Superconducting quadrupole magnets system in the interacti

on region of BEPCII

CHEN, FusanFeb. 6, 2007

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OutlineThe interaction region (IR) and the

Superconducting (SC) Magnets.– Introduction of the IR and the SC magnets.– Winding of the SC magnets.

The quench protection system (QPS).– Quench detection system (QD).– Quench protection assembly (QPA) and the power

supplies (PS) for the SC magnets.The commissioning of the SC magnets.

– Problems revealed in the commissioning.

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Interaction region of BEPCII

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The SC magnets for BEPCIICoil structure

– 3 anti-solenoid.– Main quadrupole.– Main dipole.– Vertical dipole corrector.– Skew quadrupole.

Powering configuration– Anti-solenoids are

powered in series with one main PS.

– Two trimming PS are used for current tuning.

± 65A

1300A

± 65A

AS1 AS3AS2

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Winding of the magnetsMade by BNL/SMD

– Direct wind technology.• Wind the cable directly onto

the support tube.

– Serpentine style winding.• Double layers make complete

poles.

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Quench detection systemQuench detection system (BNL)

– DSP based digital quench detection system.– Easy to configure, diagnostic and query.

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Quench protection assemblyQuench protection actions fulfilled by three

sub-systems.– Quench protection assembly interface chassis.

• QPAIC sends out commands to other systems according to the quench protection logic resided in the PLC of QPAIC.

• QPAIC can switch the operating mode for synchrotron radiation mode and collider mode.

– Quench protection assembly and the power supply.• QPA is integrated into power supply.• QPA cuts off the powering circuit and switches the energy extrac

tion resistor into the dump circuit.

– Power supply control system.• Control system ramps down the power supplies without triggerin

g the magnets quench at the case of common faults.

8/14Quench protection assembly interface chassis

Pictures of QPA

Front panel of power supplies for SCB(HDC)Back view of power supplies for SCB(HDC)

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Test of QPAAct as predetermined logic

Fast response– Quench

• 0.7ms

– Fault• 5ms

– Coherence• 7us

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Commissioning of SCMaximum test current.

– Anti-solenoid: 300A / 1300A– Main quadrupole: 205A / 580A– Corrector coils: ±40A / ±65A

Quench protection system is proved to be reliable. (React fast and correctly)

Problems are revealed with the valve box.– Coils are grounded with resistance 2~8000 ohms.– Gas cooled lead cannot be cooled down.– Main coils quench when currents go beyond 20% operat

ing current.– Temperature imbalance between inlet and outlet leads

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Commissioning of SCVoltage monitoring during commissioning.

– The voltage drops across the gas cooled lead (Vc) and across the superconducting bus inside the transfer line (Vs) are monitored independently.

Vc

Vt

Vs

Warmend

Coolend

Gas CooledLead

Endcan ofthe Magnet

Superconductingbus

Outside Valve Box Area Transfer Line Area Magnet AreaHeliumTankArea

Quenchorigin

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Commissioning of SC/SCQ

Inlet Vt

146A

162A

58AOutlet Vt

Inlet Vs Outlet Vs

The SC bus quenches, but the normal region does not expand

The SC bus cannot recover after opening the bypass valve

The SC bus recoveres after decreasing the current with the bypass valve opened

Keeping the bypass valve open, start the second ramping cycle

The SC bus does not quench at 162A

Vt almost equals to Vc and Vs equals to zero for both inlet and outlet

With the flow controller max, start the first ramping cycle

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Commissioning of SC/AS297A

9A

49A

98A

148A

197A

245A

Inlet VtOutlet Vt

Inlet VsOutlet Vs

The Vt difference between the inlet and outlet shows the imbalance of the helium flow

The inlet SC bus quench causes the jump of voltage signals while current increases to ~260A

The normal region does not expand at 297A

It is important to analyze why the outlet does not quench even the Vt higher

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ConclusionMost of the system work well.

– The performance of the superconducting magnets is good during the vertical test completed in BNL.

– The quench protection system can protect the magnets from any quench or faults.

– The power supplies and the control system are workable although some small bugs still exist.

We do meet problems.– Most of the problems occur on the valve box.

Improvement is underway.– The valve box is redesigned and under machining.