Measurement of Gas Temperature Profile in Discharge Region of Excimer Laser with Laser Schlieren Method

Abstract

Shock waves are generated by pulse discharges in the cavity of excimer lasers. The shock waves cause arcing, nonhomogeneous excitation of laser gas and limitation of repetition rate of a high-repetition-rate excimer laser. Distribution of temperature rise by pulse discharge is an essential factor for generation and propagation of shock waves. Gas temperature profiles in the discharge region of the excimer laser cavity are measured by a laser schlieren method for single-pulse operations. The results show that the temperature distribution depends on the xenon concentration. In the cases of pure helium and higher xenon concentration, the temperature distributions are steeper than those in the cases of lower xenon concentration.

Influences of gas density depletion on high-pressure, pulsed-glow discharge

“…Here, the rise of the gas temperature is about several dozen degrees [2] and is small compared to the electron temperature (several to several dozen electron volts) of the high-pressure pulsed-glow discharge [11], and so it may not influence the discharge characteristics. Immediately after discharge (t = 0.1 ms), the density change 'U / U 0 is about 4.2% and the 10% width of the depletion W is about 12.3 mm.…”

“…However, under highly repetitive operation, uniform glow cannot be maintained, and finally the arc will occur and the laser oscillation will stop. The causes of arc occurrence at high repetition are regarded to be the following remaining behind in the discharge space and disturbing the electric field at the time when the next pulse voltage is applied: (1) gas density depletion (the gas is heated instantly and the gas density of the discharge portion drops several percent) [1,2]; (2) ions (the negative ions having long lifetimes remain) [3]; (3) shock waves (those with Mach number of 1 to 3 repeat reflection in the discharge space) [4,5]; (4) discharge products (sputtering materials of electrodes and so on float between electrodes) [6]; and (5) temperature rise of electrodes (the gas near electrodes is heated and local gas density nonuniformity occurs) [7]. However, the influences of the respective factors on arc occurrence have not been clarified.…”

Discontinuity breakdown on shock wave interaction with nanosecond discharge

“…Such configuration of the discharge section allowed to improve the homogeneity of the main ͑spatial͒ discharge. 11,12 The chamber's a͒ Author to whom correspondence should be addressed. Electronic mail: dkoroteev@yandex.ru.…”

A single-filament schlieren method for flowing characteristic measurements in the pulsed gas lasers

“…There have been lots of methods applied in repetitively pulsed gas lasers to study the characteristics of the flow field after energy deposition such as pressure probe measurements [7,11,14], interferometry [9,15,16] and Schlieren method [1,14,17]. The pressure probe has been employed on the chamber wall to record the temporal evolution of the pressure fluctuation amplitude.…”

“…Longitudinal and transverse deflections caused by acoustic waves can be obtained by placing the knife edge in the vertical and horizontal positions respectively. This system has been improved by changing the knife edge into a split photodiode [17], and it has been used to measure the gas temperature profile of the heated gas in discharge region as well as the gas velocity. Spatial-resolved information can be given by scanning the interested region, while time-resolved information at the setting position of laser beam can be obtained for each pulse.…”