Wide-aperture Discharge Research Articles

Specific features of wide-aperture hollow cathode discharge in helium

The characteristics of wide-aperture discharge with a hollow cathode in helium have been studied under the conditions of predominating electron generation via photoemission from the cold cathode. In this regime, currents exceeding by an order of magnitude those for the conventional abnormal discharge have been obtained. The current-voltage characteristics are independent of the helium pressures in a range of 5–15 Torr, which is a distinctive feature of the photoemission dominated discharge with electron beam in the system under consideration.

Highly efficient electron beam generation in a wide-aperture discharge in helium

The paper deals with a gas discharge having electron beam generation efficiency η≃100% at a voltage U>300 V. The discharge has been realized in helium in a cell with a cathode diameter of 19.5 cm. The discharge features are a higher η as compared to other discharges, the presence of reverse bends in the voltage-current characteristics including the occurrence of a falling section, and nonmonotony in η(U) and its growth with increasing He pressure. The discharge peculiarities are explained by its photoemissive nature. The basic contribution to the photoemission is made by the emission from the resonance state excited in the secondary processes.

Specific features of wide-aperture glow discharge in helium

The characteristics of wide-aperture discharge in helium have been studied for a cathode diameter of 19.5 cm and a cathode-grid anode distance of 3 cm. It is established that the properties of discharge in this system are substantially different from those of a usual abnormal discharge. The difference is manifested in the bending of current-voltage characteristics, their pronounced dependence on the helium pressure, a nonmonotonic dependence of the electron beam generation efficiency η on the discharge voltage U, and an anomalously high efficiency (η ≈ 100%) in the range of U ≈ 350–1000 V.

A 100 mJ Table-Top Short Pulse Amplifier for 248 nm Using Interferometric Multiplexing

A polarization multiplexing method (based on Sagnac interferometer’s principle) was used in combination with a table-top wide aperture discharge pumped excimer amplifier to amplify femtosecond UV pulses. It is possible to optimize the operational conditions of the device within a wide range of input energies by changing the optical setup, while keeping the signal-to-noise ratio (short pulse – amplified spontaneous emission (ASE) ratio) of the pulses on a reasonably low value. The amplifier was tested for two different front ends. With ∼40 μJ input energy ∼50 mJ output energy was obtained in a 3-pass arrangement, and applying a seed pulse carrying an energy of around 2–3 mJ a maximum output energy of 100 mJ was reached in a single subpicosecond beam at 248 nm.

Saturation parameter and intensity of argon laser radiation

An investigation of an argon laser with a wide-aperture discharge tube led to the conclusion that the known reasons for saturation of the output power should be supplemented by saturation of quenching of the upper active level. The gas-pressure dependences of the radiation power and saturation parameter of the 488 nm line differed from the dependences obtained for the 514 nm line, indicating that electron quenching is not the only mechanism influencing the active levels of an excited ion in an argon laser plasma.

Spatial discharge narrowing in wide-aperture discharge pumped lasers

Narrowing of the discharge in wide-aperture transversely excited KrF excimer laser heads is shown as a result of the effect of the ground return at the outer boundary of the laser chamber on the electric field line distribution. It is shown theoretically and experimentally that it has a strong contribution to the electric field line distribution, while the electrode shape and separation are only of secondary importance. In order to avoid the narrowing effect, a compensated configuration is suggested.

Terawatt XeCl discharge laser system

A peak power of 1 TW has been obtained in a XeCl laser with a pulse width of 310 fsec. Amplified spontaneous emission was investigated extensively by changing the gain of wide-aperture discharge amplifiers. As a result, the amplified spontaneous emission content was suppressed to less than 3% in energy through the use of an appropriate spatial filter before the final amplifier and by operating at a low gain level of 4.8%/cm.

Picosecond excimer lasers.

A peak power of one terawatt has been obtained in XeCl with a pulse width of 310fs. Amplified spontaneous emission (ASE) was investigated extensively by changing the gain of wide aperture discharge amplifiers. As a result, the ASE content was suppressed to less than 3% in energy by using an appropriate spatial filter before the final amplifier along with operating at a low gain level of 4.8%/cm.