[en] Some ten per cent of the world’s electricity is generated by nuclear power plants (NPPs). However, the contribution of nuclear energy for the specific peaceful application of the generation of electric power in the developing world continues to still be very modest. Rather, it is limited to only a few technologically advanced countries, albeit that this is increasing. This situation can be partly explained by the high capital costs associated with funding a nuclear power programme and the limited technology options for many developing countries. Driven by the needs of industrialised States and economies of scale (which do not favour small and medium reactors), the nuclear technology development path taken since the late 1960s has tended to focus on the deployment of reactor designs of increasing size, leading to designs today with power levels of up to 1700 MW(e).⁴ However, access to civil nuclear power should not be the sole prerogative of developed countries: it should also be available to developing countries.

[en] The reason why there is no primordial antimatter in the Universe remains a mystery. Measurements with antimatter [1][2] show full compatibility with its matter counterparts at high precision and that the antimatter feels Earth's gravitational attraction similarly to matter [3] at low precision. Antihydrogen (Hbar) is produced by trapping antiprotons and positrons in neighboring wells in a Penning-Malmberg trap and slowing mixing then. An Ioffe-Pritchard octupole magnetic trap superposed to the Penning trap allows the trapping of the produced neutral Hbars with energy below 500 mK [4]. Since trapped antiprotons and positrons are needed to create Hbars, a bias magnetic field of ~1 T is used in the trap region. This high magnetic field adds some systematic uncertainties in comparing the two-photon 1s-2s transition in H and Hbar since accurate measurements with H [5] are performed in a very low magnetic field environment. The precision of the comparison can be improved by trapping hydrogen in the same Hbar trap [6][7][8] and repeating the exact measurements with both counterparts, avoiding many systematic uncertainties such as this magnetic field effect, AC Stark shift from the same laser and enhancement cavity operation [9]. However, the strong bias magnetic field still affects the transition's lineshape and center. It is possible to ramp down the bias magnetic field and perform the 1s-2s spectroscopy with Hbar's since we can always detect the annihilation of the ionized atoms efficiently. Nevertheless, repeating the exact measurement in a near-zero bias with H is not straightforward since we can not detect the annihilation. If we keep the bias magnetic field, it is possible to recapture a fraction of the ionized H during the spectroscopy [10] by using a weak Penning trap potential, but for a near-zero magnetic field, recapturing the protons can not be accomplished. Here, we suggest using a hybrid Penning-Linear-Paul trap, using a segmented electrode in the Penning-Malmberg trap to radially confine the ions to perform high precision 1s-2s spectroscopy in H in a near-zero field trap. We will discuss the stability of the recaptured particles in a Linear-Paul trap with a weak magnetic field along the axis, the effect of the electric field on the lifetime of the H/Hbar, lineshape of the transition, the effect of a superposed octupole field to the RF trap, patch potentials, and possible magnetic fields measurements at low fields. [1] - Borchert et al, Nature 601, 53-57 (2022). [2] - Ahmadi, M. et al., Nature557, 71-75 (2018) [3] - Anderson, E.K. et al., Nature 621, 716-722 (2023) [4] - Andresen, G. B. et al, Nature 468, 673-676 (2010) [5] - Parthey, C. G. et al., Phys. Rev. Lett.107, 203001 (2011) [6] - Azevedo, L.O.A. et al, Commun Phys 6, 112 (2023) [7] - S A Jones, New J. Phys. 24 023016 (2022) [8] - W. A. Bertsche et al 2022 J. Phys.: Conf. Ser. 2244 012080 [9] - ALPHA Collaboration, Nature Physics, Accepted - To be published [10] - Cesar, C. L., J. Phys. B49, 074001 (2016)

[en] The influence of hydrogen absorption on T_c and M_s of the Gd₅Ge₂Si₂H_x alloys, with 0.1≤x≤2.5 was studied by thermomagnetic analysis from 2 to 370 K. The M(T) curves show the first order magnetic transition at 260 K only for the sample with x=0.1. All the samples presented the second-order magnetic transition between 296 (x=0.1) and 212 K (x=2.5). For the sample with x≥1.2 is also observed a new antiferromagnetic transition at ∼45 K. The M(H) curves revealed that the M_s tends to increase with the hydrogen amount into the alloy

No abstract available

[en] In this paper, a new experiment is presented to measure the 1S-2S transition of positronium, the bound state of an electron and a positron. The goal is to improve the current accuracy by a factor of 5 to reach a precision of the order of 0.6 ppb, to check recent QED calculations. This accuracy is challenging, but it seems well within reach in view of the technological advances that have occurred during the last two decades. We will present the details of the experimental setup, the advances in the production of positronium, the developments of the laser system, and as well our new experimental technique for the detection of Ps in the 2S state. (author)

[en] This work describes preliminary experiments that will bring subsidies to analyze the capability to implement a system able to capture radiological images with new sensor system, comprised by FOs scanning process and I-CCD camera. These experiments have the main objective to analyze the optical response from FOs bundle, with several typos of scintillators associated with them, when it is submitted to medical x-rays exposition. (author)

[en] We have studied the velocity distribution of chromium atoms released from a solid neon matrix at cryogenic temperatures via Doppler spectroscopy. The Ne matrix is grown by directing a small flux of gas onto a cold substrate, while Cr atoms are simultaneously implanted by laser ablation, with the resultant plume directed toward the growing matrix. The atoms are then released by a heat pulse. We have observed neutral Cr atoms at temperatures around 13 K with densities close to 10¹² cm^-3. The released atoms have a large initial drift velocity, explained by simple kinetic theory arguments, due to the light species' drag force. The scheme could be adapted to produce cryogenic beams of atoms, molecules, and possibly ions, for collisional studies and spectroscopy. However, our main motivation was the construction of a hydrogen trap, and here we discuss the prospects and problems of using this technique for this purpose

[en] We propose a usage of microwave radiation in a magnetic trap for improving the cooling and trapping of cold antihydrogen atoms which are initially produced in high magnetic moment states. Inducing transitions toward lower magnetic moments near the turning points of the atom in the trap, followed by spontaneous emission, should enhance the number of trappable atoms. We present results of simulations based on a typical experimental condition of the antihydrogen experiments at CERN. This technique should also be applicable to other trapped high magnetic moment Rydberg atoms.

[en] When treating problems of vector diffraction in electromagnetic theory, the evaluation of the integral involving Bessel and associated Legendre functions is necessary. Here we present the analytical result for this integral that will make numerical quadrature techniques or localized approximations unnecessary. The solution is presented using the properties of the Bessel and associated Legendre functions. (letter to the editor)

[en] We describe the generation and properties of a cryogenic beam of ⁷Li₂ dimers from sublimation of a neon matrix where lithium atoms have been implanted via laser ablation of solid precursors of metallic lithium or lithium hydride (LiH). Different sublimation regimes lead to pulsed molecular beams with different temperatures, densities and forward velocities. With laser absorption spectroscopy these parameters were measured using the molecular ⁷Li₂ (R) transitions A¹Σ_u⁺(v^′=4,J^′=J^′′+1) ←X ¹Σ_g⁺(v^′′=0,J^′′=0,1,3). In a typical regime, sublimating a matrix at 16 K, translational temperatures of 6–8 K with a drift velocity of 130 m s⁻¹ in a free expanding pulsed beam with molecular density of 10⁹ cm⁻³, averaged along the laser axis, were observed. Rotational temperatures around 5–7 K were obtained. In recent experiments we were able to monitor the atomic Li signal—in the D2 line—concomitantly with the molecular signal in order to compare them as a function of the number of ablation pulses. Based on the data and a simple model, we discuss the possibility that a fraction of these molecules are being formed in the matrix, by mating atoms from different ablation pulses, which would open up the way to formation of other more interesting and difficult molecules to be studied at low temperatures. Such a source of cryogenic molecules have possible applications encompassing fundamental physics tests, quantum information studies, cold collisions, chemistry, and trapping. (paper)