2011 Particle Accelerator Conference - List of Authors (Shin, K.R.)

Paper	Title	Page
MOP257	High Power RF Distribution and Control for Multi-Cavity Cryomodule Testing	591
	Y.W. Kang, M. Broyles, M.T. Crofford, X. Geng, S.-H. Kim, S.W. Lee, C.L. Phibbs, K.R. Shin, W.H. Strong ORNL, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. The SNS has been successfully operating 81 superconducting six-cell cavities in 23 cryomodules in its linac to achieve the goals in beam power and energy. For near-term production of spare cryomodules and the upcoming power upgrade project that will need 36 additional cavities in 9 cryomodules, high RF power testing and qualification of the cavities is required in the RF test facility. Simultaneously powering all the cavities in a cryomodule is considered desirable for robust conditioning and studying of cavity field emission since certain cavities exhibit field emissions that could be mutually coupled. A four-way variable output power waveguide splitting system is being prepared for testing cryomodules with up to four cavities. The splitting system is fed by an 805 MHz, 5 MW peak power pulsed klystron. The power output at each arm can be adjusted in both amplitude and phase to wide ranges of values using two mechanical waveguide phase shifters that form a vector modulator. The system control is implemented in the EPICS environment similar to the main accelerator controls. The work performed on the design, integration, operation, and test of the system are presented.

TUP012	Computer Simulations of Waveguide Window and Coupler Iris for Precision Matching	832
	S.W. Lee ORNL RAD, Oak Ridge, Tennessee, USA Y.W. Kang, K.R. Shin, A.V. Vassioutchenko ORNL, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. A tapered ridge waveguide iris input coupler and a waveguide ceramic disk windows are used on each of six drift tube linac (DTL) cavities in the Spallation Neutron Source (SNS). The coupler design employs rapidly tapered double ridge waveguide to reduce the cross section down to a smaller low impedance transmission line section that can couple to the DTL tank easily. The impedance matching is done by adjusting the dimensions of the thin slit aperture between the ridges that is the coupling element responsible for the power delivery to the cavity. Since the coupling is sensitive to the dimensional changes of the aperture, it requires careful tuning for precise matching. Accurate RF simulation using latest 3-D EM code is desirable to help the tuning for maintenance and spare manufacturing. Simulations are done for the complete system with the ceramic window and the coupling iris on the cavity to see mutual interaction between the components as a whole.

WEP274	Broadband Antenna Matching Network Design and Application for RF Plasma Ion Source	1990
	K.R. Shin ORNL RAD, Oak Ridge, Tennessee, USA A.E. Fathy University of Tennessee, Knoxville, Tennessee, USA Y.W. Kang, M.F. Piller ORNL, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. The RF ion source at Spallation Neutron Source has been upgraded to meet higher beam power requirement. One important subsystem for efficient operation of the ion source is the 2MHz RF impedance matching network. The real part of the antenna impedance is very small and is affected by plasma density for 2MHz operating frequency. Previous impedance matching network for the antenna has limited tuning capability to cover this potential variation of the antenna impedance since it employed a single tuning element and an impedance transformer. A new matching network with two tunable capacitors has been built and tested. This network can allow precision matching and increase the tunable range without using a transformer. A 5-element broadband matching network also has been designed, built and tested. The 5-element network allows wide band matching up to 50 kHz bandwidth from the resonance center of 2 MHz. The design procedure, simulation and test results are presented.

Paper

Title

Page

High Power RF Distribution and Control for Multi-Cavity Cryomodule Testing

591

Y.W. Kang, M. Broyles, M.T. Crofford, X. Geng, S.-H. Kim, S.W. Lee, C.L. Phibbs, K.R. Shin, W.H. Strong
ORNL, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The SNS has been successfully operating 81 superconducting six-cell cavities in 23 cryomodules in its linac to achieve the goals in beam power and energy. For near-term production of spare cryomodules and the upcoming power upgrade project that will need 36 additional cavities in 9 cryomodules, high RF power testing and qualification of the cavities is required in the RF test facility. Simultaneously powering all the cavities in a cryomodule is considered desirable for robust conditioning and studying of cavity field emission since certain cavities exhibit field emissions that could be mutually coupled. A four-way variable output power waveguide splitting system is being prepared for testing cryomodules with up to four cavities. The splitting system is fed by an 805 MHz, 5 MW peak power pulsed klystron. The power output at each arm can be adjusted in both amplitude and phase to wide ranges of values using two mechanical waveguide phase shifters that form a vector modulator. The system control is implemented in the EPICS environment similar to the main accelerator controls. The work performed on the design, integration, operation, and test of the system are presented.

TUP012

Computer Simulations of Waveguide Window and Coupler Iris for Precision Matching

832

S.W. Lee
ORNL RAD, Oak Ridge, Tennessee, USA
Y.W. Kang, K.R. Shin, A.V. Vassioutchenko
ORNL, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
A tapered ridge waveguide iris input coupler and a waveguide ceramic disk windows are used on each of six drift tube linac (DTL) cavities in the Spallation Neutron Source (SNS). The coupler design employs rapidly tapered double ridge waveguide to reduce the cross section down to a smaller low impedance transmission line section that can couple to the DTL tank easily. The impedance matching is done by adjusting the dimensions of the thin slit aperture between the ridges that is the coupling element responsible for the power delivery to the cavity. Since the coupling is sensitive to the dimensional changes of the aperture, it requires careful tuning for precise matching. Accurate RF simulation using latest 3-D EM code is desirable to help the tuning for maintenance and spare manufacturing. Simulations are done for the complete system with the ceramic window and the coupling iris on the cavity to see mutual interaction between the components as a whole.

WEP274

Broadband Antenna Matching Network Design and Application for RF Plasma Ion Source

1990

K.R. Shin
ORNL RAD, Oak Ridge, Tennessee, USA
A.E. Fathy
University of Tennessee, Knoxville, Tennessee, USA
Y.W. Kang, M.F. Piller
ORNL, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The RF ion source at Spallation Neutron Source has been upgraded to meet higher beam power requirement. One important subsystem for efficient operation of the ion source is the 2MHz RF impedance matching network. The real part of the antenna impedance is very small and is affected by plasma density for 2MHz operating frequency. Previous impedance matching network for the antenna has limited tuning capability to cover this potential variation of the antenna impedance since it employed a single tuning element and an impedance transformer. A new matching network with two tunable capacitors has been built and tested. This network can allow precision matching and increase the tunable range without using a transformer. A 5-element broadband matching network also has been designed, built and tested. The 5-element network allows wide band matching up to 50 kHz bandwidth from the resonance center of 2 MHz. The design procedure, simulation and test results are presented.