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1.	Aad, G., et al. (författare) The ATLAS Experiment at the CERN Large Hadron Collider 2008 Ingår i: Journal of Instrumentation. - 1748-0221. ; 3:S08003 Forskningsöversikt (refereegranskat)abstract The ATLAS detector as installed in its experimental cavern at point 1 at CERN is described in this paper. A brief overview of the expected performance of the detector when the Large Hadron Collider begins operation is also presented.
2.	Abat, E., et al. (författare) Combined performance studies for electrons at the 2004 ATLAS combined test-beam 2010 Ingår i: Journal of Instrumentation. - : Institute of Physics (IOP). - 1748-0221. ; 5, s. P11006- Tidskriftsartikel (refereegranskat)abstract In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Radiation Tracker, Bremsstrahlungs-recovery algorithms relying on the LAr calorimeter and results obtained for the E/p ratio and a way how to extract scale parameters will be discussed.
3.	Aamodt, K., et al. (författare) The ALICE experiment at the CERN LHC 2008 Ingår i: Journal of Instrumentation. - 1748-0221. ; 3:S08002 Forskningsöversikt (refereegranskat)abstract ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries, Its overall dimensions are 16 x 16 x 26 m(3) with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.
4.	Hartman, Henrik, et al. (författare) First storage of ion beams in the Double Electrostatic Ion-Ring Experiment : DESIREE 2013 Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 84:5 Tidskriftsartikel (refereegranskat)abstract We report on the first storage of ion beams in the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. We have produced beams of atomic carbon anions and small carbon anion molecules (Cn-, n = 1, 2, 3, 4) in a sputter ion source. The ion beams were accelerated to 10 keV kinetic energy and stored in an electrostatic ion storage ring enclosed in a vacuum chamber at 13 K. For 10 keV C2- molecular anions we measure the residual-gas limited beam storage lifetime to be 448 s +/- 18 s with two independent detector systems. Using the measured storage lifetimes we estimate that the residual gas pressure is in the 10-14 mbar range. When high current ion beams are injected, the number of stored particles does not follow a single exponential decay law as would be expected for stored particles lost solely due to electron detachment in collision with the residual-gas. Instead, we observe a faster initial decay rate, which we ascribe to the effect of the space charge of the ion beam on the storage capacity.
5.	Magnusson, Joel, 1991, et al. (författare) Multiple colliding laser pulses as a basis for studying high-field high-energy physics 2019 Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 100:6 Tidskriftsartikel (refereegranskat)abstract Apart from maximizing the strength of optical electromagnetic fields achievable at high-intensity laser facilities, the collision of several phase-matched laser pulses has been identified theoretically as a trigger of and way to study various phenomena. These range from the basic processes of strong-field quantum electrodynamics to the extraordinary dynamics of the generated electron-positron plasmas. This has paved the way for several experimental proposals aimed at both fundamental studies of matter at extreme conditions and the creation of particle and radiation sources. Because of the unprecedented capabilities of such sources, they have the potential to open up new opportunities for experimental studies in nuclear and quark-gluon physics. We perform here a systematic analysis of different regimes and opportunities achievable with the concept of multiple colliding laser pulses, for both current and upcoming laser facilities. We reveal that several distinct regimes could be within reach of multi-petawatt laser facilities.
6.	Warbinek, Jessica, et al. (författare) A graphene-based neutral particle detector 2019 Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 114:6 Tidskriftsartikel (refereegranskat)abstract A neutral particle detector is presented, in which the traditionally used target material, indium tin oxide (ITO), is replaced by graphene. The graphene-based detector enables collinear photodetachment measurements at a significantly shorter wavelength of light down to 230nm compared to ITO-based detectors, which are limited at 335 nm. Moreover, the background signal from the photoelectric effect is drastically reduced when using graphene. The graphene based detector, reaching 1.7 eV further into the UV energy range, allows increased possibilities for photodetachment studies of negatively charged atoms, molecules, and clusters. Published under license by AIP Publishing.
7.	Milstead, David A., et al. (författare) Study of the material of the ATLAS inner detector for Run 2 of the LHC 2017 Ingår i: Journal of Instrumentation. - : Institute of Physics (IOP). - 1748-0221. ; 12:12 Tidskriftsartikel (refereegranskat)abstract The ATLAS inner detector comprises three different sub-detectors: the pixel detector, the silicon strip tracker, and the transition-radiation drift-tube tracker. The Insertable B-Layer, a new innermost pixel layer, was installed during the shutdown period in 2014, together with modifications to the layout of the cables and support structures of the existing pixel detector. The material in the inner detector is studied with several methods, using a low-luminosity s=13 TeV pp collision sample corresponding to around 2.0 nb-1 collected in 2015 with the ATLAS experiment at the LHC. In this paper, the material within the innermost barrel region is studied using reconstructed hadronic interaction and photon conversion vertices. For the forward rapidity region, the material is probed by a measurement of the efficiency with which single tracks reconstructed from pixel detector hits alone can be extended with hits on the track in the strip layers. The results of these studies have been taken into account in an improved description of the material in the ATLAS inner detector simulation, resulting in a reduction in the uncertainties associated with the charged-particle reconstruction efficiency determined from simulation. © 2017 CERN.
8.	Berntsen, Peter, 1974, et al. (författare) The serial millisecond crystallography instrument at the Australian Synchrotron incorporating the "Lipidico" injector 2019 Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 90:8 Tidskriftsartikel (refereegranskat)abstract A serial millisecond crystallography (SMX) facility has recently been implemented at the macromolecular crystallography beamline, MX2 at the Australian Synchrotron. The setup utilizes a combination of an EIGER X 16M detector system and an in-house developed high-viscosity injector, "Lipidico." Lipidico uses a syringe needle to extrude the microcrystal-containing viscous media and it is compatible with commercially available syringes. The combination of sample delivery via protein crystals suspended in a viscous mixture and a millisecond frame rate detector enables high-throughput serial crystallography at the Australian Synchrotron. A hit-finding algorithm, based on the principles of "robust-statistics," is employed to rapidly process the data. Here we present the first SMX experimental results with a detector frame rate of 100 Hz (10 ms exposures) and the Lipidico injector using a mixture of lysozyme microcrystals embedded in high vacuum silicon grease. Details of the experimental setup, sample injector, and data analysis pipeline are designed and developed as part of the Australian Synchrotron SMX instrument and are reviewed here. Published under license by AIP Publishing.
9.	Ferri, Julien, et al. (författare) Generation of attosecond electron bunches and x-ray pulses from few-cycle femtosecond laser pulses 2021 Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 63:4 Tidskriftsartikel (refereegranskat)abstract Laser-plasma electron accelerators can be used to produce high-intensity x-rays, as electrons accelerated in wakefields emit radiation due to betatron oscillations. Such x-ray sources inherit the features of the electron beam; sub-femtosecond electron bunches produce betatron sources of the same duration, which in turn allow probing matter on ultrashort time scales. In this paper we show, via Particle-in-Cell simulations, that attosecond electron bunches can be obtained using low-energy, ultra-short laser beams both in the self-injection and the controlled injection regimes at low plasma densities. However, only in the controlled regime does the electron injection lead to a stable, isolated attosecond electron bunch. Such ultrashort electron bunches are shown to emit attosecond x-ray bursts with high brilliance.
10.	Isaksson, Oscar, et al. (författare) An optical levitation system for a physics teaching laboratory 2018 Ingår i: American Journal of Physics. - : American Association of Physics Teachers (AAPT). - 0002-9505 .- 1943-2909. ; 86:2, s. 135-142 Tidskriftsartikel (refereegranskat)abstract We describe an experimental system based on optical levitation of an oil droplet. When combined with an applied electric field and a source of ionizing radiation, the setup permits the investigation of physical phenomena such as radiation pressure, light diffraction, the motion of a charged particle in an oscillating electric field, and the interaction of ionizing radiation with matter. The trapping occurs by creating an equilibrium between a radiation pressure force and the force of gravity. We have found that an oil droplet can be trapped for at least nine hours. The system can be used to measure the size and total electric charge on the trapped droplet. The intensity of the light from the trapping laser that is scattered by the droplet is sufficient to allow the droplet to be easily seen with the naked eye, covered by laser alignment goggles. When oscillating under the influence of an ac electric field, the motion of the droplet can be described as that of a driven, damped harmonic oscillator. The magnitude and polarity of the charge can be altered by exposing the droplet to ionizing radiation from a low-activity radioactive source. Our goal was to design a hands-on setup that allows undergraduate and graduate students to observe and better understand fundamental physical processes. (C) 2018 American Association of Physics Teachers.
11.	Windelius, Olle, 1972, et al. (författare) Photoelectron angular distributions in photodetachment from P 2021 Ingår i: Physical Review A. - 2469-9926 .- 2469-9934. ; 103:3 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.
12.	Lestinsky, M., et al. (författare) Physics book: CRYRING@ESR 2016 Ingår i: European Physical Journal: Special Topics. - : Springer Science and Business Media LLC. - 1951-6401 .- 1951-6355. ; 225:5, s. 797-882 Forskningsöversikt (refereegranskat)abstract The exploration of the unique properties of stored and cooled beams of highly-charged ions as provided by heavy-ion storage rings has opened novel and fascinating research opportunities in the realm of atomic and nuclear physics research. Since the late 1980s, pioneering work has been performed at the CRYRING at Stockholm (Abrahamsson et al. 1993) and at the Test Storage Ring (TSR) at Heidelberg (Baumann et al. 1988). For the heaviest ions in the highest charge-states, a real quantum jump was achieved in the early 1990s by the commissioning of the Experimental Storage Ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt (Franzke 1987) where challenging experiments on the electron dynamics in the strong field regime as well as nuclear physics studies on exotic nuclei and at the borderline to atomic physics were performed. Meanwhile also at Lanzhou a heavy-ion storage ring has been taken in operation, exploiting the unique research opportunities in particular for medium-heavy ions and exotic nuclei (Xia et al. 2002).
13.	Thiele, Illia, 1989, et al. (författare) Electron Beam Driven Generation of Frequency-Tunable Isolated Relativistic Subcycle Pulses 2019 Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 122 Tidskriftsartikel (refereegranskat)abstract © 2019 American Physical Society. We propose a novel scheme for frequency-tunable subcycle electromagnetic pulse generation. To this end a pump electron beam is injected into an electromagnetic seed pulse as the latter is reflected by a mirror. The electron beam is shown to be able to amplify the field of the seed pulse while upshifting its central frequency and reducing its number of cycles. We demonstrate the amplification by means of 1D and 2D particle-in-cell simulations. In order to explain and optimize the process, a model based on fluid theory is proposed. We estimate that using currently available electron beams and terahertz pulse sources, our scheme is able to produce millijoule-strong midinfrared subcycle pulses.
14.	Fritioff, T., et al. (författare) Purification of radioactive neutron-rich argon beams using an ion source in charge breeding mode 2006 Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 556:1, s. 31-37 Tidskriftsartikel (refereegranskat)abstract Measurements of nuclear properties of some neutron-rich asymmetric fission isotopes at an ISOL laboratory present a severe problem when a plasma ion source is used as the primary ion-source. The problem is associated with intense multi-charged symmetric fission contaminants that cannot be mass-separated from asymmetric fission products. In this work we demonstrate how this problem can be overcome on-line by using an electron cyclotron resonance ion source (ECRIS) as a charge-breeding secondary ion-source. Mixed Ar+/Kr2+/Xe3+ radioactive beams from an plasma ion-source were injected into the PHOENIX ECRIS that currently is installed at the ISOLDE facility at CERN in order to improve the ratio of Ar to the background contaminants of Kr and Xe. The signal to noise ratio was improved by more than two orders of magnitude after charge-breeding and mass-separation of the Ar8+, Ar9+ beams. The information on the decay of the Ar-48 nucleus obtained in these tests is useful for a better understanding of the origin of the Ca-48/Ca-46 meteorite isotopic anomaly. Potential applications of the method are discussed.
15.	Aartsen, M. G., et al. (författare) Computational techniques for the analysis of small signals in high-statistics neutrino oscillation experiments 2020 Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 977 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.
16.	Piscitelli, Francesco, et al. (författare) Neutron reflectometry on highly absorbing films and its application to (B4C)-B-10-based neutron detectors 2016 Ingår i: Royal Society of London. Proceedings A. Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-5021 .- 1471-2946. ; 472:2185 Tidskriftsartikel (refereegranskat)abstract Neutron reflectometry is a powerful tool used for studies of surfaces and interfaces. The absorption in the typical studied materials is neglected and this technique is limited only to the reflectivity measurement. For strongly absorbing nuclei, the absorption can be directly measured by using the neutron-induced fluorescence technique which exploits the prompt particle emission of absorbing isotopes. This technique is emerging from soft matter and biology where highly absorbing nuclei, in very small quantities, are used as a label for buried layers. Nowadays, the importance of absorbing layers is rapidly increasing, partially because of their application in neutron detection; a field that has become more active also due to the He-3-shortage. We extend the neutron-induced fluorescence technique to the study of layers of highly absorbing materials, in particular (B4C)-B-10. The theory of neutron reflectometry is a commonly studied topic; however, when a strong absorption is present the subtle relationship between the reflection and the absorption of neutrons is not widely known. The theory for a general stack of absorbing layers has been developed and compared to measurements. We also report on the requirements that a (B4C)-B-10 layer must fulfil in order to be employed as a converter in neutron detection.
17.	Göök, A., et al. (författare) Particle emission angle determination in Frisch grid ionization chambers by electron drift-time measurements 2010 Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 621:1-3, s. 401-405 Tidskriftsartikel (refereegranskat)abstract The double kinetic energy measurement of fission fragments with a double-sided Frisch grid ionization chamber allows a careful determination of the emission angle, which is essential in order to apply appropriate energy-loss corrections. We present a drift-time method, which uses the time that free electrons need to drift from the location of their creation, e.g. by a fission fragment in the counting gas, to the grid, before inducing a signal on the anode. Such a measurement leaves energy and angular information fully decoupled. We demonstrate the applicability of the drift-time method for the example of the 234,238U (γ,f) reactions performed at the superconducting Darmstadt electron linear accelerator. The angular resolutions achieved with this method are comparable to those obtained with other methods.
18.	Gonoskov, Arkady, 1984, et al. (författare) Employing machine learning for theory validation and identification of experimental conditions in laser-plasma physics 2019 Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 9:1 Tidskriftsartikel (refereegranskat)abstract The validation of a theory is commonly based on appealing to clearly distinguishable and describable features in properly reduced experimental data, while the use of ab-initio simulation for interpreting experimental data typically requires complete knowledge about initial conditions and parameters. We here apply the methodology of using machine learning for overcoming these natural limitations. We outline some basic universal ideas and show how we can use them to resolve long-standing theoretical and experimental difficulties in the problem of high-intensity laser-plasma interactions. In particular we show how an artificial neural network can “read” features imprinted in laser-plasma harmonic spectra that are currently analysed with spectral interferometry.
19.	Lundholm, Ida V., et al. (författare) Considerations for three-dimensional image reconstruction from experimental data in coherent diffractive imaging 2018 Ingår i: IUCrJ. - : International Union of Crystallography. - 2052-2525. ; 5, s. 531-541 Tidskriftsartikel (refereegranskat)abstract Diffraction before destruction using X-ray free-electron lasers (XFELs) has the potential to determine radiation-damage-free structures without the need for crystallization. This article presents the three-dimensional reconstruction of the Melbournevirus from single-particle X-ray diffraction patterns collected at the LINAC Coherent Light Source (LCLS) as well as reconstructions from simulated data exploring the consequences of different kinds of experimental sources of noise. The reconstruction from experimental data suffers from a strong artifact in the center of the particle. This could be reproduced with simulated data by adding experimental background to the diffraction patterns. In those simulations, the relative density of the artifact increases linearly with background strength. This suggests that the artifact originates from the Fourier transform of the relatively flat background, concentrating all power in a central feature of limited extent. We support these findings by significantly reducing the artifact through background removal before the phase-retrieval step. Large amounts of blurring in the diffraction patterns were also found to introduce diffuse artifacts, which could easily be mistaken as biologically relevant features. Other sources of noise such as sample heterogeneity and variation of pulse energy did not significantly degrade the quality of the reconstructions. Larger data volumes, made possible by the recent inauguration of high repetition-rate XFELs, allow for increased signal-to-background ratio and provide a way to minimize these artifacts. The anticipated development of three-dimensional Fourier-volume-assembly algorithms which are background aware is an alternative and complementary solution, which maximizes the use of data.
20.	Blomberg, Sara, et al. (författare) Combining synchrotron light with laser technology in catalysis research 2018 Ingår i: Journal of Synchrotron Radiation. - 1600-5775 .- 0909-0495. ; 25:5, s. 1389-1394 Tidskriftsartikel (refereegranskat)abstract High-energy surface X-ray diffraction (HESXRD) provides surface structural information with high temporal resolution, facilitating the understanding of the surface dynamics and structure of the active phase of catalytic surfaces. The surface structure detected during the reaction is sensitive to the composition of the gas phase close to the catalyst surface, and the catalytic activity of the sample itself may affect the surface structure, which in turn may complicate the assignment of the active phase. For this reason, planar laser-induced fluorescence (PLIF) and HESXRD have been combined during the oxidation of CO over a Pd(100) crystal. PLIF complements the structural studies with an instantaneous two-dimensional image of the CO2 gas phase in the vicinity of the active model catalyst. Here the combined HESXRD and PLIF operandomeasurements of CO oxidation over Pd(100) are presented, allowing for an improved assignment of the correlation between sample structure and the CO2distribution above the sample surface with sub-second time resolution.
21.	Aalbers, J., et al. (författare) A next-generation liquid xenon observatory for dark matter and neutrino physics 2023 Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 50:1 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.
22.	Aad, G, et al. (författare) Performance of the upgraded PreProcessor of the ATLAS Level-1 Calorimeter Trigger 2020 Ingår i: Journal of Instrumentation. - : IOP Publishing. - 1748-0221. ; 15:11 Tidskriftsartikel (refereegranskat)abstract The PreProcessor of the ATLAS Level-1 Calorimeter Trigger prepares the analogue trigger signals sent from the ATLAS calorimeters by digitising, synchronising, and calibrating them to reconstruct transverse energy deposits, which are then used in further processing to identify event features. During the first long shutdown of the LHC from 2013 to 2014, the central components of the PreProcessor, the Multichip Modules, were replaced by upgraded versions that feature modern ADC and FPGA technology to ensure optimal performance in the high pile-up environment of LHC Run 2. This paper describes the features of the new Multichip Modules along with the improvements to the signal processing achieved. c 2020 CERN for the benefit of the ATLAS collaboration. Published by IOP Publishing Ltd on behalf of Sissa Medialab.
23.	Agåker, Marcus, et al. (författare) Spectroscopy in the vacuum-ultraviolet 2011 Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 5:5, s. 248-248 Tidskriftsartikel (refereegranskat)
24.	Gatchell, Michael, et al. (författare) Commissioning of the DESIREE storage rings - a new facility for cold ion-ion collisions 2014 Ingår i: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013). - : Institute of Physics (IOP). ; 488:1 Konferensbidrag (refereegranskat)abstract We report on the ongoing commissioning of the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. Beams of atomic carbon anions (C-) and smaller carbon anion molecules (C-2(-), C-3(-), C-4(-) etc.) have been produced in a sputter ion source, accelerated to 10 keV or 20 keV, and stored successfully in the two electrostatic rings. The rings are enclosed in a common vacuum chamber cooled to below 13 Kelvin. The DESIREE facility allows for studies of internally relaxed single isolated atomic, molecular and cluster ions and for collision experiments between cat-and anions down to very low center-of-mass collision energies (meV scale). The total thermal load of the vacuum chamber at this temperature is measured to be 32 W. The decay rates of stored ion beams have two components: a non-exponential component caused by the space charge of the beam itself which dominates at early times and an exponential term from the neutralization of the beam in collisions with residual gas at later times. The residual gas limited storage lifetime of carbon anions in the symmetric ring is over seven minutes while the 1/e lifetime in the asymmetric ring is measured to be about 30 seconds. Although we aim to improve the storage in the second ring, the number of stored ions are now sufficient for many merged beams experiments with positive and negative ions requiring milliseconds to seconds ion storage.
25.	Li, P. F., et al. (författare) Dynamics of low energy electrons transmitting throughstraight glass capillary: Tilt angle dependence br 2022 Ingår i: Acta Physica Sinica. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 71:8 Tidskriftsartikel (refereegranskat)abstract It is a hot topic that using glass capillary to focus and shape the charged particle beam, for it isinexpensive and simple. There are the cases that single glass capillaries are used to make the microbeam of thepositive ions. When it comes to electrons, their transmitting through insulating capillaries is complex and theattempt to use the glass capillary to produce electron beams in the size of micrometer needs further exploring.In this paper, the charging-up process of the 900-eV electrons transmitting through a glass capillary withthe grounded conductive-coated outer surface is reported. Two-dimensional angular distributions of thetransmitted electrons and their time evolutions are measured for the cases of various tilt angles of glass tube. Itis found that there are a considerable number of transmitted electrons at the tilt angle exceeding thegeometrical opening angle (1 degrees) of the glass tube. The intensity of transmitted electrons for large tilt angle (i.e. -1.15 degrees)can be considered as first falling to zero, then keeping zero for a long time, finally rising to a certain stablevalue. Correspondingly, the angular distribution center experiences moving towards negative-positive-negative-settled. The energy losses are measured for various tilt angles. The larger the tilt angles, the larger the energyloss of transmitted electrons is. To better understand the physics behind the observed phenomena, thesimulations of the energy loss for transmitted electrons at various tilt angles are performed by the Monte Carlomethod. The comparation between the simulated energy losses and the measured energy losses shows that theexperimental results are well explained by multiple deflections from the wall.
26.	Litvinov, Yu.A., et al. (författare) Nuclear physics experiments with ion storage rings 2013 Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 317:PART B, s. 603-616 Tidskriftsartikel (refereegranskat)abstract In the last two decades a number of nuclear structure and astrophysics experiments were performed at heavy-ion storage rings employing unique experimental conditions offered by such machines. Furthermore, building on the experience gained at the two facilities presently in operation, several new storage ring projects were launched worldwide. This contribution is intended to provide a brief review of the fast growing field of nuclear structure and astrophysics research at storage rings.
27.	Molander, Simon, 1980- (författare) Studies of Top Physics Sensitivity and of Pile-Up Effects on Energy Reconstruction in the ATLAS Detector : A Licentiate Thesis About the Treatment of Troublesome $\tau$ and Producing Pulses to Probe Pile-up Problems 2016 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract This thesis presents two studies conducted using the ATLAS detectorat the Large Hadron Collider. The first one is a technical study abouthow out-of-time pile-up affects energy reconstruction using the optimalfiltering 2 algorithm in the TILE calorimeter sub detector. The studyis conducted using a pulse simulator software that is also described.Although the algorithm is potentially sensitive to the effects ofout-of-time pile-up, the effects under actual running conditions areestimated to be lower than 1.5 ADC counts for 68 \% of the pulses,which is considered a small effect. It is also shown that out-of-timepile-up is a potential reason to get negatively reconstructed energies.The second study regards a measurement of the $t\bar{tZ}$ cross sectionwith one hadronically decaying $\tau$ leptons and two lighter leptonsin the final state using 8 TeV data. The conclusion is that it isnot possible to make a significant such measurement from the 8 TeVdata due to low efficiencies in reconstruction of $\tau$ leptons.In addition to these two studies, this thesis also contain brief overviewsof the atlas detector and the standard model of particles and interactions.
28.	Spartà, R., et al. (författare) Probing proton halo effects in the 8 B+ 64 Zn collision around the Coulomb barrier 2021 Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 820 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.
29.	Björklund Svensson, Jonas, et al. (författare) Low-divergence femtosecond X-ray pulses from a passive plasma lens 2021 Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 17:5, s. 639-645 Tidskriftsartikel (refereegranskat)abstract Electron and X-ray beams originating from compact laser-wakefield accelerators have very small source sizes that are typically on the micrometre scale. Therefore, the beam divergences are relatively high, which makes it difficult to preserve their high quality during transport to applications. To improve on this, tremendous efforts have been invested in controlling the divergence of the electron beams, but no mechanism for generating collimated X-ray beams has yet been demonstrated experimentally. Here we propose and realize a scheme where electron bunches undergoing focusing in a dense, passive plasma lens can emit X-ray pulses with divergences approaching the incoherent limit. Compared with conventional betatron emission, the divergence of this so-called plasma lens radiation is reduced by more than an order of magnitude in solid angle, while maintaining a similar number of emitted photons per electron. This X-ray source offers the possibility of producing brilliant and collimated few-femtosecond X-ray pulses for ultra-fast science, in particular for studies based on X-ray diffraction and absorption spectroscopy. X-ray pulses with low divergences are produced in a laser-wakefield accelerator by focusing electron bunches in a dense passive plasma lens.
30.	Naumovska, Elena, et al. (författare) Local structure of hydrated nanocrystalline films of the proton conductor BaZr1-xScxO3-x/2 studied by infrared spectroscopy 2024 Ingår i: Vibrational Spectroscopy. - : Elsevier. - 0924-2031 .- 1873-3697. ; 130 Tidskriftsartikel (refereegranskat)abstract We report results from a study of the local structure of hydrated nanocrystalline 2 m films of the well known proton conductor BaZr1-xScxO3-x/2 with x = 0.45, 0.54 and 0.64, using infrared (IR) spectroscopy. The films were prepared by magnetron sputtering. Analysis of the IR spectra focused on the O–H stretching region (2000—3700 cm-1), which reveals the presence of several distinct O–H stretching bands for which the intensity and frequency of each band vary in an unsystematic manner with Sc concentration. The spectra for the two higher Sc concentrations, x = 0.54 and 0.64, exhibit a distinct, highly intense O–H stretching band centered at around 3400–3500 cm-1, which is assigned to relatively symmetric, weakly hydrogen-bonding, proton configurations. The spectrum for the lower Sc concentration, x = 0.45, does not feature such a band but a broader, weaker, O–H stretching band between approximately 2500 and 3700 cm-1, suggesting that the protons are more homogeneously distributed over a range of different local proton coordinations in this relatively weakly doped material. A comparison to the IR spectra of powder samples of similar compositions suggests that for x = 0.45, the spectra and proton coordination of films and powder samples are similar, whereas for x = 0.54 and 0.64, a larger fraction of protons seems to be located in weakly hydrogen-bonding proton configurations in the films compared to the respective powder samples.
31.	Wiedorn, Max O., et al. (författare) Megahertz serial crystallography 2018 Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9 Tidskriftsartikel (refereegranskat)abstract The new European X-ray Free-Electron Laser is the first X-ray free-electron laser capable of delivering X-ray pulses with a megahertz inter-pulse spacing, more than four orders of magnitude higher than previously possible. However, to date, it has been unclear whether it would indeed be possible to measure high-quality diffraction data at megahertz pulse repetition rates. Here, we show that high-quality structures can indeed be obtained using currently available operating conditions at the European XFEL. We present two complete data sets, one from the well-known model system lysozyme and the other from a so far unknown complex of a beta-lactamase from K. pneumoniae involved in antibiotic resistance. This result opens up megahertz serial femtosecond crystallography (SFX) as a tool for reliable structure determination, substrate screening and the efficient measurement of the evolution and dynamics of molecular structures using megahertz repetition rate pulses available at this new class of X-ray laser source.
32.	Björklund Svensson, Jonas (författare) Extreme Electron Beams and Brilliant X-rays : Generation, Manipulation and Characterization of Relativistic Electron Beams for and from Plasma-Based Accelerators 2020 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract This thesis is based on work done by the author on the development of plasma-based electron accelerators driven by ultra-intense laser pulses and dense electron bunches. Plasma based accelerators have several benefits, such as accelerating fields around 1000 times stronger than in “conventional” radio-frequency accelerators, which can allow for shrinking the overall footprint of the accelerator. They can also allow for generating electron beams with unprecedented peak currents and ultra-low emittances, meaning that a large number of electrons can be packed into a very short time duration and that the quality of the bunches is high. They can also be used to generate X-ray pulses with durations only otherwise achievable at a few large accelerator facilities, using a laboratory setup the size of a large living room. These characteristics make plasma-based accelerators interesting as a technology for future particle colliders and free-electron lasers, as well as, for example, smaller and more available X-ray sources with particular source characteristics such as ultra-short pulse durations.This thesis describes both numerical and experimental studies on plasma-based accelerators. The experimental work has mainly been on generating electron bunches and X-ray pulses using a laser-wakefield accelerator, as well as applications of the generated X-rays. The results from this branch of the research include the identification and demonstration of a new regime for laser-driven X-ray generation, which produces pulses with significantly reduced divergence compared to the standard method, simplifying the subsequent use of such pulses in applications.The numerical work has been focused towards conventional radio-frequency accelerators, concerning the shaping of electron bunches from such an accelerator for use in electron beam-driven plasma-wakefield acceleration. Themain point in this research has been removing or circumventing detrimental effects that occur during acceleration and transport, to create bunches which can drive stable wakes. One of the results from this research is an optimization strategy for certain bunch compressors, leading to a decrease in chromatic and geometric aberrations in the bunch. The common thread through both experimental and numerical work is plasma-based acceleration of electrons, and as such there is a larger overlap between these two parts than might initially be seen.
33.	Cantono, Giada, et al. (författare) Laser-driven proton acceleration from ultrathin foils with nanoholes 2021 Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 11:1 Tidskriftsartikel (refereegranskat)abstract Structured solid targets are widely investigated to increase the energy absorption of high-power laser pulses so as to achieve efficient ion acceleration. Here we report the first experimental study of the maximum energy of proton beams accelerated from sub-micrometric foils perforated with holes of nanometric size. By showing the lack of energy enhancement in comparison to standard flat foils, our results suggest that the high contrast routinely achieved with a double plasma mirror does not prevent damaging of the nanostructures prior to the main interaction. Particle-in-cell simulations support that even a short scale length plasma, formed in the last hundreds of femtoseconds before the peak of an ultrashort laser pulse, fills the holes and hinders enhanced electron heating. Our findings reinforce the need for improved laser contrast, as well as for accurate control and diagnostics of on-target plasma formation.
34.	Ntemou, Eleni, et al. (författare) Picosecond pulsed beams of light and heavy keV ions at the Time-of-Flight Medium energy ion scattering system at Uppsala University 2024 Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 556 Tidskriftsartikel (refereegranskat)abstract A 16 MHz electrostatic beam chopper is implemented at the Uppsala University ToF-MEIS system to complement the 4 MHz sinusoidal scanning, refining the resolution without drift-tube bunching. The system is benchmarked with H2+, He+, and Ne+ ions in transmission and backscattering geometries. The estimated true pulse duration for 60 keV He+ is 34 ps while the direct beam impinging on the detector resulted in measured pulse widths of 295 ps for He ions and 481 ps for Ne ions. In backscattering geometries, ions impinging on the target yield measured pulse durations of 459 ns for H ions, 550 ps for He ions and 810 ps for Ne ions and lead to energy resolution measurements of 2.4 keV (100 keV H), 0.9 keV (60 keV He), and 2.4 keV (160 keV Ne). Discussions cover straggling effects on achievable energy resolution and how to obtain estimates of the true duration of the ion pulse.
35.	Rigamonti, D., et al. (författare) The single crystal diamond-based diagnostic suite of the JET tokamak for 14 MeV neutron counting and spectroscopy measurements in DT plasmas 2024 Ingår i: Nuclear Fusion. - : Institute of Physics (IOP). - 0029-5515 .- 1741-4326. ; 64:1 Tidskriftsartikel (refereegranskat)abstract The Joint European Torus (JET) has recently conducted its second deuterium-tritium (DT) experimental campaign DTE2, providing unique opportunity for studying both physics and engineering aspects of nuclear fusion plasmas. This also allowed the exploitation of new diagnostics and technologies that were not available during the first JET DT campaign held in 1997. Among these new instruments, the enhancement projects of the JET nuclear diagnostics lead to the development and installation of synthetic single crystal diamond detectors along different collimated line of sights. This paper describes the single crystal diamond-based diagnostic suite of the JET tokamak and the enhanced 14 MeV neutron diagnostic capabilities in terms of neutron yield and high resolution neutron spectroscopy. The diamond characterization measurements and the calibration procedure at JET are shown, together with performance of the diamond based neutron spectrometer as 14 MeV neutron yield monitor which allows the separation of 2.5 MeV and 14 MeV neutrons in trace tritium plasmas. The first high-resolution 14 MeV neutron spectroscopy measurements in neutral beam injection-heated DT plasmas are presented, allowing thermal and non-thermal neutron component separation. Prospects for the diagnose of DT burning plasmas such as ITER and SPARC will be presented.
36.	Milstead, David A., et al. (författare) Comparison between simulated and observed LHC beam backgrounds in the ATLAS experiment at Ebeam=4 TeV 2018 Ingår i: Journal of Instrumentation. - : Institute of Physics Publishing (IOPP). - 1748-0221. ; 13:12 Tidskriftsartikel (refereegranskat)abstract Results of dedicated Monte Carlo simulations of beam-induced background (BIB) in the ATLAS experiment at the Large Hadron Collider (LHC) are presented and compared with data recorded in 2012. During normal physics operation this background arises mainly from scattering of the 4 TeV protons on residual gas in the beam pipe. Methods of reconstructing the BIB signals in the ATLAS detector, developed and implemented in the simulation chain based on the \textsc{Fluka} Monte Carlo simulation package, are described. The interaction rates are determined from the residual gas pressure distribution in the LHC ring in order to set an absolute scale on the predicted rates of BIB so that they can be compared quantitatively with data. Through these comparisons the origins of the BIB leading to different observables in the ATLAS detectors are analysed. The level of agreement between simulation results and BIB measurements by ATLAS in 2012 demonstrates that a good understanding of the origin of BIB has been reached. © 2018 CERN for the benefit of the ATLAS collaboration.
37.	Ferri, Julien, 1990, et al. (författare) Enhanced target normal sheath acceleration using colliding laser pulses 2019 Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 2 Tidskriftsartikel (refereegranskat)abstract Laser-solid interaction can lead to the acceleration of protons to tens of MeV. Here, we show that a strong enhancement of this acceleration can be achieved by splitting the laser pulse to two parts of equal energy and opposite incidence angles. Through the use of two- and three-dimensional Particle-In-Cell simulations, we find that the multi-pulse interaction leads to a standing wave pattern at the front side of the target, with an enhanced electric field and a substantial modification of the hot electron generation process. This in turn leads to significant improvement of the proton spectra, with an almost doubling of the accelerated proton energy and five-fold enhancement of the number of protons. The proposed scheme is robust with respect to incidence angles for the laser pulses, providing flexibility to the scheme, which should facilitate its experimental implementation.
38.	Hidvégi, Attila, 1979- (författare) FPGA-based Instrumentation for Advanced Physics Experiments 2011 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Modern physical experiments often demand advanced instrumentation based on advances in technology. This work describes four instrumentation physics projects that are based on modern, high-capacity Field-Programmable Gate Arrays, making use of their versatility, programmability, high bandwidth communication interfaces and signal processing capabilities. In the first project, a jet-finding algorithm for the ATLAS detector at the LHC experiment at CERN was developed and implemented, and different verification methods were created to validate the functionality and reliability. The experiment uses a three level trigger system, where the first level uses custom FPGA-based hardware for analysis of collision events in real-time. The second project was an advanced timing and triggering distribution system for the new European X-Ray Free Electron Laser (XFEL) facility at DESY in Hamburg. XFEL will enable scientists to study nano structures on the atomic scale. Its laser pulses will have the strongest peak power in the world with extremely short duration and a high repetition rate, which will even allow filming of chemical reactions. The timing system uses modern FPGAs to distribute high-speed signals over optical fibers and to deliver clocks and triggers with high accuracy. The third project was a new data acquisition board based on high-speed ADCs combined with high-performance FPGAs, to process data from segmented Ge-detectors in real-time. The aim was to improve system performance by greatly oversampling and filtering the analog signals to achieve greater effective resolution. Finally, an innovative solution was developed to replace an aging system used at CERN and Stockholm University to test vital electronics in the Tile Calorimeters of the ATLAS detector system. The new system is entirely based on a commercial FPGA development board, where all necessary custom communication protocols were implemented in firmware to emulate obsolete hardware.
39.	Aad, G., et al. (författare) Modelling Z -> tau tau processes in ATLAS with tau-embedded Z -> mu mu data 2015 Ingår i: Journal of Instrumentation. - : Elsevier. - 1748-0221. ; 10 Tidskriftsartikel (refereegranskat)
40.	Baum, Sebastian, et al. (författare) Impact of a XENONnT signal on LHC dijet searches 2019 Ingår i: Journal of High Energy Physics. - : Springer. - 1029-8479 .- 1126-6708. ; 2019:7 Tidskriftsartikel (refereegranskat)abstract It is well-known that dark matter (DM) direct detection experiments and the LHC are complementary, since they probe physical processes occurring at different energy scales. And yet, there are aspects of this complementarity which are still not fully understood, or exploited. For example, what is the impact that the discovery of DM at XENONnT would have on present and future searches for DM in LHC final states involving a pair of hadronic jets? In this work we investigate the impact of a XENONnT signal on the interpretation of current dijet searches at the LHC, and on the prospects for dijet signal discovery at the High-Luminosity (HL) LHC in the framework of simplified models. Specifically, we focus on a general class of simplified models where DM can have spin 0, 1/2 or 1, and interacts with quarks through the exchange of a scalar, pseudo-scalar, vector, or pseudo-vector mediator. We find that exclusion limits on the mediator’s mass and its coupling to quarks from dijet searches at the LHC are significantly affected by a signal at XENONnT, and that O(100) signal events at XENONnT would drastically narrow the region in the parameter space of simplified models where a dijet signal can be discovered at 5σ C.L. at the HL-LHC.
41.	Billnert, Robert, 1981, et al. (författare) Novel Scintillation Detectors for Prompt Fission γ-Ray Measurements 2012 Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 31, s. 29-34 Konferensbidrag (refereegranskat)abstract In this work we present first results from measurements of prompt fission γ-rays from the spontaneous fission in 252Cf. New and accurate data on corresponding γ-rays from the reactions 235U(nth,f) and 239Pu(nth,f) are highly demanded for the modeling of new Generation-IV nuclear reactor systems. For these experiments we employed scintillation detectors made out of new materials (LaBr3, LaCl3 and CeBr3), whose properties were necessary to know in order to obtain reliable results. Hence, we have characterized these detectors. In all the important properties these detectors outshine sodium-iodine detectors that where used in the 1970s, when the existing data had been acquired. Our finding is that the new generation of scintillation detectors is indeed promising, as far as an improved precision of the demanded data is concerned.
42.	Eklund, Gustav, et al. (författare) Final-state-resolved mutual neutralization of Na+ and D- 2021 Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 103:3 Tidskriftsartikel (refereegranskat)abstract The present paper reports on a merged-beam experiment on mutual neutralization between Na+ and D-. For this experiment, we have used the DESIREE ion-beams storage-ring facility. The reaction products are detected using a position- and time-sensitive detector, which ideally allows for determination of the population of each individual quantum state in the final atomic systems. Here, the 4s, 3d, and 4p final states in Na are observed and in all cases the D atom is in its ground state 1s S-2. The respective branching fractions of the states populated in Na are determined by fitting results from a Monte Carlo simulation of the experiment to the measured data. The center-of-mass collision energy is controlled using a set of biased drift tubes, and the branching fractions are measured for energies between 80 meV and 393 meV. The resulting branching fractions are found to agree qualitatively with the only available theoretical calculations for this particular system, which are based on a multichannel Landau-Zener approach using dynamic couplings determined with a linear combination of atomic orbitals model.
43.	Emken, Timon, 1988 (författare) Solar reflection of light dark matter with heavy mediators 2022 Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 105:6 Tidskriftsartikel (refereegranskat)abstract The direct detection of sub-GeV dark matter particles is hampered by their low energy deposits. If the maximum deposit allowed by kinematics falls below the energy threshold of a direct detection experiment, it is unable to detect these light particles. Mechanisms that boost particles from the Galactic halo can therefore extend the sensitivity of terrestrial direct dark matter searches to lower masses. Sub-GeV and sub-MeV dark matter particles can be efficiently accelerated by colliding with thermal nuclei and electrons of the solar plasma, respectively. This process is called "solar reflection."In this paper, we present a comprehensive study of solar reflection via electron and/or nuclear scatterings using Monte Carlo simulations of dark matter trajectories through the Sun. We study the properties of the boosted dark matter particles, obtain exclusion limits based on various experiments probing both electron and nuclear recoils, and derive projections for future detectors. In addition, we find and quantify a novel, distinct annual modulation signature of a potential solar reflection signal which critically depends on the anisotropies of the boosted dark matter flux ejected from the Sun. Along with this paper, we also publish the corresponding research software.
44.	Aad, G., et al. (författare) 2015 Tidskriftsartikel (refereegranskat)
45.	Baird, C. D., et al. (författare) Realising single-shot measurements of quantum radiation reaction in high-intensity lasers 2019 Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 21:5 Tidskriftsartikel (refereegranskat)abstract Modern laser technology is now sufficiently advanced that collisions between high-intensity laser pulses and laser-wakefield-accelerated (LWFA) electron beams can reach the strong-field regime, so that it is possible to measure the transition between the classical and quantum regimes of light-matter interactions. However, the energy spectrum of LWFA electron beams can fluctuate significantly from shot to shot, making it difficult to clearly discern quantum effects in radiation reaction (RR), for example. Here we show how this can be accomplished in only a single laser shot. A millimetre-scale pre-collision drift allows the electron beam to expand to a size larger than the laser focal spot and develop a correlation between transverse position and angular divergence. In contrast to previous studies, this means that a measurement of the beam's energy-divergence spectrum automatically distinguishes components of the beam that hit or miss the laser focal spot and therefore do and do not experience RR.
46.	Ferri, Julien, 1990, et al. (författare) Enhancement of laser-driven ion acceleration in non-periodic nanostructured targets 2020 Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 86:1 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.
47.	Ferri, Julien, 1990, et al. (författare) Proton acceleration by a pair of successive ultraintense femtosecond laser pulses 2018 Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 25 Tidskriftsartikel (refereegranskat)abstract © 2018 Author(s). We investigate the target normal sheath acceleration of protons in thin aluminum targets irradiated at a relativistic intensity by two time-separated ultrashort (35 fs) laser pulses. When the full-energy laser pulse is temporally split into two identical half-energy pulses, and using target thicknesses of 3 and 6 μm, we observe experimentally that the second half-pulse boosts the maximum energy and charge of the proton beam produced by the first half-pulse for time delays below ∼0.6-1 ps. Using two-dimensional particle-in-cell simulations, we examine the variation of the proton energy spectra with respect to the time-delay between the two pulses. We demonstrate that the expansion of the target front surface caused by the first pulse significantly enhances the hot-electron generation by the second pulse arriving after a few hundreds of fs time delay. This enhancement, however, does not suffice to further accelerate the fastest protons driven by the first pulse once three-dimensional quenching effects have set in. This implies a limit to the maximum time delay that leads to proton energy enhancement, which we theoretically determine.
48.	Horny, Vojtech, 1989, et al. (författare) Generation of single attosecond relativistic electron bunch from intense laser interaction with a nanosphere 2021 Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 63:12 Tidskriftsartikel (refereegranskat)abstract Ultrahigh-intensity laser-plasma physics provides unique light and particle beams as well as novel physical phenomena. A recently available regime is based on the interaction between a relativistic intensity few-cycle laser pulse and a sub-wavelength-sized mass-limited plasma target. Here, we investigate the generation of electron bunches under these extreme conditions by means of particle-in-cell simulations. In a first step, up to all electrons are expelled from the nanodroplet and gain relativistic energy from time-dependent local field enhancement at the surface. After this ejection, the electrons are further accelerated as they copropagate with the laser pulse. As a result, a few, or under specific conditions isolated, pC-class relativistic attosecond electron bunches are generated with laser pulse parameters feasible at state-of-the-art laser facilities. This is particularly interesting for some applications, such as generation of attosecond x-ray pulses via Thomson backscattering.
49.	Aartsen, M. G., et al. (författare) The IceCube Neutrino Observatory : instrumentation and online systems 2017 Ingår i: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221. ; 12 Tidskriftsartikel (refereegranskat)abstract The IceCube Neutrino Observatory is a cubic-kilometer-scale high-energy neutrino detector built into the ice at the South Pole. Construction of IceCube, the largest neutrino detector built to date, was completed in 2011 and enabled the discovery of high-energy astrophysical neutrinos. We describe here the design, production, and calibration of the IceCube digital optical module (DOM), the cable systems, computing hardware, and our methodology for drilling and deployment. We also describe the online triggering and data filtering systems that select candidate neutrino and cosmic ray events for analysis. Due to a rigorous pre-deployment protocol, 98.4% of the DOMs in the deep ice are operating and collecting data. IceCube routinely achieves a detector uptime of 99% by emphasizing software stability and monitoring. Detector operations have been stable since construction was completed, and the detector is expected to operate at least until the end of the next decade.
50.	Andrean, Stefio Y., 1991-, et al. (författare) The ATLAS Fast TracKer system 2021 Ingår i: Journal of Instrumentation. - : Institute of Physics Publishing (IOPP). - 1748-0221. ; 16:7 Tidskriftsartikel (refereegranskat)abstract The ATLAS Fast TracKer (FTK) was designed to provide full tracking for the ATLAS high-level trigger by using pattern recognition based on Associative Memory (AM) chips and fitting in high-speed field programmable gate arrays. The tracks found by the FTK are based on inputs from all modules of the pixel and silicon microstrip trackers. The as-built FTK system and components are described, as is the online software used to control them while running in the ATLAS data acquisition system. Also described is the simulation of the FTK hardware and the optimization of the AM pattern banks. An optimization for long-lived particles with large impact parameter values is included. A test of the FTK system with the data playback facility that allowed the FTK to be commissioned during the shutdown between Run 2 and Run 3 of the LHC is reported. The resulting tracks from part of the FTK system covering a limited eta-phi region of the detector are compared with the output from the FTK simulation. It is shown that FTK performance is in good agreement with the simulation.

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