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(a) Cross sectional view of vacoflux-50 showing curvature surface at one edge. Other two figure shows FEMM simulation of field lines for (b) edge of vacoflux-50 is curved and for (c) edge of vacoflux-50 is sharp (rectangular) when core is magnetized with 150 A magnet current (I mag). Solid line shows the field line.
Source publication
This paper presents a detail characterization of Argon plasma confined by a multi-pole line cusp magnetic field (MMF) over a large cylindrical volume (1 m axial length and 40 cm diameter) [Patel et al., Rev. Sci. Instrum. 89, 043510 (2018)] and various magnetic field scaling with magnet current obtained from the magnetic field simulation in the vac...
Citations
... This magnetic field configuration is widely used in plasma sources because of its role in confining the plasma and reducing particle loss. The applications of multi-cusp magnetic fields encompass a broad spectrum of topics [1][2][3][4][5][6][7][8][9][10][11][12]. The most common application resides in the field of ion source development, where these fields have yielded enhancements in the confinement of hot and bulk electrons [13,14]. ...
To realize the development of a long plasma source with a uniform electron density distribution in the axial direction, the spatial distribution of plasma under a multi-cusp magnetic field was analyzed using a KEIO-MARC code. Considering a cylindrical plasma source with an axial length of 3000 mm and a cross-sectional diameter of 100 mm, in which the filament electrode was the electron source, the electron density distribution was calculated using the residual magnetic flux density, Bres, and the number of permanent magnets installed at different locations surrounding the device, Nmag, as design parameters. The results show that both Bres and Nmag improved the uniformity of the electron density distribution in the axial direction. The maximum axial electron density decreased with increasing Nmag and increased with increasing Bres. These trends can be explained by considering the nature of the multi-cusp field, where particles are mainly confined to the field-free region (FFR) near the center of the plasma column, and the loss of particles due to radial particle transport. The use of multiple filaments at intervals shorter than the plasma decay length dramatically improved axial uniformity. To further improve axial uniformity, the filament length and FFR must be properly set so that electrons are emitted inside the FFR.
... The coexistence of two distinct species of electrons at different temperatures is very common in space plasmas 13,31 and laboratory plasmas. 32,33 Theoretical studies by Cairns 34 and Nishihara and Tajiri 35 had shown that the presence of non-thermal electrons or plasmas with two electron temperatures can significantly modify the ion acoustic solitary structures. The propagation of ion-acoustic waves in twoelectron temperature plasma has been studied by Jones et al., 36 both experimentally and theoretically, and it has been shown that a small fraction of hot electrons can affect the propagation of the wave. ...
... In the present work, the effect of two-electron temperature on the properties of ion-acoustic solitons are studied in a multi-pole line cusp plasma device (MPD). 32,33 The special feature of this device is the controllability of the magnitude of the pole magnetic fields by varying the currents in electromagnets used for producing the cusp magnetic fields. This controllability of the cusp magnetic field strength at the poles facilitates the production of two-temperature electrons in variable proportions. ...
... The present experiment is carried out in a multi-pole line cusp plasma device (MPD). 32,33 An MPD consists of six rectangularshaped electromagnets with profiled core material to produce the variable multi-pole line cusp magnetic field. These electromagnets provide uniqueness in varying the magnetic field strength and configuration. ...
This article presents the experimental observations and characterization of ion acoustic solitons (IASs) in a unique multi-pole line cusp plasma device (MPD), in which the magnitude of the pole-cusp magnetic field can be varied. In addition, by varying the magnitude of the pole-cusp magnetic field, the proportion of the two-electron-temperature components in the filament-produced plasmas of the MPD can be varied. The solitons are experimentally characterized by measuring their amplitude-width relation and Mach numbers. The nature of the solitons is further established by making two counter-propagating solitons interact with each other. Later, the effect of the two-temperature electron population on soliton amplitude and width is studied by varying the magnitude of the pole cusp-magnetic field. It has been observed that different proportions of two-electron-temperature significantly influence the propagation of IASs. The amplitude of the solitons has been found to be inversely proportional to the effective electron temperature (Teff).
... The usage of electromagnets in MPD facilitates the confinement of plasma with various cusp geometries and a wide range of magnetic field strengths. The characteristics of the filamentary produced argon plasma in MPD have been studied and reported before [23,24]. Drift waves [25] have been observed in the edge region of the Six Pole Six Magnet (SPSM) configurations in which the wave vector changing its direction has also been seen for the first time. ...
... The experiments reported here are performed in a linear cylindrical device MPD, which has been described before in previous studies [23,24]. The schematic of the MPD, its diagnostics, and coordinate system is shown in figure 1. ...
... Six electromagnets with 120 cm long rectangular bars of vacoflux embedded in copper coils are installed on the periphery of the cylindrical chamber with 60°azimuthal spacing. More details about these magnets are reported in [24]. The use of electromagnets in MPD, gives the flexibility to work with different multi-cusp geometries by changing the current directions in the said coils, while the field strength can be varied by changing the current values. ...
Two magnetic configurations of Multi-cusp Plasma Device (MPD) have been explored to obtain high quiescence level, large uniform plasma region with nearly flat mean density and temperature profiles. In particular, properties of plasma in a Six Pole Six Magnet (SPSM) and Twelve Pole Six Magnet (TPSM) cusp configurations are rigorously compared and reported here. It is found that more uniform plasma with nearly flat profiles is found in TPSM along with increased quiescence level. Findings are experimentally verified across various magnetic field strengths for both configurations.
... The usage of electromagnets in MPD facilitates the confinement of plasma with various cusp geometries and a wide range of magnetic field strengths. The characteristics of the filamentary produced argon plasma has been studied and reported before [16,17]. In the edge region of the six pole line configurations, drift waves have been observed [18], while in the central region the plasma is very quiescent. ...
... The experiments reported here are performed in a linear cylindrical device MPD, which has been described before [16,17] and schematic of the MPD and its diagnostics in Figure 1. The device has a cylindrical chamber of 150 cm length and 40 cm diameter and 0.6 cm thick wall made of stainless steel. ...
A Multi-pole line cusp Plasma Device (MPD) built using six electromagnets is capable of producing six poles six magnets (SPSM) and twelve poles six magnets (TPSM) cusp configuration. In this article, a detailed experimental study of the plasma parameters in these two multi-pole line cusp geometries is presented. SPSM has a very small field-free region (extending up to R=4 cm) compared to TPSM (which extends up to R=10 cm). The radial variation of plasma parameters for various, magnetic field strengths, is presented. The uniformity in radial and azimuthal variation of plasma parameters is observed to be comparable to the radial extent of field-free regions in both cusp configurations. The variation is <5% up to R=4 cm and R=0 cm in SPSM and TPSM respectively. The plasma is quiescent over a larger volume for TPSM compared to SPSM. The experimental investigation of plasma parameters in SPSM and TPSM provides very strong evidence that the magnetic field profiles of cusp magnetic field configuration play a crucial role in determining the uniformity of plasma parameters and plasma quiescence level. The different aspects of wave excitation in plasma can be studied in the background of this enhanced volume of plasma uniformity and quiescence in TPSM.
... The ion-acoustic wave propagation study is performed in a cylindrical Multi-pole line cusp Plasma Device (MPD). 37,38 This device has the facility to operate with or without a magnetic field, and for the present experiments, the MPD is used as an unmagnetized linear plasma device. The schematic of the experimental setup is shown in Fig. 1. ...
An experimental study of Ion Acoustic (IA) wave propagation is performed to investigate the effect of neutral density for Argon plasma in an unmagnetized linear plasma device. The neutral density is varied by changing the neutral pressure, which, in turn, allows the change in ion-neutral, and the electron-neutral collision mean free path. The collisions of plasma species with neutrals are found to modify the IA wave characteristics such as the wave amplitude, the velocity, and the propagation length. Unlike the earlier reported work where neutrals tend to heavily damp the IA wave in the frequency regime ω<νin (where ω is the ion-acoustic mode frequency and νin is the ion-neutral collision frequency), the experimental study of the IA wave presented in this paper suggests that the collisions support the wave to propagate for longer distances as the neutral pressure increases. A simple analytical model is shown to qualitatively support the experimental findings.
