Machine learning entails a broad range of techniques that have been widely used in Science and Engineering since decades. High-energy physics has also profited from the power of these tools for ...advanced analysis of colliders data. It is only up until recently that Machine Learning has started to be applied successfully in the domain of Accelerator Physics, which is testified by intense efforts deployed in this domain by several laboratories worldwide. This is also the case of CERN, where recently focused efforts have been devoted to the application of Machine Learning techniques to beam dynamics studies at the Large Hadron Collider (LHC). This implies a wide spectrum of applications from beam measurements and machine performance optimisation to analysis of numerical data from tracking simulations of non-linear beam dynamics. In this paper, the LHC-related applications that are currently pursued are presented and discussed in detail, paying also attention to future developments.
Planar channeling in bent crystals has been observed in LHC with multi-TeV proton beam in 2015. Two crystals, mounted on novel high-accuracy goniometers (one in the horizontal and one in the vertical ...plane), are integrated in the LHC collimation system, for studying the feasibility of the crystal-based collimation scheme. Using this experimental setup, tests with fully-stripped lead ion beams at both 450 Z and 6500 Z GeV were carried during dedicated LHC beam time. Planar channeling was observed for the first time with lead ions at these unprecedented energies surpassing by more than 1 order of magnitude the previous state-of-the-art for lead heavy ions and providing an important experimental basis for future applications of bent crystals in beam manipulations. The set of measurements performed to confirm this observation, as the local loss reduction in presence of channeling and the evidence of a deflected beam downstream of the crystal, are presented.
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•The microchannels emulsifier is able to form a rather stable water–oil emulsion.•WiDE resulted stable after 2 h running into the high pressure common rail system.•WiDE emulsion was ...successfully used in an optical diesel engine.•WiDE implied a reduction in PM and NOx compared to that resulting from diesel oil.•The 2D chemiluminescence technique highlights a reduction in soot formation.
The paper reports the results of an experimental investigation carried out on a prototype optically accessible compression ignition engine fueled with water in diesel emulsion (WiDE) and Diesel only. The effect of WiDE on combustion process evolution and exhaust emissions was investigated through standard engine benchmark and optical diagnostics. 2D chemiluminescent emission measurements centered at 690 nm were carried out during the whole combustion process to discriminate the soot emission from other excited chemical species. The emulsion was produced through a prototype designed microchannels emulsifier that can also work inline. The water concentration was 9.1%v with a small amount (0.2%v) of nonionic surfactant (SPAN80) used to stabilize the emulsion. Tests were performed comparing combustion and exhaust emissions of the reference commercial diesel fuel to the WiDE. For any investigated fuel and operating point, engine tests were carried out changing the injection interval to achieve the same chemical energy as the reference diesel (935 J/str). Compared to Diesel, the WiDE induced an increase in ignition time, enhancing the air/fuel mixing with a simultaneous reduction in both PM and NOx. The digital imaging and 2D chemiluminescence techniques highlighted a reduction in soot formation without significant changes on the soot oxidation rate. The results suggest the use of WiDE as a reliable method to improve NOx-soot trade-off of CI engines.
The use of alternative fuels, as biodiesel and ethanol, for light duty CI engines to approach the target of ultra low NOx and PM emissions without fuel economy penalty has been widely investigated. ...Recently, it is growing the interest in the butanol as a viable alternative either single or blended with conventional based fuels both to cut the demand for fossil fuel and to reduce emissions of particulate matter without significantly increasing in NOx.
In this paper, butanol effects on combustion process were investigated through conventional methods and optical diagnostics. First, blends of 80% diesel and 20% n-butanol (BU20) were used in a four cylinder, turbocharged, water cooled, DI diesel engine, equipped with a common rail injection system. Management of timing and injection pressure was carried out to achieve conditions in which the almost total amount of fuel was delivered before auto-ignition. BU20 allowed to attain almost smokeless emissions at lower injection pressure (100 MPa) than diesel fuel (120 MPa). Smokeless conditions were achieved with a slight increase in NOx emissions (around 20%) and a minor penalty for the specific fuel consumption.
Afterward, the blends effects on the combustion process were studied in the combustion chamber of a single cylinder compression ignition engine equipped with the same common rail multi-jets injection system. Spray combustion and pollutant formation were investigated by UV–visible digital imaging and natural emission spectroscopy. UV–visible emission spectroscopy was used for the detection of the chemical markers of combustion process. Chemiluminescence signals, due to OH, HCO and CO2 emission bands were detected. OH emission was correlated to NOx measured at the exhaust. The soot spectral feature in the visible wavelength range was related to the engine out soot emissions.
•Experimental investigations employing diesel fuel (BU00) and blend of 80% diesel-20% n-butanol (BU20) in C.I. engines.•BU20 reduced exhaust emissions of NOx and soot without significant penalties on performance.•Optical investigations showed that BU20 promoted faster formation and higher concentration of OH in the combustion chamber.•This effect induced faster soot oxidation phase and produced a like-smokeless combustion in the early injection condition.
The CERN Large Hadron Collider (LHC) is designed to collide proton beams of unprecedented energy, in order to extend the frontiers of high-energy particle physics. During the first very successful ...running period in 2010–2013, the LHC was routinely storing protons at 3.5–4 TeV with a total beam energy of up to 146 MJ, and even higher stored energies are foreseen in the future. This puts extraordinary demands on the control of beam losses. An uncontrolled loss of even a tiny fraction of the beam could cause a superconducting magnet to undergo a transition into a normal-conducting state, or in the worst case cause material damage. Hence a multistage collimation system has been installed in order to safely intercept high-amplitude beam protons before they are lost elsewhere. To guarantee adequate protection from the collimators, a detailed theoretical understanding is needed. This article presents results of numerical simulations of the distribution of beam losses around the LHC that have leaked out of the collimation system. The studies include tracking of protons through the fields of more than 5000 magnets in the 27 km LHC ring over hundreds of revolutions, and Monte Carlo simulations of particle-matter interactions both in collimators and machine elements being hit by escaping particles. The simulation results agree typically within a factor 2 with measurements of beam loss distributions from the previous LHC run. Considering the complex simulation, which must account for a very large number of unknown imperfections, and in view of the total losses around the ring spanning over 7 orders of magnitude, we consider this an excellent agreement. Our results give confidence in the simulation tools, which are used also for the design of future accelerators.
The effect of n-butanol on the combustion process in a DISI engine was investigated through in-cylinder pressure measurements and optical data. An optical engine was equipped with a commercial head ...and with high pressure wall guided injection system. 2000 rpm engine speed was chosen as representative for mid-road load automotive use. Two partially open throttle conditions were tested. All trials were performed at close to stoichiometric air–fuel ratio. Optical diagnostics based on UV–visible imaging and natural emission spectroscopy were applied to study the combustion process from spark ignition to exhaust valve opening. A custom post-detection procedure applied to digital imaging data allowed evaluating the flame area. Results were correlated with volume fraction burned obtained through thermodynamic analysis. UV–visible spectroscopy was applied to investigate formation and evolution of the main chemical compounds characterizing spark ignition and combustion processes. Pollutant measurements (HC, CO, NOx, opacity) at undiluted exhaust, for gasoline and butanol, were correlated with pressure data and in-cylinder optical results. Overall engine operation was found to be similar for both energy sources, with the alternative fuel providing a slight improvement in performance compared to gasoline, for both loads; a significant reduction of NOx and soot was also obtained for alcohol fuelling.
•n-butanol induces little increase in performance and reduction of smoke opacity and NOx.•This study allowed a better understanding of alcohol fuel effect on flame front propagation.•n-butanol is featured by higher flame speed than gasoline but slower flame kernel evolution.•At fixed load, butanol shows comparable OH emission with lower CO–O and CH intensity than gasoline.
The Large Hadron Collider (LHC) at CERN pushes forward to new regimes in terms of beam energy and intensity. In view of the combination of very energetic and intense beams together with sensitive ...machine components, in particular the superconducting magnets, the LHC is equipped with a collimation system to provide protection and intercept uncontrolled beam losses. Beam losses could cause a superconducting magnet to quench, or in the worst case, damage the hardware. The collimation system, which is optimized to provide a good protection with proton beams, has shown a cleaning efficiency with heavy-ion beams which is worse by up to two orders of magnitude. The reason for this reduced cleaning efficiency is the fragmentation of heavy-ion beams into isotopes with a different mass to charge ratios because of the interaction with the collimator material. In order to ensure sufficient collimation performance in future ion runs, a detailed theoretical understanding of ion collimation is needed. The simulation of heavy-ion collimation must include processes in which Pb82+208 ions fragment into dozens of new isotopes. The ions and their fragments must be tracked inside the magnetic lattice of the LHC to determine their loss positions. This paper gives an overview of physical processes important for the description of heavy-ion loss patterns. Loss maps simulated by means of the two tools ICOSIM 1,2 and the newly developed STIER (SixTrack with Ion-Equivalent Rigidities) are compared with experimental data measured during LHC operation. The comparison shows that the tool STIER is in better agreement.
Background
Whether a patient's outcomes are better when receiving nutritional counselling during cardiac rehabilitation (CR) has been scarcely described. We compared changes in weight, waist ...circumference (WC) and blood pressure (BP) in patients attending CR with and without nutritional counselling.
Methods
A retrospective analytical study was conducted in which two groups of patients who completed a phase II CR (36 sessions) were compared: CONTROL n = 144, mean (SD) age = 59 (12) years, 17% females, comprising patients without nutritional counselling (attended between 2003 and 2009), and NUT n = 128, mean (SD) age = 60 (13) years, 27% females, comprising patients with dietitian‐delivered nutritional counselling (attended between 2010 and 2019). Repeated‐measures analysis of variance was used to compare changes in weight, WC, and BP during CR between groups. Logistic regression models determined the probability of reducing weight and systolic BP (SBP).
Results
NUT group decreased weight −1.3 (3.1) kg; P < 0.0001 and WC −3.0 (3.8) cm; P < 0.0001 to a greater extent than CONTROL weight: −0.4 (3.1) kg; P = 0.51; WC: −1.4 (4.5) cm; P = 0.02. In CONTROL, 7% reduced ≥ 5% weight and 31% reduced ≥ 10 mmHg SBP, whereas, in the NUT group, 18% reduced ≥ 5% weight and 47% reduced ≥ 10 mmHg SBP. Patients in NUT (versus CONTROL) were more likely to lose ≥ 5% of weight (odds ratio = 4.27, 95% confidence interval = 1.69–10.80; P < 0.01) and reduce SBP ≥ 10 mmHg (odds ratio = 3.15, 95% confidence interval = 1.58–6.27; P < 0.01).
Conclusions
Patients who received nutritional counselling during CR improved anthropometric measures and were more likely to lose weight and reduce SBP than patients without nutritional counselling.
This retrospective study that included 272 patients who completed cardiac rehabilitation showed that patients with nutritional intervention reduced both weight (−1.3 kg) and waist circumference (−3 cm) more during cardiac rehabilitation compared to the control group. They also were four‐fold more likely to reduce significant weight (≥5% of initial weight) and three‐fold more likely to reduce significant systolic blood pressure (≥10 mmHg) during cardiac rehabilitation.
Particle Image Velocimetry (PIV) and Phase Doppler Anemometry (PDA) have been applied to investigate the droplets size and velocity distribution of a water spray, under the control of a piezo-element ...driven synthetic jet (SJ). Tests were carried out under atmospheric conditions within a chamber test rig equipped with optical accesses at two injection pressures, namely 5 and 10 MPa, exploring the variation of the main spray parameters caused by the synthetic jet perturbations. The SJ orifice has been placed at 45° with respect to the water spray axis; the nozzle body has been moved on its own axis and three different nozzle quotes were tested. PIV measurements have been averaged on 300 trials whereas about 105 samples have been acquired for the PDA tests. For each operative condition, the influence region of the SJ device on the spray has been computed through a T-Test algorithm. The synthetic jet locally interacts with the spray, energizing the region downstream the impact. The effect of the actuator decreases at higher injection pressures and moving the impact region upwards. Droplets coalescence can be detected along the synthetic jet axis, while no significant variations are observed along a direction orthogonal to it.
A study of crystal assisted collimation has been continued at the CERN SPS for different energies of stored beams using 120 GeV/c and 270 GeV/c protons and Pb ions with 270 GeV/c per charge. A bent ...silicon crystal used as a primary collimator deflected halo particles using channeling and directing them into the tungsten absorber. A strong correlation of the beam losses in the crystal and off-momentum halo intensity measured in the first high dispersion (HD) area downstream was observed. In channeling conditions, the beam loss rate induced by inelastic interactions of particles with nuclei is significantly reduced in comparison with the non-oriented crystal. A maximal reduction of beam losses in the crystal larger than 20 was observed with 270 GeV/c protons. The off-momentum halo intensity measured in the HD area was also strongly reduced in channeling conditions. The reduction coefficient was larger than 7 for the case of Pb ions. A strong loss reduction was also detected in regions of the SPS ring far from the collimation area. It was shown by simulations that the miscut angle between the crystal surface and its crystallographic planes doubled the beam losses in the aligned crystal.
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