Commissioning of the vacuum system of the KATRIN Main Spectrometer

The KATRIN experiment will probe the neutrino mass by measuring the β-electron energy spectrum near the endpoint of tritium β-decay. An integral energy analysis will be performed by an electro-static spectrometer (``Main Spectrometer''), an ultra-high vacuum vessel with a length of 23.2 m, a volume of 1240 m[superscript 3], and a complex inner electrode system with about 120 000 individual parts. The strong magnetic field that guides the β-electrons is provided by super-conducting solenoids at both ends of the spectrometer. Its influence on turbo-molecular pumps and vacuum gauges had to be considered. A system consisting of 6 turbo-molecular pumps and 3 km of non-evaporable getter strips has been deployed and was tested during the commissioning of the spectrometer. In this paper the configuration, the commissioning with bake-out at 300 °C, and the performance of this system are presented in detail. The vacuum system has to maintain a pressure in the 10[superscript −11] mbar range. It is demonstrated that the performance of the system is already close to these stringent functional requirements for the KATRIN experiment, which will start at the end of 2016.United States. Department of Energy (DE-FG02-97ER41020)United States. Department of Energy (DE-FG02-94ER40818)United States. Department of Energy (DE-SC0004036)United States. Department of Energy (DE-FG02-97ER41041)United States. Department of Energy (DE-FG02-97ER41033

Kassiopeia: A Modern, Extensible C++ Particle Tracking Package

The Kassiopeia particle tracking framework is an object-oriented software package using modern C++ techniques, written originally to meet the needs of the KATRIN collaboration. Kassiopeia features a new algorithmic paradigm for particle tracking simulations which targets experiments containing complex geometries and electromagnetic fields, with high priority put on calculation efficiency, customizability, extensibility, and ease of use for novice programmers. To solve Kassiopeia's target physics problem the software is capable of simulating particle trajectories governed by arbitrarily complex differential equations of motion, continuous physics processes that may in part be modeled as terms perturbing that equation of motion, stochastic processes that occur in flight such as bulk scattering and decay, and stochastic surface processes occuring at interfaces, including transmission and reflection effects. This entire set of computations takes place against the backdrop of a rich geometry package which serves a variety of roles, including initialization of electromagnetic field simulations and the support of state-dependent algorithm-swapping and behavioral changes as a particle's state evolves. Thanks to the very general approach taken by Kassiopeia it can be used by other experiments facing similar challenges when calculating particle trajectories in electromagnetic fields. It is publicly available at https://github.com/KATRIN-Experiment/Kassiopei

Single-Electron Detection and Spectroscopy via Relativistic Cyclotron Radiation

It has been understood since 1897 that accelerating charges must emit electromagnetic radiation. Although first derived in 1904, cyclotron radiation from a single electron orbiting in a magnetic field has never been observed directly. We demonstrate single-electron detection in a novel radio-frequency spectrometer. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay end point, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments

Focal-plane detector system for the KATRIN experiment

The focal-plane detector system for the KArlsruhe TRItium Neutrino (KATRIN) experiment consists of a multi-pixel silicon p-i-n-diode array, custom readout electronics, two superconducting solenoid magnets, an ultra high-vacuum system, a high-vacuum system, calibration and monitoring devices, a scintillating veto, and a custom data-acquisition system. It is designed to detect the low-energy electrons selected by the KATRIN main spectrometer. We describe the system and summarize its performance after its final installation.Comment: 28 pages. Two figures revised for clarity. Final version published in Nucl. Inst. Meth.

Techniques for direct neutrino mass measurement utilizing tritium [beta]-decay

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2015.In title on title-page, "[beta]" appears as the lower-case Greek letter. Cataloged from PDF version of thesis.Includes bibliographical references (pages 265-270).This thesis documents efforts performed in the service to two direct neutrino mass experiments, namely KATRIN at the Karlsruhe Institute of Technology in Karlsruhe, Germany and Project8 at the University of Washington in Seattle. These experiments aim to utilize a measurement of the shape of the endpoint of the tritium beta decay spectrum to determine the neutrino mass, which is a technique that relies only on basic kinematics and enjoys a long and distinguished history. Additionally, these experiments utilize classical electrodynamics in their analysis of the beta electron spectrum, at KATRIN through the use of a MAC-E filter and at Project8 through magnetic confinement of electrons within a waveguide and the measurement of their weakly energy dependent relativistic cyclotron frequencies, which is an entirely new technique. In the thesis, both experiments are described in detail with particular attention paid to the components involved in energy analysis. Exploiting these experiments' similarities, an extensive simulation package called KASSIOPEIA has been prepared, which is the principal effort described herein. KASSIOPEIA is applied to both KATRIN and Project8, which in the case of KATRIN delivers valuable and detailed information regarding the performance of the electrostatic spectrometers used there, in particular the main and monitor spectrometers. In its application to Project8, KASSIOPEIA is used to determine precise electron trajectories, which can be used to simulate the signals these electrons induce in the waveguide. This thesis also includes experimental results obtained at the monitor spectrometer of the KATRIN experiment, which demonstrate the efficacy of the magnetic pulse technique at ejecting problematic stored electrons at MAc-E filters. The magnetic pulse technique relies on using a set of external aircoils surrounding a MAC-E filter to reverse and rapidly restore the magnetic field in the spectrometer symmetry plane, causing stored particle to hit the vessel walls. Owing to its success as demonstrated in this work, this technique will be employed at the main spectrometer during the upcoming data taking run at KATRIN. Finally, this thesis presents some results from the inaugural run at Project8, which showed that the theretofore undemonstrated technique, named Cyclotron Radiation Emission Spectroscopy (CRES), is capable of detecting the signal a single electron excites in a waveguide as it its magnetically trapped inside. In the history of tritium based neutrino mass experiments this technique is unique, and presents an entirely complimentary approach to that used at KATRIN. Based as it is on a frequency measurement, the technique shows great promise to mature into an extremely high precision form of electron spectroscopy, with many applications throughout nuclear physics.by Daniel Lawrence Furse.Ph. D

The ecological status of European rivers: evaluation and intercalibration of assessment methods

Foreword to thematic issu

Ecological relationships between stream communities and spatial scale: implications for designing catchment-level monitoring programmes

1. Stream communities are structured by factors acting over multiple spatial and temporal scales. Identifying what factors are driving spatial patterns in stream communities is a central aim of ecology. 2. Here we used two large European data sets of fish, invertebrates, macrophytes, benthic diatoms and environmental data in two stream groups (lowland and mountain) to determine the importance of variables at different spatial scales (geographical, regional, local) on community structure. 3. Both geographical position and ecoregion were selected first in canonical correspondence analysis (CCA), clearly showing the broad spatial gradients covered in the data set. Secondary predictors (after accounting for spatial and/or ecoregion effects) were similar between stream groups and among the four organism groups. In particular, conductivity and N concentration were strong predictors reflecting catchment land use. 4. Using partial CCA, we assessed the individual importance of the three spatial scales on the community structure of the four organism groups in the two stream groups. The majority of among-site variability (22–29%) was accounted for by local scale variables (e.g. water chemistry and substratum type), with regional and spatial variables accounting 11–13% and 5–6%, respectively. Our findings indicate that the four organism groups are responding similarly to the different levels of spatial scale, implying much redundancy which should be consider when implementing studies of bioassessment

Detection of ecological change using multiple organism groups: metrics and uncertainty

A number of biological approaches are commonly used to assess the ecological integrity of stream ecosystems. Recently, it is becoming increasingly common to use multiple organism groups in bioassessment. Advocates of the multiple organism approach argue that the use of different organism groups should strengthen inference-based models and ultimately result in lower assessment error, while opponents argue that organism groups often respond similarly to stress implying a high degree of redundancy. Using fish, macroinvertebrate, macrophyte and benthic diatom data, site-specific parameters (e.g., water chemistry and substratum) and catchment variables from European mountain (n = 77) and lowland (n = 85) streams we evaluated the discriminatory power and uncertainty associated with the use of a number of biological metrics commonly used in stream assessment. The primary environmental gradient for both streams types was land use and nutrient enrichment. Secondary and tertiary gradients were related to habitat quality or alterations in hydromorphology. Benthic diatom and macroinvertebrate metrics showed high discriminatory power (R2 values often >0.50) and low error (<30%) with the primary (nutrient) gradient, while both fish and macrophyte metrics performed relatively poorly. Conversely, both fish and macrophyte metrics showed higher response (high coefficients of determination) than either benthic diatom or macroinvertebrate metrics to the second (e.g., alteration in habitat/hydromorphology) gradient. However, the discriminatory power and error associated with individual metrics varied markedly, indicating that caution should be exercised when selecting the ‘best’ organism group or metric to monitor stres

Improved Upper Limit on the Neutrino Mass from a Direct Kinematic Method by KATRIN

© 2019 authors. Published by the American Physical Society. We report on the neutrino mass measurement result from the first four-week science run of the Karlsruhe Tritium Neutrino experiment KATRIN in spring 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution MAC-E filter. A fit of the integrated electron spectrum over a narrow interval around the kinematic end point at 18.57 keV gives an effective neutrino mass square value of (-1.0-1.1+0.9) eV2. From this, we derive an upper limit of 1.1 eV (90% confidence level) on the absolute mass scale of neutrinos. This value coincides with the KATRIN sensitivity. It improves upon previous mass limits from kinematic measurements by almost a factor of 2 and provides model-independent input to cosmological studies of structure formation