The source and transport system of the Karlsruhe tritium neutrino experiment (KATRIN) must provide a significant reduction in tritium flow and gas density. It comprises a 10 m long windowless source tube, where the tritium gas is injected, followed by a differential pumping system and a cryogenic pumping system. The primary challenge of the analysis is that the gas flow changes from a viscous flow regime inside the source tube to a transitional flow regime at the first pumping stage, and to a molecular flow regime at the remaining stages of the differential pumping system and further downstream. A strong molecular beaming effect must be considered. This article presents the results of calculations of gas density and flow for the complete source and differential pumping system. It is shown that a total flow-rate reduction factor of 1.4×10−8 can be attained, which is one of the prerequisites to achieve extreme-high vacuum conditions in the spectrometers used in the downstream end of the experiment.

It is a challenging but key task to reduce the tritium inventory in EU-DEMO to levels that are acceptable for a nuclear regulator. As solution to this issue, a smart fuel cycle architecture is proposed based on the concept of Direct Internal Recycling (DIR), in which the Metal Foil Pump (MFP) will play an important role to separate the unburnt hydrogen isotopes coming from the divertor by exploiting the superpermeation phenomenon. In this study, we will present the assessment of the performance of the lower port of EU-DEMO after the integration of the MFP. For the first time, a thorough comparison of three different MFP (parallel long tubes, sandwich and halo) designs is performed regarding conductance for helium molecules, the pumping speed and the separation factor for deuterium molecules under different physical and geometric parameters. All simulations were carried out in supercomputer Marconi-Fusion with our in-house Test Particle Monte Carlo (TPMC) simulation code ProVac3D because the code had been parallelized with high efficiency. These results are essential for the development of a suitable MFP design in the vacuum-pumping train of EU-DEMO.

We develop a first-order theory of the unified colored-noise approximation. It can be applied to general multidimensional systems driven by colored noise (the Ornstein-Uhlenbeck noise). A general formula for the first-order correction is derived, which is used for investigating the transient process of a dye laser. For the colored cubic model and colored gain-noise model of a dye laser, the Fokker-Planck equations are derived based on the general formula of first-order theory. The first-order corrections of the mean first-passage times for the models are obtained. We compare the results with numerical simulations, and show that the present results have greatly improved the results obtained by the original unified colored-noise approximation.

A future nuclear fusion plant DEMO needs neutral beam injection (NBI) systems requiring a vacuum pumping system with a very high pumping speed, in the order of several 1000 m³/s. Large customized cryopumps are actually used to meet the requirements. A promising concept for future NBI systems is based on high capacity getter materials. The ZAO^® alloy, developed by SAES Getters, Italy, provides a drastically improved performance for the pumping of hydrogen compared to conventional getter materials. This paper describes the experimental characterization of a large pump of scalable size with 15 kg of ZAO^® and the achieved results, in particular the systematic investigation of sorption characteristics and regeneration behaviors. Major findings include a very good repeatability of the sorption performance, a reduced pumping speed at higher pressures only above the NBI relevant level, an improved performance (+20%) with elevated getter temperature and an isotope independent sticking coefficient for hydrogen. Furthermore, improved operation experience and regeneration prediction tools have been developed. Employing the experimental results, a simulation task was performed and the sticking factor of the getter cartridge was determined with 7%.

Topological effects exist from a macroscopic system such as the universe to a microscopic system described by quantum mechanics. We show here that an interesting geometric structure can be created by the self-replication procedure of a square with an enclosed circle, in which the sum of the circles' area will remain the same but the sum of the circumference will increase. It is demonstrated by means of Monte Carlo simulations that these topological features have a great impact on the vacuum pumping probability and the photon absorption probability of the active surface. The results show significant improvement of the system performance and have application potential in vacuum pumping of large research facilities such as a nuclear fusion reactor, synchrotron, and in the photovoltaic industry.