506 research outputs found
Design and experimental set-up of hydrogen based microgrid: characterization of components and control system development
In this study, the implementation of a hydrogen microgrid is investigated, considering the integration of H2 production, storage, and energy conversion to feed a typical end-user. A remote control system has been realized through LabVIEW software, allowing to monitor real-time all the devices and analyze their performances. The integrated system is composed of a PEM electrolyzer (325 W), a storage system based on metal hydrides (two tanks, 54 g of hydrogen each, 1.08 wt%) and an energy converter (PEM Fuel Cell stack, 200 W). A programmable electronic load was used to set a power demand throughout the year, simulating an end-user. Data collected from each component of the micro-grid were used to characterize the energetic performance of the devices, focusing on the H2 production via electrolyzer, charging cycles of the H2 storage system, and energy conversion efficiency of the FC stack. Finally, the global efficiency of the microgrid is computed. Even though the system is realized in laboratory scale, this circumstance will not invalidate the significance of the configuration due to modularity of all the technologies that can be easily scaled up to realistic scales
Light-Induced Charged and Trap States in Colloidal Nanocrystals Detected by Variable Pulse Rate Photoluminescence Spectroscopy
<p>Intensity instabilities are a common trademark of the photoluminescence of nanoemitters. This general behavior is commonly attributed to random fluctuations of free charges and activation of charge traps reducing the emission yield intermittently. However, the actual physical origin of this phenomenon is actively debated. Here we devise an experiment, variable pulse rate photoluminescence, to control the accumulation of charges and the activation of charge traps. The dynamics of these states is studied, with pulse repetition frequencies from the single-pulse to the megahertz regime, by monitoring photoluminescence spectrograms with picosecond temporal resolution. We find that both photocharging and charge trapping contribute to photoluminescence quenching, and both processes can be reversibly induced by light. Our spectroscopic technique demonstrates that charge accumulation and trap formation are strongly sensitive to the environment, showing different dynamics when nanocrystals are dispersed in solution or deposited as a film.</p>
Intrinsic time resolution of 3D-trench silicon pixels for charged particle detection
In the last years, high-resolution time tagging has emerged as the tool to
tackle the problem of high-track density in the detectors of the next
generation of experiments at particle colliders. Time resolutions below 50ps
and event average repetition rates of tens of MHz on sensor pixels having a
pitch of 50m are typical minimum requirements. This poses an important
scientific and technological challenge on the development of particle sensors
and processing electronics. The TIMESPOT initiative (which stands for TIME and
SPace real-time Operating Tracker) aims at the development of a full prototype
detection system suitable for the particle trackers of the next-to-come
particle physics experiments. This paper describes the results obtained on the
first batch of TIMESPOT silicon sensors, based on a novel 3D MEMS (micro
electro-mechanical systems) design. Following this approach, the performance of
other ongoing silicon sensor developments has been matched and overcome, while
using a technology which is known to be robust against radiation degradation. A
time resolution of the order of 20ps has been measured at room temperature
suggesting also possible improvements after further optimisations of the
front-end electronics processing stage.Comment: This version was accepted to be published on JINST on 21/07/202
f0(980) production in inelastic pp collisions at s = 5.02 TeV
The measurement of the production of f0(980) in inelastic pp collisions at sqrt(s) = 5.02 TeV is presented. This is the first reported measurement of inclusive f0(980) yield at LHC energies. The production is measured at midrapidity, |y| pi+pi- hadronic decay channel using the ALICE detector. The pT-differential yields are compared to those of pions, protons and Ï mesons as well as to predictions from the HERWIG 7.2 QCD-inspired Monte Carlo event generator and calculations from a coalescence model that uses the AMPT model as an input. The ratio of the pT-integrated yield of f0(980) relative to pions is compared to measurements in e+e- and pp collisions at lower energies and predictions from statistical hadronisation models and HERWIG 7.2. A mild collision energy dependence of the f0(980) to pion production is observed in pp collisions from SPS to LHC energies. All considered models underpredict the pT-integrated 2f0(980)/(pi+ + pi-) ratio. The prediction from the canonical statistical hadronisation model assuming a zero total strangeness content of f0(980) is consistent with the data within 1.9Ï and is the closest to the data. The results provide an essential reference for future measurements of the particle yield and nuclear modification in pâPb and PbâPb collisions, which have been proposed to be instrumental to probe the elusive nature and quark composition of the f0(980) scalar meson
Light (anti)nuclei production in Pb-Pb collisions at sNN=5.02Â TeV
The measurement of the production of deuterons, tritons and 3 He and their antiparticles in Pb-Pb collisions
at âs NN = 5.02 TeV is presented in this article. The measurements are carried out at midrapidity (|y| <
0.5) as a function of collision centrality using the ALICE detector. The pT -integrated yields, the coalescence
parameters and the ratios to protons and antiprotons are reported and compared with nucleosynthesis models. The
comparison of these results in different collision systems at different center-of-mass collision energies reveals a
suppression of nucleus production in small systems. In the Statistical Hadronisation Model framework, this can
be explained by a small correlation volume where the baryon number is conserved, as already shown in previous
fluctuation analyses. However, a different size of the correlation volume is required to describe the proton yields
in the same data sets. The coalescence model can describe this suppression by the fact that the wave functions
of the nuclei are large and the fireball size starts to become comparable and even much smaller than the actual
nucleus at low multiplicities
Inclusive and multiplicity dependent production of electrons from heavy-flavour hadron decays in pp and p-Pb collisions
Measurements of the production of electrons from heavy-flavour hadron decays in pp collisions at root s = 13 TeV at midrapidity with the ALICE detector are presented down to a transverse momentum (p(T)) of 0.2 GeV/c and up to p(T) = 35 GeV/c, which is the largest momentum range probed for inclusive electron measurements in ALICE. In p-Pb collisions, the production cross section and the nuclear modification factor of electrons from heavy-flavour hadron decays are measured in the p(T) range 0.5 < p(T) < 26 GeV/c at root s(NN) = 8.16 TeV. The nuclear modification factor is found to be consistent with unity within the statistical and systematic uncertainties. In both collision systems, first measurements of the yields of electrons from heavy-flavour hadron decays in different multiplicity intervals normalised to the multiplicity-integrated yield (self-normalised yield) at midrapidity are reported as a function of the self-normalised charged-particle multiplicity estimated at midrapidity. The self-normalised yields in pp and p-Pb collisions grow faster than linear with the self-normalised multiplicity. A strong p(T) dependence is observed in pp collisions, where the yield of high-p(T) electrons increases faster as a function of multiplicity than the one of low-p(T) electrons. The measurement in p-Pb collisions shows no p(T) dependence within uncertainties. The self-normalised yields in pp and p-Pb collisions are compared with measurements of other heavy-flavour, light-flavour, and strange particles, and with Monte Carlo simulations
Production of pions, kaons, and protons as a function of the relative transverse activity classifier in pp collisions at = 13 TeV
Abstract: The production of ϱ, K±, and ( p )p is measured in pp collisions at âs = 13 TeV
in different topological regions of the events. Particle transverse momentum (pT) spectra are
measured in the âtowardâ, âtransverseâ, and âawayâ angular regions defined with respect
to the direction of the leading particle in the event. While the toward and away regions
contain the fragmentation products of the near-side and away-side jets, respectively, the
transverse region is dominated by particles from the Underlying Event (UE). The relative
transverse activity classifier, RT = NT/ăNTă, is used to group events according to their UE
activity, where NT is the measured charged-particle multiplicity per event in the transverse
region and ăNTă is the mean value over all the analysed events. The first measurements
of identified particle pT spectra as a function of RT in the three topological regions are
reported. It is found that the yield of high transverse momentum particles relative to the
RT-integrated measurement decreases with increasing RT in both the toward and the away
regions, indicating that the softer UE dominates particle production as RT increases and
validating that RT can be used to control the magnitude of the UE. Conversely, the spectral
shapes in the transverse region harden significantly with increasing RT. This hardening
follows a mass ordering, being more significant for heavier particles. Finally, it is observed
that the pT-differential particle ratios (p + p )/(Ï+ + Ïâ) and (K+ + Kâ)/(Ï+ + Ïâ) in
the low UE limit (RT â 0) approach expectations from Monte Carlo generators such as
PYTHIA 8 with Monash 2013 tune and EPOS LHC, where the jet-fragmentation models
have been tuned to reproduce e+eâ results
Investigation of K+K- interactions via femtoscopy in Pb-Pb collisions at sNN =2.76 TeV at the CERN Large Hadron Collider
Femtoscopic correlations of nonidentical charged kaons (K+K-) are studied in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collision sNN=2.76 TeV by ALICE at the CERN Large Hadron Collider. One-dimensional K+K- correlation functions are analyzed in three centrality classes and eight intervals of particle-pair transverse momentum. The LednickĂœ and Luboshitz interaction model used in the K+K- analysis includes the final-state Coulomb interactions between kaons and the final-state interaction through a0(980) and f0(980) resonances. The mass of f0(980) and coupling were extracted from the fit to K+K- correlation functions using the femtoscopic technique. The measured mass and width of the f0(980) resonance are consistent with other published measurements. The height of the Ï(1020) meson peak present in the K+K- correlation function rapidly decreases with increasing source radius, qualitatively in agreement with an inverse volume dependence. A phenomenological fit to this trend suggests that the Ï(1020) meson yield is dominated by particles produced directly from the hadronization of the system. The small fraction subsequently produced by final-state interactions could not be precisely quantified with data presented in this paper and will be assessed in future work
Measurement of the Lifetime and Î Separation Energy of _{Î}^{3}H
The most precise measurements to date of the _{Î}^{3}H lifetime Ï and Î separation energy B_{Î} are obtained using the data sample of Pb-Pb collisions at sqrt[s_{NN}]=5.02ââTeV collected by ALICE at the LHC. The _{Î}^{3}H is reconstructed via its charged two-body mesonic decay channel (_{Î}^{3}Hâ^{3}He+Ï^{-} and the charge-conjugate process). The measured values Ï=[253±11(stat)±6(syst)]ââps and B_{Î}=[102±63(stat)±67(syst)]ââkeV are compatible with predictions from effective field theories and confirm that the _{Î}^{3}H structure is consistent with a weakly bound system
- âŠ