Contamination-free sounding rocket Langmuir probe

Amatucci, W. E.; Schuck, P. W.; Walker, D. N.; Kintner, P. M.; Powell, Steven P.; Holback, B.; Leonhardt, D.

doi:10.1063/1.1357234

Cited by 50 publications

(33 citation statements)

References 17 publications

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“…1,34 A sign of dirty probes can be a hysteresis, i.e., a different I -V curve for the upwards and downwards sweep phase. 35,36 Indeed, hysteresis can be observed on newly installed probes on TORPEX. Keeping the probes in ion saturation current during plasma discharges of several minutes sputter cleans the probe and removes this hysteresis permanently.…”

Section: Appendix: Single Langmuir Probes In Torpex Plasmasmentioning

confidence: 99%

Practical solutions for reliable triple probe measurements in magnetized plasmas

Theiler

Furno

Kuenlin

et al. 2011

Review of Scientific Instruments

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The triple probe method to obtain local, time-resolved measurements of density, electron temperature and plasma potential is investigated in detail. The difficulties in obtaining reliable measurements with this technique are discussed and overcome. These include phase delay errors, ion sheath expansion and limited bandwidth due to stray capacitance to ground. In particular, a relatively simple electronic circuit is described to strongly reduce stray capacitance. Measurements with the triple probe are presented in a plasma characterized by interchange-driven turbulence in the TORPEX device. The measured time-averaged and time-dependent, conditionally averaged parameters are cross-checked with other Langmuir probe based techniques, and show good agreement. Triple probe measurements show that electron temperature fluctuations are sufficiently large, such that the identification of plasma potential fluctuations with fluctuations of the floating potential is not a good approximation. Over a large radial region, the time-averaged fluctuation-induced particle flux can, however, be deduced from floating potential only. This is because the phase shift between density and electron temperature is close to zero there and temperature fluctuations do not give rise to a net radial particle transport.

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Section: Appendix: Single Langmuir Probes In Torpex Plasmasmentioning

confidence: 99%

Practical solutions for reliable triple probe measurements in magnetized plasmas

Theiler

Furno

Kuenlin

et al. 2011

Review of Scientific Instruments

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“…As a heating device, the halogen lamp was applied in the elds of crystal growth, 38,39 the thermoforming process, 40 and surface contaminant removal. 41 Taking polysilicon growth as an example, the tungsten-halogen lamp array was used to heat the substrate and provided a high temperature ramp rate as well as a high uniform radiation intensity. 38 Consequently, the halogen lamp was used for the detection of explosives in this work.…”

mentioning

confidence: 99%

Non-contact halogen lamp heating assisted LTP ionization miniature rectilinear ion trap: a platform for rapid, on-site explosives analysis

Chen

Hou

Xiong

et al. 2013

Analyst

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A platform consisting of a halogen lamp, a low temperature plasma (LTP) probe, and a miniature rectilinear ion trap mass spectrometer (RIT-MS) has been constructed and evaluated to detect organic and inorganic explosives on solid surfaces. This platform features two attractive characteristics: high sensitivity for the explosives with low volatility, and rapid analysis speed for the explosives on large surface areas. With non-contact heating by the halogen lamp, the signal intensities for the explosives with relatively high volatility were improved by over an order of magnitude, compared to those obtained at room temperature; and even more, the explosives with low volatility, which could hardly be detected at room temperature, were able to be readily identified. The limits of detection (LODs) of the selected explosives were all at the picogram level (e.g., 10 pg and 20 pg for TNT and RDX, respectively) with a heating time of 3 s. Using manual surface swabbing, the analysis of explosives on a large surface area (7.5 cm Â 2.5 cm) was accomplished within 10 s, and an acceptable sensitivity could be acquired; additionally, inorganic explosives (black powder and firecracker) were successfully detected. Without any sample pretreatment, the platform was used to analyze the wastewater from an explosives factory, confirming the existence of 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT), and the concentration of TNT was determined to be 5 ng mL À1. All these results indicated that the proposed platform was a promising technique for security monitoring and environmental analysis.

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“…In normal operation, in order to map out the characteristic in reproducible discharges, the probe bias is scanned as the current is recorded. As the probe surface becomes contaminated, hysteresis is observed depending on whether the bias voltage is incrementally increased or decreased [88,89]. In Section 2.2, we discuss this problem in more detail.…”

Section: Diagnosticmentioning

confidence: 99%

Experimental investigation of the trigger problem in magnetic reconnection

et al. 2011

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Magnetic reconnection is a fundamental process in plasma physics, which involves the often explosive release of magnetically stored energy in both space and laboratory plasmas. In order for this sudden release of energy to occur, there must be a period of slow reconnection, in which magnetic stress accumulates in the system, followed by a quick transition to fast reconnection. The question of what causes this transition is known as the 'trigger problem' and is not well understood.We address the trigger problem using the Versatile Toroidal Facility (VTF) at MIT, which we operate in the strong magnetic guide field regime. The resulting reconnection occurs in spontaneous events, in which there is a transition to fast reconnection. The reconnection in these events is asymmetric: it begins at one toroidal location and propagates toroidally in both directions. The spontaneous onset is facilitated by an interaction between the x-line current channel and a global mode, which breaks axisymmetry. We model the onset using an empirical Ohm's law and current continuity, which is maintained by ion polarization currents associated with the mode. The model reproduces the exponential growth of the reconnection electric field, and the model growth rate agrees well with the experimentally measured growth rate.We begin, however, by discussing reconnection in the collisional regime and the effect of neutral gas on plasma flows. We perform experiments which are relevant to plasmas at the edge of tokamaks, but may also be applicable to reconnection in the solar photosphere and the interstellar medium, where the ionization fraction is low. In these experiments, a plasma filament propagates across a magnetic field in a background of neutral atoms. The filament motion is driven by charge separation in an inhomogeneous magnetic field, and this drive is balanced by collisional damping. The filament propagation and internal structure are described in detail.

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Contamination-free sounding rocket Langmuir probe

Cited by 50 publications

References 17 publications

Practical solutions for reliable triple probe measurements in magnetized plasmas

Practical solutions for reliable triple probe measurements in magnetized plasmas

Non-contact halogen lamp heating assisted LTP ionization miniature rectilinear ion trap: a platform for rapid, on-site explosives analysis

Experimental investigation of the trigger problem in magnetic reconnection

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