ACC-Bereich

Resonant slow extraction is routinely used to provide ion beams to various users.At GSI SIS18, two extraction methods are implemented: quadrupole-driven and radio frequency Knock Out (RF-KO) extraction.In either case, delivering a defined beam intensity (spill) without fluctuations or drifts is desired for an efficient beam usage.The Spill Optimization System (SOS) was developed to address this demand and improve the spill quality based on online spill monitoring.Developed using software-defined radio technology, it comprises a feedback controlling the spill rate and an optimization algorithm to improve the spill quality.In the case of RF-KO extraction, it controls the spill by generating tailored excitation signals for the KO exciter.For quadrupole-driven extraction, it produces a control signal for the tune ramp including tune wobbling to improve the spill quality.This contribution gives an overview on the systems and compares different usage scenarios..

Various physical and technology-dependent limits are encountered for key performance parameters of accelerators such as high-gradient acceleration, high-field bending, beam size, beam brightness, beam intensity and luminosity. This paper will review these limits and the associated challenges. [...]

The radiative electron capture (REC) into the K shell of bare Xe ions colliding with a hydrogen gas target has been investigated. In this study, the degree of linear polarization of the K-REC radiation was measured and compared with rigorous relativistic calculations as well as with the previous results recorded for U92+. [...]

The LIBELLE experiment performed at the experimental storage ring at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany, has successfully determined the ground state hyperfine (HFS) splittings in hydrogen-like (${}^{209}{\mathrm{Bi}}^{82+}$) and lithium-like (${}^{209}{\mathrm{Bi}}^{80+}$) bismuth. The study of HFS transitions in highly charged ions enables precision tests of QED in extreme electric and magnetic fields otherwise not attainable in laboratory experiments. [...]