PF/KEKB  

2018/10/18
 KEKBA1 KEKBO69A-R1)(O27AT   May #!!!"##f 254



400

SHB1 of 114MHz
SHB1 Cavity

Input coupler

TunerMonitor Coupler

Beam induced field in SHB1
114MHz RF & induced fields by a single pulse beam of 10nC are shown(1) just after the beam passed(2) after 96.2ns.
Field attenuation is not sufficientSHB2 of 571MHz

SHB2 Cavity

Monitor Coupler

Input couplerPrebuncher and buncher of pre-injector APrebuncherBuncher
541174.725

160.357

Beam

209.357

49

PALMERA

 

10 nC,1 ns

Simulation by PARMELA

Gun200 kV

SHB476 MHz

PB12856 MHz

PB22856 MHz

Buncher

2856 MHz2.5 MeV

6 ps

PARMELA example at the buncher exitAn example of PARMELASHBPB1PB2Buncher

6 MV/m123 4 5 67

200kV, 3A, 1 ns
SHB

12345675 MV/m

6 MV/mAn example of PARMELA
7 MV/m200 kV, 3A, 2 ns
SHB5 MV/m

6 MV/m12 MV/m

1234567

An example of PARMELA15A, 1nsSHB

1

23

4

5

676 MV/m

7 MV/mAn example of PARMELA8 MV/m  Bunch structure measured with a streak camera

10 nC beamSingle bunch procedure
1. Turn off SHB1&2 power source, or delay rf
pulse timings not to affect the beam.
2. Adjust the beam timing by changing thetime delay of a grid pulser so that thecentral bunch peak becomes maximum.
3. Turn on only the SHB1 power source, orreturn the rf timing for modulating thebeam.
4. Adjust the SHB1-rf phase so that thecenter bunch becomes the highest peakand maximum.
5. Turn on the SHB2-rf power source, orreturn the rf timing for modulating thebeam.
6. Adjust the SHB1-rf phase so that thecenter bunch becomes maximum andsatellite bunches become minimum.

Positron Linac/BT Orbit

positron production target
The 10-nC electron/positron beams accelerated in the KEKBlinac

RF-gunKEKBA1 unit
Bunching SystemA1

OTR

SKB 

RF-GUNA1 unit

Bunching System  

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*RF Gun*740-49(&'"*, )%"SKB*8/.3@)$+#1<=9(A1;645* *.:=2

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Bunching System ( Buncher,Prebuncher,SHB2,SHB1

A1;645* *.:=2>!

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RF-GUNAT unit layoutA1 unit
Bunching System

RF-GUNBeam 

A1 unitPB+B+Acc1,2 power-phase tuningKlystron
A1-A

Phase
Shifter

50% - 50%
Power Divider

VariablePower Divider&Phase Shifter

50% - 50%
Power Divider

AC_AT_2

AC_AT_1

Buncher

PhaseShifter
PBKEK 

Tolerance of the Pre-injector ParameterInstruments

Tolerance range

Gun beam timing

45 psGun high voltage

0.38 %SHB1phase1.1 deg

SHB2 phase1.3 deg

Buncher phase1.7 deg The e+/e- beam is a single bunch of which width in 10ps (FWHM).
 The each tolerance range is defined so that when each instrumentchanges the transmission rate of the primary electron beam intensity
maintains more than 90% of the maximum value at the positron
production target.

•Element•Repetition or•Frequency••period•Voltage or•Power•Grid pulser•1~50 Hz•-•450~800 V•Gun•50 Hz•-•200 kV•25th SHB1 (standing wave)•114 MHz•8.75 ns

•11 kW•5th SHB2 (standing wave)•571 MHz•1.75 ns

•7 kW

•Prebuncher (travelling wave)•2856 MHz

•350 ps•1 MW•Buncher (travelling wave)•2856 MHz

•350 ps•23 MW•Accelerating sections (travelling wave)•2856 MHz

•350 ps•12 MW x 2•Common frequency of linac/KEKB rings•10.385 MHz•96.289 ns•-

Gun parameters

Beam current

0 ~ 15 A

Heater power

40 W

Grid pulse-300 ~ -700 V

Cathodetemperature

950CBias voltage+150 ~ +300 VAccelerationvoltage

200 kV

Grid/cathodedistance

180 µmGun pulse
duration

4 µs

Beam duration

1 ns

Residual gas
pressureBeam time jitter

8 ps

ML magnetic field

1 x 10-7 Pa~ 900 G

Design values of bunching system A
Prebuncher

Constant impedance Drift space
Buncher

42.27 mmMax. field

2.0 MV/mfield strength

15 MV/mshunt impedance

14.97 MM/m

maxi. inpu power

13 Mw

group velocity/c

0.0494

cavity number

attenuation
coefficient

0.0597 Neper/mbuncher section
normal section

5 + coupler
28 + coupler

maxi. Input power

2 MWcavity size D

31.49~34.99 mm

cavity number

3 + couplers

2a22.44~19.43 mm

cavity size D

24.318 mm

2b82.53~81.75 mm

2a36.89 mm

2b90.075 mm

Kenteck

Trigger system
Trigger

E/
OO/
E

AMP

TD4W
( 2ns-stepTime Delay+571MHz

Units )

()Time delay
TTL

Beam inhibit

E/
OO/
E

NIM

Double pulse system
Controler
1

Controler
2

Pulser1
Double pulseCombiner

Pulser2
CathodeGrid()96ns

Double pulse generation
Pulser 1

Attenuator
4 Combiners

DC cutCathode GridBeamPulser 2

Choke coil

Bius voltage

Combine Method of Two Independent Pulses(1) An individual pulser produces a pulse.
(2) Two independent pulses are combined by rf combiners
in order to isolate each other.
(3) 4 combiners are used to reduce source impedance2 grid pulsers & socket  First bunch

FWHM 15ps

  

Second bunch







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4.4W
KL-AT

#34:., ZU[^aW615 HCEX\_V3.3W

1i: 15
Kly 250kV, 1.0kW

1i: 12Gun 200kV, 1.8kW

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Pulse transformer and oil tank of gun A
Ceramic
bushingResistors
Oil tank

C-divider
Pulse transformer

Pulse transeformer & dumy loadElectron gun and collimator

Electron gun
Collimator holes (2,4,6mmf)

Collimator   

Relationship between Beam Emittanceand Collimator Size

#$

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 " !  " ! ! !

""



Relationship between Emittance and Beam Charge




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

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

Two-bunch beam generation for KEKB••

Two-bunch beams have been required to reduce injection times intoKEKB rings.
Especially for the LER it is being inevitable to increase positron
intensity as the stored beam increases. Two-bunch beam accelerationis one of the methods to meet the requirement. In order to accelerate
and accumulate the beams successfully, it is at least necessary tosatisfy the following conditions: 1) each bunch length should be as
short as the present single bunch, that is less than 10 ps, and 2) theirtime interval should be 97.29 ns that is a period of the common
operation frequency between the linac and KEKB rings. Wake field
effects are strong for high intensity beams. In normal acceleration
sections beam energy of each bunch is thought to be controllable bymeans of changing acceleration timing with respect to RF pulses. Inthe bunching section, however, this technique is not useful. To obtain
independent operation freedom we developed a system that produces
a two-pulse beam from an electron gun each of which intensity andtiming are independently changeable. Beam test results are presented
as well as the system configuration and performance.

Magnetic lens and focusing coils



571MHz & induced fieldsCorrelation between beam position andY (mm)gun-accelerating voltage

Two bunch beam orbit 196.2
nsSchematic layout of the pre-injector AOrbits and Current in KEKB Linac & BT @10nC

positron production target

The 10-nC electron/positron beams accelerated in the KEKB linac

Tolerance for phases @ 10nC beam

SHB1 dq1.4

SHB2 dq1.5

Buncher dq2.0

The each tolerance range is definedso that when each instrument changes
the transmission rate of the primaryelectron beam intensity maintains morethan 90% of the maximum value at thepositron production target.

Summary
Instruments

Tolerance
range

Measurement
accuracy

Stability*Digital feedbackGun beamtiming

45 ps

5 ps

20 



Gun highvoltage

0.38 %

0.02 %

0.1 

SHB1 phase1.1 deg

0.05 deg

0.5 deg-

SHB2 phase1.3 deg

0.2 deg

1.0 deg-Buncher phase1.7 deg-

 1.0 deg-

* Long term stability of normal status.

This system is doing on the reference of a Buncher entrance RF phase.
Three kinds of RF phases that were directly associated to the electron
beam are being measured directly with high accuracy.
We are able to discover it right away if there is abnormality in thesemeasurement data quantity.
We aim for a more stable beam from now on, and be thinking digital
feed back of SHB1/2 by using the measured value of this system.

Tolerance Measurement @1999/06/18

A1 RF-phase dependence @10nC

SHB1 RF-phase dependence @8nC,
June/14/1999

SHB1 RF-phase dependence @6nC

SHB1 RF-phase dependence @8nC

SHB2 RF-phase dependence @8nC

SHB2 RF-phase dependence @6, 8nC

Controller of the gun modulator A

Acceleration voltage

200 kV

Pulse width

4 µs

Pulse repetition rate50 pps

Gun modulator circuit40 H

15 H

0.35 A

0.35 A

L158 kVA
F-175

0.35 A
6 µF

10~380V

C1517 kV
1300 A
4.0 µsMonitor and feedback systems of gun
4352Buncher

1

1

20.8
4.0

3 Buncher & gun beam monitor system(10nC beam @bucher)

4PFN

Room Temperature(Continuous regulator)

History of Gun Room Temperature

Switching regulator
0.5deg60 hours       

Gun HV measurement and feedback

0.25% (DVpeak-peak in a short time)

5 minutes

PFN voltage change of the Gun pulser A0.1 % (DVpeak-peak in a long time)
14 hour

5 days  PFN of gun modulators

Capacity

14.6 nF

Section No. 3 x 5Coil turn No.

10

Pulse transformer and oil tank of gun A

Ceramic bushing

C-divider
Pulse transformer

Resistors Oil tank

Step up ratio

1:12

Secondary impedance
1.8 kM
Load resistancePower consumption

1.82 kM
5 kW

Pulse transeformer & dumy load

SHB1 of 114MHz

          

SHB2 of 571MHz

Quantities of Measurement
 Grid pulse amplitude and gun beam amplitude Grid pulse timing and gun beam timing Buncher beam timing vs. 2856MHz SHB1/SHB2/571MHz phase vs. 2856MHz
 Gun pulser EPFN monitor output voltage
 Output signal for e+ pulse coil power supply Gun room temperatureSummary
Instruments

Tolerance
range

Measurement
accuracy

Stability*

Digital feedback

Gun beamtiming

45 ps

5 ps20 

Gun highvoltage

0.38 %

0.02 %0.1 

SHB1 phase1.1 deg

0.05 deg

0.5 deg-SHB2 phase1.3 deg

0.2 deg

1.0 deg-Buncherphase1.7 deg-

 1.0 deg-

* Long term stability of normal status.

This system is doing on the reference of a Buncher entrance RF phase.
Three kinds of RF phases that were directly associated to the electron
beam are being measured directly with high accuracy.
We are able to discover it right away if there is abnormality in thesemeasurement data quantity.
We aim for a more stable beam from now on, and be thinking digital
feed back of SHB1/2 by using the measured value of this system.

400f4 25

Gun control panel 1

Gun control panels 2

Gun HV measurement
TD4 delay 2-ns stepStructure of the positron production target
W 4h x 20w x 15t

In or outCu
Thermo coupler

Thermo coupler

ScreenScreenHistory driving pulse for e+ Focusing Pulse Coil
Pulse width

Amplitude@ON/OFF

Fall time
Rise time
Digital Oscilloscope
TDS3032 (Tektronix)

58days    

Two-bunch beam generation for KEKB••

Two-bunch beams have been required to reduce injection times into
KEKB rings.
Especially for the LER it is being inevitable to increase positron
intensity as the stored beam increases. Two-bunch beam accelerationis one of the methods to meet the requirement. In order to accelerate
and accumulate the beams successfully, it is at least necessary tosatisfy the following conditions: 1) each bunch length should be as
short as the present single bunch, that is less than 10 ps, and 2) theirtime interval should be 97.29 ns that is a period of the common
operation frequency between the linac and KEKB rings. Wake field
effects are strong for high intensity beams. In normal acceleration
sections beam energy of each bunch is thought to be controllable bymeans of changing acceleration timing with respect to RF pulses. In
the bunching section, however, this technique is not useful. To obtain
independent operation freedom we developed a system that produces
a two-pulse beam from an electron gun each of which intensity andtiming are independently changeable. Beam test results are presented
as well as the system configuration and performance.