COOL2013 - List of Authors (Thorndahl, L.)

Paper

Title

Page

Progress of the Stochastic Cooling System of the Collector Ring

40

C. Dimopoulou, D. Barker, R.M. Böhm, A. Dolinskyy, B. J. Franzke, R. Hettrich, W. Maier, R. Menges, F. Nolden, C. Peschke, P. Petri, M. Steck
GSI, Darmstadt, Germany
L. Thorndahl
CERN, Geneva, Switzerland

An overview of the recent achievements and ongoing developments for the stochastic cooling system of the Collector Ring is given. In focus are the hardware developments as well as the progress in predicting the system performance. The system operates in the frequency band 1-2 GHz, it has to provide fast 3D cooling of antiproton, rare isotope and stable heavy ion beams. The main challenges are (i) the cooling of antiprotons by means of cryogenic movable pick-up electrodes and (ii) the fast two-stage cooling (pre-cooling by the Palmer method, followed by the notch filter method) of the hot rare isotopes. Recently, a novel code for simulating the cooling process in the time domain has been developed at CERN. First results for the momentum cooling for heavy ions in the CR will be shown in comparison with results obtained in the frequency domain with the Fokker-Planck equation.

Slides TUAM1HA01 [4.320 MB]

TUAM1HA03

Stochastic Cooling of Bunched Ions Simulated in the Time Domain

49

L. Thorndahl
CERN, Geneva, Switzerland

To include the influence of synchrotron oscillations, beam feedback and IBS a particle by particle and turn by turn treatment in the time-domain has been tried out. - Complete pickup and kicker characteristics are introduced via inverse Laplace transformation, and so is the Dirac function representing the single-ion passage at the pickup. - The computation time is kept within limits thanks to the law that cooling times scale proportionnally with the number of ions. Typically 50 000 simulation particles are cooled in 5000 turns. Instabilities occur for excessive el. gain.

Slides TUAM1HA03 [0.577 MB]

WEPPO21

Design of the Palmer Pickup for Stochastic Pre-cooling of Heavy Ions at the CR

149

L. Thorndahl
CERN, Geneva, Switzerland
D. Barker, C. Dimopoulou, C. Peschke
GSI, Darmstadt, Germany

We detail the design and optimisation of modified Faltin type pick-ups for the pre-cooling of heavy ions in the CR ring at GSI. The design challenge includes simultaneous optimisation of large pick-up impedance, 50 Ω characteristic impedance, frequency independence over a large bandwidths and phase velocity matched to particle velocity. Although heavy ions offer large signals due to their charge, their relatively slow velocity is difficult to match in Faltin type pick-ups while maintaining a flat frequency response and a 50 Ω characteristic impedance. We explain the design process, and show how multiple parameters are simultaneously optimised using genetic algorithms, which are suitable for optimization problems with large and complex search spaces.

Paper	Title	Page
TUAM1HA01	Progress of the Stochastic Cooling System of the Collector Ring	40
	C. Dimopoulou, D. Barker, R.M. Böhm, A. Dolinskyy, B. J. Franzke, R. Hettrich, W. Maier, R. Menges, F. Nolden, C. Peschke, P. Petri, M. Steck GSI, Darmstadt, Germany L. Thorndahl CERN, Geneva, Switzerland
	An overview of the recent achievements and ongoing developments for the stochastic cooling system of the Collector Ring is given. In focus are the hardware developments as well as the progress in predicting the system performance. The system operates in the frequency band 1-2 GHz, it has to provide fast 3D cooling of antiproton, rare isotope and stable heavy ion beams. The main challenges are (i) the cooling of antiprotons by means of cryogenic movable pick-up electrodes and (ii) the fast two-stage cooling (pre-cooling by the Palmer method, followed by the notch filter method) of the hot rare isotopes. Recently, a novel code for simulating the cooling process in the time domain has been developed at CERN. First results for the momentum cooling for heavy ions in the CR will be shown in comparison with results obtained in the frequency domain with the Fokker-Planck equation.
	Slides TUAM1HA01 [4.320 MB]

TUAM1HA03	Stochastic Cooling of Bunched Ions Simulated in the Time Domain	49
	L. Thorndahl CERN, Geneva, Switzerland
	To include the influence of synchrotron oscillations, beam feedback and IBS a particle by particle and turn by turn treatment in the time-domain has been tried out. - Complete pickup and kicker characteristics are introduced via inverse Laplace transformation, and so is the Dirac function representing the single-ion passage at the pickup. - The computation time is kept within limits thanks to the law that cooling times scale proportionnally with the number of ions. Typically 50 000 simulation particles are cooled in 5000 turns. Instabilities occur for excessive el. gain.
	Slides TUAM1HA03 [0.577 MB]

WEPPO21	Design of the Palmer Pickup for Stochastic Pre-cooling of Heavy Ions at the CR	149
	L. Thorndahl CERN, Geneva, Switzerland D. Barker, C. Dimopoulou, C. Peschke GSI, Darmstadt, Germany
	We detail the design and optimisation of modified Faltin type pick-ups for the pre-cooling of heavy ions in the CR ring at GSI. The design challenge includes simultaneous optimisation of large pick-up impedance, 50 Ω characteristic impedance, frequency independence over a large bandwidths and phase velocity matched to particle velocity. Although heavy ions offer large signals due to their charge, their relatively slow velocity is difficult to match in Faltin type pick-ups while maintaining a flat frequency response and a 50 Ω characteristic impedance. We explain the design process, and show how multiple parameters are simultaneously optimised using genetic algorithms, which are suitable for optimization problems with large and complex search spaces.