Science Applications International Corporation

Linac Systems, LLC

Other

Donald A Swenson

Wayne Douglas Cornelius

Phillip E Young

William J Hoffert

W Joel Starling

An interdigital (Wider&#xf6;e) linear accelerator employing drift tubes, and associated support stems that couple to both the longitudinal and support stem electromagnetic fields of the linac, creating rf quadrupole fields along the axis of the linac to provide transverse focusing for the particle beam. Each drift tube comprises two separate electrodes operating at different electrical potentials as determined by cavity rf fields. Each electrode supports two fingers, pointing towards the opposite end of the drift tube, forming a four-finger geometry that produces an rf quadrupole field distribution along its axis. The fundamental periodicity of the structure is equal to one half of the particle wavelength &#x3b2;&#x3bb;, where &#x3b2; is the particle velocity in units of the velocity of light and &#x3bb; is the free space wavelength of the rf. Particles are accelerated in the gaps between drift tubes. The particle beam is focused in regions inside the drift tubes.

Radio frequency focused interdigital linear accelerator

A linear accelerator of the interdigital (Wider&ouml;e) type, employing two-part drift tubes and associated support stems that couple to the electromagnetic fields of the interdigital linac structure, creating rf quadrupole fields along the axis of the linac to provide transverse focusing for the particle beam. Each two-part drift tube comprises two separate electrodes that operate at different electrical potentials. Each electrode supports two fingers, pointing inwards towards the opposite end of the drift tube, forming a four-finger geometry that produces an rf quadrupole field distribution along its axis. The fundamental periodicity of the structure is equal to one half of the particle wavelength &bgr;&lgr;, where &bgr; is the particle velocity in units of the velocity of light and &lgr; is the free space wavelength of the RF. Particles are accelerated in the gaps between drift tubes. The particle beam is focused in the regions inside the drift tubes.

A source wire is in the path of a neutral particle beam formed from positively and negatively charged particles (ions) and neutral particles (atoms). The source wire strips electrons from the negatively charged particles to neutralize these particles and strips electrons from the neutral particles to create positively charged particles. A magnetic field is perpendicular to the path of the particle movement. A detector wire downstream from the source wire detects the total particle flux. A magnetic field is perpendicular to the path of the particle movement. A variation, preferably cyclical, may be provided in at least one of (a) the characteristics of the magnetic field and (b) the positioning of the detector wire relative to the source wire in a direction perpendicular to the magnetic field and the particle movement. The resultant signal produced on the detector wire by the combined action of such magnetic field and/or detector wire movement is processed to indicate the characteristics, including direction, divergence and scattering of the neutral particle beam in a first direction. Second source and detector wires disposed in a direction respectively perpendicular to the first source and detector wires may be subjected to a second magnetic field perpendicular to the first magnetic field and to the particle path to determine the characteristics, including direction and divergence and scattering of the neutral particle beam in a second direction perpendicular to the first direction. A grid of source and detector wires may also be disposed in the first and second directions to enhance the indications of the characteristics, including direction, divergence and scattering, of the neutral particle beam in the first and second directions.

Apparatus for, and methods of, detecting the direction and focal

A drift tube linac incorporates rf-electric quadrupole focusing by employing drift tubes with only one drift-tube stem per particle wavelength and in which the lowest frequency RF cavity mode has a transverse magnetic field (TM.sub.010 -mode). Each drift tube comprises two separate electrodes that form a capacitor that couples to the axial electric field of the primary cavity mode. The electrodes operate at different electrical potentials, as determined by the RF fields in the cavity, and are supported by a single stem along the axis of a cylindrical cavity. Each electrode supports two fingers pointing towards the opposite end of the drift tube, forming a four fingered geometry that produces an RF quadrupole field distribution along its axis. The fundamental periodicity of the structure is equal to the particle wavelength (.beta..lambda.) where .beta. is the particle velocity in units of the velocity of light and .lambda. is the free space wavelength of the rf. The particles traverse two distinct regions, namely the gaps between drift tubes, where the acceleration takes place, and the regions inside the drift tubes, where the RF focusing takes place. The linac of the present invention transforms the reverse fields into transverse fields for focusing such that the beam is not decelerated.

Radio frequency focused drift tube linear accelerator

A radio frequency quadrupole (RFQ), which is a combination of the standard 4-vane and 4-rod designs, with a window or windows cut through mid-portions of the normally solid vanes. The windows decrease the resonant frequency, minimize undesirable mode coupling in the RFQ and result in a smaller and more easily tuned accelerator.

Segmented vane radio-frequency quadrupole linear accelerator

A new RFQ linac structure extends the useful range of beam velocity by a factor of 2 to 4 and beam energy by a factor of 4 to 16. Four-finger electrodes extend into each accelerating cell and provide quadrupole focusing of beam particles along a beam axis. The finger electrodes of adjacent cells also provide quadrupole acceleration of the beam particles along the beam axis. The finger of adjacent cells are oriented in accordance with a prescribed pattern. The pattern orientation of the fingers provides an additional degree of freedom that allows the periodcity of the focal structure to be independent of the periodicity of the accelerating structure. This makes it possible to double the rf frequency periodically to enhance the acceleration rate while holding the focusing strength constant.

Four-fingers RFQ linac structure

A close-coupled rf power system provides high peak rf power for a linear accelerator, or 'linac', and other charged particle systems. The linac operates in a vacuum housing. Low level rf power is coupled inside of the vacuum housing by a conventional rf feedthrough connector. An input resonator cavity mounts on the side of the linac within the vacuum housing. The resonator cavity couples rf power to one or more amplifier assemblies, each including at least one planar triode mounted directly on the linac housing, proximate one end of the resonator cavity. The planar triode, in turn, generates a high power rf current at its respective anode. The high power rf current couples to the linac through a conductive loop operating at the anode potential. Anode cooling is provided by pumping a suitable fluid, such as de-ionized water, through the conductive loop. The high power rf current in the loop generates magnetic fields in the linac required for its operation. After passing through the loop, the rf current is shunted to ground through an integral rf-bypass capacitor. Many components of conventional rf power systems, such as rf output resonators, transmission lines, and vacuum windows, are not needed. Peak rf power of up to 1 megawatt is achievable by using clusters of planar triodes in each amplifier assembly, and by using multiple amplifier assemblies.

Close-coupled RF power systems for linacs

A beam emittance measuring apparatus suitable for use with small diameter beams of the type commonly found in accelerators and beam transport systems. The apparatus includes a U-shaped frame that supports four thin wires that traverse the particle beam to create and detect thin particle shadows in the particle distribution. Two of the wires are shadow wires and are supported on one side of the U-shaped frame. Two of the wires are detection wires and are supported on the other side of the U-shaped frame, downstream from the shadow wires. One shadow wire and its corresponding detection wire are positioned to detect emittance data at a given point in a first emittance plane. The other shadow wire and its corresponding detection wire are positioned to detect emittance data at a given point in a second emittance plane. A given shadow wire and its corresponding detection wire are generally at right angles to each other so that the point of insertion defines the point at which the emittance measurement is made, much as the cross-hairs on a sighting device define a point being sighted. The location of the particle shadow on the detection wire provides a measure of the emittance angle of the particular beam particle whose shadow is cast by the shadow wire. The location of the particle shadow on the detection wire is detected optically using a concave mirror mounted in one side of the U-shaped frame that collects the image of the detection wire and focuses it on a segmented detector mounted in the other side of the U-shaped frame.

Wire shadow emittance scanner

A plane wave transformer linear accelerator structure for accelerating charged particles to velocities greater than one-half the speed of light. The accelerator includes a tank section having a generally cylindrical tank wall. End plates each containing a central aperture for accommodating the passage of a charged particle beam are positioned adjacent to the ends of the tank wall. Support rods extend between the end plates, partially defining at least one axially-extending outer cavity and at least one axially-extending inner cavity. A plurality of axially-spaced washers situated substantially on the central axis of the tank section are supported by the rods. The washers each have central apertures which together define a charged particle beam acceleration path through the tank section.

Plane wave transformer linac structure

A coupled-cavity linear accelerator for accelerating charged particles to velocities greater than about one-third the speed of light. The accelerator includes a first tank for accelerating charged particles at a first velocity to a second velocity and a second tank for accelerating the particles to a higher third velocity. A bridge coupler for focusing a beam formed by the charged particles joins the first and second tanks. Each tank is substantially symmetrical about an axis and includes a generally cylindrical tank outer wall having an inner surface and an outer surface. A series of axially spaced disks are positioned inside the tank and bear on the inside tank surface. Each disk has an outer diameter greater than the as-manufactured inside diameter of the tank wall so that each disk causes an annular indentation in the inner surface of the outer wall. At least one washer is supported by each of alternating disks. These washers have central apertures which together define a particle beam acceleration path through the tank. Methods of fabricating the linear accelerator and of tuning it are also disclosed.

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Albuquerque, NM, United States of America

Donald A Swenson