Main Ring Magnet System
Phase 2 & Phase 3
Magnet group
T. Adachi, K. Egawa, T. Kawamoto, R. Sugahara,
M. Masuzawa, Y. Ohsawa,S. Nakamura, T. Oki, R.Ueki

Contents
Introduction to the MR Magnet Systeml Operation and work summaryl Magnetsl Power supplies (MR normal & QCS)l Survey and tunnel motionl Summaryl

MR Magnet System @KEKB Review

Introduction to the MR Magnet System
Ring# of larger magnets
Water-cooled/air cooled

Correctormagnets(air-cooled)

HER

740/6~420

LER

986/12~410

More than 1700 water-cooled magnets
More than 800 air-cooled corrector magnets
Integration of this large system went well,which contributed to a smooth start-up of the MR
in Phase 1.

Breakdown
Recycled & Newly fabricatedExamples of new magnets

LER B

LER wiggler section
New layout

MR Magnet System @KEKB Review

IR and the straight sections
at both sides of the IP(HER and LER)

Magnets

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Operation and work summary
Magnetsl IR construction (Phase 2) & Re-construction (Phase 3)
The 1st beam-beam deflection
signal, obtained by shifting theelectron beam (HER) by ~30 µm
using a set of dipole corrector
magnets in the HER.

l From Phase 2 to Phase 3: IR skew quads
Skew quad strength increased from 0.0017 to 0.0038 [T] byadding more turns, for a larger knob tuning range (R. Ueki).

MR Magnet System @KEKB Review

Operation and work summary
Magnetsl From Phase 2 to Phase 3: Skew sextupoles
The skew sextupole magnets used for KEKB luminosity tuning were hocked back up in HER.
This is done partially to determine the specifications for the SuperKEKB skew sextupoles
magnets.

From Jun 22 swing shift report:HER IP chromaticity scan
→Not sensitive, limited by hardware tolerancesl More study is probably needed todetermine the specifications.
l We would also like to see the effectsof the LER tilting sextupole magnets
in Phase3-2.
l From Phase 2 to Phase 3:# of skew quadrupole correctors in the arc sections was doubled by installing more power
supplies the skew windings on the sextupole magnets.
Example:Skew quad coils
on sextupoles
used (LER optics
correction)

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Operation and work summary
Operation and work summary
MagnetsMagnets
Troubles : Water leak from the flow switch of an HER dipole magnet
Troubles: Waterleak abortfrom theflow switchof (Phasean HER 2)
dipole magnet→ Interlock→ Beamon April
15, 2018→ Interlock → Beam abort on April 15, 2018 (Phase 2) Diaphragm type flow switch
Diaphragm type flow switch
Photo by Y.Ohsawa

Degraded over time (~20 years since
Degradedoveristime(~20 years
since
KEKB startup)
the causeof this.
All ofKEKBstartup)
isthecauseofthis.
Allfromof
the water-cooled magnets recycled
themagnets
recycledfromKEKBwater-cooled(more than 1000!) facethis aging
KEKBissue (more than 1000 !) face this aging
issuellll

We replaced all the flow switches of the HER dipoles in the fall of 2018, as a start.
Weall thethe flow
flow switches
switches ofof thethe HER
HER quads
dipolesininthis
thesummer.
fall of 2018, as a start.
We replaced
will replace
We will replace the flow switchesof the HER quads in this summer.
MR Magnet System @KEKB Review
MR Magnet System @KEKB Review

Power Supplies

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Operation and work summary
Power supplies
Main Ring power supplies
Output power

New

From KEKB(# overhauled)

Magnets

0.95 MW20

Main dipoles

0.4-1 MW90Wigglers

0.1-0.5 MW

018#

Main quadrupoles

2-105 kW92

335#

Bend./Quad./Sext.

0.3-2.4 kW

138

1681

Steering magnets/correction coils

Total

359

2034

2393 power supplies (as of June 2016)

Large class PS

Medium class PS

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Small class PS

Operation and work summary
Power supplies
MR PS: # of Failures in Phase 1, 2 and 3 (by S. Nakamura)
Failures in Large class PS (BM /Wiggler)# of event(P1→P2→P3)

comment

AC input over current

13 → 1 → 0

AC Line distortion

AC input Stop, CB Fault

6→0→0

Earthquake

Thermostat
Failures in Medium class PS(Quad. / Sext. / local Bend)

1→2→0High ambient temperature# of event
comment(P1→P2→P3)

Magnet cooling waterflow switch level set toohigh (human error)
Workers not welltrained…we will be careful
next time.

IGBT module fault / Over current

6→1→0

Modules were replaced.

Cable GND fault

1→0→0

Cable fault.

AC over current0→2→0

Most likely false alarm.

External I/L

3→1→6

Low magnet water flow.

Tracking error / Over voltage

3→0→2

Fault in the polarity inversion circuit(P1).
Fault in the control board(P3).

Thermostat

7→ 13 → 1

High ambient temperature & Failure in the thermostat.

Failures in small class PS# of event(P1→P2→P3)

comment

DC-DC board failure
Output over voltage etc.

10 → 2 → 0

Power supplies themselves were replaced.

MR Magnet System @KEKB Review

Operation and work summary
Power supplies
MR PS: # of Failures in Phase 1, 2 and 3 (by S. Nakamura)PS stop due to AC line distortion

No more “AC input O.C. ”
due to AC line distortion
after we installed additionalinductance
MR Magnet System @KEKB Review# of thermostatinterlocks(due to overheating)are reduced after
increasing the # ofoutside air intake fansto the utility buildings
and spot coolers etc.

Operation and work summary
Power supplies
No more PS failure from “AC input O.C. ” caused by AC line distortion.
Adding reactance to the circuit
PS stop due to AC line distortion

The current surge due to avoltage drop becomes smaller.
PS failure from O.C.
(over current) does nothappen.

Coils
Stable operation
Example of AC distortion, RF crowbar work

13% drop

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Operation and work summary
Power supplies
Overshoot problem with Large Scale power supplies (Hitachi) andQCS power supplies (Nichikon)

Digital feedback program is modified.
(LER Dipole power supply case is shown as an example)
Still some overshoot is seen in the Hitachi power supplies.
The new program is being tested now.
There is no overshoot problem any more with the QCS power supplies (Nichikon).
MR Magnet System @KEKB Review

QCS Power supplies

MR Magnet System @KEKB Review

Operation and work summary
Power supplies
QCS power supplies
MagnetRated Output# of PSʼs

Main Quads

2000A, 15V

8Correctors

70A,

43 + 2 (Spare)

ESL (Compensation solenoid)

410A, 30V

1

ESR1 (Compensation solenoid)

455A, 45V

1

ESR23 (Compensation solenoid)

155A,15V

110V

Main quadrupole magnet:
Stability : 2 ppm/8 hours
Ripple: 1 ppm
Correction coils:
Stability : 5 ppm/8 hours with low cost
From T. Oki (KEKB Review 2018)

More work still needed to realize this stability
MR Magnet System @KEKB Review

Operation and work summary
Power supplies
QCS power suppliesl We replaced these modules, but that did not cure the "gate signal going nuts suddenly” disease.
The control board sent back to Nichikon has not shown any problems so far. Investigation
continues.
Trigger signal can be issued within (10 + a few) µs

l For the fall run, we will prepare a fast abort signal (10 + a few µs and transmission time fromthe IP to the abort kicker) for the case where the QCS power supply self-diagnoses a problem.

QCS power supplies (in response to the 22nd KEKB Review)
R19.1: A significant test should be made on the monotonicity of the digital feedback path with the two 20-bit DACs, extending
over the change-over between the 2 DAC systems (i.e with more than 16 counts, and including studies over a significant dynamicrange of the output).

Test carried out on the monotonicity with the actual PS

Monotonicity confirmed

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Survey and tunnel motion

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Operation and work summary
Survey & tunnel motion
Requested to survey and help re-aligning the collimators by thevacuum group after Phase 2.
We did a survey using a laser tracker and found out thatl D2V1 collimator was off by a few millimeters.
l D1V1 collimator was off by about 1mm.

Defining the beam line in such a place (between adipole and quadrupole) is not really possible
without a laser tracker.
Vacuum group will prepare holes for holding a LT target.
MR Magnet System @KEKB Review

Photo by S. TeruiOperation and work summary
Survey & tunnel motion

Vertical shaft at 12C

l Effects of the construction of the new facility buildings are still seen by tunnel level survey.
l Average rate of sinking is ~ 1.9 mm/year.

MR Magnet System @KEKB Review

Photo by Y.Ohsawa

Operation and work summary
Survey & tunnel motion
HLS sensor by BINP
(Hydrostatic water Leveling System)
There are 18 HLS sensors at theTsukuba straight section.

The floor level changed during Phase 3.
IP has become a local minimum.

Some seasonal effects areseen.
We suspect that the levelchange has something to dowith the ground water (rain,pumping for rice planting…).

MR Magnet System @KEKB Review

by T. Kawamoto

Operation and work summary
Survey & tunnel motion
HLS@14m from IP

Gap sensor
Vertical steering (ZVQLC3LP)
kick angle

Gap sensors measure the distance between QCS cryostat
and CDCMR Magnet System @KEKB Review

by T. Kawamoto

Operation and work summary
Survey & tunnel motion
Luminosity variation and floor/cryostat vibration are seen and they
are sometimes correlated.

Gap sensor (R-side)

ZDLM 3/28 7:11

LumiBell2 3/28 ~7:00~5Hz vibration, as an example.
There are also vibration at ~1.7 Hz
and 15 Hz and...

Luminosity : S. Uehara(ZDLM), S. Di Carlo, et al. (LAL)
Floor motion : L. Brunetti and G. Balik (LAAP), under the framework of FJPPL& KEK
MR Magnet System @KEKB Review

MR Magnet System Summary
The IR construction went well, which lead to a smooth 1st collision in Phase 2.
l The IR re-construction for Phase 3 also went well, with good reproducibility of theIR orbit.
l Additional coils in the IR skew quads made it possible to scan a wider range in theIR coupling knob scans.
l A water leak from a ~20-year-old flow switch led us to start replacing the flow
switches used in the KEKB magnets.
l This could be a very costly operation so we will do it over time.
l Flow switch is just one of the magnet subsidiary components.
l What about rubber hoses? Will they last for the next ~10 years? Everybodyages.
lThe # of power supply failures decreased from Phase 1 to Phase 3.
Investigation of the QCS (QC2LE) power supply failure due to distorted gate
signals is on-going. This is one of our highest priority items for the summer
shutdown.
l Adding a fast abort signal from the QCS power supplies looks feasible, and we will
try to implement a fast abort signal from the QCS PS for the fall run.
ll

The south arc of the MR continues to sink, at an average rate of 1.9 mm/year.
A correlation is seen between the HLS, the cryostat motion and the steering
currents.
l Some correlation is seen between the fast luminosity signal and vibration data. We
will keep looking into the vibration issues.
llMR Magnet System @KEKB Review