Re: Van de Graaff /Pelletron (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Sun, 18 Jan 2004 00:34:13 +0100
From: Finn Hammer <f-h@xxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Van de Graaff /Pelletron (fwd)

All,

I think that the top voltage will be limited to (slightly more than) the
air breakdown value of the sum of the gaps btwn. the pellets. The
distance from the chain to the top terminal could then be considered the
safety factor.
If the pellets are designed well (and why bother to make them if they
are not?) this should be the value of a uniform field, 30kv/cm. With a
top voltage of 600kV, the distance btwn. pellets would have to amount
to: 600/30=30cm and if the pellets are 4 times as long as the gap btwn.
them, the total length occupied with chain, would then be 30*5=150 cm,
or 60".
The average opstanding john would find his head level with the top
terminal of such a device.

That seems well-proportioned to me.

Running a VDG in a pressurized tank with exotic gasses may be tempting
as a thought experiment, the voltages obtainable would provide great
boasting value, but frankly seems rather boring in real life.
We want direct access to the discharge, don`t we?.

Cheers, Finn Hammer

High Voltage list wrote:

> Original poster: Steven Roys <sroys@xxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Sat, 17 Jan 2004 14:47:38 -0500
> From: dave pierson <davep@xxxxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: Re: Van de Graaff /Pelletron (fwd)
>
>
>
>>I guess all of those who've looked at those pictures again have come up
>>with our own way of making a "belt".  In thinking about that I came up
>>with a fundamental question which might inhibit further efforts.  If the
>>individual pellets are conducting, which seems necessary, don't their
>>edges form a chain of little spark gaps
>>
>
>     Sort of.
>
>
>>and isn't the maximum output voltage for a given length limited by
>>
>
>  >breakdown between the pellets?
>      Sort of.
>
>     There is no voltage difference between the pellets,
>     as such, that is (thought experiment):
>
>         IF the belt were removed, there would be no difference.
>
>
>  >If so, it would seem that to get interesting voltages the machine would
>  >have to be run in an insulating gas under pressure.
>     I THINK the voltage is strictly that due to the end terminals,
>     and specifically, due to the charge accumulated
>     thereon.  This is the same limit as  imposed by
>     sparking down the column of a conventional vdG,
>
>     If I'm mthinking clearly...
>
>
>>	Comments?
>>
>
>     As bove.
>     8)>>
>        best
>       dwp
>
>
>