Transcript Superconducting IR magnets (F.S.Chen)

Superconducting IR Magnets
CHEN, Fusan
May 11, 2007
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.
2/18
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.
3/18
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
when the humidity was higher than 95%.
• The temperature sensors were electrically
connected to the current leads.
• The hipot performance was concerned with the
vacuum of the valve box.
4/18
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.
5/18
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
than requirement (20Mohm).
6/18
The first commissioning
• More study on the hipot problem with BNL
experts, George Ganetis and Wing Louie.
– The grounding resistance of coils ranges from 2 to
8000 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
have a creep path that is too small.
– The G-10 insulators used on the top of the valve boxes
can collect water.
7/18
Result of grounding resistance test
Valve
Box
Circuit
SCQA
SCQB
AC Ground
Resistance
DC Ground
Resistance
AS
50
335
SCQ
130
363
SCB
563
633
SKQ
301
514
VDC
244
490
AS
126
NA
SCQ
1800
8000
SCB
533
625
SKQ
537
VDC
710
Shorts
Locations
Current
Tested
Comments
AS1-IN,
AS2- 3
AS1-OUT
SCQ-IN
SCQ-OUT
SCB-IN
SCB-OUT
SKQ-OUT
300
Pre-cooled Leads, Bus Quench
High Ground Current
250
Pre-cooled Leads, Bus Quench
10
Low Current Shut-off
6.6
Low Current Shut-off
VDC-IN
VDC-OUT
AS1-IN,
AS1- 2
AS1-OUT
SCQ-IN
SCQ-OUT
5.1
Low Current Shut-off
250
SC bus went resistive
150
SC bus went resistive
SCB-IN
40
High Current Shut-off
NA
NA
40
High Current Shut-off
NA
NA
40
High Current Shut-off
* This table quotes from George’s report
8/18
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
9/18
The first commissioning
• Some typical data and the diagnosis
Outside
Warm
end
Valve Box Area
Gas Cooled
Lead
Quench
origin
Helium
Tank
Area
Cool
end
Vc
Transfer Line Area
Magnet Area
Superconducting
bus
Endcan of
the Magnet
Vs
Vt
The signals monitored during the commissioning
10/18
Data of SCQ
162A
146A
With the flow controller
max, start the first
ramping cycle
Keeping the bypass
valve open, start the
second ramping cycle
The SC bus quenches,
but the normal region
does not expand
Inlet Vt Outlet Vt
The SC bus cannot 58A
recover after opening
the bypass valve
The SC bus does not
quench at 162A
Vt almost equals to Vc
and Vs equals to zero
for both inlet and outlet
Inlet Vs Outlet Vs
The SC bus recoveres
after decreasing the
current with the bypass
valve opened
11/18
Data of AS
297A
245A
197A
148A
98A
49A
The inlet SC bus quench causes
the jump of voltage signals while
current increases to ~260A
The Vt difference between the
inlet and outlet shows the
imbalance of the helium flow
Outlet Vt
Inlet Vt
The normal region does
not expand at 297A
It is important to
analyze why the
outlet does not
quench even the
Vt higher
9A
Inlet Vs
Outlet Vs
12/18
Learn more from SCQ
175A
165A
185A
195A
205A
146A
The normal regions expand
The normal regions do not rapidly after 200A and the
expand under 200A
quench protection system is
triggered.
Inlet Vt
Outlet Vt
13/18
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
performed.
– The insulation of some temperature sensors on the
current 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.
14/18
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)
15/18
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).
16/18
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).
17/18
Additional topic
• The force and torque of SC magnet coils.
Fx [kN]
Fy [kN]
AS
Mx [kN·m]
My [kN·m]
10.5
±3.9
z=770mm
z=1170mm
HDC
(Iop=50A)
VDC
(Iop=24A)
Fz [kN]
1.48
±3.9
z=1020mm
z=1400mm
1.49
• The special type magnets in IR work well.
– Septum bending magnet: ISPB.
– Dual aperture quadrupole: Q1a, Q1b.
– Narrow quadrupole: Q2, Q3.
18/18