It is reported that researchers for the first time proved by the low energy, ultra-short middle infrared (MIR) laser pulse driven relativistic electrons. Many applications can use accelerated beams with lower energy and higher repetition rates, such as fast scan imaging for medical, scientific and safety purposes.
Howard Milchberg, a professor of physics and electrical engineering at the University of Maryland, said: "We are currently working on a compact, highly repetitive laser accelerator that uses the lowest possible laser pulse energy to generate relativistic electrons."
Compared with the previous experiments, the long driving wavelength and low energy femtosecond laser pulse used in this project can easily approach the so-called "critical density" state. Because the critical density varies inversely with the square of the laser wavelength, gas targets for MIR laser pulses are 100 times lower than those used in visible light and NIR, making them more difficult to design.
Milchberg points out that "when a few millijoules femtoseconds of mid-infrared laser pulses are focused by a curved mirror into a jet of hydrogen - a jet of hydrogen from a nozzle - a beam of collimated electrons fires from the other side of the jet. The laser achieves very high intensities, which is much higher than what can be achieved with the use of a curved mirror, which happens by relatively autofocusing in ionized hydrogen, shrinking it to less than its focal point Much more size. "
According to Milchberg, the value of the critical density system is that relative auto-focusing can be promoted even with low-energy laser pulses. This enhanced high-intensity interaction creates a plasma wave that accelerates some of the electrons from the ionized hydrogen to a forward relative beam.
Experiments show that if there is no relative autofocus, we can not produce electron acceleration.
The team's findings are just the early stages of the development and application of high repetition rate laser-driven accelerators.
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