arXiv subjects

P. Wagenknecht

Publications and source records attributed to P. Wagenknecht.

4 recordsLinked to original sources

arXiv2024

New isomeric transition in $^{36}$Mg: Bridging the N=20 and N=28 islands of inversion

We observed a new isomeric gamma transition at 168 keV in $^{36}$Mg, with a half-life of T$_{1/2}$=[130-500]$(\pm40)(^{+800}_{-20})_{sys}$ ns. We propose that the observed transition de-excites a new 0$^+$ isomeric state and populates the previously known first 2$^+$ state. The existence of this isomer is consistent with the predictions of the large-scale shell model calculations of $^{36}$Mg using the sdpf-u-mix interaction. The observed excitation energy of the second 0$^+$ state is caused by the small energy separation between two prolate-deformed configurations where the intruder configuration corresponds to two neutron excitations from the {\it sd} to the {\it pf} shell. Within this interpretation, $^{36}$Mg becomes the crossing point between nuclei in which ground state deformed/superdeformed configurations are caused by the dominance of N=20 intruders ($^{32,34}$Mg) and nuclei where deformed configurations are associated with N=28 intruders ($^{38}$Mg and beyond). We found the lack of three-body monopole corrections in other effective interactions results in a predominance of N=20 intruder configurations past $^{38}$Mg incompatible with our observation. We conclude that $^{36}$Mg bridges the N=20 and N=28 islands of inversion, forming the so-called Big Island of Deformation.

nucl-ex↗

arXiv2022

Strategies for Beam-Induced Background Reduction at Muon Colliders

Future collider detectors at muon colliders will be bombarded by Beam-Induced Backgrounds (BIB) due to the in-flight muon decays from the beam line. These backgrounds can inhibit the ability of the detector and subsequent data analysis to successfully reconstruct collision products. We explore methods for geometrically reducing these effects for use in the readout, triggering, and data analysis of future experiments. Studies are performed for a collision energy of 1.5~TeV, and a detector with a tungsten nozzle designed to block the majority of the BIB. In this context, detector strategies are explored to further reduce the BIB, with a focus on the innermost layers of the tracker where its density is highest. In addition, a conceptual design of a calorimeter built to reject BIB is presented.

physics.ins-det↗

arXiv2021

High-accuracy liquid-sample $β$-NMR setup at ISOLDE

Recently there has been an increased interest to apply the sensitive $β$-decay asymmetry detected nuclear magnetic resonance ($β$-NMR) technique to biological studies. A liquid-sample $β$-NMR setup was build at ISOLDE to allow such investigations and to use the resolution gain of liquid-state NMR in nuclear physics. As part of this setup a magnetic field locking system, a set of printed circuit board shimming coils, a sample exchange system, a set of compact $β$-detectors and a custom experimental vacuum chamber were developed. The main magnetic field was stabilized down to the ppm level by the locking system while allowing the direct determination of the absolute magnetic field. The homogeneity of the magnetic field was improved to $\leq$~5~ppm over the sample volume by the shimming coils. Time spent on changing samples was reduced by a factor of five by the liquid sample exchange system. During experiments it was possible to continuously observe the liquid sample thanks to the custom chamber and compact $β$-detectors. The absolute field determination allows for a novel way to reference $β$-NMR measurements, removing the need for time consuming reference measurements. The improved accuracy and resolution resulting from these innovations allows the study of the distribution of nuclear magnetization and (bio)chemicals using high-accuracy liquid-sample $β$-NMR.

physics.ins-det↗

arXiv2020

Magnetic moments of short-lived nuclei with part-per-million accuracy: Towards novel applications of $β$-detected NMR in physics, chemistry and biology

We determine for the first time the magnetic dipole moment of a short-lived nucleus with part-per-million (ppm) accuracy. To achieve this two orders of magnitude improvement over previous studies, we implement a number of innovations into our $β$-detected Nuclear Magnetic Resonance ($β$-NMR) setup at ISOLDE/CERN. Using liquid samples as hosts we obtain narrow, sub-kHz linewidth, resonances, while a simultaneous in-situ $^1$H NMR measurement allows us to calibrate and stabilize the magnetic field to ppm precision, thus eliminating the need for additional $β$-NMR reference measurements. Furthermore, we use ab initio calculations of NMR shielding constants to improve the accuracy of the reference magnetic moment, thus removing a large systematic error. We demonstrate the potential of this combined approach with the 1.1 s half-life radioactive nucleus $^{26}$Na, which is relevant for biochemical studies. Our technique can be readily extended to other isotopic chains, providing accurate magnetic moments for many short-lived nuclei. Furthermore, we discuss how our approach can open the path towards a wide range of applications of the ultra-sensitive $β$-NMR in physics, chemistry, and biology.

physics.chem-ph↗