Superconducting IR Magnets

CHEN, Fusan

May 11, 2007

2/18

Outline• Progress of the superconducting magnets and relevant

systems.– Power supplies and QPS were testified to be workable.– Electronic test was done to the system.– The magnets were cooled down to superconducting temperature.– The whole system was assembled together.

• The first commissioning of the magnets.– All coils were powered to 10~20% operating current.– Quench protection system was proved to be reliable.– Many problems were revealed with the valve boxes.

• Schedule of the second commissioning and field measurement.– The valve boxes are rebuilt and the whole system is reassembled.– The second commissioning is in process.– Magnetic field measurement will be started after commissioning.

3/18

Progress of the PS and QPS• Power supplies met the requirements.

– After months of tuning work, all power supplies were workable.

• Power supply control system fulfilled the required functions.

• Quench protection assembly reacted fast and correctly.– Reaction of the system was tested with dummy load.

• Quench detection system was assembled.– Both hardware and software were ready.

4/18

Progress of the SC magnets

• Electronic test before cooling.– The environment was not ideal.

• Temperature: 25~28ºC Humidity: 95%~100%

– Problems of the valve box.• The insulator failed in the hipot test at ~220VDC wh

en the humidity was higher than 95%.• The temperature sensors were electrically connecte

d to the current leads.• The hipot performance was concerned with the vac

uum of the valve box.

5/18

Progress of the SC magnets

• Monitoring the magnets during cooling.– To monitor the transformation from normal to

superconducting of the coils, we powered the coils with low current (40mA) and monitored the voltage drops across the coils.

6/18

Progress of the SC magnets

• Electronic test after cool-down.– Measured the resistance of gas cooled leads.

– Hipot tests were repeated with all coils.• The grounding resistances of all coils were far less t

han requirement (20Mohm).

7/18

The first commissioning• More study on the hipot problem with BNL expert

s, George Ganetis and Wing Louie.– The grounding resistance of coils ranges from 2 to 800

0 ohms. The resistance decreases when the valve box gets cold.

– The resistance is non-linear and does not start to have current flowing until the voltage is greater then 1 Volt.

– In all circuits the short is at or near the gas cooled lead. But the exact location of the short can not be found.

• Possible causes of hipot failure.– All the electrical insulators used in the current leads ha

ve a creep path that is too small.– The G-10 insulators used on the top of the valve boxes

can collect water.

8/18

Result of grounding resistance testValve Box

Circuit AC Ground

Resistance

DC Ground

Resistance

Shorts

Locations

Current

Tested

Comments

SCQ-A

AS 50 335 AS1-IN,

AS2- 3

AS1-OUT

300 Pre-cooled Leads, Bus Quench

High Ground Current

SCQ 130 363 SCQ-IN

SCQ-OUT250 Pre-cooled Leads, Bus Quench

SCB 563 633 SCB-IN

SCB-OUT10 Low Current Shut-off

SKQ 301 514 SKQ-OUT 6.6 Low Current Shut-off

VDC 244 490 VDC-IN

VDC-OUT5.1 Low Current Shut-off

SCQ-B

AS 126 NA AS1-IN,

AS1- 2

AS1-OUT

250 SC bus went resistive

SCQ 1800 8000 SCQ-IN

SCQ-OUT150 SC bus went resistive

SCB 533 625 SCB-IN 40 High Current Shut-off

SKQ 537 NA NA 40 High Current Shut-off

VDC 710 NA NA 40 High Current Shut-off

* This table quotes from George’s report

9/18

The first commissioning

• New problems of valve boxes– The current leads could not be cooled down.

• The cold ends reached 20K with the flux controllers at max.

• Reached 6K with the bypass valves at max.• AS, SCQ and SCB coils could not be powered more

than 20% operating current, otherwise quenched.

– The sensors could not indicate the temperature of the most critical points.

– The inlet and outlet leads could not be cooled equally because they used common controller

10/18

The first commissioning

• Some typical data and the diagnosis

Vc

Vt

Vs

Warmend

Coolend

Gas CooledLead

Endcan ofthe Magnet

Superconductingbus

Outside Valve Box Area Transfer Line Area Magnet AreaHeliumTankArea

Quenchorigin

The signals monitored during the commissioning

11/18

Data of SCQ

Inlet Vt

146A

162A

58A

Outlet 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

12/18

Data of 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

13/18

146A

165A175A

185A195A

205A

The normal regions do not expand under 200A

The normal regions expand rapidly after 200A and the quench protection system is triggered.

Inlet VtOutlet Vt

Learn more from SCQ

14/18

The second commissioning• The valve boxes are rebuilt and installed.• The quench detection circuit is set up and tested.• The warm temperature electronic test is performe

d.– The insulation of some temperature sensors on the cur

rent leads is not satisfying.

• The power supplies are improved.• The ps control system is updated.• The interlock between systems is linked.• The cryogenic pipes are connected.Now, the temperature reaches 60K.

15/18

The second commissioning• Next steps: (schedule is tight.)

– Restore the quench protection software. (1 day)– Power the coils to 10~20% current. (5~6 days)

• Tuning the parameters of quench detection system.• Check the ps and ps control system.• Check the quench protection assembly.• Configure the parameters of leads flux controller.

– Power the coils to 50% current. (2 days)– Power the coils to 110% current. (2 days)

• Tuning the power supplies.• Quench training if necessary.

– The same powering procedure for the sync-rad mode. (4 days)

16/18

Schedule of field measurement

• Joint field measurement. (37 days)– Instruments alignment, assembly, de-assembly,

replacement (5 days).– Longitudinal field measurement with

salamander.• Solenoid magnet off (1 day) & on (3 days).

– Excitation curve measurement with stretch-line.• Solenoid magnet off (7 days) & on (7 days).

– Rotating coil measurement (long & short coil).• Solenoid magnet off (4 days) & on (10 days).

17/18

Schedule of field measurement

• Individual field measurement. (33 days)– Instruments alignment, assembly, de-

assembly, replacement (5 days).– Excitation curve measurement with stretch-line

(8 days for one magnet, totally 16 days).– Rotating coil measurement (12 days).

• Long coil and short coil are used at the same time with different magnet.

– Longitudinal field measurement with salamander (2 days).

18/18

Additional topic

• The force and torque of SC magnet coils.

• The special type magnets in IR work well.– Septum bending magnet: ISPB.– Dual aperture quadrupole: Q1a, Q1b.– Narrow quadrupole: Q2, Q3.

Fx [kN] Fy [kN] Fz [kN] Mx [kN·m] My [kN·m]

AS 10.5

HDC(Iop=50A)

±3.9z=770mm

z=1170mm1.48

VDC(Iop=24A)

±3.9z=1020mmz=1400mm

1.49