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Magnifier 13 report


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From:  richard hull [SMTP:rhull-at-richmond.infi-dot-net]
Sent:  Wednesday, April 15, 1998 8:34 PM
To:  tesla-at-pupman-dot-com
Subject:  Magnifier 13 report

All,

Here is the first pass data on the H2 thyratron switch excited magnifier 13.
This was a cobbled up test of the new circuit coupled to the new large table
top magnifier.

Statistics of system:

Coil driver-  Primary: 13 turns of #8 THHN insulator wire tight wound and
tapped wound over top of the secondary for a K=.65-.78 based on tap point.
Taps are in steps from 32uh to 89uh.

             Secondary: 44 turns of #14 stranded TW wire- insulated. 910uh
total inductance.  Natural 1/4 wave frequency 1210khz. covered with 2 wraps
of 20mil polyethylene and overwound directly with primary.

             Coil form is 1/2" wall 16" diameter schedule 40 PVC 8" tall.


gap system/tank circuit:

gap effectively placed across a 0-7kvdc supply (current limited- 60ma).  A
.007ufd 20kv pulse rated capacitor is used as the driver tank capacitor.
Gap was a 5C22 hydrogen thyratron with grid drive circuit supplying a 3 us
300 volt pulse into 50 ohms.  This circuit was triggered by a 555 astable
oscilator which had over three decade range of pulse adjustability .1hz-2khz.

Insturmentation:

Pearson wideband current transformer,  Tektronix TDS 310 digital storage scope


Observations:

The current transformer indicated about a 50 amp pulse in the tank with
6KVDC applied.  The pulse was a single ping of 3us (thyratron pulse on time)
with no ring within the primary (thyratron is turned off with the reflex
from the magnetic collapse of the primary magnetic field  This is not seen
on the CT due to circuit opening within 100 nanoseconds after current pulse
zero crossing.  In short the primary was hit and never rung up.  A slug of
magnetic energy was dropped in the primary coil and then open circuited.

The scope was next placed about 8 feet from the system with a 12" whip for a
terminal in a BNC plug in channel 1 of the scope.  Depending on resonator,
the peak voltage recorded on the damped waves was 55v peak or 110volts pp.
It was noted the resonators rung for as many as 51 cycles per pop. showing
maximum Q was realized and there was no swap back and forth interaction
between the primary tank circuit and the driver secondary or the resonator.

This being the case, and as expected, the tuning of the primary made
absolutely no difference or had zero effect on the output frequency.  This
frequency was rigidly fixed as being that of the resonator alone and was
verified with scope measurements. The tuning did, as expected, influence the
current in the tank with the lowest tap inductance sending the tank current
to about 150 amps while the highest inductance point reduced it to about 40
amps.  (Changing the effective surge impedance of the tank)  The sparks were
thin and whispy and never exceeded three inches. (~70 watts input)  This
system was not optimized as it was thrown together on a first pass.

More data as things happen here.


Richard Hull, TCBOR