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The homogeneous causal action principle on a compact domain of momentum space is introduced. The connection to causal fermion systems is worked out. Existence and compactness results are reviewed. The Euler-Lagrange equations are derived and analyzed under suitable regularity assumptions., Comment: 33 pages, LaTeX, 2 figures, smaller improvements (published version)

We measured the Coulomb dissociation of 16O into 4He and 12C within the FAIR Phase-0 program at GSI Helmholtzzentrum für Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section 16O(α,γ)12C, which is the time reversed reaction to 12C(α,γ)16O. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the R3B setup were necessary to cope with the high-intensity 16O beam. All tracking detectors were designed to let the unreacted 16O ions pass, while detecting the 12C and 4He.

International audience; The measurements of neutron capture cross sections of neutron-rich nuclei are challenging but essential for understanding nucleosynthesis and stellar evolution processes in the explosive burning scenario. In the quest of r-process abundances, according to the neutrino-driven-wind model, light neutron-rich unstable nuclei may play a significant role as seed nuclei that influence the abundance pattern. Hence, experimental data for neutron capture cross sections of neutron-rich nuclei are needed. Coulomb dissociation of radioactive ion beams at intermediate energy is a powerful indirect method for inferring capture cross section. As a test case for validation of the indirect method, the neutron capture cross section (n, γ) for C14 was inferred from the Coulomb dissociation of C15 at intermediate energy (600A MeV). A comparison between different theoretical approaches and experimental results for the reaction is discussed. We report for the first time experimental reaction cross sections of Na28(n,γ)Na29, Na29(n,γ)Na30, Mg32(n,γ)Mg33, and Al34(n,γ)Al35. The reaction cross sections were inferred indirectly through Coulomb dissociation of Na29,30, Mg33, and Al35 at incident projectile energies around 400–430 A MeV using the FRS-LAND setup at GSI, Darmstadt. The neutron capture cross sections were obtained from the photoabsorption cross sections with the aid of the detailed balance theorem. The reaction rates for the neutron-rich Na, Mg, Al nuclei at typical r-process temperatures were obtained from the measured (n,γ) capture cross sections. The measured neutron capture reaction rates of the neutron-rich nuclei, Na28, Na29, and Al34 are significantly lower than those predicted by the Hauser-Feshbach decay model. A similar trend was observed earlier for C17 and N19 but in the case of C14(n,γ)C15 the trend is opposite. The situation is more complicated when the ground state has a multi-particle-hole configuration. For Mg32, the measured cross section is about 40–90% higher than the Hauser-Feshbach prediction.

A discrepancy in the asymmetry dependence of spectroscopic factors extracted with different reaction probes calls into question whether the corresponding reaction models are properly understood. In this work, we present extracted spectroscopic factors from the Ar 46 , 34 ( p , d ) Ar 45 , 33 transfer reactions in inverse kinematics at a beam energy of 70 MeV/nucleon. The results are consistent with previous measurements of these reactions at a lower beam energy [Lee et al., Phys. Rev. Lett. 104, 112701 (2010)], indicating that the transfer reaction is a reliable probe for the nuclear structure of exotic nuclei across a wide energy range. Results from a large body of transfer reaction measurements, ( p , p N ) measurements, and theoretical nuclear structure studies make a compelling case for much weaker asymmetry dependence than what is observed with single-nucleon knockout reactions on beryllium or carbon targets.

Applied physics / A 127(8), 576 (2021). doi:10.1007/s00339-021-04713-4, Published by Springer, New York

To optimize the measurement range of thermal conductivity vacuum gauges, an expression for the sensitivity is required that takes into account all geometrical, material-specific, and operating parameters. Therefore, equations of the sensor output signal as a function of the pressure for the constant current and the constant temperature mode have been developed analytically. Based on these equations, the sensitivity of the vacuum gauge and its influencing parameters was investigated and discussed. For comparable conditions, the constant temperature operation shows a significantly higher sensitivity for high pressures, while the constant current operation shows higher sensitivity at low pressures. The sensitivity in both the constant current and the constant temperature mode depends on the ratio of the filament surface area and the parasitic thermal conductance. In addition, for the constant current operation, the sensitivity also depends on the current value and the temperature coefficient of the filament resistor. For the constant temperature operation, the sensitivity additionally depends on the distance of the filament and the reference plane. However, to extend the measurement range of a thermal conductivity vacuum gauge toward low pressures, a reduction of the parasitic thermal conductance is mandatory for both the constant current and the constant temperature mode.

The capture cross section of $^{209}\mathrm{Bi}(n,\ensuremath{\gamma})^{210g}\mathrm{Bi}$ was measured at different astrophysically relevant energies including thermal capture cross section (25 meV), resonance integral, and the Maxwellian averaged cross section at a thermal energy of $kT=30$ keV. The partial capture cross section $({\ensuremath{\sigma}}_{g})$ was determined using the activation technique and by measuring the $^{210}\mathrm{Po}$ activity. The newly developed and tested NICE detector setup was used to measure the $\ensuremath{\alpha}$ activity of the $^{210}\mathrm{Po}$. Using this setup the thermal and resonance integral cross sections were determined to be $16.2\phantom{\rule{0.28em}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.28em}{0ex}}0.97$ mb and $89.81\phantom{\rule{0.28em}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.28em}{0ex}}8.0$ mb, respectively. And the Maxwellian average cross section was measured to be $2.01\phantom{\rule{0.28em}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.28em}{0ex}}0.38$ mb.

International audience; Neutron-induced cross sections of short-lived nuclei are highly relevant in many domains such as fundamental nuclear physics, astrophysics and applications in nuclear technology. In particular, these cross sections are essential for understanding the synthesis of elements via the s- and r stellar processes. However, the measurement of such cross sections with current techniques is very difficult or even impossible, because of the difficulties to produce and handle the necessary amounts of radioactive nuclei. Reaching the nuclei of interest is only possible by inverting the reaction kinematics with radioactive beams. In this contribution we present a project for indirectly determining neutron cross sections via the surrogate-reaction method. This project is based on the measurement of transfer- or inelastic-scattering-induced decay probabilities in inverse kinematics at storage rings. The measured probabilities are then used to tune nuclear-reaction models that will provide much more accurate predictions of the desired neutron cross sections. We also discuss a very ambitious, long-term project to directly measure neutron cross sections in inverse kinematics. It consists in the combination of a radioactive beam facility, an ion storage ring and a spallation neutron source.

We provide a method for constructing (possibly non-trivial) measures on non-locally compact Polish subspaces of infinite-dimensional separable Banach spaces which, under suitable assumptions, are minimizers of causal variational principles in the non-locally compact setting. Moreover, for non-trivial minimizers the corresponding Euler-Lagrange equations are derived. The method is to exhaust the underlying Banach space by finite-dimensional subspaces and to prove existence of minimizers of the causal variational principle restricted to these finite-dimensional subsets of the Polish space under suitable assumptions on the Lagrangian. This gives rise to a corresponding sequence of minimizers. Restricting the resulting sequence to countably many compact subsets of the Polish space, by considering the resulting diagonal sequence we are able to construct a regular measure on the Borel algebra over the whole topological space. For continuous Lagrangians of bounded range it can be shown that, under suitable assumptions, the obtained measure is a (possibly non-trivial) minimizer under variations of compact support. Under additional assumptions, we prove that the constructed measure is a minimizer under variations of finite volume and solves the corresponding Euler-Lagrange equations. Afterwards, we extend our results to continuous Lagrangians vanishing in entropy. Finally, assuming that the obtained measure is locally finite, topological properties of spacetime are worked out and a connection to dimension theory is established., Comment: 46 pages

Nuclear instruments & methods in physics research / A 1014, 165701 (2021). doi:10.1016/j.nima.2021.165701, Published by North-Holland Publ. Co., Amsterdam

The interpretation of observations of cooling neutron star crusts in quasipersistent x-ray transients is affected by predictions of the strength of neutrino cooling via crust Urca processes. The strength of crust Urca neutrino cooling depends sensitively on the electron-capture and $\ensuremath{\beta}$-decay ground-state-to-ground-state transition strengths of neutron-rich rare isotopes. Nuclei with a mass number of $A=61$ are predicted to be among the most abundant in accreted crusts, and the last remaining experimentally undetermined ground-state-to-ground-state transition strength was the $\ensuremath{\beta}$ decay of $^{61}\mathrm{V}$. This Letter reports the first experimental determination of this transition strength, a ground-state branching of ${8.1}_{\ensuremath{-}3.1}^{+4.0}%$, corresponding to a log $ft$ value of ${5.5}_{\ensuremath{-}0.2}^{+0.2}$. This result was achieved through the measurement of the $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ rays using the total absorption spectrometer SuN and the measurement of the $\ensuremath{\beta}$-delayed neutron branch using the neutron long counter system NERO at the National Superconducting Cyclotron Laboratory at Michigan State University. This method helps to mitigate the impact of the pandemonium effect in extremely neutron-rich nuclei on experimental results. The result implies that $A=61$ nuclei do not provide the strongest cooling in accreted neutron star crusts as expected by some predictions, but that their cooling is still larger compared to most other mass numbers. Only nuclei with mass numbers 31, 33, and 55 are predicted to be cooling more strongly. However, the theoretical predictions for the transition strengths of these nuclei are not consistently accurate enough to draw conclusions on crust cooling. With the experimental approach developed in this work, all relevant transitions are within reach to be studied in the future.

Background: In the "island of inversion", ground states of neutron-rich $sd$-shell nuclei exhibit strong admixtures of intruder configurations from the $fp$ shell. The nucleus $^{30}$Mg, located at the boundary of the island of inversion, serves as a cornerstone to track the structural evolution as one approaches this region. Purpose: Spin-parity assignments for excited states in $^{30}$Mg, especially negative-parity levels, have yet to be established. In the present work, the nuclear structure of $^{30}$Mg was investigated by in-beam $\gamma$-ray spectroscopy mainly focusing on firm spin-parity determinations. Method: High-intensity rare-isotope beams of $^{31}$Mg, $^{32}$Mg, $^{34}$Si, and $^{35}$P bombarded a Be target to induce nucleon removal reactions populating states in $^{30}$Mg. $\gamma$ rays were detected by the state-of-the-art $\gamma$-ray tracking array GRETINA. For the direct one-neutron removal reaction, final-state exclusive cross sections and parallel momentum distributions were deduced. Multi-nucleon removal reactions from different projectiles were exploited to gain complementary information. Results: With the aid of the parallel momentum distributions, an updated level scheme with revised spin-parity assignments was constructed. Spectroscopic factors associated with each state were also deduced. Conclusions: Results were confronted with large-scale shell-model calculations using two different effective interactions, showing excellent agreement with the present level scheme. However, a marked difference in the spectroscopic factors indicates that the full delineation of the transition into the island of inversion remains a challenge for theoretical models.

The electron capture process was studied for Xe$^{54+}$ colliding with H$_2$ molecules at the internal gas target of the ESR storage ring at GSI, Darmstadt. Cross section values for electron capture into excited projectile states were deduced from the observed emission cross section of Lyman radiation, being emitted by the hydrogen-like ions subsequent to the capture of a target electron. The ion beam energy range was varied between 5.5 MeV/u and 30.9 MeV/u by applying the deceleration mode of the ESR. Thus, electron capture data was recorded at the intermediate and in particular the low collision energy regime, well below the beam energy necessary to produce bare xenon ions. The obtained data is found to be in reasonable qualitative agreement with theoretical approaches, while a commonly applied empirical formula significantly overestimates the experimental findings.

We measured the neutron capture-to-fission cross-section ratio (α ratio) and the capture cross section of $^{235}$U between 0.2 and 200 eV at the n_TOF facility at CERN. The simultaneous measurement of neutron-induced capture and fission rates was performed by means of the n_TOF BaF$_{2}$ Total Absorption Calorimeter (TAC), used for detection of γ rays, in combination with a set of micromegas detectors used as fission tagging detectors. The energy dependence of the capture cross section was obtained with help of the $^{6}$Li(n,t) standard reaction determining the n_TOF neutron fluence; the well-known integral of the $^{235}$U(n,f) cross section between 7.8 and 11 eV was then used for its absolute normalization. The α ratio, obtained with slightly higher statistical fluctuations, was determined directly, without need for any reference cross section. To perform the analysis of this measurement we developed a new methodology to correct the experimentally observed effect that the probabilities of detecting a fission reaction in the TAC and the micromegas detectors are not independent. The results of this work have been used in a new evaluation of $^{235}$U performed within the scope of the Collaborative International Evaluated Library Organisation (CIELO) Project, and are consistent with the ENDF/B-VIII.0 and JEFF-3.3 capture cross sections below 4 eV and above 100 eV. However, the measured capture cross section is on average 10% larger between 4 and 100 eV.

The neutron activation method is well-suited to investigate neutron-capture cross sections relevant for the main s-process component. Neutrons can be produced via the 7Li(p,n) reaction with proton energies of 1912 keV at e.g. Van de Graaff accelerators, which results in a quasi-Maxwellian spectrum of neutrons corresponding to a temperature of kBT = 25 keV. However, the weak s-process takes place in massive stars at temperatures between 25 and 90 keV. Simulations using the PINO code [2] suggest that a Maxwellian spectrum for higher energies, e.g. kBT = 90 keV, can be approximated by a linear combination of different neutron spectra. To validate the PINO code at proton energies Ep ≠ 1912 keV, neutron time-of-flight measurements were carried out at the PTB Ion Accelerator Facility (PIAF) at the Physikalisch-Technische Bundesanstalt in Braunschweig, Germany.

The chloride migration coefficient of concrete describes the resistance of concrete against chloride ingress. This important material variable can be determined with the rapid chloride migration test (RCM). During the test, chloride ions penetrate concrete by means of an applied electrical field. If the concrete has already been exposed to chlorides before the test starts, the test set up has to be adapted to achieve reliable results. Due to repeated exposure to the same salt (e.g. NaCl), there is no direct possibility to distinguish the chloride ions from the test procedure and the exposure before this, within the initial test procedure. Therefore, the RCM-test setup has been adapted by replacing NaCl through NaBr in the same molar amount. Consequently, this adapted test setup is called the rapid bromide migration test (RBM). The indicator silver nitrate AgNO3 forms sparingly soluble silver salts (AgCl, AgBr) in the presence of halogen ions (e.g. Cl-, Br-), which form a white precipitate in areas with Cl- or Br- ions. The penetration depths are measured at two split cylinder halves. In case the RBM-specimen has previously been exposed to NaCl, an analyzation technique has to be available for the two elements Cl and Br to enable a differentiation. As the white precipitate areas - a result of the formation of AgCl and AgBr - have a quite similar visual appearance, a differentiation cannot be achieved and other analytical techniques have to be considered. With laser-induced breakdown spectroscopy (LIBS), it is possible to determine the depth-dependent ion quantity (wt.-% of Cl or wt.-% of Br). In this study, it is shown by test results that it is possible to exchange NaCl by NaBr in the RCM test, since the penetration behavior of both ions (Cl-, Br-) is very similar in the migration test.

A novel silicon field emission source is presented, which is fabricated by saw dicing and TMAH-etching. Samples with different tip densities were investigated. Due to the fabrication process a higher tip density leads to a lower tip height. Very similar characteristics were observed for all different geometries. Emission currents of 10 $\mu\mathrm{A}$ are obtained at electrical fields of 6 - 8 $\mathrm{V}/\mu \mathrm{m}$ . The changes in the characteristics after 10 h at a regulated current of 10 $\mu\mathrm{m}\mathrm{A}$ and a pressure of 10–5 mbar were investigated. The observed shift in necessary field reduces with the number of tips and is lower in p-type compared to n-type samples.

We prove the existence of minimizers of causal variational principles on second countable, locally compact Hausdorff spaces. Moreover, the corresponding Euler-Lagrange equations are derived. The method is to first prove the existence of minimizers of the causal variational principle restricted to compact subsets for a lower semi-continuous Lagrangian. Exhausting the underlying topological space by compact subsets and rescaling the corresponding minimizers, we obtain a sequence which converges vaguely to a regular Borel measure of possibly infinite total volume. It is shown that, for continuous Lagrangians of compact range, this measure solves the Euler-Lagrange equations. Furthermore, we prove that the constructed measure is a minimizer under variations of compact support. Under additional assumptions, it is proven that this measure is a minimizer under variations of finite volume. We finally extend our results to continuous Lagrangians decaying in entropy., Comment: 31 pages, LaTeX, small improvements (published version supplemented by appendix)

Luminosity is a measure of the colliding frequency between beam and target and it is a crucial parameter for the measurement of absolute values, such as reaction cross sections. In this paper, we make use of experimental data from the ESR storage ring to demonstrate that the luminosity can be precisely determined by modelling the measured Rutherford scattering distribution. The obtained results are in good agreement with an independent measurement based on the x-ray normalization method. Our new method provides an alternative way to precisely measure the luminosity in low-energy stored-beam configurations. This can be of great value in particular in dedicated low-energy storage rings where established methods are difficult or impossible to apply., 8 pages, 5 figures

A new detector setup (NICE-detector) based on an organic plastic scintillator is presented. It will be used during experiments measuring neutron-induced reactions with a charged particle in the exit channel. The proposed design was tested at the Goethe University Frankfurt. One of the test cases was the capture cross-section of 209Bi at different astrophysically important energies, including thermal capture cross-section and resonance integral. This research presents the performance of the detector setup, as well as preliminary results for the calculated cross-sections. The preliminary results demonstrate that the newly developed NICE-detector can be used to determine capture cross-sections with sufficient accuracy, and might be adopted in the future as an alternative for charged particle measurements in different nuclear and astrophysical applications.

Objectives: To analyse the implementation, applicability and accuracy of the pretest probability calculation provided by NICE clinical guideline 95 for decision making about imaging in patients with chest pain of recent onset. Methods: The definitions for pretest probability calculation in the original Duke clinical score and the NICE guideline were compared. We also calculated the agreement and disagreement in pretest probability and the resulting imaging and management groups based on individual patient data from the Collaborative Meta-Analysis of Cardiac CT (CoMe-CCT). Results: 4,673 individual patient data from the CoMe-CCT Consortium were analysed. Major differences in definitions in the Duke clinical score and NICE guideline were found for the predictors age and number of risk factors. Pretest probability calculation using guideline criteria was only possible for 30.8 % (1,439/4,673) of patients despite availability of all required data due to ambiguity in guideline definitions for risk factors and age groups. Agreement regarding patient management groups was found in only 70 % (366/523) of patients in whom pretest probability calculation was possible according to both models. Conclusions: Our results suggest that pretest probability calculation for clinical decision making about cardiac imaging as implemented in the NICE clinical guideline for patients has relevant limitations. Key Points: • Duke clinical score is not implemented correctly in NICE guideline 95. • Pretest probability assessment in NICE guideline 95 is impossible for most patients. • Improved clinical decision making requires accurate pretest probability calculation. • These refinements are essential for appropriate use of cardiac CT.

We report on a method to stabilize the transmitted electronflux in a field-emission electronsource using an external regulation circuit. The electron source was realized with an array of silicon (Si) nanowhiskers on the top of elongated pillar structures, amica spacer, and an extraction grid made of Si. As for most applications, the emitted electron current from the cathode is not as crucial as the transmitted electron flux through the extraction grid toward the anode. We investigated a method which allows the regulation directly by the emitted electron flux and not merely on the cathode current. By using this method, we were able to stabilize the emitted electron flux of our electron source down to values below1%. Simultaneously, it was shown that there is the possibility to stabilize the influencing value in the real applicationaswell. The effectiveness of thismethod was demonstrated successfullywith an X-ray source setup. The measured X-ray photon count rate was stabilized to a standard deviation of 0.30% at a pressure of $1\times 10^{-7}$ mbar. Even in harsh environment of $2\times 10^{-5}$ mbar, a stabilization of the X-ray photon count rate down to a value of 0.63% was achieved.

A 63 years old male with a history of arterial hypertension presented with a current onset of chest pain and discrete headaches accompanied with dizziness. His blood pressure, 210/110 mmHg, had worsened and showed a reversed circadian rhythm with an average of 150/90 mmHg during night time. A CT angiography of the aorta demonstrated a type B dissection involving the right renal artery causing reduced perfusion of the right kidney. Subsequent invasive aortic angiography showed a continuously moving aortic dissection flap resulting in a dynamic stenosis proven by varying pressure gradients of between 5 and 35 mmHg. Stent placement of the renal artery ostium kept the vessel open and fixed the reno-aortic dissection flap in order to prevent it from progressing into the right kidney. Follow-up examinations revealed improved blood pressure control allowing for physiologic drop of blood pressure during night-time.

8 pags., 3 figs., We measured the Coulomb dissociation of 16O into 4He and 12C at the R3B setup in a first campaign within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The goal was to improve the accuracy of the experimental data for the 12C(α,γ)16O fusion reaction and to reach lower center-ofmass energies than measured so far. The experiment required beam intensities of 109 16O ions per second at an energy of 500 MeV/nucleon. The rare case of Coulomb breakup into 12C and 4He posed another challenge: The magnetic rigidities of the particles are so close because of the same mass-to-charge-number ratio A/Z = 2 for 16O, 12C and 4He. Hence, radical changes of the R3B setup were necessary. All detectors had slits to allow the passage of the unreacted 16O ions, while 4He and 12C would hit the detectors’ active areas depending on the scattering angle and their relative energies. We developed and built detectors based on organic scintillators to track and identify the reaction products with sufficient precision., This project was carried out within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. This project was supported by the Bundesministerium für Bildung und Forschung (BMBF) (05P19RFFN1, 05P15RFFN1, 05P15RDFN1), HGS-HIRE, HIC for FAIR and the GSI-TU Darmstadt cooperation agreement. I. Gašparić and R. Popočovski have been supported by the Croatian Science Foundation under projects no. 1257 and 7194.

The ^{23}Al(p,γ)^{24}Si reaction is among the most important reactions driving the energy generation in type-I x-ray bursts. However, the present reaction-rate uncertainty limits constraints on neutron star properties that can be achieved with burst model-observation comparisons. Here, we present a novel technique for constraining this important reaction by combining the GRETINA array with the neutron detector LENDA coupled to the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The ^{23}Al(d,n) reaction was used to populate the astrophysically important states in ^{24}Si. This enables a measurement in complete kinematics for extracting all relevant inputs necessary to calculate the reaction rate. For the first time, a predicted close-lying doublet of a 2_{2}^{+} and (4_{1}^{+},0_{2}^{+}) state in ^{24}Si was disentangled, finally resolving conflicting results from two previous measurements. Moreover, it was possible to extract spectroscopic factors using GRETINA and LENDA simultaneously. This new technique may be used to constrain other important reaction rates for various astrophysical scenarios.

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 682841 “ASTRUm”). This work is supported by the Helmholtz International Center for FAIR (HIC for FAIR), by the Bundesministerium fur Bildung und Forschung (BMBF) (05P15RFFAA, 05P15RGFAA), by the Science and Technology Facilities Council (STFC) UK (ST/L005824/1, ST/M001652/1, ST/M006085), by the Helmholtz-CAS Joint Research Group (HCJRG-108), and by the Helmholtz-OCPC Postdoctoral Program (GSI08). C. L. W. acknowledges support by the European Research Council (Grant Agreement ERC-2015-StG No. 677497 “DoRES”). S. D. gratefully acknowledges the support provided by the Alexander von Humboldt Foundation and the Jordanian Scientific Research Support Fund under Grant No. Bas/2/4/2014. S. Yu. T. acknowledges the support by the DAAD through Mendeleev Grant, SPbU(28999675). C. L. and J. G. thank the ExtreMe Matter Institute EMMI at GSI, Darmstadt, and JINA-CEE (NSF Grant No. PHY-1430152) for support in the framework of the EMMI/JINA-CEE Workshop “NARRS” during which this work was discussed.

7 pags., 4 figs., 2 tabs. -- Open Access funded by Creative Commons Atribution Licence 4.0, The quasi-free scattering reactions C(p,2p) and C(p,pn) have been studied in inverse kinematics at beam energies of 300–400 MeV/u at the RB-LAND setup. The outgoing proton-proton and proton-neutron pairs were detected in coincidence with the reaction fragments in kinematically complete measurements. The efficiency to detect these pairs has been obtained from GEANT4 simulations which were tested using the C(p,2p) and C(p,pn) reactions. Experimental cross sections and momentum distributions have been obtained and compared to DWIA calculations based on eikonal theory. The new results reported here are combined with previously published cross sections for quasi-free scattering from oxygen and nitrogen isotopes and together they enable a systematic study of the reduction of single-particle strength compared to predictions of the shell model over a wide neutron-to-proton asymmetry range. The combined reduction factors show a weak or no dependence on isospin asymmetry, in contrast to the strong dependency reported in nucleon-removal reactions induced by nuclear targets at lower energies. However, the reduction factors for (p,2p) are found to be 'significantly smaller than for (p,pn) reactions for all investigated nuclei., This work was supported by the German Federal Ministry of Education and Research (BMBF projects 05P2015RDFN1 and 05P15WOFNA), through the GSI-TU Darmstadt cooperation agreement, by the State of Hesse through the LOEWE center HIC for FAIR, and the Helmholtz-Gemeinschaft through the graduate school HGS-HIRe. This work was supported by the European Union by means of the European Commission within its Seventh Framework Program (FP7) via ENSAR (Contract No. 262010), and the Spanish CICYT research grants FPA2012-32443, FPA2015-64969-07387, and FPA2015-69640-C2-1-P. This work has supported by the Swedish Research Council under contract number 621-2011-5324. C.A.B. acknowledges support from the U.S. NSF grant No. 1415656 and the U.S. DOE grant No. DE-FG02-08ER41533. Supported by the Portuguese FCT under the project PTDC/FIS/ 103902/2008.

Silicon field emitter arrays (FEAs) with different tip sizes and quantities were fabricated by saw dicing and anisotropic wet chemical etching by tetramethylammonium hydroxide. The tip is formed by the different etching rates of the crystal facets leading to a sharp pyramid based on {103} planes on the top and a hexadecagon based on {331} and {221} planes on the bottom. Electrical measurements at 10−5 mbar up to 10 μA show good reproducibility for FEAs with the same process parameters and higher uniformity and stability with an increasing number of tips. Constant current measurements at the same conditions and 10 μA show a mean electric field increase of about 0.06(3) V/(μm h) for p-type FEAs with a tip quantity of 3600. The shift increases with lower tip quantity and is higher for n-type FEAs compared to p-type. The degradation during the constant current measurement of n-type samples is found to be partly reversible by heating to 200 °C during emission. In contrast, heating of p-type FEAs induced further degradation instead of a regeneration effect.

Physics letters / B 753, 204 - 210(2016). doi:10.1016/j.physletb.2015.11.082, Published by North-Holland Publ., Amsterdam

Transradial coronary angiography (TRC) can be performed applying only one catheter fitting into the right and left coronary ostia (R/LCO). In this bicentric study (n = 2953), we analyzed the ostial performance of the Tiger_II_catheter widely used in TRC. Compared to Judkins catheters, the Tiger_II is frequently associated with ostial instability within the LCO but fits better into the RCO-irrespective of tube size. Judkins catheters generally need more peri-procedural contrast and radiation exposure. TRC may be started using a 5F_Tiger_II on the right side in order to be switched to 5F Judkins in case of propable LCO instability.

A compact vacuum-sealed field emission electron gun with an operation voltage below 5 kV is presented. With a 150 nm thick pyrolytic carbon membrane, a transmission of 40% at 5 kV is obtained. For more than 2500 h of continuous operation at an emission current of 100 nA, no significant increase ( < 50 V) and almost no degradation were found. From this measurement, a lifetime of more than 10 000 h at continuous operation with approximately a linear increase of the extraction voltage from about 545 V to about 730 V is predicted. This electron source enables application of field emitter arrays in poor vacuum or even ambient pressure.

The components for a silicon chip electron source were fabricated by laser micromachining using pulsed laser ablation and wet chemical cleaning and etching dips. The field emission electron source consists of a silicon field emission cathode with 4 × 4 conical shaped emitters with a height of 250 μm and a tip radius of about 50 nm, a 50 μm thick laser-structured mica spacer, and a silicon grid electrode with a grid periodicity of 200 μm and a bar width of 50 μm. These three components are combined to a single chip with the size of 14 × 10 mm2 and the thickness of 1 mm to form the electron source. Several of these devices were characterized in ultrahigh vacuum. Onset voltages of about 165 V and cathode currents of about 15 μA for voltages lower than 350 V were observed. Operating the electron source with an anode voltage of 500 V and an extraction grid voltage of 300 V yielded a cathode current of 4.5 μA ± 8.9%, an anode current of 4.0 μA ± 9.6%, and a corresponding grid transmittance of 89%. Regulating the anode current by the extraction grid voltage, an extremely stable anode current of 5.0 μA ± 0.017% was observed. A long-term measurement over 120 h was performed, and no significant degradation or failure was observed.The components for a silicon chip electron source were fabricated by laser micromachining using pulsed laser ablation and wet chemical cleaning and etching dips. The field emission electron source consists of a silicon field emission cathode with 4 × 4 conical shaped emitters with a height of 250 μm and a tip radius of about 50 nm, a 50 μm thick laser-structured mica spacer, and a silicon grid electrode with a grid periodicity of 200 μm and a bar width of 50 μm. These three components are combined to a single chip with the size of 14 × 10 mm2 and the thickness of 1 mm to form the electron source. Several of these devices were characterized in ultrahigh vacuum. Onset voltages of about 165 V and cathode currents of about 15 μA for voltages lower than 350 V were observed. Operating the electron source with an anode voltage of 500 V and an extraction grid voltage of 300 V yielded a cathode current of 4.5 μA ± 8.9%, an anode current of 4.0 μA ± 9.6%, and a corresponding grid transmittance of 89%. Regulating th...

The neutron-unbound isotope Be-13 has been studied in several experiments using different reactions, different projectile energies, and different experimental setups. There is, however, no real consensus in the interpretation of the data, in particular concerning the structure of the low-lying excited states. Gathering new experimental information, which may reveal the Be-13 structure, is a challenge, particularly in light of its bridging role between Be-12, where the N = 8 neutron shell breaks down, and the Borromean halo nucleus Be-14. The purpose of the present study is to investigate the role of bound excited states in the reaction product Be-12 after proton knockout from B-14, by measuring coincidences between Be-12, neutrons, and gamma rays originating from de-excitation of states fed by neutron decay of Be-13. The Be-13 isotopes were produced in proton knockout from a 400 MeV/nucleon B-14 beam impinging on a CH2 target. The Be-12-n relative-energy spectrum d sigma/dE(fn) was obtained from coincidences between Be-12(g.s.) and a neutron, and also as threefold coincidences by adding gamma rays, from the de-excitation of excited states in Be-12. Neutron decay from the first 5/2(+) state in Be-13 to the 2(+) state in Be-12 at 2.11 MeV is confirmed. An energy independence of the proton-knockout mechanism is found from a comparison with data taken with a 35 MeV/nucleon B-14 beam. A low-lying p-wave resonance in Be-13(1/2(-)) is confirmed by comparing proton- and neutron-knockout data from B-14 and Be-14.

We have investigated the properties of single n- and p-type black silicon (b-Si) pillars with a height of 20 μ m under strong electric field and halogen lamp or laser illumination. For both type of b-Si pillar structures, I-V measurements revealed strong activation effects, which consisted in sudden current increases during the first up/down voltage sweeps. The maximum reproducible emission current from a single n-type b-Si pillar structure was about 15 μ A. A pronounced saturation region at 240 nA was observed for a single p-type b-Si pillar. The current fluctuation over time showed a standard deviation of 28% and 2.5% for n- and p-type single b-Si pillar structures, respectively. Optical switching under halogen lamp illumination resulted in at least 3 times higher saturation currents and showed a linear dependence of the FE current on the laser power.