JAERI-Conf 95-021

PB18
VME BASED CONTROL SYSTEM FOR THE TRISTAN CORRECTIONDIPOLE POWER SUPPLY
Hitoshi FUKUMA, Kuninori ENDO, Atsushi KABE, Haruyo KOISOand Tadashi KUBO
National Laboratory for High Energy Physics
Oho, Tsukuba-shi, Ibaraki-ken, 305, Japan
Abstract
The control system for the TRISTAN correction
dipole power supply was improved to cure the beam loss
during the energy ramp. The main part of it is based on
VME standard. This paper describes the system
configuration, the software and the operation with thebeam.
I .Introduction
The TRISTAN MR has 520 correction dipoles named
correctors to control a closed orbit. Their power supplies
are placed in four buildings around the ring. Initially thepower supplies was controlled by a specially designed
Power Supply Control Module(PSCM) with Motorola
68B09 and driver units[l,2]. The module calculates thecurrent of the power supplies Ii according to the formula
Ii=Ai Io+Mi, where Ai and Mi are constants which areindexed by a power supply no. i and Io is a waveform(i.e. "pattern") in an accelerator cycle. Io is similar tothe current of the main dipole power supply and common
to all power supplies. In the energy ramp Ii was uniquelydetermined from the injection and flat top current because
free parameters were two, Ai and .:iii. For several years
after the commissioning of MR this system functioned
enough for the energy ramp. As the beam current
increased it was found that the beam life time at injection
was very sensitive to the RF voltage, the betatron tunes
and the vertical closed orbit. And the beam loss during theenergy ramp became troublesome. One of the cause of thebeam loss was considered the deviation of the closed orbit
from the optimum one at injection. This led to us todevelop a new control system of the correction dipole
power supply to control the closed orbit more finely.
In the new system the PSCM was replaced with a
VME based system while driver units remain unchanged.
We employed VME system because of its flexibility inchanging a software.
2.System Configuration
Fig. 1 shows the schematic diagram of the system.
The system consists of three parts, l)VME system,2)Control computer Hitachi HIDIC and serial CAMAC
system and 3)Driver units.
The VME system is Hitachi Zosen's Portable VMEsystem(HIMV-P254/N) . The system consists of a rackwith 7 slot back planes, a CPU board Motrola MVME147S, a 100MB hard disk drive and a floppy disk drive.
The operating system is PDOS from EYRING Co ..

The CPU board calculates the current of the power
supplies and write it to a digital output(Hitachi ZosenHIMV630). The output-signals are transferred to thedriver unit through 21 parallellines(12 bits data, 7 bits
address and 2 timing signals). The data of 72 power
supplies are sent sequentially on the lines. The timing
sequence of data transfer is emulated by a software so as
to fit the driver units. VMEbus interface, KSC 2917-ZlA
is used to communicate with the HIDIC through memory
modules. The clock interrupt, which is controlled by aHIDIC, initiates a program. The maximum repetition rateof the clock is 50Hz. So the CPU calculates and outputs
the data every 20ms. The interrupt is accepted by FORCESYS68KIIPIO-l.
HIDIC and serial CAMAC system are a part ofTRISTAN control system[3]. The 128KB memory
modules in the CAMAC crate, which are accessed fromboth HIDIC and VME CPU, are used for thecommunication between them.
The driver units are the part of original control systemwith PSCM. They accept the data from the digital output
and distribute the data to each power supply.
3.Software
A.VME system
A device driver was written for VMEbus interface
KSC 2917-ZIA. This supports CAMAC 16 bit single
transfer and CAMAC 16 bit DMA transfer. The datatransfer-time is about 50 )ls/word for the single transfer
and 3.5 )ls/word for the block transfer. The device driversof FORCE SYS68KIIPIO-l and HIMV630 were preparedby Hitachi Zosen.
Two functions are written as application software forl)Cyclic operation and 2)Current-setting at static states.
l)Cyclic operation
A function is called in cyclic operation of MR such as
the energy ramp, the squeezing of the beam and thesetting current from flat top to injection. The cycle goesby synchronously with the clock pulse. Whole accelerator
cycle is divided into 14 periods by 15 nodal points. Thetime, which is measured by the number of the clockpulse, and current at each nodal point is stored in a
"clock-current table" in the memory module. The currentof a power supply I(t) at a clock tis calculated as-298-JAERI-Conf 95-021

calculation, the data transfer from/to the memory moduleand the output of the data, is 8ms for 130 power supplies.

during the energy ramp and2)Current-setting at static states
Another function is called at injection and flat top.
The current is changed from present set point to new
point in the total steps N step· This function is initiatedNstep times by the clock interrupt. At each step thefunction calculates the current by linear interpolation ofpresent and new set point.

in remaining periods, where tN and tN+ 1 are the clocks at
nodal point N and N+ 1 respectively. The clock t satisfies
the condition tN< t < tN+1· IB(t) is the current of themain dipole power supply at clock t. IB at each clock isstored in the memory module.
The total processing time, which includes the aboveJMemorymodule,.......-Auxiliary
crate controller(KSC j3922-Z1 B)

Netwo rk of HIDIC

Mini-computer(HIDIC)ICAMAC crateCPU(MVME-147S}

P1lClockinterruptI

Serial crate controller

Digital output(HIMV630}-----VME crate~1\g121/I II

VME bus lnte rface(KSC 2917-Z1 A) Interrupter(FORCE SYS68K/IPI0-1)

Driver units••••••••••••••••Local control room--------.-

t----------t-1- 1--

IPower supply-room IPower supplies••••••••• • ••• • ••Fig. 1 Schematic diagram of the control system for the TRISTAN correction dipole power supply.

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Table 1B.HIDIC
Programs are prepared for !)Management of the clockcurrent table and 2)Control of the clock interrupt.

A result of the closed orbit correction during the energy
ramp.

4.0peration
Nodalno.

In the operation 11 nodal points are used during theenergy ramp. The nodal points are denser in low energy
region than in high energy region because the beam loss
occurred very often below llGeV. Following procedures
are taken in the beam tuning for the energy ramp.
1)The current which corresponds to the kick by thecorrectors at injection is set to all nodal points.
2)The closed orbit at injection c.O.inj is measured. Thenthe energy ramp starts.
3)The energy ramp is suspended at the clock
corresponding to a nodal point and the closed orbit
c.o.nod is measured. This procedure is repeated for all
nodal points.
4 )An orbit correction program calculates the kick of thecorrectors {A9} to correct the difference between c.o.nod
and c.O.inj• where {... } means the list of the kick by thecorrectors. The {A9} at each nodal point is stored in afile.
5)The kick at each nodal point is calculated as {9inj}+{A9}, where {9inj} is the kick at the injection. The
current corresponding to {9injl+ {A9} is set in theclock-current table.
6)The procedure 2) and 3) are repeated to confirm that theclosed orbit is really corrected.
Table 1 shows an example of the result of the above
correction . ...f<Ay2> is the r.m.s. of the difference between
the vertical closed orbit at injection and that at a nodal
point. Average < > was taken over the beam positions
around the ring. Nodal no. 1 corresponds to the injection
stage.
Actually, the closed orbit in the energy ramp being
suspended is different from that in the energy ramp beingin progress. But we have no way to measure theinstantaneous closed orbit because the measurement takes
about a minute in the present beam position monitor
system.
We can not state clearly the effect of the correction on
the beam loss. On one occasion the beam loss disappeared
after that. On another occasion, in addition to thecorrection, another ways such as the change of RFvoltage, the change of the betatron tunes and theoptimization of the closed orbit at injection were needed
to cure the beam loss.
Above correction is made at the beginning of a long
operation period. Once {A9} is determined the procedure5) is taken before every energy ramp because the closed

Energy...f<Ay2> (mm)

(GeV)

2

8.4

beforecorrection
0.14

aftercorrection
0.08

3

9.6

0.31

0.12

4

11.6

0.49

0.14

5

14.2

0.69

0.22

6

16.8

0.84

0.22

orbit at injection is corrected to a standard orbit at every
beam fill. Usually the re-determination of {A9} is notnecessary for three to four months despite the change ofthe closed orbit at injection.
5.Acknowledgements
The authors wish to thank to T. Kato and H.
Nakagawa for useful advise and discussion about VME
system.
6.References[1]Ta. Kubo, To. Ozaki, A. Kabe, H. Fukuma, K. Endo,"MAGNET POWER
SUPPLYAND
IT'S
CONTROL MODULE FOR TRISTAN MRSTEERING MAGNET", Proceedings of the 6th
Symposium on Accelerator Science and Technology,Tokyo, Japan, 1987,161[2]H. Fukuma, A. Kabe, Ta. Kubo, T. Ozaki and K.
Endo, "POWER SUPPLY CONTROL FOR THE
TRISTAN MAIN RING AND ACCUMULATION
RING", Proceedings of the 1987 IEEE Particle
Accelerator Conference, Washington,D.C., 1987,1529.
[3]Shin-ichi KUROKAWA et al., "THE TRISTANCONTROL SYSTEM", Nucl. Instr. and Meth.,
A247(1986), 29.

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