[en] To cool ion beams in the heavy ion storage ring CRYRING and thus achieve a low momentum spread, CRYRING features an electron cooler, where the ion beam is superimposed with a monoenergetic electron beam. In order to calculate the velocity of the electrons and therefore of the cooled ion beam, it is mandatory to continously monitor the cooler voltage with a high-precision divider. For that purpose a high-precision voltage divider for voltages up to 35 kV is currently being constructed in Muenster, similar in design to the ultrahigh-precision voltage dividers in use at the KATRIN experiment. The precision of the divider will be in the low ppm range and will, if other sources of systematic uncertainties like e.g. space charge effects are under control, allow for measurement uncertainties in the < 10^-5 region. Special care is taken to ensure a fast time response of the divider, for measurements where the cooler voltage is modified in regular intervals.

[en] The heavy ion storage ring CRYRING at GSI provides a unique possibility to test atomic structure calculations with slow exotic ion beams at energies in the range of 0.3 MeV/u up to 15 MeV/u. In order to cool the ions and thus achieve a low momentum spread of the stored beam, CRYRING features an electron cooler, where the ion beam is superimposed with a monoenergetic electron beam. In earlier measurements of hyperfine transitions in hydrogen- and lithium-like ions at Experimental Storage Ring (ESR), the limiting uncertainty was the voltage measurement of the electron cooler which determines the velocity of the ions. That uncertainty could be removed by an in-situ precision measurement of the cooler voltage using a high voltage divider provided by PTB on a temporary basis. We therefore plan to construct a high-precision divider for voltages up to 35 kV which will be similar to the ultrahigh-precision voltage dividers which have been constructed for use at the KATRIN experiment. The precision of the divider will be in the low ppm range and will allow for measurement uncertainties in the < 10^-5 region. The concept and first characterization measurements of the precision components are presented.

[en] The heavy ion storage ring CRYRING at GSI provides a unique possibility to test atomic structure calculations with slow exotic ion beams at energies in the range of 0.3 MeV/u up to 15 MeV/u. In order to cool the ions and thus achieve a low momentum spread of the stored beam, CRYRING features an electron cooler, where the ion beam is superimposed with a monoenergetic electron beam. In earlier measurements of hyperfine transitions in hydrogen- and lithiumlike ions at Experimental Storage Ring (ESR), the limiting uncertainty was the voltage measurement of the electron cooler. That uncertainty could be removed by an in-situ precision measurement of the cooler voltage using a precision high voltage divider provided by PTB on a temporary basis. Therefore the construction of a high-precision divider for voltages up to 35 kV for the CRYRING electron cooler is ongoing in our group. The concept is similar to the ultrahigh-precision voltage dividers which have been constructed for use at the KATRIN experiment. The precision of the divider is designed to be in the low ppm range and will allow for measurement uncertainties in the < 10^-5 region. We present characterization measurements of the precision parts and first calibration measurements of the finished divider.

[en] The KATRIN experiment will measure the absolute mass scale of neutrinos with a sensitivity of m_ν = 200meV/c² by means of an electrostatic spectrometer set close to the tritium β-decay endpoint at 18.6keV. Fluctuations of the energy scale must be under control within ±60mV (±3ppm). Since a precise voltage measurement in the range of tens of kV is on the edge of current technology, a nuclear standard will be deployed additionally. Parallel to the main spectrometer the same retarding potential will be applied to the monitor spectrometer to measure 17.8-keV K-conversion electrons of ^83mKr. This article describes the setup of the monitor spectrometer and presents its first measurement results

[en] The KATRIN experiment aims to determine the neutrino mass scale with a sensitivity of 200 meV/c"2 (90% C.L.) by a precision measurement of the shape of the tritium β-spectrum in the endpoint region. The energy analysis of the decay electrons is achieved by a MAC-E filter spectrometer. To determine the transmission properties of the KATRIN main spectrometer, a mono-energetic and angular-selective electron source has been developed. In preparation for the second commissioning phase of the main spectrometer, a measurement phase was carried out at the KATRIN monitor spectrometer where the device was operated in a MAC-E filter setup for testing. The results of these measurements are compared with simulations using the particle-tracking software ''Kassiopeia'', which was developed in the KATRIN collaboration over recent years. (orig.)

[en] The neutrino mass experiment KATRIN requires a stability of 3 ppm for the retarding potential at - 18.6 kV of the main spectrometer. To monitor the stability, two custom-made ultra-precise high-voltage dividers were developed and built in cooperation with the German national metrology institute Physikalisch-Technische Bundesanstalt (PTB). Until now, regular absolute calibration of the voltage dividers required bringing the equipment to the specialised metrology laboratory. Here we present a new method based on measuring the energy difference of two ^83mKr conversion electron lines with the KATRIN setup, which was demonstrated during KATRIN's commissioning measurements in July 2017. The measured scale factor M = 1972.449(10) of the high-voltage divider K35 is in agreement with the last PTB calibration 4 years ago. This result demonstrates the utility of the calibration method, as well as the long-term stability of the voltage divider. (orig.)

[en] The KATRIN experiment aims to determine the effective electron neutrino mass with a sensitivity of 0.2 eV/c² (%90 CL) by precision measurement of the shape of the tritium β-spectrum in the endpoint region. The energy analysis of the decay electrons is achieved by a MAC-E filter spectrometer. A common background source in this setup is the decay of short-lived isotopes, such as ²¹⁹Rn and ²²⁰Rn, in the spectrometer volume. Active and passive countermeasures have been implemented and tested at the KATRIN main spectrometer. One of these is the magnetic pulse method, which employs the existing air coil system to reduce the magnetic guiding field in the spectrometer on a short timescale in order to remove low- and high-energy stored electrons. Here we describe the working principle of this method and present results from commissioning measurements at the main spectrometer. Simulations with the particle-tracking software Kassiopeia were carried out to gain a detailed understanding of the electron storage conditions and removal processes. (orig.)