Varian Associates

About: Varian Associates is a based out in . It is known for research contribution in the topics: Beam (structure) & Wafer. The organization has 2160 authors who have published 2591 publications receiving 46002 citations.

10 KW and up from a helix TWT

Abstract: It is well known that wideband helix traveling wave tubes have been limited to peak power levels of several kilowatts, due to the occurrence of backward wave oscillations (BWO). Continuing advancements in TWT technology, however, have made this restriction a thing of the past. Octave bandwidth TWTs have been developed using helix pitch steps, diameter steps, or resonant loss for BWO stability. It would appear that peak power levels in excess of 50 kW are possible by using a combination of these approaches. This paper will first discuss the design and present performance data of a high peak power 10 kw, octave bandwidth, PPM-focused, conduction-cooled, helix TWT, in which "resonant loss" is the only oscillation suppression technique employed. Secondly, by extending this basic tube design, it will be shown that higher peak power levels can easily be achieved.

Potential for localized, adjustable deep heating in soft-tissue environments with a 30-beam ultrasonic hyperthermia system.

Abstract: Initial heating rates (°C/min) along parallel tracks at depths of 1–14 cm in a static, muscle-like phantom were determined from time-temperature profiles obtained with 'Helios', a 30-beam ultrasonic hyperthermia system developed by Varian Associates. Data were taken at a single operating frequency of 556 kHz, for different sets of focal plane ring diameters of the four-ring array applicator, different levels of transducer driving power and two different focal plane depths, 6 cm and 9 cm. In each experiment, at each point of temperature measurement, analysis of temperature versus time data over a 2 min heating interval permitted separation of the desired phantom heating from artefactual heating resulting primarily from absorption of transverse (shear) waves produced at phantom-metal probe catheter interfaces. The results of the studies conducted suggest that in a non-translating carriage mode, Helios can produce axially and laterally localized deep heating in soft tissues for tissue volumes of lateral dime...

TWT Slow-wave structure assembled from three ladder-like slabs

Abstract: This invention concerns a slow-wave circuit which is electrically equivalent to the well-known folded-waveguide or coupled-cavity circuit with staggered coupling slots. The central portion of the circuit is a metallic ladder. The ladder rungs are wide and flat to form the equivalent of flat cavities. The rungs have axially aligned holes thru their centers for beam passage. A pair of coupling ladders are joined to opposite sides of the central ladder. They have apertures or recesses spaced at twice the pitch of the central ladder; the recesses are aligned to provide a coupling duct between each pair of adjacent cavities, and cavity-closing walls at the ends of the pair. The coupling recesses in the two coupling ladders are staggered by the cavity pitch so that the coupling ducts are on alternating sides of the cavities.

Numerical simulation of drive induced oscillation in coupled cavity traveling wave tubes

Abstract: Computer analysis of Drive Induced Oscillation (DIO) requires a large-signal program which does not restrict itself to treating disturbances which propagate at a single frequency or at a number of related frequencies, known in advance This paper describes a numerical model which handles relativistic, electromagnetic, and nonlinear effects in such a way as to achieve a full transient analysis of the coupled cavity traveling wave tube >