At frequencies I use, no. But I
I will do 20 hz to one Meg max.
Much of the problem is where on the source spool the copper is. Wrapping on a mandrel at constant tension means that inner position wire has been work hardened a bit more tha wire on the OD of the spool.
Beyond that, all we can think is just random wire spacing and not so well controlled wire packing.
Jn
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Since the beam is speed of light, a machine 1.86 miles circumference (I like simple math) will have the beam "packets" go through 100,000 times per second. As a magnet quenches, nothing happens to the field until the protection diode kicks in and diverts current. The quench protection system will see the rise in magnet voltage first, and can start the beam dump process before the mag field changes. (If the system does not see the quench, when the field drops, the beam will drift outwards until it scrapes the beam pipe.)
That is the theory.. Most of the time, it works. On occasion, a misfire of a beam kicker (fast diverter) will send the beam careening into the beam pipe wall in a random location (4 work in concert, one by itself is not good).
That is why I'm looking for diodes...they do not react well to being hit by the beam. And glancing blows turn out to be the worst, as they cause gradient damage. Think of four bipolars in parallel where one does not have an emitter resistor, it goes first.
Jn
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At CERN they had a magnet trouble.
20 septembre 2008.
From a connection that overheated under the very large current.
That cost a 2 months delay mostly because the time it takes to bring all back at room temperature to repair, then cooling again at near 0 Kelvin.
Now LHC is at it's maximum power. For more, we will need a bigger machine.
20 septembre 2008.
From a connection that overheated under the very large current.
That cost a 2 months delay mostly because the time it takes to bring all back at room temperature to repair, then cooling again at near 0 Kelvin.
Now LHC is at it's maximum power. For more, we will need a bigger machine.
I love the press releases.
They used tin/silver solder to solder buss bars filled with tin/silver.
Nobody there knew how to step solder, nobody understood what would would happen if they starved the joint of solder with plenty of flux, what steps, processes, and QA was needed to make sure the solder joints between magnets were good.
It was abysmal. I spent a week explaining to them what they did wrong.
It wasn't two months, it was two years. They had to repair 11 thousand solder joints.
Edit: they replaced a huge number of magnets, limped along at lower power, then shut down to fix everything.
Jn
Yeah Large Hadron Collider - Wikipedia took out rather a lot of stuff. And I'm sure superfluid helium climbing the walls causes its own issues.
@JN: was the resoldering of everything done then or after the 2013 shutdown
@JN: was the resoldering of everything done then or after the 2013 shutdown
I think the full redo was 2013 to reach full energy. I'd have to check my trip report date to be sure.. Long time ago.
The accident vaporized 2000 gallons of superfluid. I think the expansion ratio is 700 to 1. Magnets played leapfrog in the tunnel, they weigh 40,000 lbs plus.
Jn
Above my pay grade. However, it is certainly getting more expensive from what I see in the meetings.
There is a big push to go pulse cryocooler for many things cold. Also the push for high temp supers working liquid nitrogen.
One big problem at liquid helium temps is that all normal matter has almost no heat capacity at 4.5 Kelvin. If a wire moves in the least, the temp rise kills the super if helium is not present to absorb the energy.
High temp supers over 50 Kelvin don't have that problem.
Jn
There is a big push to go pulse cryocooler for many things cold. Also the push for high temp supers working liquid nitrogen.
One big problem at liquid helium temps is that all normal matter has almost no heat capacity at 4.5 Kelvin. If a wire moves in the least, the temp rise kills the super if helium is not present to absorb the energy.
High temp supers over 50 Kelvin don't have that problem.
Jn
JN --- what is the beam current level -- KAmp ? Because a beam hitting the tube side wall usually destroys it by burning thru it rather quickly with machines I was on where a lot of this early research was done. Like beam source development, linear accelerator, wiggler etc.
Speaking of coil winding ---- LLNL super conducting magnetic field cooled to near zero as possible... did you ever see the 2ea 300 tonne ying-yang super conducting magnets ? Impressive in its huge size and all kept at LH cryo temp. system. My job was all power used on system to power the super conducting magnets and control systems. Not the physics.
Those big machines are a lot of fun to work on as a project.
-RNM
Speaking of coil winding ---- LLNL super conducting magnetic field cooled to near zero as possible... did you ever see the 2ea 300 tonne ying-yang super conducting magnets ? Impressive in its huge size and all kept at LH cryo temp. system. My job was all power used on system to power the super conducting magnets and control systems. Not the physics.
Those big machines are a lot of fun to work on as a project.
-RNM
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I read this and was reminded of the last scene from 'the towering inferno'
I suspect the control room footage would have been quite entertaining.
RN...beam current is maybe 1 amp, so no holes just spray.
Since it's ions, lots of speed of light neutrons are also involved unless they're running polarized protons. As I recall, the LHC has enough energy to slice open the beam pipe a significant length.
Bill, they didn't have tunnel cameras, but the control screens depicted dipoles, they were turning red right down the line.
Jn
Since it's ions, lots of speed of light neutrons are also involved unless they're running polarized protons. As I recall, the LHC has enough energy to slice open the beam pipe a significant length.
Bill, they didn't have tunnel cameras, but the control screens depicted dipoles, they were turning red right down the line.
Jn
On a slightly different note..
Just saw a presentation where a vendor has to assemble the magnet arrays in a room at 20 C below zero. Seems there is a trade off between magnetization parameters where the magnets will lose strength if separated at room temp. A trade off between remanence and coercivity.
I recall reading that back in the 80's with stepper motors. I also recall speaker lab in their brochure mentioning Ragnar, their machine for magnetizing woofers fully assembled. I had thought their sequence was to avoid working with the live magnets.
Now I'm wondering if I toasted the magnet on the 8 incher by removing the front plate.
Next time, I will measure gap field right after I remove the next cone/voice coil.
Jn
Bill... Boss walks in, says "Ok, what did you touch?? That's coming out of your paycheck!"
Just saw a presentation where a vendor has to assemble the magnet arrays in a room at 20 C below zero. Seems there is a trade off between magnetization parameters where the magnets will lose strength if separated at room temp. A trade off between remanence and coercivity.
I recall reading that back in the 80's with stepper motors. I also recall speaker lab in their brochure mentioning Ragnar, their machine for magnetizing woofers fully assembled. I had thought their sequence was to avoid working with the live magnets.
Now I'm wondering if I toasted the magnet on the 8 incher by removing the front plate.
Next time, I will measure gap field right after I remove the next cone/voice coil.
Jn
Bill... Boss walks in, says "Ok, what did you touch?? That's coming out of your paycheck!"
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At -20 °C the required magnetization field is lower due to reduced coercivity for ferrite magnets. When brought back at room temp, Hcl increases again. It is slightly irreversible at temp lower than -40 to -60 Celsius http://spontaneousmaterials.com/Papers/TN_0302.pdf
You were right. The reason is, it is much easier and safer to handle and manufacture speaker drivers with ferrites in unmagnetized condition and then magnetize the whole assembly as an assembled unit.
No, you haven’t toasted the ferrite magnet by removing the front plate (only keep it magnetically shorted while in storage).
The front plate is made of soft steel. It will be saturated again when placed over the ferrite magnet when you’ll reassemble it.
As Ed said, alnico magnets are more easily self demagnetized.
RF bursts in the air when the capacitor banks discharge?
George
Thanks. The wiki quote I showed was a little confusing. I thought that it meant the vacuum permeability was different at different loacations, times ie not a constant. Not that it is derived from alpha which is determined experimentally and will get more acurrate, thus not constant. Please corect me if im wrong.
With the new SI, mu0 is directly proportional to alpha, with the constant of proportionality equal to 2h/ce^2
where h, c, and e are (now) exact, fixed, fundamental constants. Since alpha is determined experimentally,
therefore so is mu0, with the experimental error % the same for both.
In other words we now have mu0 = K x alpha, where K is a physical constant, and alpha is measured.
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