Experimental observation of superradiance in millimeter-wave band

The first experimental results of the observation of superradiance from a single subnanosecond electron bunch are presented. Superradiance was associated with different varieties of stimulated emission (bremstruhlung, cyclotron, Cherenkov, etc). Unique megawatt power level microwave pulses of short duration (0.3-0.5 ns) have been obtained

Coherent summation of emission from relativistic Cherenkov sources as a way of production of extremely high-intensity microwave pulses

For relativistic Cherenkov devices, we investigate the process of high-power microwave pulse generation with its phase correlating to the sharp edge of an e-beam current pulse. Our theoretical consideration is referred to quasi-stationary and superradiative (SR) generation regimes when spontaneous emission of the e-beam edge serves as the seed for the development of further coherent oscillations. Phase correlation of the excited microwave pulses with the characteristics of the current pulse front and/or an initial external electromagnetic pulse has been additionally confirmed by particle-in-cell simulations. Pulse-to-pulse stability of the radiation phase within several percents of the oscillation period makes it possible to arrange multichannel schemes producing mutually coherent microwave pulses. In the experiments that have been carried out, the cathodes of independent generators were powered by identical accelerating pulses from strictly synchronized voltage modulators, or by splitting the pulse from a single powerful modulator. For the 2-ns regime with the power of each Ka-band backward-wave oscillator about 100 MW, we demonstrate quadratic growth of the power density in the interference maximum of the directional diagram. In a short pulse SR regime, with the peak power of 600 MW in a single channel, for a four-channel 2-D array, we attained a 16-fold radiation intensity gain

Generation of electromagnetic fields of extremely high intensity by coherent summation of Cherenkov superradiance pulses

We demonstrate both theoretically and experimentally the possibility of correlating the phase of a Cherenkov superradiance (SR) pulse to the sharp edge of a current pulse, when spontaneous emission of the electron bunch edge serves as the seed for SR processes. By division of the driving voltage pulse across several parallel channels equipped with independent cathodes we can synchronize several SR sources to arrange a two-dimensional array. In the experiments carried out, coherent summation of radiation from four independent 8-mm wavelength band SR generators with peak power 600 MW results in the interference maximum of the directional diagram with an intensity that is equivalent to radiation from a single source with a power of 10 GW

High Voltage Subnanosecond Monocycle Active Former Based on Compression Energy Unit

Compact high voltage subnanosecond monocycle former (MF) was tested. The device was designed on base of energy compression device and operated in a travelling wave mode. MF consists of high impedance and forming lines, which discharged for the load in parallel. As a result, the monocycle with pulse duration ∼1 ns and typical peak-to-peak amplitude ∼250 kV was formed without additional peaking of the nanosecond pulse rise time. Some pulses reached the maximum amplitude ∼270 kV. The parallel discharge circuit, and a spiral shape of forming line allowed keeping small dimensions of MF, and save enough electrical strength to operate with pulse repetition rate up to 100 pps

Cerenkov superradiance from a subnanosecond electron bunch in a sectional decelerating system

Induced coherent radiation (superradiance) from a subnanosecond electron bunch in a combined decelerating system has been investigated experimentally. In a first section formed by a periodically modulated waveguide, the density of the bunch is modulated and it then radiates in a second section formed by a waveguide partially filled with a dielectric. At an electron energy of 250 keV and a peak current of 800 A, millimeter radiation pulses with powers up to 2 MW and lengths up to 800 ps were obtained

A new source of ultra-short microwave pulses based on the effect of superradiation of subnanosecond electron clusters

Describes a new source of ultra-short microwave pulses based on the effect of superradiation of subnanosecond electron clusters

INVESTIGATION OF RADIAL AIR BREAKDOWN BY TRAVELING TEM-WAVE INITIATED BY RUNAWAY ELECTRONS

Investigations of the air breakdown in the field of traveling TEM-wave have been per-formed. Also researches of the breakdown were carried out both at various amplitudes and at different durations of high voltage pulse

Experimental observation of cyclotron superradiance under group synchronism conditions

Intense microwave pulses (several hundreds of kilowatts) of ultrashort duration (less than 0.5 ns) were obtained from an ensemble of electrons rotating in a uniform magnetic field. The comparison with theoretical simulations proves that this emission can be interpreted as cyclotron superradiance. The maximum radiation power was achieved under group synchronism conditions, when the electron bunch translational velocity coincides with the group velocity of the wave propagating in the waveguide

Generation of powerful subnanosecond microwave pulses in the range of 38-150 GHz

Experimental measurements of coherent stimulated radiation from intense, subnanosecond electron bunches moving through a periodic waveguide and interacting with a backward propagating TM01 male are presented. The ultra-short microwave pulses in Ka, W, and G band were generated with repetition frequencies of up to 25 Hz, Observation of RF breakdown of ambient air, as well as direct measurements by hot-carrier germanium detectors, gives an estimate of the peak power up to 140 MW for the 300-400 ps pulses at 38 GHz. The initial observation of 75 GHz 10-15 MW radiation pulses with duration less than 150 ps, and of 150 GHz microwave spikes with a risetime of 75 ps are also reported