2004.Feb.17

KEKB Review

Injector Linac Upgradefor SuperKEKB
overview

Kamitani Takuya

1

2

KEKB Injector

Energy gain = 160 MeV/unit with 21 MV/m gradient

The layout is optimized for 8-GeV e-/3.5-GeV e+.
e- to HER : 8 GeV ~ (Primary e- : 4 GeV) + (e+ to LER : 3.5 GeV)

e-/e+ /(PF/AR) injection modes are switched by,retracting/inserting the target from/to the beamline, switching the gun,changing the parameters (magnet strengths, acceleration phases etc).
The switching takes 45 ~ 120 sec.

3Typical operation status (1)(Periodic Injection Mode)• 18~20 injections/day
8 min. for routine refill
23 min. after beam abort• Injection rate
5 mA/s for e– 50 Hz(1 nC x 1 bunch)
3 mA/s for e+ 50 Hz(0.6 nC x 2 bunches)• Belle DAQ* stops
during injection(*) DAQ = data acquisition(**) Luminosity efficiency =integrated lumi./(peak lumi. x operation time)• Lumi. effic.** ~ 66 %

4

Typical operation status (2)(Continuous Injection Mode)• Injecting always
e+ every 20 min.
(target bellows)e– quasi-continuous• Injection rate
1.0 mA/s for e– 10 Hz
0.5 mA/s for e+ 10 Hz• Belle DAQ continues
with short dead time 3.7 ms
after each beam pulse(The less beam rep. rate,
the smaller dead time.)• Lumi effic. ~ 81 %CIM improves the efficiency more than 15 %(~ 84 % on Feb.15)

5

Upgrade Requirements(1)
Beam Energy (e–)
(e+)

KEKB
SuperKEKB
8.0 GeV----->
3.5 GeV
3.5 GeV----->
8.0 GeV !!
-> C-band accelerator modules(2)Stored current (e–)
(e+)

KEKB
SuperKEKB
1.1 A----->
9.4 A !!
1.5 A --> 2.6 A --->
4.1 A !
-> e–: increase beam charge-> e+: flux concentrator (e+ capture effic.)(3) Smaller e+ emittance to fit for IR & C-band module apertures-> e+ damping ring(4) Faster e+/e– mode-switching for Continunous e+/e– Injection-> separated e+/e– beam lines-> non-destructive beam monitoring6Upgrade Scheme e+ energy is boosted by the C-band accelerator modules.
 e+/e- injections are switched by the kicker before the target,e+ and e- go through independent beam lines.
 e+ emittance is reduced with the damping ring.
 both the 2 bunches are used for e+ or e-. (Not for e+ and e–)

7Energy Upgrade• e+ energy gain at KEKB
– max 4.8 GeV = 21 MV/m (S-band module) x 231 m

e+ energy is boosted byC-band accelerator modules.
• e+ energy gain at SuperKEKB–

8.0 GeV ˜ 21 MV/m (S-band modules) x 46 m
+ 42 MV/m (C-band modules) x 185 m

8Linac Accelerator module(From S-band To C-band)
Present S-band accelerator module

Wave guide

Wave guideS-bandSLEDC-bandcompressor

41 MW
4 µs S-band

Pulse
Modulator

New C-band accelerator module

KlystronS-band accelerating sections

Accel. field gradient = 21 MV/m

40 MW
2 µs Pulse

C-bandModul- Klystron
ator

Wave guideC-bandcompressor

40 MW

Pulse C-band
Modul- Kly- 2 µs
stron
ator

C-band accelerating sections

Accel. field gradient = 42 MV/m

9C-band Test Standfor High power test & RF processingof the components
Modulator

RF Window

Accelerating
section
SubBooster
Klystron
High-power
KlystronC-band rf source installed in KEKBlinac (2003 September)10

C-band accel. section installed inKEKB linac (2003 September)

S-band section

C-band section

11

12

C-band R & D items• Klystron -> Toshiba E3746, High Power Test OK• Modulator -> compact (1/3 size), OK except inverter P.S. trouble• Low power RF -> sub-booster OK, solid-state amp.?
• RF pulse compressor -> HPT in July 2004
• Accelerating section -> 1st prototype 41 MV/m,breakdown at input coupler

2nd prototype HPT in July 2004
• Other RF components– RF window– Dummy load– 3-dB hybrid power divider– Wave guide flange– RF gate valve

HPT OKHPT OKHPT OKHPT OK
under consideration

13

Intensity upgrade
Intensity upgrade is essential for higher luminosity efficiency,
even for the continuous injection mode.

• e+ : 0.6 nC x 2 bunches --> 1.2 nC x 2 bunches
by replacing present 2.3 Tesla pulse coilwith 7~10 Tesla flux concentrator
in the e+ capture section
for doubling the capture efficiency• e– : 1.0 nC x 1 bunch --> 2.5 nC x 2 bunches
by increasing the charge from the pre-injector
and using two bunches
With less bunch charge, e– emittance andenergy-spread are smaller.

14

Other R & D items• e+ focusing flux concentrator• beam kicker & e- transport line
• non-destructive beam profile monitor• beam position monitor for 50 Hz readout• fast e-gun grid pulser switching• fast RF phase switching• e+ Damping ring

15Summary• C-band R & D is in progress. High power test of the
prototype C-band accelerator module has been
performed since October 2003. Most of thecomponents are working well.
(Remaining issues)
Breakdown at input coupler, inverter P.S. troubles
RF pulse compressor• Beam instrumentation R & D is in progress. Nondestructive profile monitor and 50 Hz readout ofposition monitor are the main issues.
• Design study of the damping ring is in progress.
Preliminary design is fixed.