NAPAC2022 - List of Authors (Li, Z.)

Paper	Title	Page
TUPA80	Cyborg Beamline Development Updates	512
	G.E. Lawler, A. Fukasawa, N. Majernik, J.R. Parsons, J.B. Rosenzweig, Y. Sakai UCLA, Los Angeles, California, USA F. Bosco Sapienza University of Rome, Rome, Italy Z. Li, S.G. Tantawi SLAC, Menlo Park, California, USA B. Spataro LNF-INFN, Frascati, Italy
	Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409. Xray free electron laser (XFEL) facilities in their current form are large, costly to maintain, and inaccessible due to their minimal supply and high demand. It is then advantageous to consider miniaturizing XFELs through a variety of means. We hope to increase beam brightness from the photoinjector via high gradient operation (>120 MV/m) and cryogenic temperature operation at the cathode (<77K). To this end we have designed and fabricated our new CrYogenic Brightness-Optimized Radiofrequency Gun (CYBGORG). The photogun is 0.5 cell so much less complicated than our eventual 1.6 cell photoinjector. It will serve as a prototype and test bed for cathode studies in a new cryogenic and very high gradient regime. We present here the fabricated structure, progress towards commissioning, and beamline simulations.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA80
About •	Received ※ 02 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 09 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPA81	Design of a High-Power RF Breakdown Test for a Cryocooled C-Band Copper Structure	516
	G.E. Lawler, A. Fukasawa, J.R. Parsons, J.B. Rosenzweig UCLA, Los Angeles, California, USA Z. Li, S.G. Tantawi SLAC, Menlo Park, California, USA A. Mostacci Sapienza University of Rome, Rome, Italy E.I. Simakov, T. Tajima LANL, Los Alamos, New Mexico, USA B. Spataro LNF-INFN, Frascati, Italy
	Funding: This work was supported by the DOE Contract DE-SC0020409. High-gradient RF structures capable of maintaining gradients in excess of 250 MV/m are critical in several concepts for future electron accelerators. Concepts such as the ultra-compact free electron laser (UC-XFEL) and the Cool Copper Collider (C3) plan to obtain these gradients through the cryogenic operation (<77K) of normal conducting copper cavities. Breakdown rates, the most significant gradient limitation, are significantly reduced at these low temperatures, but the precise physics is complex and involves many interacting effects. High-power RF breakdown measurements at cryogenic temperatures are needed at the less explored C-band frequency (5.712 GHz), which is of great interest for the aforementioned concepts. On behalf of a large collaboration of UCLA, SLAC, LANL, and INFN, the first C-band cryogenic breakdown measurements will be made using a LANL RF test infrastructure. The 2-cell geometry designed for testing will be modifications of the distributed coupled reentrant design used to efficiently power the cells while staying below the limiting values of peak surface electric and magnetic fields.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA81
About •	Received ※ 29 July 2022 — Accepted ※ 02 August 2022 — Issue date ※ 08 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA09	A Parallel Automatic Simulation Tool for Cavity Shape Optimization	634
	L. Ge, Z. Li, C.-K. Ng, L. Xiao SLAC, Menlo Park, California, USA M. Beall, B.R. Downie, O. Klaas Simmetrix Inc., Clifton Park, USA
	Funding: U.S. Department of Energy under contract No. DE-SC0018715. We present a parallel automatic shape optimization workflow for designing accelerator cavities. The newly developed 3D parallel optimization tool Opt3P based on discrete adjoint methods is used to determine the optimal accelerator cavity shape with the desired spectral response. Initial and updated models, meshes, and design velocities of design parameters for defining the cavity shape are generated with Simmetrix tools for mesh generation (MeshSim), geometry modification and query (GeomSim), and user interface tools (SimModeler). Two shape optimization examples using this automatic simulation workflow will be presented here. One is the TESLA cavity with higher-order-mode (HOM) couplers and the other is a superconducting rf (SRF) gun. The objective for the TESLA cavity is to minimize HOM damping factors and for the SRF gun to minimize the surface electric and magnetic fields while maintaining its operating mode frequency at a prescribed value. The results demonstrate that the automatic simulation tool allows an efficient shape optimization procedure with minimal manual operations. All simulations were performed on the NERSC supercomputer Cori system for solution speedup.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA09
About •	Received ※ 03 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 08 October 2022
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WEPA26	197 MHz Waveguide Loaded Crabbing Cavity Design for the Electron-Ion Collider	679
	S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA J. Guo, R.A. Rimmer JLab, Newport News, Virginia, USA Z. Li SLAC, Menlo Park, California, USA B.P. Xiao BNL, Upton, New York, USA
	The Electron-Ion Collider will require crabbing systems at both hadron and electron storage rings in order to reach the desired luminosity goal. The 197 MHz crab cavity system is one of the critical rf systems of the col-lider. The crab cavity, based on the rf-dipole design, ex-plores the option of waveguide load damping to suppress the higher order modes and meet the tight impedance specifications. The cavity is designed with compact dog-bone waveguides with transitions to rectangular wave-guides and waveguide loads. This paper presents the compact 197 MHz crab cavity design with waveguide damping and other ancillaries.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA26
About •	Received ※ 08 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 06 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Cyborg Beamline Development Updates

512

G.E. Lawler, A. Fukasawa, N. Majernik, J.R. Parsons, J.B. Rosenzweig, Y. Sakai
UCLA, Los Angeles, California, USA
F. Bosco
Sapienza University of Rome, Rome, Italy
Z. Li, S.G. Tantawi
SLAC, Menlo Park, California, USA
B. Spataro
LNF-INFN, Frascati, Italy

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409.
Xray free electron laser (XFEL) facilities in their current form are large, costly to maintain, and inaccessible due to their minimal supply and high demand. It is then advantageous to consider miniaturizing XFELs through a variety of means. We hope to increase beam brightness from the photoinjector via high gradient operation (>120 MV/m) and cryogenic temperature operation at the cathode (<77K). To this end we have designed and fabricated our new CrYogenic Brightness-Optimized Radiofrequency Gun (CYBGORG). The photogun is 0.5 cell so much less complicated than our eventual 1.6 cell photoinjector. It will serve as a prototype and test bed for cathode studies in a new cryogenic and very high gradient regime. We present here the fabricated structure, progress towards commissioning, and beamline simulations.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA80

About •

Received ※ 02 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 09 October 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPA81

Design of a High-Power RF Breakdown Test for a Cryocooled C-Band Copper Structure

516

G.E. Lawler, A. Fukasawa, J.R. Parsons, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
Z. Li, S.G. Tantawi
SLAC, Menlo Park, California, USA
A. Mostacci
Sapienza University of Rome, Rome, Italy
E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA
B. Spataro
LNF-INFN, Frascati, Italy

Funding: This work was supported by the DOE Contract DE-SC0020409.
High-gradient RF structures capable of maintaining gradients in excess of 250 MV/m are critical in several concepts for future electron accelerators. Concepts such as the ultra-compact free electron laser (UC-XFEL) and the Cool Copper Collider (C3) plan to obtain these gradients through the cryogenic operation (<77K) of normal conducting copper cavities. Breakdown rates, the most significant gradient limitation, are significantly reduced at these low temperatures, but the precise physics is complex and involves many interacting effects. High-power RF breakdown measurements at cryogenic temperatures are needed at the less explored C-band frequency (5.712 GHz), which is of great interest for the aforementioned concepts. On behalf of a large collaboration of UCLA, SLAC, LANL, and INFN, the first C-band cryogenic breakdown measurements will be made using a LANL RF test infrastructure. The 2-cell geometry designed for testing will be modifications of the distributed coupled reentrant design used to efficiently power the cells while staying below the limiting values of peak surface electric and magnetic fields.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA81

About •

Received ※ 29 July 2022 — Accepted ※ 02 August 2022 — Issue date ※ 08 August 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA09

A Parallel Automatic Simulation Tool for Cavity Shape Optimization

634

L. Ge, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA
M. Beall, B.R. Downie, O. Klaas
Simmetrix Inc., Clifton Park, USA

Funding: U.S. Department of Energy under contract No. DE-SC0018715.
We present a parallel automatic shape optimization workflow for designing accelerator cavities. The newly developed 3D parallel optimization tool Opt3P based on discrete adjoint methods is used to determine the optimal accelerator cavity shape with the desired spectral response. Initial and updated models, meshes, and design velocities of design parameters for defining the cavity shape are generated with Simmetrix tools for mesh generation (MeshSim), geometry modification and query (GeomSim), and user interface tools (SimModeler). Two shape optimization examples using this automatic simulation workflow will be presented here. One is the TESLA cavity with higher-order-mode (HOM) couplers and the other is a superconducting rf (SRF) gun. The objective for the TESLA cavity is to minimize HOM damping factors and for the SRF gun to minimize the surface electric and magnetic fields while maintaining its operating mode frequency at a prescribed value. The results demonstrate that the automatic simulation tool allows an efficient shape optimization procedure with minimal manual operations. All simulations were performed on the NERSC supercomputer Cori system for solution speedup.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA09

About •

Received ※ 03 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 08 October 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA26

197 MHz Waveguide Loaded Crabbing Cavity Design for the Electron-Ion Collider

679

S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
J. Guo, R.A. Rimmer
JLab, Newport News, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
B.P. Xiao
BNL, Upton, New York, USA

The Electron-Ion Collider will require crabbing systems at both hadron and electron storage rings in order to reach the desired luminosity goal. The 197 MHz crab cavity system is one of the critical rf systems of the col-lider. The crab cavity, based on the rf-dipole design, ex-plores the option of waveguide load damping to suppress the higher order modes and meet the tight impedance specifications. The cavity is designed with compact dog-bone waveguides with transitions to rectangular wave-guides and waveguide loads. This paper presents the compact 197 MHz crab cavity design with waveguide damping and other ancillaries.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA26

About •

Received ※ 08 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 06 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)