[A measurement of spontaneous magnetic field by satellites structures of harmonic spectrum]

The satellites structures of doubling harmonic spectrum and tripling harmonic spectrum were measured at the reflection direction of laser wave from the front side of targets, employing OMA optical multi-channel spectrometer during the interactions of femtosecond laser with solid targets. The satellites structures of red-shift harmonic spectrum of 2omega0 and 3omega0 were observed. Under the intensity of approximately 10(18) W x cm(-2), the result of measurement indicates that the spontaneous magnetic field was all less than 1 MGs level by analyzing the satellites structures of doubling harmonic spectrum and tripling harmonic spectrum during the laser-plasma interaction. With increasing the intensity of the laser pulse, the peak of the red-shift moves further to the long wavelength side causing the broadening of the spectrum. The measurements of the spontaneous magnetic field provide a basis of diagnosing the movement of the critical surface in the laser-plasma interaction process.