CALABAZAS CREEK RESEARCH, INC. — Department of Energy SBIR Phase II: 21b

Description

Current high power gyrotrons for plasma heating use an internal launcher and multiple mirrors to generate a Gaussian output beam that exits the tube through a large diamond window.A Mirror Optical Unit (MOU) external to the gyrotron is required to transition the Gaussian beam into an HE11 mode in corrugated waveguide for transmission to tokamaks.The internal mirrors and large diamond window costs approximately $200K.The MOU costs approximately $150K to build with additional cost of $250K per year from lost RF power.A more cost effective and efficient approach is required for transitioning gyrotron power into transmission lines.Calabazas Creek Research Inc.(CCR) developed a coupler to transition the gyrotron RF power into corrugated waveguide inside the tube using an internal (direct) coupler.This eliminates internal mirrors costing approximately $60K and reduces the diamond window cost by approximately $100K.It also eliminates the MOU and its associated cost.A direct coupler was designed for a long pulse gyrotron at General Atomic that is no longer operational due to an electron gun failure.The coupler is forecast to provide 97% HE11 mode purity with 1% loss from the launcher to the output waveguide.Current MOUs provide less than 96% more purity with losses from the gyrotron and MOU exceeding 4%.The direct coupler will replace the existing Gaussian mode system.The Phase II program will rebuild the long pulse gyrotron, replacing the electron gun, output window, launcher, and multi-mirror output coupling system.Funds are also available to replace the collector if warranted.The direct coupler designed in Phase I will be installed, and the gyrotron will be rebuilt, processed, and tested at high power and long pulses to confirm the performance.Gyrotrons are used for heating plasmas in tokamaks in Europe, Russia, Korea, Japan, China and the U.S.This technology would find worldwide application for future ECH power sources for fusion energy research.