Recent Status
ofElectron/Positron Injector Linac
Kazuro Furukawa
for Injector Linac, KEK
Many slides from Y. Enomoto and S. Matsumoto

Injector Linac Status

K.Furukawa, B2GM, Feb.2018

1

Injector Linac Mission

Mission of Electron/positron Injector in SuperKEKB
v For 40-times higher luminosity in SuperKEKB collider
v Low emittance & low energy spread injection beam with 4-5 times higher beam current³ New high-current photo-cathode RF gun³ New positron capture section³ Damping ring construction³ Optimized beam optics and correction³ Precise beam orbit control with long-baseline alignment³ Simultaneous top-up injection to DR/HER/LER/PF/PFARv Balanced injection for the both photon science andelementary particle physics experiments

The single injector would behave asmultiple injectors to multiple storagerings by the concept of virtual
accelerator
Injector Linac Status

K.Furukawa, B2GM, Feb.2018

2Injector Linac Overview
uInjector linac configuration

vMajor upgrade items³Photo-cathode RF-gun for low-emittance e³Flux concentrator, LAS structure, solenoids, quads for e+³Pulsed magnets for adequate beam optics for each beam
³High-precision beam position monitor³High-precision beamline alignment for low emittance
Injector Linac Status

K.Furukawa, B2GM, Feb.20183

Linac Beam Property Requirements

Required injector beam parametersStage

KEKB (final)

Phase-I

Phase-II

SuperKEKB(final)Beame+e–e+e–e+e–e+e–

Energy3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeVStored current

1.6 A

1.1 A

1A

1A

––

3.6 A

2.6 A

Life time (min.)

150

200

100

100––

66Bunch charge (nC)primary e- 10→11primary e- 8→ 0.4

10.51

primary e- 10→44

Norm. Emittance(γβε) (µrad)

1400

310

1000

130

200/40(Hor./Ver.)150

100/15(Hor./Ver.)

40/20(Hor./Ver.)

Energy spread

0.125%

0.125%

0.5%

0.5%

0.16%

0.1%

0.16%

0.07%

Bunch / Pulse

222222

22Repetition rate

50 Hz

25 Hz

25 Hz

50 Hz

Simultaneous topup injection (PPM)

3 rings(LER, HER, PF)

No top-up

Eventually

4+1 rings (LER, HER,DR, PF, PF-AR)

Injector Linac Status

K.Furukawa, B2GM, Feb.20184New Schedule

RF-Gun e- beamcommissioning
at A,B-sector

Linac Schedule Overview as of Feb.2018
e- commiss.
at A,B,R,C,1

e+ commiss.
at 1,2 sector (FC, DCS, Qe- 50%)e- commiss.
at 1,2,3,4,5 sector

Phase1: high emittance beam for vacuum scrub
Phase2,3: low emittance beam for collision

Time →Location↓Beam
Licensesin steps

Low
Emittance
Beams

Low
Emittance
Injections

4+1 Ring
Injections

DRCommiss.
1 nC
Phase1

Without Top-up: Electron: Positron: Low current electron

Injector Linac Status

non damped e+ commiss.
at 1,2, 3,4,5 sectors
e- commiss. at A→5 sectors

1 - 2 nC
Phase22 - 4 nC
Phase3

Direct PF-AR BT
damped e+ commiss. Improved
at 1→5 Qe+ = 1~4nC RF gune- commiss.
at A→5 Qe- = 1~4nC

K.Furukawa, B2GM, Feb.20185Newly Installed Pulsed Magnets
KEKB Common optics was enoughSuperKEKB Independent beam optics with26 Quads and 26 Correctors
in Sectors 3 – 510 Correctors
in Sectors 1 and 22 Quads
for Positron Target

Beam energy

HER (7 GeV)
PF-AR (6.5 GeV)LER (4 GeV)PF (2.5 GeV)
ABC12345Sector
Injector Linac Status

K.Furukawa, B2GM, Feb.20186

Pulsed Magnet Installation 1
u Installation during long
shutdown at summer 2017
vNot possible before Phase 1
without DR because of theaperture
vReplacement for 64 magnets
vIn 99 days between May andOctobervAll components including
magnets, girders, cabling,cooling water, controls, etc.
vIn parallel with otherreplacements and installations
Injector Linac Status

2017/3/31
by N.Toge7
K.Furukawa,
B2GM, Feb.2018

Pulsed Magnet Installation 2

u 13 New girders
v each for 2 quads and 2 correctors
v ready for 10 µm alignment to realize low emittance preservationin Phase 3
Injector Linac Status

K.Furukawa, B2GM, Feb.20188

Pulsed Magnet Installation 3Standard cabinet configuration for pulsed magnets
4 quads and 4 correctors for a half sector
Pulsed power supplies
Pulsed power supplies& Interlock system& Interlock system
Controls
for 2 quads and 2 correctors for 2 quads and 2 correctors

Girder and magnet replacements before July
Power supply installation and cabling before September
Comprehensive system tests in September for a month
Injector Linac Status

K.Furukawa, B2GM, Feb.20189Performance of Quad Power Supplyu High performance with energy
recoveryu Drives a 1 mH coilvTotal energy recovery rate ofat 330 A, 340 V, 1.5 ms risetime
68.5％ (measured)vNo need for additional wall
power (only 39kW for all newmagnets)
u High precision and high stability
by analog feedback with IGBTvStability of 0.01％ for 24 hours
u Flexible synchronous controls
with global event control systemvIndependent pulse-by-pulse
modulation at 50 Hz
Injector Linac Status

K.Furukawa, B2GM, Feb.2018

10Power Consumption Measurement
Quad (50 Hz, 300 A) x 1
3000
2628.6

Actual power consumption (measured)

2500

500

76302.6

Total Energy

1000

Heat loss on cables

1500

Heat loss at Magnet

Power (W)

2000

Energy stored in coil inductance

2250

827

0Pjoule-mag

Pjoule-cable

PL

PtotalPmeasured.

Energy recovery ratio = 1 - Pmeasured / Ptotal = 68.5 %Injector Linac Status

K.Furukawa, B2GM, Feb.201811

Stability of Quad Power Supply
25 mA / div

0.014578 A / 165.946 A = 0.0107% / 24 hours (for PF_52_4 magnet)
Injector Linac Status

K.Furukawa, B2GM, Feb.201812

New Pulsed Magnets enabled Simultaneous
PF/PF-AR Injections And 2 Test Beam Accelerations

Injector Linac Status

K.Furukawa, B2GM, Feb.201813

For Phase 3
uPulsed bending magnet addition forswitching between RF electron gun /thermal electron gun
uPulsed corrector additions for offset
injection (orbit control) to enable lower
emittance
u40 magnet replacements if budget allows

Injector Linac Status

K.Furukawa, B2GM, Feb.201814

Planning Pulsed Bend for Merger Line
24-degree Merger
Bend x2
Thermionic Gun
PF-AR
LER (primary e– for e+）
PFHER
Photo RF GunInjector Linac Status

K.Furukawa, B2GM, Feb.201815

DR LTR / RTL Waveguides
nnn

Accelerating
structures for energy /bunch compressors onDR LTR / RTL beamlines
45-m waveguides fromlinac gallery
Fabrication errors of~150 µm were found(while schematics from
KEK and from makerwere correct)
Linac

Injector Linac Status

DRRTL

K.Furukawa, B2GM, Feb.201816

DR LTR / RTL Waveguides
nBunch Compressor on RTL
Injector Linac Status

Components withRed circles had tobe replaced

Energy Compressor on LTR
K.Furukawa, B2GM, Feb.201817

Structure of Waveguide Flange
Metal Seal (Vacuum)
RF Contactor (Electric)

Emphasized figures

Correct

only 150 µm difference
Injector Linac Status

WrongK.Furukawa, B2GM, Feb.201818

Fabrication Error and Recovery
u September 2017vA large reflection was observed from the middle ofwaveguides in the low-power test
vFabrication errors in 58 waveguide flanges were identified
u October 2017vHigh power test was performed at a test stand³Discharge at the gap prevents the power only up to 10%of the nominal power

All 29 wrong waveguides were replaced; some were replacedwith the ones with different length, others were newly fabricatedInjector Linac Status

K.Furukawa, B2GM, Feb.201819

Fabrication Recovery
u Early October 2017
vRemoval of all erroneous waveguides from the tunnel
u Till November 2017
vFabrication, preparation and test of replacement waveguides
u Late November – early December 2017
vRe-installation in between linac operationu December 17 and 24, 2017vHigh-power verification of whole system in between DR
construction
u January 2018vIntermittent RF conditioning in between DR construction
vReached nominal power for Phase 2 and 3 operationvConfirmed the designed energy compression of one third on LTR
Injector Linac Status

K.Furukawa, B2GM, Feb.201820

LTR/ECS – RTL/BCS Waveguide Conditioning

Injector Linac Status

K.Furukawa, B2GM, Feb.201821

Summaryu New Pulsed Magnets
v Successful fabrication and installation of home-grown low-cost
pulsed magnet system during 2017 summer shutdownv 1-month test was performed as scheduledv Experienced no large troubles so far and enabled stable
simultaneous accelerations with different energy beams

u Erroneous Waveguides
v Replacements of 29 waveguides were performed successfully evenduring light source operation and SuperKEKB commissioning /constructionv Achieved the designed energy compression without any harmful
impact against DR commissioningu Injector is ready for Phase-2 commissioning
Injector Linac Status

K.Furukawa, B2GM, Feb.201822

Thank you

Injector Linac Status

K.Furukawa, B2GM, Feb.201823