Characterization and Optimization of the KATRIN Tritium Source

The Karlsruhe Tritium Neutrino (KATRIN) experiment aims to measure the effective electron anti-neutrino mass via high-precision spectroscopy of the energy spectrum of $\beta$-decay electrons of tritium near the 18.6 keV endpoint with an unprecedented accuracy. The specifications of the KATRIN experiment result in an experimental setup with a target discovery potential of 5 $\sigma$ for a neutrino mass of 350 meV/c$^{-2}$ and the expected capability to push the upper limit on the neutrino mass down to a target of 200 meV/c$^{-2}$ (90 % C. L.) if no neutrino mass signal is detected. To achieve this unprecedented sensitivity, both statistical and systematical uncertainties have to be stringently minimized. The reduction of statistical uncertainties requires a total measurement duration of 3 years with a windowless gaseous tritium source (WGTS) capable of producing $10^{11}$ $\beta$-electrons per second. To keep the systematical uncertainties at the level required to reach the target sensitivity, the activity of this $\beta$-electron source needs to be stable at the level of 0.1%. This stability is influenced by several factors such as the purity and pressure of the tritium gas, as well as the temperature of the WGTS beam tube enclosing the gaseous tritium. Therefore, in order to minimize systematical uncertainties, a very stable injection of tritium gas into the beam tube is necessary. This is achieved by the tritium loop system. The main focus of this thesis is the optimization of stabilized injection of tritium gas into the WGTS, the in-depth characterization and modeling of the isotopic gas composition inside of the WGTS, as well as the measurement and continuous monitoring methods of the WGTS column density. Summarizing the results presented in this thesis, it was shown that the stability of the tritium column density of the WGTS meets the requirement of 0.1%. A variety of column density monitoring methods were implemented and have been used to derive the best current upper limit on the neutrino mass from direct measurement of 1.1 eV/c$^{-2}$. This outstanding performance in both stability and monitoring can be achieved reliably and reproducibly. This is necessary for the upcoming measurement campaigns, which are needed by the KATRIN experiment in order to meet its scientific goal of a 200 meV/c$^{-2}$ sensitivity on the neutrino mass

µRA : A New Compact Easy-to-Use Raman System for All Hydrogen Isotopologues

We have developed a new compact and cost-efficient Laser-Raman system for the simultaneous measurement of all six hydrogen isotopologues. The focus of this research was set on producing a tool that can be implemented in virtually any existing setup providing in situ process control and analytics. The “micro Raman (µRA)” system is completely fiber-coupled for an easy setup consisting of (i) a spectrometer/CCD unit, (ii) a 532 nm laser, and (iii) a commercial Raman head coupled with a newly developed, tritium-compatible all-metal sealed DN16CF flange/Raman window serving as the process interface. To simplify the operation, we developed our own software suite for instrument control, data acquisition, and data evaluation in real-time. We have given a detailed description of the system, showing the system’s capabilities in terms of the lower level of detection, and presented the results of a dedicated campaign using the accurate reference mixtures of all of the hydrogen isotopologues benchmarking µRA against two of the most sensitive Raman systems for tritium operation. Due to its modular nature, modifications that allow for the detection of various other gas species can be easily implemented

ViMA -- the spinning rotor gauge to measure the viscosity of tritium between 77 and 300 K

Experimental values for the viscosity of the radioactive hydrogen isotope tritium (T$_2$) are currently unavailable in literature. The value of this material property over a wide temperature range is of interest for applications in the field of fusion, neutrino physics, as well as to test ab initio calculations. As a radioactive gas, tritium requires careful experiment design to ensure safe and environmental contamination free measurements. In this contribution, we present a spinning rotor gauge based, tritium compatible design of a gas viscosity measurement apparatus (ViMA) capable of covering the temperature range from 80 K to 300 K.Comment: 11 pages, 3 figures, Tritium Conference 202

Towards the first direct measurement of the dynamic viscosity of gaseous tritium at cryogenic temperatures

Accurate values for the viscosity of the radioactive hydrogen isotope tritium (T) at cryogenic temperatures are unavailable. Values for tritium found in literature are based on extrapolation by mass ratios as well as an empirical factor derived from hydrogen (H) and deuterium (D ) viscosity measurements, or classical kinetic theory which does not handle quantum effects. Accurate data of the tritium viscosity will help to improve the modelling of the viscosity of diatomic molecules and can be used as a test of their interaction potentials. With this contribution we report a major step towards a fully tritium and cryogenic temperature compatible setup for the accurate measurement of the viscosity of gases, using a spinning rotor gauge (SRG) at the Tritium Laboratory Karlsruhe. After calibration with helium, measurements with hydrogen and deuterium conducted at room temperature agree with literature values within 2%. The performance at liquid nitrogen (LN ) temperature has been successfully demonstrated with a second setup in a liquid nitrogen bath. Again after calibration with helium at LN temperature, the viscosities of H and D were determined and are in agreement with literature to about 2%

Viscosity measurements of gaseous H2 between 200 K to 300 K with a spinning rotor gauge

Experimental values for the viscosity of the radioactive hydrogen isotopologue tritium are still unknown in literature. Existing values from ab initio calculations disregard quantum mechanic effects and are therefore only good approximations for room temperature and above. To fill in these missing experimental values, a measurement setup has been designed, to measure the viscosity of gaseous hydrogen and its isotopologues (H$_2$, HD, HT, D$_2$, DT, T$_2$) at cryogenic temperatures. In this paper, the first results with this Cryogenic Viscosity Measurement Apparatus (Cryo-ViMA) of the viscosity of gaseous hydrogen between 200 K to 300 K are presented.Comment: 9 pages, 2 figures, 22nd International Vacuum Congress, submitted to e-Journal of Surface Science and Nanotechnolog

Multilevel Interventions To Address Health Disparities Show Promise In Improving Population Health

Multilevel interventions are those that affect at least two levels of influence—for example, the patient and the health care provider. They can be experimental designs or natural experiments caused by changes in policy, such as the implementation of the Affordable Care Act or local policies. Measuring the effects of multilevel interventions is challenging, because they allow for interaction among levels, and the impact of each intervention must be assessed and translated into practice. We discuss how two projects from the National Institutes of Health’s Centers for Population Health and Health Disparities used multilevel interventions to reduce health disparities. The interventions, which focused on the uptake of the human papillomavirus vaccine and community-level dietary change, had mixed results. The design and implementation of multilevel interventions are facilitated by input from the community, and more advanced methods and measures are needed to evaluate the impact of the various levels and components of such interventions

Kilogram scale throughput performance of the KATRIN tritium handling system

The Karlsruhe Tritium Neutrino (KATRIN) experiment aims to determine the effective mass of the electron antineutrino by investigating the tritium β-spectrum close to the energetic endpoint. To achieve this, there are stringent and challenging requirements on the stability of the gaseous tritium source. The tritium loop system has the task to provide the 95 %. KATRIN started full tritium operation in early 2019. This paper focusses on the observed radiochemical effects and confirms that non-negligible quantities during initial tritium operation have to be expected