arXiv subjects

Hans-Werner Ortjohann

Publications and source records attributed to Hans-Werner Ortjohann.

4 recordsLinked to original sources

arXiv2026

A precision 32 keV angular-selective photoelectron source for calibration measurements at the KATRIN experiment

The Karlsruhe Tritium Neutrino (KATRIN) experiment measures the neutrino mass from a precise measurement of the endpoint region of the kinematic tritium beta-decay spectrum by using a spectrometer combining magnetic adiabatic collimation and electrostatic filtering (MAC-E filter). For calibration purposes, KATRIN uses a monoenergetic angular-selective photoelectron source. We present an upgrade of this source, which was installed in the KATRIN beamline in February 2022. The source allows for a wide range of accessible electron energies up to 32 keV and a variation of the angle with regard to the magnetic field. These features are used for precise measurements of electron scattering effects off tritium molecules in KATRIN's gaseous tritium source, for investigations of angular-dependent backscattering for example at KATRIN's focal-plane detector, and for studies on adiabatic transport in the main spectrometer.

physics.ins-det↗

arXiv2018

Magnetically-coupled piston pump for high-purity gas applications

Experiments based on noble elements such as gaseous or liquid argon or xenon utilize the ionization and scintillation properties of the target materials to detect radiation-induced recoils. A requirement for high light and charge yields is to reduce electronegative impurities well below the ppb level. To achieve this, the target material is continuously circulated in the gas phase through a purifier and returned to the detector. Additionally, the low backgrounds necessary dictate low-Rn-emanation rates from all components that contact the gas. Since commercial pumps often introduce electronegative impurities from lubricants on internal components or through small air leaks, and are not designed to meet the radiopurity requirements, custom-built pumps are an advantageous alternative. A new pump has been developed in Muenster in cooperation with the nEXO group at Stanford University and the nEXO/XENON group at Rensselaer Polytechnic Institute based on a magnetically-coupled piston in a hermetically sealed low-Rn-emanating vessel. This pump delivers high performance for noble gases, reaching more than 210 standard liters per minute (slpm) with argon and more than 170 slpm with xenon while maintaining a compression of up to 1.9 bar, demonstrating its capability for noble gas detectors and other applications requiring high standards of gas purity.

physics.ins-det↗

arXiv2014

Determination of hydrogen cluster velocities and comparison with numerical calculations

The use of powerful hydrogen cluster jet targets in storage ring experiments led to the need of precise data on the mean cluster velocity as function of the stagnation temperature and pressure for the determination of the volume density of the target beams. For this purpose a large data set of hydrogen cluster velocity distributions and mean velocities was measured at a high density hydrogen cluster jet target using a trumpet shaped nozzle. The measurements have been performed at pressures above and below the critical pressure and for a broad range of temperatures relevant for target operation, e.g., at storage ring experiments. The used experimental method is described which allows for the velocity measurement of single clusters using a time-of-flight technique. Since this method is rather time-consuming and these measurements are typically interfering negatively with storage ring experiments, a method for a precise calculation of these mean velocities was needed. For this, the determined mean cluster velocities are compared with model calculations based on an isentropic one-dimensional van der Waals gas. Based on the obtained data and the presented numerical calculations, a new method has been developed which allows to predict the mean cluster velocities with an accuracy of about 5%. For this two cut-off parameters defining positions inside the nozzle are introduced, which can be determined for a given nozzle by only two velocity measurements.

physics.atm-clus↗

arXiv2011

High density cluster jet target for storage ring experiments

The design and performance of a newly developed cluster jet target installation for hadron physics experiments are presented which, for the first time, is able to generate a hydrogen cluster jet beam with a target thickness of above $10^{15}\,\mathrm{atoms/cm}^2$ at a distance of two metres behind the cluster jet nozzle. The properties of the cluster beam and of individual clusters themselves are studied at this installation. Special emphasis is placed on measurements of the target beam density as a function of the relevant parameters as well as on the cluster beam profiles. By means of a time-of-flight setup, measurements of the velocity of single clusters and velocity distributions were possible. The complete installation, which meets the requirements of future internal fixed target experiments at storage rings, and the results of the systematic studies on hydrogen cluster jets are presented and discussed.

physics.ins-det↗