A New Timing System for NSRL
Pengjie Zhang Qi An Shubin Liu Yanfang Wang
Fast Electronics Lab, Modern Physics Dept. University of Science and Technology of China(Mailbox 4, HeFei, AnHui, 230027 , P. R. China)
Abstract
The timing system is an important part of the NSRL
control system. Its main function is to provide
synchronization trigger signals for the LINAC (whichincludes the Electron-Gun, the Microwave Excitor and six
Modulators), the Switch Magnet, the Septum, the Kicker
and the beam diagnosis system. The former Timing
System[1] only allowed injection in full bunch mode, thenew Timing systems provide more precise and stable
trigger signals, it will allow injection in both full bunchmode and single bunch mode.
The New Timing System consists of two parts: FastTiming System and Slow Timing System. The Fast Timing
System provides trigger signals for the Electron-Gun and
the Kicker, the jitters of these trigger signals are measured
to be less than 100pS (Sigma < 30pS) [2] with respect tothe storage ring RF. The time delays of these signals can be
programmed with a step of 50pS. The fast Timing System
also provides period pre-trigger signal for LINAC andinjection. The Slow Timing System provides trigger signals
for other devices¡ £The timing delay of each trigger signal
can be adjusted in the full range of its period.
1 Introduction
The NSRL synchrotron radiation facility has two main
components: an 800MeV storage ring and a 200MeV linear
accelerator (LINAC). The LINAC and injection devices areoperated in pulsed mode. The maximum repetition rate of
the LINAC is 100Hz, and minimum injection period is 1s.
The LINAC and injection system are composed of varioustransient devices, such as the Electron Gun, Modulators
and Kickers, etc. At the end of the LINAC, a switch
magnet is installed. In each injection cycle, the magnet
delivers one beam bunch to the injection system andseveral bunches to beam analyzer for energy measurement
purpose. Injection into the storage ring is accomplished via
a septum magnet and three fast Kickers. The function of
the Timing System is to provide synchronization trigger
signals for the LINAC, the switch magnet and the injection
system, so that a bunch will be fully accelerated in theLINAC, transported to the injection point at the right timeand injected into the storage properly.
In full bunches injection mode, the pulse width of theLINAC output beam is 0.2-1.0µS, after fully accelerated in
LINAC, it is transported to the injection point, and isinjected into the ring sequentially. The bunches in thestorage ring have a revolution period of 0.22µS, if the pulse
width is 1.0µS, one ″Multi-Turn Injection″ will contain
about four turns. The Electrons will be distributed into 45
buckets. In single bunch injection mode, the LINAC output
beam duration is about 2 - 3nS. The successive injection

beams will be filled in the same bucket, so the trigger
signals of the electron gun and kickers must be
synchronized to the Radio Frequency (RF) of the storage
ring, and the injection period must be integral times of therevolution period of the electron in the Storage Ring. In
single bunch injection mode, the timing system must use
the RF signal as the time reference (Clock). While in thefull bunch mode, it is not a necessary. In the full bunchesmode, the electron beam is much longer than single bunchmode, so the timing requirements are much lower than insingle bunch mode. The new Timing system will provide
more precision and stable trigger signals, and will allow thefacility to inject both full bunches mode and single bunchmode.
2 Timing requirements
Table 1 shows the timing specification of the trigger
signals in the New Timing System.
According to the timing resolution, the trigger signals
can be classified into three catalogs. The trigger signals forE-GUN(I) and the Kicker are in the first catalog, and theirresolutions are less than 1nS. We call them ″Fast Timing
Signals″. The second catalog includes the trigger signals
for E-GUN(II), six Modulator, Micro-Wave Excitor andSwitch Magnet synchronization. The resolution of thesesignals should be less than 0.1µS, and their repetition rateequal to the LINAC’s. The rest trigger signals areconcerned with injection, their timing resolution should beless than 1.0µS, and their period is the same as the injection
cycle. Trigger signals in the second and the third catalogs
are entitled ″Slow Timing Signals.″
E-GUN(I) and E-GUN(II) are the trigger signals of theelectron gun, E-GUN(I) is used in the single bunch
injection mode, while E-GUN(II) in the full bunch mode.
In the full bunch mode, the beam duration is the same as
the width of the trigger signal, so the pulse width of the EGUN(II) can be adjusted from 0.1µS to 10 µS with a stepof 0.1µS. In the single bunch mode, the jitters of the EGUN(I) and kicker should be less than 500pS with respect
to the storage ring RF, otherwise the electron from theLINAC may enter the buckets adjacent to the ″mainbunch″, and form ″Satellite bunches″.
Because of the non-uniform transmission delay andinternal delay of the each device, the trigger signal shouldhave sufficient range and resolution to satisfy different
cases.
3 System description
The new timing system consists of two parts: fast timing
system and slow timing system. Figure 1 is the schematic
Diagram of the new timing system.

Table 1 Timing specifications
DevicePeriodRange

Resolution

Rise time

Jitters

Pulse Width

E-GUN(I)2/1/0.2…
0.02 /0.01S

100mS

100pS
/ 5ns

< 500pS< 500pS

2uS

Kicker

200mS∼2S

2S

100pS / 5nS< 500pS< 500pS

4uS

Septum

200mS∼2S

2S< 1.0uS

50nS5nS

4uS

S.M. RESET

200mS∼2S

2S< 1.0uS

50nS

5nS

0.5S

Beam Analyzer

200mS∼2S2S< 1.0uS

50nS

5nS

4uS

E-GUN(II)10∼100mS

100mS< 0.1uS

50nS

5nS

0.1∼10uS

Modulator(6)Micro Wave
S.M. SYN

10∼100mS

100mS< 0.1uS

50nS

5nS

4uS

3.1 Fast timing system

3.2 Slow timing system

The fast timing system provides the trigger signal forelectron gun (single bunch mode: E_GUN(I)) and thekicker, it also generates the pre-trigger signal for
LINAC(L-S) and repeats signal for injection(K-S). The fasttiming system consists of Clock Driver, Repeat Signals andlow frequency Clock Generator and three ″Fast TimingSignals″ generators.
Figure 2 is the schematic layout of the ″Repeat Signals& Clock Generator″. Repeat signals are the pre-trigger for
the LINAC(L-S) and the injection(K-S).

Slow Timing System generate all the ″Slow timingsignals″. It has two parts: LINAC Timing Subsystem andInjection Timing Subsystem. LINAC Timing Subsystem isinstalled in the LINAC control room, as shown in figure 1(which is in the dotted line rectangle). It provides trigger
signal for electron gun (E-GUN(II)), six modulators, micro
wave excitor, and one spare signal. The Injection Timing
Subsystem and the fast Timing System are installed in thecentral control room. The clock (CLK10) and the LINAC
repeat signal(L-S) are transmitted differentially from
central control room to LINAC control room with twistedpairs. There is a local OSC in the LINAC Timing
Subsystem, which make it possible to run LINAC
separately.
The slow trigger signals are transmitted by twisted pairs.
At the end of each transmission line, an optic isolator isinstalled to protect the timing system from EM influence.
The slow timing system is designed mainly with Field
Programmable Gate Array (FPGA).

RF204MHzClockDriverAC - LINE
Divideby 45

Fc=4.53MHz
AC - SYN
CLK10Clock
EnableDivideby N
Divideby M

SampleGate
CLK11L-S
1/M

K-S

To Precision Delay Moduler

Figure2: schematic of the ″Repeat Signal & Clock Gen.″First, the revolution clock is obtained by dividing thering RF by the ring harmonics (45), then the revolution
clock samples the AC-SYN, and get the LINAC pre-trigger
signal L-S. The injection repetition period is M times of theLINAC period. Pick one L-S pulse every M cycle of L-Swill get K-S. The low frequency clocks (Clk10, Clk11),
which will be used in the ″Slow Timing system″, are also
generated by dividing the ring RF.
The ″Precision delay module″ generates the ″Fast timingsignal″. It has a very fast binary counter, whose frequency
is 204MHz (Ring RF), and a programmable delay
generator with a resolution of 50pS. There are three Fast
Timing Signals, one for kicker and one for E-GUN(I), theother one is spare. They are transmitted by optic fiber.
The fast timing system is designed with ECL(orECLinPS) family devices.

3.3 Control of timing system
Two PCs have been introduced to control the Timing
System. One is installed in the central control room, theother in the LINAC control room. They are connected
through a serial link. The operator in the central control
room can control the whole Timing System. The Timing
System can link to the real-time net when upgrading theNSRL Control System. Software is designed withLabVIEW for Windows, and it has a friendly interface. All
the timing parameters can be set and recorded. The timingsystem is packed in three cases, one case is installed in theLINAC control room and the other two in central controlroom. A PC-ISA bus interface card is plug in the one of theISA-bus slots, and it is connected to the timing circuit witha ribbon cable. The ribbon cable is shield with copper net
to protest EM noise.
4 System performance
After the New Timing System was set up, performance
had been tested. The jitters of ″Fast Trigger Signal″ aremeasured to be less than 100pS (and RMS < 30pS) withrespect to the storage ring RF, and its resolution is 50pS,
much better than the requirements (shown in table 1). The
jitters of the ″Slow Trigger Signal″ are less than 1nS withrespect to Electron-Gun trigger.

and Prof. S.Q. Liu for their help.
Reference[1] C.Y Yao et al., Proc. Intl. Conf. Synchrotron Radiation
Applications, Hefei, China, 1989. P241
[2] P.J Zhang, ″New Timing System Test Report″, Modern
Physics Dept. Univ. of Sci. & Tech. of China, 1997.

Acknowledgments
We would like to thank Prof. G.C Wang, Prof. Y.J. PeiRing
Master Clock PowerRF System
Ring RF Splitter

Clock Enable

Level
Shifter

Fast Timing System
Clock Driver
Precision
Delay Module

CLK0: 204MHZ

E/O

E-GUN(I)
KickerAC-LINE

Repeat Signal& Clock Gen.

CLK10 / L-S

Spare

L-S/K-SBeam Analyzer

Variable Delay
Modules

ECL-TTL

Septem¡£¡£¡£ Modulator

E/O(Six)
Micro Wave

E-GUN(II)
LINAC Subsystem

Spare

S.M Reset

Variable Delay
Modules

Slow Timing System

Figure 1: Schematic Diagram of the New Timing System

S.M. SYN