Liquid cooling system for linear beam device electrodes

An electrode of an inductive output tube (IOT) is provided with channels for guiding cooling fluid. In one aspect of the invention, the channels are in a confronting relationship with a jacket surrounding the electrode and spaced from the electrode so as to define an interior region. Cooling fluid such as oil is circulated in the channels in fluid communication with the interior region, providing an escape mechanism for trapped bubbles in order to prevent localized heating of the electrode. In another aspect of the invention, the channels form multiple intersecting helical patterns of different pitches, with the steeper-pitched channels providing a more direct escape route for the bubbles.

CROSS-REFERENCE TO RELATE APPLICATIONS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to linear beam devices, and more particularly, to a liquid system for electrodes of linear beam devices.

2. Description of the Related Art

Several approaches for cooling an electrode of a linear beam device such as an inductive output tube (IOT) klystron, extended interaction klystron (EIK), coupled cavity traveling wave tube (CCTWT) and traveling wave tubes (TWT), are known. One such approach circulates cooling water around the electrodes. The water removes heat from the electrode, improving efficiency and longevity of the device.

In cases where multiple electrodes are used, such as in a multi-stage depressed electrode (MSDC) device, concerns with arcing between electrodes have led to the development of oil-cooled systems, as the dielectric nature of some oils, unlike water, will repress arcing. Otherwise, the water used has to be de-ionized and issues with corrosion, limited operating temperatures and increased maintenance and operating costs arise.

One issue with oil, which has higher viscosity than water, is bubble formation. Trapped bubbles disrupt oil flow and displace the circulating oil. This results in localized heating at the region of the trapped bubble. Hotspots are thus formed, which, if unmitigated, can lead to catastrophic failure of the device.

There is therefore a long felt need for a liquid cooling system for linear beam device electrodes which addresses the problems associated with trapped bubbles in the fluid flow circuit.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the invention, a linear beam device in which electrons emitted by a cathode are collected by a collector having one or more electrodes is provided, the linear beam device including a housing having at least one electrode, the electrode having at least one channel provided on the exterior surface thereof for guiding cooling fluid. The linear beam device further includes a jacket disposed within the housing and spaced from the exterior surface of the electrode so as to provide a first, interior region in fluid communication with the channel and defined by the jacket and the exterior surface of the electrode and a second, exterior region defined by the jacket and the housing.

In accordance with another aspect of the invention, there is provided a linear beam device in which electrons emitted by a cathode are collected by a collector having one or more electrodes. The device includes a housing, at least one electrode disposed in the housing; and a plurality of intersecting channels provided on the exterior surface of the electrode for guiding cooling fluid in multiple substantially helical flow paths.

In accordance with another aspect of the invention, there is provided a linear beam device having at least one oil-cooled electrode and at least one water-cooled electrode.

In accordance with another aspect of the invention, there is provided a liquid-cooled electrode assembly for a linear beam device. The assembly includes a housing, a jacket disposed in the housing, and an electrode including at least one channel provided on an exterior surface and having an open side in confronting relationship with an interior region of the jacket. The assembly further includes input and output ports provided in the housing for passage of cooling fluid into and out of the liquid cooled electrode assembly, the cooling fluid flowing in the interior region and the at least one channel to thereby remove heat from the electrode.

In accordance with another aspect of the invention, there is provided a liquid-cooled electrode assembly for a linear beam device. The electrode assembly includes a housing, an electrode, and a plurality of intersecting channels provided on an exterior surface of the electrode for guiding cooling fluid in multiple substantially helical flow paths to thereby remove heat from the electrode.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic view of an inductive output tube (IOT)10provided with a cooling system in accordance with the invention. IOT10includes a cathode C from which electrons are emitted towards an anode A and collected by a multistage depressed collector MSDC. A grid G is optionally provided. Voltages VE1, VE2and VE3are applied respectively to electrodes E1, E2and E3of the MSDC. Voltages VAand VCand VGare applied respectively to the anode, cathode and grid. Although illustrated in conjunction with an IOT, the cooling system of the invention is not so limited, and applications with other types of devices, such as klystrons, extended interaction klystrons (EIKs), coupled cavity traveling wave tubes (CCTWTs) and traveling wave tubes (TWTs), are contemplated.

Cooling system12is provided to remove heat from the electrodes E1, E2and E3of the MSDC. The cooling system consists of a water cooler associated with electrode E1and an oil cooler associated with electrode E2and optionally electrode E3. Linear beam devices other than IOTs would have similar cooling devices associated with electrodes thereof.

FIG. 2is a longitudinal cross-sectional view of a portion of multi-stage depressed collector MSDC of the inductive output tube IOT10. Each of electrodes E1, E2and E3of the MSDC is electrically isolated from the others such that the electrodes can be biased differently depending on the application. Electrical isolation of the electrodes E1, E2and E3is provided by isolators14, which can be suitable electrically non-conducting materials such as polymers, ceramics, and so forth. In one aspect of the invention, electrode E1is grounded and electrode E3is at −34 kV. Electrode E2is held at about 40-60% potential of E3. The electrodes E1, E2and E3are of any conductive material that is suitable for high temperature and vacuum, such as copper, copper-coated or -sputtered aluminum nitride, copper-coated or -sputtered beryllium oxide and the like.

Cooling system12(FIG. 1) consists generally of two parts: a water-cooling portion associated with electrode E1and an oil-cooling portion associated with electrode E2(and E3). E1can be cooled by oil as well. Each portion includes a fluid circuit in which cooling fluid is circulated past the associated electrode in heat exchange relationship therewith. The water and oil cooling circuits each includes a fluid (water, water and glycol or oil) reservoir cooler, pump, conduits and other components (not shown). In the case of the water cooled electrode E1, an input port16(FIG. 2) is provided, through which cooling water is introduced. The water flows into an annular space18surrounding electrode E1and bounded by a sleeve20. Such flow removes heat from electrode E1thereby cooling same. The water then continues to an output port (not shown), through which it exits the MSDC, returning to the water cooler and completing the circuit.

A second oil circuit for cooling electrodes E2and E3is also provided. This second portion of the cooling system includes an oil cooler (FIG. 1) for cooling oil which is circulated past the electrodes E2and E3for removal of heat therefrom. Electrodes E2and E3are substantially cylindrical in shape and surrounded by a jacket26, also substantially cylindrical. A space shown in detail inFIG. 3is provided between electrodes E2and E3and jacket26, the space forming an annular interior region30of jacket26through which oil is circulated in heat exchange relationship with the electrodes E2and E3. The space is maintained using spacers38, such as spot face spacers, which threadably engage jacket26and pass therethrough to rest against the exterior surface of the electrodes, for example surface28of electrode E2. Oil enters interior region30from exterior region32by way of a gap34provided between end portion36of jacket26and an end wall or seal40. Oil is introduced into exterior region32from the oil cooler by way of input port41provided in housing39. Oil exits the MSDC by way of output port43.

As detailed inFIGS. 3 and 4, exterior surfaces28and29of electrodes E2and E3are grooved to thereby form channels46for passage of oil therein. The channels46form helical patterns along the exterior surfaces of the electrodes. Multiple intersecting and/or non-intersecting channels corresponding to different helices having different pitches can be provided, as seen inFIG. 4. Channel46ais helical and is shown as having a shallower pitch than helical channels46band46c, which are parallel to each other and nonintersecting. Channel46atherefore intersects channels46band46c. Cooling oil passes through channels46a,46band46con its way past the electrodes E2and E3in order to remove heat from the electrodes.

It will be appreciated that since jacket26is spaced from exterior surfaces28and29of electrodes E2and E3, the channels46a,46band46cremain open on the side facing interior region30. Circulating fluid flows past the electrodes E2and E3in channels46a,46band46c, as well as in interior region30. The distance of jacket26from exterior surface28of E2and E3as controlled by spacers38can be varied to control the proportion of cooling oil flowing in the channels46a,46band46crelative to that flowing in interior region30, depending on the particular design. One preferred ratio is about 60:40, meaning about 60% of fluid flow is through the channels, and about 40% is through interior region30.

An important advantage of the communication of channels46a,46band46cwith interior region30is to provide a mechanism to permit escape of bubbles which inevitably form in the oil flow path. Without such communication—that is, if jacket26were to abut against exterior surface28of the electrodes E2and E3to thereby eliminate interior region30—bubbles would become trapped in the channels46a,46band46c, displacing cooling oil and inducing localized heating of the surface of the electrodes. The interior region30provides an outlet for such bubbles by offering a more resistance-free path to the bubbles, avoiding their entrapment and resultant hotspots. It also enables active flushing of the bubbles should their entrapment be suspected.

The use of multiple intersecting channels also provides a bubble escape mechanism, as the steeper-pitched channels would form a more direct path for the bubbles to travel and/or be flushed out of the MSDC.

Further, by spacing jacket26away from the electrodes E2and E3, the jacket material can be selected to provide magnetic shielding of the collector and prevent RF leakage. One suitable material for this purpose is steel, although copper and other materials are contemplated. In addition, an electrically conductive material can be used to simplify the contact structure for electrode biasing. With reference toFIG. 5, it can be seen that an electrical path can be established from biasing cable50to electrode E2by way of pin52, conductive jacket26and conductive spacer38. Of course, if in such an arrangement spacers are required to separate jacket26from electrode E3as well, such spacers would have to be non-conductive in order to maintain electrical isolation of electrodes E2and E3from one another. Alternatively, spacers between jacket26and E3can be omitted altogether. Further alternatively, this biasing arrangement can be used to bias electrode E3, in which case and spacers separating jacket26from electrode E2would have to be non-conductive, or omitted altogether.

In accordance with one aspect of the invention the cooling oil used is a dielectric alpha 2 oil. The oil is selected to prevent arcing between the electrodes, particularly differently-biased electrodes E2and E3sharing the oil cooling portion of the cooling system12. In addition, oil has a high breakdown voltage, is more corrosion-resistant, has better operating temperatures, requires less maintenance, and can be used in a more compact arrangement than that for water or air cooling.

The above are exemplary modes of carrying out the invention and are not intended to be limiting. It will be apparent to those of ordinary skill in the art that modifications thereto can be made without departure from the spirit and scope of the invention as set forth in the following claims.