REMOTE CONTROL SYSTEM FOR TANDEM ACCELERATOR
T. Nakashima and T. Maeda
Tandem Laboratory, Department of Physics, Faculty of ScienceKyushu University
This report describes some devices for a system;of data communication
between ground potential and high voltage terminal (HVT) of the electrostaticaccelerator.
For the purpous of signal transmission between different electric
potential, light link device which is composed of a pair of light transmitterand receiver should be very adequate means, and recent development of optical
data communication techniqu~. using optical fiber cable makes possible toconstruct a very reliable remote control system for electrostatic accelerator.
Recently such a system has been used successfully in several machines, andthe optical fiber cables are set along the indulation columns.
The light link system in the kyushu University Tandem accelerator
however has not been used any light guide materials such as optical fiber,
and the light path was taken to radial direction of the column axis, andlight link transmitters and receivers are faced each other through pressure
vessel window and a slit of 2cm width on the shell of HVT.

The relativePosition of HVT and pressure vessel window changes a few mm following thegas pressure, and to insure the operation of the remote control system inany gas pressure, the syze of light spot at the receiver sets about 8mm dia.
The term "remote control system" is used in this report as a general name ofremote operation system and telemeter system, the former has light transmitters at ground potential and operating the devices in HVT, e.g. vacuum pump,
stripper foil changer, charge inductor etc, the latter has light transmittersin h~T and the data are transmitted to control desk.
Remote Operation System
Four laser light sources (1 m~v He-Ne laser tubes were placed at
the out side of the pressure vessel and corresponding four phototransistor receivers were mounted in a small case placed in HVT.

Toavoid the affect of environmental light, the receiver case has four
small aperture cr,llimator (lmm dia., lOmm thick) faced each light source.
These collimator drop the laser bight intensity about 1/50, however,high efficiency photo-transistor (NEC PD32) can drive small power relay
directry.

This system operates as a channel selector by the order offour light sources turn on time sequence.

Each light source has ashutter of light path and if one make one of the remote control s1-ritchs-247-

at the control desk, the shutters are opened one by one following thecoded ordering.

When the third shutter is opened, receiver circuit in

HVT can select out one channel out of 24 channels ( 4P 3=24), and wither
the fourth shutter is opened or not double the selectable channel
number.

Then the remote operation system can make any one of 48 diffe-

rent circuits at a time.
Telemeter systemGas discharge tube (NEC-Rll68) have been used for the signal converterto the light.

This tube works rather wide frequency rang~ and then deand low frequency signals are converted to modulated signals of highfrequency (PCM or AM modes) for preventing the disturbance of environmental light, i.e. lightning of discharge and lighting in the vessel.
Principle of the signal converter to the light are shown in figure.

t).2)

.3)

f; pulse counts/sevond at PCM mode0 < f < 5000 Hz

v; (gas discharge starting voltage)-(discharg e quenching voltage)-248-