EPICS 2008, ShanghaiBEPCII Timing System1 BEPC-II Event Timing System Ge LEI for BEPC-II timing team Institute of High Energy Physics, Beijing Mar. 2008

EPICS 2008, Shanghai BEPCII Timing System 1

BEPC-II Event Timing System

Ge LEI

for BEPC-II timing team

Institute of High Energy Physics, Beijing

Mar. 2008


Brief Introduction to BEPC-IIBrief Introduction to BEPC-II

BEPC--Constructed in 1984 –1988; Operation 1988-2005

Single Ring collider, Beam energy: 1 – 2.8 GeV

Physics Run ： Lum. 1031cm-2s-1 @ 1.89GeV, 5 month/year

Syn. Rad. Run ： 140mA @ 2.2 GeV, 3 month/year


Design Goals of BEPCIIDesign Goals of BEPCII

The BEPCII continues to serve the purposes of both high energy physics experiments and synchrotron radiation applications.


SR mode: outer ring (BSR)

Col. mode: e+ ring (BPR)

e- ring (BER)

Commissioning

Phase 1 ： Backup Scheme

Phase 2 ： With SCQ

Phase 3 ： With detector

e+e

SR


-Jan. 31 Beam collision tuning with SCQ to improve the luminosity & minimize the background

Feb. 26 -- One month of SR operation

Mar. 26 Shutdown for detector to move in

May 14 Start collision tuning with detector on line

Test run of HEP experiment

Dec. 2008 Lum. (1.0~3.0) 1032cm-2s-1

BEPCII Schedule of CommissioningBEPCII Schedule of Commissioning


BEPC-II timing system,an event timing system


BEPC-II timing related Parameters

colliding mode SR mode

ring circumference 237.531m 241.129m

energy 1.89GeV 2.5GeV

RF frequency 499.8MHz

harmonic number 396 402

revolution frequency 1.262MHz 1.243MHz

linac repetition rate 5, 12.5, 25, 50Hz

linac RF frequence 2856MHz


BEPC-II timing system requirements

delay resolution RMS jitter in respect to RF Clock

Injection kickers 2ns < 100 ps

e-Gun 10ps < 35ps

other triggers 10ns <200ps

clock <100ps


• Black boxes are timing stations

• Blue lines: timing multi-mode fiber cables

• Red lines: 499.8MHz reference distribution.

• Greed line: 10MHz synchronizing cable from linac master osc. to ring RF osc.

BEPCII timing system layout

master

BCM,Libera TB-BI

ModulatorsBI

eGun

2856MHz

Feedback

BES

e- SR

e+ SR

e+Kicker

e-Kicker

RF

RF


BEPCII timing

structure

EV

G

Fan

out

499.

8MH

z 50

Hz

TT

L

Fan

out

Fan

out

Fan

out

EV

R

330m fiber cable

EVR330m fiber cable

EVREVR

EVR

120m fiber cable EVR

EVR

EVR

EVR

EVR

16 Modulaters

BT BPM

feedback

e- camera

BCM

e+ camera

120m fiber cable

EVR

EVR

EVR

EVR

EVR BT BCT

Fast bucket select

e- Kickers

BES

e+Kickers

…...

E-Gun

AmplifierPSK

Gun PSe+ PS

Linac BI

GU

N-T

X

EVRLibera BPM

120m fiber cable


• 2 EVGs, 18 EVRs

• 13 VME crates and controllers,

• 2 levels of fanout, 5 Fout-7 modules in total.

• GUN-TX and Gun-Rx for e-gun pulser timing

• 4 TD-4Vs for Kickers

• 18 sets of home-made E/O and O/E for linac

BEPCII timing system hardware


What are special in BEPCII event timing

• Hardware developed– 18 sets of optical transmitting/receiving boards, for gun

power supply, positron source, and 16 modulators (LI Gang, LE Qi)

– Gun-Rx module modified to generate NIM outputs directly (WANG Lin)

– Revolution frequency

• Software

– Make every bucket selectable

– Fast bucket selection: a dedicated record support and device support developed for fast bucket selection


To select any bucket

• The event clock is set to 499.8MHz/5. – Reason: In EVG-200, the event clock is generated from RF

divided by 4,5,6,8,10 and 12, among which only 5 is a prime numver.

• event-clock/7 is set to be the sequencer clock – Reason: 7 is a common factor of BEPCII ring RF and linac RF

frequnecy.

• Bn = MOD(Rn*35, 396), for BEPCII colliding mode– Rn is the SequenceRAM unit number, Bn is the bucket number.– Using the above formula, any unit from 0 to 395 in SeqRAM can

be mapped to one and only one bucket in the ring, which has 396 buckets in total.

• The above formula can generate a table, SeqRAM unit to bucket number. Transform it to a table mapping bucket number to SeqRAM unit number.


Map bucket number to SequenceRAM unit number(partly)

Bkt SeqRAM Bkt SeqRAM Bkt SeqRAM Bkt SeqRAM Bkt SeqRAM

0 0 4 68 8 136 12 204 16 272

1 215 5 283 9 351 13 23 17 91

2 34 6 102 10 170 14 238 18 306

3 249 7 317 11 385 15 57 19 125


To select any bucket

• This table is put into an array of one-dimension in our dedicated record support which does the fast bucket selection. The n-th element of table gives the SeqRAM unit which generates the n-th bucket to the ring.

• Similarly, we generate the mapping table for BEPCII synchronized radiation mode by Bn = MOD(Rn*35, 402)


Fast bucket selection event timing + Beam Current Monitor

• A new EPICS record support has been created to do the fast bucket selection,

– Damping time consideration, bucket switch in 50Hz

– protection to BCM hardware

• process

– read BCM values from reflective memory card of BI group, select a bucket of smallest bunch current

– map the bucket number into corresponding SeqRAM unit,

– Set event code to the above unit in SeqRAM of EVG


bktRecord.dbd• BKSE, DBF_LONG, BER TotalBucketNumbers• BKSP, DBF_LONG, BPR TotalBucketNumbers• BKSS, DBF_LONG, BSR TotalBucketNumbers• BKTE, DBF_LONG, BER BucketInj• BKTP, DBF_LONG, BPR BucketInj• BKTS, DBF_LONG, BER BucketInj• BSEL, DBF_LONG, bucket selection method• COUN, DBF_LONG, count• CNTD, DBF_LONG, count down• DONE, DBF_LONG, all buckets done• ENKE, DBF_OUTLINK, Enable/Disable Kicker e-• ENKP, DBF_OUTLINK, Enable/Disable Kicker e+• EVG, DBF_OUTLINK, Output SeqRAM delay to EVG• INJ, DBF_UCHAR, if is injecting • LBKT, DBF_LONG, Last Bucket injected


bktRecord.dbd• MAX, DBF_LONG, max bcm protection value• MODE, DBF_MENU, BEPCIIoperationMode• RLPE, DBF_UCHAR, ReLoadPatternFile of BER• RLPP, DBF_UCHAR, ReLoadPatternFile of BPR• RLPS, DBF_UCHAR, ReLoadPatternFile of BSR• RMMD, DBF_MENU, ReflectiveMemoryMode• RMEO, DBF_LONG, ReflectiveMemory BER Offset for bucket 0• RMPO, DBF_LONG, ReflectiveMemory BPR Offset for bucket 0• RMSO, DBF_LONG, ReflectiveMemory BPR Offset for bucket 0• SEQO, DBF_LONG, EVG SeqRAM offset for bucket 0• TPUP, DBF_LONG, topup autoInjMinBkt


bktRecord.dbd

• PTRE, DBF_NOACCESS, BER Pattern ， extra int ptre[402]

• PTRP, DBF_NOACCESS, BPR Pattern ， extra int ptrp[402]

• PTRS, DBF_NOACCESS, BSR Pattern ， extra int ptrs[402]

• BCME, DBF_NOACCESS, – BCM readout for BER

– extra char bcme[402]

– asl ASL1, – special SPC_DBADDR,

• BCMP, DBF_NOACCESS, – BCM readout for BER

– extra char bcmp[402]

– asl ASL1,

– special SPC_DBADDR


Multi bunch injection control


Multi-bunch injection control

• Control when to inject and when to stop

– Top-off injection, a control loop

– Stop injection when all buckets reach the bunch current limit

• Bucket select method

– The smallest the first

– Next smaller than the bunch limit, according to the sequence in the injection pattern definition file

• Criterion

– Beam current from DCCT, or bunch current from BCM

• Injection pattern definition file: ASCII files


BCM display of 20 * 20 buckets colliding


Revolution frequency

Since our event clock is selected as 499.8MHz/5 = 99.96MHz, no way to generate revolution frequency directly by EVG/EVR with this clock rate.

1. Second EVG of event clock 499.8MHz/4, this method has been using from Oct 2007 to Feb. 2008, second round commissioning for colliding mode of BEPCII

2. Develop a revolution frequency module• Input: Ring RF 499.8MHz• Output: 499.8MHz/396 or 499.8MHz/402• Made by an institute in Beijing• Has been working well since Feb. 2008.


EV

GE

vent

Clo

ck

=49

9.8M

Hz/

5

Fan

out

499.

8MH

z

50H

z T

TL

Fan

out

Fan

out

Fan

out

EV

R

330m fiber cable

EVR330m fiber cable

EVREVR

EVR

120m fiber cable EVR

EVR

EVR

EVR

EVR

16 Modulaters

BT BPM

feedback

e- camera

BCM

e+ camera

120m fiber cable

EVR

EVR

EVR

EVR

EVR BT BCT

Fast bucket select

e- Kickers

BES

e+Kickers

…...

E-Gun

AmplifierPSK

Gun PSe+ PSLinac BI

GU

N-T

X

EVRLibera BPM

120m fiber cable

Agi

lent

E

4434

B

Spl

itte

r

Mai

ns

Syn

ch.

EV

GE

vent

Clo

ck

=49

9.8M

Hz/

4

Fan

out

499.

8MH

z

50H

z T

TL

EVR Libera BPM


Performance: jitter of transport line beam signal (taken from TC-BCT2) to 499.8MHz RF signal is less then 16 pico

seconds. On Apr. 26, 2007, last for 20 minutes.


Acknowledgement

Work done by Ge Lei, Guanglei Xu, Lin Wang, Gang Li, Wenchun Gao, etc. Thanks to the cooperation.

Many thanks to the discussions and suggestions of Jukka Pietarinen (MRF Oy.) , Kazuro Furukawa (KEKB), Timo Korhonen (SLS), Dekang Liu and Liying Zhao (SSRF), Angelos Gorias and Yuri Chernousko (DLS). Special thanks to the 50Hz module from Yuri Chernousko.

Many thanks to the suggestions and cooperation of the colleagues in group of AP, BI, PS Injection, RF, Linac Power Source, Linac Microwave, and detector of BEPCII project.


Thank you!

Documents

EPICS 2008, ShanghaiBEPCII Timing System1 BEPC-II Event Timing System Ge LEI for BEPC-II timing team Institute of High Energy Physics, Beijing Mar. 2008