-
Cryogenic system of the SuperKEKB final
focusing SC magnets
Zhanguo Zong, Norihito Ohuchi, Yasushi Arimoto, Xudong Wang,
Kiyosumi Tsuchiya,
Masanori Kawai, Yoshinari Kondo, Hiroshi Yamaoka, Kanae Aoki,
and Ryuichi Ueki
SC magnet Group, Accelerator Laboratory,
High Energy Accelerator Research Organization (KEK)
Email: [email protected]
The 9th Asian Forum for Accelerators
and Detectors (AFAD2018),
from January 28 to 31, 2018 in the DCC
(Daejeon Convention Center), Korea.
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2018/01/29 (Mon.) 2Zhanguo ZONG, AFAD2018, Daejeon, Korea
Contents
• The SuperKEKB/Belle II, from KEKB/Belle (1999~2010)
− The commissioning status, from Phase I to Phase II
• SC magnets and cryogenics of the SuperKEKB final focusing
system
• Performance tests of SC magnets and cryogenic systems
• Summary
− SC magnets, SC magnet cryostats, service cryostats,
refrigerator, cryogenic system
− Cool down, interlock tests, and excitation of SC magnets
− Magnetic field measurements with different techniques
− Some problems to be solved after the 2017 performance
tests
− Heat load measurements of the SC magnet cryostats
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2018/01/29 (Mon.) 3Zhanguo ZONG, AFAD2018, Daejeon, Korea
The SuperKEKB project: a electron-positron collider
The Nobel Prize in Physics 2008
Makoto Kobayashi and Toshihide Maskawa
The SuperKEKB accelerator/the Belle II detector
− The target luminosity: 8×1035 cm-2s-1, 40 times than the world
highest record at its
predecessor, KEKB, by collecting 50 times more data.
KEKB accelerator /Belle detector (1999 ~ 2010)
demonstrated the violation of CP asymmetry, a leader
in the race to provide the world's highest luminosity
• To discover new physics beyond the Standard Model
on the luminosity frontier.
− Upgrading the KEKB and the BELLE detector .10240*
1234
y
yeIscmL
− Based on the Nano-beam and higher currents: the beta function
at the IP is 1/20 (L: ×20) and beam
currents are doubled (L: ×2).
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2018/01/29 (Mon.) 4Zhanguo ZONG, AFAD2018, Daejeon, Korea
• The modified or new components
− The injector linac sources, reinforcing RF
system, new damping ring for positron, and
replacing vacuum beam pipes.
− New SC magnets for final focusing
• Beam commissioning in three phases.
− Phase I: Feb.~Jun. 2016, machine tuning
and vacuum scrubbing
− Phase II: Mar.~ Jul. 2018, beam collision
tuning with QCS and Belle II
K. AKAI, MR and DR status and
schedule, Oct. 9, 2017 @B2GM
The SuperKEKB project: a electron-positron collider
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2018/01/29 (Mon.) 5Zhanguo ZONG, AFAD2018, Daejeon, Korea
SC magnets of the SuperKEKB final focusing at the interaction
region
− 8 main quadrupoles (QC1s-vertical focusing and
QC2s-horizontal) to form the beam doublets
− 43 Correction coils (To calibrate misalignments, to cancel
leakage field, 20/23 coils for left/right)
− 4 anti-solenoids (ESL, ESR1 ESR2, and ESR3) to fully
compensate the detector solenoid field.
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2018/01/29 (Mon.) 6Zhanguo ZONG, AFAD2018, Daejeon, Korea
The SC magnet cryostats
Magnet cryostat QCSL QCSR
Total cold mass (kg) 1522 3139
Front LHe vessel 1180 2076
Rear LHe vessel 342 1063
Supply lines
LHe return lines
Front LHe vessel
• Inside the SC magnet cryostats, the two LHe
vessels are cooled in series with one LHe flow.
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2018/01/29 (Mon.) 7Zhanguo ZONG, AFAD2018, Daejeon, Korea
Cooling the SC magnet cryostats
• The SC magnets are cooled with the sub-cooled LHe at 20 g/s
and 0.16 MPa (~40 W)
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2018/01/29 (Mon.) 8Zhanguo ZONG, AFAD2018, Daejeon, Korea
The service cryostats• To host the current leads of SC magnets
(L/R: 16/17)
− Current leads for each side consumes about 30 LLHe /hour.
• To install cryogenic valves, instrument wires, and to
access cryogenic transfer lines from the sub-cooler.
The LHe vessels inside
the SC magnet cryostat
The service
cryostat
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2018/01/29 (Mon.) 9Zhanguo ZONG, AFAD2018, Daejeon, Korea
Cryogenic systems
2017-03/ before Belle-roll-in
Sub-cooler
The QCS-L
cryostat
Valve units
for current
lead flows
Cryogenic
lines
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2018/01/29 (Mon.) 10Zhanguo ZONG, AFAD2018, Daejeon, Korea
Cryogenic systems of the final focusing SC magnets
• Each cryostat has an individual coldbox, with the cooling
powers of 250 W.
− The cold boxes has served for the Tristan and KEKB project for
about 30 years.
0 10 20 30 40 50 60 700
50
100
150
200
250
Margines of cryogenic system:
~80 W or ~20 LLHe/h
貯液 : ~20 L/h
Ref
rig
erat
or
po
wer
(W
)
Liquefaction (L/hour)
The cryostat heat loads:
~70 W+CL: 30 LLHe/h
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2018/01/29 (Mon.) 11Zhanguo ZONG, AFAD2018, Daejeon, Korea
Cryogenic control system of the SuperKEKB final focusing SC
magnets
• Cryogenic systems are controlled by a process-
control computer system, comprising central
computer units and individual substations
located in the Tsukuba Exp. Hall.
SuperKEKB IR
Tsukuba Exp. hall
Central control room
for refrigerators
Nikko Exp. Hall
SuperKEKB
Accelerator central
room
− Automatically cool down, warm up, recover from
some troubles of compressors, turbins, and
quench.
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2018/01/29 (Mon.) 12Zhanguo ZONG, AFAD2018, Daejeon, Korea
Construction of QCS cryogenic systems
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2018/01/29 (Mon.) 13Zhanguo ZONG, AFAD2018, Daejeon, Korea
Construction of QCS cryogenic systems
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2018/01/29 (Mon.) 14Zhanguo ZONG, AFAD2018, Daejeon, Korea
Performance tests of the SC magnets and cryogenic system
• April 11th, 2017: Belle-II Rolled in to the SuperKEKB
interaction region
• May ~ August 2017: Performance tests of the SC magnets and
cryogenic system
− Cool down and excitation tests of the QCS-R/L systems with
exciting Belle-II solenoid at 1.5 T
− Magnetic field measurements: Single stretched wire (SSW, June
19 ~ 30), Harmonic coils (July 3
~ 29, August 17 ~ 19), Hall probe (August 21 ~ 28)
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2018/01/29 (Mon.) 15Zhanguo ZONG, AFAD2018, Daejeon, Korea
Cool down of the QCS-L system
• The first cool down from Nov. 10, 2016
− Cooled down to 4.5 K with 55 hours
• The 2nd cool down from May 16, 2017
− The cool down time from room temperature to LHe
temperatures: 44 hours. The operation parameters
were improved from the 1st cooling down.
0 10 20 30 40 50 600
60
120
180
240
300QCS-L: Nov. 10, 2016, 17:00~
RearLHe level of
Subcooler
LHe level of
the service cryostat
LH
e le
vel
(%
)Service
Cryostat
Sub-cooler
Front
Tem
per
atu
res
(K)
Liquefaction (L/hour)
0
20
40
60
80
100
0 10 20 30 400
60
120
180
240
300QCS-L: May 16, 2016, 16:00~
Rear
LHe level of
Subcooler
LHe level of
the service cryostat
LH
e le
vel
(%
)
Service
Cryostat
Sub-cooler
FrontT
emp
erat
ure
s (K
)
Liquefaction (L/hour)
0
20
40
60
80
100
0 10 20 30 40 50 60 700
50
100
150
200
250
Heat [email protected]:
~70 W (QCS-L)
Coldbox+subcooler+QCS-L
Coldbox+subcooler
Hea
ter
Po
wer
(W
)
Liquefaction (L/hour)
Heater power:
~110 W
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2018/01/29 (Mon.) 16Zhanguo ZONG, AFAD2018, Daejeon, Korea
Cool down of the QCS-R system• The first cool down from May 10
to 18, 2017
− At the 1st cooling down test, the QCS-R SC magnets did not
reach to 4.5 K. The cooling down
process was stopped to investigate the reasons, which was the
mis-connection of a flow monitor
of helium gas for turbines
− After the repairs, the QCS-R magnets was cooled down to 4.5 K
within 65 hours.
• The 2nd cool down from August 14, 2017
− The cooling-down process started from about 200 K of the QCS-R
cryostat, and it took 100
hours (4 days) to cool the SC magnets to 4.5 K.
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2018/01/29 (Mon.) 17Zhanguo ZONG, AFAD2018, Daejeon, Korea
Interlock tests of cryogenic systems
• Cryogenic systems must be operated stably for a long term as a
part of the accelerators
• To simulate some troubles in the main devices of cryogenic
system, and to check the
responses of the operation sequence programs
− Operation sequence programs are designed to realize the system
automatic processes, such as
cool down, warm up, recovery from some troubles with
compressors, turbines, and quenches
− Quenches of SC magnets − Trouble with compressors − Trouble
with turbines
• The cryogenic systems were controlled very well and responsed
rightly for protections
• The recovery times to the normal operation were investigated.
~ 35 hours were needed
20 hours 16 hours
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2018/01/29 (Mon.) 18Zhanguo ZONG, AFAD2018, Daejeon, Korea
Excitation tests of SC magnets• 54 SC magnets (QCS-L&R) were
excited to the beam operation currents.
− The SC magnets were operated under the magnetic field at 1.5 T
by the Belle-II solenoid.
− The main quadrupole magnets were excited all together.
− The excitation current of QC2RE was smaller than the beam
operation current.
• Quench recovery: ESR1, which has the largest energy in the SC
magnets
15 hours
8.75%/h
~22 L/h
19:00:00 19:20:00 19:40:001.0
1.5
2.0
2.5
3.0
3.5
4.0
Setting pressure of
the releasing valve: 3.0 bar
inlet pressure
of the QCS-R compressor
QCS-R: June 08, 2017, 17:00~
QCS-R
Cryostat
Pressure
Pre
ssure
AB
(B
ar)
− After quench, the cryogenic system responsed automatically, to
stop the LHe supplying to the
cryostat, to fully open the valves, and the safety releasing
valve opened.
• The setting pressure of 3.0 bar was too high so that the
compressor was stopped by
over pressure protection and the releasing pressure was reduced
to ~ 2.0 bar)
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2018/01/29 (Mon.) 19Zhanguo ZONG, AFAD2018, Daejeon, Korea
Magnetic field measurements and some problems to be solved
• Magnetic field measurements, with measuring techniques and
different excitation scenario
− Single stretched wire (SSW): to measure the quadrupole field
centers and the angles to beam lines
− Harmonic coils: magnetic field quality as a function of
currents with the integral coils, magnetic
field profiles along the beam lines with the 20 mm short
coils.
− Hall probe: to measure Bx, By, and Bz components along the
beam lines
• To measure the magnetic field profile with Belle II and
ES-s
• Calculation of the integral Bz component, and adjustment of
the operation
currents of the compensation solenoids.
• Problems to be improved for Phase II commissioning of the
SuperKEKB.
− Power supply noise of the compensation solenoids (ESR1 and
ESL): the voltage noise
of the power supplies below 100 A induced the false operation of
the quench detector of
the magnets, and the signals from the quench detector made the
power supply shut-off
− Quenches of the main quadrupole magnets at the connection of
the current leads
• To increase the flows for the current leads. For the Phase II,
we added sc
cables at the ends of the current leads.
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2018/01/29 (Mon.) 20Zhanguo ZONG, AFAD2018, Daejeon, Korea
Heat load measurements of the QCS cryostats
10:40 11:20 12:00 12:40 13:20 14:004.3
4.4
4.5
4.6
4.7
4.8
L: 28.1 g/s
L: 22.8 g/s
Saturated Temp.: 4.435 K @ 0.123 MPa
Saturated Temp.: 4.754 K @ 0.1613 MPa
Tem
per
atu
res
(K)
LTI615
LTI414a
LTI412a
RTI615
RTI414a
RTI412amR: 17.5 g/smR: 23.0 g/s
he cryostat (Service cryostat + SC magnet cryostat)
mSupply
Pipes
0
m1 m 2m 3Rear
Comp.
vesselFrontvessel
leadsleads
Return
Pipes
TI414a TI412a
• Heat loads of the QCS cryostats (Supply
pipes + the two LHe vessels)
• Total heat loads of QCS-L&R (+flows for current leads: 30
LLHe/h)
Items QCS-L QCS-R
Support rod 13.2 7.1
CLead pipes 19.1 14.5
Thermal radiation 8.6 12.2
TRT+Valves 22.0 22.0
Instrument wires 4.7 4.3
Total heat loads 67.5 60.1
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2018/01/29 (Mon.) 21Zhanguo ZONG, AFAD2018, Daejeon, Korea
Current status of the final focusing SC magnet system
QCS-LQCS-R
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2018/01/29 (Mon.) 22Zhanguo ZONG, AFAD2018, Daejeon, Korea
Summary
• The SuperKEKB accelerator and the Belle II detector are being
prepared for the Phase II
commissioning in this March
− The final focusing SC magnet cryostats (QCS-L/R) were moved to
the core of Belle II detector
from both sides and connected to central beam pipe inside. (Jan.
10 ~ 15, 2018)
• The final focusing SC magnets and cryogenic systems were
operated with the Belle II
solenoid from May to August 2017
− Cool down, interlock tests of cryogenic system were
performed
− All 55 SC magnets were successfully excited under the Belle II
solenoid field of 1.5 T
− Magnetic fields were measured with different techniques: SSW,
Harmonic coils, and Hall probe.
• Some works for the SC magnets and cryogenic system after the
2017 performance tests
− Exchange the field measurement pipes to the real beam pipes
and exchange the front caps of the SC
magnet cryostats, improve cold ends of current leads (Completed
by Oct.~Nov. 2017)
− Improve ESR1 and ESL current sources, to reduce the voltage
noises below 100 A.
− Cryogenic operation parameter tuning, interlocks between
current sources, accelerators.