Pionska apsorpcija u 4He

This paper presents a large solid angle measurement of the positive pion absorption cross-section on 4He and its decomposition into partial channels. A large fraction of the absorption cross-section at incident pion kinetic energies of Tπ+ =70, 118, 162, 239, and 330 MeV is due to multinucleon channels.Daju se ishodi mjerenja pod velikim prostornim kutom udarnog presjeka za apsorpciju pozitivnih piona u He4 i razdjela na pojedine kanale. Velik dio apsorpcijskog udarnog presjeka za energije upadnih piona od Tπ+ =70, 118, 162, 239 i 330 MeV je posljedica višenukleonskih kanala

Ceramic mould development for precision bending of thin glass

In high-energy astrophysics, X-ray telescopes play a key role as a primary source of information. However, the weight of the satellite-based telescope mirrors limits their size and thus their light collecting power. The research project "precision bending of thin glass" aims to develop lightweight and precise alternatives for X-ray mirrors based on thin glass segments. Glass has many material-specific advantages, and glass samples with thicknesses < 0.5 mm and an extremely low micro-roughness are commercially available. They can be shaped by a thermal treatment during which the shape of an underlying mould is transferred to the glass in a process called glass slumping. The project's core is the investigation of heat-resistant porous ceramic materials for the production of moulds and the development of appropriate high-precision machining processes. The project aims for the manufacturing of an exemplary mould, which allows the slumping of mirror segments for an X-ray optics with shaping supported using vacuum pumping from the mould side. The necessary dimensional accuracy of < 1 μm / 100 mm on the mould and on the glass should be finally demonstrated. The requirements to an open-pored and chemically inactive ceramics, which is dimensionally stable under the thermal process, are demanding, so the range of suitable materials is narrow. Our primary choice for the mould material is a carbon-fiber reinforced silicon carbide (HB-Cesic®). HB-Cesic® is well known for its thermal and mechanical stability and has already been used for glass slumping. The following Fig. 1 shows a fully polished mould out of dense HB-Cesic®

Pion absorption reactions on \chem{N}, \chem{Ar} and \chem{Xe}

The absorption of $\pi^{+}$ on \chem{Ar} was studied at pion energies of 70, 118, 162, 239 and 330MeV, and on \chem{N} and \chem{Xe} at 239MeV. Twenty-six absorption reaction channels with at least two energetic charged particles in the final state have been evaluated. Partial cross-sections have been determined according to the number of protons, neutrons and deuterons in the final state