Four-channel source of synchronously modulated subgigawatt voltage pulses

Summary form only given. Investigations preceded the development of subgigawatt rf source based on a single, shock-excited ferrite-loaded nonlinear transmitting line (NLTL) demonstrated that the frequency (F_rf) and power (P_rf) of rf generation are determined by numerous parameters (see Ref. [1] and citation therein). The most critical are the properties of ferrite insert, radial and longitudinal dimensions of NLTL, as well as the amplitude (V_p) and the rise time of the feeding voltage pulse. When aiming simultaneous increase in F_rf, P_rf and pulses repetition frequency (PRF), one undoubtedly meet the problem of breakdown strength of NLTL. Refurbished version of an all-solid-state modulator [2] used in presented investigation produces at 50-Ohm terminal a pulses (~3 ns, FWHM) with the amplitude of (325-450) kV which depends on PRF (up to 800 Hz). Utilizing the power of such pulses (P_v > 2 GW) for rf excitation at F_rf ~2 GHz and at highest PRF could be arranged by splitting feeding pulse to several identical NLTL-channels producing synchronous modulation of decreased in amplitude voltage pulses at identical F_rf. In the prospect, such a multi-channel rf array may provide sharpening of the radiation pattern which also could be scanned somewhat with the electronic variation of the NLTLs delays. Above listed objectives of our investigation determine the stage, when technical features of separate components should be found prior full-scale experiments. We increased step-by step the quantity of NLTL channels (one, two, or four). For a single channel option, empty terminals of the modulator were loaded with absorbing water lines. In a single-channel version it was found that all tested NLTLs having overall diameter 40 mm and different in length sets of ferrite rings are resistant against breakdowns of both ferrite body as well as oil insulation pressurized up to 6 atm. In the limited - RF of 1 Hz, the voltage pulse top (V_p ~180 kV) was modulated at F_rf ~2.25 GHz, and peak-to-peak rf amplitude attained V_rf ~100 kV. The rise of PRF to 800 Hz provided the following: V_p ~130 kV; F_rf ~2.1 GHz; V_rf ~80 kV. In the options with two and four channels we tested correlations of F_rf and V_rf instability with variations of V_p, as well as interchannel mishmash of above parameters and the reasons for that.