KEKB Injector

Linac Status

Sector-B
Sector-A

KEKB Injector Linac
180deg
ARC

Sector-1

e- Gun for PF/AR

Sector-C

e- Gunfor KEKB

RF modulator

PhotonFactory

Klystron
SLED (RF pulse compressor)
Accl. structures

Sector-5

KEKB
HER/LER(160 MeV/unit)(29 accl. units) = 4640 MeV(55 accl. units) = 8800 MeV

160 MeV/unit

e- to HER:

(160 MeV/unit)(26 accl. units) = 4160 MeV

Sector-4

Acceleration
unit

21 MV/mSector-3

e+ generation target

Sector-2

Energy gain /unit
Acceleration field

4 /unitAccl. structure length 1.928 m# of Accl. structures

e+ to LER:

(160 MeV/unit)

Total Energy gain potentiality

e- to Target:

Charge

Beam Energy
0.8

1.0 nC/pulse

8.0 GeVElectron (e-)

0.5 %

2.5

0.6 (1.2) nC/pulse

3.5 GeV

Positron (e+)(1.1) Injector Linac Performance

Emittance

0.2 %

1.5 (3.0) mA/sec

10-3 mEnergy spread (full width)

3.0 mA/sec

10-3 mInjection rate(for double-bunch inj.)

Typical Daily Run Status

Typical Topup Injection

eInjec-Total Deadtime
for Injection
12 ˜ 13 min.

Injection interval 80 ˜ 90 min.

Mode Switchingtion

Linac Mode

Mode Switching

Injection -> Physics

Switching

Physics -> Injection(Belle status & Ring Tunes)

e+ Injection(Belle status & Ring Tunes)(1.2) Double-Bunch Injection-> Increase positron intensity !

Most of the injection time is spent for positrons !

How ?
(1) Increase primary electron charge ?

-> present 10 nC/bunch is already limited by Wake effect(2) Increase positron collection efficiency-> expensive !
(3) Increase number of the bunches ?

-> Constraint from frequencies of Linac and Ring,Maximum Two Bunches but possible

LinacPrimary Electron

Double Bunch Injection

X-position
Y-position
Intensity

Positron

Transfer Line

1-st bunch

2-nd bunch

Positron Intensity is doubled !

Double Bunch Injection
Single-Bunch Injection Mode

Double-Bunch Injection ModeInjection Rate is doubled ! -> Shorter Injection Time(1.3) Continuous Injection-> Keep Peak luminosity !

(Lifetime : (e-) ˜ 300 min, (e+) ˜ 150 min)Degradation of Luminosity by gradual beam loss

How ?

Continuous beam injection while keeping the detectors turned on-> detectors trip-off by beam background ???
-> anyway, check the detectors tolerance
to injection backgound !

Continuous Injection StudyNo Detectors trip-off !
Positron current kept constant By Continuous Injection !

Injector Upgradefor SuperKEKB(1035 Luminosity machine)

Not Yet an established Project,

Still in a feasibility Study StageUpgrade requirements to Injector
8.0 GeV----->----->

8.0 GeV !!

3.5 GeVSuperKEKB

Beam Energy (e-)

3.5 GeV

KEKB(e+)NEED Energy upgrade for e+ !

9.4 A !!

SuperKEKB

0.9 A ---> 1.1 A --->

4.1 A !!

KEKB designStored current (e-)

1.4 A ---> 2.6 A --->

May 2002(e+)

NEED Intensity upgrade for e-/e+ !

(2.1) Intensity Upgradee- Intensity increase(5 nC/pulse)

3.0 mA/sec --> 15.0 mA/sec(1 nC/pulse)

already 10 nC e- beam is used as primary* Beam quality issue due to Wake fielde+ Intensity increase(1.2 nC/pulse)

1.5 mA/sec --> 3.0 mA/sec(0.6 nC/pulse)

e+ capture section upgrade

With stronger focusing solenoid (flux concentrator?)(2.2) High Gradient Scheme

To raise e+ Beam energy ; 3.5 -> 8.0 GeV,

Acceleration Field gradient will be doubledby using C-band (5712 MHz) components.

B

1.7-GeVJ-arc for e–CA

1eGun

2e+ targetE(e–)=3.5 GeV,
Q(e–)=10 nC
to target
Q(e–)=5 nC
for Injection

DampingRing

3E(e+)=1.0 GeV
Q(e+)=1.2nC

4

New C-band units

5E(e+)=8.0 GeV,
Q(e+)=1.2 nC
HER

LER
E(e–)=3.5GeV,
Q(e–)=5 nC

24 accl. units are Replaced to C-band (Eacc = 21 -> 42 MV/m)(Egain = 160 -> 320 MeV/unit)(max. e+ total Egain = 4640 -> 8640 MeV)
e+ Damping Ring for smaller emittance and beam size
to fit for smaller aperture in C-band accl. structures

C-band Components* Klystron-> Toshiba 50 MW klystron available* Pulse Modulator-> Compact Modulator* RF-pulse compressor-> TE038 cavity (LIPS-type)* Accelerating structure-> 2p/3-mode travelling-wave type(2.3) Re-circulation Scheme

To accelerate e+ to 8.0 GeV,

They are re-circulated to upstream and areaccelerated in the linac twice.

B

1.5-GeVJ-arc1 for e–
J-arc2 for e+CA

1E(e–)=3.5 GeV,
Q(e–)=10 nC
to target
Q(e–)=5 nC
for InjectioneGune+ target
2Damping
Ring

3E(e+)=1.0 GeV
Q(e+)=1.2nC

45E(e+)=8.0 GeV,
Q(e+)=1.2 nC
HERLERE(e–)=3.5GeV,
Q(e–)=5 nC

No significant Upgrade in RF sources & acclerating structures

e+ Damping Ring for synchronization to next RF pulse
e+ beam return line, 2nd J-arc for e+, target-bypass beam line--> Multi-Beam acceleration in same RF pulse(primary e- and e+) (high E e+ and low E e+)

For the simultaneous acceleration ofe- and e+ beam and2-3 unit

2-4 unitlowE(0.4 GeV) e+

low Energy e+ and high Energy e+ beams

2-2 unit

highE(3.5 GeV) e+e+ target
2-1 unit

complicated transport line isBende- beam fore+ generationnecessary.

KickerBend
Bend

3.5 GeV e- for LER

2-6 unit