Varian Associates, Inc.

USA As Represented by Secretary of the Navy

William A Gerard

George K Farney

Robert J Foreman

A wide bandwidth linear motor system suitable for high performance applications such as driving the tuning plunger of a magnetron oscillator. The linear motor includes a coil assembly with a structure which suppresses secondary resonances, thereby permitting the linear motor to be used in a wide bandwidth servo control loop. The coil assembly includes a cylindrical coil support, a bushing coaxial with the coil support for attachment to the linear motor shaft, a plurality of radial ribs connecting the coil support to the bushing and a coil having multiple turns wound circumferentially around the coil support. The coil support is subdivided by axial gaps into at least two separate coil support elements, each connected by a radial rib to the bushing. Resonance of the coil support and the coil is suppressed by the separate coil support elements and the lossy connection therebetween.

Wide bandwidth linear motor system

A frequency agile magnetron employs an altitude compensation vacuum envelope external to the vacuum envelope of the magnetron. The tuning assembly of the magnetron includes a tuning plunger coupled through a first bellows assembly to one end of a tuning shaft. The tuning shaft is coupled at its opposite end through a second bellows assembly to the compensation vacuum envelope. When the two bellows assemblies are identical, atmospheric forces acting upon the tuning shaft are balanced at any altitude. Translation of the tuning assembly is provided by an actuator such as a linear motor coupled to the tuning shaft. Improved transfer of heat from the resonant cavity is provided.

Altitude compensation for frequency agile magnetron

Apparatus for high resolution sensing of the position of a rapidly moving member. The apparatus includes at least two linear variable differential transformers (LVDT's) each having a magnetic core coupled to the movable member. A signal source and a phase shifter provide energizing signals to the primary coil of each LVDT. The energizing signals have the same frequency but are phase shifted relative to each other. The induced secondary voltages of the LVDT's are sampled by synchronous detectors, the outputs of which are combined by an adder into a high resolution output signal. When two LVDT's are utilized, the energizing signals have a relative phase shift of 90.degree. and the effective position sampling rate is doubled. The apparatus can be used to sense the operating frequency of a tunable magnetron.

High resolution position sensing apparatus with linear variable

The cathode of a coaxial magnetron has a cylindrical electron emitter with a radially extending projection which is asymmetrical with respect to the axis of the emitter. The projection suppresses starting of the magnetron in the TE.sub.121 mode and reduces starting jitter. In a preferred embodiment, the projection is in the form of a circumferential ridge extending around approximately one-half the circumference of the cylindrical surface and is centrally located thereon. The projection is oriented at 45 degrees with respect to the output of the magnetron. The power output of the magnetron is not substantially reduced.

Coaxial magnetron with improved starting

A standard demountable coaxial magnetron has a cathode and a surrounding de shell formed with slots through which electromagnetic energy is coupled into an external resonant stabilizing cavity. The anode and its associated components are contained in a vacuum-sealed interaction cavity envelope separably mounted in the sleeve-like body of the stabilizing cavity. A ceramic window sealably covers the slots and has its axial ends coupled to the axial ends of the anode shell by kovar strips. Since various unwanted modes of oscillation, such as the TE.sub.121 mode, occur in the external resonant cavity, standard mode-suppression TE.sub.121 chokes are used. Such a choke includes a high rf loss absorber carried in a choke cavity formed between the cavity and the anode. However, the kovar strips also extend through this choke cavity and, in many cases, seriously interfere with mode suppression. A knitted gasket placed near the choke cavity entrance between the kovar strip and the anode shorts the kovar to effectively reduce its impedance and permit excitation of the absorber. The knitted structure provides a needed flexibility.

Mode control apparatus for a separable-insert coaxial magnetron

A magnetic circuit useful in crossed field tubes and the like. At least one permanent magnet assembly is provided which includes a high flux density magnet (as Alnico), a high coercive force magnet (as Samarium Cobalt) with an end area larger than the facing end of the high flux density magnet, and polarized oppositely thereto, and an iron transition member sandwiched between the two magnets. This isolates the high coercive force magnet and concentrates its flux. When used with a second such magnet assembly to create a high magnetic flux density in a gap therebetween, for example, in the interaction space of a crossed field tube, a higher flux density is achieved in the gap than would be the case utilizing the high flux density magnet alone within the available dimensional limitations. This is particularly so in an open magnetic circuit application having only a non-magnetic flux return path.

Open-circuit magnet structure for cross-field tubes and the like

In a coaxial magnetron the resonant circuit interacting with the electrons is coupled to a stabilizing resonator operating in a mode with circular electric field. The coupling is thru a set of slots in the intervening wall. Undesirable resonances localized in the slots are damped by lossy material at the ends of the slots. Undesirable damping of the cavity mode is prevented by a conducting shield covering exposed area of the lossy material and spaced into the cavity away from the slots.

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Andover, MA, United States of America

William A Gerard