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Quench Protection and the Power Supplies for the MICE Focusing and Coupling Magnets. Michael A Green Lawrence Berkley Laboratory 10 February 2005. Focusing and Coupling Magnet Quench Protection.
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Quench Protection and the Power Supplies for the MICEFocusing and Coupling Magnets Michael A Green Lawrence Berkley Laboratory 10 February 2005
Focusing and Coupling Magnet Quench Protection • The focusing and coupling magnets have a shorted secondary (the mandrel) to induce quench back in the coil for passive quench protection. • Quench back will quench all magnets when more than one magnet is hooked up in series. • Resistors and diodes across the coil will provide additional quench protection by shunting some current from the coil. • The resistors and diodes limit the voltage within the coils during a magnet Quench.
Unprotected Quenches of a Single Focusing Magnet and Three Focusing Magnets in the Flip Mode L1 = 98.6 H E1 = 3.10 MJ L3 = 295.2 H E3 = 9.30 MJ
Unprotected Quenches of a Single Focus Magnet in the Flip Mode and the Non-flip Mode Lflip = 98.6 H Eflip= 3.10 MJ Lnon-flip = 134.8 H Enon-flip = 4.65 MJ The non-flip current is the worst case.
An Unprotected Quenches of a Single Coupling Magnet L1 = 563 H E = 12.8 MJ
Should the coupling coils be in series? • One can argue this question either way, but the argument favor powering the coils separately. • The inductance of a single coil is 563 H. It will take 3.4 hours to charge one coil at 10 V. The inductance of all other magnet circuits is less than the inductance of a single coupling coil. • A single coupling coil produces force that are smaller than the maximum force with the coils hooked in series. • A quench of the coupling magnet will probably quench the focusing magnets.
The MICE Coupling Coil Power Supplywith Quench Protection Note: The coil is shown split into two parts. The coil may be split into three or four parts instead of two parts.
Detector Magnet Quenches • The INFN magnet design is different from the focusing and coupling magnet design from a quench standpoint. Active quench protection is proposed. Quench back is not a factor in the quench. • The current densities are lower so quenches are safe even without quench back from a mandrel. • The detector should have separate 300 A leads on the match coils. The other three coils are in series with added 50 A power supplies across the end coils. • Like detector coils can be put in series. The circuit inductances are less than 200 H.
Detector Magnet Power Supplies Match 1 Match 2 End 1 Center End 2
Concluding Comments on Quenches • The focusing and coupling magnets will have passive quench protection. The detector magnet will likely have an active quench protection system. • The three focusing magnets should be in series. • Each coupling magnet should have its own power supply to reduce the charge time. • Like detector magnet coils can be put in series. • A coupling coil quench will quench the rest of MICE. A focus coil quench will not quench a coupling coil.