512 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 63, NO. 1, JANUARY 2016
Simulation and Experiments of a W-Band
Extended Interaction Oscillator Based on
a Pseudospark-Sourced Electron Beam
Yong Yin, Wenlong He, Liang Zhang, Huabi Yin, Craig W. Robertson, and Adrian W. Cross
Abstract—This paper presents the first experimental results
of an extended interaction oscillator (EIO) based on a
pseudospark-sourced electron beam, which produced a peak
output power over 38 W at W-band. The advantages of the
newly developed device are: 1) transport of the electron beam by
the positive-ion focusing channel without the need of an external
magnetic field and 2) high interaction impedance and high gain
per unit length of the EIO circuit. The experimental results agree
well with the 3-D particle-in-cell simulations.
Index Terms— Extended interaction oscillator (EIO),
pseudospark-sourced electron beam, vacuum electronics.
I. INTRODUCTION
P
SEUDOSPARK discharge systems based on the hollow
cathode can produce axially symmetric-pulsed electron
beams along the axis of the cathode cavity [1]–[3]. The
production of higher current density electron beams, compared
with thermionic cathodes, from pseudospark discharges has
been convincingly demonstrated [4]. This property meets the
urgent need of very high current density electron beams in the
generation of coherent millimeter-wave and tera-hertz wave
radiation.
At millimeter and submillimeter wavelengths
(terahertz frequencies), the achievable output power of
the conventional O-type vacuum electronic devices is greatly
limited by the electron beam current that can transport
through the device at a particular voltage. The current density
of a pseudospark-sourced electron beam is of the order of
hundreds of A/cm
2
or higher [5], [6], which enables a wide
range of applications in generating millimeter-wave and
submillimeter-wave radiation [7]. Yin et al. [8] demonstrated
that the electron beam pulses with a 3-mm diameter can
Manuscript received August 21, 2015; revised October 13, 2015 and
November 8, 2015; accepted November 19, 2015. Date of publication
December 8, 2015; date of current version December 24, 2015. This work
was supported in part by the Engineering and Physical Sciences Research
Council, U.K. under Grant EP/G011087/1 and in part by the National Natural
Science Foundation of China under Grant 61201011. The review of this
paper was arranged by Editor M. Thumm. (Corresponding author: Yong Yin.)
Y. Yin is with the University of Electronic Science and Technology of China,
Chengdu 610054, China (e-mail: yinyong@uestc.edu.cn).
W. He, L. Zhang, H. Yin, C. W. Robertson, and A. W. Cross are with the
Department of Physics, University of Strathclyde, Glasgow G4 0NG, U.K.
(e-mail: w.he@strath.ac.uk; liang.zhang@strath.ac.uk; h.yin@strath.ac.uk;
c.w.robertson@strath.ac.uk; a.w.cross@strath.ac.uk).
Color versions of one or more of the figures in this paper are available
online at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TED.2015.2502950
Fig. 1. Experimental setup of the W-band EIO based on a
pseudospark-sourced electron beam and the schematic drawing of the
experiment.
be transported distances up to 20 cm without a guiding
magnetic field. To work with the pseudospark-sourced
pulsed electron beam, automatic optimization techniques
can be used to shorten the klystron interaction structure [9].
An alternative technique is to use the extended interaction
oscillator (EIO) circuit, which has the advantages of high
interaction impedance and high gain per unit length [10].
A W-band (75–110 GHz) EIO circuit operated in the
2π mode was selected for our first experiment because of
its shorter interaction length as compared with a backward
wave oscillator. The beam voltage was designed to be centered
at 30.5 kV, which is suitable for a four-gap pseudospark dis-
charge. This newly developed device combines the merit of a
short interaction circuit in the EIO and the high current density
property of the pseudospark-sourced electron beam to generate
W-band coherent radiation. The design and optimization of
the W-band EIO with a pseudospark-sourced electron beam
has been carried out. Experimental results show that with
a 35-kV discharge voltage, the oscillator produced W -band
microwave radiation pulses with a 38-W peak power and 20-ns
duration, which agrees well with the 3-D particle-in-cell (PIC)
simulations using MAGIC.
A photograph of the W -band oscillator based on a
pseudospark-sourced electron beam and the EIO circuit, which
includes a schematic drawing of the experiment, is shown
in Fig. 1. It does not need an external focusing magnetic field
and is capable of operating in a high repetition rate (up to a
few kilohertz) [11]. From a review of the literature, this is the
first experiment of an EIO based on a pseudospark-sourced
0018-9383 © 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.
See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.