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Effect of neutral pressure on the He plasma flow measurement in a linear device

Title
Effect of neutral pressure on the He plasma flow measurement in a linear device
Author
정규선
Keywords
Plasma flow; Unmagnetized Mach probe; Ion-neutral collision; Divertor simulator; Helium plasma
Issue Date
2012-03
Publisher
Elsevier
Citation
Current Applied Physics, Vol.12, No.6 [2012], p1497 ~ 1502
Abstract
Axial and azimuthal flow velocities have been measured in a linear plasma device called NAGDIS-II (NAGoya DIvertor Simulator-II), along with plasma density and electron temperature, using a vector Mach probe composed of two Mach probes, one of which is for the axial flow, and the other is for the azimuthal flow. To study the effect of neutral pressure on the deduction of the Mach numbers, the ratio of upstream to downstream currents are measured by changing the neutral pressure for the deduction of flow velocities. Helium plasma was generated with pressure of 2-35 mTorr. Since the ion gyro-radius at the magnetic flux of 300 G is larger than the probe size, an unmagnetized collisionless Mach probe theory was used for the deduction of Mach numbers and their variations. In order to check the range of collisionality, plasma density (ne = 1010-1011 cm-3) and electron temperature (Te = 2-9 eV) are measured by a single electric probe using a conventional collisionless probe theory. Variations of Mach number, electron temperature and plasma density with collisionless models are to be compared with those using collisional models for different pressures where ionization and ion-neutral collision are included. Mach numbers by the collisionless model are found to be overestimated by 120% for the maximum difference even in weakly collisional plasmas. A clear flow reversal exists in the axial direction with higher pressure plasma, even in the linear machine. Azimuthal flows are also measured simultaneously along with axial flows, yet they seem to be very small in the present cold ion plasma (Ti/Te << 1).
URI
https://www.sciencedirect.com/science/article/pii/S1567173912001630http://hdl.handle.net/20.500.11754/67604
ISSN
1567-1739
DOI
10.1016/j.cap.2012.04.024
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > ELECTRICAL AND BIOMEDICAL ENGINEERING(전기·생체공학부) > Articles
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