KEKB Review, 2010 February 16

Injector Upgrade Overview&Positron Source
KAMITANI Takuya
e+/e- Injector Linac group, KEK1

2(1) Injector Upgade Overview

SuperKEKB Injector Linac Parameters
KEKB (e+/e-)achieved

SuperKEKB (e+/e-)
required

beam energy

3.5 GeV / 8.0 GeV

4.0 GeV / 7.0 GeV

stored current

1600 mA / 1200 mA

3600 mA / 2620 mA

beam lifetime

150 min / 200 min

10 min / 10 min

bunch charge

primary e–  e+

e– 

primary e–  e+

e– 

10 -> 1.0 nC / 1.0 nC

10 -> 4.0 nC / 5.0 nC

2/22/2

beam emittance ()[1]

2100 μm / 300 μm

10 μm / 20 μm

energy spread E/E

0.125 % / 0.05 %0.07 % / 0.08 %bunch length z

2.6 mm / 1.3 mm

0.5* mm / 1.3 mm# of bunches*(assuming bunch compression after DR)3

Injector Upgrade Strategy(e-)
 High intensity
 Low emittancePhoto-cathodeRF gunTalk by T. Sugimura(e+)
 High intensity

New matching device &L-band capture section
Talk by T. Kamitani

 Low emittanceDamping Ring
Talk by M. Kikuchi &by N. Iida

45KEKB Injectore–BA
A1 gun1.7 GeV@J-arc1C

Key Features for Simultaneous Injection
pulse-by-pulse beam switching for HER, LER & PF
target bypass bump orbit (5 mm height)
compatible optical setting for different beam energies
switching of RF phases, ACC/STDBY timings &gun parametersindependent orbit control with pulse steerings

target bypass
bump orbit

32

4

5C-bandmodule

3T gunmoved from CTfor PF
2.5 GeV
0.1nC x 1for HER
8.0 GeV
1nC x 2for AR
3.0 GeV
0.1nC x 1e+
A1 gunBCA
1

4.0 GeV
10nC x 2

23e+ target &S-band capture section

45for LER
3.5 GeV
1nC x 2
ECS (Energy-spreadCompression System)6

SuperKEKB Injectore–B

new RF gun
for low emittancee– beam for HER

Afor PF
2.5 GeV
0.1nC x 1

RF gunemittance growth ?
in e– / e+ beams

1.7 GeV@J-arc1C

2target bypass
bump orbite+35e- bypass line for
DC separation bend

present A1 gunfor 10nC e– beamfor e+ production

1.0 GeV@DRA1 gunB

4for HER
7.0 GeV
5nC x 2for ARe– or e+ ?

Damping ringfor rad. coolingof e+ beam

Atarget moved to 1-5 for e+ energy margin
new matching dev. & L-band capt. section
for e+ intensity upgrade

1C

3.5 GeV
10nC x 22BCS

e+ target, matching dev. &L-band capture section

ECS

3

2nd C-band module added
for e+ energy margin

4C-bandmodule x 2

5for LER
4.0 GeV
4nC x 2

ECS (Energy-spreadCompression System)

7(2) Positron Source Upgade

Positron capture section upgrade
present capt. section

L-band capt. section

accelerating structures

1m x 2 + 2m x 2 (=6m)

2m x 2 + 2m x 4 (=12m)

RF frequency

2856 MHz1298 MHz

aperture of the structures

20 mm in diameter

30 mm in diameter

accel. field gradient14.0 ~ 13.2 MV/m

10.0 MV/m

accel. phase-30 deg-30 degsolenoid field （strong）

2.0 T x 45 mm QWT

6.0 T x 220 mm AMD

solenoid field （weak）

0.4 T x 7.9 m

0.4 T x 13.1 m

energy after capt. sec.

~ 80 MeV~ 120 MeV

(=10.5cm)(=23.1cm)

Increase e+ capture efficiency by enlarging these acceptances !

 longitudinal acceptance by longer wave length of L-band RF transverse acceptance by larger aperture of L-band structure
 energy acceptance by adiabatic matching device=> Flux concentrator or SuperConducting solenoid

Qe+ = 1 nC

4 nC

prelim. simulation result by N. Iidasuggests
Qe+ ~ 8 nC @ DR

8

flux concentrator (FLC) R&D
 R&D in collaboration with BINP prototype magnet, vacuum

chamber & power supply
fabricated at BINP
 operation test at BINP
15x106 pulses ~ 1 week
No mechanical failure !!

9

FLC operation test at KEK prototype magnet, vacuum

chamber & power supply
are sent to KEK in Apr. 2010
 stand-alone operation test &field distribution measurementat KEKB linac klystron gallery
in May-June 2010
 installation of FLC magnet
into KEKB linac e+ source
in Aug. 2010
 operation testfrom Sep. 2010 to Mar. 2011
mechanical stability will be tested ande+ yield performance will be studied
with real KEKB linac 10 nC e– beam 1011

Superconducting (SC) solenoid R&DCurrentdensityJ (kA/mm2)

 SC solenoid can yield highmagnetic field as 6 Tesla.
 Superconducting state can be
maintained only if J, B, T are
below quench limit curve.
 Can SC solenoid survive under
heating by intense radiationfrom e+ production target ?
 Is SC solenoid sensitive to
instantaneous heating bypulsed linac beam ? (10 ps/20 ms)
 Which kind of SC wires to be
used ?
Nb3Sn
 high Tc material ? (Bi, YBCO)

Magneticfield
B (T)Temperature
T (K) NbTi,trial designSC solenoid beam irradiation test12

 a sample SC solenoid isirradiated by shower fromtungsuten radiator at KEKB
linac test-beam line.
 quench limit property is studied.

SC solenoid
inside Liq. Hecryostat

8 GeV
e– beamtungustenradiator
lead shield
to control
rad. intensitySC solenoid beam test result

13

observed quench limit seems to beconsistent with ordinary critical limit.
no sensitivity to pulsed heating !!

More detailed beam studies are necessary with more practical prototypesolenoid and with more practical beam line configuration. They will be
performed in 2010, 2011. 2nd beam test is planned in 2010 March.

Comparison of matching devices(merits & demerits)

air-core coilflux concentrat.

SC solenoid

field strength

2.3 T

6 ~ 10 T

6T

field length

45 mm

90 mm

> 220 mmfield shapedifficult to makelong slope

defined byconductor shapeflexible in design

aperture diameter

22 mm

8 mm

> 30 mmpower supply

high-power pulse
modulator

high power pulse
modulator

low-power DC
power supply

vibration

large

large

none

transvers field

small

large

small

target in mag. fieldout of field peakout of field peakat field peakcomponent in vacuumnone

magnet & coolingnone

quenching

none

none

possible

top meritworking now

high field strength

adiabatic field

top demerit

low & short fielde+ bypass line

quenching

14

15

L-band capture section layout
present layout around e+ targetEach block is an accelerator module.

target








 











 

solenoid focusing

layout with L-band capt. section (FLC case) target moved for DR inj. energy margin
L-band modules

 e+ bypass line, separation pulse bend,e+/e– merging DC bend are necessary DRS-band modules





 or
moved for DR inj. energy marginlayout with L-band capt. section (SCS case) target–
e bypass through target hole

DRL-band modules




 









 

L-band component R&D
fL-band = 2856 [MHz] x (5/11) = 1298 [MHz]
 klystron developping 40 MW klystron (30 MW in operation), 4.0 μs width 1st klystron will be completed in May 2010 and tested in a test-stand pulse modulator with suitable design of the klystron, S-band modulator can be usedfor L-band without modification

 accelerating structure breakdown issue

spiralling field emission in solenoidal fieldshower particle bombardment
 travelling wave or standing wave structure ?
shorter RF pulse width
higher accelerating field 1st TW structure (2m long, 10 MV/m acc. field) will be completed inFeb. 2011 and tested in a test-stand

16

17

L-band teststand1) klystron + accel. structure
L-bandKlystronhigh power test
PulseModulator2) operation with DC solenoid

field to study breakdowns
by spiralling field-emission3) operation with target &matching device to study
breakdowns by radiationfrom targete– beam

1st stage high power test
will begin in Apr. 2011.

wave guide
temporarytargetaccel. structures

temporary
matchingdevice

DC solenoid

dummy
load

in Linac tunnel@1-5 unit18(3) Injector Upgade Schedule

19

Injector upgrade schedule
FY2009FY2010Main Ring *FY2011FY2012FY2013

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