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Magnifier Gen


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From:  Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent:  Thursday, March 26, 1998 12:40 AM
To:  tesla-at-pupman-dot-com
Subject:  Magnifier Gen

Hi All,
          Here is the oil on the magnifier I used to get the scope 
pictures. It appears that it was not as well tuned as I thought 
either. According to my notes I didn't check primary tune at the time
and miscalculated its inductance and frequency into the bargain. The 
photos were scoped at a primary energy of 1.25J (no breakout) and 
2.3J. Anyhow, here are the specs:

Resonator: Rdc = 15.5 Ohms
           Dwire = 0.45mm  (Cu diameter)
           Pitch = 50TPI
           Turns = 540 - 550
           Hwinding = 10.9"
           Diameter = 3.1"
          
           Lcalc = 5.6mH
           Lmeas = 6.24mH !!  (Sencore L-C Analyser)
I haven't been able to explain this yet :(
          
           Former = acrylic tube
          
           Cself = 5.1pF  (excl corona shields)
           Cself (incl corona shields) = 6.7pF

FWIW I tested Medhurst on Electrum and found the answer to be as good 
as spot on.
          
           Fres (corona shields but no topload) = 780kHz           
           Fres (measured on the day with topload) = 462.65kHz       

Corona shields:    Top - 4.75" x 1.25" torus
                Bottom - 4.1" x 1.1" 
....................................................................

Driver Secondary: Former = HDPE gaspipe
                  Height = 6"
                  Diameter = 6.7"
                  Wire = 80 strand litz, strand diameter = 0.2mm
                  Lmeas = 344uH
                  Lcalc = 350uH  (much better)
                  Fself = 3.01MHz
                  Cself = 7.8pF
                  Turns = 53

Primary used in tests: Former = skeletal
                       Height = 3.9"
                       Diameter = 5.5"  (fits snuggly into secondary)
                       Turns = 5.25
                       Lmeas = 3.6uH
                       Lcalc = 3.3uH roughly.
I had thought it was around 4.5uH but I remember that figure came out 
when it was considerably more shortened.

Primary cap = CP 25nF  (about 25.5nF last time I checked).

Gives Fp about 525kHz (to be measured - or maybe better tuned).
......................................................................
The interesting bits:

Pri - Sec k = 0.526   Found by aiding/opposing method using the LC 
Analyser to get the inductances and running through
M = (L1-L2)/4, finally plugging that into the L/M/k formula.

Laiding = 382uH,  Lopposed = 308uH

System k measured at 0.086 off scope waveforms using k = 1/2xTxF 
where F was the ring frequency and T was half a beat length.

F was about 465kHz and T around 25uS.
......................................................................

Driver Q was pretty awful. I could see lottsa sparks inside the 
secondary former. It also showed up as a big loss on the scoped 
waveforms. Quench was generally third notch, occasionally second. 
That wonderful figure had everything to do with the primary losses 
and nothing to do with the gap which was a straight non-blown static.
Next round of tests will be done with the driver system oil filled 
which should improve it out of sight and maybe a different primary.

I have only got photos of no breakout waveforms back so far. the 
others are on a film still in the camera. It will be about a week 
before I get back to further testing during which time, something 
will be done about tuning and primary losses. I do remember that it 
did better in attached spark length with one fewer of the stacked 
terminals on top a couple of nights previously (about 11" sshot 
around 3J which is far from my best at that energy level).

Malcolm