Acoustic Signals Induced in a Copper Target under Irradiation by a Low-Energy High-Current Electron Beam

Results of investigations of acoustic signals induced in a copper plate irradiated with a microsecond lowenergy high-current electron beam (LEHCEB) are presented. The characteristic acoustic signal waveforms, their amplitudes, phases, and frequencies are experimentally measured. It has been established that the acoustic signals induced by LEHCEB irradiation have groups of characteristic spectral components with fundamental frequencies of 6, 11, 22-24, 80, and 100-120 kHz whose amplitudes increased with charging voltage. It has been established that from the change of the 80 kHz harmonic with the charging voltage, the beginning of LEHCEB generation, its stable or unstable phase, and the beginning of target melting can be traced. It has been found that for a fixed charging voltage of each pulse in a series, the amplitude and phase-frequency structure of acoustic signals are almost the same.