Journal of Russian Laser Research, Volume 34, Number 3, May, 2013
INTENSITY DISTRIBUTION
OF A CAPILLARY-DISCHARGE 46.9 nm SOFT X-RAY LASER
Yongpeng Zhao,
1
Han Wu,
1 ∗
Yao Xie,
2
Shan Jiang,
1
Huaiyu Cui,
1
and Qi Wang
1
1
Harbin Institute of Technology
National Key Laboratory of Tunable Lasers
Harbin, 150080 P. R. China
2
Chinese Academy of Sciences, Changchun Institute of Optics and Fine Mechanics
State Key Laboratory of Applied Optics
Changchun, 130033 P. R. China
∗
Corresponding author e-mail: schmeichel1992 @ 126.com
Abstract
We realize a Ne-like Ar 46.9 nm soft X-ray laser pumped by a capillary discharge. The study of the laser-
pulse-intensity distribution is important for applications of soft X-ray lasers. The intensity distribution
demonstrates the gain distribution, plasma radius, and axial plasma density that contribute to the
study of the laser-pulse formation. To measure the intensity in different positions of the X-ray laser
spot, we moved transversally an X-ray diode (XRD) assembled with a slit. We obtain the one-
dimensional intensity distribution. We find a laser divergence (FWHM) of 4.0 mrad. According to
the gain-guided model, we calculate the intensity distribution. The measured divergence of 4.0 mrad
roughly corresponds to a plasma radius a approximately equal to 230–250 µm and on-axis electron
density n
e
≈ 8.0 · 10
18
− 9.0 · 10
18
cm
−3
. The results of calculations indicate that the divergence of
the intensity distribution increases when the plasma radius decreases and the on-axis electron density
increases.
Keywords: capillary discharge, intensity distribution, slit scanning, gain-guided model.
1. Introduction
Soft X-ray lasers are used in the diagnostics of high-density plasma, material ablation, soft X-ray
microscopy, and micromachining. In 1994, Rocca et al. first demonstrated a Ne-like Ar 46.9 nm soft
X-ray laser pumped by a capillary discharge [1]. As for the intensity distribution, they obtained the
time-resolved end-on soft X-ray images utilizing an X-ray pinhole camera [2]. With the MCP intensified
CCD and the phosphor-screen assisted CCD, they measured the intensity distribution and divergence
of different soft X-ray lasers [3, 4]. They adopted the gain-guided model to calculate the distribution
and analyzed the key impacts theoretically [5]. In 1998, they performed systematic measurements of
two-dimensional near-field and far-field intensity distributions of the laser and numerical modeling of the
dive rgence and output beam pattern [6].
Tomassetti et al. reported the 4 6.9 nm soft X-ray laser output in 2002 [7]. In their experiments, an
aluminum foil was used to cut the visible and ultraviolet radiation, and a slit (3 mm) was positioned in
Manuscript submitted by the authors in English on December 29, 2012.
1071-2836/13/3403-0203
c
2013 Springer Science+Business Media New York
203