Setup and calibration of a position sensitive microchannel plate detector and analysis of a test run optimizing the WITCH experiment

Die Beta-Neutrino-Winkelkorrelation ist sehr sensitiv auf exotische Wechselwirkungen und kann über die Form des Rückstoßenergiespektrums der Tochterkerne nach dem Beta-Zerfall bestimmt werden. Hierzu werden Ionen in einer Penningfalle gespeichert und die Rückstoßenergie der Tochterkerne mit Hilfe eines MAC-E-Filters bestimmt. Für den Nachweis der Rückstoßionen wird ein positionsempfindlicher MCP-Detektor verwendet. Im Rahmen dieser Arbeit wurde ein neuer MCP-Detektor aufgebaut, in Betrieb genommen und kalibriert. Durch eine detaillierte Analyse der Schwachstellen des alten Detektorsystems konnte die Signalqualität verbessert, eine homogene Nachweiseffizienz erzielt, der Detektor kalibriert und dadurch eine zuverlässige Funktionsweise sichergestellt werden. Im zweiten Teil dieser Arbeit wurden anhand von Messdaten aus einer Teststrahlzeit eine Analyseroutine entwickelt und nach experimentellen Schwachstellen gesucht und Lösungen hierfür entwickelt

First detection and energy measurement of recoil ions following beta decay in a Penning trap with the WITCH experiment

The WITCH experiment (Weak Interaction Trap for CHarged particles) will search for exotic interactions by investigating the beta-neutrino angular correlation via the measurement of the recoil energy spectrum after beta decay. As a first step the recoil ions from the beta-minus decay of 124In stored in a Penning trap have been detected. The evidence for the detection of recoil ions is shown and the properties of the ion cloud that forms the radioactive source for the experiment in the Penning trap are presented.Comment: 9 pages, 6 figures (9 figure files), submitted to European Physical Journal

The WITCH experiment: Acquiring the first recoil ion spectrum

The standard model of the electroweak interaction describes beta-decay in the well-known V-A form. Nevertheless, the most general Hamiltonian of a beta-decay includes also other possible interaction types, e.g. scalar (S) and tensor (T) contributions, which are not fully ruled out yet experimentally. The WITCH experiment aims to study a possible admixture of these exotic interaction types in nuclear beta-decay by a precise measurement of the shape of the recoil ion energy spectrum. The experimental set-up couples a double Penning trap system and a retardation spectrometer. The set-up is installed in ISOLDE/CERN and was recently shown to be fully operational. The current status of the experiment is presented together with the data acquired during the 2006 campaign, showing the first recoil ion energy spectrum obtained. The data taking procedure and corresponding data acquisition system are described in more detail. Several further technical improvements are briefly reviewed.Comment: 11 pages, 6 figures, conference proceedings EMIS 2007 (http://emis2007.ganil.fr), published also in NIM B: doi:10.1016/j.nimb.2008.05.15

Space-charge effects in Penning ion traps

International audienceThe influence of space-charge on ion cyclotron resonances and magnetron eigenfrequency in a gas-filled Penning ion trap has been investigated. Off-line measurements with 39 K + using the cooling trap of the WITCH retardation spectrometer-based setup at ISOLDE / CERN were performed. Experimental ion cyclotron resonances were compared with ab initio Coulomb simulations and found to be in agreement. As an important systematic effect of the WITCH experiment , the magnetron eigenfrequency of the ion cloud was studied under increasing space-charge conditions. Finally , the helium buffer gas pressure in the Penning trap was determined by comparing experimental cooling rates with simulations

First β-ν correlation measurement from the recoil-energy spectrum of Penning trapped 35Ar ions

We demonstrate a novel method to search for physics beyond the standard model by determining the β-ν angular correlation from the recoil-ion energy distribution after β decay of ions stored in a Penning trap. This recoil-ion energy distribution is measured with a retardation spectrometer. The unique combination of the spectrometer with a Penning trap provides a number of advantages, e.g., a high recoil-ion count rate and low sensitivity to the initial position and velocity distribution of the ions and completely different sources of systematic errors compared to other state-of-the-art experiments. Results of a first measurement with the isotope 35Ar are presented. Although currently at limited precision, we show that a statistical precision of about 0.5% is achievable with this unique method, thereby opening up the possibility of contributing to state-of-the-art searches for exotic currents in weak interactions.status: publishe

A compact radio frequency quadrupole for ion bunching in the WITCH experiment

During the last several years the WITCH (Weak Interaction Trap for CHarged particles) experimental setup at ISOLDE has undergone various upgrades aiming at improvement of general performance. An essential innovation, a compact Radio Frequency Quadrupole (RFQ) ion cooler and buncher device, was designed and successfully commissioned as a part of the off-line tuning system of WITCH. The RFQ is coupled to the existing surface ionization ion source providing high intensity ion bunches (up to 10(7) ions per bunch) towards the pulsed drift tube and the Penning traps of WITCH. This achievement allows for loading and tuning of the Penning traps in the domain of space charge limits and grants off-line operation independently of the REX-ISOLDE ion source. The current upgrade allows for a more thorough and frequent testing with bunched stable ion beams of high intensities, which will be used for studying various systematic effects involved in experiments with radioactive ions.status: publishe

Simbuca, using a graphics card to simulate Coulomb interactions in a penning trap

In almost all cases, N-body simulations are limited by the computation time available. Coulomb interaction calculations scale with O(N(2)) with N the number of particles. Approximation methods exist already to reduce the computation time to O(NlogN) although calculating the interaction still dominates the total simulation time. We present Simbuca, a simulation package for thousands of ions moving in a Penning trap which will be applied for the WITCH experiment. Simbuca uses the output of the Cunbody-1 library, which calculates the gravitational interaction between entities on a graphics card, and adapts it for Coulomb calculations. Furthermore the program incorporates three realistic buffer gas models, the possibility of importing realistic electric and magnetic fieldmaps and different order integrators with adaptive step size and error control. The software is released under the GNU General Public License and free for use. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved

Search for a scalar component in the weak interaction

International audienceWeak interactions are described by the Standard Model which uses the basic assumption of a pure “V(ector)-A(xial vector)” character for the interaction. However, after more than half a century of model development and experimental testing of its fundamental ingredients, experimental limits for possible admixtures of scalar and/or tensor interactions are still as high as 7%. The WITCH project (Weak Interaction Trap for CHarged particles) at the isotope separator ISOLDE at CERN is trying to probe the structure of the weak interaction in specific low energy β–decays in order to look for possible scalar or tensor components or at least significantly improve the current experimental limits. This worldwide unique experimental setup consisting of a combination of two Penning ion traps and a retardation spectrometer allows to catch, trap and cool the radioactive nuclei provided by the ISOLDE separator, form a cooled and scattering-free radioactive source of β–decaying nuclei and let these nuclei decay at rest. The precise measurement of the shape of the energy spectrum of the recoiling nuclei, the shape of which is very sensitive to the character of the weak interaction, enables searching for a possible admixture of a scalar/tensor component in the dominant vector/axial vector mode. First online measurements with the isotope 35Ar were performed in 2011 and 2012. The current status of the experiment, the data analysis and results as well as extensive simulations will be presented and discussed

Space-charge effects in Penning ion traps

The influence of space-charge on ion cyclotron resonances and magnetron eigen frequency in a gas-filled Penning ion trap has been investigated. Off-line measurements with 39K using the cooling trap of the WITCH retardation spectrometer-based setup at ISOLDE/CERN were performed. Experimental ion cyclotron resonances were compared with ab initio Coulomb simulations and found to be in agreement. As an important systematic effect of the WITCH experiment,the magnetron eigen frequency of the ion cloud was studied under increasing space-charge conditions. Finally, the helium buffer gas pressure in the Penning trap was determined by comparing experimental cooling rates with simulations.publisher: Elsevier articletitle: Space-charge effects in Penning ion traps journaltitle: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment articlelink: http://dx.doi.org/10.1016/j.nima.2015.02.057 content_type: article copyright: Copyright © 2015 CERN for the benefit of the Authors. Published by Elsevier B.V.status: publishe

Computer controls for the WITCH experiment

The WITCH experiment is a medium-scale experimental set-up located at ISOLDE/CERN. It combines a double Penning trap system with,a retardation spectrometer for energy measurements of recoil ions from beta decay. For a correct operation of such a set-up a whole range of different devices is required. Along with the installation and optimization of the set-up a computer control system was developed to control these devices. The CS-Framework that is developed and maintained at GSI, was chosen as a basis for this control system as it is perfectly suited to handle the distributed nature of a control system.We report here on the required hardware for WITCH, along with the basis of this CS-Framework and the add-ons that were implemented for WITCH. (C) 2010 Elsevier B.V. All rights reserved