BEPC II TIMING SYSTEMBEPC II TIMING SYSTEM

EPICS SeminarEPICS SeminarPresented by Ma zhenhan IHEPPresented by Ma zhenhan IHEP

20.August 200220.August 2002

Functions

1. Providing a series of synchronization signals for accelerator and other related devices.

2. Providing start pulse signals for the storage ring diagnostic system as time references.

Operation Modes1. Colliding mode

a. Single bunch injection

One bunch for one injection.

93 bunches will be reached.

the beam interval is 2.4m.

b. Two bunch injection

Two bunches for one injection, their interval time is 56ns.

93 bunches will be reached.

the beam interval is 2.4m.

Operation Mode

2. SR mode

Single bunch injection

The minimum bunch interval time is 2ns.

Basic parameters and requirements

colliding mode SR mode

Storage ring RF 499.8 MHZ 499.8 MHZ

Storage ring Perimeter 237.193 m 241.396 m

Rotation Frequency 1.264 MHZ 1.242MHZ Storage ring harmonic wave number 396 402

Linac RF 2856MHZ 2856MHZ

Injection repeat Frequency 50 50

Requirement to Timing System The trigger signal of Linac electronic gun must be strictly synchronous with

storage ring high frequency signal.

The jitter of timing system to the bucket reception center will be less than ±70 ps 。

The jitter of trigger signals for Linac klystrons will be less than 5ns.

The storage ring reference signal phase can be adjusted from-180º to+180º.

396 buckets can be selected freely during the colliding mode injection. 402 buckets can be selected freely during the SR mode injection.

In order to ensure that e- and e+ can collide right at the colliding point, the e- timing phase and e+ timing phase can be adjusted.

The bucket selection of timing system and part of parameters can be controlled by IOC through central console. The software will be EPICS.

BEPCII Timing System Design

Reference signals will be considered to adopt phase locked loop technology to depress the time jitter.

Rotation frequencies will be switched according to the operation modes.

The timing system will be considered to compensate for the tiny difference of the two rings.

The timing system will use E/O and O/E and other connectors to eliminate the electromagnet interference.

BEPCII Timing System Block Diagram

BEPCII Timing System Phase Lock Scheme

We select high stable 571.2 MHz synthesizer frequency source to generate the 2856 MHz and 499.8MHZ reference signals.

. The 571.2 MHz reference frequency will be multiplied by 5 to generate the 2856 MHz reference signal .

. The 571.2 MHz synthesizer frequency will generate 499.8MHz reference signal with phase locked technology. We consider 71.4 MHZ common reference frequency as phase detector inputs. 499.8MHz reference frequency is the voltage controlled oscillator output . 71.4 MHZ common reference frequencies are generated from 8 divide 571.2MHz and 7 divide 49

9.8MHz.

BEPCII Timing System Reference Signal Transmission

BEPCII reference signal 499.8 MHz and other fractional frequencies will be used frequently ， so the degree of accuracy needed will be high enough to make sure all the systems can work well.

PSOF can be used to transfer reference signals and trigger pulses.

Some other anti-interference measures will also be adopted to resist the electromagnet interference .

BEPCII Timing System Bucket Selection

The time interval can be set freely. All of the 396 buckets can be selected to

receive the bunches. At most 93 bunches can be injected to the

storage ring according to the BEPCII physical request.

BPECII Timing System Reference Signals’ synchronization

The timing system reference signal should be synchronous with trigger pulse.

RF 499.8 MHz and rotation frequency should be strictly synchronous with repetition frequency of 50HZ.

Besides, the signal transmission method, cable delay and signal attenuation of the synchronizing pulses which are sent to the devices should also be considered.

BEPCII Timing System Time Relationship Graph

Main Devices of BEPCII Timing System

RF Signal Agilent 8648C Frequency Range 9 kHz - 3200 MHz Resolution 0.001 Hz Output Power <= 2500 MHz +13 dBm - -136 dBm <= 4000 MHz +10 dBm - -136 dBm Precision & Stability Normal ： without the time stabilizing plug-in 1E5 aging <±2 ppm/year temp <±1 ppm （ Environment temperature 25±5ºC ） voltage <±0.5 ppm (220V±5%) High stability ： with the time stabilizing plug-in 1E5 aging <±0.1 ppm/year ， <±0.0005 ppm/day temp <±0.01 ppm （ Environment temperature 25±5ºC ） voltage <±0.1 ppm (220V±5%) Spectrum purity Good

BEPCII Timing System Main Equipment Modules

Phase Shifter a. The phase shifter is used to adjust the output phase of the 499.8 MHz to

ensure that the bunch can be injected into the bucket properly. b. The phase shift range should be ±180º ， the phase adjust voltage should

be ±10 V.

Rotation Frequency generator a. There are two rotation frequencies in BEPCII system, so the generator

should generate two frequencies. b. The rotation frequency can be acquired by dividing the RF 499.8 MHz.

BEPCII Timing System Main Equipment Modules

High precision synchronization module a. This module can lock the trigger signal and reference frequencies together. b. The synchronous pulse trigger signals which are generated by this module are: electronic gun trigger, LINAC synchronizing device triggers and storage ring synchronizing device triggers. High precision delay module This module is used in the bucket selection. The module should ado

pt VME plug-in. 499.8 MHz signal is the time input of the module, and the time step is 2ns.

BEPCII Timing System Main Equipment Modules

Optical Fiber Transceivers BEPCII timing system should adopt optical fiber to eliminate

electromagnet interference. Time adjustment modules BEPCII Timing system will use lots of high precision and high stability time

counters. The time resolution should be several ns to several µs. These parameters can be set through computers.

SummarySummary BEPCII timing system can work under the colliding mode and SR

mode ， and can also serves for the two rings structure of BEPCII 。

BEPCII timing system can easily realize the bucket selection. The requirement to the BEPCII timing system is so high that this

timing system will be the best timing system domestically after its establishment.

We still have many problems to be solved in the future.