V. L. Kaminsky

Note: Resonant microwave compressor with two output ports for synchronous energy extraction

The brief theoretical analysis shows the resonant microwave compressor provides the output pulse power higher than the traveling wave power in the storage cavity. The experimental study was made with the model of the S-band microwave compressor. The power of pulses generated by the device reached the value three times as much as the value of the traveling wave power in the storage cavity at the maximum amplification 23 dB, peak power 400 MW, and pulse width 4-5 ns.

Oversized interference switches of active resonant microwave compressors

Interference switches of resonant microwave compressors made of single mode waveguides provide high coupling factors after switching and rapid energy extraction. The disadvantage of these switches is low electrical strength which limits output power values. Oversized waveguides maintain higher electrical strength due to large dimensions of a cross section but mode transformation disturbs the regular operation of the switch. Operation of interference switches with a gaseous discharge gap as a switching element in oversized rectangular waveguides was studied experimentally. Conditions of their effective switching in active resonant microwave compressors were derived. It was shown that the stable microwave pulses of gigawatt power level in S-band and pulses of 0.1 GW pulse power in X- band can be produced in resonant microwave compressors with oversized interference switches. Possible switch designs are discussed.

Synchronous energy extraction from oversized cavities designed with smooth transitions

Synchronous operation of storage cavities connected in parallel increases a maximum permissible output power level of a microwave compressor; an oversized cavity used in a compressor increases the amplification factor. These two characteristic properties used jointly in the microwave compressor design could improve the parameters of the device considerably. Results of the experimental study of the oversized S-band compressor where the energy was extracted through a smooth transition were presented. It was noted the design maintains relatively small overall dimensions, high efficiency and amplification factor values. Measurements showed the source provided steady nanosecond pulses at repetitive operation mode up to 100 Hz of 0.4 GW pulse output power for the single oversized cavity. The design of the system consisting of four storage units is proposed. Preliminary estimation shows the output limiting pulse power exceeds the one of a single cavity design at power amplification factor 22 dB and efficiency about 0.3.

Switching of H 11 -mode electromagnetic field in oversized circular waveguide

Operation of the microwave switch in a circular waveguide with the principal working mode H11 at the frequency 2800 MHz was studied. Experimental results for different switch designs and traveling wave power values up to 0.5 GW are presented. The switching occurs by the microwave discharge plasma formed in the quarts tube filled with gas. The energy distribution between transmitted, reflected and dissipated waves in a waveguide with permissible H11 and E01 modes during switching process was investigated. Main conditions for effective switching in a regular waveguide when the cross section is close to cut-off one for H01 and E11 modes and in short circuited arm of the same cross section of H-tee interference switch are determined.

Synchronization of energy extraction from microwave compressor cavities with laser triggering

Laser triggering was used to synchronize the switching of two resonant microwave compressors over to energy extraction mode. The obtained experimental data of the study are presented. Practically the precise synchronism was demonstrated when switching the working mode in the storage regime. Each compressor provided pulses of 250 MW power and 5 ns pulsewidth, the pulse summation gave the output pulse power of 500 MW. Foundation of the supposition that the combined power of several compressors with common load can exceed 1 GW when laser radiation synchronized operation is given.

Two channel high power microwave compressor

High power microwave nanosecond pulses can be generated by the procedure of microwave energy resonant storing in a high Q-value cavity with following fast energy dumping. The output power value is limited by electric strength of the switch gap and the design of the device studied in this report is meant to overcome the limitation. The device contains two parallel cylindrical cavities, the output waveguide bridge made of circular waveguides and the common output line. The single switch is located in the bridge side arm so the energy is dumped through direct bridge arms synchronously into the combining output line. Each cavity included the oversized cylindrical section bounded by an end cap having the input iris and a smooth transition matching bridge waveguides. Calculation showed the electric field strength in the switch is about 135 kV/cm and the total output power is in the range 0.55-0.9 GW depending on parameters of the cavities. Experimental tests were run in S-band with 5 MW input power pulses. The measured output pulse power was ~0.8 GW at pulse repetition rate 10 Hz, output pulsewidth 5.1 ns at -3 dB level and gas pressure in the switch up to 1 bar.

Microwave compression in superconducting cavities

Evaluations for possible using of superconducting materials in high power microwave generators based on the method of the resonant microwave compression were made. As an example the relationship between the power amplification factor and frequency was determined for superconducting rectangular cavities. Capabilities of superconducting cavities as energy accumulators were analyzed. Microwave power value required for feeding superconducting accumulator is estimated. Experimental results of storing and extracting the energy in superconducting cavities are presented.