QCS quench protection plan
Contents

QCS cryostats and magnets
Quench result of phase-2
Quench protection and monitoring systems
Other protection plans
Collimator installation plan
Belle diamond abort system
Additional tungsten shield
B2GM@KEK, 4 Feb. 2019 Summary
Xudong Wang
KEKB QCS Group
B2GM

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QCS cryostats (QCS-L and QCS-R)

QCS-R

IP

QCS-L

QCS-R
QCS-L

KEKB review

2QCS magnets (54 magnets in total)e- beam line : 4 quadrupole magnets, 17 corrector coils, and 8 cancel coilse+ beam line : 4 quadrupole magnets and 18 corrector coils
4 compensation solenoids are located on the outer surface of quadrupole magnets
to cancel the influence of the Belle-II solenoid field on the collision beam.

Positron beam（e+）

Electron beam
（e-）

ESR1

ESL

ESR2

ESR3
KEKB review

3Quench result of phase-2
25 quenches occurred around the QC1 magnets (near to the IP).
Storage beam
Injection beam

HERLER Beam injection was not stable and the collimator was not closed in April.
 Frequency of quench dropped by closing the collimator at the end of April.
 No quench occurred from May 25 to June 25!
 Two collimators, D2V1 (LER) and D1V1 (HER), were damaged in June 25 and July 9.
 After the collimator was damaged, beam operation began to become unstable andthe quench began to occur again.
KEKB review

4Quench protection system
54 QCS magnets
Main detector
Quench detector 1Quenchtrigger

Subsidiary detector
Quench detector 2Power supplies in D2 building

Magnet temperature
Current lead temperature

QCS-R
Current lead

QCS-L

Pressure of LHe cooling line
Flow rate of current leadQuench protection system B2GMCurrent lead5

Quench detector 1 and 2
Quench detector 1

Quench detector 2

Using the balance voltage
Using the end-to-end coil voltage= V1 - V2= V1 + V2
 Sensitive to the resistive voltage
 Detectable even when V1 = V2
Independent from the inductive voltage × Not sensitive to the resistive voltage
× Not detectable when V1 = V2
V1+V2 includes the inductive voltage

Two coil blocks of a QCS magnet

V1

B2GMV26

Quench monitoring system
QCS group

Monitor group

Coil voltages of all QCS magnets

Abort kickertrigger

Beam current
Quench detector 1
Beam loss monitor

Quench detector 2
Quenchtrigger

QCS Data logger

Data logger

 Coil voltages of all QCS magnets are monitored by the QCS data logger.
 We can compare the magnet voltage of QCS group with the beam loss ofmonitor group by using the same signals of abort kicker and beam current.
B2GM7

Collimator installation planNo. of collimators
Phase-2

LER

HER

Horizontal

4

10

Vertical1

9The number of collimators
was not enough for LER inphase-2.
The damaged collimators of
D2V1 (LER) and D1V1 (HER)
were replaced.

IR meeting 2019/01/24 by Antonio Paladino

Phase-3

LERHER

Horizontal

711

Vertical

29

LER beam loss is expected tobe suppressed by the addedcollimators.
B2GM8Loss monitor around the collimator
No. of collimators
Phase-2

LER

HER

Horizontal

410

Vertical

19

The number of collimators
was not enough for LER inphase-2.
The damaged collimators ofD2V1 (LER) and D1V1 (HER)
were replaced.

IR meeting 2019/01/24 by Antonio Paladino

Phase-3

LERHER

Horizontal

711

Vertical

29

LER beam loss is expected tobe suppressed by the added
collimators.
B2GM

9

Belle diamond abort system
Diamond system may prevent QCS quenches by aborting the beams.

QCS quench meeting 2018/05/23 by Giovanni Bassi
B2GM

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Additional tungsten shield Several additional tungsten shields were proposed to suppress the beam loss tothe QCS magnet.
 The tungsten shields are supposed to be placed between the QCS inner pipe andbeam pipe.
 Some simulation results, which were reported by Y. Funakoshi, show the tungsten
shields may effective to suppress the beam loss.
 To determine the detail shape of the tungsten shields, we need more informationof the beam loss simulation from Y. Funakoshi and H. Nakayama.
QCS-RQCS-L

B2GM

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Summary In phase-2, most quench was caused by the unstable beam injection
and the incomplete collimator setting. After the tuning of injection
and collimator setting, no quench occurred from May 25th to June
25th.
 Quench protection and monitoring systems of QCS group are all
ready for the phase-3 commissioning.

 LER beam loss is expected to be suppressed by the added collimators.
 We also expect the Belle diamond abort system work well in phase-3.
 For the additional tungsten shields, we need to continue to discuss
the detail.
B2GM

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