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13Complex Systems of Charged Particles and their Interactions with Electromagnetic Radiation 2016
EXPERIMENTAL VERIFICATION THE ABLATION PRESSURE DEPENDENCE FROM THE INTENSITY OF THE LASER RADIATION
I.K. Krasyuk*1, A.Yu. Semenov1, I.A. Stuchebryukhov1, K.V. Khishchenko2
1 Prokhorov General Physics Institute of the Russian Academy of Sciences, str. Vavilova 38,
Moscow 119991, Russia 2 Joint Institute for High Temperatures of the Russian Academy of Sciences, str. Izhorskaya 13
Bldg 2, Moscow 125412, Russia *e-mail: krasyuk99@rambler.ru
The experimental verification of the relation of ablation pressure Pabi (Mbar) on the front surface of the target with the intensity of the laser radiation Ilas (W/cm2):
P =
1 abl
12(10141 as [ A / (2 Z )]
16(10141^ )7X4
3/16
Ias □ 4.3 10
12
W/cm2
Ihs □ 4.3 1012 W/cm2
(1)
(where X is the wavelength of laser radiation (pm), A is the atomic weight, Z is the atomic number of the target substance) in the range of 1.2 1012 " 3.5 1014 W/cm2 (scaling formula) was done. For this purpose, under certain intensities of laser radiation the exit times of the shock wave front on the back surface of the target, depending on the amplitude of the ablative pressure on the front surface of the target, were measured. Two circuit experiments were used. In the first scheme, at high intensities of laser radiation, the output of the shock front on the back surface of the target, followed by the appearance of luminescence, was recorded using electro-optical camera. In the second scheme an optical system was used in which the probe laser beam directs at the back side of the target in shock-wave zone. The shock-wave output was registered by the change in the character of the probe laser pulse reflection from the back surface of the target. Using the test scaling formula, at each realized value of the laser intensity ablation pressure on the front surface of the target was calculated. This value is compared with calculated amplitude of the pressure, at which the shock wave arriving time coincides with the value obtained experimentally. Experimental details and results obtained are given in table 1.
Ta ble 1.
№ Target, thickness 2 Ilas, W/cm P, Mbar 1-arr ns Pabi, Mbar t, ns
1 Al, 21 mkm 3.9 1013 9.6 1.33±0.02 11.1±0.5 2.5
2 Al, 45 mkm 3.5 1014 42 1.50±0.02 41.6±1.7 2.5
3 Cu, 110 mkm 6.0 1012 2.9 22.9±0.3 3.2±0.5 0.07
4 Al, 200 mkm 8.7 1012 3.6 29.3±0.3 3.8±0.23 0.07
5 Al, 50 mkm 1.2 1012 0.82 7.8±0.3 0.8±0.25 0.07
Note. Ilas is the intensity of the laser radiation, P is the pressure calculated by the formulas (1), tarr is the experimentally measured output time of the shock front on the back surface of the target, Pabl, - pressures as to measurement tarr, t- duration laser pulse.
The results show that the formula (1) can be used to calculate the ablation pressure by measuring the laser intensity with a precision of 20 %.
This work was financially supported by grants of the Russian Foundation for Basic Research (No. 14-08-00967, 14-29-06099, 15-02-03498 and 16-02-00371) and the President of the Russian Federation (No.NSh-451.2014.2 and NSh-6614.2014.2), as well as the programs of the Presidium RAS (No. I.25P "Fundamental and applied problems of photonics and physics of new optical materials" and I.11P "Thermophysics of high energy density").
