A rich set of differential cross section of the three-body
2
H(
d
,
dp
)
n
breakup reaction at 160 MeV deuteron beam energy has been measured over a large range of the available phase space. The ...experiment was performed at KVI in Groningen, the Netherlands, using the BINA detector. The cross-section data for the breakup reaction have been normalized to the simultaneously measured
2
H(
d
,
d
)
2
H elastic scattering cross section. The breakup cross sections obtained for 147 kinematically complete configurations near the quasi-free scattering kinematics are compared to the recent approximate calculations for the three-cluster breakup in deuteron–deuteron collisions. The cross sections for 294 kinematic configurations of the quasi-free scattering regime, for which no theoretical calculations exist, are also presented. Besides the three-body breakup, semi-inclusive energy distributions for the four-body
2
H(
d
,
pp
)
nn
breakup are reported.
The experimental data collected during the S515 experiment performed by the R
3
B collaboration at GSI/FAIR represent a great opportunity to investigate nucleon knockout reactions of exotic nuclei in ...the region of Sn using complete kinematics measurements. These cross sections can be used in the future to investigate the quenching in the knockout of the minority species (neutrons or protons) in nuclei far from stability. Some of the arguments put forward are the underestimation of the knockout of deeply bound nucleons, final state interactions or the role of short-range correlations (SRC). Recently, several works based on inclusive measurements have shown that these SRCs could reduce the single nucleon knockout cross sections by around 50%, depending on the neutron excess (N/Z) of the initial projectile. The S515 data can help us to go further in this investigation because it allows to correlate the knockout cross sections of one, two or more nucleons with the number of protons and neutrons emitted from the target and which can be detected by the CALIFA and NeuLAND detectors, respectively, and perform complete kinematical studies on the nature of the event (SRC, evaporation, emission of clusters, final-state interactions...). Here the results obtained for the charge distribution of reaction residues are presented, which is one of the first steps of the still on-going analysis.
The tetraneutron has attracted the attention of nuclear physicists during the past decades, but there is still no unambiguous confirmation of its existence or non-existence. A new experiment based on
...8
He(
p
, 2
p
)
7
H{
t
+
4
n
} reaction, with direct detection of the four neutrons, has been carried out at RIBF, which can hopefully help to draw a definite conclusion on the tetraneutron system.
A neutron spectrometer, the European Low-Energy Neutron Spectrometer (ELENS), has been constructed to study exotic nuclei in inverse-kinematics experiments. The spectrometer, which consists of ...plastic scintillator bars, can be operated in the neutron energy range of 100keV–10MeV. The neutron energy is determined using the time-of-flight technique, while the position of the neutron detection is deduced from the time-difference information from photomultipliers attached to both ends of each bar. A novel wrapping method has been developed for the plastic scintillators. The array has a larger than 25% detection efficiency for neutrons of approximately 500keV in kinetic energy and an angular resolution of less than 1°. Details of the design, construction and experimental tests of the spectrometer will be presented.
Systems composed of 3 nucleons are a subject of precise experimental studies for many years. At the first stage the investigations were mainly focused on elastic nucleon-deuteron scattering, slowly ...extending to systematic measurements of the deuteron breakup reaction. Intermediate energies, below the threshold for pion production, deserve special attention: it is the region where comparison with exact theoretical calculations is possible, while the sensitivity to various aspects of interaction, like subtle effects of the dynamics beyond the pairwise nucleon-nucleon force, is significant. Moreover, the Coulomb interaction and relativistic effects show their influence in the observables of the breakup reaction. All these effects vary with energy and appear with different strength in certain observables and phase space regions, what calls for systematic investigations of a possibly rich set of observables determined in a wide range of energies. The next step in complication of the system are studies of reactions involving 4 nucleons—more sensitive, as expected, to subtle dynamics beyond the pairwise interaction. A brief survey of recent and planned experiments in the 3- and 4-nucleon systems is given.
The investigation of light-ion reactions with exotic beams in inverse kinematics gives access to a comprehensive range of nuclear structure information in the region far off stability. The future ...FAIR facility at GSI will provide new opportunities to extend and advance these investigations. The present paper will focus on the results of the first feasibility experiment for the EXL project in which we used a stored
136Xe beam with
E = 350
MeV/nucleon interacting with an internal hydrogen gas-jet target at the ESR storage ring of GSI. In this experiment we made use of at least one element of every detector part of the future experimental setup. Selected results from this measurement will be presented.
The Super FRagment Separator (Super-FRS) at the FAIR facility will be the largest in-flight separator of heavy ions in the world. One of the essential steps in the separation procedure is to stop the ...unwanted ions with beam collimators. In one of the most common situations, the heavy ions are produced by a fission reaction of a primary 238U-beam (1.5 GeV u) hitting a 12C target (2.5 g cm2). In this situation, some of the produced ions are highly charged states of 238U. These ions can reach the collimators with energies of up to 1.3 GeV u and a power of up to 500 W. Under these conditions, a cooling system is required to prevent damage to the collimators and to the corresponding electronics. Due to the highly radioactive environment, both the collimators and the cooling system must be suitable for robot handling. Therefore, an active cooling system is undesirable because of the increased possibility of malfunctioning and other complications. By using thermal simulations (performed with NX9 of Siemens PLM), the possibility of passive cooling is explored. The validity of these simulations is tested by independent comparison with other simulation programs and by experimental verification. The experimental verification is still under analysis, but preliminary results indicate that the explored passive cooling option provides sufficient temperature reduction.
A new Machine Learning algorithm for shower-head identification in the NeuLAND neutron detector is presented. The new algorithm uses densely-connected Deep Neural Networks (DNNs) to properly classify ...events and clusters, which allows accurate reconstruction of the 4-momenta of the detected neutrons. As data-events recorded with NeuLAND vary quite a lot in size, and not all emitted neutrons always produce signals in the detector, careful pre- and post-processing of the data turned out to be required for letting the DNNs be successful in their classifications. However, after properly implementing these procedures, the new algorithm offers a better efficiency than previously-used algorithms in virtually all investigated scenarios. However, the newly-developed algorithm (as well as previous ones) suffers from systematic uncertainties. These uncertainties mainly arise from the physics lists used in the Geant4 simulations to train the DNNs. They are particularly large for the neutron energy range around 200 MeV and for NeuLAND configurations of few double-planes (slimmed down version of the detector). The accuracy improves with a larger number of double-planes. Furthermore, both model improvements and accurate benchmarks are needed for the currently used Geant4 physics lists to reduce the systematic uncertainties of the new algorithm for high-precision studies. Further improvement of the present DNN algorithm is also needed, especially for experiments that require high precision in the neutron scattering angle reconstruction. However, it seems unlikely that this improvement can be realized using only NeuLAND data.
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