Magnetron injection gun for a broadband gyrotron backward-wave oscillator

Abstract

The magnetron injection gun is capable of generating relativistic electron beam with high velocity ratio and low velocity spread for a gyrotron backward-wave oscillator ͑gyro-BWO͒. However, the velocity ratio ͑␣͒ varies drastically against both the magnetic field and the beam voltage, which significantly limits the tuning bandwidth of a gyro-BWO. This study remedies this drawback by adding a variable trim field to adjust the magnetic compression ratio when changing the operating conditions. Theoretical results obtained by employing a two-dimensional electron gun code ͑EGUN͒ demonstrate a constant velocity ratio of 1.5 with a low axial velocity spread of 6% from 3.4-4.8 Tesla. These results are compared with a three-dimensional particle-tracing code ͑computer simulation technology, CST͒. The underlying physics for constant ␣ will be discussed in depth.

A magnetic cusp gun for terahertz gyro-devices

“…The heater magnetic fields from the going and returning heating current could counteract with each other. The mechanical design is similar to the demountable configuration [9]. The inner cathode electrode, made of molybdenum, and the anode, made of oxygen free copper, are demountable, and could be customized according to specific magnetic field profile.…”

Magnetron injection gun design for a Q-band 300 kW 30 A gyrotron traveling wave tube

“…Derived LVS due to CTT is shown as [26] (12) where K is Boltzman's constant, T c is the cathode temperature. For a thermionic cathode with an operating temperature of 1300 K, the calculated ( β z ) CTT is 1.22%.…”

“…The remaining two mechanisms, CSR and CTT, which feature in ineluctability and are not considered by EGUN code, should be taken into consideration additionally. The contribution of CSR to LVS is given as [26] (…”

“…For a thermionic cathode with an operating temperature of 1300 K, the calculated ( β z ) CTT is 1.22%. Since the three sources are statistically independent, the combined effect can be evaluated by giving the square root of the square sum as follows [18,26] ( β z ) TOTAL = ( β z ) 2 ERO + ( β z ) 2 CSR + ( β z ) 2 CTT 1/2 (13) The estimated overall LVS is about 3.44%, which is good enough for this Q-band gyro-TWT.…”

Design of a Compact Sub-Terahertz Gyrotron for Spectroscopic Applications

“…It is based on a self-consistent fully relativistic physical model which takes into account the space charge and initial velocities effects. As a starting point an existing MIG developed previously for some other tubes of the Gyrotron FU series has been selected as a prototype and scaled down (using the well known analytical relations [28,[35][36][37]) in order to produce the initial variant of the design. Then as a result of an a iterative design loop, performing trajectory analysis (ray tracing) after each change of the configuration, positions and dimensions of the electrodes (including the emitting ring) a system which produces an electron beam with appropriate parameters has been selected.…”