JAERI-Conf 95-021

2a4-1
HIGH STABILITY, HIGH CURRENT DC-POWER SUPPLIES
K. Hosono, K. Hatanaka, T. Itahashi, I. Miura, K. Sato, T. Saito, A. Shimizu,
K. Takahisa, K. Tamura, T.Yamazaki, S. Ano, M. Kibayashi, H. Tamura, M. Uraki

Research Centerfor Nuclear Physics, Osaka University,
10-1 Mihogaoka, Ibaraki, Osaka 567, Japan
Abstract

2. Power Supply for the Main Coil of the Injector

Improvements of the power supplies and the control system of the AVF cyclotron which is used as aninjector to the ring cyclotron and of the transport system to the ring cyclotron were done in order to get
more high quality and more stable beam. The power
supply of the main coil of the AVF cyclotron was exchanged to new one. The old DCCTs used for thepower supplies of the trim coils of the AVF cyclotron
were changed to new DCCTs to get more stability.
The potentiometers used for the reference voltages in
the other power supplies of the AVF cyclotron andthe transport system were changed to the temperature
controlled DAC method for numerical-value settings.
This paper presents the results of the improvements.

The maximum rating currents of the power supply
is 1,430 A and the output voltage is 350 V. The oldpower supply of the main coil was pre-regulated by amotor generator and the DC current was regulated byseries transistors. The stability was about 3x1o-s /8h.
The stability was not so good to get high quality beam.
So, the power supply of the main coil has been changed
to a new one.
The new power supply is pre-regulated by a saturable reactor in stead of a motor generator and is current regulated by series transistors. A current sensor
to achieve high stability is performed with a high precision shunt resistance made of germanium manganese
copper alloy(ZERAMIN) with a temperature coefficient less than 3 ppm.rc between 15°C and 40°C.
The shunt resistance is cooled by temperature controlled water in ±0.1 °C. The feedback amplifier andthe DAC for the current control are placed in the thermostatic oven.
The stability and ripple were examined. The current stability of 4x10- 6 for 8 hrs was achieved at thecurrents between 1300 A and 400 A. The stability wasmeasured with a zero-flux current transformer(DCCT)
put in the cubic for a current monitor. Figure 1 showsa result of the measured current stability. Figure 2
shows a photograph of the voltage ripple of the output. The results are very similar to the stability of thepower supply for the main coil of the ring cyclotron.

1. Introduction

The K=140 AVF cyclotron is a three sector, 180°
single-dee, variable energy machine. Any necessary
isochronous field can be produced by a main coil andsixteen trim coils. The power supplies of these coils
have been used for more than 20 years. The AVF cyclotron is now mainly used as an injector of the ring cyclotron. In order to obtain more high quality and morehigh stable beams in acceleration of ring cyclotron, thequality of the beam from the injector is essential. Accordingly, more high stability of current is required forthese power supplies. Improvements of all power supplies of the injector have been made to achieve morehigh stability.

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1

current : 1000 A-~_.-,'~. _T_' monitor voltage : 6.692865 V· •- (DCCT output)~:-- f
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. 'A result of stabilty measurement of main coil power supply for the injector.

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JAERI-Conf 95-021

3. Zero-flux Current Transformers
Zero-flux current transformers(DCCT) have beenused as current sensors for trim coil power supplies ofthe injector. However, these DCCTs are old and are
not satisfactory in accuracy, reliability and in thermalstability. the current stabilities of the power supplies
were 1x10- 4 • In order to exchange the old DCCTs
used for the trim coil power supplies to more high precision ones, we have carried out performance tests ofa few type of the DCCTs. Figure 3 shows a schematic
block diagram for the measurements. Figure 4 shows

the results of measurements of the temperature coefficients and Figure 5 shows the sensibility( resolution) by
a current change of 1ppm for the two kinds of DCCTs
made by A company and B company, respectively. Thetemperature coefficient of A is less than 0.04ppm;oc
and that of B is about 0.25ppm;oc. The DCCT madeby A company has better quality in both temperature
coefficient and sensibility than one made by B company, but is easily affected by a small noise from theoutside and stops to work. The DCCT made by B
company is not so influenced by a noise. We haveadopted the DCCTs made by B company as the current sensors of trim coil power supplies because wehave to consider a counterplan for a noise.
4. Power Supplies of the Trim Coil for the Injector

Fig. 2. A photograph of the voltage ripple.

A new DCCT has been included as a current sensorof the trim coil power supply. The maximum currentof the power supply is 1500 A. The DCCT feedback
signal is 10 V for the current of 1500 A. The feedback amplifier and the DAC are placed in a oven. We
have measured the current stability of the power supply. Figure 6 shows a result of the measurement of thecurrent stability. We have obtained the current stability of less than 1x10- 5 . The current stability has
been improved by about 10 times in comparison withthe current stability of the power supply. We are going to change the old DCCTs used as current sensors
in other, many power supplies to the new ones of highprecision.
5. Improvement of Power Supplies for the Injector.............................................. ":Fig. 3. Schematic block diagram for themeasurement of DCCTs.

An improvement has been made to the water cooling system of the injector to ensure better beam stability, because the current stabilities of power supplies
are severely dependent on the temperature of the cooling water. So, the temperature control devices of theFig. 4 Results of the measurements of the temperature coefficients.

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Acknowledgements

cooling water have added to the cooling system.

The authors are indebted to IDX Tokyo Densi Corporation and Kudo Denki Corporation for their kindness to provide some data and information.

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1-T- of lpp~ ,- -t ~l:,1.,'.IFig. 5. Sensibility of DCCTs by a current change oflppm.

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Trim 1 700 A ... '..

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Fig. 6. Results of the current stabilities of trim coil
power supplies.
The potentiometers used as the reference voltages in the all power supplies of the injector and thebeam transport system have been changed to the temperature controlled DAC method for numerical value
settings. Due to the DAC method, the old type control system for the injector and the beam transportsystem has been replaced to the computer control system and has been included in the control system of thering cyclotron.
The beam stability for a long time has been
become better due to the these improvements.

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