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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.

Cryogenic system of the SuperKEKB final focusing SC magnets · Cryogenic system of the SuperKEKB final focusing SC magnets Zhanguo Zong, Norihito Ohuchi, Yasushi Arimoto, Xudong Wang,

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  • 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.

  • 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

  • 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).

  • 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

  • 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.

  • 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.

  • 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)

  • 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

  • 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

  • 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

  • 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.

  • 2018/01/29 (Mon.) 12Zhanguo ZONG, AFAD2018, Daejeon, Korea

    Construction of QCS cryogenic systems

  • 2018/01/29 (Mon.) 13Zhanguo ZONG, AFAD2018, Daejeon, Korea

    Construction of QCS cryogenic systems

  • 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)

  • 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

  • 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.

  • 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

  • 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)

  • 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.

  • 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

  • 2018/01/29 (Mon.) 21Zhanguo ZONG, AFAD2018, Daejeon, Korea

    Current status of the final focusing SC magnet system

    QCS-LQCS-R

  • 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.