High-frequency, amplitude modulation of a submillimeter wave, medium power gyrotron

Abstract

Experimental results of the amplitude modulation of the output of a submillimeter wave gyrotron are presented. The 100% modulation of the output at frequencies up to several hundred kilohertz has been achieved with anode modulation levels of only a few percent. A good account of the experimental results is given by including a small modulation of the anode voltage in an energy transfer formula and then calculating the power output.

Design of a Compact Sub-Terahertz Gyrotron for Spectroscopic Applications

“…For the gyrotron under consideration we have developed a triode MIG in order to retain the possibility for flexible control of the electron beam parameters. Using such gun one could perform an effective feed-back control for stabilization of the output power through the mechanism of amplitude modulation [38], which is based on the dependence of the efficiency on the velocity distribution and velocity ratio. In a triode MIG the latter can be controlled varying the potential of the anode.…”

Development of a compact sub-terahertz second-harmonic gyrotron

“…The triode MIG allows one to tune finery the beam controlling the potential of the intermediate anode. Additionally, using such gun it is possible to implement an effective feedback control for stabilization of the output power taking advantage of a mechanism, which is known as amplitude modulation [3] and is based on the dependence of the efficiency on the velocity distribution and the velocity ratio. Controlling the current of the additional solenoids it is possible to finely adjust the magnetic field on the cathode.…”

Rapid frequency step-switching in submillimeter wave gyrotrons (Gyrotrons FU III and FU IV)

“…Our high-frequency gyrotrons covering the wide range from millimeter to submillimeter wavelengths ͑Gyrotrons FU III and FU IV͒ have demonstrated 3,4 amplitude modulation of their outputs, where in some situations only a few percent modulation of V a causes almost 100% modulation of the output amplitude. Furthermore, a linear dependence between V a and the amplitude is realized over a wide range of gyrotron operating parameters.…”

“…Amplitude modulation has been achieved in high power gyrotrons 1,2 and also in highfrequency gyrotrons. [3][4][5] The principle is as follows. The anode voltage V a of a triode magnetron injection gun determines the pitch angle ␣ of a beam electron in the gyrotron cavity, which in turn determines the efficiency of energy transfer from beam electrons to the electromagnetic wave.…”

“…Furthermore, a linear dependence between V a and the amplitude is realized over a wide range of gyrotron operating parameters. The modulation frequency can be increased up to several hundred kHz 3,4 or several MHz. 1 A beam with such a modulation may be applied to a phase sensitive measurement of plasma and other materials, communications in millimeter to submillimeter wave region, study of relaxation phenomena in plasma, and so on.…”