IPAC2012 - List of Authors (Johansson, A.J.)

Paper	Title	Page
WEPPP093	Time and Phase Synchronisation at ESS	2927
	A.J. Johansson Lund University, Lund, Sweden R. Zeng ESS, Lund, Sweden
	ESS is a next generation spallation source to be built in Lund, Sweden. It is a green field laboratory, and as such it has the opportunity to establish one central timing reference for all systems, from control systems through reference phases for the Linac RF generators to the scientific instruments at the detector. We will here present the proposed architecture for this timing and phase reference system.

THPPC082	Control Performance Improvement by Using Feedforward in LLRF	3476
	R. Zeng, D.P. McGinnis, S. Molloy ESS, Lund, Sweden A.J. Johansson Lund University, Lund, Sweden
	The LLRF design is ongoing at ESS (European Spallation Source). One major task of LLRF is to overcome a variety of perturbations such as klystron droop and ripple, Lorentz detuning and beam loading. These perturbations can be well suppressed by classical PI (proportional-integral) controller in feedback loop, but at a cost of raising risk of instability and consuming power overhead for overshoot. Since ESS is a green project focusing on energy efficiency, we will hence investigate in this paper some feedforward and advanced adaptive algorithms to deal with these perturbations, so as to improve the control performance and reduce the power overhead.

THPPC083	Investigation of Feedback Control for Klystron Ripple	3479
	R. Zeng, D.P. McGinnis, S. Molloy ESS, Lund, Sweden A.J. Johansson Lund University, Lund, Sweden
	At ESS (European Spallation Source), there might be potentially serious droop and ripple because of long RF pulse more than 3 ms. It is important for us to know to what extent the droop and ripple affects the klystron output, and how much we can tolerate. The variations of the phase and amplitude of klystron output due to the change in klystron cathode voltage is investigated in this Paper. The mechanism and the effectiveness of the feedback control to suppress the variations are given. To understand the limitation of the feedback, both proportional controller and proportional-integral controller used in feedback loop are simulated and analyzed respectively for superconducting cavity and normal conducting cavity. The tolerances of the droop and ripple in cathode voltage under feedback control are shown according to the data and results obtained.

Paper

Title

Page

Time and Phase Synchronisation at ESS

2927

A.J. Johansson
Lund University, Lund, Sweden
R. Zeng
ESS, Lund, Sweden

ESS is a next generation spallation source to be built in Lund, Sweden. It is a green field laboratory, and as such it has the opportunity to establish one central timing reference for all systems, from control systems through reference phases for the Linac RF generators to the scientific instruments at the detector. We will here present the proposed architecture for this timing and phase reference system.

THPPC082

Control Performance Improvement by Using Feedforward in LLRF

3476

R. Zeng, D.P. McGinnis, S. Molloy
ESS, Lund, Sweden
A.J. Johansson
Lund University, Lund, Sweden

The LLRF design is ongoing at ESS (European Spallation Source). One major task of LLRF is to overcome a variety of perturbations such as klystron droop and ripple, Lorentz detuning and beam loading. These perturbations can be well suppressed by classical PI (proportional-integral) controller in feedback loop, but at a cost of raising risk of instability and consuming power overhead for overshoot. Since ESS is a green project focusing on energy efficiency, we will hence investigate in this paper some feedforward and advanced adaptive algorithms to deal with these perturbations, so as to improve the control performance and reduce the power overhead.

THPPC083

Investigation of Feedback Control for Klystron Ripple

3479

R. Zeng, D.P. McGinnis, S. Molloy
ESS, Lund, Sweden
A.J. Johansson
Lund University, Lund, Sweden

At ESS (European Spallation Source), there might be potentially serious droop and ripple because of long RF pulse more than 3 ms. It is important for us to know to what extent the droop and ripple affects the klystron output, and how much we can tolerate. The variations of the phase and amplitude of klystron output due to the change in klystron cathode voltage is investigated in this Paper. The mechanism and the effectiveness of the feedback control to suppress the variations are given. To understand the limitation of the feedback, both proportional controller and proportional-integral controller used in feedback loop are simulated and analyzed respectively for superconducting cavity and normal conducting cavity. The tolerances of the droop and ripple in cathode voltage under feedback control are shown according to the data and results obtained.