Papers by Sebastian Chmel
Physical Review C
High-spin states in 123 Xe were populated in the 80 Se(48 Ca, 5n) 123 Xe reaction at a beam energ... more High-spin states in 123 Xe were populated in the 80 Se(48 Ca, 5n) 123 Xe reaction at a beam energy of 207 MeV. γ-ray coincidence events were recorded with the Gammasphere spectrometer. Four new high-spin bands have been discovered in this nucleus. The bands are compared with those calculated within the framework of cranked Nilsson-Strutinsky and cranked Nilsson-Strutinsky-Bogoliubov models. It is concluded that the configurations of the bands involve two-proton excitations across the Z = 50 as well as excitation of neutrons across the N = 82 shell gaps resulting in a large deformation, ε 2 ≈ 0.30 and γ ≈ 5 • .
Verhandlungen der Deutschen Physikalischen Gesellschaft, 2012
2012 15th International Conference on Information Fusion, 2012
The localization and tracking of radioactive sources in public facilities like airports or statio... more The localization and tracking of radioactive sources in public facilities like airports or stations is a problem of highest security relevance. The accumulation and the severity of terrorist attacks during the past decade give reason to the assumption that future attacks could also involve radioactive material packaged with conventional explosives. The only way to avoid such kind of attacks is to localize and arrest the person carrying the material to its destination. But since radiation is not perceivable by human beings, the security guards are largely dependent on technical decision support to perform this task. We consider a security assistance system comprising three gamma scintillation detectors that are distributed along a corridor wall to check passing people for radioactive material. Furthermore, the system consists of a set of tracking sensors simultaneously providing the positions of all persons during their walk through the corridor. In this paper we propose techniques t...
EPJ Web of Conferences, 2021
Measurement equipment for the detection and identification of radioactive and nuclear (RN) materi... more Measurement equipment for the detection and identification of radioactive and nuclear (RN) material has a wide application area. The main application aspects are monitoring, search, and identification. A common goal is to gain reliable measurement results. In the past, the only way to assess the performance of a measuring device was to rely on the data given by the manufacturer of the device itself. Reliable test results from an independent third party are more than welcome. These tests can be performed against consensus standards in order to have reproducible test results, independent of the testing location and the performing laboratory. Fraunhofer INT has conceived and built a test environment to perform dynamic and static test measurements using neutron and gamma sources. Tests can be performed in accordance with the IEC and ANSI standards as well as the ITRAP+10 test procedures. This includes qualification tests of truck portal monitors with the dynamic test system. Generally, ...
Physical Review C, 2020
An experiment involving a heavy-ion induced fusion-evaporation reaction was carried out where hig... more An experiment involving a heavy-ion induced fusion-evaporation reaction was carried out where high-spin states of 123 Xe were populated in the 80 Se(48 Ca, 5n) 123 Xe reaction at 207 MeV beam energy. Gamma-ray coincidence events were recorded with the Gammmasphere Ge detector array. The previously known level scheme was confirmed and enhanced with the addition of five new band structures and several inter-band transitions. Cranked Nilsson-Strutinsky (CNS) calculations were performed and compared with the experimental results in order to assign configurations to the bands.
The European Physical Journal A, 2002
High-spin states in 142 Gd have been populated by means of the 99 Ru(48 Ti, 2p3n) reaction at 240... more High-spin states in 142 Gd have been populated by means of the 99 Ru(48 Ti, 2p3n) reaction at 240 MeV and investigated with the γ-spectrometer EUROBALL III and the charged-particle detector array ISIS. The features of four dipole bands have been determined and compared with tilted-axis cranking model calculations indicating that they are magnetic rotational bands. A transition from regular to irregular bands has been found approaching N = 82 demonstrating that this is a general phenomenon in nuclei near a double-shell closure.
Nuclear Structure, 2001
The principles of the Level Mixing Spectroscopy technique are explained. A possible area of appli... more The principles of the Level Mixing Spectroscopy technique are explained. A possible area of application is the neutron-deficient Pb region around A ~ 200.
To prevent the misuse of nuclear or radioactive material for malicious acts we investigated highl... more To prevent the misuse of nuclear or radioactive material for malicious acts we investigated highly sensitive passive detection systems for gamma and neutron radiation. The aim is to detect such material as early as possible with high reliability excluding false alarms caused by natural radioactivity (like in potash fertilizer) or by patients which have undergone a nuclear medical therapy respectively examination. Fixed monitors can be employed for the detection of such materials during transport. They may be covertly installed in advertising pillars or other objects commonly found in public. In a more static situation a general overview is gained by scanning of buildings or objects with a gamma camera. Here the measured spatial gamma intensity is converted into colors and then superimposed on the optical picture of the situation in order to get a visual overview. Besides gamma detectors we investigated neutron detectors also. Nuclear material can be detected by neutron emissions fro...
Nuclear Structure Physics, 2001
Communications in Computer and Information Science, 2012
The localization and tracking of radioactive sources in public facilities like airports or statio... more The localization and tracking of radioactive sources in public facilities like airports or stations is a problem of highest security relevance. The accumulation and the severity of terrorist attacks during the past decade give reason to the assumption that future attacks could also involve radioactive material packaged with conventional explosives. The only way to avoid such kind of attacks is to localize and arrest the person carrying the material to its destination. But since radiation is not perceivable by human beings, the security guards are largely dependent on technical decision support to perform this task. We consider a security assistance system comprising three gamma scintillation detectors that are distributed along a corridor wall to check passing people for radioactive material. Furthermore, the system consists of a set of tracking sensors simultaneously providing the positions of all persons during their walk through the corridor. In this paper we propose techniques to estimate the assignment of radioactive detections to person tracks. These techniques provide a measure for each person that reflects the probability that the person is a radioactive source carrier. The problem of source localization is thus reduced to a matching problem between person tracks and sequences of count rates.
Physics Letters B, 2007
The spectroscopic quadrupole moments of the 11 − and 12 + isomers in 192,194 Pb, described by the... more The spectroscopic quadrupole moments of the 11 − and 12 + isomers in 192,194 Pb, described by the 3s −2 1/2 1h 9/2 1i 13/2 intruder two-proton and 1i 2 13/2 two-quasineutron configurations, respectively, have been investigated by the method of time-differential observation of the γ-ray perturbed angular distribution. The derived values are |Q s |(12 + , 192 Pb) = 0.32(4) eb, |Q s |(11 − , 192 Pb) = 2.9(3) eb and |Q s |(11 − , 194 Pb) = 3.6(4) eb. The 8 + 2304 keV and 9 − 2514 keV states in 192 Pb have been identified as isomers, with half-lives of 3.9(3) and 3.3(3) ns, respectively. The experimental spectroscopic quadrupole moments for the 11 − and 12 + isomers in neutron deficient Pb nuclei have been described in the frame of the pairing plus quadrupole model. The intrinsic quadrupole moments and deformation of the 11 − isomers are compared with the predictions of mean-field and interacting boson models.
Physical Review C, 2007
Tilt angles, deformation parameters, angular momenta, and reduced magnetic dipole and electric qu... more Tilt angles, deformation parameters, angular momenta, and reduced magnetic dipole and electric quadrupole transition probabilities are calculated within the framework of the tilted-axis cranking model for shears bands in the neutron-deficient Pb isotopes 193 Pb to 202 Pb. The self-consistently calculated quadrupole-deformation parameters for the various configurations lie around ε 2 = −0.1, and the triaxiality is small. The tilt angle, i.e., the angle between the angular momentum and the nuclear symmetry axis, remains almost constant within each band, showing only a small increase toward higher angular momenta. The angular momentum increases mainly due to the shears effect, which is a step-by-step alignment of high-j proton and neutron orbitals into the direction of the total angular momentum. Calculated and experimental M1 transition rates are in good agreement. They decrease with increasing spin within the bands as expected for the shears effect. The calculated B(E2) values show only a weak spin dependence. However, the experimental B(E2) values have large errors, and more accurate data are needed to decide between the present model and a recently suggested geometrical approach.
The European Physical Journal A, 2004
Lifetimes have been measured for dipole bands in 142 Gd using DSAM. The deduced B(M 1) and B(E2) ... more Lifetimes have been measured for dipole bands in 142 Gd using DSAM. The deduced B(M 1) and B(E2) values as well as B(M 1)/B(E2) ratios are compared with calculations in the framework of the TAC (Tilted Axis Cranking) and SPAC (Shears mechanism with Principal Axis Cranking) models. The dipole bands DB1 to DB4 can be interpreted as magnetic rotational bands.
In the context of the possible threat of proliferation of nuclear material by groups of terrorist... more In the context of the possible threat of proliferation of nuclear material by groups of terrorist and non-state actors reliable detection techniques of such material are of great importance at points of interest such as airports, harbors, railway stations, and border crossing points. The opportunity to detect nuclear material is given at border stations in particular because vehicles and pedestrians potentially carrying such material are forced to drive or walk slowly in lines, thus providing well-defined measuring conditions. Gamma and neutron detectors with a high efficiency are required for this task. As consortium leader of the current TACIS (Technical Assistance to the Commonwealth of Independent States) project "Ukrainian Border Security" of the European Union our institute is involved in setting up modern stationary portal monitor systems at selected Ukrainian border stations in order to provide adequate detection techniques for the prevention of illicit trafficking...
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Papers by Sebastian Chmel