.
The AGATA Detector Library (ADL) was developed for the calculation of signals from highly segmented large volume high-purity germanium (HPGe) detectors. ADL basis sets comprise a huge amount of ...calculated position-dependent detector pulse shapes. A basis set is needed for Pulse Shape Analysis (PSA). By means of PSA the interaction position of a
-ray inside the active detector volume is determined. Theoretical concepts of the calculations are introduced and cover the relevant aspects of signal formation in HPGe. The approximations and the realization of the computer code with its input parameters are explained in detail. ADL is a versatile and modular computer code; new detectors can be implemented in this library. Measured position resolutions of the AGATA detectors based on ADL are discussed.
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•Comparison of three state-of-the art analysis platforms for amino acid analysis.•Detailed comparison of analytical figures of merit.•Guidance of the reader to the platform most ...valuable for his research question.
The analysis of amino acids has become a central task in many aspects. While amino acid analysis has traditionally mainly been carried out using either gas chromatography (GC) in combination with flame ionization detection or liquid chromatography (LC) with either post-column derivatization using ninhydrin or pre-column derivatization using o-phthalaldehyde, many of today’s analysis platforms are based on chromatography in combination with mass spectrometry (MS). While derivatization is mandatory for the GC-based analysis of amino acids, several LC platforms have emerged, particularly in the dawn of targeted metabolite profiling using hydrophilic interaction liquid chromatography (HILIC) coupled to MS, allowing the analysis of underivatized amino acids. Among the numerous analytical platforms available for amino acid analysis today, we here compare three prominent approaches, being GC–MS and LC–MS after amino acid derivatization using chloroformate and HILIC–MS of underivatized amino acids. We compare and discuss practical issues as well as performance characteristics, e.g., the use of 13C-labeled internal standards, of the different platforms and present data on their practical implementation in our laboratory. Finally, we compare the real-life applicability of all three platforms for a complex biological sample. While all three platforms are very-well suited for the analysis of complex biological samples they all show advantages and disadvantages for some analytes as discussed in detail in this manuscript.
The space charge distribution inside highly segmented large volume HPGe detectors determined from capacitance–voltage (CV) measurements is investigated. A computer code was developed to understand ...the impact of impurity concentrations on the resulting capacitances between core contact and outer contact for HPGe detectors biased at different high voltages. The code is intended as a tool for the reconstruction of the doping profile within irregularly shaped detector crystals. The results are validated by comparison with the exact solution of a true coaxial detector. Existing methods for space charge parameter extraction are briefly reviewed. The space charge reconstruction under cylindrical symmetry is derived. An extension of this scheme to higher dimensions for inhomogeneous space charge distributions is illustrated for a two-dimensional segmented coaxial detector.
MINOS is a new apparatus dedicated to in-beam nuclear structure experiments with low-intensity exotic beams in inverse kinematics at intermediate energies above 150MeV/nucleon. The device is composed ...of a thick liquid-hydrogen target coupled to a compact time projection chamber (TPC) serving as a vertex tracker. Either used for in-beam gamma spectroscopy of bound excited states or invariant-mass spectroscopy of unbound states, MINOS aims at improving the luminosity by a very significant factor compared to standard solid-target material experiments while improving experimental resolutions.
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The performance of the Pulse-Shape Analysis (PSA) in AGATA HPGe detectors was investigated and improved employing a
γ
-ray source measurement based on
e
+
e
-
annihilation radiation after decays of
...22
Na by
β
+
decay. The first interaction positions of the two 511keV
γ
rays were determined and the connecting line of these two positions was compared to the known source position as a measure for the PSA performance. The position resolution and its dependence on the PSA parameters were investigated by varying most relevant input quantities: the charge carrier mobility of the holes, the response of the employed measuring electronics especially the preamplifier rise time. The relative statistical weight of charge signals and transient signals was scrutinized. The optimal distance metric of the grid-search algorithm and its impact on the position resolution were determined.
Several experiments were conducted at the 10 MV Van-de-Graaff tandem accelerator at the Institute of Nuclear Physics, Cologne, to detect proton emission from the isomeric 6457-keV
10
+
state in
54
Ni
.... Excitation functions for two fusion–evaporation reactions were measured to maximise the population of the rare two-neutron evaporation channel from a
56
Ni
compound nucleus. The search for delayed proton emission was based on the
28
Si
(
28
Si
,
2
n
)
54
Ni
reaction at a beam energy of 70 MeV. For this reaction, a cross-section limit for the population of the
10
+
state in
54
Ni
and its proton-decay branch was determined to be
σ
<
22
nb.
.
A Compton camera based on a highly-segmented high-purity germanium (HPGe) detector and a double-sided silicon-strip detector (DSSD) was developed, tested, and put into operation; the origin of
γ
...radiation was determined successfully. The Compton camera is operated in two different modes. Coincidences from Compton-scattered
γ
-ray events between DSSD and HPGe detector allow for best angular resolution; while the high-efficiency mode takes advantage of the position sensitivity of the highly-segmented HPGe detector. In this mode the setup is sensitive to the whole
4
π
solid angle. The interaction-point positions in the 36-fold segmented large-volume HPGe detector are determined by pulse-shape analysis (PSA) of all HPGe detector signals. Imaging algorithms were developed for each mode and successfully implemented. The angular resolution sensitively depends on parameters such as geometry, selected multiplicity and interaction-point distances. Best results were obtained taking into account the crosstalk properties, the time alignment of the signals and the distance metric for the PSA for both operation modes. An angular resolution between
13
.
8
∘
and
19
.
1
∘
, depending on the minimal interaction-point distance for the high-efficiency mode at an energy of 1275 keV, was achieved. In the coincidence mode, an increased angular resolution of
4
.
6
∘
was determined for the same
γ
-ray energy.
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Lifetimes of excited states in
107
Tc,
109
Rh,
111
Rh, and
113
Rh were measured at GANIL using the Recoil-Distance Doppler Shift method. The neutron-rich nuclei were produced in fission reactions ...in inverse kinematics with a
238
U beam impinging on a
9
Be target. Fission fragments were identified event-by-event in the ray-tracing spectrometer VAMOS++ and correlated with prompt
γ
rays observed around the target position with the EXOGAM Ge detector array. Several lifetimes were obtained for states in the positive-parity yrast bands in the four nuclei and compared to triaxial particle-rotor calculations. The results clarify the configuration for the strongest positive-parity band in
107
Tc and suggest a gradual increase of triaxial deformation with atomic number
Z
, reaching almost maximum triaxiality for the neutron-rich Rh nuclei.
The structure of neutron-rich 96,98Sr nuclei was investigated by low-energy safe Coulomb excitation ofradioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. A rich set ...oftransitional and diagonal E2 matrix elements, including those for non-yrast structures, has been extractedfrom the differential Coulomb-excitation cross sections. The results support the scenario of a shape transition atN = 60, giving rise to the coexistence of a highly deformed prolate and a spherical configuration in 98Sr, andare compared to predictions from several theoretical calculations. The experimental data suggest a significantcontribution of the triaxal degree of freedom in the ground state of both isotopes. In addition, experimentalinformation on low-lying states in 98Rb has been obtained.
Neutron-rich {96,98}Sr isotopes have been investigated by safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility. Reduced transition probabilities and spectroscopic quadrupole ...moments have been extracted from the differential Coulomb excitation cross sections. These results allow, for the first time, the drawing of definite conclusions about the shape coexistence of highly deformed prolate and spherical configurations. In particular, a very small mixing between the coexisting states is observed, contrary to other mass regions where strong mixing is present. Experimental results have been compared to beyond-mean-field calculations using the Gogny D1S interaction in a five-dimensional collective Hamiltonian formalism, which reproduce the shape change at N=60.
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