We study the propagation of streamer discharges through air and along an epoxy rod with an ICCD camera. We use stroboscopic imaging at frequencies up to 110 MHz to visualize discharge evolution and to calculate velocities. Initial results show that surface streamers along a dielectric surface can be up to twice as fast as streamers through bulk air

Ebert, U. (Ute)

Nijdam, S. (Sander)

Trienekens, D.J.M. (Dirk)

English

Trienekens, D.J.M.

Nijdam, S.

Ebert, U.

NARCIS 

Stroboscopic images of streamers through air and over dielectric surfaces

CWI's Institutional Repository

2400 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 42, NO. 10, OCTOBER 2014Stroboscopic Images of Streamers ThroughAir and Over Dielectric SurfacesDirk J. M. Trienekens, Sander Nijdam, and Ute EbertAbstract— We study the propagation of streamer dischargesthrough air and along an epoxy rod with an ICCD camera.We use stroboscopic imaging at frequencies up to 110 MHz tovisualize discharge evolution and to calculate velocities. Initialresults show that surface streamers along a dielectric surfacecan be up to twice as fast as streamers through bulk air.Index Terms— Imaging, surface discharges.IN HIGH voltage devices, breakdown may occur becausedischarges seem to move more easily over insulatingsurfaces than through bulk gas [1]. In this paper, we usestroboscopic imaging to study these surface discharges.To generate discharges, a positive high voltage pulsebetween 10 and 17 kV [see Fig. 1(f)] is supplied by a chargedcapacitor that discharges after a spark gap is triggered toa needle placed 16 cm above a grounded cathode plane.A stainless steel sample holder containing an epoxy rod(4 mm in diameter) is placed on the cathode plane, in such away that the top of this rod is 6 mm below and 35 mm to theside of the needle. Our experiments were performed in air, atpressures between 40 and 100 mbar.To image the discharge, we use a LaVision PicoStar HR12camera system. We send a pulse train of tunable length andfrequency to the intensifier. This way, we are able to performstroboscopic imaging of the discharge. By controlling thenumber of pulses and the frequency, we are able to controlthe number of gating cycles and the time between these gates.By measuring the monitor output of the intensifier, we areable to relate the timing of the camera to the voltage pulse[see Fig. 1(f)].With stroboscopic imaging, we are able to study the spatialand temporal evolution of the discharge in two dimensions.Due to the stochastic behavior of the discharges it is notpossible to compare different discharges, and although a streakcamera would allow us to study the spatial and temporal evolu-tion of the discharge, this would only yield accurate results fordischarges that propagate in a well-defined direction. For theManuscript received November 3, 2013; revised January 29, 2014 andApril 25, 2014; accepted June 23, 2014. Date of publication July 15, 2014;date of current version October 21, 2014. This research is supported by ABBand the Dutch Technology Foundation STW, which is part of the NetherlandsOrganisation for Scientific Research (NWO), and which is partly funded bythe Ministry of Economic Affairs.D. J. M. Trienekens and S. Nijdam are with the Department of Physics,Eindhoven University of Technology, Eindhoven 5612 AZ, The Netherlands(e-mail: d.j.m.trienekens@tue.nl; s.nijdam@tue.nl).U. Ebert is with CWI Amsterdam, Amsterdam 1098 XG, The Netherlands(e-mail: ute.ebert@cwi.nl).Color versions of one or more of the figures in this paper are availableonline at http://ieeexplore.ieee.org.Digital Object Identifier 10.1109/TPS.2014.2335615highly nonreproducible discharges that propagate in multipledirections that we are studying, stroboscopic imaging yieldsthe best results.Pancheshnyi et al. [2] have used the same technique to studystreamers, however, in their experiment the number of gatingcycles was limited to 6 due to the high velocity of the dischargeand the narrow gap. In our experiment, because of the lowerdischarge velocity and larger gap we can use up to 20 gatingcycles, allowing a more detailed study of discharge phenomenalike branching and the inception cloud.Fig. 1(a)–(c) shows the images obtained at 50-MHz inten-sifier gating. The needle and the contour of the dielectricrod are marked in white. The images clearly show theintermittent pattern caused by the stroboscopic gating. Threeparts of the discharge can be distinguished: 1) the inceptioncloud [3], [4]; 2) the bulk gas streamers; and 3) the surfacedischarge propagating along the epoxy rod. The number ofgating cycles is chosen so that the intensifier has zero gainwhen the discharge reaches the cathode, to prevent the imagingof secondary streamers.Information on the inception cloud is relatively hard toderive, since the 3-D morphology of the cloud makes it harderto distinguish the maxima and minima in the intensity. To gainmore information, we can reduce the gating frequency and stillstudy the entire discharge [Fig. 1(d)], or we can zoom-in viewon this part of the discharge [Fig. 1(e)].The images show that the surface discharges are faster thanthe bulk gas streamers. The velocity of bulk gas streamers wasdetermined from the longest streamers, which are assumedto have a small deviation from the vertical image plane.Under the present conditions, we find that surface dischargesare typically a factor ∼2 faster. Bulk gas streamers propagateat around 2 ·105 m/s, compared with (4–5)·105 m/s for surfacestreamers. Inception cloud velocities as low as ∼1 · 105 m/sare observed just before the inception cloud breaks up intoseparate channels.REFERENCES[1] A. Sobota et al., “Speed of streamers in argon over a flat surface of adielectric,” J. Phys. D, Appl. Phys., vol. 42, no. 1, p. 015211, 2009.[2] S. Pancheshnyi, M. Nudnova, and A. Starikovskii, “Development ofa cathode-directed streamer discharge in air at different pressures:Experiment and comparison with direct numerical simulation,” Phys.Rev. E, vol. 71, no. 1, pp. 16407-1–16407-12, 2005.[3] T. M. P. Briels, E. M. van Veldhuizen, and U. Ebert, “Time resolvedmeasurements of streamer inception in air,” IEEE Trans. Plasma Sci.,vol. 36, no. 4, pp. 908–909, Aug. 2008.[4] S. Nijdam, G. Wormeester, E. M. van Veldhuizen, and U. Ebert, “Probingbackground ionization: Positive streamers with varying pulse repetitionrate and with a radioactive admixture,” J. Phys. D, Appl. Phys., vol. 44,no. 45, p. 455201, 2011.0093-3813 © 2014 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.TRIENEKENS et al.: STROBOSCOPIC IMAGES OF STREAMERS THROUGH AIR AND OVER DIELECTRIC SURFACES 2401Fig. 1. Stroboscopic images of streamers through air and over dielectric surfaces in air for various pressures and voltages are presented in panels (a)–(e).The anode tip and the dielectric rod are marked in white. The repetition rate of the discharges was 3 Hz. A typical voltage pulse and the monitor outputof the intensifier are presented in panel (f). Streamers visible in the top of the image originate from the needle holder. They do not influence the streameroriginating from the needle tip to the best of our knowledge.

Stroboscopic images of streamers through air and over dielectric surfaces

Abstract

Similar works

Full text

Available Versions

NARCIS

CWI's Institutional Repository

Repository TU/e

Pure OAI Repository

NARCIS

Crossref

Pure OAI Repository