Relativistic Klystron Two-Beam Accelerator studies at the RTA test facility Page: 4 of 6
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RELATIVISTIC KLYSTRON TWO-BEAM ACCELERATOR
STUDIES AT THE RTA TEST FACILITY*
G.A. Westenskowt, D. Anderson, S. Eylon, E. Henestroza , T.L. Houckt, J.S. Kimi,
S.M. Lidia, L.L. Reginato, D.L. Vanecek, S.S. Yu
Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, USA
t Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550, USA
* Fusion and Accelerator Research, 3146 Bunche Ave., San Diego, CA 92122, USA
University of California, Davis, CA 95616, USA
A prototype rf power source based on the Relativistic
Klystron Two-Beam Accelerator (RK-TBA) concept is being
constructed at the Lawrence Berkeley National Laboratory to
study physics, engineering, and costing issues. The
prototype, called the RTA, is described and compared to a full
'scale design appropriate for driving the Next Linear Collider
(NLC). Specific details of the induction core test and pulsed
power system are presented. Details of the 1-MeV, 1.2-kA
induction gun currently under construction are described.
For several years a Lawrence Berkeley National
Laboratory (LBNL) and Lawrence Livermore National
Laboratory (LLNL) collaboration has studied rf power sources
based on the RK-TBA concept . This effort has included
both experiments  and theoretical studies. A preliminary
design study for a rf power source using the RK-TBA concept
suitable for an rf power source upgrade of the NLC collider
design (TBNLC) has been published . The design
specifically addressed issues related to cost, efficiency, and
technical issues. For a 1.5-TeV center-of-mass energy design,
the if power source is comprised of 76 subunits, each about
340 m in length with 150 extraction structures generating
360 MW per structure. Estimated conversion efficiency of
wall plug energy to rf energy for this source could be greater
than 40%. Theory and simulations showed acceptable drive
beam stability through the relativistic klystron, and no
insurmountable technological issues were uncovered.
We have established the RTA test facility  at LBNL to
verify the analysis used in the design study. The principle
effort is constructing a rf power source prototype where all
major components of the TBNLC rf power source will be
tested. The different sections of the RTA are described in
Table 1. Due to fiscal constraints, the RTA will have only
8 rf extraction structures. Table 2 is a comparison between
the pertinent parameters for TBNLC and the RTA. The pulsed
power system and induction cells in the extraction section
will be similar for both machines, allowing a demonstration
of the wall-plug power to drive beam power conversion
efficiency and establishing a basis for costing of the
*The work was perform under the auspices of the U.S.
Department of Energy by LLNL-under contract W-7405-ENG-
48, by LBNL under contract AC03-76SF00098, and by FAR
under SBIR grant FG03-96ER82179.
RTA Accelerator Sections
Beam Current f Sectio
Section Energy (a) current Length
Electron gun 1 1.2 0 3
Accelerator 2.8 1.2 0 8
Chopper 2.8 0.6 0.5 1
Adiabatic compressor 4 0.6 1.1 4
Extraction section 4 - 0.6 1.1 8
Diagnostic section 0 - - 2
t Beam parameters at the end of the section.
Comparison between RTA and the TBNLC.
Parameter RTA TBNLC
Flat-top 200 ns' 200 ns
Rise Time 100 ns 100 ns
Pre-chopper 1.2 kA 1.2 kA
Extraction Sec.(dc) 600 A 600 A
Extraction Sec.(rf) 1.1 kA 1.1 kA
Injector 1 MeV 1 MeV
Chopper 2.8 MeV 2.5 MeV
Extraction 4.0 MeV 10.0 MeV
Bunch Coin ressin 240* to 1100 240* to 70*
Beam trasprtin the
BetatronPeriod 1 im 2 m
Lattice Period 20 cm 33.3 cm
Phase Advance 720 600
Occupancy 0.5 0.48
Pole Tip Field 870 G 812 G
Beam Diameter 8 mm 4 mm
Frequency 11.4 GHz 11.4 GHz
Power/Structure 180 MW 360 MW
Structures SW &TW 3-cell TW
Output Spacing 1 m 2 m
Pulsed Power System
Conversion of wall plug power into induction drive beam
power is a significant factor in the if power source efficiency.
The efficiency of a TBA induction accelerator depends on
several factors. Beam transport dynamics will determine the
size of the beam pipe. The if power requirement determines
the pulse duration, beam current, accelerating gradient, and
repetition rate. Once these factors are established, the outer
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Westenskow, G.A.; Houck, T.L. & Anderson, D. Relativistic Klystron Two-Beam Accelerator studies at the RTA test facility, article, August 16, 1996; California. (digital.library.unt.edu/ark:/67531/metadc675081/m1/4/: accessed October 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.