A dipole probe for electric field measurements in the LVPD

Abstract

This paper describes the design, construction, and calibration of an electric dipole probe and demonstrates its capability by presenting results on the measurement of electric field excited by a ring electrode in the Large Volume Plasma Device (LVPD). It measures the electric field in vacuum and plasma conditions in a frequency range lying between . The results show that it measures electric field 2 mV cm−1 for frequency . The developed dipole probe works on the principle of amplitude modulation. The probe signal is transmitted through a carrier of 418 MHz, a much higher frequency than the available sources of noise present in the surrounding environment. The amplitude modulation concept of signal transmission is used to make the measurement; it is qualitatively better and less corrupted as it is not affected by the errors introduced by ac pickups. The probe is capable of measuring a variety of electric fields, namely (1) space charge field, (2) time varying field, (3) inductive field and (4) a mixed field containing both space charge and inductive fields. This makes it a useful tool for measuring electric fields in laboratory plasma devices.

Plasma potential measurement using centre tapped emissive probe (CTEP) in laboratory plasma

“…In absence of electron temperature gradient, temperature fluctuation, and electron beam, the method provides accurate measurement of plasma potential. The method fairly supports its usage in plasmas where plasma density and electron temperature ranges between − − 10 10 m 11 18 3 and / ⩽ T eV 1 e p respectively. In fact, most of the plasmas in the laboratory scale satisfy this range.…”

“…But when plasma has finite electron temperature gradient (∇ ≠ T 0 e ) and temperature fluctuations (δ ≠ T 0 e ), consideration of such an assumption becomes invalid. In such situations, Langmuir probes and even the dipole probe [3] fails to provide right estimation of plasma potential and electric field and only emissive probes gives right measure of plasma potential and its fluctuations. Accurate measurement of DC and AC component of plasma potential is important to measure the electric field for estimating fluctuation induced particle transport, × E B drift, rotation and prediction of × E B driven instabilities etc.…”

Research on the magnetic flux leakage field distribution characteristics of defect in low-frequency electromagnetic detection technique

“…Meanwhile, the highsensitivity magnetoresistive (MR) sensor is always adopted as the signal acquisition medium [19,20,21], although it is affected greatly by spatial magnetic field. In addition, the magnetic dipole model [22,23,24,25,26,27,28,29,30] is one of the most mature theories used to explain the magnetic flux leakage field produced by an external DC or a permanent magnet, which can also directly analyze the relative change trend of LF-MFL field instead of the absolute value variation. In this study, the mathematical models of the LF-MFL field spatial distribution for four types of groove crack defects (rectangular, semicircular, trapezoidal, and V-shaped) with equal lengths and widths were established on the basis of the derivation of magnetic dipole theory.…”

Validation of a Lagrangian model for laser-induced fluorescence

“…In general, strong electric fields can be measured with deflections of particle beams [94,95] or spectroscopic techniques, such as Stark effect [96] and Lamb shift [97]. Weaker field measurements, on the other hand, are mostly obtained with probes or antennas [98]. Electrostatic fields can be computed from local measurements of the plasma potential using Langmuir probes [99] or emissive probes [100,101], while inductive electric fields generally require the knowledge of all currents in space and time so as to calculate the vector potential A [102,103].…”

“…Electrostatic fields can be computed from local measurements of the plasma potential using Langmuir probes [99] or emissive probes [100,101], while inductive electric fields generally require the knowledge of all currents in space and time so as to calculate the vector potential A [102,103]. In the case where both the electrostatic and inductive fields are present, dipolar probes are used [98,104,105].…”