STATUS OF THE KEK INJECTOR
S. Fukumoto, S. Inagaki, K. Ito, T. Kakuyama, T. Katoc. Kubota, Y. Mori, A. Takagi, E. Takasaki, T. Takenaka andY. Terayama
National Laboratory for High Energy Physics
Since the 2nd Symposium on Accelerator Science and Technology, the KEK
injector has run satisfactorily by improvements and developments of various
equipments. Total operation time of the KEK proton synchrotron and the downtime due to the injector are given in Table I.
The new RF windows were made and tnstalled into the linac tank to avoid
the breakdown on the ceramic surface. 1
In this window, the brazing waseliminated and the metal gascket of Al Helicoflex was used for the vacuum seal
between the ceramic disk and the flange.
The new light link system was made for control of the instruments in thehigh voltage terminal of 750 kV prein~jctor. This system has a pair of opticalfiber cables and two microprocessors.
The vacuum system was improved in the 20 MeV beam line and 650 ~Is turbomolecular pump was installed in the LEBT for improvements of the beam transmission.
Increase of the beam intensity in the KEK injector was tried on June 20th
1979. The maximum intensity of 420 rnA at the entrance and of 200 rnA at theexit of the linac were gotten with the careful conditioning of the high gradientaccelerating column u~der the pressure of 1.4 x 10- 4 Torr and by removing thegrid of the buncher. 3
These values are compared with the design values of 200rnA at the entrance and 100 rnA at the exit. The slight change of the momentum
spread produced by RF beam loading would not be serious to achieve the intense
circulating beam in the booster because beam with a rather broad spectrum (±0.8 %) was favorable for injection into the booster.
Typical characteristics of beam during the operation time from April 1980
are given in Table II. In this run, the narrow spectrum of the momentum wasrequested by the booster group. Therefore, the RF field of debuncher has been
kept in the normal operation level. Since the transfer of beam into the Booster
Synchrotron Utilization Facility starts on July, the 20 beam pulses/sec aredelivered from the KEK injector to the booster.
The transient field induced by the beam was observed with the spectrum
analyser. The higher mode resonances were assigned by measuring the field
amplitude along the longitudinal axis. The spectra measured at the high energy
end of the tank are shown in Fig.l. As seen in Fig.l, the higher mode resonances are excited more strongly by the beam than by RF power, which is suppliedwith double feed system. The phase shift of the transient field was measc,ed,
too. The phase shift due to the beam was less than 3°. The effect of thehigher mode on the phase shift was investigated with the spectrum analyser andthe contribution of TMo11
to the phase shift~ was observed. The phaseshifts calculated with the normal mode analysis 5 agreed with the measured
ones.
In the debuncher, the phase shift of RF field due to the beam was measured
and was less than 13°. The phase compensation in the debunyher was tried andthe estimated effects on the momentum spread was observed. 6
Acknowledgement
The aouthors wish to thank Prof. J. Tanaka and Dr. S. Anami for theirencouragements and the cooperation. We thank Dr. S. Takeda for the measurementof the schottky noise.

-243-References
1)
2)
3)
4)
5)
6)

KEK annual report (1978) 110, 1978.
S. Anami et al; to be published at the 1979 Proton Linear Accelerator
Conf.
T. Sakaue and A. Takagi; .IEEE NS-26, 3983, 1979.
S. Anami et al; The 1979 linear accelerator meeting in Japan, 40, 1979.
T. Sakaue et al; The 1978 linear accelerator meeting in Japan, 54, 1978.
T. Nishikawa; Brookhaven National Laboratory Accelerator Department.,
Inernal Report AADD-87, 1965.
T. Kato et al; to be reported at the 1980 linear accelerator meeting inJapan.
..Table I System downtime and Total operation time
APR. '78

SEP. '78

APR. '79

SEP. '79

APR. '80

AUG• '78

MAR.' 79

AUG. '79

MAR. '80

AUG. '80

1706.4hr.

2384.11760.31888.2

5

Total operating time~s~Preinjector

0.28%

0.24%

0.24%

0.52%

Linac

1.34%

1.02%

0.40%

0.86%

Table II
Characteristic s of beam
after 750 KV
at entrance
at exitaccelerationof linacof linac
Intensity

700 mA

300 mA.s

20 MeVline

150 mA

0.277T*

Emittance· (cm•mrad)

0.87T(Hor.) **0.67T(Ver.)±0.75+±0.35% ***Momentumspread****refered from ref. 4).
** EBIHARA; private cominucation
this was measured with the schottky noise under the D.C.
operation of the booster magnets.

TMo1 oby the beam and RF power
Fig.l

TMo11

by RF power only.

Spectra of RF field in tank-244-