All posts by Lawrence Ives

Load Reflector Assembly Completes Testing

Life testing of the reflector assembly for CCR’s 1.5 MW CW RF load assembly was terminated on January 3rd after operating for more than 410,000 cycles. The assembly was still operating satisfactorily when the testing was stopped. This is more than twice the expected lifetime for a load in operation at a gyrotron facility. The assembly is being disassembled to determine areas where the design can be improved. These improvements will be implemented to further improve the reliability of the device. The previous post provides a video of the assembly operating in the testing structure.

1.5 MW RF Load Reflector Testing

Testing has begun on the RF reflector drive system for CCR’s new, 1.5 MW CW, RF load for gyrotrons. The new design eliminates rotating seals and bearings. The reflector is mounted to a hollow shaft passing through a stainless steel bellows that supports the reflector and provides water cooling. An external motor swings the reflector around the waveguide launcher that delivers RF power to the load. The reflector sweeps the RF power around the load interior, preventing excessive power densities and standing modes inside the structure.
The new design meets specifications for ITER, the international fusion reactor now under construction in France. Approximately 24 loads will be required for the initial phase.
The video below shows life testing of the the reflector support assembly. A dummy cone on the shaft duplicates the weight of the copper, water-cooled cone that will be used in the actual load.

PPM-Focused Klystron completes bakeout

CLINAC following bakeout

CCR’s Periodic Permanent Magnet (PPM) focused klystron completed bakeout today. The tube is currently being prepared for high power testing at Communications & Power Industries, LLC. The klystron is being developed for a new generation of cancer therapy machines (CLINACs) produced by Varian Medical Systems, Inc.  The PPM-focused klystron would replace traditional solenoid-focused klystrons, reducing the size and weight of the system.

The klystron is designed to produce 5.5 MW RF pulses at 2.856 GHz at approximately 50% efficiency.  This development is funded by the U.S. Department of Energy through grant number DE-SC0007591.

Diamond Brewster Window Nearing Completion

Brewster Window

A major milestone was achieved in fabrication of the diamond Brewster window when the brazed diamond disk assembly was successfully welded into the stainless steel support structure. This was the final assembly step potentially stressing the diamond.
The diamond Brewster window is designed to transmit up to 1.5 MW of RF power continuously from 100 – 140 GHz. The window will be mounted in 63.5 mm diameter HE11 waveguide and forwarded to General Atomic for testing in the ECH transmission line at DIII-D. It will be tested using 110 GHz gyrotrons at the maximum power and pulse width available.
The window is compatible with the Direct Coupler developed by CCR for extracting RF power from gyrotrons in HE11 waveguide. The Direct Coupler and Brewster window would allow development of broadband, high-power, long-pulse/CW gyrotrons for electron cyclotron heating, parasitic more suppression, and current drive in tokamaks.
This program is funded by U.S. Department of Energy Grant DE-SC0006212.

Beam Optics Analyzer Version 6.3 Released

BOA x-ray device image

During the past several months, we’ve been extensively testing BOA beta version 6.3 and it is now ready for primetime. It uses the latest Simmetrix solid model and meshing libraries and the most recent DisLin plotting library for portability and implementation of UI interfaces. New features are listed below. More detailed information is available in the Release Notes at

New features in BOA v6.3 include:
• Option to use Inverse Cumulative Density Function technique for thermal effects in thermionic emission,
• More intuitive and simplified menu for beam optics display pane, especially for model background and symmetries,
• Models with built-in symmetries can now be specified.
• Both global and project level persistent preferences can be set via File, Options and View, User View Preferences, respectively,
• Parallel IO particle data are now available,
• Ability to plot images of power density from a 3D surface in either color or gray scale. Display power density on 3D surfaces in either color or gray scale,
• Plot emittances or brightnesses along a global or arbitrary axis.
• Injection of particles with arbitrary coordinates without specifying an injection plane in model. This is convenient for multipactoring ePIC simulations.

PPM-focused klystron ready for bakeout

PPM-Focused Klystron Seal-in
CCR’s Periodic Permanent Magnet (PPM) Focused klystron was sealed in on Friday and is now waiting for a bakeout oven. The tube is targeted for a new generation of cancer therapy devices. Elimination of solenoid focusing will allow a smaller package and downsizing of the medical equipment. The klystron is designed to produce 5.5 MW of pulsed RF power at 128 kV. A critical challenge was maintaining relatively high efficiency for a tube operating at high perveance. This klystron is a prototype and allows measurement of body current to determine beam transmission and includes tuners for several cavities. It will be tested at Communications & Power Industries, LLC, the industrial partner on this program. More information is available on the Research page .
This program is funded by U.S. Department of Energy Grant No.  DE-SC0007591.

Life testing initiated for corrosion mitigation coatings

Accelerated life testing of test structures was started in September to evaluate corrosion mitigation coatings for copper cooling channels. This is similar to life tests performed a couple of years ago that were very successful. Those tests used ethylene glycol and water as the coolant fluid. To more closely duplicate the conditions on Navy ships (recall this is a Navy-funded program), the coolant mixture includes salts to mimic seawater contamination. We’re also bubbling air into the coolant reservoir to oxygenate the water. There are seven coated samples and one uncoated control sample in the experiment. It’s anticipated that the experiment will be terminate in early December and the test samples analyzed. This will provide useful information on the effectiveness of different materials with varying thickness. More information concerning this research is available on the Research page.
This program is funded by U.S. Navy contract N00014-14-P-1198.

Life test setup