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Since the discovery of neutrino oscillations, we know that neutrinos have non-zero mass. However, the absolute neutrino-mass scale remains unknown. Here we report the upper limits on effective electron anti-neutrino mass, mν, from the second physics run of the Karlsruhe Tritium Neutrino experiment. In this experiment, mν is probed via a high-precision measurement of the tritium β-decay spectrum close to its endpoint. This method is independent of any cosmological model and does not rely on assumptions whether the neutrino is a Dirac or Majorana particle. By increasing the source activity and reducing the background with respect to the first physics campaign, we reached a sensitivity on mν of 0.7 eV c–2 at a 90% confidence level (CL). The best fit to the spectral data yields $${{\mbox{}}}{m}_{\nu }^{2}{{\mbox{}}}$$ m ν 2  = (0.26 ± 0.34) eV2 c–4, resulting in an upper limit of mν < 0.9 eV c–2 at 90% CL. By combining this result with the first neutrino-mass campaign, we find an upper limit of mν < 0.8 eV c–2 at 90% CL.

Molecular semiconductors are increasingly used in devices, but understanding of elementary nanoscopic processes in molecular film growth is in its infancy. Here we use real-time in situ specular and diffuse X-ray scattering in combination with kinetic Monte Carlo simulations to study C60 nucleation and multilayer growth. We determine a self-consistent set of energy parameters describing both intra- and interlayer diffusion processes in C60 growth. This approach yields an effective Ehrlich–Schwoebel barrier of EES=110 meV, diffusion barrier of ED=540 meV and binding energy of EB=130 meV. Analysing the particle-resolved dynamics, we find that the lateral diffusion is similar to colloids, but characterized by an atom-like Schwoebel barrier. Our results contribute to a fundamental understanding of molecular growth processes in a system, which forms an important intermediate case between atoms and colloids.

Single-phase ZnCdO alloys with a band gap extending from the violet to yellow spectral range are fabricated by molecular beam epitaxy using extremely low growth temperatures in conjunction with O-rich growth conditions. The Cd concentration can be systematically adjusted via the Cd∕Zn beam pressure ratio. Despite growth temperatures as low as 150°C, layer-by-layer growth is accomplished allowing for the preparation of ZnCdO∕ZnO quantum well structures. Both epilayers and quantum wells exhibit strong band-gap-related emission at room temperature in the whole composition range.

The KArlsruhe TRItium Neutrino (KATRIN) experiment, which aims to make a direct and model-independent determination of the absolute neutrino mass scale, is a complex experiment with many components. More than 15 years ago, we published a technical design report (TDR) [1] to describe the hardware design and requirements to achieve our sensitivity goal of 0.2 eV at 90% C.L. on the neutrino mass. Since then there has been considerable progress, culminating in the publication of first neutrino mass results with the entire beamline operating [2]. In this paper, we document the current state of all completed beamline components (as of the first neutrino mass measurement campaign), demonstrate our ability to reliably and stably control them over long times, and present details on their respective commissioning campaigns. K: Beam-line instrumentation (beam position and profile monitors, beam-intensity monitors, bunch length monitors); Spectrometers; Gas systems and purification; Neutrino detectors A X P : 2103.04755Neutrino-mass mode. This is the standard mode of operation to continually adjust the retarding voltage of the MS in the range of [ 0 − 40 eV; 0 + 50 eV] while tritium is in the system. This scanning range can be adjusted if required. The voltage and the time spent at each setting are defined by the Measurement Time Distribution (MTD) (figure 3). A typical run at a given voltage lasts between 20 s and 600 s; a full scan of the energy range given above takes about 2 h. Of these standard neutrino-mass runs, a small portion will be dedicated to sterile neutrino searches. These searches involve scanning much farther (order of keV) below the endpoint 0 .Calibration mode. To check the long-term system stability, calibration measurements are done regularly. The neutrino-mass mode is suspended for the duration of these measurement:• An energy calibration of the FPD (section 6) is performed weekly, which requires closing off the detector system from the main beamline for about 4 h.• The offset and the gain correction factor of the low-voltage readout in the high-voltage measurement chain needs to be calibrated based on standard reference sources (section 5.3.4). This requires stopping the precision monitoring of the MS retarding potential twice per week for about 0.5 h each.