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Re: Charge Carriers

Tesla List wrote:
> 
> Subscriber: music-at-triumf.ca Sat Dec 21 19:19:15 1996
> Date: Sat, 21 Dec 1996 09:17:25 PST
> From: "Fred W. Bach, TRIUMF Operations" <music-at-triumf.ca>
> To: tesla-at-pupman-dot-com
> Cc: music-at-triumf.ca
> Subject: Re: Charge Carriers
> 
> >Message-ID: <199612210625.XAA11163-at-poodle.pupman-dot-com>
> >Date: Fri, 20 Dec 1996 23:25:23 -0700
> >From: Tesla List <tesla-at-poodle.pupman-dot-com>
> >To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> >Subject: Re: Charge Carriers
> 
> >Subscriber: rwall-at-ix-dot-netcom-dot-com Fri Dec 20 23:00:14 1996
> >Date: Fri, 20 Dec 1996 10:53:40 -0800
> >From: Richard Wayne Wall <rwall-at-ix-dot-netcom-dot-com>
> >To: tesla-at-pupman-dot-com
> >Subject: Re: Charge Carriers
> >
> >12/20/96
> >
> >Fred Bach, all
> >
> >RH opines that TCs deposit eletrostatic charge on a receiver by an
> >"ionic acoustic wave".  Do you have any idea what the ion(s) are and
> >their associated energies, potentials and mean free paths?
> >
> >RWW
> 
>    I have been too busy to get into this discussion.  Too bad, since
>    it has been a good one.
> 
>    I think Richard Hull's "ionic acoustic wave" is a fair description.
>    but I wouldn't call it acoustic.  In sound, air molecules do not
>    travel themselves at the speed of sound but the wave does.  Same
>    with a cloud of ions.  Their movment rate depends on many things,
>    the wind for one.  The source does create its own wind by Coulomb
>    (ES) repulsion.
> 
>    In air I beleive the ions are O2 minus, O2 plus, O+ (possibly
>    O-minus) and the equivalent in nitrogen and various oxides of
>    nitrogen.  Also there can be charged ozone.  And if there is any
>    hydrogen around you can have naked protons.  H- is generated as
>    well but it is a very short-lived species (H- is our bread and
>    butter at TRIUMF for that is what we generate in the ion sources
>    and accelerate to 500 MeV then we strip off the electrons with a
>    foil and we have naked protons). I suppose someone could look up
>    the lifetimes of all of these species.  In air I don't have any
>    idea what the drift speeds are except to say that the speed of the
>    heavy positive ions in air is much lower than the speed of sound.
>    There are also naked electrons and these travel much faster.  The
>    difference in speed is a problem in some of our beam detectors when
>    the internal vacuum deteriorates.  The reading is stable as long as
>    the beam is stable in amplitude.  But let there be a dip in the
>    beam intensity and the negatives disappear first, leaving a huge
>    positive signal at the collector plates which gives the monitor a
>    false beam reading and shuts the beam off.  So we have installed
>    filters and appropriate time delays.  The effect is a function of
>    vacuum quality.
> 
>    If some HV AC source puts out a lot of both negative and positive
>    species into the air, and if you collect the negatives from the
>    air,  the net balance left over will be positive and everything
>    they land upon will take up a positive aftercharge in milliseconds
>    to seconds.   So in any of these experiments it is vital to measure
>    the voltage buildup on objects as a function of time.
> 
>    High voltage electric fields go right through insulators like
>    plastic so there is no surprize that insulating a HV AC ball does
>    not prevent air ionization on the other side.   All that is needed
>    on the far side is some sharp (ground) element to shape the field
>    down to a point.  The plastic does not have to get ionized in the
>    process.
> 
>    Cheers,
> 
>  Fred W. Bach ,    Operations Group        | Internet: music-at-triumf.ca
>


Fred,

Read with interest, your post.  You mention it is important to measure 
voltage build up with time.  Wow!  I could speak for hours on this.  I 
get a virtually instanteous slamming of the needle of the Keithley 
electrometer to 100 volts negative (-) on an isolated 12" ball of 12 pf 
measured capacitiy. (the insturment's own 12 pf of internal capacity now 
adjusts the total to 24pf).  However, I record a moderate rate of 
positive (+) accumulated coulombic charge on the same over a period of a 
few seconds from a 30 watt Tesla coil 4' distant.  This off course flies 
in the face of convention as according to q=cv the charge of 10^-8 
coulomb of charge on the input of the instrument recorded over 5 seconds 
shows the ball voltage should be 10^-8/24 X 10^-12 or 400 volts after the 
5 second period.  Now based on the time constant seen, a full second 
would be required to hit 100 volts.  I note that the time to -100 volts 
is a small fraction of a second on the voltmeter.  Also odd how the 
accumulated charge is positive inspite of the negative voltage 
indication.  I have checked with a mechanical lindemann and  
older condensing electroscope and verified the accumulated charge sign on 
the keithley as being correct.  It is still a mystery to me.  Both 
potential (voltage) and charge are scalar quantities and should answer 
the thought experiment and math. but seemingly don't.  I still wonder 
about the voltage mechanism of the electrodynamic reading Keithley. 
(voltage must fall through a resistive path to ground.)

Richard Hull, TCBOR