SRF2013 - List of Authors (Pande, S.A.)

Paper	Title	Page
MOP003	Implications of Increased Beam Current for the Diamond Storage Ring RF System	73
	C. Christou, A. Bogusz, P. Gu, M. Maddock, P.J. Marten, S.A. Pande, A.F. Rankin, D. Spink, A.V. Watkins Diamond, Oxfordshire, United Kingdom
	Diamond Light Source presently operates for users with 300mA beam current and initial tests have begun to upgrade this current towards an ultimate goal of 500mA. The implications of such a beam current increase for the storage ring RF system will be significant, including the installation of a third superconducting cavity and a possible modification of the coupling parameters of the existing cavities. An overview of the planned enhancements of the RF system is presented, including an update of the procurement of a new CESR-design cavity and options for installation and operation of this cavity and supporting infrastructure.

MOP059	Management for the Long-Term Reliability of the Diamond Superconducting RF Cavities	255
	P. Gu, C. Christou, M.P. Cox, S.A. Pande, A.F. Rankin, H.S. Shiers, A.V. Watkins Diamond, Oxfordshire, United Kingdom
	Diamond started operation with users in January 2007 and the Diamond storage ring superconducting RF cavities used to be the largest single contributor to unplanned beam trips. Extensive effort has been dedicated to understand and improve the long-term stability of the SRF cavities. Our experience shows that the long-term stability of superconducting RF cavities relies heavily on the surface conditions. Gases keep accumulating on the cold surfaces with time due to its huge cryo-pumping capacity. The integral effect will ultimately lead to fast vacuum trips during operation. In Diamond, we have developed a systematic approach to control the long-term stability of the SRF cavities. We will discuss here our approach and also present the future work that should be completed.

THP062	Optimisation of the 3-Stub Tuner for Matching the Diamond SCRF Cavities	1061
	S.A. Pande, C. Christou, P. Gu, M. Jensen Diamond, Oxfordshire, United Kingdom
	The Diamond Storage Ring cavities are aperture coupled resulting in a fixed external Q. This results in the cavities being matched under certain conditions depending on the loss per turn, the beam current and the accelerating voltage. Operationally, there are advantages to limiting the accelerating voltage to improve reliability and lifetime, which at high beam current results in a mismatch and high reflected power. To match the cavities under such non-optimum operating conditions we use 3-stub tuners in the waveguide feeds. It has been observed, that certain configurations of the 3-stub tuners can improve the match of the cavity, but this can result in strong heating of the waveguide in the cryostat. Numerical simulations of the cavity along with the coupling waveguide and 3-stub tuners have been carried out using CST Studio for different beam loading conditions to optimise the 3-stub tuners for acceptable match and heating. In this paper we present the results of our simulations and comparisons with measurements for operation with different beam currents and cavity voltages.

Paper

Title

Page

Implications of Increased Beam Current for the Diamond Storage Ring RF System

73

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

Diamond Light Source presently operates for users with 300mA beam current and initial tests have begun to upgrade this current towards an ultimate goal of 500mA. The implications of such a beam current increase for the storage ring RF system will be significant, including the installation of a third superconducting cavity and a possible modification of the coupling parameters of the existing cavities. An overview of the planned enhancements of the RF system is presented, including an update of the procurement of a new CESR-design cavity and options for installation and operation of this cavity and supporting infrastructure.

MOP059

Management for the Long-Term Reliability of the Diamond Superconducting RF Cavities

255

P. Gu, C. Christou, M.P. Cox, S.A. Pande, A.F. Rankin, H.S. Shiers, A.V. Watkins
Diamond, Oxfordshire, United Kingdom

Diamond started operation with users in January 2007 and the Diamond storage ring superconducting RF cavities used to be the largest single contributor to unplanned beam trips. Extensive effort has been dedicated to understand and improve the long-term stability of the SRF cavities. Our experience shows that the long-term stability of superconducting RF cavities relies heavily on the surface conditions. Gases keep accumulating on the cold surfaces with time due to its huge cryo-pumping capacity. The integral effect will ultimately lead to fast vacuum trips during operation. In Diamond, we have developed a systematic approach to control the long-term stability of the SRF cavities. We will discuss here our approach and also present the future work that should be completed.

THP062

Optimisation of the 3-Stub Tuner for Matching the Diamond SCRF Cavities

1061

S.A. Pande, C. Christou, P. Gu, M. Jensen
Diamond, Oxfordshire, United Kingdom

The Diamond Storage Ring cavities are aperture coupled resulting in a fixed external Q. This results in the cavities being matched under certain conditions depending on the loss per turn, the beam current and the accelerating voltage. Operationally, there are advantages to limiting the accelerating voltage to improve reliability and lifetime, which at high beam current results in a mismatch and high reflected power. To match the cavities under such non-optimum operating conditions we use 3-stub tuners in the waveguide feeds. It has been observed, that certain configurations of the 3-stub tuners can improve the match of the cavity, but this can result in strong heating of the waveguide in the cryostat. Numerical simulations of the cavity along with the coupling waveguide and 3-stub tuners have been carried out using CST Studio for different beam loading conditions to optimise the 3-stub tuners for acceptable match and heating. In this paper we present the results of our simulations and comparisons with measurements for operation with different beam currents and cavity voltages.