Plasma dynamics in a hollow cathode triggered discharge with the influence of fast electrons on ionization phenomena and EUV emission

Abstract

The 2-D computational code Z* is used to simulate physical phenomena in hollow cathode triggered lowpressure capillary discharge at different phases of the process: electron beam generation, formation of a channel by ionization wave, and discharge dynamics together with ionization kinetics and plasma emission, particularly in EUV band interesting for applications. Runaway electrons in gas-filled capillary discharge with hollow cathode play an important role both in ionization wave propagation, and in ionization of multicharged ions in discharge plasma. The electron beam prepares a tight ionized channel. The fast electrons shift the ionization equilibrium in discharge plasma increasing the EUV emission from relatively low-temperature plasma of argon or xenon. At ionization wave stage, the electron flow is simulated in electron-hydrodynamic model. At discharge stage, the plasma is described by the radiative magnetohydrodynamics with ionization kinetics and radiation transfer.

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

“…One such is the approximately 10:1 gas pressure ratio between the cathode entrance and the anode exit, thus requiring at least a two-dimensional dynamic calculation. Zakharov 35 undertakes this problem in a geometry close to ours and a discharge of similar peak current in a similar time scale. The authors find a significant axial variation of the density profile and significantly, for this work, that the EUV emission is from a submillimeter plasma region next to the anode, rather than a bulk or extended on axis plasma.…”

“…4 it may be seen from the filtered diode signals that there is still significant e-beam activity of keV energy at the time of hot plasma emission, but of an order of magnitude lower current than at the start of the breakdown. It is not possible to quantify the percentage of fast electron content in our experiment to use the results of Zakharov 35 directly. The presence of a strong short Ti-filtered diode signal, which is most sensitive to the Ar X to XII ionization stages seen in Fig.…”

“…This has been discussed in considerable detail in the modeling of the most similar discharge to the present work. 35 In particular, EUV emission is predicted to come from a relatively dense plasma formed in the initially low-density plasma near the anode. The predictions of this available model allow the best published theoretical comparisons to our experimental configuration.…”

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

“…Ранее было показано, что присутствие ускоренных электронов способно существенно повлиять на ионизационный состав плазмы средних и тяжелых элементов, населенности излучательных уровней и значительно повысить эффективность генерации излучения в нанометровом диапазоне [16,20]. По результатам проведенного моделирования азотной плазмы источников излучения в диапазоне 2.3-4.4 нм наличие ускоренных электронов в плазме позволяет достичь многократного увеличения спектральной эффективности излучения в диапазоне 2.3-3.0 нм для температуры плазмы около 40-50 эВ.…”

“…Для широкополосного излучения используются мишени на основе висмута и циркония с применением дифракционной оптики [14]. Однако присутствуют серьезные сложности с загрязнением вакуумной камеры и оптической системы из-за характерных особенностей данных материалов, поэтому их применение сильно снижает срок службы всей системы [15], а для разрядной плазмы крайне ограничено [16].…”