Why is energy ramp-up/ramp-down so slow?

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jolder
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Why is energy ramp-up/ramp-down so slow?

Post by jolder » Sun Apr 04, 2010 1:39 am

Looking at the live energy graph (http://op-webtools.web.cern.ch/op-webto ... p?usr=LHC3), I am surprised to see that it takes a lot of time to ramp up particle energy. I'm even more surprised that ramp-down takes just as long.

You'd think just removing power would grind all activity to a halt.

I'm guessing there are some powerful magnetic fields that have to be built over time.
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Tau
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Re: Why is energy ramp-up/ramp-down so slow?

Post by Tau » Sun Apr 04, 2010 6:23 am

This is basic physics. The magnets are inductors. The main property of an inductor is that if you apply a voltage to them the current goes up or down. The higher the voltage, the fast the current goes up; the bigger the inductor, the slower.
The arc magnets are very large inductors, and you cannot apply too much voltage to them, because they'll quench otherwise. So, the process necessarily takes a long time.
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Danny252
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Re: Why is energy ramp-up/ramp-down so slow?

Post by Danny252 » Sun Apr 04, 2010 1:30 pm

Is there also an element of limits of the local power grid - in that it can only supply/dissapate power at a certain rate?

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Re: Why is energy ramp-up/ramp-down so slow?

Post by Harbles » Sun Apr 04, 2010 10:01 pm

I think it's a limitation of the magnets and power converters. Here is a paper on LHC ramp. http://epaper.kek.jp/p99/PAPERS/MOP45.PDF

They conclude ;
" An optimised shape for the LHC acceleration ramp has
been developed, based on the constraints of field
quality, time minimisation and practical power
converter limits as well as on-line feedback
considerations. This complex curve has been
implemented in a prototype power converter system"

jolder
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Re: Why is energy ramp-up/ramp-down so slow?

Post by jolder » Mon Apr 05, 2010 2:43 am

Tau wrote:The arc magnets are very large inductors, and you cannot apply too much voltage to them, because they'll quench otherwise.
I figured it was something like that. I was unaware of the annoying quench feature of superconductors.

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Xymox
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Re: Why is energy ramp-up/ramp-down so slow?

Post by Xymox » Mon Apr 05, 2010 7:50 am

annoying quench feature
Hehehehe... It sure is that !

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