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Vacuum Electron Devices Laboratory

The Vacuum Electron Devices Laboratory is currently developing systems in the field of microwave vacuum electron devices and microplasmas.

Vacuum Electron Devices

Vacuum electron devices are used in a variety of applications from communications to radar systems to medical imaging. These devices require an electron source for operation. A thermionic cathode is often used as the electron source, but these sources have some drawbacks in terms of power requirements, size, and spatial control. One possible replacement for the electron source is gated field emitter arrays. The lab research studies methods of introducing field emission arrays into Microwave Vacuum Electron Devices (MVEDs) in order to improve device performance.

Image of crossed-field amplifier

Crossed-Field Amplifier Experiment

 

Current Research

The Vacuum Electron Devices Laboratory has several ongoing projects related to MVEDs including the development of a Smart Crossed Field Amplifier and a Faceted Cold Cathode Magnetron. In addition, research is ongoing in the use of electron hop funnels for improving the performance of field emission arrays.  The laboratory also has a research project in the use of micro-plasmas for analog circuit components.

Smart Crossed-Field Amplifier

The smart crossed-field amplifier (CFA) project  uses a 1 GHz linear format CFA that incorporates gated vacuum field emitter arrays (FEAs) as a distributed electron source. The FEAs are placed below the sole electrode and provide the current to the device. FEAs can be addressed allowing spatial and temporal control of the injected current. This ‘smart’ device would monitor RF power input, power output, and current collected on the segmented collector and would be able to dynamically change the spatial location of injected current to optimize the operation of the device.

Image of smart crossed-field amplifier

Faceted Cold Cathode Magnetron

The goal of this project is to build a section of a magnetron device using field emission cathodes as the electron source. A vacuum chamber test system has been developed and is being used for testing. The magnetron structure has been modeled by collaborator NumerEx, Albuquerque, NM using the Air Force Research Laboratory particle-in-cell code ICEPIC.  Our group has modeled the field emission electron current injection using the two-dimensional particle trajectory simulation Lorentz2E. Additional research at BSU includes the magnetron modeling with the particle-in-cell code VORPAL from Tech-X. For the particle trajectory modeling the cathode has a distributed structure comprised of field emitters instead of the traditional thermionic cathode. The cathode is designed with facet plates with slits to protect the emitters. The device being modeled is a 10 cavity rising sun magnetron.

Image of animated faceted cold cathode magnetron

image of faceted cold cathode magnetron

Capabilities

The Vacuum Electron Devices Laboratory focuses on all aspects necessary to develop, test, and improve the operation of microwave vacuum electron devices. Capabilities of the lab include vacuum system development and operation, RF design and testing, high voltage systems, control system development, and mechanical design.

Vacuum Systems

With a total of three vacuum chambers both high and ultrahigh vacuum can be achieved. These chambers include a variety of ISO flange systems for rapid experimentation and conflat only chambers with heating systems for ultrahigh vacuum. Current work also includes the incorporation of gas sources to all chambers including nitrogen for venting, argon for plasma studies, and hydrogen for ion back bombardment lifetime testing.

 

Image of magnetron test chamber

Magnetron Test Chamber

Vacuum pumping systems include the use of diaphragm, turbo, and ion pumps as well as heating systems. For pressure measurement ion gauges, convectron gauges, and residual gas analyzers are used.

RF Design and Testing

RF circuits are used in some projects in the Vacuum Electron Devices Laboratory. All of the circuits currently in use have been developed and partially fabricated within the lab. Laboratory equipment for RF design and testing includes spectrum analyzers, network analyzers, signal generators, a broadband RF amplifier (0-50 W, 400 to 1000 MHz), directional couplers, isolators, and a 250W matched load. Additional laboratory equipment includes oscilloscopes, multi-meters, HV power supplies, and soldering stations to build and troubleshoot laboratory electronics.

High Voltage Systems

High voltage systems are used extensively in the lab including a 5kV/400mA and a 25kV/200mA power supply and various high voltage DC to DC converters.

Image of high voltage systemThe operation of the high voltage systems also includes all the necessary safety systems to keep all operators and equipment safe. This effort includes the incorporation of safety interlocks, isolation systems for device protection, and hardware to control and monitor high voltage operation. In addition the laboratory is equipped with high voltage probing equipment for testing.

The lab also incorporates high current systems to operate the electromagnets necessary to operate the devices. These high current systems include 100A/30V and 180A/55V power supplies.

 

Control System Design

Image of control system on computer monitorTo operate all equipment necessary to maintain and operate the vacuum electron devices, control systems have been developed to monitor, control, and perform data acquisition. All of the control systems are developed using National Instruments (NI) LabView Software. In addition to NI hardware, custom hardware has been designed, developed, and constructed to supplement the system. Using this type of system, the entire experiment can be centrally controlled via a single computer.

 

Mechanical Design

Image of mechanical design From electro magnet design to experiment support structures, the Vacuum Electron Devices Lab designs and fabricates a wide array of mechanical designs. Design capabilities include CAD drawing using SolidWorks, fabrication, and cooperation with fabrication companies. Specific specialties include voltage isolation structures, cooling systems, and vacuum chamber configurations.

Laboratory Members

Current members of the Vacuum Electron Devices laboratory include:

  • Undergraduate Students:  Eric Wright, Brian McMillon, Matthew Dolan, Kyle Straub, Alfredo Bravo-Iniguez, Brooke Garner, and David Mullner
  • Master’s Students: Tyler Rowe
  • PhD Students: Marcus Pearlman,  Sulmer Fernandez Gutierrez

The faculty responsible for this laboratory is Prof. Jim Browning

 

Sponsorship

The Vacuum Electron Devices Laboratory is part of Department of Electrical and Computer Engineering (ECE) at Boise State University. Research is being funded by the Air Force Office of Scientific Research and the ECE Department

Relevant Publications

J. Browning and J. Watrous, “A faceted magnetron concept using field emission cathodes,” J. Vacuum Science and Technology B, Vol. 29,  March/April (2011).

C. Lester, J. Browning, and L. Matthews, “Electron hop funnel measurements and comparison with the Lorentz-2E simulation”, IEEE Trans. on Plasma Sci., Vol. 39, No. 1, pp. 555-561, Jan. (2011)