – Combined cathode ray tube and circuit element structure
Reexamination Certificate
1998-10-22
2001-11-20
Lee, Benny T. (Department: 2817)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Combined cathode ray tube and circuit element structure
C313S045000, C313S046000, C445S035000
Reexamination Certificate
active
06320315
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to collector assemblies used for collecting spent electrons in linear beam electron devices. More particularly, the invention is directed to a collector assembly having a hot-inserted molybdenum sleeve to separate the ceramic collector core from a corresponding heat sink in order to provide improved high temperature operation.
2. Description of Related Art
Linear beam electron devices are well known in the art for generating and amplifying high frequency signals. In a linear beam device, an electron gun comprising a cathode and an anode generates a linear beam of electrons. The electron beam passes through an interaction structure, or drift tube, in which the energy of the beam is transferred to an electromagnetic signal. At the end of the drift tube, the spent electrons of the beam pass into a collector structure that captures the electrons and recovers a portion of their remaining energy. Electrodes disposed within the collector structure are used to collect the spent electrons at close to their remaining energy level in order to return the electrons to the power source of the linear beam electron device. Energy of the spent electrons that cannot be collected onto the electrodes is dissipated into the collector structure in the form of heat.
Since linear beam electron devices operate at very high power levels, the collector structure must be capable of withstanding very high operating temperatures, e.g., above 200° Celsius. Moreover, the collector structure must stand off the voltage potential between individual ones of the collector electrodes. In view of these demanding operational requirements, the central core of the collector structure is often comprised of a thermally rugged and electrically non-conductive material, such as ceramic. To remove the heat from the collector core, collector assemblies generally also include a heat sink provided in contact with the outer surface of the collector core. Typically, the heat sink is made of a material having good thermal conductivity, such as copper or aluminum.
A drawback of such prior art collector assemblies is that the ceramic collector core and metal heat sink can be incompatible due to the differences in their respective rates of thermal expansion. In one method of manufacture known in the art, the ceramic collector is dimensioned to fit into a corresponding opening in the heat sink at room temperature. During high temperature operation, the metal heat sink expands at a higher rate than the ceramic core, causing the heat sink to expand away from the collector core and leave a gap between the two adjacent structures. The heat sink is thereby no longer effective in removing heat from within the ceramic collector core, resulting in excessive stress of the collector core and ultimately failure of the component. A proposed solution to this problem is to dimension the ceramic collector core to fit the thermally expanded size of the heat sink, and to insert the collector core into the heat sink with the heat sink pre-heated to the operational temperature. This method is not practical due to the difficulty of constructing the entire collector assembly in a high temperature environment.
It would therefore be highly desirable to provide a collector structure having a ceramic collector core that permits high temperature operation without the drawbacks of the prior art. More particularly, it would be desirable to provide a collector assembly having efficient heat transfer from the ceramic collector core to the surrounding heat sink while operating at relatively high temperatures.
SUMMARY OF THE INVENTION
In accordance with the teachings of the present invention, a collector structure for a linear beam device is provided which overcomes the drawbacks of the prior art. The collector structure comprises a heat sink having a cylindrical opening, a sleeve disposed within the cylindrical opening of the heat sink, and a collector core disposed within the sleeve.
In an embodiment of the invention, the sleeve is comprised of a material having a rate of thermal expansion different than that of the heat sink and is disposed in close contact with the heat sink when the collector is at an elevated operational temperature. A slight gap is defined between the collector core and the sleeve when the collector is at an ambient temperature, and the collector core is in close contact with the sleeve when the collector is at the operational temperature. The heat sink further comprises either copper or aluminum, the sleeve is comprised of molybdenum, and the collector core is comprised of a ceramic material. To manufacture the collector structure, the heat sink is heated to a temperature above the operational temperature and the sleeve is inserted into the cylindrical opening of the heat sink at the elevated temperature. The collector core is then inserted into the sleeve at an ambient temperature of the collector structure. During operation of the collector, heat generated within the collector core is efficiently conducted through the sleeve to the heat sink.
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patent: 3717787 (1973-02-01), Doyle
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Lee Benny T.
Litton Systems Inc.
O'Melveny & Myers LLP
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