(+ve was shorthand for positive, sorry if that was confusing, I won't use it again)
To be able to compare candidate scenarii on the basis of current waveforms, we should first ascertain how currents would behave in each case, trying not to digress too much (please show mercy for my limited proficiency in this foreign language). My suggestion was to start with the ion jet hypothesis (subject line), which may not be as absurd as you suggest BTW. In that hypothesis, do you agree with my assertion below that we should get identical and synchronous step waveforms for anode and cathode currents, or do you expect a delay allowing for the flight time? Michel ----- Original Message ----- From: "Horace Heffner" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Thursday, June 07, 2007 7:11 PM Subject: Re: [Vo]:Filament ion jets > > On Jun 7, 2007, at 4:57 AM, Michel Jullian wrote: > >> Hi Horace, >> >> Let's try to agree on simple things, in a simple example. Say at >> t=0 the HV is turned on instantly and the +ve anode's tip starts >> emitting a dotted line of slow-flying +ve ions > > > I'm curious - why do you use the notation +ve? Does the "e" represent > someting? I assume here you mean the needle is an anode of potential > +ve, and the plate is ground. Hopefully you are not implying the > filament is comprised of single molecule charged ions? Single > molecule charged ions would distribute themselves across the area of > the plates, following the field lines. The only hope of maintaining > anything like a filament or jet is a high m/q ratio, which charged > drops provide to a degree, and continuous filaments provide as well. > Also, I think Bill said a metal target plate accumulated water, which > would be consistent with either a droplet or water filament model. > Such models are also consistent with the need to keep the environment > wet, humid, or full of CO2. Say, maybe flowing water provides a way > to visualize the filament - a powdered dye on a metal plate. When it > gets wet it changes color. Only good for a one time shot, but it > still would be impressive and maybe could be engineered to leave a > permanent trace for study. > > >> which won't arrive before t=50ms. Say the flow of charge is a >> constant 10nA flowing out of the tip. The anode current waveform is >> therefore a step function, zero for t<0, 10nA for t>=0. What I am >> saying is that the cathode current is exactly the same step >> function, as it would be for any electronic component, without a >> delay corresponding to the flight time, i.e. cathode current won't >> wait for 50ms to turn on. Do you agree with this? > > > No, not necessarily. Bill said the filaments were fairly neutral, > and a pair could in fact travel parallel and close to each other for > long distances. I therefore don't think the majority of the current > flows until the filament completes contact with the plate, in which > case the filament conducts current through itself. I think the > voltage and thus the repulsion between two *conducting* filaments > declines as the point of observation approaches the ground plate. > > I agree that in the *droplet model* the current onset would be > immediate, as the droplets carried off the charge. We clearly are > basing (biasing) our assumptions regarding conductivity depending on > our personal models of the situation. In the filament model there > are two currents involved: (1) the current that leaves some charges > on the filament which is assembled from polar molecules held in place > primarily by their polar (hydrogen bond) attraction with the > alignment coordinated by the tip field E, and (2) the conduction > current that occurs when contact is "made" between the two > electrodes. If we knew the surface area of the filament we could > compute the current required to eject a filament at velocity V and > maintained at needle potential ve. > > I think it is an interesting question as to the exact mechanics the > allows the formation of a jet instead of droplets. It may relate to > the voltage, the power supply characteristics, the needle geometry, > and maybe the resistance and surface physics of the needle. It may > be highly related to the manner in which the needle attracts and > feeds water and/or CO2 to the jet. It certainly should be affected > by the surface tension at the needle tip, and thus may be highly > related to the thickness of the water feed to the tip, and to the > chemistry of the water, i.e. its CO2 content. But first there is a > need to prove the continuous filament exists at all and to detect its > presence and characteristics. > > Even without an imposed AC signal, the two plate method may be useful > for determining the presence of filaments vs. drops. The experiment > would consist of (1) establishing a current with the needle over one > plate and (2) then moving the needle electrode back and forth between > the centers of the two plates slowly, maintaining the current. Given > two adjacent coplanar target plates, each with its own nano-ammeter, > and slowly moving a source needle from above one to above the other, > we would see the current jump from one plate to the other very fast > if a filament were involved, and more gradually switch between the > two plates if droplet current transmission were involved, especially > at longer needle-plate separations. If lots of filaments from the > source electrode were involved, we should still see the change in > currents occur in jumps, while if droplet conduction is occurring > then the transition of signal strengths would be more continuous. > > Another way to diagnose filament vs drop formation at the needle tip > is through current fluctuations. If very pure DC is used, then an > oscilloscope probe wire attached to the needle, but capacitively > isolated from the needle using a small value high voltage capacitor, > should be able to detect the difference between ejection of droplets > vs a continuous jet. Droplets would cause a ripple in current and > voltage, while a jet would form with a smooth waveform. > > Regards, > > Horace Heffner > >
