BEAM AND RADIATION SECURITY SYSTEM OF KEK PS
K. Uchino, K. Ishii and T. Kamei
National Laboratory for High Energy Physics
A beam and radiation security system of high energy accelerators have to work without any error throughout operation andmaintenace periods, and the system of KEK PS is carefully
designed and is working without trouble.
The accelerator enclosure of KEK PS has one main gate, eight
subgates and four entrances for large devices. In order to keep
evacuation from the above area during operation and check residual
radioactivit y of every thing_ being carryed out during maintenance ,the beam interlock and the centralized gate control system arebeing used. These consist of personal keys, door limit switches,
remote control electric door locks, emergency switches, gate
monitor TV, a hand-foot-c lothing monitor and the logging computer
system. Fig.l shows a block diagram of the system.
1.

The Beam Interlock System

The personal keys are assigned for every staff working in theaccelerator enclosure. These are usually inserted in the key
switch panel and the electric door lock can be released by thepersonal key, so one must to take out his key from the switch when
he enters the enclosure. Status of all key switch is displayed on
the accelerator control desk with the personal names. All key
switch circuits and door switches interlock to.the accelerator
beam switch. Actual beam acceleration starts some time C~ 20 sec)
after the beam switch is turn on. If anyone is accidentally left
in the accelerator enclosure, he can interrupt the beam by theemergency switches distributed in the enclosure during the above
period. However such a case has not yet occurred.
The beam from the ion source is controlled by the triggerpulses that is gated by the logic circuit connected with the beamswitch and the beam stop is insured by the beam shutter in thebeam line to the linac tank, even in case of accidental beam
acceleration in the preinjector.
2.

The Centralized Gate Monitor and Control System

Every gate door is equipped with an electric lock and it canbe released by the personal key under control of the guardman on
duty in the central control station. He can watch and checkentrance and exit at each gate by TV monitor, and the interphones
are used to communicate between the gates and the central station.
Prior to going out from the accelerator enclosure, everyone
has to check his own body and all things carried by him using thehand-foot-c lothing monitor at the main gate.
3.

The Logging Computer System

The personal key switches and all do~r switches are connectedto the minicompute r system and it records the name and the time ofgoing in and out for each person, and also each gate open time.
Measurments of thermolumin escence dosimeters for each person arealso recorded in the computer, and it make a list of the personal
data concerning the number of entrance times, the total hours in-87-

the accelerator tunnel and the total radiation dose. This computer also summarizes the operation record through the link withthe touch key board and the accelerator beam control system.
A new gate radiation monitor system is being developed by
the KEK Radiation Safty Group, and this will enable automatic andhigh accurate survey of human body and others.
Acknowledgement s
The authors would like to express sincere thanks to the KEK
radiation safety group for their collaboration in design of theradiation security system.

r.=------lI=ilJElECTRIC ibJR locK

I ~ Ci>J.'ERAI

AccELERATOR DeviCESl& CooROL KEY BoxiNTERI'ImEIEMERGENCY BEAM ·Srop Sw1TC1£s-~=-~------1I I PERSOOAL KEY PANEL

12 SIMILAR STATIONS-~~-~!
fWm,fooT & CloTHING

1L.:::: ______ _ -~~~- ==:!Jl'l\IN bATE DEVICES

Fig. l-88-