Trap-integrated fluorescence detection based on silicon photomultipliers in a cryogenic Penning trap

We present a fluorescence-detection system for laser-cooled 9Be+ ions based on silicon photomultipliers (SiPM) operated at 4 K and integrated into our cryogenic 1.9 T multi-Penning-trap system. Our approach enables fluorescence detection in a hermetically-sealed cryogenic Penning-trap chamber with limited optical access, where state-of-the-art detection using a telescope and photomultipliers at room temperature would be extremely difficult. We characterize the properties of the SiPM in a cryocooler at 4 K, where we measure a dark count rate below 1/s and a detection efficiency of 2.5(3) %. We further discuss the design of our cryogenic fluorescence-detection trap, and analyze the performance of our detection system by fluorescence spectroscopy of 9Be+ ion clouds during several runs of our experiment.Comment: 12 pages, 11 figure

A device for simultaneous spin analysis of ultracold neutrons

© 2015, SIF, Springer-Verlag Berlin Heidelberg. We report on the design and first tests of a device allowing for measurement of ultracold neutrons polarisation by means of the simultaneous analysis of the two spin components. The device was developed in the framework of the neutron electric dipole moment experiment at the Paul Scherrer Institute. Individual parts and the entire newly built system have been characterised with ultracold neutrons. The gain in statistical sensitivity obtained with the simultaneous spin analyser is (18.2± 6.1)% relative to the former sequential analyser under nominal running conditions.status: publishe

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

Search for a scalar component in the weak interaction

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 beta–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 beta–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.status: publishe

Superconducting Solenoid System with Adjustable Shielding Factor for Precision Measurements of the Properties of the Antiproton

status: publishe

Active compensation of magnetic field distortions based on vector spherical harmonics field description

An analytic solution to the magnetostatic inverse problem in the framework of vector spherical harmonic basis functions is presented. This formalism is used for the design of a spherical magnetic field compensation system and its performance is compared with an already existing rectangular coil system. The proposed set of spherical coils with 15 degrees of freedom achieves a shielding factor of 1000 or better in a large part of the volume enclosed by the coils for a dipolar type external perturbation.status: publishe

Search for a scalar component in the weak interaction

Weak 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 $\beta$–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 $\beta$–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 $^{35}$Ar 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

Superconducting Solenoid System with Adjustable Shielding Factor for Precision Measurements of the Properties of the Antiproton

A superconducting self-shielding three-solenoid system with an adjustable shielding factor is developed, implemented, and characterized using a single antiproton in a Penning trap. With the tuned system, we suppress external magnetic field disturbances by up to a factor of 225 ± 15, allowing antiproton-to-proton charge-to-mass ratio comparisons with fourfold reduced frequency fluctuations and antiproton magnetic moment determinations with tenfold reduced uncertainty

Constraints on the Coupling between Axionlike Dark Matter and Photons Using an Antiproton Superconducting Tuned Detection Circuit in a Cryogenic Penning Trap

We constrain the coupling between axionlike particles (ALPs) and photons, measured with the superconducting resonant detection circuit of a cryogenic Penning trap. By searching the noise spectrum of our fixed-frequency resonant circuit for peaks caused by dark matter ALPs converting into photons in the strong magnetic field of the Penning-trap magnet, we are able to constrain the coupling of ALPs with masses around $2.7906-2.7914\,\textrm{neV/c}^2$ to $g_{a\gamma}< 1 \times 10^{-11}\,\textrm{GeV}^{-1}$. This is more than one order of magnitude lower than the best laboratory haloscope and approximately 5 times lower than the CERN axion solar telescope (CAST), setting limits in a mass and coupling range which is not constrained by astrophysical observations. Our approach can be extended to many other Penning-trap experiments and has the potential to provide broad limits in the low ALP mass range.Comment: 7 pages, 3 figure