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Tomassetti, Giuseppe; Ritucci, A.; Reale, A.; Palladino, L.; Reale, L.; Kukhlevsky, S. V.; Flora, F.; Mezi, L.; Kaiser, Jozef; Faenov, A. Ya.; Pikuz, T. A.

doi:10.1007/s10053-002-8855-7

Cited by 21 publications

(34 citation statements)

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“…the collisional excitation scheme [1]. Strong amplification was observed in the 3P → 3S transition at 46.9nm [2]- [5]. The timing of the amplification (that lasts about 1ns) is close to the pinch time (i.e.…”

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The effects of the prepulse on capillary discharge extreme ultraviolet laser

et al. 2006

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In the past few years collisionally pumped extreme ultraviolet (XUV) lasers utilizing a capillary discharge were demonstrated. An intense current pulse is applied to a gas filled capillary, inducing magnetic collapse (Z-pinch) and formation of a highly ionized plasma column. Usually, a small current pulse (pre-pulse) is applied to the gas in order to pre-ionize it prior to the onset of the main current pulse. In this paper we investigate the effects of the pre-pulse on a capillary discharge Ne-like Ar XUV laser (46.9nm). The importance of the pre-pulse in achieving suitable initial conditions of the gas column and preventing instabilities during the collapse is demonstrated. Furthermore, measurements of the amplified spontaneous emission (ASE) properties (intensity, duration) in different pre-pulse currents revealed unexpected sensitivity. Increasing the pre-pulse current by a factor of two caused the ASE intensity to decrease by an order of magnitude -and to nearly disappear. This effect is accompanied by a slight increase in the lasing duration. We attribute this effect to axial flow in the gas during the pre-pulse.PACS numbers: 42.55. Vc,42.60.Lh In the last decades the possibility of achieving Amplified Spontaneous Emission (ASE) in the soft X-ray and XUV regimes was extensively explored [1]. One of the realizations utilizes a homogenous column of highly ionized plasma created by a fast capillary discharge [2]. Specifically, a fast (∼ 50ns) and intense (∼ 50kA) current pulse is applied to a capillary filled with low pressure (∼ 1T orr) argon gas. The current induces magnetic forces that attract the gas towards the capillary axis. During the selfcollision of the gas on the axis a column of highly ionized Ar plasma is formed (this technique to create high temperature plasmas is called Z-Pinch). Careful design of the experimental parameters results in high abundance of Ne-like Ar ions in the plasma, and population inversion between the 3P and 3S electronic configurations. The population inversion is due to excitations by collisions with hot electrons in the plasma and spontaneous emission -i.e. the collisional excitation scheme [1]. Strong amplification was observed in the 3P → 3S transition at 46.9nm [2]- [5]. The timing of the amplification (that lasts about 1ns) is close to the pinch time (i.e. the collision of shock waves on the capillary axis). Obviously, for efficient amplification the plasma column must be relatively stable and homogenous (at least up to the amplification time). Several effects might cause instabilities or inhomogeneity in the Z-pinch process (see Ref.[6] and references therein). One of the possible reasons for inhomogeneity is the initial electrical breakdown through the gas column. At the onset of the main current pulse, high voltage across the capillary (hundreds of kV), may result in channel-like breakdown along the capillary walls (channel sparks) [7]. A technique to overcome this inhomogeneity is to pre-ionize the gas by a slow, low intensity current pulse ("pre-pulse"). In Refs...

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“…In Refs. [2]- [5] a small current (typically 10 − 100A) is applied for a few µs be- * Email address: shuker@physics.technion.ac.il fore the onset of the main current pulse. The pre-pulse current creates sufficient amount of pre-ionization in the argon gas, allowing the main current pulse to flow homogenously (i.e.…”

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The effects of the prepulse on capillary discharge extreme ultraviolet laser

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“…The shock wave propagates towards the capillary axis forming a plasma waveguide of continuously decreasing diameter. The axially uniform plasma column, which has a length up to about 45 cm, can be created in the non-ablative ceramic capillary with a repetition rate of several Hz [16,17]. Our experiments [16] show that the wall evaporation in ceramic capillaries is negligible in comparison to that obtained using ablative capillaries.…”

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Non-ablative capillary z-pinch for plasma-based waveguide

et al. 2005

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The conditions for the formations of plasma-based waveguide in non-ablative argonfilled capillary discharge are studied theoretically. The pinch dynamics is simulated using magneto-hydrodynamic code originally developed and utilized to find proper conditions for operation of capillary-discharge Ar +8 soft x-ray laser. The presented results show that the ablation-free capillary z-pinch provides conditions that are suitable for guiding of high-intensity laser pulses on the earlier stages of the plasma compression.

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“…However, in spite of the big efforts, it is not clear up to now which one of the basic processes and experimental conditions are critical for the achievement of the lasing effect. For this reason, only very recently three independent groups [2,3,4] demonstrated the gain coefficient sufficient for the 46.9 nm lasing in Ne-like Ar inside a capillary discharge produced plasma.…”

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confidence: 97%

Role of the wall ablation in the operation of a 46.9 nmAr capillary discharge soft x‐ray laser

Ritucci¹,

Tomassetti

Reale

et al. 2003

Contrib. Plasma Phys.

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A capillary discharge pumped soft x-ray laser operating at 46.9 nm on the 3p−3s transition of the Ne-like Ar has been realized by pumping the active medium with a relatively slow current pulse (dI/dt ≈ 6·10 11 A/s). In order to study the role of the ablation in the production of the laser effect, the intensity of the amplified 46.9 nm line has been investigated using the same pumping current pulses in the plastic (polyacetal) and ceramic (Al2O3). We showed that the ablation of the capillary walls is unfavorable both for the compression and stability of the plasma and consequently for the soft x-ray laser production. The amplification and lasing effects are observed only in the ceramic channel. The measurements of the line intensity at 46.9 nm showed the lasing with a gain-length product of ≈ 9, a laser pulse energy of ≈ 5 µJ, a pulse duration of 1.3 ns and a beam divergence of ≈ 3.5 mrad. In addition, effect of the scaling of the time of lasing with the initial plasma diameter was demonstrated experimentally and compared with a one-dimensional MHD model.

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Cited by 21 publications

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The effects of the prepulse on capillary discharge extreme ultraviolet laser

The effects of the prepulse on capillary discharge extreme ultraviolet laser

Non-ablative capillary z-pinch for plasma-based waveguide

Role of the wall ablation in the operation of a 46.9 nmAr capillary discharge soft x‐ray laser

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