Optical emission spectroscopy of deuterium and helium plasma jets emitted from plasma focus discharges at the PF-1000U facility

Abstract

Optical emission spectroscopy techniques were used to investigate the spectra of dense deuterium-plasma jets generated by high-current pulse discharges within the large PF-1000U facility and to estimate parameters of plasma inside the jets and their surroundings. Time-resolved optical spectra were recorded by means of a Mechelle®900 spectrometer. From an analysis of the deuterium line broadening, it was estimated that the electron concentration at a distance 57 cm from the electrode outlets amounted to (0.4–3.7) × 1017 cm−3 depending on the initial gas distribution and the time interval of the spectrum registration after the instant of the plasma jet generation. From the re-absorption dip in the Dβ profile, it was assessed that the electron concentration in the surrounding gas was equal to about 1.5 × 1015 cm−3. On the basis of the measured ratio of He II 468.6 nm and He I 587.6 nm line intensities, it was estimated that the electron temperature amounted to about 5.3 eV. Also estimated were some dimensionless parameters of the investigated plasma jets.

Comparison of optical spectra recorded during DPF-1000U plasma experiments with gas-puffing

“…It should be noted that in comparison with the optical spectra observed in the previous PF-1000 experiments [2][3][4] the spectra recorded recently in the DPF-1000U facility without the gas-puffi ng showed negligible differences in lines shapes and intensities. Some examples of the optical spectra recorded at different instants before and after the discharge current peculiarity (the so-called current dip) are shown in Fig.…”

“…The optical emission spectroscopy (OES) has already been used for the investigation of intense pulsed plasma-ion streams generated with the use of the 1 MJ plasma focus facility [1][2][3][4], but recent modifi cations of this machine, and particularly the installation of the gas-puffi ng, have made it necessary to perform anew the detailed spectroscopic measurements. In this note the most important results are presented of experimental studies performed with the use of the modifi ed DPF-1000U facility without and with the gas-puffi ng.…”

Properties of toroidal magnetic fields in axial plasma flow on the PF-1000U plasma focus facility

“…Therefore, despite the huge difference in the parameters of astrophysical and laboratory plasma outflows (their sizes differ by 14-15 orders of magnitude, and characteristic densities and pressures by 15-16 orders of magnitude), they can be studied in the framework of the same system of equations (Ryutov & Remington 2002;Remington et al 2006). The first experiments showed that the conditions satisfying the basic laws of similarity, which make it possible to model the jets of young stars, are fulfilled in the PF-1000 (Skladnik-Sadowska et al 2016). It was also shown that in some modes of filling the chamber with working gas, compact plasma objects are formed, which retain their compactness when being spread over considerable distances (Krauz et al 2020).…”

The Study of Momentum and Energy of Plasma Flow Generated in Plasma Focus Discharge

“…Результаты последних экспериментов [9][10][11][12][13][14][15] показали, что они также являются эффективным инструментом для лабораторного моделирования одного из вариантов астрофизических джетов -струйных выбросов молодых звёздных объектов (YSO). В экспериментах на установках ПФ-3 [9-12, 14, 15], PF-1000 (Институт физики плазмы и лазерного микросинтеза, Варшава, Польша) [13,14] и КПФ-4 (ГНПО «СФТИ», Сухум, Абхазия) [14,15] продемонстрировано, что компактные плазменные образования могут распространяться на значительные расстояния от места генерации (~1 м), значительно превышающие их поперечные размеры. Для определения природы струйного выброса существенное значение имеет соотношение между плотностью потока энергии электромагнитного поля и плотностью кинетической энергии частиц.…”