Hi,
nice picture auf an electron track in my new spark projection chamber. The chamber works with argon at reduced pressure (200 mbar) and pulsed voltage of about 10 kV. The pulse is triggered by a geiger tube under the chamber.
Thomas
Archived - Spark Chamber
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Rapp Instruments
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Archived - Spark Chamber
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Carl Willis
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Re: Spark Chamber
Nice project, Thomas.
I have seen a spark chamber operate at the Griffith Park Observatory museum in Los Angeles. Simple concept, but endlessly entertaining.
Getting the photo probably took some effort also. Thanks for sharing, and keep up the fine work.
-Carl
I have seen a spark chamber operate at the Griffith Park Observatory museum in Los Angeles. Simple concept, but endlessly entertaining.
Getting the photo probably took some effort also. Thanks for sharing, and keep up the fine work.
-Carl
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Scott Fusare
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Re: Spark Chamber
Great work Thomas!
Can you provide more details on the triggering? It sounds as if you are not using coincidence triggering? Also, what are you using for a HV switch? Classically spark chambers have used hydrogen thyratrons but it has always seemed to me that there were other ways to accomplish the task.
Regards
Scott
Can you provide more details on the triggering? It sounds as if you are not using coincidence triggering? Also, what are you using for a HV switch? Classically spark chambers have used hydrogen thyratrons but it has always seemed to me that there were other ways to accomplish the task.
Regards
Scott
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Rapp Instruments
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Re: Spark Chamber
Hi Scott,
You are right, I used only one counter below the chamber to trigger. Because of the tube sides are shielded by lead most of the counts are from electrons of a small sr 90 source which crossed the chamber. It's a projection chamber, which means that the discharges are perpenticular to the track. For switching the high voltage I used a homemade sparkgap. With argon I had to use rather low pressure of about 200 mbar to get tracks. The chamber works better with neon at atmospheric pressure, but most of the expensive gas (I have ordered 12 liter for 120 Euro) I have use already. At atmosperic pressure you get more discharges per line.
Thomas
You are right, I used only one counter below the chamber to trigger. Because of the tube sides are shielded by lead most of the counts are from electrons of a small sr 90 source which crossed the chamber. It's a projection chamber, which means that the discharges are perpenticular to the track. For switching the high voltage I used a homemade sparkgap. With argon I had to use rather low pressure of about 200 mbar to get tracks. The chamber works better with neon at atmospheric pressure, but most of the expensive gas (I have ordered 12 liter for 120 Euro) I have use already. At atmosperic pressure you get more discharges per line.
Thomas
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Wilfried Heil
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Re: Spark Chamber
Nice experiment! Would it be possible to seal the chamber, if it is filled with neon at atmospheric pressure or maybe a helium/neon mixture?
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Rapp Instruments
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Re: Spark Chamber
Hi Wilfried,
I think it should be possible to seal the chamber. Perhaps a light overpressure would prevent air from entering the chamber. Mostly oxygen with it's electronegative properties catch the free electrons and prevent normal operation of the chamber. I have tried to use helium which should also work nicely. But I only have ballon gas, which contains up to 10 percent of air and don't work in the chamber. But pure helium should be much cheaper than neon. A mixture of neon/helium 75/25 called henogal was often used in sparkchambers.
Thomas
I think it should be possible to seal the chamber. Perhaps a light overpressure would prevent air from entering the chamber. Mostly oxygen with it's electronegative properties catch the free electrons and prevent normal operation of the chamber. I have tried to use helium which should also work nicely. But I only have ballon gas, which contains up to 10 percent of air and don't work in the chamber. But pure helium should be much cheaper than neon. A mixture of neon/helium 75/25 called henogal was often used in sparkchambers.
Thomas
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Doug Coulter
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Re: Spark Chamber
Nice work!
One of the things that has impressed me most was a large spark chamber at the New York World's fair in the '60s, and I've wanted one ever since. The one on display there was nearly 3 foot cube and was showing cosmic rays, blue sparks along their tracks (probably air at atmosphere). It was made of plexiglass, with aluminum plates spaced about one inch.
I do plan to build one too at some point, but have been doing thought and other experiments on the way there. Most of the ones I've seen use very thick metal plates to get the required flatness, so the spark jumps where it should (only), and use large area detectors one above, and one beneath (all this for cosmics which will easily go through the whole thing). The thick metal plates on most will also cause showers of secondaries, and this is very pretty -- the ultimate geek coffee table ornament.
I tested a large area detector that worked great, so simple it's embarrassing. It was simply two sheets of iron metal (cheap sheet metal) about a foot square, separated by a couple of pieces of quarter inch glass tubing for insulation. Drove it with about 1.5 kv through a 1 meg series R and it worked just fine, decent sized pulses on every cosmic hit. All this just laying on the table, in air.
With a detector so numb, there's some doubt whether you'd need co-incidence at all, only a cosmic will do it, and to get to the detector under the spark chamber, it had to go though that first.
To solve the flatness problem, my thought is to use glass for the plates -- it's about the flattest inexpensive stuff around. You would metallize the glass with something like evaporated aluminum (another use for the fusor vacuum system) or best of all, maybe, ITO so it would stay "clear".
I would generate the high voltage via flyback, eg automotive spark coil, and use series resistors for each plate. I've tested that seperately and it works well, giving each plate a chance to spark, using about 20-30k resistors. The spark coil just sits there energized at about 2-3 amps till you want a spark, when you turn off the switch; a high voltage FET with a ZNR across it to limit the volts on the primary side. I don't think anything fancier is needed -- the spark just has to come before the ions recombine. So you get more time for that at lower gas pressures.
A small, all glass, transparent spark chamber on my coffee table is the goal. Martha Stewart, eat your heart out! Wonder how long ITO would last in this service? Maybe not real long if the sparks are high energy. Perhaps an all glass thing could be run at lower than atmospheric and low energy sparks used?
To make something like this work for the particles we are interested in for fusors would be quite a trick, as they are low energy compared to cosmics and wouldn't easily pass through things.
One of the things that has impressed me most was a large spark chamber at the New York World's fair in the '60s, and I've wanted one ever since. The one on display there was nearly 3 foot cube and was showing cosmic rays, blue sparks along their tracks (probably air at atmosphere). It was made of plexiglass, with aluminum plates spaced about one inch.
I do plan to build one too at some point, but have been doing thought and other experiments on the way there. Most of the ones I've seen use very thick metal plates to get the required flatness, so the spark jumps where it should (only), and use large area detectors one above, and one beneath (all this for cosmics which will easily go through the whole thing). The thick metal plates on most will also cause showers of secondaries, and this is very pretty -- the ultimate geek coffee table ornament.
I tested a large area detector that worked great, so simple it's embarrassing. It was simply two sheets of iron metal (cheap sheet metal) about a foot square, separated by a couple of pieces of quarter inch glass tubing for insulation. Drove it with about 1.5 kv through a 1 meg series R and it worked just fine, decent sized pulses on every cosmic hit. All this just laying on the table, in air.
With a detector so numb, there's some doubt whether you'd need co-incidence at all, only a cosmic will do it, and to get to the detector under the spark chamber, it had to go though that first.
To solve the flatness problem, my thought is to use glass for the plates -- it's about the flattest inexpensive stuff around. You would metallize the glass with something like evaporated aluminum (another use for the fusor vacuum system) or best of all, maybe, ITO so it would stay "clear".
I would generate the high voltage via flyback, eg automotive spark coil, and use series resistors for each plate. I've tested that seperately and it works well, giving each plate a chance to spark, using about 20-30k resistors. The spark coil just sits there energized at about 2-3 amps till you want a spark, when you turn off the switch; a high voltage FET with a ZNR across it to limit the volts on the primary side. I don't think anything fancier is needed -- the spark just has to come before the ions recombine. So you get more time for that at lower gas pressures.
A small, all glass, transparent spark chamber on my coffee table is the goal. Martha Stewart, eat your heart out! Wonder how long ITO would last in this service? Maybe not real long if the sparks are high energy. Perhaps an all glass thing could be run at lower than atmospheric and low energy sparks used?
To make something like this work for the particles we are interested in for fusors would be quite a trick, as they are low energy compared to cosmics and wouldn't easily pass through things.
Why guess when you can know? Measure!
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Richard Hull
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Re: Spark Chamber
Don't forget aquadag spray coatings on glass for conductivity.
Archived this due to the fascinating nature of the device. For further work, reports and images please post under new topic in the radiation forum. Our own HEAS group's Tim Raney made a nice little spark detector demo. Nice work.
Richard Hull
Archived this due to the fascinating nature of the device. For further work, reports and images please post under new topic in the radiation forum. Our own HEAS group's Tim Raney made a nice little spark detector demo. Nice work.
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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David D Speck MD
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Re: Spark Chamber
There is a special place in my heart for "The World's Largest Cosmic Ray Spark Chamber" that was featured at the NY 1964-65 World's Fair. It was in the exit rotunda of the GM Futurama ride. I have all the parts needed to replicate it, and about 4 years ago, I corresponded with Prof. Donald Meyer, at U. Michigan, who consulted with GM to build it.
A good deal of info about the chamber, as well as several photos of it can be found at:
http://www.worldsfaircommunity.org/inde ... entry23503
You may have to fix a line wrap to make the link work.
Regrettably, the World's Fair site had a crash a couple of years back, and several of the photos have been lost. I kept copies on a computer at home and can send them to anyone interested.
Dave Speck
A good deal of info about the chamber, as well as several photos of it can be found at:
http://www.worldsfaircommunity.org/inde ... entry23503
You may have to fix a line wrap to make the link work.
Regrettably, the World's Fair site had a crash a couple of years back, and several of the photos have been lost. I kept copies on a computer at home and can send them to anyone interested.
Dave Speck