ICALEPCS2011 - List of Authors (Butterworth, A.C.)

Paper

Title

Page

A Digital System for Longitudinal Emittance Blow-Up in the LHC

215

M. Jaussi, M. E. Angoletta, P. Baudrenghien, A.C. Butterworth, J. Sanchez-Quesada, E.N. Shaposhnikova, J. Tückmantel
CERN, Geneva, Switzerland

In order to preserve beam stability above injection energy in the LHC, longitudinal emittance blowup is performed during the energy ramp by injecting band-limited noise around the synchrotron frequency into the beam phase loop. The noise is generated continuously in software and streamed digitally into the DSP of the Beam Control system. In order to achieve reproducible results, a feedback system on the observed average bunch length controls the strength of the excitation, allowing the operator to simply set a target bunch length. The frequency spectrum of the excitation depends on the desired bunch length, and as it must follow the evolution of the synchrotron frequency spread through the ramp, it is automatically calculated by the LHC settings management software from the energy and RF voltage. The system is routinely used in LHC operation since August 2010. We present here the details of the implementation in software, FPGA firmware and DSP code, as well as some results with beam.

Poster MOPKS024 [0.467 MB]

Paper	Title	Page
MOPKS024	A Digital System for Longitudinal Emittance Blow-Up in the LHC	215
	M. Jaussi, M. E. Angoletta, P. Baudrenghien, A.C. Butterworth, J. Sanchez-Quesada, E.N. Shaposhnikova, J. Tückmantel CERN, Geneva, Switzerland
	In order to preserve beam stability above injection energy in the LHC, longitudinal emittance blowup is performed during the energy ramp by injecting band-limited noise around the synchrotron frequency into the beam phase loop. The noise is generated continuously in software and streamed digitally into the DSP of the Beam Control system. In order to achieve reproducible results, a feedback system on the observed average bunch length controls the strength of the excitation, allowing the operator to simply set a target bunch length. The frequency spectrum of the excitation depends on the desired bunch length, and as it must follow the evolution of the synchrotron frequency spread through the ramp, it is automatically calculated by the LHC settings management software from the energy and RF voltage. The system is routinely used in LHC operation since August 2010. We present here the details of the implementation in software, FPGA firmware and DSP code, as well as some results with beam.
	Poster MOPKS024 [0.467 MB]