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Old Yesterday, 08:44 PM   #1
Pano is offline Pano  United States
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Default Ground Problems. It's always ground problems.

Even in the billion dollar systems, they have ground problems.
Short Circuit Delays Restart of the Large Hadron Collider - Scientific American
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Old Today, 04:30 PM   #2
davym is offline davym  Europe
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These novices need to catch up with the world of quantum hifi physics

A ground lift switch and a cryo treated mains cable would have them up and running in no time
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Old Today, 04:39 PM   #3
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Originally Posted by Pano View Post
Even in the billion dollar systems, they have ground problems.
Short Circuit Delays Restart of the Large Hadron Collider - Scientific American
Ya gotta love it.

When they say diode box, what they really mean is DIODE box.

The diode is a 100 mm diameter piece of silicon, designed to bypass the magnet in the event the magnet quenches. It operates normally at the 1.9 Kelvin temperature, and acts like an SCR.

The forward voltage of the diode essentially goes away, and instead, the device can sustain somewhere between 3 and 30 volts in the forward direction without conducting forward current.

When a magnet quenches, it's IR drop goes way up, and the diode clamps the voltage first at whatever the diffusion parameters were set for, and then the diode instantly heats up, and reverts back to a forward bias junction device. It conducts the current of the rest of the sector around the heating magnet, and they very quickly turn off the power supply. And when I say instantly, I mean instantly..13 kiloamps and 30 volts ain't no biggie in itself, but at 1.9 K there really is no heat capacity in the silicon nor in the copper anvils they are compressed between.

Unfortunately, that switching operation only occurs at liquid helium temperatures, so they have to enclose it deep in the cryostat, with everything welded for high pressure resistance.

QA for these big objects is a PITA, as it can take days (or weeks) to bring the system back up to room temperature..as I recall, it took weeks to bring the tunnel up to room temperature after the accident..

jn
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Old Today, 04:39 PM   #4
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These novices need to catch up with the world of quantum hifi physics

A ground lift switch and a cryo treated mains cable would have them up and running in no time
I got news for ya.

The mains cables are cryo treated..

jn
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Old Today, 04:44 PM   #5
davym is offline davym  Europe
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Progress! shame they haven't found out about the benefits of 'tuning' fuses yet though eh
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Old Today, 04:44 PM   #6
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bummer if they have to warm it up to let a meatbag in to inspect.

I have to admit the whole concept of cooling the whole ring to 1.9K is mind boggling.
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Old Today, 04:51 PM   #7
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bummer if they have to warm it up to let a meatbag in to inspect.
They are CERN. They have ways.

When they did the splice work, the first thing they did was come up with a way to X-ray every solder splice. sheesh.. Now, they are going to use that to view the diode box. The only thing they have to worry about is oxygen deficiency hazard in the tunnel while the magnets are cold. The tunnel looks pretty much like the one in terminator 3, but less of a curve...and no chick robots.

In ODH training here, they have one very important rule. If you hear the whoosh of a big liquid helium or liquid nitrogen leak, RUN the other way.

Run. Do not walk. This IS a race. The loser....well, loses..
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I have to admit the whole concept of cooling the whole ring to 1.9K is mind boggling.
Yes. Most people do not know what it takes, nor how weird or dangerous it can be. They do have the 8 biggest refrigerators on the planet though.

jn
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Old Today, 05:02 PM   #8
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Well I can very safely say Superfluid helium freaks me out.
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Old Today, 05:30 PM   #9
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Progress! shame they haven't found out about the benefits of 'tuning' fuses yet though eh
Yah. Their idea of a fuse turned out to be a 50 foot long, 45 ton iron based object which played leapfrog in the tunnel during the "accident".

But at least they only use lead free solder..

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Old Today, 09:48 PM   #10
Pano is offline Pano  United States
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Really? Lead free? Hmmm...

Cryo treatment all around, that's - uh - cool. Wonder what the thing sounds like?
Thanks for the info on the diode box.
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