Dynamics of plasmas produced by a laser pulse, inside a dense gaseous target, formed in an ambient gas

In this work, the time development of plasmas produced by interaction of laser pulses, with a nitrogen gas, was investigated. The interaction took place inside a small portion of dense nitrogen gas injected temporarily into a chamber filled with the gas under low pressure. High-temperature plasmas produced directly by the laser pulse were a source of soft x rays and charged particles, ionizing and exciting the surrounding gas. In this way, low-temperature plasmas were produced. The formation of high-temperature plasmas was studied using soft x-ray spectroscopy and x-ray streak imaging. Low-temperature plasmas formed at various distances from the laser focus were investigated using an optical streak camera. Interpretation of the experimental data was supported by numerical modeling of the laser-produced plasma hydrodynamics. It was concluded that depending on the distance from the focal spot, the formation of the low-temperature plasmas was dominated by ion streams or by soft x-ray radiation.