Moritz Pilossof

Gyrotron With Dual Electrode Ferroelectric Cathode Operating at High Repetition Rate and Long Pulse

A gyrotron based on a ferroelectric cathode with dual front electrodes has been experimentally studied, and the results are reported. The two electrodes are triggered separately with complementary timing. During operation when plasma is forming on one of the electrodes, the other undergoes a relaxation process and vice versa. A pulse repetition rate of ~ 3 MHz with a 50% duty cycle was obtained from each electrode, reaching an overall 100% duty cycle, forming a continuous ~ 7-μs current pulse. This configuration has the potential to extend the pulse duration toward continuous operation. The cathode was used as a source for a 25-GHz gyrotron generating a ~ 7-μs radiation pulse.

Note: A 95 GHz mid-power gyrotron for medical applications measurements

A mid-power 95 GHz gyrotron was built and used for measuring insertion loss of biological tissue. The gyrotron is a compact table-top device that allows convenient measurements in a biological setup. It operates at the fundamental harmonic with TE02 circular mode. A mode converter is used to obtain TE10 rectangular mode in standard WR10 components. Using this gyrotron, beef tissue insertion loss was measured to be about 7-8 dB per millimeter.

Experimental Study of 50-kV/3.5-A Hollow Electron Beam Produced by Ferroelectric Cathode

An annular electron beam emitted from a flat ferroelectric cathode is demonstrated in this paper. The cathode with a pierced ring-shaped front electrode was operated in two different electron gun setups. In the first electron gun, the cathode was operated in low voltages and under different magnetic fields. The beam shape was photographed, and the beam radii were controlled by the magnetic field. In the second electron gun, with a high voltage of 50 kV, an annular beam was also obtained, with a current of ~3.5 A. The configuration presented here may be the basis for an annular electron beam source for a gyrotron.

Frequency-Replaceable Ferroelectric Cathode Gyrotron for the Entire Ka-Band Using Replaceable Resonator

A modular, mid-power, Ka-band frequency (27-40 GHz) gyrotron is reported. The gyrotron is known as a dominant tube for millimeter waves, but once fabricated its frequency changing is limited. In this paper, a gyrotron with a replaceable resonator was designed and built. By a rather simple action of resonator replacement, the operating frequency of the gyrotron can be replaced. The use of a ferroelectric cathode supports a quick opening and closing of the tube for the resonator replacement in less than half an hour. With the view of covering a wide range of frequencies, a wide range magnetic field pulsed copper solenoid was designed, supporting the gyrotron operation on either the fundamental or the second harmonic of the electron-cyclotron frequency. The gyrotron design is based on a ferroelectric electron gun designed and built to provide the appropriate electron beam to a wide variety of resonators, operating at the fundamental or at the second harmonic. The gyrotron with two differently designed resonators has been constructed and tested in the TE01, TE21, and TE11 modes at 39, 31, and 27 GHz, respectively. With an accelerating beam voltage of ~35 kV and a beam current of ~1-1.7 A, an output power of ~1-6 kW was obtained at single pulse and at ~200-ns micropulse in ~6-μs macropulse with ~25% duty cycle. In addition, the system was operated with 5-s repetition rate for half an hour, and a high stability was measured for all the mentioned frequencies.

Ferroelectric Cathode Electron Emission Dependence on Magnetic Field

Many experiments on microwave and millimeter wave tubes, which are based on ferroelectric (FE) cathodes include a magnetic field in the emission region. For such electron devices, an optimal magnetic field leads to overall performance enhancement. In this paper, the dependence of the electron emission from an FE cathode on the magnetic field is experimentally examined and presented. The electron current emitted from an annular FE electron gun, suitable for gyrotron tubes, was measured with different magnetic fields. It was found that adding magnetic field extends the emitted current until a maximal working point is reached. Magnetic field above this point reduces the emission. A ~20 % enhancement in the emitted current relative to the emission in the absence of a magnetic field is obtained. Another observation relates to the gap closure and breakdown effects. The influence of the magnetic field on these effects is also reported. A suitable working point for an electron tube is chosen according to these observations.

Millimeter-wave insertion loss of mice skin

Abstract We measure the insertion loss of mice skin for millimeter waves. Millimeter waves are used today for various applications such as communications, fog penetrating radar, and detection of concealed weapons and drugs. High-power millimeter wave has been suggested as a non-lethal weapon and recently also for selective cancer treatment. Mice serve as biological models for human beings. Hence, in order to study various effects of millimeter waves on human beings, it is of paramount importance to understand how much millimeter-wave power penetrates the mouse skin and affects the layers beneath the skin, which is the purpose of this experimental paper.