500 MHz 200 kW CW KLYSTRON FOR PHOTON FACTORY STORAGE RING
T. Okamoto, K. Ohya and K. Takata*Tqshiba Corporation* National Laboratory for High Energy Physics
Introduction
A CW klystron E3774(500 MHz, 200 kW) for pho~on factory storage ring in
KEK is presented.
In the design of high power klystron, it is very important to utilize
the harmonic component contribution .to electron beam 1).
There are two approaches for this purpose:(1) To use the second harmonic cavities,~--E.L.Lien 1 )(2) To use the abnormally long drift spaces,---E.L.Lien 1 ), T.G.Mihran 2 )Design and Performance
In the klystron E3774 to be designed in our purpose, it is required to
get the producibility and the easy handling and maintenance as well as thehigh efficiency. In order to attain the klystron with the efficiency morethan 62.5 % and particularly the reduced length, we analyzed and obtained theoptimum values by the new computer simulation method, which includes theeffect of the high efficiency by the second harmonic contribution.
· As a ·result of this analysis, we found the high efficiency, high gain,
and comparatively short klystron with the different cavity location. from theabove mentioned klystrons!) 2 ) The interval of the input and output gap inour klystron is about a half in the 2nd approach.
The electrical and mechanical characteristics designed for the klystronE3774 are shown in Table 1, and its photograph is shown .in Fig. 1.
The calculated and measured effect of the debunching frequency which
affects the beam in the drift space are shown in Fig.3, where Merit Figure 3 )is used as the calculated efficiency.
The measured efficiency is slightly different from the calculated one,however the tendency resembles well each other. This discrepancy seems to be
due to the fact that the one-dimensional analysis was used, or the parametersof E3774, particularly output Q, are not optimized yet.
Fig.2 shows electron phase angle, normalized RF beam currents, and Merit
Figure vs normalized distance.
Conclusion
We developed the 200 kW comparatively short klystron in this frequency
range with the high efficiency of 53 % and the high gain of 60 dB at 46 kV
8.2 A.
Although the difference between the calculated and measured efficiency
is about 10 %, it can be reduced and the higher efficiency klystron will beobtained by more optimization of designed parameters.
Acknowledgement
We wish to thank Proffessor Puke of KEK for his many
and useful advices.

helpful suggestions

References(1) E.L.Lien, 8th Int. Con£. on MOGA, Amsterdam (1970) 11.
(2) T.G.Mihran,G.M.Bra nch, JR, and G.J.Griffin, JR,TEEE Trans. on ED, ED-18 (1971) 124.
(3) T.G.Mihran, IEEE Trans. on ED, ED-14 (1967) 201.

-217-TabTe ] Desianed Parameter s of E3774::::::::~eousBandwidth ( 0.

/~~ .P0o8in~s~~~~0.5 MHZ

Beam Voltage
Beam Current

40 kV!

RF Power Output (saturatio n)

200 kW l

Efficiency
Gain(satu ration)

62.5 %!
40 dBGain(Po=ld O kW)
Load VSWR
Overall Length

42 dB
1.3
2.5 m

8

A 1I

RF Input
Coaxial Type N Connector
RF Output
WR 1500 Wave Guide
Magnetic Focusing Field
250 GaussCollector and Body

Water-coo led

Focusing Coil and Cathodej___,425 £/min
Air-Coole d-----·-------

Fig. 1 Klystron E3774

Fi .2 Electron phase angle, Normalize dRF beam current, and Meritfigure vs Normalize d distance.

-218-lFig.3 Efficiency vsDebunchin g frequency .