> On December 21, Bill Sloman wrote:
>>> I recall working on an arc lamp power supply, which used
>>> a spark gap for ignition.
>>> I wondered, and still do, are there any design techniques
>>> or formulas, to obtain a specific desired voltage pulse
>>> across the gap? Or is it cut and try, regarding the gap size
>>> and current? (the current break, that is)
>>
>> You can buy high voltage spark gaps - the one I bought for that job in
>> 1972 was glass-enclosed tube with an inert gas filling.
>> At the tine I'd bought a copy of a 1920's text book on the conduction pf
>> electricity through gases, for which there was already a well
>> established theory - search on Paschen's Law.
>> https://en.wikipedia.org/wiki/Paschen%27s_law
>> My first spark gaps was made in the workshop, and used two steel
>> ball-bearings to form the gap, mounted in a silica glass tube,
>> The arc lamp was exposed to the UV light from the spark, and that help
>> start the lamp. The glass in the store-bought spark gaps wasn't UV
>> transparent and the light they emitted didn't start the lamp nearly as
>> often.
>
> I looked at the Paschen theory, it's complicated. I find it hard to believe
> that Joe Engineer uses that to design spark gaps.
He uses as much of it as he needs.
> I'm more curious as to what precision one can achieve a desired pulse
> amplitude and shape. Or maybe it doesn't matter, the process is robust?
The process of initiating an arc starts with a single charge carrier -
usually an electron - showing up in the gap to start the process. Cosmic
rays will do it, or potassium-40 nearby. That happens at random.
> Looking at the physics, you have to specify the geometry, solve the field
> equations, control the transition slope of the (non-ideal) switch, etc.
> Note that ionization is sensitive to the E field, not voltage.
> Maybe EEsof can handle it -
It gets a lot simpler in practice. The questions tend to be - does what
we have work at all? And if the answer is yes, how do we change it to
make it work better?
--
Bill Sloman, Sydney
Reply by RichD●December 30, 20232023-12-30
On December 21, Bill Sloman wrote:
>> I recall working on an arc lamp power supply, which used
>> a spark gap for ignition.
>> I wondered, and still do, are there any design techniques
>> or formulas, to obtain a specific desired voltage pulse
>> across the gap? Or is it cut and try, regarding the gap size
>> and current? (the current break, that is)
>
> You can buy high voltage spark gaps - the one I bought for that job in
> 1972 was glass-enclosed tube with an inert gas filling.
> At the tine I'd bought a copy of a 1920's text book on the conduction pf
> electricity through gases, for which there was already a well
> established theory - search on Paschen's Law.
> https://en.wikipedia.org/wiki/Paschen%27s_law
> My first spark gaps was made in the workshop, and used two steel
> ball-bearings to form the gap, mounted in a silica glass tube,
> The arc lamp was exposed to the UV light from the spark, and that help
> start the lamp. The glass in the store-bought spark gaps wasn't UV
> transparent and the light they emitted didn't start the lamp nearly as
> often.
I looked at the Paschen theory, it's complicated. I find it hard to believe
that Joe Engineer uses that to design spark gaps.
I'm more curious as to what precision one can achieve a desired pulse
amplitude and shape. Or maybe it doesn't matter, the process is robust?
Looking at the physics, you have to specify the geometry, solve the field
equations, control the transition slope of the (non-ideal) switch, etc.
Note that ionization is sensitive to the E field, not voltage.
Maybe EEsof can handle it -
--
Rich
Reply by Anthony William Sloman●December 28, 20232023-12-28
On Wednesday, December 27, 2023 at 7:24:07 AM UTC+11, Carlos E.R. wrote:
> On 2023-12-26 06:20, Bill Sloman wrote:
> > On 26/12/2023 12:06 am, Carlos E.R. wrote:
> >> On 2023-12-22 01:03, RichD wrote:
> >>> I recall working on an arc lamp power supply, which used
> >>> a spark gap for ignition.
> >>>
> >>> I wondered, and still do, are there any design techniques
> >>> or formulas, to obtain a specific desired voltage pulse
> >>> across the gap? Or is it cut and try, regarding the gap size
> >>> and current? (the current break, that is)
> >>
> >> That's strange, an arc lamp is low voltage, high current. The ones I
> >> have seen needs the points to touch for an instant, then separate,
> >> either automatically or manually. During use, the points can be at a
> >> distance of about one centimetre.
> >>
> >> Using a a high voltage spark to initiate the thing? I don't know if
> >> that is possible, I have not seen it.
> >
> > The high pressure xenon arc lamps I built my power supply to drive were
> > being used as UV light sources in the Photochemistry group at
> > Southampton University.
> >
> > It took about 20kV to drive a spark between the electrodes, which dumped
> > enough xenon ions and electrons into the gap to sustain a glow discharge
> > for the few microsceconds it took for the tungsten electrode surface to
> > warm up enough to sustain an 24A arc at about 20v or so.
> >
> > They ran hot and were filled with a couple of atmospheres of xenon gas,
> > and relied on silica glass to keep the gas inside and the tungsten
> > electrodes spaced apart. Moving the electrodes wasn't an option.
> > Providing a third - trigger - electrode to allow easier starting was
> > possible, but not popular.
> >
> > I set up a stable constant current so the lamp provided a more or less
> > stable output - turbulent convection currents in the xenon gas meant
> > that it wasn't all that stable in the short term.
> Interesting.
>
> The tungsten wears out?
The arc mechanism relies on the tungsten surface getting hot enough to deform under the electric field into lot of very sharp spikes - sharp enough for field emission to take place.
The tungsten doesn't so much wear out as move around. You do get some positive ion bombardment at the cathode (xenon ions) which doesn't help.
--
Bill Sloman, Sydney
Reply by Phil Hobbs●December 26, 20232023-12-26
Joe Gwinn <joegwinn@comcast.net> wrote:
> On Tue, 26 Dec 2023 19:52:00 -0000 (UTC), Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> Carlos E.R. <robin_listas@es.invalid> wrote:
>>> On 2023-12-25 17:58, Joe Gwinn wrote:
>>>> On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
>>>> <robin_listas@es.invalid> wrote:
>>>>
>>>>> On 2023-12-22 01:03, RichD wrote:
>>>>>> I recall working on an arc lamp power supply, which used
>>>>>> a spark gap for ignition.
>>>>>>
>>>>>> I wondered, and still do, are there any design techniques
>>>>>> or formulas, to obtain a specific desired voltage pulse
>>>>>> across the gap? Or is it cut and try, regarding the gap size
>>>>>> and current? (the current break, that is)
>>>>>
>>>>> That's strange, an arc lamp is low voltage, high current. The ones I
>>>>> have seen needs the points to touch for an instant, then separate,
>>>>> either automatically or manually. During use, the points can be at a
>>>>> distance of about one centimetre.
>>>>>
>>>>> Using a a high voltage spark to initiate the thing? I don't know if that
>>>>> is possible, I have not seen it.
>>>>
>>>> It's how Xenon flash lamps are triggered. The big capacitor is
>>>> charged less than 1 KVolt, which isn't enough for such a long gap (the
>>>> length of the fused quartz flash tube). The trigger wire is wrapped
>>>> around the flash tube and when pulsed with 10 or 20 KV, causes a
>>>> conductive path to form in the Xenon gas (about 0.1 Bar) within, and
>>>> boom!
>>> Ah, ok, yes.
>>>
>>> But there is no conductivity between the high voltage and low voltage parts.
>>>
>>
>> Gas lasers and CFLs are started by a HV transient on the terminals.
>
> As can the flash lamp - it was sometimes done that way.
>
> The advantage of the capacitive coupling (through the fused quartz
> lamp tube wall) is that the 20 KVolt pulse does not appear on the 1 KV
> terminal or circuit, a simplification.
>
> Joe Gwinn
>
Big flashlamps are usually run in simmer mode. A small, constant anode
current greatly reduces both electrode wear and trigger jitter.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Reply by Carlos E.R.●December 26, 20232023-12-26
On 2023-12-26 06:20, Bill Sloman wrote:
> On 26/12/2023 12:06 am, Carlos E.R. wrote:
>> On 2023-12-22 01:03, RichD wrote:
>>> I recall working on an arc lamp power supply, which used
>>> a spark gap for ignition.
>>>
>>> I wondered, and still do, are there any design techniques
>>> or formulas, to obtain a specific desired voltage pulse
>>> across the gap? Or is it cut and try, regarding the gap size
>>> and current? (the current break, that is)
>>
>> That's strange, an arc lamp is low voltage, high current. The ones I
>> have seen needs the points to touch for an instant, then separate,
>> either automatically or manually. During use, the points can be at a
>> distance of about one centimetre.
>>
>> Using a a high voltage spark to initiate the thing? I don't know if
>> that is possible, I have not seen it.
>
> The high pressure xenon arc lamps I built my power supply to drive were
> being used as UV light sources in the Photochemistry group at
> Southampton University.
>
> It took about 20kV to drive a spark between the electrodes, which dumped
> enough xenon ions and electrons into the gap to sustain a glow discharge
> for the few microsceconds it took for the tungsten electrode surface to
> warm up enough to sustain an 24A arc at about 20v or so.
>
> They ran hot and were filled with a couple of atmospheres of xenon gas,
> and relied on silica glass to keep the gas inside and the tungsten
> electrodes spaced apart. Moving the electrodes wasn't an option.
> Providing a third - trigger - electrode to allow easier starting was
> possible, but not popular.
>
> I set up a stable constant current so the lamp provided a more or less
> stable output - turbulent convection currents in the xenon gas meant
> that it wasn't all that stable in the short term.
Interesting.
The tungsten wears out?
--
Cheers, Carlos.
Reply by Phil Hobbs●December 26, 20232023-12-26
john larkin <jl@650pot.com> wrote:
> On Tue, 26 Dec 2023 19:52:00 -0000 (UTC), Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> Carlos E.R. <robin_listas@es.invalid> wrote:
>>> On 2023-12-25 17:58, Joe Gwinn wrote:
>>>> On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
>>>> <robin_listas@es.invalid> wrote:
>>>>
>>>>> On 2023-12-22 01:03, RichD wrote:
>>>>>> I recall working on an arc lamp power supply, which used
>>>>>> a spark gap for ignition.
>>>>>>
>>>>>> I wondered, and still do, are there any design techniques
>>>>>> or formulas, to obtain a specific desired voltage pulse
>>>>>> across the gap? Or is it cut and try, regarding the gap size
>>>>>> and current? (the current break, that is)
>>>>>
>>>>> That's strange, an arc lamp is low voltage, high current. The ones I
>>>>> have seen needs the points to touch for an instant, then separate,
>>>>> either automatically or manually. During use, the points can be at a
>>>>> distance of about one centimetre.
>>>>>
>>>>> Using a a high voltage spark to initiate the thing? I don't know if that
>>>>> is possible, I have not seen it.
>>>>
>>>> It's how Xenon flash lamps are triggered. The big capacitor is
>>>> charged less than 1 KVolt, which isn't enough for such a long gap (the
>>>> length of the fused quartz flash tube). The trigger wire is wrapped
>>>> around the flash tube and when pulsed with 10 or 20 KV, causes a
>>>> conductive path to form in the Xenon gas (about 0.1 Bar) within, and
>>>> boom!
>>> Ah, ok, yes.
>>>
>>> But there is no conductivity between the high voltage and low voltage parts.
>>>
>>
>> Gas lasers and CFLs are started by a HV transient on the terminals.
>>
>> Cheers
>>
>> Phil Hobbs
>
> Series trigger transformer?
>
> Krytrons have a seperate trig terminal and a keep-alive electrode.
>
>
Nah, just a high (inductive) impedance, like a magneto.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics,
Electro-optics, Photonics, Analog Electronics
Reply by Carlos E.R.●December 26, 20232023-12-26
On 2023-12-26 21:08, Joe Gwinn wrote:
> On Tue, 26 Dec 2023 19:52:00 -0000 (UTC), Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> Carlos E.R. <robin_listas@es.invalid> wrote:
>>> On 2023-12-25 17:58, Joe Gwinn wrote:
>>>> On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
>>>> <robin_listas@es.invalid> wrote:
>>>>
>>>>> On 2023-12-22 01:03, RichD wrote:
>>>>>> I recall working on an arc lamp power supply, which used
>>>>>> a spark gap for ignition.
>>>>>>
>>>>>> I wondered, and still do, are there any design techniques
>>>>>> or formulas, to obtain a specific desired voltage pulse
>>>>>> across the gap? Or is it cut and try, regarding the gap size
>>>>>> and current? (the current break, that is)
>>>>>
>>>>> That's strange, an arc lamp is low voltage, high current. The ones I
>>>>> have seen needs the points to touch for an instant, then separate,
>>>>> either automatically or manually. During use, the points can be at a
>>>>> distance of about one centimetre.
>>>>>
>>>>> Using a a high voltage spark to initiate the thing? I don't know if that
>>>>> is possible, I have not seen it.
>>>>
>>>> It's how Xenon flash lamps are triggered. The big capacitor is
>>>> charged less than 1 KVolt, which isn't enough for such a long gap (the
>>>> length of the fused quartz flash tube). The trigger wire is wrapped
>>>> around the flash tube and when pulsed with 10 or 20 KV, causes a
>>>> conductive path to form in the Xenon gas (about 0.1 Bar) within, and
>>>> boom!
>>> Ah, ok, yes.
>>>
>>> But there is no conductivity between the high voltage and low voltage parts.
>>>
>>
>> Gas lasers and CFLs are started by a HV transient on the terminals.
>
> As can the flash lamp - it was sometimes done that way.
>
> The advantage of the capacitive coupling (through the fused quartz
> lamp tube wall) is that the 20 KVolt pulse does not appear on the 1 KV
> terminal or circuit, a simplification.
It certainly simplifies things. The high voltage spike can destroy the
lower voltage parts. The design would have to cope with that.
--
Cheers, Carlos.
Reply by john larkin●December 26, 20232023-12-26
On Tue, 26 Dec 2023 19:52:00 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>Carlos E.R. <robin_listas@es.invalid> wrote:
>> On 2023-12-25 17:58, Joe Gwinn wrote:
>>> On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
>>> <robin_listas@es.invalid> wrote:
>>>
>>>> On 2023-12-22 01:03, RichD wrote:
>>>>> I recall working on an arc lamp power supply, which used
>>>>> a spark gap for ignition.
>>>>>
>>>>> I wondered, and still do, are there any design techniques
>>>>> or formulas, to obtain a specific desired voltage pulse
>>>>> across the gap? Or is it cut and try, regarding the gap size
>>>>> and current? (the current break, that is)
>>>>
>>>> That's strange, an arc lamp is low voltage, high current. The ones I
>>>> have seen needs the points to touch for an instant, then separate,
>>>> either automatically or manually. During use, the points can be at a
>>>> distance of about one centimetre.
>>>>
>>>> Using a a high voltage spark to initiate the thing? I don't know if that
>>>> is possible, I have not seen it.
>>>
>>> It's how Xenon flash lamps are triggered. The big capacitor is
>>> charged less than 1 KVolt, which isn't enough for such a long gap (the
>>> length of the fused quartz flash tube). The trigger wire is wrapped
>>> around the flash tube and when pulsed with 10 or 20 KV, causes a
>>> conductive path to form in the Xenon gas (about 0.1 Bar) within, and
>>> boom!
>> Ah, ok, yes.
>>
>> But there is no conductivity between the high voltage and low voltage parts.
>>
>
>Gas lasers and CFLs are started by a HV transient on the terminals.
>
>Cheers
>
>Phil Hobbs
Series trigger transformer?
Krytrons have a seperate trig terminal and a keep-alive electrode.
Reply by john larkin●December 26, 20232023-12-26
On Mon, 25 Dec 2023 11:58:46 -0500, Joe Gwinn <joegwinn@comcast.net>
wrote:
>On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
><robin_listas@es.invalid> wrote:
>
>>On 2023-12-22 01:03, RichD wrote:
>>> I recall working on an arc lamp power supply, which used
>>> a spark gap for ignition.
>>>
>>> I wondered, and still do, are there any design techniques
>>> or formulas, to obtain a specific desired voltage pulse
>>> across the gap? Or is it cut and try, regarding the gap size
>>> and current? (the current break, that is)
>>
>>That's strange, an arc lamp is low voltage, high current. The ones I
>>have seen needs the points to touch for an instant, then separate,
>>either automatically or manually. During use, the points can be at a
>>distance of about one centimetre.
>>
>>Using a a high voltage spark to initiate the thing? I don't know if that
>>is possible, I have not seen it.
>
>It's how Xenon flash lamps are triggered. The big capacitor is
>charged less than 1 KVolt, which isn't enough for such a long gap (the
>length of the fused quartz flash tube). The trigger wire is wrapped
>around the flash tube and when pulsed with 10 or 20 KV, causes a
>conductive path to form in the Xenon gas (about 0.1 Bar) within, and
>boom!
>
>Joe Gwinn
On Tue, 26 Dec 2023 19:52:00 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>Carlos E.R. <robin_listas@es.invalid> wrote:
>> On 2023-12-25 17:58, Joe Gwinn wrote:
>>> On Mon, 25 Dec 2023 14:06:06 +0100, "Carlos E.R."
>>> <robin_listas@es.invalid> wrote:
>>>
>>>> On 2023-12-22 01:03, RichD wrote:
>>>>> I recall working on an arc lamp power supply, which used
>>>>> a spark gap for ignition.
>>>>>
>>>>> I wondered, and still do, are there any design techniques
>>>>> or formulas, to obtain a specific desired voltage pulse
>>>>> across the gap? Or is it cut and try, regarding the gap size
>>>>> and current? (the current break, that is)
>>>>
>>>> That's strange, an arc lamp is low voltage, high current. The ones I
>>>> have seen needs the points to touch for an instant, then separate,
>>>> either automatically or manually. During use, the points can be at a
>>>> distance of about one centimetre.
>>>>
>>>> Using a a high voltage spark to initiate the thing? I don't know if that
>>>> is possible, I have not seen it.
>>>
>>> It's how Xenon flash lamps are triggered. The big capacitor is
>>> charged less than 1 KVolt, which isn't enough for such a long gap (the
>>> length of the fused quartz flash tube). The trigger wire is wrapped
>>> around the flash tube and when pulsed with 10 or 20 KV, causes a
>>> conductive path to form in the Xenon gas (about 0.1 Bar) within, and
>>> boom!
>> Ah, ok, yes.
>>
>> But there is no conductivity between the high voltage and low voltage parts.
>>
>
>Gas lasers and CFLs are started by a HV transient on the terminals.
As can the flash lamp - it was sometimes done that way.
The advantage of the capacitive coupling (through the fused quartz
lamp tube wall) is that the 20 KVolt pulse does not appear on the 1 KV
terminal or circuit, a simplification.
Joe Gwinn