Robert Mitchell Wheat

Wideband RF Structure for Millimeter Wave TWTs

LANL has developed a new vane loaded waveguide RF structure for a sheet electron beam traveling wave tube (TWT). The goal was to create a new class of wideband RF structures that allow simple mechanical fabrication and have geometry suitable for interaction with sheet electron beams. We have concentrated on structures at 94 GHz. We have achieved 6% bandwidth and believe that 10% is possible. We have performed 3D electromagnetic simulations using the codes Microwave Studio and HFSS, and fabricated several aluminium cold models of RF structures at 10GHz to confirm the design. Agreement between the 10 GHz cold test data and computer simulations was excellent. An RF structure at 94GHz was fabricated using electrical discharge machining (EDM) with a 0.004 inch wire and cold tested.

Design and Application of a Diode-Directed Solid-State Marx Modulator

Researchers at Los Alamos National Laboratory (LANL) are developing a new solid-state high-voltage Marx modulator for the generation of pulsed power. The initial application of the LANL modulator is to provide power to a magnetron that requires a 46-kV, 160-A, 5-mus rectangular pulse. This modulator technology is also being developed for other applications, including portable millimeter wave sources, a beam energy corrector for induction accelerators, and space-based power systems. The LANL solid-state modulator has several benefits, including wave shape control, switch protection, efficiency, and compactness. The present paper describes this source technology and its design.

Performance of a Diode-Directed Solid-State Marx Modulator

The diode-directed solid-state Marx modulator is a new high-voltage modulator developed at Los Alamos National Laboratory (LANL) to drive a high-power magnetron. In its normal mode of operation the modulator produces 46-kV, 160-A, 5-mus rectangular pulses at 50 Hz. The modulator is also capable of running in burst mode and generating arbitrary waveforms at full voltage. The current paper describes modulator testing and performance results. Also shown are several of the unique features of this design, such as pulse width variability, wave shape variability, and switch protection.

Design of High‐Power, MM‐Wave Traveling‐Wave Tubes

Simulations have indicated that emerging electron sheet‐beam technology can drive simple rippled and stepped waveguide traveling‐wave tubes with extremely high gain. There are many design possibilities that need to be evaluated. The interaction can be made with the n=−1 (backward wave), n=0 (fundamental forward wave), or n=+1 (first space harmonic forward wave) interactions. In this paper, we discuss some of the fundamental design issues.

Multiple output timing and trigger generator

In support of the development of a multiple stage pulse modulator at the Los Alamos National Laboratory, we have developed a first generation, multiple output timing and trigger generator. Exploiting Commercial Off The Shelf (COTS) Micro Controller Units (MCUs), the timing and trigger generator provides 32 independent outputs with a timing resolution of about 500 ns.

Sheet Beam Development for mm-Wave Microwave Tubes at Los Alamos National Laboratory

Currently ongoing at Los Alamos National Laboratory is a program to develop high-power, planar 100-300 GHz traveling-wave tubes (TWTs). The promise of planar TWT technology is: 1) the radio-frequency (RF) structures lend themselves well to established micro-fabrication techniques: and 2) by spreading the electron beam in one dimension, we effectively eliminate the beam self force and can transport a high net beam current, resulting in very high-power devices. An enabling technology for this effort is a sheet electron beam source

Secure Chaos Communications Using Driven Traveling Wave Tube Amplifiers with Delayed Feedback

A new method of RF communications with inherent security has been demonstrated at Los Alamos using chaos masking. In the past several years many papers have described this secure chaos concept theoretically but LANL has the first operating prototype communications system. This chaos communications method is similar to spread spectrum techniques. The chaos masking of a transmitted signal is created by operating a non-linear amplifier (TWT) in saturation with controlled feedback. The system receiver uses an identical TWT that de-codes the chaos masking similar to the correlation methods of a spread spectrum receiver

A 120kV IGBT modulator for driving a pierce electron gun

An IGBT modulator has been developed to drive a 120 kV, 23 A Pierce electron gun. The modulator is capable of producing pulses up to 10 mus in width at repetition rates up to 10 Hz with no active reset. The pulse rise time on the electron gun will be approximately 2 mus and the remaining 8 mus of flattop is tuned to have a ripple of less than 1 percent rms. The modulator technology was developed from a previous 50 kV prototype. The modulator consists of six boards, each with one EUPEC IGBT that drives a single common step-up transformer wound on METGLAS 2605 SC cores. The six transformer cores share a common bifilar output secondary winding. The modulator uses a fiber optic trigger system and has a high voltage cable output with an epoxy receptacle on the oil end and a ceramic receptacle on the vacuum end. The 120 kV electron gun was manufactured by MDS Co. and will be used to generate sheet electron beams from the standard pencil beam produced by the Pierce electron gun

Multiple Flow Loop SCADA System Implemented on the Production Prototype Loop

The following report covers FY 15 activities to develop supervisory control and data acquisition (SCADA) system for the Northstar Moly99 production prototype gas flow loop. The goal of this effort is to expand the existing system to include a second flow loop with a larger production-sized blower. Besides testing the larger blower, this system will demonstrate the scalability of our solution to multiple flow loops.

Production Facility SCADA Design Report

The following report covers FY 14 activities to develop supervisory control and data acquisition (SCADA) system for the Northstar Moly99 production facility. The goal of this effort is to provide Northstar with a baseline system design.