Statistical investigations of the beam stability of the double-pass amplified zinc soft X-ray laser at 21.2 nm
PALS, Institute of Physics, Academy of Sciences, Na Slovance 2, 18221 Prague 8, Czech Republic
Corresponding author: a firstname.lastname@example.org
Revised: 16 April 2003
Published online: 5 August 2003
At the Prague asterix laser system (PALS) of the Academy of Sciences of the Czech Republic the 1-TW asterix iodine laser is used as a pump source for soft X-ray laser experiments. The prepulse technique was applied which is known to enhance the X-ray laser output at the J=0–1 transition dramatically. Since Zn slab targets were used the laser wavelength was 21.2 nm. A prepulse beam having 1.6 J was preceding the main pulse by 10 ns. The main and the prepulse beam are focused by two different optical systems separately. Implementing a half-cavity set-up for double-pass amplification using a Mo/Si multilayer mirror the X-ray laser output was 10 times stronger than at single pass amplification in a 3-cm long plasma. Double-pass amplification was observed to be most efficient when the pump pulse duration was at least 120 ps longer than the round trip time in the half-cavity. Under this fundamental condition the X-ray laser reached saturation in the double-pass regime containing 4 mJ energy what is proved to be enough for applications. In this contribution the X-ray laser features like divergence in two dimensions, the beam quality (symmetry), the pointing angle and the time-integrated output energy are investigated over more than 100 shots. To characterize the stability of the X-ray laser the shot distribution, the mean value and the standard deviation for these parameters are evaluated. For 18 shots in a series — achieved during one single day — the corresponding values are given and detailed chi-squared tests characterize the Zn X-ray laser as a robust tool suitable for applications. At PALS soft X-ray laser beam time can be reserved for external research groups.
PACS: 42.55.Vc – X- and γ-ray lasers / 42.60.Da – Resonators, cavities, amplifiers, arrays, and rings / 42.60.Jf – Beam characteristics: profile, intensity, and power; spatial pattern formation
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003