IPAC2012 - List of Authors (Ge, L.)

Paper	Title	Page
WEEPPB010	RF Modeling Using Parallel Codes ACE3P for the 400-MHz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity for the LHC HiLumi Upgrade	2185
	Z. Li, L. Ge SLAC, Menlo Park, California, USA J.R. Delayen, S.D. Silva ODU, Norfolk, Virginia, USA
	Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515. Schemes utilizing crab cavities to achieve head-on beam-beam collisions were proposed for the LHC HiLumi upgrade. These crabbing schemes require that the crab cavities be compact in order to fit into the tight spacing available in the existing LHC beamlines at the location where the crab cavities will be installed. Under the support of US LARP program, Old Dominion University and SLAC have joint efforts to develop a 400-MHz compact superconducting crab cavity to meet the HiLumi upgrade requirements. In this paper, we will present the RF modeling and analysis of a parallel-bar/ridged-waveguide shaped 400-MHz compact cavity design that can be used for both the horizontal and vertical crabbing schemes. We will also present schemes for HOM damping and multipacting analysis for such a design.

WEPPC068	Multipacting Simulation and Analysis for the FRIB β = 0.085 Quarter Wave Resonators using Track3P	2366
	L. Ge, C. Ko, Z. Li SLAC, Menlo Park, California, USA J. Popielarski FRIB, East Lansing, Michigan, USA
	Funding: Work supported by DOE Office of Science under Cooperative Agreement DE- SC0000661, DOE Contract No. DE-AC02-76SF00515, and used resources of NERSC supported by DOE Contract No. DE-AC02- 05CH11231. The drive linac for the Facility for Rare Isotope Beams (FRIB) utilizes several types of low beta superconducting resonators to accelerate the ion beams from 0.3 MeV per nucleon to 200 MeV per nucleon. Multipacting is an issue of concern for such superconducting resonators as they have unconventional shapes. We have used the parallel codes Tack3P and Omega3P, developed at SLAC under the support of the DOE SciDAC program, to analyze the multipacting barriers of such resonators. In this paper, we will present the simulation results for the β(v/c) = 0.085 Quarter Wave Resonator (QWR) for the FRIB project. Experimental data will also be presented to benchmark with the simulation results.

WEPPC110	3D Simulations of Multipacting in the 56 MHz SRF Cavity	2477
	Q. Wu, S.A. Belomestnykh BNL, Upton, Long Island, New York, USA L. Ge, C. Ko, Z. Li, C.-K. Ng, L. Xiao SLAC, Menlo Park, California, USA
	Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The 56 MHz SRF Quarter-Wave Resonator (QWR) is designed for RHIC as a storage cavity to improve the collider performance. 2D multipacting simulation has been done for the cavity alone. Ripples were added to the outer body of the cavity for multipacting suppression based on the simulation findings. During operation, there will be four higher order mode (HOM) couplers and a fundamental power coupler (FPC) inserted through the end ports of the cavity and a fundamental mode damper (FD) inserted through a special port on the outer body. All of these components will be exposed to high RF fields. In this presentation we compare 2D and 3D codes simulation results for multipacting in the cavity. We also report 3D simulation results for multipacting simulation at the couplers.

THPPC040	Improved RF Design for an 805 MHz Pillbox Cavity for the US MuCool Program	3371
	Z. Li, C. Adolphsen, L. Ge SLAC, Menlo Park, California, USA D.L. Bowring, D. Li LBNL, Berkeley, California, USA
	Funding: Work supported by US DOE under contract number DE-AC02-05CH11231, and DE-AC02-76SF00515. Normal conducting RF cavities are required to operate at high gradient in the presence of strong magnetic field in muon ionization cooling channels for a Muon Collider. Experimental studies using an 805 MHz pillbox cavity at MTA of Fermilab has shown significant degradation in gradient performance and damage in the regions that are correlated with high RF fields in magnetic field up to 4 Tesla. These effects are believed to be related to the dark current and/or multipacting activities in the presence of external magnetic field. To improve the performance of the cavity, a new RF cavity with significantly lower surface field enhancement was designed, and will be built and tested in the near future. Numerical analyses of multipacting and dark current were performed using the 3D parallel code Track3P for both the original and new improved cavity profiles in order to gain more insight in understanding of the gradient issues under strong external magnetic field. In this paper, we will present the improved RF design and the dark current and multipacting analyses for the 805 MHz cavity.

Paper

Title

Page

RF Modeling Using Parallel Codes ACE3P for the 400-MHz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity for the LHC HiLumi Upgrade

2185

Z. Li, L. Ge
SLAC, Menlo Park, California, USA
J.R. Delayen, S.D. Silva
ODU, Norfolk, Virginia, USA

Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
Schemes utilizing crab cavities to achieve head-on beam-beam collisions were proposed for the LHC HiLumi upgrade. These crabbing schemes require that the crab cavities be compact in order to fit into the tight spacing available in the existing LHC beamlines at the location where the crab cavities will be installed. Under the support of US LARP program, Old Dominion University and SLAC have joint efforts to develop a 400-MHz compact superconducting crab cavity to meet the HiLumi upgrade requirements. In this paper, we will present the RF modeling and analysis of a parallel-bar/ridged-waveguide shaped 400-MHz compact cavity design that can be used for both the horizontal and vertical crabbing schemes. We will also present schemes for HOM damping and multipacting analysis for such a design.

WEPPC068

Multipacting Simulation and Analysis for the FRIB β = 0.085 Quarter Wave Resonators using Track3P

2366

L. Ge, C. Ko, Z. Li
SLAC, Menlo Park, California, USA
J. Popielarski
FRIB, East Lansing, Michigan, USA

Funding: Work supported by DOE Office of Science under Cooperative Agreement DE- SC0000661, DOE Contract No. DE-AC02-76SF00515, and used resources of NERSC supported by DOE Contract No. DE-AC02- 05CH11231.
The drive linac for the Facility for Rare Isotope Beams (FRIB) utilizes several types of low beta superconducting resonators to accelerate the ion beams from 0.3 MeV per nucleon to 200 MeV per nucleon. Multipacting is an issue of concern for such superconducting resonators as they have unconventional shapes. We have used the parallel codes Tack3P and Omega3P, developed at SLAC under the support of the DOE SciDAC program, to analyze the multipacting barriers of such resonators. In this paper, we will present the simulation results for the β(v/c) = 0.085 Quarter Wave Resonator (QWR) for the FRIB project. Experimental data will also be presented to benchmark with the simulation results.

WEPPC110

3D Simulations of Multipacting in the 56 MHz SRF Cavity

2477

Q. Wu, S.A. Belomestnykh
BNL, Upton, Long Island, New York, USA
L. Ge, C. Ko, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA

Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
The 56 MHz SRF Quarter-Wave Resonator (QWR) is designed for RHIC as a storage cavity to improve the collider performance. 2D multipacting simulation has been done for the cavity alone. Ripples were added to the outer body of the cavity for multipacting suppression based on the simulation findings. During operation, there will be four higher order mode (HOM) couplers and a fundamental power coupler (FPC) inserted through the end ports of the cavity and a fundamental mode damper (FD) inserted through a special port on the outer body. All of these components will be exposed to high RF fields. In this presentation we compare 2D and 3D codes simulation results for multipacting in the cavity. We also report 3D simulation results for multipacting simulation at the couplers.

THPPC040

Improved RF Design for an 805 MHz Pillbox Cavity for the US MuCool Program

3371

Z. Li, C. Adolphsen, L. Ge
SLAC, Menlo Park, California, USA
D.L. Bowring, D. Li
LBNL, Berkeley, California, USA

Funding: Work supported by US DOE under contract number DE-AC02-05CH11231, and DE-AC02-76SF00515.
Normal conducting RF cavities are required to operate at high gradient in the presence of strong magnetic field in muon ionization cooling channels for a Muon Collider. Experimental studies using an 805 MHz pillbox cavity at MTA of Fermilab has shown significant degradation in gradient performance and damage in the regions that are correlated with high RF fields in magnetic field up to 4 Tesla. These effects are believed to be related to the dark current and/or multipacting activities in the presence of external magnetic field. To improve the performance of the cavity, a new RF cavity with significantly lower surface field enhancement was designed, and will be built and tested in the near future. Numerical analyses of multipacting and dark current were performed using the 3D parallel code Track3P for both the original and new improved cavity profiles in order to gain more insight in understanding of the gradient issues under strong external magnetic field. In this paper, we will present the improved RF design and the dark current and multipacting analyses for the 805 MHz cavity.