Recovery of injector linac

Kazuro Furukawa
for Injector Linac group
July 9, 2019

Injector Linac

K.F, KEK, Jul.2019.

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Injector Linac andAccelerating structure assembly room
Accelerating structureassembly room

Southern 1/3 of Injector
Sector B

Ａセクター

Ｂセクター

機械、
電気室

機械室

A1_A
B7

B8

加速管組立室

B5

B6B3

B4

B1

B2

SB_B AC

A4AB

A3AD AA

A2

A1_B

機械室

副制御室
MB
SB_C
C1

C2

C3

C4

C5C6C7C8加速管準備室

SB_1

1112

FC_13
1A15 FC_15

1E

161718

1B 1C

電気室 空調機械室

Sector R
J-ARC

Sector C
Cセクター

１セクターv Sectors B, R, C had to be recovered³ Approximately 25% of the Injector
Injector Linac

K.F, KEK, Jul.2019.

2Injector Recovery
u No injury
u Fire already extinguished before firemen enteredu No direct fire damage on the injector itself
u However, carbon soot sneaked into the injector
v Discharge might prevent high-voltage operation of high-power
pulsed modulators
v Short-circuit might prevent high-precision operation of theinstrumentation

u Chemical material (Dioctyl Phthalate) accompanied withcarbon sootv Required protective clothingu Balance between quick recovery and complete cleanupv Certain recovery was left for summer shutdown
Injector Linac

K.F, KEK, Jul.2019.

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v Carbon soot sneaked through holes between rooms

Injector Linac

K.F, KEK, Jul.2019.

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v Carbon soot in the equipment

Injector Linac

K.F, KEK, Jul.2019.

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v Cleanup one by one

Injector Linacv Low-power & high-power tests

K.F, KEK, Jul.2019.

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u Information Sharing
via Meeting,Mail and Web
v Meeting in every morningv Group leader meetingin every eveningv Daily updatev Mental healthv Physical healthv Environmental analysis
v Recovering strategy
v Utility recovery
v Equipment recovery
v Testing progress
v Beam schedule

Injector Linac

K.F, KEK, Jul.2019.

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Recovery progress
Apr.3: Fire. Carbon soot was anticipated for high-power and high-precision operation.
Apr.4: During the investigation, hazardous chemical material was found as well as carbon
soot.
Apr.5, 6: Partial clean-up was performed as a test, and also for devices to be sent out tomaker companies, with limited pieces of protective clothing.
Apr.8: As protective clothing arrived, full clean-up started. Several devices were found tobe difficult to fix in a short term, and an operation plan was developed.
Apr.18: Low power test started.
Apr.22, 23: High power test was performed successfully.
Apr.23: Beam test began.
Apr.25: Limited HER injection started.
Apr.26: HER and LER injections, and then collision started.
May.7: PF light source injection as originally scheduled.
Injector Linac

K.F, KEK, Jul.2019.

8Impact on Injector
u Recovered with much help from everyone
v All divisions in KEK and outside companies

u Certain equipment was postponed to recoverv Energy lowered from 1.5 GeV to 1.35 GeV³ at J-ARC, 180 degree bending sectionv Until summer shutdown³ 2 of 60 RF sources would be off³ 1 of 2 bending magnet power supplies would be off

v Found not to impact much on the injection³ with present beam specifications

v Should be recovered before autumn operationu Many of backup devices were consumed
v May mean acceleration of renewal for aging devices, actually

u Budget may depend on insurance refund
v Planning in this and the next fiscal year

Injector Linac

K.F, KEK, Jul.2019.

9Injector Operationu Capacitors at injector are different from Nextef's
v Has ceramic container instead of plastic containerv Has lower designed potential gradient (longer lifetime)v Has puncture protectionv Performed degradation check every summer

u Tentative operation procedure in injector linac
v Local operator investigation is enforced on modulator HV interlock³ Observation for any anomalous behavior or capacitor puncturev More frequent observation of southern part of injectoru More surveillance devices would be installedu Important to start S-band structure assembly in 2020v As originally planned to fight against aging structuresv Structure assembly room should be recovered earlyu Careful knowledge transfer from the original designer to the next
generation
Injector Linac

K.F, KEK, Jul.2019.

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Impact on SuperKEKB Operationu Beam suspension for 3 weeks³ at the first stage of phase 3 operation³ at the middle of luminosity development

Fire Recovery

Injector Linac

K.F, KEK, Jul.2019.

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Impact on SuperKEKB Operationu Operation suspension for 3 weeks was unfortunate, butu Resultant recovery did not impact the operation muchu Part of suspension would be compensated in 2020u For example of recoveringv Simultaneous top-up injection was initiated as originally plannedv It is one of the mission of the injector in upgrade

Injector Linac

K.F, KEK, Jul.2019.

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Pulse-to-pulse modulationu Four PPM virtual accelerators
for SuperKEKB project
Based onDual-tier controls withEPICS and event-system
Independent parameter setsfor each VA (20ms)>200 parameters
for equipment controls
many more
for beam controls
maybe with additional PPM VAof stealth beam
for measurement

Event-basedControl SystemEvery
20 msF.B
F.Be− GunARCPF Injection�

e– (2.5GeV, 0.2nC)

F.B
e− GunARC

Damping ring

SuperKEKB-LER Injection�

F.B

e– (3.5GeV, 10nC)

F.B

e+ Targete+ (4GeV, 4nC)

e− GunARC

SuperKEKB-HER Injection�

F.B

e– (7GeV, 5nC)
e− GunARC

F.B

PF-AR Injection�

F.B
e– (6.5GeV, 5nC)

Injector Linac

K.F, KEK, Jul.2019.

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Simultaneous 4 + 1 Ring Top-up Injection
u Realized for the first time
³ SuperKEKB HER 7 GeV e–³ SuperKEKB DR and LER 4 GeV e+³ Photon Factory 2.5 GeV e–³ PF-AR 5.0 / 6.5 GeV e–v4 beams are modulated at 20
ms PPM
vMore than 200 pulsed devices
were constructed forSuperKEKB, as well as beamand RF monitors
vInjection noise (background)
were well studied from the 2nd
week of May
Injector Linac

HER

337.5 ± 1.6 mA (0.48%)

LER

348.2 ± 1.2 mA (0.34%)

PF

449.9 ± 0.1 mA (0.02%)

PF-AR

55.1 ± 0.2 mA (0.38%)

K.F, KEK, Jul.2019.

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Simultaneous Top-up Injections
uIntegrated luminosity improvement (example)
17.54 /pb in 5.15 hr(5 fills)
on May.6

41.64 /pb in 5.15 hr(top-up)
on May.16

237%
improvement
Injector Linac

K.F, KEK, Jul.2019.

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Developments
u Recommendations in the previous review meeting
vStill working on themv3. Continue to develop the critical injector systems, including theRF gun and the positron source. Identify the sources of emittanceblow up and beam jitters through beam studies. Develop adetailed plan for reducing the injection emittances from about
150 micron for Phase II to the needed 20 to 40 micron for Phase
III. (R3.1)
v4. Perform a new study to improve the work hardening process ofthe copper FC coils. Compare with the experience at otherlaboratories, e.g. at SLAC and BINP. (R7.3)
vetc.
vReports will be provided in the following talks

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Talks on Injector Linacu Beam background (Injection tuning)u Fire at Nextef
u Recovery of injector linac
u Injector beam operationu Injector RF and LLRF
u Injector beam monitors
u RF gunu Positron sourceu Emittance preservation

Injector Linac

N. IidaT.Abe
K. Furukawa
M. SatohT. Miura
F. Miyahara
R. Zhang
Y. Enomoto
Y. Seimiya

K.F, KEK, Jul.2019.

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SummarySummary
u We should not have the same disaster with better preparationu We are slowly recovering from the disasteru We are improving the injector learning from the beam as well as thepast experiencesu Trial and error for new challenges may be necessary depending on
many parameters along the accelerator chainu With some Phronesis we can enjoy accelerators
v Phronesis [Greek]: Practical wisdom, Ability to understand the Universal Truth

Injector Linac

K.F, KEK, Jul.2019.

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Mt. Tsukuba

Thank youPF-ARPF

SuperKEKB
dual rings

700m Injector
LinacConference papers at <http://www-linac.kek.jp/linac/>
Injector Linac

K.F, KEK, Jul.2019.

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Injector Linac

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Injector Linac

K.F, KEK, Jul.2019.

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Timeline
uDuring SuperKEKB operation in decay mode
u20:58 Last surveillance performed
u21:15 Interlock interrupted the Nextef operation
u21:44 Fire alarm
u21:48 Much smoke foundu21:50 – 22:05 Firemen called and arrived
u23:15 Checked by 6 firemen, radiation manager
uHigh power modulator was found burnt
vAccelerator structure assembly room
vUsed for X-band development test facility (Nextef)
Injector Linac

K.F, KEK, Jul.2019.

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First KEK announce on April 4thFire in the accelerator structure assembly room atelectron-positron injector linac
At 9:44 pm on April 3rd, on the KEK Tsukuba campus, a fire alarm
went off in the accelerator structure assembly room at electronpositron injector linac (a general radiation area) and the fire
department was called to the site.
The cause of the alarm was determined to be an electric pulse
modulator used in microwave power source, which had suffered aburnout.
This event did not cause any human injuries or radiation leakage.
We apologize to everyone for any concern or alarm. For a timelineof the incident and other details, please see the following link.
Timeline
9:44 pm
Fire alarm goes off, 2 researchers from Accelerator division 5 go to
the accelerator structure assembly room with the alert and confirm
the presence of smoke.
9:52 pm
As a safety precaution, the accelerator’s beams are aborted.

Injector Linac

11:15 pm (approx.)
Firefighters and KEK Tsukuba Campus Radiation Safety personnel
enter
the site, confirm that there is no danger from radiation, heat, etc.
As there was no danger of fire spreading to radioactive isotopes,
external shutters were opened and the room was vented naturally.
1:30 am, April 4th
The fire is confirmed to be extinguished.
2. Pre-fire Conditions
A check around 7 pm noticed nothing out of the ordinary. Around
9:30 pm the pulse modulator was remotely confirmed to havestopped unexpectedly.
3. Fire Location and Cause
Performance tests of the accelerating structure require microwaves,and we believe that a pulse modulator used in their generation had
an undetermined malfunction that caused it to emit smoke. The exact
cause is under investigation.
4. Effect on Accelerator Experiments
The accelerator in the Electron-Positron Injector linac delivers
electrons and positrons to the SuperKEKB collider and the Photon
Factory light sources, but research carried out in the accelerating
structure assembly room is entirely separate from theseaccelerators.
This effect that this incident will have on on-going experiments iscurrently under investigation. Once it has been confirmed to be safe,
the experiments plan to restart.

K.F, KEK, Jul.2019.

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