Quasi-optical components for MMW fed radars and particle accelerators

A fast switch, combiner and narrow-band filter for high-power millimetre wave beams

“…The amplitude transmission coefficients from the input to output 1 and 2, respectively, are given by This type of diplexer has been investigated in detail for highpower multi-channel transmission [5,6]. As prototype for a high-power switch, a diplexer/combiner for 140 GHz, 1 MW was designed, consisting of a ring resonator with L = 2. calculated from (3) and including the fields of the coupled beams) corresponds to an energy-flux density of 0.83 MW/cm 2 , which is below the 1 MW/cm 2 threshold of atmospheric air breakdown.…”

“…Thus, depending on the experiment, there is no need to increase the number of launchers, else one could even reduce the number of launchers by using this device. As long-term perspective, switching of a high-power beam generated from several continuously operating sources can be provided by using a multiplexer fed by a set of frequency-controlled gyrotrons [3,4,5,6,7]. Infinitely variable beam steering could become possible with a phased array fed by a set of gyrotrons (or high-order-mode gyroklystrons) which are phase locked to a common low-power reference oscillator via electrically controlled phase shifters [4,5,7,8,9,10].…”

New Concepts for Quasi-Optical Structures for Use With Gyrotron Systems

“…8 [9], [16], [17]. If frequency band widths are narrower, not exceeding 1%, multiplexers of resonant and interferometric types seem preferable [9], [14][15][16]. An example of this approach is a ring mirror cavity coupled to input and output wave flows by a mirror corrugation, as illustrated in Fig.…”

“…Such a diplexer (Fig.10) [15] was used to combine the power from two near-140 GHz sub-MW gyrotrons with voltage-controlled frequencies; the combined power was switched between two output channels at switching frequencies up to 10 kHz, which is typical for the neoclassical tearing mode (NTM) instability in modern tokamaks. Quasi-optical diplexers of both resonant and interferometric types could be configured into multiplexers with a relatively large number of inputs and outputs [9], [14][15][16]. In particular, multiplexers can provide the wave combiningswitching performance shown in Fig.7, when gyrotron voltages are modulated and, accordingly, gyrotron frequencies are varied [14], [15].…”

“…A specific means to control RF beams can be provided with gratings of the Littrow configuration when the incident beam and the -1 st order scattered beam share a common plane with the groove direction [5]. With a proper corrugation depth, a grating based on this configuration can function as a four-port -3dB hybrid (analogous to the usual magic T) [9]. When two RF beams of equal power are combined, the combined beam direction is switched from one output to another by changing the mutual phase-shift between the input beams.…”