USA As Represented by Secretary of the Navy

John F Seely

Glenn Emerson Holland

Craig N Boyer

William R Hunter

A two-wire metal vapor vacuum arc (MeVVA) vacuum head includes an upper housing and a lower vacuum housing. The lower vacuum housing includes a plurality of ports, a vacuum space, and a first grid positioned in the vacuum space. A plurality of electrodes are positioned in the ports with a first end with an electrical contact area extending into the upper housing, and a second end extending into the vacuum space with an exposed electrical discharge area spaced from the first grid. An electrode of opposite polarity is positioned in one of the lower housing ports with a first end extending into the upper housing and a second end attached to the first grid. An extractor grid is positioned adjacent to the first grid, an electrode selector is operatively connected to the plurality of electrodes, and a trigger generator circuit is connected to an input of the electrode selector.

Metal vapor vacuum arc ion source

A trigger circuit is provided for a trigger system for a Marx generator column. The column includes a plurality of metal electrode pairs wherein the electrodes of each pair are spaced to form a spark gap therebetween and a capacitor is connected across each gap. The trigger system includes a three electrode (trigatron) spark gap switch forming the first spark gap of the Marx generator column. The triggering circuit includes a trigger transformer having primary and secondary windings. The secondary winding is connected through a connecting cable to a blocking capacitor of an input circuit of the trigatron switch. A charging capacitor is connected to an oscillator power supply so as to be charged thereby to the output voltage (e.g., 345 volts) of the oscillator power supply. An electronic switch (e.g., an SCR) is connected to a junction between the charging capacitor and the oscillator power supply for, when actuated by an input pulse, completing a connection between the capacitor and the primary winding of the trigger transformer so that a high voltage trigger pulse is produced at the secondary winding of the trigger transformer.

Trigger circuit for Marx generators

A dual-energy x-ray system is provided which is useful in densitometry and other applications. A dual energy x-ray source, formed field emission x-ray tube driven by a Marx generator, produces a single x-ray pulse of a very short duration (e.g., 10 to 200 nanoseconds). The pulse provides x-ray energy of a first, high value early in the pulse and x-ray energy of a second, lower value later in the pulse so as to provide a dual energy level x-ray distribution comprising hard and soft x-rays. A detector system having dual x-ray energy discrimination properties, formed by soft and hard x-ray detectors and an inter-detector, receives the x-ray pulse and discriminates between the dual x-ray energy levels of the pulse.

Dual energy x-ray densitometry apparatus and method using single x-ray pulse

A portable X-ray unit, of a relatively light-weight, occoping a volume of less then one-half a cubic foot containing an x-ray head assembly, a unique Marx generator, a plurality of spark-gap switches and control electronics is disclosed. The Marx generator allows for the development of a relatively high voltage in excess of 100 kV, yet allows for the discharge thereof within the nanosecond range. The Marx generator is enclosed by an acrylic insulator that cooperates with an aluminum enclosure, which functions as a return current path for the capacitors in the Marx generator and also as a shield against the escape of electromagnetic radiation from the pulsed x-ray unit. The Marx generator and spark-gap switches are confined within the pressurized chamber that may contain nitrogen gas to reduce the separation of the gap in the spark-gap switches.

Mobile X-ray unit

A mobile X-ray machine includes an improved Marx generator. The capacitors sed in the Marx generator are disc capacitors each having opposed side surfaces having electrodes formed thereon and each including a insulative coating provided on the peripheral edge thereof. The capacitors are mounted in slots in a support structure and are supported by spring contact members located within the slots. The spring contact members include spring arms which engage the electrodes on the opposed side surfaces of the associated capacitor. The spring contact members also include support elements from which are suspended the spherical electrodes of spark-gap switches individually associated with each of the capacitors.

Capacitor mounting arrangement for marx generators

A field emission X-ray tube is provided for use in a mobile X-ray machine. n evacuated ceramic housing having a convoluted interior shape for dissipating sparks surrounds the components of the field emission tube. A cathode and, an anode which emits x-rays, are located within the ceramic housing. A hollow anode tube is connected to the anode at one end and a vacuum pinch off element at the other end. Stray radiation is attenuated by a lead ring positioned inside of the ceramic housing.

Field emission tube for a mobile X-ray unit

An interference photocathode includes a reflective substrate and interference layers disposed on said reflective substrate for selectively enhancing a first photoelectric yield of said photocathode when irradiated by radiation having a first wavelength relative to a second photoelectric yield of said photocathode when irradiated by radiation having a second wavelength. In one embodiment, the interference layers include a dielectric layer having a wavelength dependent effective thickness disposed on said reflective substrate such that said effective thickness for radiation having said first wavelength is an odd multiple of a quarter of said first wavelength and said effective thickness for radiation having said second wavelength is an even multiple of a quarter of said second wavelength. In another embodiment, the dielectric layer includes a layer of electrically conductive material and a dielectric material disposed between said layer of electrically conductive material and said reflective substrate.

Interference photocathode

A mirror for reflecting radiation at a desired wavelength in the soft x-ray region, comprises a substrate and a coating on the substrate. The coating contains a first section and a second section. The first section comprises at least one layer made up of at least a spacer sublayer and a nodal sublayer. The optical thickness of each spacer sublayer is selected so that, upon application of the radiation of desired wavelength, the mirror generates a standing wave having a node in the middle of each nodal sublayer. The second section is disposed between the first section and the substrate, and comprises a plurality of optically absorptive layers.

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Alexandria, VA, United States of America

John F Seely