X-ray emission during the ablative processing of biological materials by ultrashort laser pulses

Abstract

The ablative laser processing with ultrashort pulsed laser beams may cause secondary emission of hazardous X-rays. While the effect has recently been proven to be considered in working safety regulations when processing technical materials, such as metals, the X-ray emission rates during the ablative processing of biological tissue materials are widely unexplored yet. Therefore, biological materials like water, isotonic saline solution, pig eyes, and human teeth were ablated with ultrashort laser pulses of 1030 nm wavelength, 600 fs pulse duration and 5 kHz pulse repetition rate, aiming to mimic typical surgery situations. Simultaneously, in-situ X-ray dose rate measurements were performed at a short distance from the plasma to display potential X-ray emission. For all four studied biological materials, our measurements prove the secondary emission of laser-induced X-rays.

Self-Shielding of X-ray Emission from Ultrafast Laser Processing Due to Geometrical Changes of the Interaction Zone

“…Most of the experimental studies on the emission of ionizing radiation from laser-produced plasmas were already carried out in the 1980s under high vacuum conditions [ 9 , 10 , 11 , 12 , 13 , 14 ], resulting in only a few publications considering industrial conditions [ 7 , 15 , 16 , 17 , 18 ]. With the increase in available power of recent ultrafast lasers, the topic is gaining interest in the area of industrial laser material processing, which has lead to the latest investigations about the influence of high pulse repetition rates [ 19 ], different materials [ 20 ] and the pulse duration [ 21 ] on the X-ray emission. There are several important differences between the two conditions, one being the air breakthrough (ionization of the gas atmosphere) at high intensities [ 22 ] when working in standard atmosphere, leading to defocusing of the incident laser beam and thereby reducing the local irradiance on the workpiece.…”