CCR is making good progress in assembling a 100 kW RF magnetron RF source system with phase and amplitude control. This will provide lower cost RF power than currently available from klystrons, with a significant increase in efficiency. The system uses a phase modulated locking signal to provide amplitude control when driving high Q accelerator cavities. The initial test will determine the magnitude of the RF signal required to lock the magnetron. This will provide information to replace the existing klystron driver with a solid state driver.
The system consists of the magnetron, circulator, RF driver, coolant system, PLC-based interlock system, driver power supply, and diagnostic instrumentation. It is anticipated the system will be completed near the end of July with high power testing scheduled for mid-August. Following tests at CCR, the system will be tested with a superconducting cavity at Fermi National Laboratory . CCR intends to market this system as an economical source of RF power for superconducting accelerators.
CCR’s 1.5 MW CW Brewster Window is currently being tested at General Atomics using a gyrotron at the DIII-D tokamak facility. The window is installed in transmission line between the Mirror Optical Unit (MOU) and high power load. The tests are characterizing the performance, including reflection and potential mode conversion and will eventually transmit the highest RF power level available from the gyrotron. Cameras will look for arcing and power deposition in the CVD diamond window. Testing will continue for the next couple of months, depending on availability of the gyrotron and associated power supplies. Test results will be presented at the IR & MM-Wave Conference in Copenhagen in September.
Calabazas Creek Research, Inc. shipped a 125 kW, C-Band klystron with 18 beams. This is the culmination of an 18-month development program to build a wide-band, low voltage klystron. The tube operates at 25 kV with a bandwidth exceeding 6%. It uses controlled porosity reservoir cathodes and includes an extended interaction output cavity. The klystron is currently being installed for high power testing at the customer’s site.
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.
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.
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.
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.