Development of fast switching photochromic coatings on transparent plastics and glass

A new photochromic organic-inorganic nanocomposite (Nanomer(R)) coating system has been developed. It is based on an epoxysilane as network former, an organic bisepoxide as spacer, an organic amine as thermal cross-linker and surface modified SiO2 nanoparticles as fillers. This coating system is compatible with different photochromic dyes, like oxazines and pyrans. Photochromic coatings with blue, yellow, red, green, violet and neutral tints were prepared on flat glass and PMMA substrates by dip coating and cured for 3 h at 100 degrees C. The photochromic coatings show the following properties: the transmittance changes reversibly between 80 and 20% with half fading times of about 2-20 s (comparable to the half fading time of the appropriate dye in ethanolic solution) after UV irradiation for 15 s with 5 mW/cm(2). The coatings show a scratch hardness of about 15 g (scratch test with Vickers indenter, coating thickness 10 mu m). The addition of only 3 wt.% SiO2 nanoparticles relative to epoxysilane increases the scratch resistance of the coatings to about 20 g without changing the fast kinetics of the incorporated photochromic dye(s). The long term stability of the photochromic dye(s) in the matrix system can be considerably improved by the introduction of additives like antioxidants, hindered amine light stabilizer (HALS) and UV stabilizers. The half lifetime (decay to 50% of the initial photochromic intensity) of a blue spirooxazine dye (Blue A) measured in a dry sun-test (75 mW/cm(2)) could be increased from 20 h without any additive up to 200 h with an UV absorber (Tinuvin 327) as a stabilizer, which is assumed to be sufficient for ophthalmic applications

Online Pattern Recognition for the ALICE High Level Trigger

The ALICE High Level Trigger has to process data online, in order to select interesting (sub)events, or to compress data efficiently by modeling techniques.Focusing on the main data source, the Time Projection Chamber (TPC), we present two pattern recognition methods under investigation: a sequential approach "cluster finder" and "track follower") and an iterative approach ("track candidate finder" and "cluster deconvoluter"). We show, that the former is suited for pp and low multiplicity PbPb collisions, whereas the latter might be applicable for high multiplicity PbPb collisions, if it turns out, that more than 8000 charged particles would have to be reconstructed inside the TPC. Based on the developed tracking schemes we show, that using modeling techniques a compression factor of around 10 might be achievableComment: Realtime Conference 2003, Montreal, Canada to be published in IEEE Transactions on Nuclear Science (TNS), 6 pages, 8 figure

Real-time TPC Analysis with the ALICE High-Level Trigger

The ALICE High-Level Trigger processes data online, to either select interesting (sub-) events, or to compress data efficiently by modeling techniques. Focusing on the main data source, the Time Projection Chamber, the architecure of the system and the current state of the tracking and compression methods are outlined.Comment: 6 pages, 5 figures, to be published in NIM

Sustainability in astroparticle physics

The topic of sustainability is becoming increasingly important in research activities in astroparticle physics, both in existing and also in future instrument. At this year\u27s International cosmic ray conference (ICRC 2021) one session was dedicated to this topic. This publication will summarise the findings of this well-attended online session

Transition Radiation Spectroscopy with Prototypes of the ALICE TRD

We present measurements of the transition radiation (TR) spectrum produced in an irregular radiator at different electron momenta. The data are compared to simulations of TR from a regular radiator.Comment: 4 pages, 5 Figures, Proceedings for "TRDs for the 3rd millennium" (Sept. 4-7, 2003, Bari, Italy

Software environment for controlling and re-configuration of Xilinx Virtex FPGAs – TWEPP-07

The Time Projection Chamber is one of the detectors of the ALICE experiment, that is currently being commissioned at the Large Hadron Collider at CERN. The Detector Control System is used for control and monitoring of the system. For the TPC Front-End Electronics (FEE) the control node is a Readout Control Unit that communicates to higher layers via Ethernet, using the standard framework DIM. The Readout Control Unit is equipped with commercial SRAM based FPGAs that will experience errors due to the radiation environment they are operating in. This article will present the implemented hardware solution for error correction and will focus on the software environment for configuration and controlling of the system – TWEPP-07

Position Reconstruction in Drift Chambers operated with Xe, CO2 (15%)

We present measurements of position and angular resolution of drift chambers operated with a Xe,CO$_2$(15%) mixture. The results are compared to Monte Carlo simulations and important systematic effects, in particular the dispersive nature of the absorption of transition radiation and non-linearities, are discussed. The measurements were carried out with prototype drift chambers of the ALICE Transition Radiation Detector, but our findings can be generalized to other drift chambers with similar geometry, where the electron drift is perpendicular to the wire planes.Comment: 30 pages, 18 figure

Statistical signatures of critical behavior in small systems

The cluster distributions of different systems are examined to search for signatures of a continuous phase transition. In a system known to possess such a phase transition, both sensitive and insensitive signatures are present; while in systems known not to possess such a phase transition, only insensitive signatures are present. It is shown that nuclear multifragmentation results in cluster distributions belonging to the former category, suggesting that the fragments are the result of a continuous phase transition.Comment: 31 pages, two columns with 30 figure

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