Cyclotron autoresonance maser (CARM) amplifier experiments at 17 GHz

CARMs are attractive sources for applications such as electron cyclotron resonance heating of fusion plasmas and driving high-gradient RF linear accelerators. For applications such as accelerator drivers, amplifiers or locked-oscillators are required. A 17 GHz cyclotron autoresonance maser (CARM) amplifier experiment is presently underway at the MIT Plasma Fusion Center. This experiment uses an electron beam generated by the 500 kV injector on the SRL/MIT SNO-MAD II induction accelerator. The present gun geometry produces a beam at 400 kV in a 50 ns pulse. The amplifier is designed to operate in the TE
₁₁
mode. To date, only second and third harmonic relativistic gyro-TWT modes have been seen. The power levels of these modes are ~1 MW. We characterize these modes and discuss steps which we are taking in order to operate in the TE
₁₁
CARM mode. A high power, 17 GHz CARM amplifier has numerous applications. An RF injection electron gun is currently being designed at MIT that has RF input requirements quite comparable to the CARM amplifier's predicted rf output (see elsewhere in these proceedings). A potential high degree of phase stability may allow the CARM amplifier to serve as a driver for future high gradient linear e
⁺
e
^-
colliders.