Progress of the sub-harmonic bunching system (i.e.

upgrading progress of BEPCII present bunching system)

Pei Shilun for the SHBS teamAccelerator center, IHEP

May 10, 2007

Outline

• Beam dynamics simulation and mechanical layout

• Design and study of the two sub-harmonic bunching cavities

• Design and study of the two RF power source

• Construction schedule

Beam dynamics simulation and mechanical layout

(1)

Schematic layout of the bunching system

1.6ns1.6ns

10ps

~9nC(total)

SHB2 Buncher Standard accelerate sectionGun

571.2MHz 2856MHz 2856MHz

e-

Schematic layout of the upgraded pre-injector with 2 SHBs

(Design Scheme)

10nC

SHB1

142.8MHz

Schematic layout of the present pre-injector

(Present Scheme)

e-

1.6ns

PB Buncher Standard accelerate sectionGun

2856MHz 2856MHz 2856MHz

1.6ns 10ps350ps

~7nC(total)

10nC

layout of the bunching system

Keep the location and arrangement

of devices

Keep the arrangement of

devices but move northward for

113.4cm

Remove PB 、 GUF6 and GUF7

Install SHB1 、 SHB2 and 11 new coils

Arrangement of devices for the new sub-harmonic bunching

system

Solenoids

GunBPM&BCT

Vacuumvalve

Vacuumchamber

Profile

BPMSHB1SHB2 Bellow

Bellows

Solenoids SolenoidsSolenoids

Beam pulse structure at the bunching system exit

• Starting with the beam parameters at the gun exit calculated with EGUN, a 150kV/10A/10nC/1.6ns(Bottom width)/0.95ns(FWHM) electron bunch is used as an input of PARMELA to simulate and optimize the beam performance of the primary electron beam at the present and the sub-harmonic bunching system exit.

enlarged

enlarged

Present bunching system

Sub-harmonic bunching system

Emittance variation along the bunching system

Bunching efficiency of the bunching system

(charge within 10ps at the A0 exit)

Present bunching system

Sub-harmonic bunching system

Beam envelope variation along the bunching system

Present bunching system

Sub-harmonic bunching system

Solenoid field strength variation along the bunching

system

Present bunching system

Sub-harmonic bunching system

Physical tolerance of the new sub-harmonic bunching system

Instrument Tolera

nce

Gun beam timing

± 50 ps

Gun high voltage

± 0.4 %

SHB1 phase ± 1.5o

SHB1 power ±1.5%SHB2 phase ± 1.5o

SHB2 power ±1.5%Buncher

phase± 2.0o

A0 phase ± 2.0o

• According to the simulation results with PARMELA, the physical tolerance of the new sub-harmonic bunching system can be obtained. If the physical tolerance shown in the following table cann’t be satisfied, the reduction of the bunching efficiency will be larger than 10%.

Design and study of the two sub-harmonic bunching cavities

(2)

Main parameters of SHB1: • Resonant frequency: 142.8MHz• Tuning range: ~400kHz(length of tuner: 40mm 、 radius of tuner: 10mm)• Q0 value: ~8175• Shunt impedance: ~1.4MOhm• Esurface,max/Egap,max=2.53• When Pin=10kW, Egap,max=2.70MV/m, Esurface,max=6.85

MV/m, Vgap,max=118kV.

Main parameters and structure of SHB1

water channel

Structure of SHB1

SHB1 assembly SHB1 cut view

Tuner cut view Long drift tube assembly

Mechanical design of the SHB1

Monit

or

Coupler

Short drift tubeLong drift tube end-plate

Mechanical design of the SHB1

Bought from HITACHI High-Technologies

Corporation

Main parameters and structure of SHB2

Main parameters of SHB2:• Resonant frequency: 571.2MHz• Tuning range: ~2MHz (length of tuner: 30mm 、 radius of tuner: 8mm)• Q0 value: ~13629• Shunt impedance: ~3.7MOhm• Esurface max/Egap,max=2.44• When Pin=4.5kW, Egap,max=3.68MV/m, Esurface,max=8.98M

V/m, Vgap,max=129kV.

Structure of SHB2

Mechanical design of the SHB2 test cavity

Cold test of the SHB2 test cavity

• Frequency: 571.2MHz (Simulation: 571.2MHz)• Unloaded Q value: >10605 (Simulation: 12370)• Tuning range: 1.60MHz (Simulation: 1.40MHz)• VSWR: <1.05 (Simulation: <1.05)The measurement and the simulation consistent

well!

Design and study of the two RF power source

(3)

Schematic diagram of the RF system for BEPCII Future Linac

Specification of the six reference signal generator

• Input signal: 571.2MHz 、 -8dBm-4dBm• Output signal: f1=571.2MHz 、 f2=142.8MHz 、 f3=2856MH

z 、 f4=17.85MHz 、 f5=71.4MHz 、 f6=499.8MHz• Output power: f1, f2, f3 >13dBm, f4, f5, f6 >10dBm • Input phase noise: >130dBc/Hz (5kHz)• Output phase noise: f1, f2, f4, f5 >110dBc/Hz (5kHz) f3, f6 >105dBc/Hz (5kHz)• Phase shift: <=±2ps/℃• Non-harmonic restrain: >=50dBc• Harmonic restrain: >=25dBc• Output signal isolation: >=20dB• Stably operating temperature: 0~50 Degree

SHB1 solid-state amplifier1) Specification: • Frequency 142.8MHz 5.0MHz• Pulse width 10 to 70s• Repetition 1 to 100Hz• RF input power (cw) 10mW• Phase noise － 110dBc/Hz (1kHz)• RF output power 20kW• Phase variation 1.5 (max. )˚• Phase drift during pulse <1 ˚• Pulse rise/fall time <1s• RF pulse flatness 2 % (max.)• RF power stability 1.5 %2) Operation requirement:• Monitor of the output power .• Monitor of the power supply and power amplifier modules.• VSWR protection when output mismatch occurs.3) Environment requirement:• Air conditioning, < 25℃

SHB2 solid-state amplifier1) Specification: • Frequency 571.2MHz 5.0MHz• Pulse width 10 to 70s• Repetition 1 to 100Hz• RF input power (cw) 10mW• Phase noise － 110dBc/Hz (1kHz)• RF output power 10kW• Phase variation 1.5 (max. )˚• Phase drift during pulse <1 ˚• Pulse rise/fall time <1s• RF pulse flatness 2 % (max.)• RF power stability 1.5 %2) Operation requirement:• Monitor of the output power .• Monitor of the power supply and power amplifier modules.• VSWR protection when output mismatch occurs.3) Environment requirement:• Air conditioning, < 25℃

571.2MHz/1.5kW solid state test module for SHB2

Parameters Measured

Frequency 571.2MHz

Pulse width 10 s

Repetition 400Hz

RF input power 10dBm

Rise time 70.8 ns

Fall time 98.0 ns

RF pulse flatness 0.48%

Output power 1888W

Phase drift during pulse

0.738°

Requirements to the LLRF

• Phase and amplitude stability of the SHB cavities.

• Fast interlock of the SHB cavities and the power amplifiers.

• Frequency tuning of the SHB cavities.• Ethernet interface for remote control.• Fast data acquisition and history

recording.

Construction schedule• 2006.12: Detailed engineering design• 2007.1~07.10: Fabrication of all SHB compo

nents • 2007.11~07.12: Acceptance test • 2008.1~08.5: High power test in laboratory• 2008.6~08.8: Installation and commissioni

ng• 2008.9: Operation in Linac

(4)

Summary(1)• Established in the future development o

f BEPCII Linac, the optimized physical design of BEPCII future sub-harmonic bunching system and the optimized structure of the two SHBs are developed.

• Design, fabrication and cold test of the SHB2 test cavity has been performed, the test results is consistent with the simulation.

• Study of the two RF power source have been done. One test module of the solid state amplifier has been designed and tested with satisfied results.

Thank the colleagues from KEKB-Linac and SLAC for their help in the past sever

al years.

Summary(2)• Recently, the upgrading of BEPCII present bunc

hing system to sub-harmonic bunching system has been approved by IHEP’s experts and directors. The detailed design scheme has been decided. The construction will start in this year, correspondingly, the commissioning will be started in summer of 2008 according to the construction plan.

The revolution is not success, everybody in the SHBS team should

continue to work hard.