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Old 3rd May 2019, 12:02 pm   #21
Viewmaster
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Default Re: SparkChambers

Building now...…..
200mm dia x 200mm long acrylic cylinder with acrylic end plates.
Power supply slung under base acrylic, from 15kV NST I stripped from my old SGTC.


10 ali plates spaced 20mm apart on nylon spacers and bolts with HV on alternate plates.


Argon filled with telltale neoprene disc to show pressure increase as sparking will heat up gas. HV to be cut manually to start with.
Maybe auto later.

Model railway valves for Argon inlet/air outlet.

Non pulsed HV to start with, as the first spark chambers had this so
this is old fashion stuff.

PS. I haven't forgotten 'Bach with sparks,' but as I said somewhere for the moment it's on
'the bach burner.'
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Old 5th May 2019, 10:11 am   #22
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Default Re: SparkChambers

When a partical passing through my chamber ionises the Argon, ( I hope ),
the spark created will continue so I need to cut the HV after some
short time. As I am finding, switching 20kV plus HV is rather costly so I will make a short period timer to cut the mains supply to the NST, if I can
detect when a spark has been triggered by a partical and not spurious.


This is all a new ball game for me and the next part of the game is ordering
a small cylinder of Argon and a regulator.
to suit. I think these will fit the bill from Machine Mart who is near to me...……..

https://www.machinemart.co.uk/p/argon-gas-cylinder


https://www.machinemart.co.uk/p/bott...RoC6RQQAvD_BwE

Maybe I ought to train up as a gas engineer.
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Last edited by Viewmaster; 5th May 2019 at 10:19 am.
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Old 5th May 2019, 3:49 pm   #23
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Default Re: SparkChambers

Quote:
so I will make a short period timer
A resistor and capacitor, just like a Geiger counter?
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Old 25th May 2019, 7:25 pm   #24
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Default Re: SparkChambers

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Originally Posted by Philips210 View Post
I remember reading that helium is able to permeate through glass such as in valves and impair the vacuum. Is this a real possibility if the valve is exposed to helium?
I recall that when I worked on sector-field mass spectrometers, a way of finding where there was a leak in the vacuum system was to squirt a little helium around the suspect places while the mass spectrometer was tuned to 4 mass units. If a peak at 4 mass units was seen, that was where the leak was. This was pretty sensitive, as most of the joints would leak a little, anyway.

Isn't it true to imagine that if helium can diffuse through the glass envelope of a valve, then it can also leak out of the valve too? This will depend on the partial pressure of helium on either side of the glass, not the total pressure difference, surely?

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Old 25th May 2019, 10:48 pm   #25
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Default Re: SparkChambers

There's a well publicised issue of new iPhones using MMS resonators in vacuum packages instead of Quartz crystals. They are temporarily disabled by helium diffusion into the tiny vacuum chambers if there is raised helium density in the environment. Worth looking up as an illustration of helium diffusion.

David
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Old 26th May 2019, 5:30 am   #26
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Default Re: SparkChambers

Quote:
Originally Posted by ColinTheAmpMan1 View Post
Quote:
Originally Posted by Philips210 View Post
I remember reading that helium is able to permeate through glass such as in valves and impair the vacuum. Is this a real possibility if the valve is exposed to helium?
I recall that when I worked on sector-field mass spectrometers, a way of finding where there was a leak in the vacuum system was to squirt a little helium around the suspect places while the mass spectrometer was tuned to 4 mass units. If a peak at 4 mass units was seen, that was where the leak was. This was pretty sensitive, as most of the joints would leak a little, anyway.

Isn't it true to imagine that if helium can diffuse through the glass envelope of a valve, then it can also leak out of the valve too? This will depend on the partial pressure of helium on either side of the glass, not the total pressure difference, surely?

Colin.
There was a small (1cm radius or so) mass spectrometer called the 'minimass' I think made by AEI. It had a pre-set positon on the controls for 4 mass units, to be used as a leak detecctor as you suggest (go round the joints of the vacuum system with a jet of helium). I have such an instrument (the mass spectrometer head, big horseshoe magent and the control electronics) but no vacuum system to use it with.

As for helium diffusing out, this was certainly a problem with HeNe laser tubes when I was at school. They would lose the helium and stop working.
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Old 26th May 2019, 12:06 pm   #27
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Default Re: SparkChambers

The pictures remind me of my Jacob's Ladder, c/w HT lead and Gabriel (starter) electrode. ('Arc-Angel' pun courtesy of BigClive!) The two HV resistors in series are around 5Meg each. The run time isn't long enough to overheat the Tupperware, as the bolts act as a good heatsink.

Dave
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Old 26th May 2019, 6:56 pm   #28
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Default Re: SparkChambers

Quote:
Originally Posted by TonyDuell View Post

There was a small (1cm radius or so) mass spectrometer called the 'minimass' I think made by AEI.
AEI eventually became Kratos (at least the bit that made mass spectrometers did). It looks as though it is now a part of Shimadzu, but still makes some mass spectrometers (MALDI-TOF as far as I can see).

What you need is a decent rotary pump and oil-diffusion pump or a turbo-molecular pump, plus the pipework, isolation valves, Pirani gauges and ionisation gauges. You never know, you might find just what you want in a skip. The last place that I worked at scrapped a Jeol GC-MS system and a VG ZAB! I worked on one of the early ZABs at the Royal Society Research Unit at Swansea University ages ago - beautiful reverse-geometry beasties.

Oh, dear. I think I have just gone too far off-topic...sorry.

Colin.
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Old 26th May 2019, 7:11 pm   #29
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Default Re: SparkChambers

Quote:
Originally Posted by TonyDuell View Post

As for helium diffusing out, this was certainly a problem with HeNe laser tubes when I was at school. They would lose the helium and stop working.
Ah that would explain why a couple I had stopped working after a while.
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Old 26th May 2019, 7:51 pm   #30
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Default Re: SparkChambers

The HeNe laser is a very marginal device, to be honest. The single-pass gain can be as low as a percent or two. So the outcoupling has to be a good deal less than this, requiring a cavity Q of several hundred. Any slight misalignment of the mirrors, or optical absorption/scattering losses due to sputtered contamination, will snuff it out.

Cheers,

GJ
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Old 27th May 2019, 7:12 pm   #31
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Default Re: SparkChambers

Just as a side issue I seem to recall bubble chambers for seeing radiation trails in 6th form physics using solid dry ice - is this the same or some different mechanism??
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Old 27th May 2019, 7:49 pm   #32
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The solid dry ice ones would have been cloud chambers rather than bubble chambers, the latter being a superheated liquid and the former a supersaturated vapour. The passage of a high-energy subatomic particle leaves an ionisation trail behind it which then nucleates either condensation of the vapour (cloud chamber) or appearance of a trail of fine bubbles (bubble chamber). In a spark chamber the ionisation causes a gas discharge to develop. In some ways they're all similar, in others they're very different.

There were once some quite large liquid hydrogen bubble chambers at the lab where I spent most of my working life. By the time I arrived they had gone. But the huge (essentially immovable) concrete blast wall put in to direct the explosion fragments away from the staff in the event of an accident was still there !

Cheers,

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