A NEW PULSED MAGNET CONTROL SYSTEM IN THE KEK
ELECTRON POSITRON LINAC
Y. Enomoto∗ , K. Furukawa, T. Natsui, M. Satoh, KEK, Tsukuba, Japan
H. Saotome, Kanto Information Service Tsukuba, JapanCSS
SS archiverarchi

AbstractLAN

DC power supplycontroll server

DC power supply

PXI express(fast controll)pules driver

event signalmagnet

INTRODUCTION

cRIO(interlock and data logging)

In 2017, sixty-four pules magnets (28 quadrupoles and36 steerings) were installed in the KEK electron positron
LINAC for simultaneous injection to four different rings.
Since each ring requires different injection energy, magnetic field in the injector LINAC has to be changed shotby shot (every 20 ms) according to the destination of thebeam. To realize such operation, a PXI express based newcontrol system was installed. At present, 13 units are stably
in operation to control 64 magnets. Further installation ofthe magnets and control system is planned in 2018.

operater´s machineNAS

standard unit
EPICS CALXI ver 1.3
NI network shared variable

Figure 2: Block diagram of the system.

Figure 1: A schematic view of electron and positron accelerator complex in the KEK
Figure1 shows electron and positron accelerator complex
in the KEK. There are four storage rings, i.e. two rings
for light source, PF and PF-AR, and two rings for electron
positron collider, SuperKEKB HER and LER. In addition
to them, positron damping ring have been in operation since
Feburary 2018. All of the rings require full enegy injection
but the value of energy is different as shown in the figure
1. To satisfy the requirment, 64 pulsed magnets were installed in 2017. Using these magnets, magnetic field can bechanged shot by shot in 20 ms and was optimized for each
destination. In this paper, the control system for the pulsed
power supply using PXI express unit with event timing system controlled by EPICS and LabVIEW is shown in detail.

OVERVIEW OF THE SYSTEM
Figure2 shows a block diagram of the system. One standard unit consist of a PXI express unit for fast controll, DC
power sipplies, pulse drivers and NI cRIO unit for interlock
and slow data acquisition. There is one compture to controll and monitor all of the 64 DC power suplies. A CSS∗ yoshinori.enomoto@kek.jp

archiver and A Network attached storage are used to log
various data not only output current of the power suppilies
but temperature of the IGBT in the pulse driver, status of
the DC power supplies and so on. EPCIS channel accessprotocol is mainly used for the communication among computers. LXI ver 1.3 protocol is used to control the DC power
supplies and NI network shared variable is used to send fast
waveform data. As for the event timing system, dedicatedoptical fiber is directly connected to the module. Most ofthe software is writte by LabVIEW 2016 (32 bit) with NIDSC module.

PXI AND EVENT TIMING SYSTEM
For the fast controll, PXI express unit plays major role.
The unit, shonw in figure 3, consists of a PC and a PXI express chasis with four cards, a controller board to connect
to the PC, an event reciever board (EVR), a DAC board,and a ADC board, which can set and monitor output current up to 8 pulsed power supply independently in 16 bit
resolution with 1 MSa/s sampling or update rate. They areplaced in the same rack and connected by a metal cable. AnEVR board in PXI form factor is used to integrate the timing system to the LINAC timing system. In our LINAC,
event timing system by Micro-Research Finland Oy (MRF)
is adopted. The EVR recive not only the timing information
but also the mode number and shot ID. The mode number
is used to determine the next output setting. The shot ID isused to tag the monitored information. The trigger timing isprescisely (in the order of a few times 10 ps) adjusted 3 ms
before the beam arraival. Since the rising and falling timeof the magnet current is in the order of ms, pules shape ofoperater´s machine
NAS Qnap TS-431XU-2GLAN

EVR MRF PXI-EVR-230

DAC NI PXI-6733

controll PC
Windows 8.1
LabVIEW 2016 (32 bit)

ADC NI PXIe-6356

PCIeGen2 x8

Contreller NI PXIe-8381

chasis NI PXIe-1082

event signal (opt. fiber)

Figure 3: PXI express unit
the power supply does not important as long as the reproducibility is assured.

EVR, the DAC and the ADC start ouputting and digitizing
data for 6 ms. Aquired ADC data array is concatinated withshot ID and mode number, then issued to the network using NI network shared variable protocol every 20 ms. At
the same time, one point, at the timing of the beam passing through, in the ADC data array is chosen and issued tothe network with mode number using EPICS channel accessprotocol. Every one point data with timetsamp, shot ID andmode number is buffered in the memory of the control PC
for 10 s then they are dumpt to the text file in the local storage of the PC. The file is copied to the NAS every 60 s byanother process. By this way, output current of the power
supply for all of the shot (every 20 ms) is stored in the disk.
Even though the windows is not a real-time OS, the dataloss rate is less than ppm which is acceptable value for us.
The amount of the data is about 3 TB/year for 64 ch. Inaddition to real-time monitoring, logging by CSS archiver
every 10 s is also available for all the channel. Suplemental softwares such as, remote monitoring ADC data array,detecting hung-up of the main programs etc. are also prepared by LabVIEW and runnig on the windows machine in
the control room.

INTERLOCK SYSTEMSOFTWARE
output current read back (EPICS CA)
waveform data(NI network
shared variable)

DAC data arraymode 1

DAC data arraymode 12

local memory local storage
in PC
in PC (SSD)

To DACDC power supplycontroll server

relay out NI 9482

from ADC

relay out NI 9482

point
data

NI cRIO-9063

DIO NI 9403

ADC data array

ADC NI 9205

mode #operater´s machine
hicopy file to NAS

shot ID

selector

output value control (EPICS CA)

data buffer from EVR

Figure 4: Data flow in software
In terms of software, Windows 8.1 and LabVIEW 2016(32 bit) with DSC module are mainly adopted to control
the hardware. EPICS channel access (CA) protocol and NI
network shared variable procotol are used to communicate
with operator’s interface panels. Figure 4 shows data flowin the software. Twelve DAC data array according to thebeam mode are prepared in advance in the PC’s memory.
Each DAC data is recalculated by putting a new value using
EPICS channel access protocol. Data buffer informationfrom the EVR is delivered to the main software a few millisecond after the last trigger. Then, one of the DAC dataarray is selected according to the next beam mode and updated to the DAC’s memory. By the trigger signal from theDC power supply x8
kisukui PWX series

Figure 5: Interlock system
NI compactRIO unit is used for the interlock nad slow
data aquisition. One unit consists of a 32 ch 250 kSa/s/ch
ADC module, a 32 ch TTL digital I/O moduse and two 4ch relay output modules. It covers 4ch of the pulsed power
supply, namely for one PXI express unit (8 ch), two cRIO
units are needed. To realize robust interlock system, cRIO isworking not in a scan engine mode but in a FPGA mode. Onthe upper layer, EPICS CA server is running on the NI RT
Linux. Not only the PVs for the ADC and DIO data, but thePVs for the high and low threshold, average number to controll data acquisiotn are also prepared which can be set andread using EPICS CA protocol. Between each analog anddigital input channel and each relay output channel, matrix
mask information PVs are prepared, that determine which
input channels are used for interlock signal of the which output channels(see figure 6). This method make it possible for
us to flexisbley change the intelrock setting.

November, simaltenouse injection using the newly installed
pulsed magnets were demonstrated successfully. Since theSuperKEKB phase two operation start from March in 2018
and light source rings restart in May, real simaltenousu injection operation start in the middle of May in 2018.

CONCLUSION
A new pulsed magnet control system using PXI express
unit with event timing system are developed and installed in2017. They are now working in the KEK electron positron
injector LINAC without any severe troubel for 7 monthes.

UPDATE PLAN

Figure 6: Matrix mask setting pnale.

OPERATION
After four months installation work from May, comprehensive test was done for a month in September in 2017. InIn summer shutdown in 2018, another 32 pulsed magnets are plan to be installed. The same controll system will
be adopted but the major update of the software is planned.
One of the important update is to synchronus data acquisition among different PXI express unit and further different
equipment like RF monitors and beam position monitors forbetter beam analysis and control.