SRF2011 - List of Authors (Jensen, M.)

Paper	Title	Page
MOIOB05	Operational Experience with SRF Cavities for Light Sources	27
	M. Jensen Diamond, Oxfordshire, United Kingdom
	Third generation light sources require modest accelerating voltages, however this is offset by a need for high reliability, to serve users on a continual basis with minimal interruption. The high Q of the superconducting (SC) cavities means that cavities are designed such that higher order modes are effectively damped using external loads, offering stable high current, multi-bunch operation. Fundamental mode SC cavities for light sources were initially used in CESR and KEKB, followed by Taiwan Light Source and Canadian Light Source and third harmonic systems are used for bunch lengthening at SLS and ELETTRA. The successful operation of those machines led to the choice of SC cavities in the design of Soleil, Diamond Light Source and Shanghai Synchrotron Radiation Facility, all now in operation. Additionally, Taiwan Photon Source, Pohang Light Source II and National Synchrotron Light Source II are currently in construction and all employ SC cavities. In this paper we will review recent operational experience of SC cavities in light sources and will describe recent developments related to the cavities and their auxiliary systems.

MOPO068	Reliability Improvements of the Diamond Superconducting Cavities	267
	P. Gu, M. Jensen, M. Maddock, P.J. Marten, S.A. Pande, S. Rains, A.F. Rankin, D. Spink, A.V. Watkins Diamond, Oxfordshire, United Kingdom
	For successful operation of superconducting cavities in light sources, high reliability and minimal beam losses are essential. Diamond started operation with users in January 2007 and since then, the Diamond storage ring superconducting cavities have been the largest single contributor to unplanned beam trips. We have dedicated extensive effort to improve our data acquisition, numerical modelling and fault analysis to improve our understanding of the main causes of the trips and how to prevent trips or reduce their frequency. In the past seven months, the performance of the cavities has improved significantly. We present here our analysis of some of the trips and their underlying causes and discuss improvements carried out.

THPO010	Multipactor Studies for DIAMOND Storage Ring Cavities	718
	S.A. Pande, M. Jensen Diamond, Oxfordshire, United Kingdom
	The Diamond storage ring is presently operating with two CESR type Superconducting (SC) RF cavities operating at 499.654 MHz. The cavities are suffering from a significant number of trips due to a sudden loss of accelerating field believed to be caused by Multipacting. It is observed that operating the cavities at lower voltages reduces the trip frequency significantly. In order to estimate the multipacting thresholds and to determine safe (multipactor free) parameter zones, we have initiated a detailed simulation study of multipacting in the cavities and the coupling waveguide. The cavities have fixed coupling, and therefore the match of the cavities varies with beam current, radiation loss and cavity voltage. A change in any of these parameters leads to a different standing wave in the waveguide. This requires the simulations to account for the different operating conditions. In addition to the waveguide and the cavity cell, the simulations also indicate the possibility of multipactor in the connecting beam tubes. In this paper, we summarise the results of our simulations obtained using CST Studio PIC and Tracking solvers.

Paper

Title

Page

Operational Experience with SRF Cavities for Light Sources

27

M. Jensen
Diamond, Oxfordshire, United Kingdom

Third generation light sources require modest accelerating voltages, however this is offset by a need for high reliability, to serve users on a continual basis with minimal interruption. The high Q of the superconducting (SC) cavities means that cavities are designed such that higher order modes are effectively damped using external loads, offering stable high current, multi-bunch operation. Fundamental mode SC cavities for light sources were initially used in CESR and KEKB, followed by Taiwan Light Source and Canadian Light Source and third harmonic systems are used for bunch lengthening at SLS and ELETTRA. The successful operation of those machines led to the choice of SC cavities in the design of Soleil, Diamond Light Source and Shanghai Synchrotron Radiation Facility, all now in operation. Additionally, Taiwan Photon Source, Pohang Light Source II and National Synchrotron Light Source II are currently in construction and all employ SC cavities. In this paper we will review recent operational experience of SC cavities in light sources and will describe recent developments related to the cavities and their auxiliary systems.

MOPO068

Reliability Improvements of the Diamond Superconducting Cavities

267

P. Gu, M. Jensen, M. Maddock, P.J. Marten, S.A. Pande, S. Rains, A.F. Rankin, D. Spink, A.V. Watkins
Diamond, Oxfordshire, United Kingdom

For successful operation of superconducting cavities in light sources, high reliability and minimal beam losses are essential. Diamond started operation with users in January 2007 and since then, the Diamond storage ring superconducting cavities have been the largest single contributor to unplanned beam trips. We have dedicated extensive effort to improve our data acquisition, numerical modelling and fault analysis to improve our understanding of the main causes of the trips and how to prevent trips or reduce their frequency. In the past seven months, the performance of the cavities has improved significantly. We present here our analysis of some of the trips and their underlying causes and discuss improvements carried out.

THPO010

Multipactor Studies for DIAMOND Storage Ring Cavities

718

S.A. Pande, M. Jensen
Diamond, Oxfordshire, United Kingdom

The Diamond storage ring is presently operating with two CESR type Superconducting (SC) RF cavities operating at 499.654 MHz. The cavities are suffering from a significant number of trips due to a sudden loss of accelerating field believed to be caused by Multipacting. It is observed that operating the cavities at lower voltages reduces the trip frequency significantly. In order to estimate the multipacting thresholds and to determine safe (multipactor free) parameter zones, we have initiated a detailed simulation study of multipacting in the cavities and the coupling waveguide. The cavities have fixed coupling, and therefore the match of the cavities varies with beam current, radiation loss and cavity voltage. A change in any of these parameters leads to a different standing wave in the waveguide. This requires the simulations to account for the different operating conditions. In addition to the waveguide and the cavity cell, the simulations also indicate the possibility of multipactor in the connecting beam tubes. In this paper, we summarise the results of our simulations obtained using CST Studio PIC and Tracking solvers.