Jim,
Nice write up and explanation. I read previously that not using a breakout
point of a nail tip, needle, pin (how is the pin attached - from the inside
of the toroid where the flat round end is touching the toroid and pin
breaks through the outside of the toroid to emit sparks?) will cause a 40%
reduction in spark length (vs having a breakout point) by having multiple
sparks randomly around the toroid.
It sounds to me that having a breakout point is the way to go for having
the longest spark length then. I will still build a bigger toroid with 8"
aluminum ducting but if you don't need the $20 a roll aluminum tape then a
breakout point should be the answer then.
Tim
On Thu, Apr 9, 2015 at 10:52 AM, Jim Lux <jimlux@xxxxxxxxxxxxx> wrote:
> On 4/9/15 7:38 AM, Timothy Gilmore wrote:
>
>> Thanks for sharing Doug.
>>
>> One question to the group...as I am building my new toroid, I was under
>> the
>> impression that a smooth surface like I saw with Doug's machined toroid
>> would provide only 1-2 sparks but I saw many like I get on my aluminum
>> ducting toroid. Is this the case also with machined toroids?
>>
>
>
> The science of spark development and growth is very poorly understood.
> There's a book "Spark Discharge" by Bazelyan and Raizer from about 10 years
> ago that has a lot of theory, but the summary is that "it's complex and
> hard to model"
>
> In my experience, smooth surfaces tend to have many sparks, because a
> spark can grow from one place as well as another. The whole "breakout
> point" thing (a thumbtack stuck to the toroid, or a screwdriver laying over
> the edge) is an attempt to create a preferential point from which sparks
> develop.
>
> The visible sparks you see are really the combination of many sparks. The
> individual sparks grow very quickly (nanoseconds), dissipating and
> reforming on every halfcycle of the RF. IN some cases, the sparks tend to
> follow the same path, extending the channel a bit more each time. In
> others, it doesn't.
>
> It is believed that there's an interaction between the size of the topload
> (which sets the energy available for each individual spark event) and the
> resonant frequency, and the bang rate.
>
> If you have a very smooth surface and a very uniform surroundings and a
> bit of air movement, each time a new little spark starts to form, it can
> form in a new place, because one place is as good as another, and the
> moving air disperses any residual "partly ionized" channel as well as
> cooling the topload.
>
> A narrow point, with no moving air, can
> a) provide a preferential spot for the spark to start
> b) get hotter, aiding in spark growth because hot things emit electrons
> c) leave the hot air from the previous spark in a convenient place.
>
> But there's a tradeoff.. if the spark forms too soon on the topload, it
> drains the energy out of the topload (being fed in from the secondary)
> before it has time to accumulate. If there's not enough energy to "feed
> the spark", it stops growing.
>
>
>
>
>
>
>
>> Tim
>>
>> On Thu, Apr 9, 2015 at 9:04 AM, Doug <doug11642@xxxxxxxxxxx> wrote:
>>
>> Working great; https://www.youtube.com/watch?v=4LTzJAashpQ
>>> Doug Johnson
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