High intensity cyclotrons for driving hybrid nuclear systems

"Several cyclotron-based high intensity accelerators have been studied in the framework of the Energy Amplifier (EA) project proposed by Prof. C. Rubbia [1]. Among them, two basic designs are presented: a 380 MeV separated sector cyclotron delivering a high intensity proton beam to a target or to a booster accelerator and a low injection energy stand-alone H-2(+) cyclotron producing 110 MeV protons, extracted by stripping, available for further acceleration in a cyclotron or a superconducting linac structure. Specific aspects in the methods used for the design of these cyclotrons are also briefly described. [1] C. Rubbia, J.A. Rubio, S. Buono, F. Carminati, N. Fiétier, J. Galvez, C. Geles, Y. Kadi, R. Klapisch, P. Mandrillon, J.P. Revol and Ch. Roche, Conceptual design of a fast neutron operated high power energy amplifier,CERN Internal Report [CERN-AT-95-44 ET] (September 1995).

Spectral element methods for unsteady viscoelastic flows

This paper presents the development of spectral element methods to simulate unsteady flows of viscoelastic fluids using a differential constitutive equation. Preliminary results for simple test problems are discussed as well as possible techniques to improve the numerical stability of the computational algorithms

A three-stage cylotron for driving the Energy Amplifier

The goal of the proposed three-stage cylotron complex is to deliver a continuous external high energy (in the 1 GeV range) proton beam of the order 10 mA for driving the Energy Amplifier, a hybrid sub-critical nuclear system, which is being deveoped at CERN and whose principles have been successfully tested during the first experimental programme [1]. This accelerator consists of two 10 MeV injectors feeding a four separated sector magnet iscochronous ring from which a 120 MeV beam is injected into a large ring cylotron with ten separated spiral sector magnets. In this final booster six cavities operating at 42 MHz will provide an egenrgy gain per turn of 6 MeV in order to get a sufficient turn separation on the extraction radius. The maximum available current depends mainly on the beam quality on the extraction radius of the various cylotrons. This report summarizes the main fields of work carried out during these preliminary studies

Time-dependent algorithms for the simulation of viscoelastic flows with spectral element methods: applications and stability

This paper presents the development of spectral element methods to simulate unsteady flows of viscoelastic fluids using a closed-form differential constitutive equation. The generation and decay Poiseuille planar flows are considered as benchmark problems to test the abilities of our computational method to deal with truly time-dependent flows. Satisfactory results converging toward steady-state regimes have been obtained for the flow through a four-to-one planar abrupt contraction with unsteady algorithms. Time-dependent simulations of viscoelastic flows are prone to numerical instabilities even for simple geometrical configurations. Possible methods to improve the numerical stability of the computational algorithms are discussed in view of the results carried out with numerical simulations for the flows through a straight channel and the four-to-one contraction

Simulations of time-dependent flows of viscoelastic fluids with spectral element methods

This paper presents the application of spectral element methods to simulate the time-dependent flow of viscoelastic fluids in non-trivial geometries using a closed-form differential constitutive equation. As an example, results relative to the flow of a FENE-CR fluid in a two-dimensional four-to-one contraction are given