[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: [TCML] magnetic controlled spark gap



hmm thats weird. It is a one page editorial thing from a  scientific paper... type thing. looks old. i can open it just fine with out paying 30$. I can't save it so, I will type what it says. there are 2 diagrams but i can't get those.
J. s a . INSTRUM., 1963, VOL. 40
L E T T E R TO THE E D I T O R S
A magnetically controlled spark gap

A low inductance spark gap is described, utilizing the breakdown between coaxial cylinder
electrodes with a transverse magnetic field at low pressure. The device can be triggered
magnetically and it can be used as a ?clamp switch?.
At low pressure the sparking potential between coaxial
cylinder electrodes depends on the strength of the axial
magnetic field. Typical breakdown curves for this electrode
configuration are shown in figure 1. For a range of values 
of the magnetic field breakdown only occurs at a low potential
if the inner electrode is positive. Theories of breakdown
under these conditions have been put forward in terms of the
equivalent pressure due to electrons traversing cycloidal
paths in the presence of the magnetic field (Somerville 1952;
Redhead 1958). It has been suggested (Blevin 1961 unpublished)
that a ?clamp switch? could be constructed using these
characteristics. The concentric cylinder geometry ensures a
low inductance decice.
The general arrangement of the spark gap is shown in
figure 2. It consisted of concentric cylinder electrodes supported
by a 3 in. internal diameter, 6 in. long Q.V.F. tube.
The inner electrode was a 3/4 i n . outside diameter and the
outer a 2 in. inside diameter copper tube. Stress relief on
the ends of the electrodes was accomplished by the domed
end of the inner electrode, whereas in the case of the outer
electrode a copper ring was edge brazed on to the tube. The
end plates (brass) were machined to take OS42 O-rings and
a connector plate to accept 10 cables (UR42) provided a low
inductance connection. The connection to the vacuum pump
entered through one of the end plates.
The magnetic field coil was wound on a Paxolin tube, and
a total of 660 turns of 14 a.w.g. enamelled wire allowed the
range of operating fields to be obtained by using currents up
To enable satisfactory operation the gap was pumped to
5 nitorr. The gap described had a breakdown potential in
the absence of a magneric field of 50 kv.
To operate as a clamp switch the magnetic field is set
between H, and H2 (figure 1). Breakdown will not occur
with the inner electrode negative up to 50 kv. Conduction
takes place when the inner electrode is driven positive.
Triggered operation of the spark gap can be accomplished
by applying a magnetic field at the desired instant. This
allows complete isolation of the trigger from the rest of the
circuit. it is possible to set the magnetic field to a value
just too low to cause conduction, then to inject a pulse in the
magnetic circuit suficient for conduction to occur. The low
initial value of the magnetic field could be supplied by a
permanent magnet.
With a magfietic field greater than H,, fast rising long
tailed voltage pillses (1-50 waves, etc.) can be chopped at
any level by adjusting the magnetic field. Thus the device
can be used in conjunction with a standard impulse generator
to produce chopped waves of repeatable characteristics.
The controlled spark gap has also functioned as a high
voltage rectifier; for this condition the magnetic field was set
between H , and H2. The spark gap operated at 13CmA:
IC kv for 15 minutes. It may be possible to develop a
rectifier from this device suitable for charging capacitor banks,
etc.
The work described above was carried out at the Marchwood
Engineering Laboratories of the Central Electricity
Generating Board and this letter is published by permission
of the Director of the Laboratories.

sorry for the long post
-------------- Original message -------------- 
From: "Lau, Gary" <Gary.Lau@xxxxxx> 

> The link provided only prompts one to purchase the article: 
> A magnetically controlled spark gap 
> D Harcombe, R T Palmer and C F Gozna 1963 J. Sci. Instrum 
> for $30. Have you seen the article, or an abstract? 
> 
> 
> Regards, Gary Lau 
> MA, USA 
> 
> 
> > -----Original Message----- 
> > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On 
> > Behalf Of jhowson4@xxxxxxxxxxx 
> > Sent: Saturday, September 13, 2008 12:00 AM 
> > To: tesla list 
> > Subject: [TCML] magnetic controlled spark gap 
> > 
> > http://www.iop.org/EJ/article/0950-7671/40/9/118/siv40i9p468.pdf?request- 
> > id=b5fffc4a-5483-45fd-99ce-4c1d72710536 
> > 
> > hey guys found this while looking for something else thought you would be 
> > interested. 
> > _______________________________________________ 
> > Tesla mailing list 
> > Tesla@xxxxxxxxxxxxxx 
> > http://www.pupman.com/mailman/listinfo/tesla 
> _______________________________________________ 
> Tesla mailing list 
> Tesla@xxxxxxxxxxxxxx 
> http://www.pupman.com/mailman/listinfo/tesla 
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla