DEVELOPMENT OF FAST CONTROLS FOR BEAM WIRE SCANNER FOR
SuperKEKB
Anindya Roy#, VECC, Kolkata, India
Tomohiro Okazaki, EJIT, Tsuchiura, Japan
Naoko Iida, Kazuro Furukawa, KEK, Tsukuba, Japan
Abstract
Recent development towards the data acquisition
system of the wire scanner (WS) systems of theSuperKEKB injector linac (LINAC) and beam transportlines (BT’s) is described. A VME based system,comprised of charge sensitive ADC (CSADC) board,scaler board, DAC board and Event receiver board, hasbeen installed. The primary aim of the system is to utiliseglobal linac event timing system for synchronized andmode-dependent data acquisition. A set of EPICS device
driver has been developed for new hardware e.g. CSADC,scaler and DAC boards. The combination of latest
versions of firmware and EPICS device driver for Micro
Research Finland (MRF) Event receiver board is also
evaluated and further incorporated in this system. The
application software is developed for simultaneous
acquisition of multiple beam mode data during multimodeinjection of the LINAC. The developed system is tested
successfully after integrating with the existing wire
scanner driving mechanism. The system enables the beam
size measurements at four consecutive locations, thatderive Twiss parameters and ensure the reliable beamtransport to four downstream storage rings.

the beam pulse by an independent gate generation system.
Since LINAC is used for injecting beam of different
characteristic into three storage rings (HER, LER and PF)
simultaneously [6], hence a system synchronised with
LINAC timing system, may be useful to acquire various
beam mode data simultaneously. A VME based system,
as shown in Fig.1, is developed to utilise timing systemevents for WS data acquisition. The speed of the wire isalso changed while scanning the beam for obtaining
maximum data points in minimum scanning time.

INTRODUCTION
The KEK 8-GeV linac injects electron and positron
beams with different characteristics into four storagerings: KEKB high-energy ring (HER), KEKB low-energy
ring (LER), Photon Factory (PF) and PF-AR [2] [5]. The
distance from the linac to the injection points of various
storage rings is about 1km. A well controlled stable
operation is required to maintain high luminosity. A wirescanner (WS) is useful for non-destructive monitoring of
the beam profile for such long beam lines. A set of four
WS are used for beam emittance and Twiss parameter
calculation in optics matching. There are seven such
matching sections in LINAC and BT's. The design ofWS's and its measurement software were reported
elsewhere[1,2,3].
At present, the WS's data acquisition system iscomprised of CAMAC based front-end hardware e.g.
CSADC, Scaler and DAC. A VME based supervisorysystem, running EPICS IOC on VxWorks 5.5, is used tocontrol the pulse motor based WS system andPhotomultiplier Tube (PMT) high voltage. An
independent application program is used to acquire datafrom CAMAC hardware and save it in a memory basedtable. The supervisory system acquires the data from thetable. The data acquisition process is synchronised with___________________________________________#r_ani@vecc.gov.in

Fig.1: Hardware architecture of the system

HARDWARE
The new system is comprised of Motorola MVME5500 CPU, Hoshin V004 Scaler, Hoshin V005 CSADC,PVME DAC, Agilent LAN/GPIB converter and Micro
Research Finland Event Receiver (EVR). The system isconnected to LINAC timing system using single mode
optical fiber through EVR. The EVR is used to generate
gate pulse for CSADC synchronised with incoming
events from global event generator of the timing system.
The movement of the wire is controlled through pulse
motor controller using LAN/GPIB converter. A GPIB
based multi-channel digital voltmeter is used measure theabsolute
wireposition
throughpotentiometricarrangement. The DAC is used to control the PMT bias
voltage.

SOFTWARE
The Experimental Physics & Industrial Control System(EPICS), a standard open-source dual layer software toolfor designing distributed control system, is adopted toimplement the supervisory control software in LINAC as
well as in all four storage rings. An EPICS Input-Output
Controller (IOC), running on VxWorks 6.8, is developed
for control and data acquisition for the WS system.
Since the user interface panels are developed and tested
for the existing IOC of the WS system. Hence it isdecided to retain the same software interface with userinterface panel while developing the new system. Theforegoing requirement is resolved by designing a newEPICS record, Wire Scanner (WS) record. In this record,
data from various sources e.g. CSADC, Scaler, Beam
Position Monitor (BPM) etc are acquired through input
links and stored in a predefined array format while
processing of the record. The maximum number of sucharray is to be specified while defining the record. To
incorporate BPM data, options are kept for obtaining
BPM signals and further calibration of the BPM signals.
The Beam mode data is appended dynamically to thearray through an additional field. A field is also provided
to specify the delay in processing the record to fine tune
the hardware e.g ADC with event signal. The record isdesigned as a ring buffer of the data array. A header isprovided to specify total size of the buffer and the latest
data position in the buffer. In this system, the buffer
length is kept for storing 2048 events. On each event, therecord acquires data from four scaler channel, three BPM
signals and twelve CSADC channels.
In LINAC and BT, the simultaneous top-up injections
to three rings, KEKB-HER, KEKB-LER, and PF isrealised by a global fast event-based control system [4].
In this system, various beam line equipments arecontrolled through a set of event codes, broadcasted
sequentially for each beam mode. An event generator,
clock synchronised with RF, is used to sent event codes
along with clock to various event receivers distributed
along the beam line through optical link. The event
receivers decode the event codes and generate timing
signals for the related IOC's to control subsequent beamline equipments e.g. klystrons, magnets etc. A set ofMicro Research Finland event generator and event
receiver modules are used for timing system in LINAC
and BT. There are maximum six event codes e.g.
preparation, klystron-1, klystron-2 etc. for each beammode in the present configuration. In the wire scannersystem, the event signals for klystron 1 & 2 are used fordata acquisition. The event signal for klystron-1 is used to
set the gate width and gate delay value in EVR dependingon the beam mode. The subsequent klystron-2 signal isused for gate generation and data acquisition.
A set of EPICS device drivers are developed for
CSADC, Scaler and DAC hardware, while Asyn driver isused for LAN/GPIB and existing latest driver is used for
EVR. Since there are three distinct positions of the wire
scanner for maximum signal, peak, in PMT. Hence a
combination of slow and fast speed is used during
scanning to get maximum data at the desired wire position
keeping overall scanning time to a minimum. The options
are provided for specifying high speed, slow speed, peak
positions and width around the peaks by the user.

TESTING & TEST RESULTThe new wire scanner system is installed in the Sector– 5 of the LINAC. After installation, the gate delay andwidth are adjusted with PF, PF Study, AR and AR Studymodes. The wire speed, peak positions and width areoptimised after multiple scanning. Some minor changes
are also done in the user panel to adopt software interfaceof the new system. The final system is tested with PF andPF Study modes. The test results are shown in Fig 2 & 3.

Fig.2: Test result

Fig.3: Test result
It can be seen that the wire speed is fast at thebeginning of scan and becomes slow down around thethree wires. Owing to that, we can speedily take the data
points enough for obtaining the width of the peakalthough the beam repetition rate is constant, e.g. 10 pps.
A user panel is developed using EPICS MEDM tool forfine tuning of the system by specifying various
parameters e.g. wire speed, peak position, width, beammode etc. It is shown in Fig.4.

REFERENCES

Fig.4: User panel

CONCLUSION
The new system is developed to acquire wire scanner
data of multiple beam mode simultaneously. This system
will contribute significantly for beam tuning during
SuperKEKB commissioning and subsequent stages.

ACKNOWLEDGMENT
Authors would like to acknowledge their kind regards
to Dr. R. K. Bhandari, Dr. D. Sarkar and Dr. Sarbajit Pal,
Variable Energy Cyclotron Centre for their support andencouragement towards this development.

[1] N. Iida et al., “Recent Progress of Wire Scanner Systems
for the KEKB Injector Linac and Beam Transport Lines”,
Proc of EPAC2000, Vienna, Austria, June 2000., pp.17381740[2] N. Iida et al., “The First Results of Optics Matching Using
Wire Scanners for the KEKB Beam Transport Line”,
Proc of PAC99, New York City, USA., March 1999,
pp.2108-2110.
[3] Y. Funakoshi et al., “Beam Tests of a Wire Scanner for the
KEKB Injector Linac and Beam Transport Line”, Proc of
APAC'98, Tsukuba, Japan, March 1998, pp.537-539.
[4] K. Furukawa et al., “New Event-based Control System for
Simultaneous Top-up Operation at KEKB and PF”, Proc of
ICALEPCS2009, Kobe, Japan, Oct.2009, pp.762-764.
[5] I. Abe, el al., “The KEKB injector linac”, Nucl. Instrum.
Methods A 499 (2003) 167-190[6] N. Iida, el al., “Pulse-to-pluse Switching Injection to Three
Rings of Different Energies from a Single Electron LINAC
at KEK”, Proc. of PAC09, Vancouver, BC, Canada,
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