What is Quench Management for Magnetism?

In summary, Quench Management is a safety measure used in high-field magnets made from superconductors. It involves overpressure valves and shorting rods to prevent dangerous situations in case of a quench, where the superconductor exceeds its critical current and becomes a normal metal. This is important for preventing explosions and ensuring the safe operation of these magnets.
  • #1
neorich
20
1
Hi,

Can someone please explain what Quench Management is particularly when applied to magnetism.

Thanks

Regards

neorich
 
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  • #2
I guess you are asking about high-field magnets (a few T)?
In this case is probably refers to safety valves etc.

Most high field magnets are made from a superconductor (usually NbTi) that can carry very large currents. However, superconducting wires can only carry a certain amount of current (known as the critical current), if you exceed this limit the wire goes normal (i.e. becomes a normal metal); this is known as a "quench".
This can also happen if the superconductor warms up since the critical current decreases as you approach the critical temperature of the superconductor (and Jc goes to zero at Tc, obviously).

Most superconducting magnets are cooled using liquid helium. Now, the problem is of course that if you quench the magnet you suddenly have a LOT of current going through what is suddenly just a thin metal wire, i.e. the resistance is quite high ->It gets very hot very quickly which in turn heats the helium which vaporizes; 1l of liquid helium becomes about 700l of gas at 1 Bar meaning you suddenly have a LOT of gas that needs to go somewhere.
This is what happened at LHC recently .

Hence, overpressure valves are absolutely necessary on superconducting magnets. In addition to this there are usually copper or brass rods that "shorts" the magnet and can carry the current for a while if there is a quench; this way the magnet is de-energzied in a relatively safe manner.

All large magnets are quench tested when they are installed; an "uncontrolled" quench would be very dangerous and could result in an explosion.
 
  • #3
Thanks for your reply f95toli, very helpful.

Regards

neorich
 

1. What is quench management for magnetism?

Quench management for magnetism is a process used in particle accelerators and other high-energy physics experiments to safely and efficiently dissipate the energy of a sudden loss of superconductivity in a magnet. This loss of superconductivity, known as a quench, can have destructive effects if not properly managed.

2. How does quench management work?

Quench management involves quickly detecting a quench event and initiating a controlled discharge of the stored energy in the magnet. This is typically done by activating a dump resistor, which creates a path for the current to flow and dissipate the energy in the form of heat. In some cases, an emergency quench system may also be used to rapidly cool the magnet to prevent damage.

3. Why is quench management important?

Quench management is important because it helps prevent damage to expensive and delicate equipment, such as superconducting magnets, in high-energy physics experiments. It also ensures the safety of the researchers and technicians working with these magnets, as a quench event can release a large amount of energy and potentially cause harm.

4. What are some techniques used in quench management?

There are several techniques used in quench management, including the use of dump resistors, quench heaters, and quench detection systems. These systems work together to quickly detect and dissipate the energy of a quench event, minimizing any potential damage to the equipment.

5. How is quench management for magnetism different from quench management in other fields?

Quench management in high-energy physics experiments is unique in that the magnets used are often large and powerful, and require specialized techniques for safe and efficient operation. In other fields, such as electrical engineering, quench management may refer to techniques for preventing overheating in electrical circuits, but the principles are similar in that the goal is to safely dissipate energy to prevent damage.

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