PAC2013 - List of Authors (Li, Z.)

Paper	Title	Page
MOPBA18	Multipacting Simulation of Accelerator Cavities using ACE3P	216
	C.-K. Ng, L. Ge, C. Ko, Z. Li, L. Xiao SLAC, Menlo Park, California, USA
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515. ACE3P is a 3D parallel finite element code suite for cavity design and optimization including electromagnetic, thermal and mechanical effects. Taking advantages of the power of computing on multi processors, ACE3P's particle tracking module Track3P allows efficient multipacting (MP) simulation by extensive scanning in field gradient and on cavity surface to identify the occurrences of MP activities. The output from Track3P simulation includes the determination of resonant trajectories and their locations, the calculation of electron impact energy on cavity surface, and the evaluation of the electron enhancement counter as a function of field gradient. The sensitivity of MP on secondary emission yield can be readily obtained through postprocessing. Examples of Track3P MP simulation for the Muon cooling cavities and APS SPX cavity will be presented.

WEPAC40	Mechanical Analysis of the 400 MHz RF-Dipole Crabbing Cavity Prototype for LHC High Luminosity Upgrade	862
	S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA S.U. De Silva, J.R. Delayen, H. Park JLAB, Newport News, Virginia, USA Z. Li SLAC, Menlo Park, California, USA
	The proposed LHC high luminosity upgrade requires two crabbing systems in increasing the peak luminosity, operating both vertically and horizontally at two interaction points of IP1 and IP5. The required system has tight dimensional constraints and needs to achieve higher operational gradients. A proof-of-principle 400 MHz crabbing cavity design has been successfully tested and has proven to be an ideal candidate for the crabbing system. The cylindrical proof-of-principle rf-dipole design has been adapted in to a square shaped design to further meet the dimensional requirements. The new rf-dipole design has been optimized in meeting the requirements in rf-properties, higher order mode damping, and multipole components. A crabbing system in a cryomodule is expected to be tested on the SPS beam line prior to the test at LHC. The new prototype is required to achieve the mechanical and thermal specifications of the SPS test followed by the test at LHC. This paper discusses the detailed mechanical and thermal analysis in minimizing Lorentz force detuning and sensitivity to liquid He pressure fluctuations.

WEPAC43	Study of Cavity Imperfection Impact on RF-Parameters and Multipole Components in a Superconducting RF-Dipole Cavity	871
	R.G. Olave, S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA Z. Li SLAC, Menlo Park, California, USA
	Funding: This work is funded by the US/LHC LARP program. The ODU/SLAC superconducting rf-dipole cavity is under consideration for the crab-crossing system in the upcoming LHC luminosity upgrade. While the proposed cavity complies well within the rf-parameters and multipolar component restrictions for the LHC system, cavity imperfections arising from cavity fabrication, welding and frequency tuning may have a significant effect in these parameters. We report on an initial study of the impact of deviation from the ideal shape on the cavity’s performance in terms of rf-parameters and multipolar components.

WEPAC44	Higher Order Modes Damping and Multipacting Analysis for the SPX Deflecting Cavity in APS Upgrade	874
	C.-K. Ng, Z. Li, L. Xiao SLAC, Menlo Park, California, USA A. Nassiri, G.J. Waldschmidt, G. Wu ANL, Argonne, USA R.A. Rimmer, H. Wang JLAB, Newport News, Virginia, USA
	Funding: Work supported by US DOE under contract number DE-AC02-06CH11357. A single-cell superconducting deflecting cavity operating at 2.815 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source (APS) upgrade. Each deflecting cavity is equipped with one fundamental power coupler (FPC), one lower order mode (LOM) coupler, and two higher order mode (HOM) couplers to achieve the stringent damping requirements for the unwanted modes. Using the electromagnetic simulation suite ACE3P, HOM damping will be calculated for the cavity including the full engineering design waveguide configurations and rf windows. Trapped modes in the bellows located in the beampipes connecting the cavities in a cryomodule will be computed and their effects on heating evaluated. Furthermore, multipacting activities at the end groups of the cavity will be identified to assess possible problems during high power processing.

Paper

Title

Page

Multipacting Simulation of Accelerator Cavities using ACE3P

216

C.-K. Ng, L. Ge, C. Ko, Z. Li, L. Xiao
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
ACE3P is a 3D parallel finite element code suite for cavity design and optimization including electromagnetic, thermal and mechanical effects. Taking advantages of the power of computing on multi processors, ACE3P's particle tracking module Track3P allows efficient multipacting (MP) simulation by extensive scanning in field gradient and on cavity surface to identify the occurrences of MP activities. The output from Track3P simulation includes the determination of resonant trajectories and their locations, the calculation of electron impact energy on cavity surface, and the evaluation of the electron enhancement counter as a function of field gradient. The sensitivity of MP on secondary emission yield can be readily obtained through postprocessing. Examples of Track3P MP simulation for the Muon cooling cavities and APS SPX cavity will be presented.

WEPAC40

Mechanical Analysis of the 400 MHz RF-Dipole Crabbing Cavity Prototype for LHC High Luminosity Upgrade

862

S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
S.U. De Silva, J.R. Delayen, H. Park
JLAB, Newport News, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA

The proposed LHC high luminosity upgrade requires two crabbing systems in increasing the peak luminosity, operating both vertically and horizontally at two interaction points of IP1 and IP5. The required system has tight dimensional constraints and needs to achieve higher operational gradients. A proof-of-principle 400 MHz crabbing cavity design has been successfully tested and has proven to be an ideal candidate for the crabbing system. The cylindrical proof-of-principle rf-dipole design has been adapted in to a square shaped design to further meet the dimensional requirements. The new rf-dipole design has been optimized in meeting the requirements in rf-properties, higher order mode damping, and multipole components. A crabbing system in a cryomodule is expected to be tested on the SPS beam line prior to the test at LHC. The new prototype is required to achieve the mechanical and thermal specifications of the SPS test followed by the test at LHC. This paper discusses the detailed mechanical and thermal analysis in minimizing Lorentz force detuning and sensitivity to liquid He pressure fluctuations.

WEPAC43

Study of Cavity Imperfection Impact on RF-Parameters and Multipole Components in a Superconducting RF-Dipole Cavity

871

R.G. Olave, S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA

Funding: This work is funded by the US/LHC LARP program.
The ODU/SLAC superconducting rf-dipole cavity is under consideration for the crab-crossing system in the upcoming LHC luminosity upgrade. While the proposed cavity complies well within the rf-parameters and multipolar component restrictions for the LHC system, cavity imperfections arising from cavity fabrication, welding and frequency tuning may have a significant effect in these parameters. We report on an initial study of the impact of deviation from the ideal shape on the cavity’s performance in terms of rf-parameters and multipolar components.

WEPAC44

Higher Order Modes Damping and Multipacting Analysis for the SPX Deflecting Cavity in APS Upgrade

874

C.-K. Ng, Z. Li, L. Xiao
SLAC, Menlo Park, California, USA
A. Nassiri, G.J. Waldschmidt, G. Wu
ANL, Argonne, USA
R.A. Rimmer, H. Wang
JLAB, Newport News, Virginia, USA

Funding: Work supported by US DOE under contract number DE-AC02-06CH11357.
A single-cell superconducting deflecting cavity operating at 2.815 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source (APS) upgrade. Each deflecting cavity is equipped with one fundamental power coupler (FPC), one lower order mode (LOM) coupler, and two higher order mode (HOM) couplers to achieve the stringent damping requirements for the unwanted modes. Using the electromagnetic simulation suite ACE3P, HOM damping will be calculated for the cavity including the full engineering design waveguide configurations and rf windows. Trapped modes in the bellows located in the beampipes connecting the cavities in a cryomodule will be computed and their effects on heating evaluated. Furthermore, multipacting activities at the end groups of the cavity will be identified to assess possible problems during high power processing.