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.
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 http://calcreek.com/products/software/.
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.
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.
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.
CCR is nearing completion of its photocathode fabrication chamber. The main chamber was assembled and baked in March. The vacuum suitcase was assembled and is currently being baked. Figure 1 shows a photo of the chamber with the suitcase attached.
During the next couple of weeks we’ll be installing the support for the sputtering source and the internal support for the photocathode being processed. We also need to mount the laser and connect the picoammeter. We had a small setback when problems arose with our turbo pump. That’s now been replaced, and we’re moving forward again.
We’ll first fabricate cesium antimonide photocathodes. The antimony source will be installed in the next couple of weeks. We still need to assemble the first test photocathode with parts in stock. I’m hoping we can fabricate our first cathode by the end of November.
This program is funded by U.S. Department of Energy Grant No. DE-SC00009583.
The U.S. Navy funded the Phase I Option of CCR’s program to use innovative coatings to suppress arcing in electron guns and reduce or eliminate corrosion in RF systems deployed in the fleet. The corrosion occurs in copper coolant channels in RF sources and solenoids due to excess oxygen and salts in the coolant.
CCR is developing coatings to prevent coolant channel corrosion in collaboration with N.C. State University. This follows highly successful life test studies that demonstrated coolant channel lifetime could be increased more than 500% using a nanometer-scale coating of ceramic. The coating is applied by flowing a sequence of gases through the device’s cooling system. Figure 1 shows the setup to coat a TWT collector. It is anticipated the coating will be added prior to final device tests. The process would be applicable to any fluid cooled device where high quality coolant is not available.
The arcing issue arises in klystrons following weeks or months of stand-by operation. The sudden application of high voltage creates spurious electron emission from the focus electrode, immediately taking the system off-line.During the next few months, CCR and N.C. State University will test the process on the cooling circuit of a solenoid manufactured by Arnold Magnetic Technologies.
CCR is investigating coatings that preferentially react with oxygen. This program will determine if coatings of carbon, titanium carbide or tantalum carbide will absorb the oxygen and prevent barium oxide formation. High voltage tests are planned during the next few months using CCR’s cathode test chamber (Figure 2).
R. Lawrence Ives, Ph.D.
Dr. Ives received his Ph.D. from N.C. State University in plasma physics and began his microwave career in the Gyrotron Department at Varian Associates, Inc. in Palo Alto, CA. In that position he was responsible for designing electron guns, gyrotron circuits, collectors, and waveguide components. Gyrotrons are high power, high frequency microwave and millimeter wave RF sources used for fusion research and industrial heating.
Dr. Ives founded Calabazas Creek Research, Inc., which is involved in software development, microwave tube and component design, and uses of microwave power for environmental and heating applications.
Dr. Ives was principle investigator in programs to develop a two-stage depressed collector system for Gaussian-mode gyrotrons at the 2 MW CW power level, S-Band multiple beam electron gun for radar applications, a MW CW waterload for Gaussian mode gyrotrons, and a 15 kW CW L-Band klystron for Driving Superconductor Accelerator Cavities.
Dr. Ives is currently principle investigator on the following programs to implement field emission array cathodes into RF sources, multiple beam electron guns for high power RF applications, improved magnetron injection guns for high power gyrotrons and gyroklystrons, a 50 MW multiple beam klystron, a microfabricated W-Band Traveling Wave Tube for satellite communications, and Terahertz backward wave oscillators.
Dr. Ives also provides consulting support to several commercial companies on electron gun and RF source development.
Prior to founding CCR, Dr. Ives was manager of Varian's High Power Klystron department, responsible for overseeing klystron design and development from S-Band through X-Band. He was responsible for managing and upgrading the computational facility, which supported four divisions and was recognized as the most powerful and advanced in the microwave industry. He was responsible for implementing Computer Integrated Manufacturing (CIM) techniques, including interfacing CNC machines to the engineering system. Dr. Ives returned to a more technical role as Senior Engineer, supporting research in both the klystron and gyrotron areas. In that position he managed development programs for high power CW klystron amplifiers; high voltage, high current electron guns for research purposes; and ultrahigh power window designs for klystrons. Dr. Ives developed the first commercial gyrotron capable of operation with a depressed collector. He also designed the output window and waveguide system for an experimental, 200 MW, X- Band klystron using advanced scattering matrix and mode matching computer techniques.