What in the world is MKS doing here? (ion gauge that works at atmospheric)

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
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ian_krase
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What in the world is MKS doing here? (ion gauge that works at atmospheric)

Post by ian_krase » Wed Oct 25, 2017 9:49 am

Over the summer, MKS released the Series 523 Cold Cathode Ion Gauge.

This device is distinguished by two features. The first and strangest is that it is an ion gauge that not only works in the micron range, but all the way up to atmosphere. It's not an ion-pirani combo or similar, it's all discharges, although the very vague marketing-speak suggests that it contains more than one diode.

The second feature is that its feedthroughs are made only of polypropylene.


I really wonder just what is going on here. They talk some about arc discharges and the like, but I was not of the impression that arcs worked reliably as pressure gauges at atmospheric pressure. Also, customarily I had thought that polypropylene was not a vacuum qualified material -- if it was, it would be a great way to make dirt cheap DIY feedthroughs in whatever voltage you prefer. Perhaps they de-gassed it similar to how Apiezon Grease is made? (And what keeps the polypropylene from burning up in the plasma?)


Sadly, since this is a very new product there are none on ebay. I would really like to dissect a broken one.

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Richard Hull
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Re: What in the world is MKS doing here? (ion gauge that works at atmospheric)

Post by Richard Hull » Thu Oct 26, 2017 4:45 am

MKS is advertising the "nirvana gauge". With this gauge, all other gauges are obsolete. There might be a catch, but MKS is not given to hyperbole.
I wonder what this wonder sells for?

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Re: What in the world is MKS doing here? (ion gauge that works at atmospheric)

Post by Andrew Seltzman » Thu Oct 26, 2017 4:57 am

The catch is accuracy, the gauge specifies +-50% error at high pressure (>10torr). It's only using the "enhanced arc" to turn the ion gauge on/off in inverted magnetron mode. I's assume it's using some sort of current limited corona or "ion breeze" current sensing at high pressure.
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Richard Hull
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Re: What in the world is MKS doing here? (ion gauge that works at atmospheric)

Post by Richard Hull » Thu Oct 26, 2017 5:08 am

There is always that "catch 22". All the cold cathode gauges I have are non-linear based on their controller meter faces and just start to read in the single digit microns (10e-3 torr) and go down to bottom out near 10e-6 torr. Three very useful decades once your TC gauge starts running out of meter needle movement.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

ian_krase
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Re: What in the world is MKS doing here? (ion gauge that works at atmospheric)

Post by ian_krase » Thu Oct 26, 2017 7:45 am

Huh. I guess that answers it.

I still am extremely curious what's up with the vacuum qualified (including as a vacuum barrier!) polypropylene and where I can get some. And the polypropylene to metal sealing process. Are plastic Conflat gaskets going to join the rubber and copper ones?


Imagine that the Penning-Micropirani combination will be much more popular for years to come.


(Meanwhile, I have a pretty rare Convectron ATM... which leaks... and only speaks devicenet... and a bayard-alpert gauge taking advantage of the MKS 919, which routinely is sold used for under 20 dollars. Unfortunately the cable is nearly impossible to buy and expensive (and tricky) to make -- so instead I drilled a hole in the back panel and added my own connector.)

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Re: What in the world is MKS doing here? (ion gauge that works at atmospheric)

Post by Dennis P Brown » Thu Oct 26, 2017 1:15 pm

Not sure that polypropylene is very good for anything but low vacuum work (no plasticizer) but sealing to metal shouldn't be too difficult: just use a very thin layer of vacuum grade epoxy. That should bond those very different materials together, fairly well.

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Re: What in the world is MKS doing here? (ion gauge that works at atmospheric)

Post by Richard Hull » Thu Oct 26, 2017 4:06 pm

I doubt epoxy will hold to PE very well. I remember asking a plastics expert if their was a teflon cement or epoxy. He said yes., but to tell you how good it is in bonding Teflon, It comes in a glass bottle with a teflon anti leak gasket, attached to a teflon lid or cap.

A PE seal might better be served in a vacuum setting by using vacuum grease and a compression fit against it on a viton gasket.

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Re: What in the world is MKS doing here? (ion gauge that works at atmospheric)

Post by ian_krase » Thu Oct 26, 2017 7:58 pm

It's from the datasheet. The only material in vacuum is metal and PP.

I understand that gluing Teflon or polyolefins is a question of surface prep with either aggressive chemical or plasma.

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