TY  - JOUR
A1  - Henriques, A.
A1  - Jurado, B.
A1  - Grieser, M.
A1  - Denis-Petit, D.
A1  - Chiron, T.
A1  - Gaudefroy, L.
A1  - Glorius, J.
A1  - Langer, Christoph
A1  - Litvinov, Yu. A.
A1  - Mathieu, L.
A1  - Meot, V.
A1  - Perez-Sanchez, R.
A1  - Pibernat, J.
A1  - Reifarth, R.
A1  - Roig, O.
A1  - Thomas, B. A.
A1  - Thomas, B. A.
A1  - Thomas, J. C.
A1  - Tsekhanovich, I.
T1  - Indirect measurements of neutron cross-secti at heavy-ion storage rings
JF  - Journal of Physics: Conference Series
N2  - Cross sections for neutron-induced reactions of short-lived nuclei are essential for nuclear astrophysics since these reactions in the stars are responsible for the production of most heavy elements in the universe. These reactions are also key in applied domains like energy production and medicine. Nevertheless, neutron-induced cross-section measurements can be extremely challenging or even impossible to perform due to the radioactivity of the targets involved. Indirect measurements through the surrogate-reaction method can help to overcome these difficulties.

The surrogate-reaction method relies on the use of an alternative reaction that will lead to the formation of the same excited nucleus as in the neutron-induced reaction of interest. The decay probabilities (for fission, neutron and gamma-ray emission) of the nucleus produced via the surrogate reaction allow one to constrain models and the prediction of the desired neutron cross sections.

We propose to perform surrogate reaction measurements in inverse kinematics at heavy-ion storage rings, in particular at the CRYRING@ESR of the GSI/FAIR facility. We present the conceptual idea of the most promising setup to measure for the first time simultaneously the fission, neutron and gamma-ray emission probabilities. The results of the first simulations considering the 238U(d,d') reaction are shown, as well as new technical developments that are being carried out towards this set-up.
Y1  - 2020
U6  - https://doi.org/10.1088/1742-6596/1668/1/012019
VL  - 1668
IS  - Art. 012019
PB  - IOP
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Fiedler, Thomas M.
A1  - Ladd, Mark E.
A1  - Clemens, Markus
A1  - Bitz, Andreas
T1  - Safety of subjects during radiofrequency exposure in ultra-high-field magnetic resonance imaging
JF  - IEEE Letters on Electromagnetic Compatibility Practice and Applications
N2  - Magnetic resonance imaging (MRI) is one of the most important medical imaging techniques. Since the introduction of MRI in the mid-1980s, there has been a continuous trend toward higher static magnetic fields to obtain i.a. a higher signal-to-noise ratio. The step toward ultra-high-field (UHF) MRI at 7 Tesla and higher, however, creates several challenges regarding the homogeneity of the spin excitation RF transmit field and the RF exposure of the subject. In UHF MRI systems, the wavelength of the RF field is in the range of the diameter of the human body, which can result in inhomogeneous spin excitation and local SAR hotspots. To optimize the homogeneity in a region of interest, UHF MRI systems use parallel transmit systems with multiple transmit antennas and time-dependent modulation of the RF signal in the individual transmit channels. Furthermore, SAR increases with increasing field strength, while the SAR limits remain unchanged. Two different approaches to generate the RF transmit field in UHF systems using antenna arrays close and remote to the body are investigated in this letter. Achievable imaging performance is evaluated compared to typical clinical RF transmit systems at lower field strength. The evaluation has been performed under consideration of RF exposure based on local SAR and tissue temperature. Furthermore, results for thermal dose as an alternative RF exposure metric are presented.
Y1  - 2020
SN  - 2637-6423
U6  - https://doi.org/10.1109/LEMCPA.2020.3029747
VL  - 2
IS  - 3
SP  - 1
EP  - 8
PB  - IEEE
CY  - New York, NY
ER  -