X-Ray Lasers and Plasma Waveguides
Members of the group:
Szergei KUKHLEVSKY, full professor, leader
Imre SANTA, associate professor
Janos SZASZ, research fellow
Matyas KISS, Ph. D. student
Anatoliy SHAPOLOV, Ph. D. student
Soft X-Ray laser
Soft X-Ray laser is a special type of lasers, due to its operating principle and the short wavelength (46.9 nm). The shorter the wavelength, the more energy must be pumped into the system. On the other hand, in aforementioned spectral range, there are no mirrors with acceptable reflection, which are not destroyed by the capillary plasma jet. Moreover, population inversion cannot be sustained for a long time (longer than single passing time). Therefore, such laser works in the so-called Amplified Spontaneous Emission (ASE) mode. In order to improve the pumping efficiency, researchers usually used to increase the energy density by applying different techniques. Basis of ours is the phenomenon called Z-pinch. It occurs during the capillary discharge, in which the produced plasma shrinks due to Lorenz-force arising from magnetic field induced by high peak (13...20 kA) electric current pulse flowing through the capillary.
Investigation of the alternative particle accelerators recently is a subject of growing interest among many scholars and researchers. It applies to our research group too, since numerical simulations of the plasma dynamics showed, that the high peak electric current triggers an electron density shockwave, which propagates from the capillary wall toward the axis. As a result, in vicinity of the axis a convex electron density profile occurs with significant gradient. Since refractive index of the plasma depends on the electron density, such circumstances lead to gradient of the refractive index as well. This feature of the plasma persists for several nanoseconds. Within this time range, plasma column behaves like a graded optical fiber, which plays a key role in terms of laser pulse stabilization. Furthermore, a sufficiently short and high intensity laser pulse is able to accelerate electrons, due to wake field arising from nonlinear ponderomotive force.
A.A. Shapolov, M. Kiss, and S.V. Kukhlevsky: A Simplified MHD Model of Capillary Z-Pinch Compared with Experiments, Contrib. Plasma Phys. 56, 10, 959-967 (2016).
J. Szasz, M. Kiss, I. Santa, S. Szatmari, and S.V. Kukhlevsky: Magnetoelectric Confinement and Stabilization of Z Pinch in a Soft-X-Ray Ar+8 Laser, Phys. Rev. Lett. 110, 183902 (2013).
J. Szasz, M. Kiss, I. Santa, S. Szatmari, and S.V. Kukhlevsky: Critical Parameters of the Pumping Scheme of Ar+8 Lasers Excited by Z Pinches in Long Capillaries, Contrib. Plasma Phys. 52, 770 (2012).
S.V. Kukhlevsky, A. Ritucci, I.Z. Kozma, J. Kaiser, A. Shlyaptseva, G. Tomassetti, O. Samek: Atomic Model Calculations of Gain Saturation in the 46.9 nm Line of Ne-like Ar, Contrib. Plasma Phys. 42, 1, 109 – 118 (2002).