IPAC2012 - List of Authors (Waldschmidt, G.J.)

Paper	Title	Page
MOPPR069	Use of Waveguide and Beam Pipe Probes as Beam Position and Tilt Monitoring Diagnostics with Superconducting Deflecting Cavities	945
	X. Sun, T.G. Berenc, G. Decker, G.J. Waldschmidt, G. Wu ANL, Argonne, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357. Waveguide and beam pipe field probes associated with a superconducting deflecting cavity are explored as beam position and tilt monitoring diagnostics. The superconducting deflecting cavity will be used for the Short-pulse X-rays (SPX) in the Advanced Photon Source (APS) upgrade project. Microwave Studio will be used to simulate the techniques of detecting the fields excited by the beam passing through the cavity and determining how close the beam is on electrical center.

WEPPC040	Evaluation of VATSEAL Technology to Seal Waveguide Serving High-field Superconducting RF Cavities	2298
	B.K. Stillwell, J.D. Fuerst, J. Liu, G.J. Waldschmidt, G. Wu ANL, Argonne, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. A waveguide flange seal serving a high-field, superconducting, radio-frequency (SRF) cavity ideally possesses several characteristics. Seals must generally be ultrahigh-vacuum leak tight. Seals must also bridge the inner surfaces of connecting flanges for optimum transmission and minimal heating due to trapped modes. In addition, if seal contact areas are minimized, flange seals may serve as convenient thermal impedances. Finally, seals must be easily cleanable and not be prone to generate particulate matter during assembly and disassembly. A unique sealing technology known as VATSEAL may neatly address all of the above requirements. In this paper, we describe our evaluation of VATSEAL technology for use in SRF cavity assemblies.

WEPPC042	Low Impedance Bellows for High-current Beam Operations	2303
	G. Wu, K.-J. Kim, A. Nassiri, G.J. Waldschmidt, Y. Yang ANL, Argonne, USA J.J. Feingold, J.D. Mammosser, R.A. Rimmer, H. Wang JLAB, Newport News, Virginia, USA J. Jang, S.H. Kim POSTECH, Pohang, Kyungbuk, Republic of Korea
	Funding: Work Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357 In particle accelerators, bellows are commonly used to connect beamline components. Such bellows are traditionally shielded to lower the beam impedance. Excessive beam impedance can cause overheating in the bellows, especially in high beam current operation. For an SRF-based accelerator, the bellows must also be particulate free. Many designs of shielded bellows incorporate rf slides or fingers that prevent convolutions from being exposed to wakefields. Unfortunately these mechanical structures tend to generate particulates that, if left in the SRF accelerator, can migrate into superconducting cavities, the accelerator's critical components. In this paper, we describe a prototype unshielded bellows that has low beam impedance and no risk of particulate generation.

WEPPC086	Higher Order Modes Damping Analysis for the SPX Deflecting Cavity Cyromodule	2414
	L. Xiao, Z. Li, C.-K. Ng 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 the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. A single-cell superconducting deflecting cavity operating at 2.812 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source upgrade. A cryomodule of 4 such cavities will be needed to produce the required 2-MV deflecting voltage. 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. The damping of the HOM/LOM modes below the beampipe cutoff has been analyzed in the single cavity geometry and shown to meet the design requirements. The HOMs above beam pipe cutoff in the 4-cavity cyromodule, however, may result in cross coupling which may affect the HOM damping and potentially trapped modes between the cavities which could produce RF heating to the beamline bellows and even be detrimental to the beam. We have evaluated the HOM damping and trapped modes in the 4-cavity cryomodule using the parallel finite element EM code ACE3P developed at SLAC. We will present the results of the cryomodule analysis in this paper.

WEPPC038	Status of the Short-Pulse X-ray Project at the Advanced Photon Source	2292
	A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, A.E. Grelick, D. Horan, J. Kaluzny, F. Lenkszus, R.M. Lill, J. Liu, H. Ma, V. Sajaev, T.L. Smith, B.K. Stillwell, G.J. Waldschmidt, G. Wu, B.X. Yang, Y. Yang, A. Zholents ANL, Argonne, USA J.M. Byrd, L.R. Doolittle, G. Huang LBNL, Berkeley, California, USA G. Cheng, G. Ciovati, P. Dhakal, G.V. Eremeev, J.J. Feingold, R.L. Geng, J. Henry, P. Kneisel, K. Macha, J.D. Mammosser, J. Matalevich, A.D. Palczewski, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman JLAB, Newport News, Virginia, USA Z. Li, L. Xiao SLAC, Menlo Park, California, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source Upgrade (APS-U) Project at Argonne will include generation of short-pulse x-rays based on Zholents’* deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. In collaboration with Jefferson Laboratory, we are prototyping and testing a number of single-cell deflecting cavities and associated auxiliary systems with promising initial results. In collaboration with Lawrence Berkeley National Laboratory, we are working to develop state-of-the-art timing, synchronization, and differential rf phase stability systems that are required for SPX. Collaboration with Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi-cavity geometries with lower- and higher-order modes waveguide dampers using ACE3P. This contribution provides the current R&D status of the SPX project. * A. Zholents et al., NIM A 425, 385 (1999).

THPPC029	High-power Waveguide Dampers for the Short-Pulse X-Ray Project at the Advanced Photon Source	3344
	G.J. Waldschmidt, B. Brajuskovic, J. Liu, M.E. Middendorf, A. Nassiri, T.L. Smith, G. Wu ANL, Argonne, USA J. Henry, J.D. Mammosser, R.A. Rimmer, M. Wiseman JLAB, Newport News, Virginia, USA
	Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. High-power waveguide dampers have been designed and prototyped for the Short-Pulse X-ray (SPX) cavities at the Advanced Photon Source. The cavities will operate at 2.815 GHz and utilize the TM110 dipole mode. As a result, higher-order (HOM) and lower-order mode (LOM) in-vacuum dampers have been designed to satisfy the demanding broadband damping requirements in the APS storage ring. The SPX single-cell cavity consists of two WR284 waveguides for damping the HOMs and one WR284 waveguide for primarily damping the LOM where up to 2kW will be dissipated in the damping material. The damper designs and high-power experimental results will be discussed in this paper.

WEPPR083	New Sector 37 Chamber Design and Installation for High-Current Operation of the APS Storage Ring	3123
	Y.-C. Chae, R. Bechtold, W. Berg, L. Erwin, M. Givens, J.E. Hoyt, L.H. Morrison, K.M. Schroeder, R. Soliday, J.B. Stevens, G.J. Waldschmidt ANL, Argonne, USA
	Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357. The Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source consisting of 40 sectors. Sector 37 accommodates four radio-frequency cavities followed by a short straight section, which is set aside for the future installation of a diagnostic device. The 60-cm-long section of spool pieces can be isolated by two gate valves and has an independent vacuum pump. The spool pieces are normally under high vacuum condition when the total current is below 100 mA. However, at the higher current required for the APS Upgrade, rf heating causes an unacceptable rise in temperature. We analyzed this situation by wakefield simulation, which led to a new chamber design. Proper fabrication and careful installation with twelve thermocouples ensured a temperature rise under 40-50 degrees Celsius at 100 mA. A brief thermal analysis shows that the present observed temperature rise in the new chamber is mainly due to the resistive wall.

Paper

Title

Page

Use of Waveguide and Beam Pipe Probes as Beam Position and Tilt Monitoring Diagnostics with Superconducting Deflecting Cavities

945

X. Sun, T.G. Berenc, G. Decker, G.J. Waldschmidt, G. Wu
ANL, Argonne, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357.
Waveguide and beam pipe field probes associated with a superconducting deflecting cavity are explored as beam position and tilt monitoring diagnostics. The superconducting deflecting cavity will be used for the Short-pulse X-rays (SPX) in the Advanced Photon Source (APS) upgrade project. Microwave Studio will be used to simulate the techniques of detecting the fields excited by the beam passing through the cavity and determining how close the beam is on electrical center.

WEPPC040

Evaluation of VATSEAL Technology to Seal Waveguide Serving High-field Superconducting RF Cavities

2298

B.K. Stillwell, J.D. Fuerst, J. Liu, G.J. Waldschmidt, G. Wu
ANL, Argonne, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A waveguide flange seal serving a high-field, superconducting, radio-frequency (SRF) cavity ideally possesses several characteristics. Seals must generally be ultrahigh-vacuum leak tight. Seals must also bridge the inner surfaces of connecting flanges for optimum transmission and minimal heating due to trapped modes. In addition, if seal contact areas are minimized, flange seals may serve as convenient thermal impedances. Finally, seals must be easily cleanable and not be prone to generate particulate matter during assembly and disassembly. A unique sealing technology known as VATSEAL may neatly address all of the above requirements. In this paper, we describe our evaluation of VATSEAL technology for use in SRF cavity assemblies.

WEPPC042

Low Impedance Bellows for High-current Beam Operations

2303

G. Wu, K.-J. Kim, A. Nassiri, G.J. Waldschmidt, Y. Yang
ANL, Argonne, USA
J.J. Feingold, J.D. Mammosser, R.A. Rimmer, H. Wang
JLAB, Newport News, Virginia, USA
J. Jang, S.H. Kim
POSTECH, Pohang, Kyungbuk, Republic of Korea

Funding: Work Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357
In particle accelerators, bellows are commonly used to connect beamline components. Such bellows are traditionally shielded to lower the beam impedance. Excessive beam impedance can cause overheating in the bellows, especially in high beam current operation. For an SRF-based accelerator, the bellows must also be particulate free. Many designs of shielded bellows incorporate rf slides or fingers that prevent convolutions from being exposed to wakefields. Unfortunately these mechanical structures tend to generate particulates that, if left in the SRF accelerator, can migrate into superconducting cavities, the accelerator's critical components. In this paper, we describe a prototype unshielded bellows that has low beam impedance and no risk of particulate generation.

WEPPC086

Higher Order Modes Damping Analysis for the SPX Deflecting Cavity Cyromodule

2414

L. Xiao, Z. Li, C.-K. Ng
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 the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A single-cell superconducting deflecting cavity operating at 2.812 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source upgrade. A cryomodule of 4 such cavities will be needed to produce the required 2-MV deflecting voltage. 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. The damping of the HOM/LOM modes below the beampipe cutoff has been analyzed in the single cavity geometry and shown to meet the design requirements. The HOMs above beam pipe cutoff in the 4-cavity cyromodule, however, may result in cross coupling which may affect the HOM damping and potentially trapped modes between the cavities which could produce RF heating to the beamline bellows and even be detrimental to the beam. We have evaluated the HOM damping and trapped modes in the 4-cavity cryomodule using the parallel finite element EM code ACE3P developed at SLAC. We will present the results of the cryomodule analysis in this paper.

WEPPC038

Status of the Short-Pulse X-ray Project at the Advanced Photon Source

2292

A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, A.E. Grelick, D. Horan, J. Kaluzny, F. Lenkszus, R.M. Lill, J. Liu, H. Ma, V. Sajaev, T.L. Smith, B.K. Stillwell, G.J. Waldschmidt, G. Wu, B.X. Yang, Y. Yang, A. Zholents
ANL, Argonne, USA
J.M. Byrd, L.R. Doolittle, G. Huang
LBNL, Berkeley, California, USA
G. Cheng, G. Ciovati, P. Dhakal, G.V. Eremeev, J.J. Feingold, R.L. Geng, J. Henry, P. Kneisel, K. Macha, J.D. Mammosser, J. Matalevich, A.D. Palczewski, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman
JLAB, Newport News, Virginia, USA
Z. Li, L. Xiao
SLAC, Menlo Park, California, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source Upgrade (APS-U) Project at Argonne will include generation of short-pulse x-rays based on Zholents’* deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. In collaboration with Jefferson Laboratory, we are prototyping and testing a number of single-cell deflecting cavities and associated auxiliary systems with promising initial results. In collaboration with Lawrence Berkeley National Laboratory, we are working to develop state-of-the-art timing, synchronization, and differential rf phase stability systems that are required for SPX. Collaboration with Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi-cavity geometries with lower- and higher-order modes waveguide dampers using ACE3P. This contribution provides the current R&D status of the SPX project.
* A. Zholents et al., NIM A 425, 385 (1999).

THPPC029

High-power Waveguide Dampers for the Short-Pulse X-Ray Project at the Advanced Photon Source

3344

G.J. Waldschmidt, B. Brajuskovic, J. Liu, M.E. Middendorf, A. Nassiri, T.L. Smith, G. Wu
ANL, Argonne, USA
J. Henry, J.D. Mammosser, R.A. Rimmer, M. Wiseman
JLAB, Newport News, Virginia, USA

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
High-power waveguide dampers have been designed and prototyped for the Short-Pulse X-ray (SPX) cavities at the Advanced Photon Source. The cavities will operate at 2.815 GHz and utilize the TM110 dipole mode. As a result, higher-order (HOM) and lower-order mode (LOM) in-vacuum dampers have been designed to satisfy the demanding broadband damping requirements in the APS storage ring. The SPX single-cell cavity consists of two WR284 waveguides for damping the HOMs and one WR284 waveguide for primarily damping the LOM where up to 2kW will be dissipated in the damping material. The damper designs and high-power experimental results will be discussed in this paper.

WEPPR083

New Sector 37 Chamber Design and Installation for High-Current Operation of the APS Storage Ring

3123

Y.-C. Chae, R. Bechtold, W. Berg, L. Erwin, M. Givens, J.E. Hoyt, L.H. Morrison, K.M. Schroeder, R. Soliday, J.B. Stevens, G.J. Waldschmidt
ANL, Argonne, USA

Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357.
The Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source consisting of 40 sectors. Sector 37 accommodates four radio-frequency cavities followed by a short straight section, which is set aside for the future installation of a diagnostic device. The 60-cm-long section of spool pieces can be isolated by two gate valves and has an independent vacuum pump. The spool pieces are normally under high vacuum condition when the total current is below 100 mA. However, at the higher current required for the APS Upgrade, rf heating causes an unacceptable rise in temperature. We analyzed this situation by wakefield simulation, which led to a new chamber design. Proper fabrication and careful installation with twelve thermocouples ensured a temperature rise under 40-50 degrees Celsius at 100 mA. A brief thermal analysis shows that the present observed temperature rise in the new chamber is mainly due to the resistive wall.