Status Of The FAIR Synchrotron Projects SIS18 And SIS100

A large fraction of the program to upgrade the existingheavy ion synchrotron SIS18 as injector for the FAIR synchrotron SIS100 has been successfully completed. With the achieved technical status, a major increase of theaccelerated number of heavy ions could be reached. Thenow available performance especially demonstrates thefeasibility of high intensity beams of medium charge stateheavy ions with a sufficient control of the dynamicvacuum and connected charge exchange loss. Two furtherupgrade measures, the installation of additional magneticalloy (MA) acceleration cavities and the exchange of themain dipole power converter, are presently beingimplemented. For the FAIR synchrotron SIS100, theprocurement of all major components with longproduction times has been started. With the delivery andtesting of several pre-series components, the phase ofoutstanding technical reserach and developments could becompleted and the readiness for series productionachieved

Construction of minimal gauge invariant subsets of Feynman diagrams with loops in gauge theories

In this work, we consider Feynman diagrams with loops in renormalizable gauge theories with and without spontaneous symmetry breaking. We demonstrate that the set of Feynman diagrams with a fixed number of loops, contributing to the expansion of a connected Green's function in a fixed order of perturbation theory, can be partitioned into minimal gauge invariant subsets by means of a set of graphical manipulations of Feynman diagrams, called gauge flips. To this end, we decompose the Slavnov-Taylor identities for the expansion of the Green's function in such a way that these identities can be defined for subsets of the set of all Feynman diagrams. We then prove, using diagrammatical methods, that the subsets constructed by means of gauge flips really constitute minimal gauge invariant subsets. Thereafter, we employ gauge flips in a classification of the minimal gauge invariant subsets of Feynman diagrams with loops in the Standard Model. We discuss in detail an explicit example, comparing it to the results of a computer program which has been developed in the context of the present work

Construction of minimal gauge invariant subsets of Feynman diagrams with loops in gauge theories

In this work, we consider Feynman diagrams with loops in renormalizable gauge theories with and without spontaneous symmetry breaking. We demonstrate that the set of Feynman diagrams with a fixed number of loops, contributing to the expansion of a connected Green's function in a fixed order of perturbation theory, can be partitioned into minimal gauge invariant subsets by means of a set of graphical manipulations of Feynman diagrams, called gauge flips. To this end, we decompose the Slavnov-Taylor identities for the expansion of the Green's function in such a way that these identities can be defined for subsets of the set of all Feynman diagrams. We then prove, using diagrammatical methods, that the subsets constructed by means of gauge flips really constitute minimal gauge invariant subsets. Thereafter, we employ gauge flips in a classification of the minimal gauge invariant subsets of Feynman diagrams with loops in the Standard Model. We discuss in detail an explicit example, comparing it to the results of a computer program which has been developed in the context of the present work

Challenges for the SIS100 emergency beam dump system

The heavy ion synchrotron SIS100 is the flagship accelerator of the Facility for Antiproton and Ion Research (FAIR) currently under construction at GSI, Darmstadt. It will provide high intensity beams of particles ranging from protons to uranium ions at beam rigidities up to 100 Tm. Part of the machine protection system is an emergency beam dump that is partly inside the vacuum system and partly outside. Due to the beam dump’s tight integration with the beam extraction system, there is little flexibility for design of the dump or beam optics defining the shape of the impacting beam. High energy deposition densities and the wide range of accelerated ions pose unique challenges to the survival of the dump. In this paper we identify the most demanding beam impact scenarios for the different dump components that will consequently guide choices for materials and design

Status of SIS100 slow extraction design including effects of measured magnetic field errors

The synchrotron SIS100 at FAIR, currently under construction in Darmstadt, Germany, will deliver slow extracted proton and ion beams up to 100 Tm employing resonant extraction. Its compact super-ferric dipole and quadrupole magnets allow fast ramping of magnetic field up to 4 T/s and 57 (T/m)/s, respectively. Recently, field errors has been measured for the dipole magnets and the first batch of quadrupole magnets. Higher order multipoles may interfere with resonant extraction, changing the geometry of the separatrix and conditions for resonant particles. The latter are affected most during their last turns and in the extraction channel owing to their large amplitudes, which amplify the effect of higher order multipoles. SIS100 comprises a set of corrector magnets up to octupole order, which can be used to compensate the impact of magnetic field errors. In this contribution, we report on the status of the slow extraction simulation studies including field errors. Furthermore, we present alternative working points for slow extraction, which are necessary to avoid the transition energy for some of beams required by the FAIR experiments

Design and Beam Dynamics of the Electron Lens for Space Charge Compensation in SIS18

An electron lens for space charge compensation is being developed at GSI to increase the ion beam intensities in SIS18 for the FAIR project. It uses an electron beam of 10A maximum current at 30keV. The maximum magnetic field on-axis is 0.6T, considerably higher than the field of the existing electron cooler. The magnetic system of the lens consists of solenoids and toroids. The toroids’ vertical field component creates a significant horizontal orbit deflection in the circulating low rigidity ion beam. To correct this deflection, four correction dipoles have been introduced. As common for electron lenses, the high-power electron beam is not dumped at ground potential, but rather in a collector with a small bias potential with respect to the cathode. The present design foresees a collector at -27kV, leading to a power dissipation of 30kW, distributed over a large surface area by placing the collector in an appropriately shaped magnetic field of a pre-collector solenoid. This contribution reports on the design of the lens and presents the results of beam transport simulations for the electron beam (with space charge) and a representative ion beam, performed using the 3D CST STUDIO