[en] Charge flows were induced from a laser ablation plasma to a grounded target. The current signals, which were directly measured using a current monitor, developed from negative to positive depending on the dynamically evolving plasma. The results showed that, initially the current was induced by an electron flow from the plasma plume to the surrounding wall and, after a transient phase, the current was replaced by an ion flow to the wall. The results suggest that there was a breaking of the quasi-neutral state of the ablation plasma and that an ambipolar electric field (double layer; DL) was generated during the ablation process. (author)

[en] Two plasma-focus electrodes, consisting of a pair of counter-facing center electrodes surrounded by six outer electrodes, can sustain a long-life, high-energy-density (HED) plasma initiated by laser-triggered multi-channel discharges. With the goal of making a high-average-power plasma device, we investigated the repetition rate of this device. Double-pulse experiments showed that when the device was driven with positive polarity, in which the center electrodes were biased at a positive voltage, the time required for the device to return to a non-conducting state was less than 100 μs, regardless of the operating voltage. The device thus has a repetition rate of more than 10 kHz. (author)

[en] We have developed a counter-facing plasma focus device for the next generation Li plasma light source of photo-lithography. The plasma dynamics in counter-facing plasma focus was discussed to optimize the operating condition. We obtained time-resolved spectra of the Li-plasma, which showed spectral purity evolves as a function of time. Based on the results, we estimated a current sheet profile and the total amount of Li mass that contributes the focusing plasma. (author)

[en] The total energy consumed in the load of a laser-triggered discharge produced plasma light source was measured as functions of the applied voltage, the electrode polarity and the laser energy. When the device operated with negative polarity, the energy consumed in the load was low in comparison with positive mode. In addition, when the laser energy increased, the consumption energy decreased a little. (author)

[en] We studied the effect of rise time of discharge current on the EUV output from the Li plasma in counter-facing discharge device and investigated the plasma dynamics in the device. Results indicated the waveform can control the plasma dynamics and improve the conversion efficiency. The EUV output depended on the shot number in a successive operation mode. The results indicated that changes of Li surface condition during the successive operation affect the plasma dynamics. (author)

[en] Fundamental properties of a counter-facing plasma focus device were characterized. The plasma dynamics in the device, the out-put energy, the spectra from plasma, images of the plasma radiation, and the recovery rate of electrical insulation, were investigated using a proof-of-principle experimental device. All of the results indicated that the device has potentiality as a high average power extreme ultraviolet light source for the next generation lithography system. (author)

[en] Center electrode damages of counter-facing discharge device for Extreme Ultraviolet (EUV) source were classified to stationary damage and pulsed damage. We estimated stationary thermal load by using a semi-empirical simulation. As a results, we found that the electrode temperature becomes too hot under the stationary operation. Also, we examined pulsed thermal load by establishing a simplified model based on the Child-Langmuir sheath. The results showed that the calculation over-estimated the sheath potential, which showed the need to develop a self-consistent model which can deal with the plasma sheath boundary. (author)

[en] Dynamics of laser ablation plasma in vacuum was discussed for incident intensities less than ∼ 10⁹ W/cm². Results showed that the ablation plasma is accompanied by charge flows from the laser ablation plasma to a grounded target. The current signals, directly measured by a current monitor, developed from negative to positive depending on the dynamically evolving plasma. Results also showed that, initially the current is induced by an electron flow from the plasma plume to the surrounding wall and, after a transient phase, the current is replaced by ion flow to the wall. This result reflects a breaking of quasi-neutral state of the ablation plasma during the evolution and corroborates a generation of ambipolar electric field (double layer) during the ablation process. (author)