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Bloch T.,TU Darmstadt | Bauer C.,TU Darmstadt | Leske J.,TU Darmstadt | Pietralla N.,TU Darmstadt | Van De Walle J.,Kernfysisch Versneller Instituut KVI
IPAC 2010 - 1st International Particle Accelerator Conference | Year: 2010

The REX-ISOLDE facility at CERN delivers a great variety of radioactive ion beams with energies up to 3.0 MeV/u and therefore allows nuclear structure physics experiments far from the valley of stability. A crucial point for the experimentalist is the knowledge of beam contaminations, either from the bunching and charge-breeding procedure (residual gas ions) or directly from the ion-production process (isobaric contaminants), whose sources are discussed as well as possible ways of elimination during the post-acceleration. Methods to analyse the beam composition in the relevant energy range are presented on the basis of two specific experiments using the MINIBALL detector array with an emphasis on the experimental challenges in Gamma-spectroscopy experiments and data analysis.

Jungmann K.,Kernfysisch Versneller Instituut KVI | Giri G.S.,Kernfysisch Versneller Instituut KVI | Versolato O.O.,Kernfysisch Versneller Instituut KVI
AIP Conference Proceedings | Year: 2012

In the singly charged Ra + ion the contributions of the weak interactions to the atomic level energies are some 50 times larger than in the Cs atom. We report the results of laser spectroscopy experiments on 209-214Ra + isotopes in preparation of a precision atomic parity violation experiment. Experimental input data is provided for testing the atomic theory, which is necessary for a competitive extraction of the Weinberg angle at low energies. © 2012 American Institute of Physics.

Van Dam H.T.,Technical University of Delft | Seifert S.,Technical University of Delft | Vinke R.,Kernfysisch Versneller Instituut KVI | Dendooven P.,Kernfysisch Versneller Instituut KVI | And 4 more authors.
IEEE Transactions on Nuclear Science | Year: 2010

The response of a silicon photomultiplier (SiPM) to optical signals is inherently nonproportional due to saturation, afterpulsing, and crosstalk. Existing models of the SiPM response do not account for all of these effects, and therefore, these models are not sufficiently accurate for many applications. In this work, a comprehensive model of the SiPM response is developed that is generally applicable to exponentially decaying light pulses and that can be simplified in the case of very short (e.g., laser) light pulses. The model accounts for the total number and the temporal distribution of the incident photons as well as for the relevant SiPM parameters, viz. the recovery time, afterpulsing, crosstalk, and their cross correlations. The model is shown to correspond well with measurements on a SiPM-based scintillation detector. Furthermore, it is shown to be in agreement with several cases for which the SiPM response is known a priori. Having thus validated the model, its use is demonstrated by predicting the response of the Hamamatsu multipixel photon counter (MPPC) S10362-33-050C SiPM to several different scintillators. © 2010 IEEE.

Seifert S.,Technical University of Delft | Van Dam H.T.,Technical University of Delft | Huizenga J.,Technical University of Delft | Vinke R.,Kernfysisch Versneller Instituut KVI | And 3 more authors.
Physics in Medicine and Biology | Year: 2012

Positron emission tomography detectors based on monolithic scintillation crystals exhibit good spatial and energy resolution, intrinsically provide depth-of-interaction information, have high γ-photon capture efficiency, and may reduce the manufacturing costs compared to pixelated crystal arrays. Here, we present the characterization of a detector consisting of a 18.0 mm×16.2mm×10.0 mm monolithic LaBr 3:5%Ce scintillator directly coupled to a 4×4 array of silicon photomultipliers. An energy resolution of 6.4% full-width-at-half-maximum (FWHM) was obtained. The point-spread-function (PSF) was determined for different regions of the detector. The full-width-at-half-maximum (FWHM) of the PSF was measured to be <1.5 mm at the center of the detector and <1.7 mm averaged over the entire crystal. Both values are not corrected for the 0.6 mm FWHM test beam diameter. Furthermore, the influence of edge effects was investigated. We found that near the edges of the detector the spatial resolution degrades to 2.2 mm (FWHM), and a bias in the position estimates, up to 1.5 mm, was observed. Moreover, the coincidence resolving time for two identical detectors in coincidence was measured to be as small as 198 ps FWHM. © 2012 Institute of Physics and Engineering in Medicine.

Nunez Portela M.,Kernfysisch Versneller Instituut KVI | van den Berg J.E.,Kernfysisch Versneller Instituut KVI | Bekker H.,Kernfysisch Versneller Instituut KVI | Boll O.,Kernfysisch Versneller Instituut KVI | And 13 more authors.
Hyperfine Interactions | Year: 2013

A single trapped Ra+ (Z = 88) ion provides a very promising route towards a most precise measurement of Atomic Parity Violation (APV), since APV effects grow faster than Z3. This experiment promises the best determination of the electroweak coupling constant at the lowest accessible energies. Such a measurement provides a sensitive test of the Standard Model in particle physics. At the present stage of the experiment, we focus on trapping and laser cooling stable Ba+ ions as a precursor for radioactive Ra+. Online laser spectroscopy of the isotopes 209-214Ra+ in a linear Paul trap has provided information on transition wavelengths, fine and hyperfine structures and excited state lifetimes as test of atomic structure calculations. Additionaly, a single trapped Ra+ ion could function as a very stable clock. © 2013 Springer Science+Business Media Dordrecht.

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