The Klynac concept integrates an electron gun, a radio frequency (RF) power source, and a coupled-cavity linear accelerator into a single resonant syste

Potter, J. M., Schwellenbach, D., Meidinger, A.

UNT Digital Library

Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator The Klynac: An Integrated Klystron and Linear Accelerator James M. Potter JP Accelerator Works, Inc., Los Alamos, NM  David Schwellenbach, Alfred Meidinger National Security Technologies, LLC, Los Alamos, NM  For CAARI August 5‒10, 2012  This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy and supported by the Site-Directed Research and Development Program.  DOE/NV/25946--1587 -1- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Klynac Concept • The Klynac concept integrates: – an electron gun,  – a radio frequency (RF) power source,  – a coupled-cavity linear accelerator • into a single resonant system.  -2- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Klynac Overview • Gun—Established technology • Klystron (RF Source)—Established technology • RF Linac—Established technology • Innovative Coupler: Linac and RF source are an integrated system -3- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Klynac Coupler • The Klynac uses: – a unique cavity structure to resonantly couple the klystron output cavity to the accelerator cavities, – locking the two in amplitude and phase, – and eliminating the normal transmission line between klystron and accelerator.  -4- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Klynac Coupler Concept The coupler is a TEM (coaxial) cavity tuned to transmit RF power and resonantly couple the klystron output cavity to the accelerator input cavity -5- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Resonant Coupling • The resonant coupling concept was developed at Los Alamos in the early days of the LANSCE (LAMPF) accelerator design • The LAMPF design had a coupling resonator that was off axis. It was called a “side-coupled”  structure. • The on-axis coupled accelerator structure was conceived at the same time  -6- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator On-Axis Coupled Linac Cell On-axis coupled accelerator structure Accelerating cell Coupling slot Nose Beam aperture Coupling cell -7- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Coupled Circuit Model Half accelerating cavity Coupling slot Coupling cavity -8- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Coupled Circuit Analysis • In the perfectly tuned case, the π/2 mode frequency is the frequency for which I2 = 0.  • This requires that                       ,                           and • Then the π/2 mode frequency is ω1.  • The coupling factors are                        and                          .   • The currents I1 and I4 have the opposite sense and                        .  11 11L Cω = 22 21L Cω = 1 2ω ω=121 212ML Lk = 343 434ML Lk =34 4 12 1k I k I= −-9- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Transmission Line Added • Transmission line • Arbitrary two-port network -10- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Chain Matrix Representation • Chain matrix representation of coaxial transmission line • ϑ is the electrical length of the line •     is the physical length of the line •     is the characteristic impedance of the line 00cos( ) sin( )sin( ) cos( )jZA BM jC DZϑ ϑϑ ϑ= =cωϑ = 0Z-11- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator If Line Electrical Length is a Multiple of π •   • The amplitude relation is now ( 1) 00 ( 1)NNM−=−Nϑ π=34 4 12 1( 1)Nk I k I= − −-12- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator More General Case • C2 and C3 have been removed  • For I2 = I3 = 0 we get 1 2 31 ( )0 0j L LMω− +=-13- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Form of the Matrix M • The matrix M must contain a series impedance that resonates with the coupling slot self inductances at frequency ω1. • This could be the equivalent of the circuit of Slide 10, with series capacitances and a transmission line of electrical length               . • Or, it could be a more complex circuit. Nϑ π=-14- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Coupler Network Properties • The network has to have the property that the currents I2 = I3 = 0 in the accelerating  π/2 mode, ωπ/2  = ω1 and the currents I1 = I4 = 0 in the coupling π/2 mode, ω’π/2  = ω1. • The accelerating mode is calculated with short circuit boundaries as illustrated in Slide 13. • The coupling mode is calculated with open circuit boundaries. -15- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Circuit Model with Open Circuit Boundaries For a periodic structure the resonant frequency is the mode with stored energy in the coupling mode and no stored energy in the accelerating mode -16- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator HFSS Model of a Coupler -17- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator • The rings on the outer conductor labeled transmission mode tuners capacitively load the coaxial line so that the short circuit mode resonates at the operating frequency  • The rings on the inner conductor labeled coupling mode tuners capacitively load the coaxial line so that the open circuit mode resonates at the operating frequency -18- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Tilt Sensitivity Method 1 • The tuning of the accelerating mode can be done by direct measurement • The coupling mode is tuned by an indirect measurement • The relative amplitudes of the resonators on each side of the coupler is measured with the resonators detuned -19- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Tilt Sensitivity Measurement 2 • One measurement is made with one end tuned high and the other end tuned low keeping the frequency constant • Then the tuning errors are reversed • The change in the amplitude ratio is plotted against the frequency of the coupling mode • When reversing the error produces no change in the field ratio the coupler is tuned  -20- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Coupling Mode Frequency The coupling mode frequency can be calculated with HFSS as a function of tuner radius. -21- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Tilt Sensitivity versus Coupler Frequency   -22- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator Tilt Sensitivity Technique • For several values of the coupler frequency the tilt sensitivity is measured for several tuning errors • For moderately small tuning errors the tilt sensitivity is linear in the tuning error • It is also linear in the error in the coupler frequency • The tilt sensitivity vanishes when the coupler is tuned -23- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator E-Fields in Operating Mode • Logarithmic field plot • Quadrant with      symmetry planes • Half cells at ends • Short circuit end      boundaries • Equal amplitudes  in end cells • Voltage across slots      equal at each end • Open circuit      transmission line mode  -24- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator E-Fields in Coupling Mode • Logarithmic field plot • Open circuit boundaries • Transmission line       terminated by slot      self inductance • Mode must be at same      frequency as main mode      for resonant coupling • Resonant coupling – Reduces sensitivity of     field distribution to     tuning errors  -25- Vision – Service – Partnership Managed and Operated by National Security Technologies, LLC Nevada National Security Site The Klynac: An Integrated Klystron and Linear Accelerator What Next? • We have demonstrated that we can make a suitable resonant power coupler of whatever length is required • We need to do beam dynamics calculations to show that we can get some fraction of the klystron beam to the accelerator at the right phase • Then we build a cold model to perfect tuning techniques • Next we would build a full prototype to demonstrate performance -26- 

The Klynac: An Integrated Klystron and Linear Accelerator

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