•A cryogenic test facility for helium operation in forced-flow mode was built.•Helium at 4.5K and 20–70K, simultaneously, can be provided.•Test setup provides supply current up to 50kA DC and ...withstand voltage of 50kV DC.•The cryogenic, electrical and process control setup is described in detail.•Experiences during installation and commissioning are presented.
The Karlsruhe Institute of Technology (KIT) has a longtime experience in the development of High Temperature Superconductor (HTS) Current Leads (CLs) for high currents leading to several contracts with national and international partners. Within these contracts series production and cold acceptance tests of such CLs were required. The cold test of a large number of CLs requires the availability of a flexible facility which allows fast and reproducible testing.
With the Current Lead Test Facility Karlsruhe (CuLTKa) a versatile and flexible test bed for CLs was designed and constructed. The facility consists of five cryostats including two test boxes and is directly connected by a transfer line to a refrigerator with a capacity of 2kW at 4.4K. The refrigerator supplies supercritical helium at two different temperature levels simultaneously. Each of the two test cryostats can be equipped with a pair of CLs which is short-circuited at the low temperature level via a superconducting bus bar. For current tests a power supply can provide DC currents up to 30kA. If required, the facility design offers the potential of withstanding high voltages of up to 50kV on the test objects.
The commissioning of the facility started in July 2014. In total a series of acceptance tests of the CLs for the Japanese JT-60SA will be carried out until second half of 2017 to qualify six CLs with a current of 26kA and 20 CLs with a current of 20kA. In the meantime, six CLs@26kA and 16 CLs@20kA have been tested in CuLTKa which demonstrates the very effective operation of the facility.
This paper describes the setup of the facility from cryogenic, electrical and process control point of view and will highlight the design of particular technical aspects. Furthermore, an overview of the performance during the commissioning phase will be given.
In this work, we present the first spectroscopic measurements of conversion electrons originating from the decay of metastable gaseous 83mKr with the Karlsruhe Tritium Neutrino (KATRIN) experiment. ...The obtained results represent one of the major commissioning milestones for the subsequent direct neutrino mass measurement with KATRIN. The successful campaign demonstrates the functionalities of the KATRIN beamline. Precise measurement of the narrow K-32, L3-32, and N2,3-32 conversion electron lines allowed to verify the eV-scale energy resolution of the KATRIN main spectrometer necessary for competitive measurement of the absolute neutrino mass scale.
The fact that neutrinos carry a non-vanishing rest mass is evidence of physics beyond the Standard Model of elementary particles. Their absolute mass bears important relevance from particle physics ...to cosmology. In this work, we report on the search for the effective electron antineutrino mass with the KATRIN experiment. KATRIN performs precision spectroscopy of the tritium \(\beta\)-decay close to the kinematic endpoint. Based on the first five neutrino-mass measurement campaigns, we derive a best-fit value of \(m_\nu^{2} = {-0.14^{+0.13}_{-0.15}}~\mathrm{eV^2}\), resulting in an upper limit of \(m_\nu < {0.45}~\mathrm{eV}\) at 90 % confidence level. With six times the statistics of previous data sets, amounting to 36 million electrons collected in 259 measurement days, a substantial reduction of the background level and improved systematic uncertainties, this result tightens KATRIN's previous bound by a factor of almost two.
The Karlsruhe Tritium Neutrino (KATRIN) experiment is designed to measure a high-precision integral spectrum of the endpoint region of T2 beta decay, with the primary goal of probing the absolute ...mass scale of the neutrino. After a first tritium commissioning campaign in 2018, the experiment has been regularly running since 2019, and in its first two measurement campaigns has already achieved a sub-eV sensitivity. After 1000 days of data-taking, KATRIN's design sensitivity is 0.2 eV at the 90% confidence level. In this white paper we describe the current status of KATRIN; explore prospects for measuring the neutrino mass and other physics observables, including sterile neutrinos and other beyond-Standard-Model hypotheses; and discuss research-and-development projects that may further improve the KATRIN sensitivity.
In this work we present a keV-scale sterile-neutrino search with the first
tritium data of the KATRIN experiment, acquired in the commissioning run in
2018. KATRIN performs a spectroscopic ...measurement of the tritium $\beta$-decay
spectrum with the main goal of directly determining the effective electron
anti-neutrino mass. During this commissioning phase a lower tritium activity
facilitated the search for sterile neutrinos with a mass of up to $1.6\,
\mathrm{keV}$. We do not find a signal and set an exclusion limit on the
sterile-to-active mixing amplitude of down to $\sin^2\theta < 5\cdot10^{-4}$
($95\,\%$ C.L.), improving current laboratory-based bounds in the
sterile-neutrino mass range between 0.1 and $1.0\, \mathrm{keV}$.
Some extensions of the Standard Model of Particle Physics allow for Lorentz invariance and Charge-Parity-Time (CPT)-invariance violations. In the neutrino sector strong constraints have been set by ...neutrino-oscillation and time-of-flight experiments. However, some Lorentz-invariance-violating parameters are not accessible via these probes. In this work, we focus on the parameters \((a_{\text{of}}^{(3)})_{00}\), \((a_{\text{of}}^{(3)})_{10}\) and \((a_{\text{of}}^{(3)})_{11}\) which would manifest themselves in a non-isotropic beta-decaying source as a sidereal oscillation and an overall shift of the spectral endpoint. Based on the data of the first scientific run of the KATRIN experiment, we set the first limit on \(\left|(a_{\text{of}}^{(3)})_{11}\right|\) of \(< 3.7\cdot10^{-6}\) GeV at 90\% confidence level. Moreover, we derive new constraints on \((a_{\text{of}}^{(3)})_{00}\) and \((a_{\text{of}}^{(3)})_{10}\).
We report on the direct cosmic relic neutrino background search from the first two science runs of the KATRIN experiment in 2019. Beta-decay electrons from a high-purity molecular tritium gas source ...are analyzed by a high-resolution MAC-E filter around the kinematic endpoint at 18.57 keV. The analysis is sensitive to a local relic neutrino overdensity of 9.7e10 (1.1e11) at a 90% (95%) confidence level. A fit of the integrated electron spectrum over a narrow interval around the kinematic endpoint accounting for relic neutrino captures in the Tritium source reveals no significant overdensity. This work improves the results obtained by the previous kinematic neutrino mass experiments at Los Alamos and Troitsk. We furthermore update the projected final sensitivity of the KATRIN experiment to <1e10 at 90% confidence level, by relying on updated operational conditions.
We present the results of the light sterile neutrino search from the second KATRIN measurement campaign in 2019. Approaching nominal activity, \(3.76 \times 10^6\) tritium \(\beta\)-electrons are ...analyzed in an energy window extending down to \(40\,\)eV below the tritium endpoint at \(E_0 = 18.57\,\)keV. We consider the \(3\nu+1\) framework with three active and one sterile neutrino flavor. The analysis is sensitive to a fourth mass eigenstate \(m_4^2\lesssim1600\,\)eV\(^2\) and active-to-sterile mixing \(|U_{e4}|^2 \gtrsim 6 \times 10^{-3}\). As no sterile-neutrino signal was observed, we provide improved exclusion contours on \(m_4^2\) and \(|U_{e4}|^2\) at \(95\,\)% C.L. Our results supersede the limits from the Mainz and Troitsk experiments. Furthermore, we are able to exclude the large \(\Delta m_{41}^2\) solutions of the reactor antineutrino and gallium anomalies to a great extent. The latter has recently been reaffirmed by the BEST collaboration and could be explained by a sterile neutrino with large mixing. While the remaining solutions at small \(\Delta m_{41}^2\) are mostly excluded by short-baseline reactor experiments, KATRIN is the only ongoing laboratory experiment to be sensitive to relevant solutions at large \(\Delta m_{41}^2\) through a robust spectral shape analysis.
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