V![-12OPERATIONAL RESULTS OF KEK
KICKER MAGNET SYSTEM
Shichiro Tazawa,

Koji Takata,

Yoshitaka Kimura

Nationa Laboratory for High Energy Physics
Oho-machi, Tsukuba-gun, Ibaraki-ken
In KEK Proton Synchrotron 3 kicker magnets are fired insynchronization with the 500 MeV beam bunch to extract it fromthe booster ring at a maximum rate of 20 Hz, and 4 kicker magnets for the injection into the main ring are triggered at every 2 seconds by 9 sequential pulses of 20 Hz. Each magnet has
its own HV pulse supplying system which generates 40 KV 200 nSpulses with a rise time of 35 nS for a 25 ohm system. The block
diagram is shown in Figure 1. The basic principles of this system is slmilar to those of CERN PS (1). The details were already described in a previous re:port(2). The system has been
operated since summer of 1975. The total heating time of themain thyratron CX117l is about 6000 hours, and we have experienced some troubles peculiar to a HV pulse supplying system.
The HV is generated by a resonant charging method. A 40cmx33cmx57cm dry transformer with a winding ratio of 100:20000
charges a 3.5nF PFN up to BOKV in 2.5mS when the primary winding is excited by a 25mF condenser bank held at 260V. There
have been neither HV breakdowns nor thermal troubles for 20Hz
continuous operations with respect to the windings molded byan epoxy resin and also to the peak holding diode. The HV supply and PFN are connected with a 10m long standard 50ohm coaxial cable l0D2V which has lOmm¢ polyethylene (PE) layer. Thiscable, though flexible enough, has been one of weak elements,
as 15 times of the HV breakdown have already occurred for the 7systems. We are now trying a l0D2V with a semiconductor layer.
The PFN is a 36m long standard 50ohm cable 20D2V with a 20mm¢
PE insulation layer. The both ends of the cable are connected
into a thyratron housing. Thus it forms a 18m long 25ohm PFN.
The PFN has showed no HV breakdown, but a 20D2V with a semiconductor layer is also now under testing. The main thyratronCXll7l is housed in a oil filled case. Every tube is operated153with a reservoir voltage 10% higher than that specified by English Electric Valve Co. Ltd .. After 5000hours of operation, 3of 7 tubes began to show some delaying and jitter of the switching time which is normally about 230 nS. One tube was replaced,
and the other two are now used with a reservoir voltage raised
still by 10%. The housing, vacuum chamber in which the magnets
are enclosed, and terminating resistor are connected by a pairof the 20D2V cables. The termination of these cables is doneby a specially designed connector(2). There are used 56 suchconnectors. They have shown 38 times of the HV breakdown • Mostof them were due to Teflon which was at first employed for theinsulating material. After changing it for PE no troubles havebeen encountered. The other troubles are found in a trigger
circuit for CX1171. A 10 V 1 microsecond input pulse is amplified by EFP60 and then a 1.6KV 2 microsecond output pulse isgenerated by 3045. Usually the delay in the former stage is 60nS and 120 nS in the latter. During operation we have encountered rather frequently the elongation and jitter of these delaysand we have had to change EFP60 22 times and 3045 13 times.
By improving the components and periodical checking ofthe system, the down time of KEK PS due to the failure of thekicker system have been greatly reduced. At present it is about
1% of the total operating time.

Figure 1
References:(1) D.Fiander: CERN/MPS/SR 71-5 (1971)(2) K.Takata, S.Tazawa, Y.Kimura: KEK-76-21 (1977)

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