The Mainz Atomic Test Setup (MATS) should demonstrate the production of cold atomic hydrogen at rates that are needed for a next-generation neutrino mass experiment. The MATS setup uses hydrogen atoms instead of tritium since the atoms behave very similarly and the use of tritium in a University environment is restricted due to its radioactive nature. To produce large amounts of atomic hydrongen methods that are used in atomic physics are not feasible because they produce too little atom flux. In our test stand we dissociate molecular hydrogen by heating it to >2000K which cracks up the molecule into individual atoms. Our Hydrogen Atomic Beam Source (HABS) uses a hot tungstant capillary to crack the molecular hydrogen. The HABS is operated in ultra-high vaccum so that the atomic beam can propergate unattenuated. We plan on additional elements in our atomic beam line to cool down the hot atomic beam and trap it in an atomic beam trap. Many activities in Mainz are around the MATS and are described below.

While working with hydrogen, many of the devices and vacuum components can be readily upgraded or replaced. The same flexibility, however, is not possible when handling tritium, because radioactive contamination protocols are far more stringent. These constraints—together with our shared interest in atomic-tritium research—motivated the formation of the KAMATE collaboration with our colleagues at the Tritium Laboratory Karlsruhe (TLK). The main goal of this collaboration is to take the MATS design and rebuild the setup at TLK for tritium measurements. KAMATE’s milestones are as follows:

• KAMATE 0.5: Identify best atomic hydrogen source and test the need for a tilt mechanism
• KAMATE 1.0: Operate the resulting setup at TLK with Tritium
• KAMATE 2.0: Add and test the accommodator as first stage of cooling
• KAMATE 3.0: Add and test the nozzle as the second stage of cooling and beam temperature measurements.

To improve the atom producitionm, we need to measure and characterize a sources’ properties, make changes, and compare the results. Therefore, we need a varity of beam diagnostics to measure and verify the produced atom flux. We use mass spectrometer specialized on low mass-to-charge ratios and multiple analysis methods to determine the dissociation efficiency . This includes the measurement of the relative atom to molecular hydrogen flux and thus the characterization of the dissociation efficiency. The group in Mainz developed a calorimetric detector based on gold coated wires to measure the hydrogen flux, which allows to measure the spatial beam distribution. For the determination of the dissociation efficiency a measurement of the capilary temperature is needed. We are developing techniques to measure temeratures conratctles in vacuum with ~1K precision. Further we are investigating beam temperature measurements

The CRES technique described above is pioniered by the Project 8 collaboration. Project 8 follows a phased approch with a series of different demonstrator experiments. In Phase II the first neutrino mass measurement using the CRES technique was performed. The group in Mainz significantly contributed to the Data Aquisition (DAQ) system for the readout of the RF frequency. The group determined the detection efficiency as function of kinetic energy by using a mono-energetic line of a meta-stable Krypton isotope and a solenoid to shift the magnetic field and thus the frequency response of the apperatus. The final data analysis using a Frequentist method was developed in Mainz and resulted in the first neutrino mass measurement with a sensitivity of 150 eV.

One major challange for the Project 8 collaboration is to scale up the CRES technique to large volumina to aquire sufficient statistics for a competitive neutrino mass measurement. Therefore the Project 8 collaboration investigated the use of radio frequency antennas to pick up the CRES signal in free space. A Free Space CRES Demonstrator (FSCD) was designed to demonstrate the detection of CRES in free space in a 1L scale active volume. However, the investigations show that the computational needs to reconstruct and detect signals from a huge array of antennas are challanging. The group in Mainz designed the magnetic bottle trap to for CRES electrons for the FSCD, developed an independent simulation tool to simulate CRES events and signals in an antenna array, developed likelihood based reconstruction technique to benchmark the best possible reconstruction resolution and investigated the neutrino mass sensitivity reach of a potential large scale experiment for neutrino mass detection based on antenna arrays in a best case scenario. While a 40meV neutrino mass sensitivity can be reached in such an experiment the computational needs in such an experiment are extremely challanging and an alternative readout scheme based on cavities is now followed.

The radiated power by a single CRES electron is on the aW – fW level depending on the magnetic field strength. To detect electrons based on this little power, the CRES electron has to be observed for a long time (µs – ms) to be detectable and reconstructable. Thus the CRES electron has to be confined in the sensitive part of the apperatus. In CRES experiments this is achived by a magnetic bottle trap, which exhibits two magnetic field bumps in axial direction of the background field. CRES electrons with little axial momentum are thus trapped. The magnetic field trap leads to additional signal features in the CRES signal and introduces additional frequency components. The CRES signal shape and reconstructability thus depends on the magnetic trap shape. For example, the mean experienced magnetic field of a CRES electron depends on its axial momentum and thus the turning points in the magnetic field trap. For high-precision determination of the CRES electron kinetic energy these effects have to be considered. In addition the design of a magnetic bottle trap has to account for technical constraints like available space and heat load on the setup. The group in Mainz is leading the design of the electron trap for several demonstrators. Currently the electron trap for the Cavity CRES apperatus (CCA) is under commissioning at the University at Washington.