SIS18

SIS18

SIS18 is a heavy-ion synchrotron at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, serving as a principal injector for downstream facilities and as a research accelerator for nuclear, atomic, and materials physics. It operates in coordination with the UNILAC linear accelerator, the ESR (Experimental Storage Ring), and the FAIR project infrastructure, enabling experiments involving relativistic heavy ions, rare isotope beams, and high-energy density matter. The facility contributes to international programs involving collaborations with institutions such as the CERN, RIKEN, Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, and the Max Planck Society.

Overview

SIS18 is a 216-metre circumference synchrotron designed for acceleration of heavy ions from injection by UNILAC to kinetic energies used by the ESR (Experimental Storage Ring), the FRS (Fragment Separator), and transfer lines feeding the GSI Helmholtz Centre for Heavy Ion Research experimental halls. The machine provides beams of elements across the periodic table from hydrogen to uranium, serving experiments in nuclear astrophysics, atomic physics, materials science, and biophysics at facilities including TRANSURANUS, PHELIX, and SPARC. SIS18 supports time-structured beams for experiments associated with the Helmholtz Association, enabling collaborations with universities such as the Technical University of Darmstadt and research organizations like DESY.

History and development

Construction of the synchrotron complex at the GSI Helmholtz Centre for Heavy Ion Research followed post‑World War II planning for European heavy-ion research and the success of early electrostatic and cyclotron projects in the United States, France, and Soviet Union. SIS18 was commissioned in 1976 and expanded operationally through collaborations with the European Union research frameworks and national agencies including the German Federal Ministry of Education and Research. Early development integrated technologies pioneered at laboratories such as Brookhaven National Laboratory and Lawrence Berkeley National Laboratory, while adaptations for high-intensity heavy-ion operation paralleled upgrades at GANIL and RIKEN. The machine has been central to GSI programs that later informed the design of the FAIR facility, aligning with accelerator projects like the SIS100 and SIS300 concepts.

Technical specifications

SIS18 is a synchrotron with a maximum magnetic rigidity of about 4.5 T·m, a circumference of 216 m, and operates with combined-function magnets arranged in a lattice permitting both fast and slow extraction. Injection is provided by the UNILAC linear accelerator and accumulation techniques incorporate multi-turn injection and transverse painting strategies developed at CERN and BNL. Radiofrequency systems include harmonic cavities and bunching systems comparable to those at TRIUMF and GSI Helmholtz Centre for Heavy Ion Research’s other rings. The vacuum system, beam diagnostics, and scraper assemblies were influenced by designs from DESY and incorporate technologies such as residual gas ionization profile monitors and current transformers used at the European XFEL. Power supplies, magnet families, and control systems follow standards harmonized with projects like ITER control prototypes and industrial partners including Siemens.

Operation and experiments

SIS18 operates beams for injection into storage rings like the ESR (Experimental Storage Ring) and for direct use by experiments such as heavy-ion collision studies at the PHELIX laser facility, fragmentation experiments feeding the FRS (Fragment Separator), and atomic physics programs collaborating with SPARC. Experiments conducted with SIS18-provided beams include measurements relevant to the r-process (nucleosynthesis), equation-of-state studies connected to neutron star research, and radiation biology investigations aligned with projects at the German Cancer Research Center. The synchrotron supports fast extraction for time-resolved studies and slow extraction for precision experiments, employing detector systems similar to those at ALICE, ISOLDE, and FAIR demonstrators. Operational coordination uses scheduling and beam-time allocation frameworks analogous to those at CERN and the European Space Agency partnerships for space radiation testing.

Upgrades and future plans

Planned upgrades for SIS18 focus on increasing intensity, beam quality, and reliability to meet requirements for the FAIR accelerator complex and for novel experimental programs in high-energy density physics and rare isotope production. Technical improvements being studied include new power converters inspired by developments at SIS100, upgraded radiofrequency cavities drawing on innovations at TRIUMF, and enhanced beam diagnostics similar to instruments at DESY. Collaboration with industry partners such as Siemens and research organizations including the Max Planck Society, Helmholtz Association, and European Union research initiatives aims to align SIS18 operation with emerging projects like FAIR and international campaigns at RIKEN and Brookhaven National Laboratory. Long-term concepts consider integration with superconducting magnet technology explored for SIS300 and adoption of machine-learning based control strategies pioneered in projects at CERN and DESY.

Category:Particle accelerators Category:GSI Helmholtz Centre for Heavy Ion Research