Transcript BEPC2 timing system - KEK:Accelerator Laboratory

BEPC II TIMING SYSTEM
EPICS Seminar
Presented by Ma zhenhan IHEP
20.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 Modes
1.
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
Storage ring RF
499.8 MHZ
Storage ring Perimeter
237.193 m
Rotation Frequency
1.264 MHZ
Storage ring harmonic
wave number
396
Linac RF
2856MHZ
Injection repeat Frequency
50
SR mode
499.8 MHZ
241.396 m
1.242MHZ
402
2856MHZ
50
Requirement to Timing System

The trigger signal of Linac electronic gun must be strictly synchronous with
storage ring high frequency signal.
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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.
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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
499.8MHz.
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

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RF Signal
Frequency Range
Resolution
Output Power

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

Agilent 8648C
9 kHz - 3200 MHz
0.001 Hz
<= 2500 MHz
+13 dBm - -136 dBm
<= 4000 MHz
+10 dBm - -136 dBm
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
adopt 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


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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.
Summary



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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.