| 1. |
- Aartsen, M. G., et al.
(författare)
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Computational techniques for the analysis of small signals in high-statistics neutrino oscillation experiments
- 2020
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 977
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Tidskriftsartikel (refereegranskat)abstract
- The current and upcoming generation of Very Large Volume Neutrino Telescopes - collecting unprecedented quantities of neutrino events - can be used to explore subtle effects in oscillation physics, such as (but not restricted to) the neutrino mass ordering. The sensitivity of an experiment to these effects can be estimated from Monte Carlo simulations. With the high number of events that will be collected, there is a trade-off between the computational expense of running such simulations and the inherent statistical uncertainty in the determined values. In such a scenario, it becomes impractical to produce and use adequately-sized sets of simulated events with traditional methods, such as Monte Carlo weighting. In this work we present a staged approach to the generation of expected distributions of observables in order to overcome these challenges. By combining multiple integration and smoothing techniques which address limited statistics from simulation it arrives at reliable analysis results using modest computational resources.
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| 2. |
- Lei, Fuchuan, 1987, et al.
(författare)
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Power-efficient hyperparametric oscillation via bound states in the continuum
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023.
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Konferensbidrag (refereegranskat)abstract
- Optical hyperparametric oscillation (h-OPO) emerges in a driven Kerr cavity because of modulation instability. Two pump photons are converted into a pair of two correlated photons at new wavelengths. For many realistic applications, efficient operation of h-OPO is required, especially at high-power regime. Currently, the pump-to-signal conversion efficiency is fundamentally limited mainly by two factors: parasitic mode competition [1] and attainable cavity intrinsic Q (Qi) to coupling Q (Qc) ratio [2].
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| 3. |
- Rebolledo Salgado, Israel, 1992, et al.
(författare)
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Nonlinear Broadening of Electro-Optic Frequency Combs in All-Normal Dispersion Si 3 N 4 Waveguides
- 2021
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Ingår i: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021.
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Konferensbidrag (refereegranskat)abstract
- Dispersion-engineered silicon nitride waveguides are often used for broadening of frequency combs. Previous experiments have focused on anomalous dispersion waveguides pumped by femtosecond laser pulses, whereby coherent supercontinuum generation relies on soliton compression and dispersive wave emission (see e.g. [1] ). This regime of operation does not work well with high-repetition rate sources, such as microcombs or electro-optic (EO) combs, because the pulse duration is not sufficiently short to drive coherent broadening in anomalous dispersion media. Indeed, octave-spanning coherent broadening of high-repetition rate sources has been attained in anomalous dispersion silicon nitride waveguides, but this required using a pre-broadening stage in a normal-dispersion highly nonlinear fiber (HNLF) [2]. Implementing this stage in a silicon nitride waveguide is the topic we address in this contribution.
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| 4. |
- Spartà, R., et al.
(författare)
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Probing proton halo effects in the 8 B+ 64 Zn collision around the Coulomb barrier
- 2021
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 820
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Tidskriftsartikel (refereegranskat)abstract
- Proton halo effects in the 8B+64Zn reaction at an energy around 1.5 times the Coulomb barrier have been studied at HIE-ISOLDE CERN using, for the first time, the only existing postaccelerated 8B beam. This, together with the use of a high granularity and large solid angle detection system, allowed for a careful mapping of the elastic angular distribution, especially in the Coulomb-nuclear interference region. Contrary to what is observed for the one-neutron halo nucleus 11Be on the same target in a similar energy range, the analysis of the elastic scattering angular distribution shows only a modest suppression of the Coulomb-nuclear interference peak, with no remarkable enhancement of the total reaction cross-section. Inclusive angular and energy distributions of 7Be produced in direct reaction processes have also been measured. The comparison of these data with the results of theoretical calculations for the elastic and non-elastic breakup contributions indicate that both processes are important. Overall, the experimental data suggest a 8B collision dynamics at the barrier very different from the one of neutron halo nuclei, showing only modest effects of coupling to continuum. This behaviour can be interpreted as due to the presence of the additional Coulomb interactions halo-core and halo-target together with the presence of the centrifugal barrier felt by the valence proton of 8B.
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| 5. |
- Windelius, Olle, 1972, et al.
(författare)
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Photoelectron angular distributions in photodetachment from P
- 2021
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Ingår i: Physical Review A. - 2469-9926 .- 2469-9934. ; 103:3
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Tidskriftsartikel (refereegranskat)abstract
- The angular distributions of electrons ejected in laser photodetachment of the P- ion have been studied in the photon energy range of 0.95-3.28 eV using a photoelectron spectrometer designed to accommodate a source consisting of collinearly overlapping photon and negative ion beams. We observe the value of the asymmetry parameter beta starting at zero near the threshold, falling to almost -1 about 0.5 eV above the threshold and eventually rising to a positive value. The experimental data has been fitted to a simplified model of the Cooper-Zare formula which yields a qualitative understanding of the quantum interference between the outgoing s and d waves representing the free electron. The present results are also compared with previous results for other elements involving p-electron photodetachment.
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| 6. |
- Leimbach, David, 1992, et al.
(författare)
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Upgrades of the GANDALPH photodetachment detector towards the determination of the electron affinity of astatine
- 2020
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 463, s. 277-279
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 The Gothenburg ANion Detector for Affinity measurements by Laser PHotodetachment (GANDALPH)has recently been built for measurements of electron affinities (EA)of radioisotopes. A first measurement campaign is aimed towards the determination of the EA of astatine, the rarest naturally occurring element on earth. In this work we present several upgrades of GANDALPH which have been implemented in order to facilitate EA measurements of radioisotopes where only low intensity ion beams (<1 pA)can be produced.
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| 7. |
- Aalbers, J., et al.
(författare)
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A next-generation liquid xenon observatory for dark matter and neutrino physics
- 2023
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Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 50:1
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Forskningsöversikt (refereegranskat)abstract
- The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
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| 8. |
- Abbasi, R., et al.
(författare)
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A convolutional neural network based cascade reconstruction for the IceCube Neutrino Observatory
- 2021
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Ingår i: Journal of Instrumentation. - : Institute of Physics Publishing (IOPP). - 1748-0221. ; 16:7
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Tidskriftsartikel (refereegranskat)abstract
- Continued improvements on existing reconstruction methods are vital to the success of high-energy physics experiments, such as the IceCube Neutrino Observatory. In IceCube, further challenges arise as the detector is situated at the geographic South Pole where computational resources are limited. However, to perform real-time analyses and to issue alerts to telescopes around the world, powerful and fast reconstruction methods are desired. Deep neural networks can be extremely powerful, and their usage is computationally inexpensive once the networks are trained. These characteristics make a deep learning-based approach an excellent candidate for the application in IceCube. A reconstruction method based on convolutional architectures and hexagonally shaped kernels is presented. The presented method is robust towards systematic uncertainties in the simulation and has been tested on experimental data. In comparison to standard reconstruction methods in IceCube, it can improve upon the reconstruction accuracy, while reducing the time necessary to run the reconstruction by two to three orders of magnitude.
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| 9. |
- Ferri, Julien, 1990, et al.
(författare)
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Enhancement of laser-driven ion acceleration in non-periodic nanostructured targets
- 2020
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 86:1
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Tidskriftsartikel (refereegranskat)abstract
- Using particle-in-cell simulations, we demonstrate an improvement of the target-normal-sheath acceleration (TNSA) of protons in non-periodically nanostructured targets with micron-scale thickness. Compared to standard flat foils, an increase in the proton cutoff energy by up to a factor of two is observed in foils coated with nanocones or perforated with nanoholes. The latter nano-perforated foils yield the highest enhancement, which we show to be robust over a broad range of foil thicknesses and hole diameters. The improvement of TNSA performance results from more efficient hot-electron generation, caused by a more complex laser-electron interaction geometry and increased effective interaction area and duration. We show that TNSA is optimized for a nanohole distribution of relatively low areal density and that is not required to be periodic, thus relaxing the manufacturing constraints.
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| 10. |
- Hjort, Filip, 1991, et al.
(författare)
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Optical microprism cavities based on dislocation-free GaN
- 2020
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 117:23
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional growth of nanostructures can be used to reduce the threading dislocation density that degrades III-nitride laser performance. Here, nanowire-based hexagonal GaN microprisms with flat top and bottom c-facets are embedded between two dielectric distributed Bragg reflectors to create dislocation-free vertical optical cavities. The cavities are electron beam pumped, and the quality (Q) factor is deduced from the cavity-filtered yellow luminescence. The Q factor is similar to 500 for a 1000nm wide prism cavity and only similar to 60 for a 600nm wide cavity, showing the strong decrease in Q factor when diffraction losses become dominant. Measured Q factors are in good agreement with those obtained from quasi-3D finite element frequency-domain method and 3D beam propagation method simulations. Simulations further predict that a prism cavity with a 1000nm width will have a Q factor of around 2000 in the blue spectral regime, which would be the target regime for real devices. These results demonstrate the potential of GaN prisms as a scalable platform for realizing small footprint lasers with low threshold currents.
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