Effect of preionization uniformity on a KrF laser

Sumida, Shin; Kunitomo, Kouichi; Kaburagi, Masahiro; Obara, Minoru; Fujioka, Tomoo; Sato, Kanta

doi:10.1063/1.329074

Cited by 29 publications

(2 citation statements)

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“…Otherwise, arcs are formed during the formation phase of the discharge, and the gas is not effectively pumped. However, the avoidance of streamers alone is not sufficient for optimum pumping conditions, since the avalanche formation time decreases with higher initial electron density which results in a longer optical pulse [12][13][14]. Additionally, when the number density of preionization electrons is too small, the optimum electron density in a fully established discharge (~1015cm -3) may not be reached at all.…”

Section: X-ray Preionizationmentioning

confidence: 99%

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Compact, wide aperture X-ray preionized XeCl laser with high specific optical power

et al. 1989

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Abstract. An X-ray preionized, discharge-pumped XeC1 laser with a variable beam crosssection of up to 6 x 6 cm 2 is described. It uses fiat electrodes and the beam width is determined by X-ray collimation. Its operation characteristics concerning reduced electric field strength (E/p) and X-ray dose are discussed in detail. The inductance of the discharge loop is minimized using a water capacitor arrangement. A very high specific optical power (90 MW/1) is achieved in an active volume of 1.21. The pulse energy exceeds 5 J in a 45 ns pulse (FWHM).PACS: 42.55G, 42.60B, 52.80HFor the generation of intense UV laser pulses at the KrF and XeC1 wavelengths, a wide aperture, discharge-pumped excimer laser with a high excitation rate is of considerable interest. However, when scaling discharge-pumped systems to a larger cross-section (active volume) one faces the problem that the energy storage medium has to be low-inductively coupled to the main discharge. For pumping large volumes a pulse forming line (PFL) is usually employed and connected by a rail gap switch to the laser head to decrease the voltage rise-time [-1 ]. However, the pumping rate is limited by the given impedance of the PFL. In contrast to the total pump energy, the pump power is not increased with the length of the line. The achievable optical power per unit volume is generally considerably smaller than in small volume systems which mostly employ lumped circuits. It seldom exceeds 50 MW/1 for active volumes of more than I 1, whereas in small lasers (~50 cm3), 300 MW/I can be easily obtained [2].To achieve high pumping rates in a large aperture laser employing a lumped circuit, both low inductance electrical circuit and high charging voltage are needed. We employa combination of the waterline and the lumped circuit technology by using a number of parallel waterlines of short electrical length [3]. This arrangement has a very low inductance and is suitable for a charging voltage of 150 kV.X-ray preionization was chosen to provide a sufficiently high and spatially homogeneous initial electron distribution even at high pressures. Moreover, X-ray preionization allows easy variation of the beam cross-section and the use of flat electrodes [4,5]. By variation of the beam width which is determined by horizontal lead apertures, the pump current density can be varied and optimized.In this paper we report on a wide aperture (6 x 6 cm 2) XeC1 oscillator. The active volume of the laser can be varied up to 1.5 1. Under optimized conditions more than 5 J are generated in a 45 ns (FWHM) pulse corresponding to 4 J/1 and an average specific optical power of 90 MW/1. We performed detailed studies of the influence of electrical parameters and conditions of X-ray preionization.

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Section: X-ray Preionizationmentioning

confidence: 99%

“…In the literature a logarithmic growth of the laser pulse energy, EL, with the preionization electron density ne has often been observed, which has (at least partially) been attributed to an increase of optical pulse length [12][13][14]. This dependence can be expressed as EL = c In (no/n~,mi.…”

Section: X-ray Preionizationmentioning

confidence: 99%