Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal

An optically powered fibre network for heterogeneous subscribers

In optically powered networks, glass fibres are used for transmitting optical communication signals as well as optical energy for electrically powered devices. Advantages over existing power delivery technologies are: immunity to electromagnetic interference, spark-free power for safety-critical applications, slim cables, simple installation and reduced maintenance cost. Applications relate to security of public spaces and buildings, downhole exploration, medical endoscopes, and to communications in the context of remote RF antennas and passive optical networks (PON). An optically powered network can connect widely differing subscribers with low/high bandwidth requirements, asynchronous/ synchronous operation, and low/high priority, e.g., energy-preserving small-bandwidth subscribers with ultra-low duty cycles and low network priority (e.g., temperature sensors) in combination with wide-bandwidth subscribers operating at large duty cycles and high priority (e.g., video conferencing). Optical energy is supplied centrally from an access point, and this results in a combined star and tree-like network topology. As a consequence, subscribers communicate with the CO only, and therefore a standard carrier sense multiple access (CSMA) protocol cannot handle the data exchange. We present optically powered subscriber hardware and demonstrate a low-energy medium-access control (LE-MAC) protocol that extends the IEEE 802 standard, allows random and scheduled medium access of subscribers, and, by quality-of-service support, efficiently uses the available resources, namely channel bandwidth and optically supplied energy

Implementation of a Virtual Internal Configuration Access Port (JCAP) for Enabling Partial Self-Reconfiguration on Xilinx Spartan III FPGAs

The exploitation of dynamic and partial hardware reconfiguration on FPGAs is currently being investigated in various research projects, dealing with systems for space applications to automotive and masurement applications. Despite challenges such as a complicated design flow, dynamic reconfigurable systems offer advantages in terms of flexibility and performance. Unfortunately only few kinds of commercial architectures support dynamic and partial reconfiuration, which has lead to Virtex II / IV being main target architectures for this kind of systems. Additionally, the Xilinx Spartan III architecture is dynamically and partially reconfigurable with some limitations, one of them being the lack of an internal configuration port. The Virtex II / IV and V architectures all include the ICAP port, which allows a system to reconfigure itself during run-time without additional external components. Until now, this was not possible on the Spartan III architecture. This paper presents the implementation of a virtual internal configuration port for the Spartan III family of FPGAs. The configuration port was implemented for a hardware reconfigurable measurement system, which is implemented on a Spartan III FPGA due to its cost-and power optimized characteristics