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Abstract. The most sensitive direct method to establish the absolute neutrino mass is observation of the endpoint of the tritium beta-decay spectrum. Cyclotron Radiation Emission Spectroscopy (CRES) is a precision spectrographic technique that can probe much of the unexplored neutrino mass range with O(eV) resolution. A lower bound of m(ν e ) 9(0.1) meV is set by observations of neutrino oscillations, while the KATRIN Experiment -the current-generation tritium beta-decay experiment that is based on Magnetic Adiabatic Collimation with an Electrostatic (MAC-E) filter -will achieve a arXiv:1703.02037v1 [physics.ins-det]

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. For over a century, nuclear decay electron spectroscopy has played a pivotal role in the understanding of nuclear physics. Early measurements of the continuous β-decay spectrum [1] provided the first evidence of the existence of the weak force and the neutrino [2], and immediately hinted that the neutrino mass is small. Continuing this tradition, present efforts to directly measure the mass of the neutrino rely on precision spectroscopy of the β-decay energy spectrum of 3 H. Because the value of the neutrino mass is an input to the standard model of particle physics as well as precision cosmology, a precision measurement of the neutrino mass would represent a significant advance in our description of nature.The sensitivity of 3 H -based neutrino mass measurements has been improving over the past 80 years as a result of increasingly powerful electron spectrometry techniques [3][4][5][6]. The most sensitive experiments to date place a limit on the electron-flavor-weighted neutrino mass m β ≤ 2.05 eV=c 2 at 95% C.L. [7][8][9], m 2 β ¼

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.

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 KASSIOPEIAʼs 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 occurring 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/Kassiopeia.