Beam aborts status
The 23rd KEKB Accelerator Review Committee
2019/7/8 H.Ikeda

The 23rd KEKB Accelerator Review Committee

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Contents
1. SuperKEKB abort system
2. QCS quench abort @Phase-III
3. Speedup of the abort
4. Summary

The 23rd KEKB Accelerator Review Committee2

1. SuperKEKB Abort System
In order to protect the hardware components of the detector andthe accelerator against the high beam currents, we installed thecontrolled abort system.

Dumped beam length : one revolution time (10 μs).
Build-up time of the magnetic field of abort kicker magnet : 200 ns(empty bucket space).
Synchronization of the kicker timing and the abort gap timing isrequired for the protection of hardware.
The 23rd KEKB Accelerator Review CommitteeT. Mimashi
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Abort Trigger
The abort request signals from each hardware component are collected in 12 local control rooms (LCRs).
The request signals from LCRs, software abort request signals, and manual abort request signals arecollected in the central control room and the abort kicker trigger is sent to the abort kicker.
D１e-IP(Belle)

e+Abort Source (>130)
RF Cavity voltage, Arc sensor,Cooling water flow andtemperature,
He liquid level and tankpressure ,etc.
Beam Phase

D4OhoNiko

Central ControlRoom
Interlock Module
Abortkicker

Transfer Cables(max. 3km long)

Magnet(Comparator current)

D10: Experimental Hall
CCR

12 Local Control Rooms
Interlock Module (OR and LatchingCircuit): Local Control Room

Vacuum Pressure,
Cooling water flow andtemperature
SR Monitor (Chiller power): Data Logger
e+eFuji: RF Station

Loss Monitor (PIN,IC)

ManualBelle-II (VXD diamond)

Software: Collimator
D7: Ion Chamber

The 23rd: Loss
KEKB
Accelerator
Review CommitteeMonitorSignal: Abort Request Signal

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Beam Abort Delays
Beam Abortrequest

a failure is detected…

Devicerequests
Abort> ~2μs

Hardware dependent

Beam Interlock system
Process< ~10 μsSignal
sentto Kicker

Beam Dumping
System waiting
for beam gap

Kicker fired

LER7μs～17μs
HER6μs～16μs

max 10μs

All bunches
are aborted

t3
t2
t4
t1
To summarize the abort request
Synchronization of the abort request signal with revolution
on the beam abort system.
in FPGA.：Max delay=10μs
Depends on the optical cable
Delay to synchronize to the abort gap(fixed delay) : 4.2μs
length from the local control room for LER, 2.8μs for HERto CCR.
Delay from CCR to kicker (400m) : 2μs
10μs for D1, D2(near Belle-II), Thyratron ON :1μs
Rise time for the kicker : 200ns
TheD8
23rd KEKB Accelerator Review Committee
52μs for D7 orLoss Monitor Abort• Free Air Ion Chamber (20D co-axial cable ) : whole ring to cover a wide range in space.
• PIN Photodiode (2.65mm × 2.65mm) : downstream of Collimator and other.
tunnelLCRAnalog outIC(～ms)

IntegratorGain(×1/×10/×100)
～20μs

EPICS

ADC

Analog out
I/L signal

kblog

Regularly record
Sampling time: ～1sec

Data logger

Trigger: abort trigger
Sampling time:～μs

Interlockmodule

Abort trigger

200ns
Analog outPDIntegrator
peak&hold circuit
Gain(×1/×10/×100)

ADC

EPICS

Analog out

I/L signal
The 23rd<2μs
KEKB Accelerator
Review Committee

kblog

Regularly record
Sampling time: ～1sec

Data logger

Trigger: abort trigger
Sampling time:～μs

Interlock
moduleAbort trigger6

Abort analysis• Abort Timestamp Log (Control)• The order of abort trigger received at LCR islogged.

• Each group prepares the logging system.
• Abort trigger is input as reference.
• Monitor (LM, TbT BPM)
• QCS
• RF• Belle-II

The 23rd KEKB Accelerator Review Committee7

2. QCS quench abort @Phase-III
Day/time

ReasonRing

Vacuum Spike

1st Abort trigger

1

5/28 01:32 - 22:20

QC2LE PS trouble

HER-

LM@D1H5 collimator2

5/31 19:49 - 22:00

Beam loss

LER

D06_L07 3.98E-7 Pa (B2P_65)

LM@D6V2 collimator3

6/6 14:53 - 18:19

QC2LE PS trouble

HER-Belle2 VXD diamond4

6/9 22:11 - 6/13 19:01

Beam loss(155mA)LER

D02_L18 3.64E-5 Pa (D02_V1 collimator)
D05_L20 9.64E-8 Pa (between D05 ARES and wiggler)
D06_L25 4.86E-7 Pa (D06_V2 collimator)
D11_L22 8.35E-7 Pa (NIKKO D11wiggler)

Belle2 VXD diamond5

6/27 11:41 - 12:34

Beam loss

LER

D03_L20 1.17E-7 Pa (B2P_96)

Belle2 VXD diamondThreshold and range of Belle-II VXD diamond abort was changed at 6/5.

The 23rd KEKB Accelerator Review Committee

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Ex1. 5/28 01:32 QCS quench(HER)• Caused by QCS PS problem.
• The beam loss was detected at D1H5 collimator.
• QCS quench I/L ～13ms• QCS PS OFF I/L ～63ms

The 23rd KEKB Accelerator Review Committee9• The beam loss occurred at D1H5 collimator several ms after QC2 LE PS problem.
HER abortkicker trigger

Quenchdetector 1trigger

QC1LE Coilvoltage

QC2LE Coilvoltaget (μs)The 23rd KEKB Accelerator Review Committee

Y.10Arimoto• The beam loss occurred at D1H5 collimator several ms after QC2 LEPS problem.
• t1～60μs• t1→t2～10μs• t2→t3～6to16μs• t3→t4～10μs• Sum=90～100μs• QCS quench I/L ～13ms after the LM trigger.
• QCS PS OFF I/L ～63ms

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Ex4. 6/9 22:21 QCS quench(LER)• D02V1 collimator head was damaged.
• The beam loss detected at Belle-II VXD diamond at first.
Following times are the delay from diamond trigger.
• RF D5F arc sensor : 8μs• Loss Monitor D4-3(D6V2 collimator) :16μs• Loss Monitor D1-1(D2V1,H4,H3 collimator) :16.5μs• Loss Monitor TSUKUBA B4(D2H4 collimator) :39.9μs• Loss Monitor D4-1 (D3H1 collimator) :48.3μs

D02_V1 BottomBeam• QCS quench I/L :～16ms• QCS PS OFF I/L :～49ms
The 23rd KEKB Accelerator Review Committee

12 mm12(Y.Suetsugu)

Abort timing dose not synchronize with LER 6.25Hz injection.

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It took 30μs from starting beam loss to abort.
LER beam was lost about 150mA at that time.

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LM signal start at ～30μs before from abort trigger (40μs before from beam off ).

The 23rd KEKB Accelerator Review Committee15• Belle-II beam dose start to increase 50μs before beam off.
• Belle-II abort can be delivered within 10μs(samplingtime)+700ns.
• Change of QCS voltage started 40μs before abort trigger(50μs before beam off).

L. Vitale
The 23rd KEKB Accelerator Review Committee16• Beam orbit (H) moved 0.05mm a few turn before
beam off.
• Beam oscillation was not observed before thattiming.
• RF arc sensor signal start to change 40μs before
beam off.

5 turnThe 23rd KEKB Accelerator Review Committee

M.Tobiyama

17M.Nishiwaki

• Abort timing dose not synchronize with LER 6.25Hz injection.
• It took 30μs from starting beam loss to abort trigger.
• LER beam was lost about 150mA at that time.
• Loss monitor, Belle-II diamond and RF arc sensor showed the signal atsimilar timing.
• Beam orbit started to move at similar timing with beam loss.
• We could not find any beam loss or other behavior.
• Beam loss may be caused by dust since vacuum spike happened at that time.
• Abort delay estimation is consistent with the observation.
• t1～10μs (Signal reach to I/L level at 2nd turn.)• +8μs @ D5F• +16μs@D6V2 collimator etc.

• t1→t2～10μs• t2→t3～7to17μs• t3→t4～10μs• Sum=37～47μs

The 23rd KEKB Accelerator Review Committee18

3. Speedup of the abort
1. Minimize t1(Detector response time)① QCS magnet• Quench detector : Shorter checking time 10ms→2ms for stronger protection of QCS magnet.： (Done)• QCS PS I/L : Remodel the PS module to take out abort signal directly from FPGA without conventional PLC when
there is a failure in a power supply. (start from main magnet)② Beam loss detection• Make the threshold of the detectors severe and keep redundancy.
• Loss Monitor : Set lower threshold• Use PIN at the place besides collimator.
• Make the injection veto system for collimator PIN. (from D6V2 as a trial)• RF D5F arc sensor : Set lower threshold and shorter checking time (6μs→). : Use temporarily.
• Belle : Make shorter sampling time (10μs→<5μs)

2. Shorten t2-t1(Distance from CCR)

• Detect the beam loss by the detector near CCR.

• D6V2 collimator PIN signal send to D7 in stead of D4.

3. Shorten t3-t2• Increase the number of abort gap (1→2)• Shortened time < 5μs

We perform all of these before autumnrun.
The 23rd KEKB
Accelerator Review Committee

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Ex1. 5/28 01:32 QCS quench(HER)• The beam loss occurred at D1H5 collimator several ms after QC2 LEPS problem.
• t1～60μs→2μs• t1→t2～10μs→5μs• t2→t3～6to16μs→6～11μs• t3→t4～10μs• Sum=90～100μs→23～28μs• QCS quench I/L ～13ms• QCS PS OFF I/L ～63m→30～40μs after PS trouble
The 23rd KEKB Accelerator Review Committee

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Ex4. 6/9 22:21 QCS quench(LER)• The beam loss detected at Belle-II.

• t1～10μs (Signal reach to I/L level at 2nd turn.) →2μs
• +8μs @ D5F→2μs• +16μs@D6V2 collimator etc. →2μs

• t1→t2～10μs→5μs• t2→t3～7to17μs→7～12μs• t3→t4～10μs• Sum=37～47μs→24～29μs• QCS quench I/L ～16ms→8ms• QCS PS OFF I/L ～49ms
The 23rd KEKB Accelerator Review Committee

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Summary• The abort system of SuperKEKB works well.
• But some sudden beam loss caused QCS quench and gavedamage to a collimator and a Belle-II detector before a beam wascompletely aborted.
• (The beam loss caused by dust ?)• We improve the abort trigger to abort beam as fast as possible
before autumn run.

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BackUpThe 23rd KEKB Accelerator Review Committee

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Abort Request• Hardware• Electric signal → E/O → Abort system (synchronized to revolution)• RF, Magnet, Vacuum, Safety, Monitor (Loss monitor), etc.
• Delay < 3 turns of revolution (see next page)• Software• From many IOCs (not needed instant response)• RF, Vacuum, Monitor (Temperature, FB reflection etc), etc• Depends on the software processing time (both in local IOC and abortIOC), total time <few seconds.

The 23rd KEKB Accelerator Review Committee

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QCS quench overview（有本氏）• QC2LE• Power supply went to a slow down process due to IPM-abnormality
alarm• QC1LE• Quench was happened.
• It is deduced that beam hit QC1LE ( the beam orbit was changed due tothe slow down of QC2LE).

e-QC1LEQuench

The 23rd KEKB Accelerator Review Committee

P.S. slow downe+25

5/28 Quench : Arimoto

QCS Power Supply
error

PLC
~20 msserious
error

FPGA

~20 msQCS PS I/L~20 msQCS PS…
QCS PS

PLC

HER

E/O

LER

time-lag : 40 ~ 60 ms

HER
LER

The 23rd KEKB Accelerator Review Committee

Abortsystem

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S.NakamuraImprovement plan
QCS Power Supply
t=0error

PLC~20 msseriouserror

FPGA~20 mst =~μs

Abort SystemQCS PS I/L~20 ms
QCS PS…
QCS PS

PLC

HER

E/O

LER

The 23rd KEKB Accelerator Review Committee

time-lag : 45 ~ 65 ms

HER
LER

Abortsystem

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S.Nakamura