Fast plasma discharge capillary design as a high power throughput soft x-ray emission source

Abstract

We present the experimental details and results from a low energy but high repetition rate compact plasma capillary source for extreme ultraviolet and soft x-ray research and applications. Two lengths of capillary are mounted in two versions of a closely related design. The discharge operates in 1.6 and 3.2 mm inner diameter alumina capillaries of lengths 21 and 36 mm. The use of water both as dielectric and as coolant simplifies the compact low inductance design with nanosecond discharge periods. The stored electrical energy of the discharge is approximately 0.5 J and is provided by directly charging the capacitor plates from an inexpensive insulated-gate bipolar transistor in 1 μs or less. We present characteristic argon spectra from plasma between 30 and 300 Å as well as temporally resolved x-ray energy fluence in discrete bands on axis. The spectra also allow the level of ablated wall material to be gauged and associated with useful capillary lifetime according to the chosen configuration and energy storage. The connection between the electron beams associated with the transient hollow cathode mechanism, soft x-ray output, capillary geometry, and capillary lifetime is reported. The role of these e-beams and the plasma as measured on-axis is discussed. The relation of the electron temperature and the ionization stages observed is discussed in the context of some model results of ionization in a non-Maxwellian plasma.

Radiative properties of non-equilibrium nitrogen plasma in soft x-ray range

“…6. Излучательная способность плазмы в связно-связанных переходах при температуре 80 эВ для теплового распределения электронов (maxwell -черная линия) и с учетом ускоренных электронов с долями 1% и 0.5% и средними энергиями 1.5 и 3 кэВ (красная и зеленая линии)…”

“…Лазерная плазма возникает при воздействии одного или нескольких сфокусированных лазерных импульсов одинаковой или различной длины волны излучения на твердую или жидкую мишень [1,2], газовую струю [3] в вакуумной камере. Разрядная плазма производится при инициации разряда электрического тока в капилляре, заполненном смесью газов [4][5][6], или электрической дуги [7]. Также применяется комбинированный или гибридный подход с использованием твердой или жидкой мишени: первоначальное воздействие лазерного импульса приводит к испарению и предионизации вещества мишени, последующий нагрев плазмы производится при электрическом разряде [7][8][9].…”

Soft X-Ray Emission Analysis Of A Pulsed Capillary Discharge Operated In Nitrogen

“…The charging circuit delivers approximately 0.5J directly to one capacitor plate in less than 1µs, delivering voltages of 18-24kV. This charging circuit has been discussed in detail previously [5]. The upper half of the capacitor plates and alumina capillary are shown in Figure 1.…”

Observations of soft X-ray emission and plasma dynamics of a compact capillary discharge operated in xenon

“…The small size of the emitting source is compatible with soft X-ray microscopy in the water window band (23-44 Å ), of great interest to the biological sciences 6 and also for soft X-ray metrology and microscopy at 135 Å . 7 The experimental results of this work were obtained in a low stored energy, low inductance discharge that exploits the Transient Hollow Cathode Mechanism (THCM) 5,8 in order to obtain a volume initiated discharge, as opposed to a wall initiated discharge where the plasma lifts off from the wall. This results in a spectrum mostly of the filling gas, as it has been demonstrated in discharges in nitrogen 9 and in argon, 8 although presence of wall material is more evident in the case of nitrogen.…”

“…7 The experimental results of this work were obtained in a low stored energy, low inductance discharge that exploits the Transient Hollow Cathode Mechanism (THCM) 5,8 in order to obtain a volume initiated discharge, as opposed to a wall initiated discharge where the plasma lifts off from the wall. This results in a spectrum mostly of the filling gas, as it has been demonstrated in discharges in nitrogen 9 and in argon, 8 although presence of wall material is more evident in the case of nitrogen. The THCM capillary discharges are selftriggered as the hollow cathode generated axial electron beam causes a returning ionization wave leading to breakdown.…”