Preparatory studies for a high-precision Penning-trap measurement of the 163Ho electron capture Q-value

Abstract

The ECHo Collaboration (Electron Capture 163 Ho) aims to investigate the calorimetric spectrum following the electron capture decay of 163 Ho to determine the mass of the electron neutrino. The size of the neutrino mass is reflected in the endpoint region of the spectrum, i.e., the last few eV below the transition energy. To check for systematic uncertainties, an independent determination of this transition energy, the Q-value, is mandatory. Using the TRIGA-TRAP setup, we demonstrate the feasibility of performing this measurement by Penning-trap mass spectrometry. With the currently available, purified 163 Ho sample and an improved laser ablation mini-RFQ ion source, we were able to perform direct mass measurements of 163 Ho and 163 Dy with a sample size of less than 10 17 atoms. The measurements were carried out by determining the ratio of the cyclotron frequencies of the two isotopes to those of carbon cluster ions using the time-of-flight ion cyclotron resonance method. The obtained mass excess values are ME ( 163 Ho) = −66379.3(9) keV and ME ( 163 Dy) = −66381.7(8) keV. In addition, the Q-value was measured for the first time by Penning-trap mass spectrometry to be Q = 2.5(7) keV.

Towards a He-buffered laser ablation ion source for collinear laser spectroscopy

“…Using low-pressure buffer gas simplifies the differential pumping progress but catches a lower fraction of the ablated ions. While this can be sufficient for trap measurements [8] collinear laser spectroscopy profits from a high number of ions per bunch and especially from a lowemittance beam. This can be achieved by ablating the ions in buffer-gas pressures above 10 mbar and extracting them from the laser ablation chamber into low-pressure conditions through a nozzle in a supersonic gas jet as it is realized in other cases where ions are generated or stopped in high-pressure gas cells by other means.…”

Production, isolation and characterization of radiochemically pure 163Ho samples for the ECHo-project

“…The preparation of the required, isotopically pure samples by mass separation of the Ho samples and the implantation into the MMCs is described in [14]. Separate samples have been prepared for high-precision measurements of the Q EC value of 163 Ho using Penning-Trap Mass Spectrometry (PTMS) [15] to provide a value independent of that evaluated from the energy spectrum, and the corresponding measurement of the Q EC value was recently performed [16].…”

Simulation studies of the laser ablation ion source at the SHIPTRAP setup

“…The target holder can accommodate multiple samples and is driven by a step motor that allows fine rotation in order to scan the position of the same sample as well as to access another target. Once ablated from the surface of the sample, the ions are injected into a mini-RFQ [13], which consists of an injection electrode, four parallel rods and an ejection electrode. Here, it is possible to confine the ions axially by applying electrostatic voltages to the injection electrode, the rods and the ejection electrode in a way that a potential minimum is created in the mini-RFQ volume.…”

“…This requires that the ions are captured and cooled right after the ablation process. To thermalize the laser-ablated ions and to collect them in a bunch, we have implemented a mini-RFQ with a similar design as the one used at the mass spectrometer TRIGA-TRAP [13]. As the name mini-RFQ suggests, it is a very compact device: the four rods are 20 mm long with a diameter 11.5 mm and a rod spacing of 10 mm.…”