RESEARCH & DEVELOPMENT
Since 1999, CCR has been a leader in the development of advanced, innovative technologies for high power RF generation & transmission.
Research is in progress to develop high current multiple beam electron guns without beam compression. This is practical using Controlled Porosity Reservoir (CPR) cathodes, which can provide longlife operation with emission current densities exceeding 30 A/cm2. This is an order of magnitude higher than typically available from dispenser cathodes, allowing confined flow electron beams using flat magnetic fields in the gun.
Since 1999, CCR is the only commercial source of RF loads capable of dissipating more than 1 MW CW of RF power from high frequency gyrotrons. CCR is reducing the cost and improving performance using Additive Manufacturing, commonly referred to as 3D printing. CCR is teamed with N.C. State University and SD3D Inc., to 3D print copper and high strength plastics capable of high pressure and high thermal loads. The current effort is developing loads capable of dissipating up to 2 MW CW.
In 2003, CCR released the first, commercial, 3D, finite element, charged particle code capable of adaptive meshing and integral optimization. Countless upgrades and enhancements now make it one of the most advanced analytical tools of its kind. Beam Optics Analyzer (BOA) supports thermal and stress analysis and multiple generations of secondary electron emission. It’s used in the microwave tube and x-ray source industry to design the next generation of medical, defense, industrial, and scientific electron beam devices. CCR is developing techniques to dynamically refine localized meshes around beam bunches propagating in high energy accelerators.
The next generation of high energy linear accelerators, including the International Linear Collider and the Compact Linear Collider, will require RF sources producing 10 MW or more of RF power in millisecond pulses. The current RF source is the multiple beam klystron, which uses eight or more separate beams to generate sufficient beam power. These sources cost approximately $850K each. The annular beam klystron, if successfully developed, would provide the same operational performance at a cost less than $300K. CCR is continuing development of annular beam klystrons and is investigating an improved electron gun to increase performance.
RF power from gyrotrons is critical for heating fusion plasmas in fusion tokamaks in the search for an unlimited supply of electrical power. Gyrotrons produce one megawatt or more of RF power at frequencies exceeding 100 GHz. RF power at these frequencies and power levels require special transmission lines to reduce loss, and the devices that couple the gyrotron power into the waveguide cost $500K or more. CCR is developing technology to couple the power into the transmission line inside the gyrotron, eliminating the $500K coupler and reducing lost RF power. A prototype gyrotron is currently under construction.
Corrosion is a serious issue in copper cooling systems, particularly when high purity coolant is not available. This a serious issue for marine systems subject to saltwater contamination. With U.S. Navy funding, CCR and N.C. State University developed a system that applies a nano-scale ceramic coating to cooling surfaces to separate the copper from the coolant without impacting heat transfer. A system using Atomic Layer Deposition demonstrated that coolant system lifetimes could be increased by more than 300%. The Navy is currently qualifying the system for critical defense systems.
Magnetrons are perhaps the lowest cost, most efficient source of RF power. These devices, however, are oscillators, so there is no control of the phase, frequency, and amplitude. This prevents use for many applications, including accelerators, radar, and communications systems. CCR is working with SLAC National Accelerator Laboratory to address this issue. In 2019, CCR, in collaboration with Fermilab, successfully tested a 10 kW, 1.3 GHz magnetron system for driving superconducting accelerators. The current program is developing a simpler and more compact system using varactor diodes.
Klystrons are the RF source of choice for many systems, including radar, communications, and accelerators. The klystron is a well established RF source but lacks the efficiency required for many applications. Typical efficiencies range from 55 – 65%. CCR is building a 100 kW CW, 1.3 GHz klystron designed to operate at 80% efficiency. The RF circuit uses the core oscillation method (COM) to more effectively bunch the electron beam for RF power extraction. A prototype klystron is under construction.
Multipactor emission is a serious problem for vacuum windows transmitting MW levels of RF power. Multipactor results when high RF fields cause electron emission avalanche on the material surface. This is mitigated by a 10-15 Angstrom metal alloy coating to reduce secondary electron emission and dissipate electric charge. This coating is typically applied using hot wire sputtering, which works well for small structures, but is insufficient for larger ones. CCR is teamed with VaporPulse, Inc. and Ultramet to develop coating processes using Atomic Layer Deposition and/or Chemical Vapor Deposition. These new process will improve performance and treat structures up to 24 inches or more.
Inductive output tubes (IOTs) are highly efficient sources of RF power from a few hundred MHz up to 1.2 GHz. Efficiencies exceeding 80% are easily achieved, making them desirable for many applications where cost is important. Single beam IOTs, however, are limited to power level typically less than 30 kW. A number of important applications, such as waste treatment and water purification, required 200 kW or more of continuous power. CCR is developing a 700 MHz multiple beam IOT designed to produce 200 kW CW with an efficiency exceeding 80%. A prototype is scheduled for testing in spring 2022.