Re: Van de Graaff generator safety question (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 15 Jan 2004 11:00:07 -0700
From: Gomez <gomez@xxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Van de Graaff generator safety question (fwd)


On Thursday, January 15, 2004, at 09:58  AM, High Voltage list wrote:

> Original poster: Steven Roys <sroys@xxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Wed, 14 Jan 2004 14:57:06 -0200
> From: Antonio Carlos M. de Queiroz <acmq@xxxxxxxxxxxxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: Re: Van de Graaff generator safety question (fwd)
>
> High Voltage list wrote:
>>
>> From: Dr. Resonance <resonance@xxxxxxxxxx>
>>
>> Yes, we built one about 12 years ago.  Current increase, as compared
>> to a
>> belt, is approx 1,200%.
>
> This doesn't seem possible. The belt in a regular VDG operates already
> close to the limit of charge density that would cause ionization of
> the air. The conductive sections of a pelletron chain would at most
> operate at this same density. The current is always directly
> proportional to the area per second of charge transport surface that
> reaches the terminal. For a given belt speed, it's very difficult to
> get something better than what a belt can give.

  I believe you have hit upon one of the advantages of a chain - insane
surface speeds.  Although I could not find any mention of the chain
operating speed on National Electrostatics' web site, they do mention
that their pulleys are quite large (30cm - 60cm dia) which implies a
high surface speed.  And they mention their very high charging currents:

	"Depending on the particular design options,	the system delivers
charging currents of 100
	- 200 A or more per chain to the high voltage
	terminal."