Energy Loss Of Particles Research Articles

Using high-energy neutrinos as cosmic magnetometers

Magnetic fields are crucial in shaping the non-thermal emission of the TeV-PeV neutrinos of astrophysical origin seen by the IceCube neutrino telescope. The sources of these neutrinos are unknown, but if they harbor a strong magnetic field, then the synchrotron energy losses of the neutrino parent particles---protons, pions, and muons---leave characteristic imprints on the neutrino energy distribution and its flavor composition. We use high-energy neutrinos as "cosmic magnetometers" to constrain the identity of their sources by placing limits on the strength of the magnetic field in them. We look for evidence of synchrotron losses in public IceCube data: 6 years of High Energy Starting Events (HESE) and 2 years of Medium Energy Starting Events (MESE). In the absence of evidence, we place an upper limit of 10 kG-10 MG (95% C.L.) on the average magnetic field strength of the sources.

Spatially and Time-Resolved Investigation of Lithium Plating on a Graphite Electrode during Fast Charging Using Operando Neutron Depth Profiling (NDP)

Apart from increasing the battery size of electric vehicles (EVs), another approach to reduce range anxiety and to achieve mass market penetration is to increase the charging power and thus significantly lower charging times. To date, commercial lithium-ion battery (LIB) cells are almost exclusively based on graphite as anode material.[1] Here, owing to the low potential of the graphite electrode during charge, the charging rate must be limited in order to avoid lithium plating, which can thermodynamically occur in regions of the electrode where the potential drops below 0 V vs. Li+/Li. Plated lithium is very reactive, leading to irreversible reactions with the electrolyte and therefore strongly reduces lifetime and safety of a battery.[2] Studying lithium plating in a battery cell is very challenging since post-mortem diagnostics do not reflect the electrode state during operation, since plated lithium will reintercalate into the active graphite material on a timescale of minutes at room temperature.[3] , [4] Hence, non-destructive operando techniques[5] , [6] are necessary to elucidate and follow lithium plating mechanisms in an operating cell.In this study, we present data collected via Neutron Depth Profiling (NDP) during lithium plating induced by fast charging of a graphite electrode at a rate of 2 C. NDP is a lithium-sensitive, non-destructive technique utilizing the neutron capture reaction of 6Li atoms to quantitatively measure the lithium distribution over the thickness of an electrode by probing the energy loss of charged particles formed by the neutron capture reaction.[7] We employ a recently developed operando NDP cell that shows a cycling performance comparable to a commercial cell even at high charging rates, and at the same time allows charged particles to exit the cell through a thin Kapton® window.[8] We were able to resolve the lithium depth distribution changes during the open circuit voltage (OCV) phase after a constant current charge with a time resolution of 2 min. This exceptionally high time resolution was achieved by combining the high cold neutron flux of 2.7×109 ncm-2s-1 at the NIST Center for Neutron Research (Washington D.C., USA) with a 6Li enriched electrolyte and a 6LiFePO4 cathode, which enhances the signal by an additional factor of 12. In order to achieve lithium plating already at a rate of 2 C, the LiPF6 salt concentration in the EC/EMC = 3/7 (w/w) electrolyte was reduced to 0.3 M.Figure 1 shows the NDP signal intensity as a function of the energy of the detected tritium particles, which translates into a depth profile: signals at an energy of ≈2400 keV represent lithium at the interface between the graphite electrode and the Cu current collector, and signals at decreasing energies represent lithium from increasing depth into the graphite electrode, with signals at an energy of ≈800 keV deriving from the graphite anode / separator interface. It is clearly visible that lithium plating starts towards the separator facing side of the graphite anode, caused by the lithium-ion concentration gradient forming over the thickness of the electrode during fast charging (dark blue profile); during the subsequent OCV phase, lithium re-distributes over the anode thickness, whereby this equilibration process is observed to be completed within ≈24 min.[1] C. Pillot, “The Rechargeable Battery Market and Main Trends 2014-2025”, 32nd International Battery Seminar and Exhibit, 3/9/2015, Presentation.[2] J. C. Burns, D. A. Stevens, J. R. Dahn, J. Electrochem. Soc. 2015, 162, A959.[3] Z. Y. Tang, J. J. Xue, C. Y. Liu, X. G. Zhuang, Acta Phys. - Chim. Sin. 2001, 17, 388.[4] M. Park, X. Zhang, M. Chung, G. B. Less, A. M. Sastry, J. Power Sources 2010, 195, 7904.[5] J. Wandt, P. Jakes, J. Granwehr, R. A. Eichel, H. A. Gasteiger, Mater. Today 2018, 21, 231.[6] R. Bhattacharyya, B. Key, H. Chen, A. S. Best, A. F. Hollenkamp, C. P. Grey, Nat. Mater. 2010, 9, 504.[7] M. Trunk, M. Wetjen, L. Werner, R. Gernhäuser, B. Märkisch, Z. Révay, H. A. Gasteiger, R. Gilles, Mater. Charact. 2018, 146, 127.[8] F. Linsenmann et al., A Lithium-Ion Battery Cell Design for Operando Neutron Depth Profiling, to be submitted. Figure 1

Unified description of interactions and energy loss of particles in dense matter and plasmas

In this paper, the authors present a unified approach to describe the interaction of charged particles with matter that applies to a very broad range of values of densities, temperatures, and ionization state. It can be used for applications to processes in ionized matter under extreme conditions of densities and temperatures, such as found, e.g., in fusion or astrophysical plasmas.

Mitigation of the Stopping Power Effect on Proton-Boron11 Nuclear Fusion Chain Reactions

A proton beam with a velocity of the order of 10^9 cm/s is generated to interact with a charge neutral hydrogen-boron medium such as H3B. The created charged particles are confined by magnetic fields. This concept was the basis for a novel non-thermal fusion reactor, published recently in Laser and Particle Beams [1]. The fusion is initiated by protons followed by a process of chain reactions in a neutral medium density of the order of 10^19 cm-3, heated by the pB11 fusion created alphas up to a temperature of about one electron volt. In this system, the radiation losses by bremsstrahlung are negligible and the plasma thermal pressure is low. The ionization of the gaseous medium is caused by the alpha elastic nuclear collisions with the hydrogen atoms and their thermal heating and it is less than 10^-4. An external electric field is applied to avoid the energy losses of the protons particles by friction, due to their interaction with the electrons of the medium, to keep the proton-boron fusion at the maximum cross section of about 600 keV at the center of mass frame of reference. The alphas created in the pB11 fusion undergo nuclear elastic collisions with the hydrogen protons of the medium and causing a pB11 chain reaction. In this paper the equation of motion of these proton and alphas are solved numerically for the one-dimensional (1D) case, and their possible solutions are analyzed and discussed. Specifically, it is shown how the electric field can mitigate the stopping power for the proton11-proton nuclear fusion. Our results show that starting from a bunch of 1013 protons in our volume, an alpha number of particles of 6×10^16 was accepted after a 5ms cycle of applying our specially designed electric field. Consequently, the medium temperature was raised to 1.3 eV. Although the aim of this paper is to present a new concept by addressing only the main physical processes and not to present a complete engineering design for a power plant, our numerical solution is novel and promises a viable proton-boron11 fusion reactor for clean energy creation.

Measurement of the Cross Section for the Process $$\boldsymbol{e^{+}e^{-}\to K^{+}K^{-}}$$ with the CMD-3 Detector

Preliminary results of measurement of the cross section for the process $$e^{+}e^{-}\to K^{+}K^{-}$$ in the range of c.m. energies between 1.075 and 1.975 GeV are presented. An analysis was performed on the basis of an integrated luminosity of 62.9 pb $${}^{-1}$$ accumulated by employing the CMD-3 detector within the experimental runs of 2019. The suppression of the background from the processes $$e^{+}e^{-}\to e^{+}e^{-}(\gamma)$$ , $$\mu^{+}\mu^{-}(\gamma)$$ , and $$\pi^{+}\pi^{-}(\gamma)$$ and the background of cosmic-ray muons was accomplished with the aid of information about specific energy losses of charged particles in the layers of the liquid xenon calorimeter of the CMD-3 detector. The preliminary results of the present measurement of the $$e^{+}e^{-}\to K^{+}K^{-}$$ cross section are in reasonable agreement with the results of earlier measurements and have a commensurate statistical precision.

Development and calibration of a method for direct measurement of 220Rn (thoron) activity concentration

The interest in the measurement of thoron (220Rn) activity concentration in air has recently increased, with the attention for the development of standards useful for the calibration of measuring instruments. Due to its short half-life (55.8 s), consolidated techniques for the realization and the use of controlled atmospheres of radon (222Rn) are not effective in the case of thoron. New adequate methodology are required. A method for the measurement of the thoron reference activity based on the direct detection of the alpha particles produced by the decay of 220Rn, from natural samples containing 232Th, is here proposed. The possibility of observing an acceptable spectrum is entrusted to the realization of measurement chambers small enough to reduce as much as possible the energy loss of the alpha particles before they reach the Silicon detector. Such a chamber was realized and used with a known thoron atmosphere in a controlled environment. The experimental results are compared with those obtained from the simulation with the Monte Carlo method: (i) the alpha spectra coming directly from thoron atoms exhibit similar shape with a linear trend plus an exponential trend on the left side of the 220Rn peak, depending from the distance between source and detector; (ii) the corresponding 220Rn detection efficiency values are compatible considering the uncertainties. An investigation was conducted to study the shape of the 220Rn spectra vs the different volume of chambers, through Monte Carlo simulations. The results show: (i) the linear part of the spectra shape goes to reduce with the increasing of the height of the chamber; (ii) the 220Rn detection efficiency decreases with the increasing of the height of the chamber.

Spatially and Time-Resolved Investigation of Lithium Plating on a Graphite Electrode during Fast Charging Using Operando Neutron Depth Profiling (NDP)

Apart from increasing the battery size of electric vehicles (EVs), another approach to reduce range anxiety and to achieve mass market penetration is to increase the charging power and thus significantly lower charging times. To date, commercial lithium-ion battery (LIB) cells are almost exclusively based on graphite as anode material.[1] Here, owing to the low potential of the graphite electrode during charge, the charging rate must be limited in order to avoid lithium plating, which can thermodynamically occur in regions of the electrode where the potential drops below 0 V vs. Li+/Li. Plated lithium is very reactive, leading to irreversible reactions with the electrolyte and therefore strongly reduces lifetime and safety of a battery.[2] Studying lithium plating in a battery cell is very challenging since post mortem diagnostics do not reflect the electrode state during operation, since plated lithium will reintercalate into the active graphite material on a timescale of minutes at room temperature.[3] , [4] Hence, non-destructive operando techniques[5] , [6] are necessary to elucidate and follow lithium plating mechanisms in an operating cell.In this study, we present data collected via Neutron Depth Profiling (NDP) during lithium plating induced by fast charging of a graphite electrode at a rate of 2 C. NDP is a lithium-sensitive, non-destructive technique utilizing the neutron capture reaction of 6Li atoms to quantitatively measure the lithium distribution over the thickness of an electrode by probing the energy loss of charged particles formed by the neutron capture reaction.[7] We employ a recently developed operando NDP cell that shows a cycling performance comparable to a commercial cell even at high charging rates, and at the same time allows charged particles to exit the cell through a thin Kapton® window.[8] We were able to resolve the lithium depth distribution changes during the open circuit voltage (OCV) phase after a constant current charge with a time resolution of 2 min. This exceptionally high time resolution was achieved by combining the high cold neutron flux of 2.7×109 ncm-2s-1 at the NIST Center for Neutron Research (Washington D.C., USA) with a 6Li enriched electrolyte and a 6LiFePO4 cathode, which enhances the signal by an additional factor of 12. In order to achieve lithium plating already at a rate of 2 C, the LiPF6 salt concentration in the EC/EMC = 3/7 (w/w) electrolyte was reduced to 0.3 M.Figure 1 shows the NDP signal intensity as a function of the energy of the detected tritium particles, which translates into a depth profile: signals at an energy of ca. 2400 keV represent lithium at the interface between the graphite electrode and the Cu current collector, and signals at decreasing energies represent lithium from increasing depth into the graphite electrode, with signals at an energy of ca. 800 keV deriving from the graphite anode / separator interface. It is clearly visible that lithium plating starts towards the separator facing side of the graphite anode, caused by the lithium-ion concentration gradient forming over the thickness of the electrode during fast charging (dark blue profile); during the subsequent OCV phase, lithium re-distributes over the anode thickness, whereby this equilibration process is observed to be completed within ca. 24 min.

Stopping Power of Alpha Particles in Helium Gas

The stopping power and the range of alpha particles emitted from Am-241 source has been investigated in helium gas at different pressures of 0 to 1 bar, using surface barrier silicon detector in the large vacuum chamber. The energy loss has also been obtained at variable distances from 2 to 8 cm. It is observed that as the pressure in a large vacuum chamber increases, the energy loss of the alpha particle decreases. The measured energy loss of alpha particles at lower pressure of 0 bar is less, but at higher pressure of 1 bar is more. As expected from Bethe --- Bloch formula, the stopping power of charged particle in helium gas at different pressure was found to increase significantly when pressure is increased. The measured value of stopping power and range were compared with SRIM and theoretical value. The experimental value of stopping power and range was found to be very close to the SRIM and theoretical value. Then, the measured value of range was compared with experimental using the Bragg --- Kleeman's rule

On the conversion of NDP energy spectra into depth concentration profiles for thin-films all-solid-state batteries

A three-step numerical procedure has been developed, which facilitates the conversion of NDP energy spectra into lithium concentration depth profiles for thin-film Li-ion batteries. The procedure is based on Monte Carlo modeling of the energy loss of charged particles (ions) in the solid media, using the publically available SRIM/TRIM software. For the energy-to-depth conversion, the battery stack has been split into finite volume elements. Each finite volume element becomes a source of ions according to the employed nuclear reaction. Ions loos energy when they move across the battery stack towards the detector. The as-obtained simulated spectra have been compared with the experimentally measured spectra. The thicknesses of the battery stack layers were estimated by minimizing the deviation between the simulated and measured spectra. Subsequently, a relation between the average energy of detected ions and the depth of the corresponding finite volume element, yielding a calibration function, was used to relate that particular part of the spectra with the depth of its source. At the final stage, a Bayesian estimator was used to find the distribution of lithium at a particular depth. The developed procedure was applied to a practically relevant case study of Si immobilization in the LPO electrolyte of all-solid-state thin-film batteries. It is shown that the lithium immobilization process in the LPO electrolyte is responsible for the battery degradation process.

Calibration of the charge and energy loss per unit length of the MicroBooNE liquid argon time projection chamber using muons and protons

We describe a method used to calibrate the position- and time-dependent response of the MicroBooNE liquid argon time projection chamber anode wires to ionization particle energy loss. The method makes use of crossing cosmic-ray muons to partially correct anode wire signals for multiple effects as a function of time and position, including cross-connected TPC wires, space charge effects, electron attachment to impurities, diffusion, and recombination. The overall energy scale is then determined using fully-contained beam-induced muons originating and stopping in the active region of the detector. Using this method, we obtain an absolute energy scale uncertainty of 2% in data. We use stopping protons to further refine the relation between the measured charge and the energy loss for highly-ionizing particles. This data-driven detector calibration improves both the measurement of total deposited energy and particle identification based on energy loss per unit length as a function of residual range. As an example, the proton selection efficiency is increased by 2% after detector calibration.

The Monte Carlo simulation of the Borexino detector

Borexino is a 300 ton sub-MeV liquid scintillator solar neutrino detector which has been running at the Laboratori Nazionali del Gran Sasso (Italy) since 2007. Thanks to its unprecedented radio-purity, it was able to measure the flux of 7Be, 8B, pp, and pep solar neutrinos and to detect geo-neutrinos. A reliable simulation of the detector is an invaluable tool for all Borexino physics analyses. The simulation accounts for the energy loss of particles in all the detector components, the generation of the scintillation photons, their propagation within the liquid scintillator volume, and a detailed simulation of the electronics chain. A novel efficient method for simulating the external background which survives the Borexino passive shield was developed. This technique allows to reliably predict the effect of the contamination in the peripheral construction materials. The techniques developed to simulate the Borexino detector and their level of refinement are of possible interest to the neutrino and dark matter communities, especially for current and future large-volume liquid scintillator experiments.

Production and characterization of thin, self-supporting Si foils for use as targets in radioactive beam experiments

Development of thin, self-supporting silicon foils (both natural and isotopically-enriched) for use as targets in reaction studies with radioactive beams is detailed. Foils with a thickness of ∼220μg/cm2 were produced using vapor deposition and were floated onto aluminum frames with 10–15 mm diameter holes. During their production, the foil thickness was measured using a quartz crystal monitor. Subsequently, the foil thickness was characterized by α particle energy loss measurements and Rutherford backscattering (RBS). These measurements demonstrated that the thickness could be determined to within a 0.5% uncertainty. The elemental purity of the foils was assessed using RBS and X-ray photoelectron spectroscopy. This analysis demonstrated that the foils have 87%–90% silicon abundance.

The background simulation of experiment for searching of 2v2K capture in 124Xe

We describe the Monte Carlo (MC) simulation package of the “2K-CAPTURE” setup and discuss the agreement of its output with data. The “2K-CAPTURE” MC simulates the energy loss of particles in detector and components of the passive shield and generates the resulting response in working volume large proportional counter (LPC). The simulation accounts for absorption, reemission, and scattering of both photons and neutrons and tracks them until they either are absorbed. The algorithm proceeds with a detailed simulation of the electronics chain. The MC is tuned using data collected with radioactive calibration source deployed in the internal channel of the installation. The simulation reproduces the energy response of the detector corresponding to distribution of the generated pointwise clusters of a charge of primary ionization in LPC.

Thermal neutron flux evaluation by a single crystal CVD diamond detector in LHD deuterium experiment

A single crystal CVD diamond detector (SDD) was installed in the torus hall of the Large Helical Device (LHD) to measure neutron during deuterium plasma operation. The LiF foil with 95.62% of 6Li isotope enrichment pasted on the detector was used as the thermal neutron convertor. The energetic ions of 2.0 MeV alpha and 2.7 MeV triton particles generated by the nuclear reaction of neutron with 6Li in LiF foil. Then, energetic ions deposited the energy into diamond, producing a signals in SDD. SDD were exposed to the neutron field in the torus hall of the LHD during the 2nd campaign of the deuterium experiment. The total charge in SDD during one plasma shot in LHD was linearly propotional to the neutron yield over 4 orders of magnitude. The energetic alpha and triton were separately measured by SDD with LiF with the thickness of 1.9 μm, although SDD with LiF with the thickness of 350 μm showed a broadened peak due to the large energy loss of energetic particles generated in the bulk of LiF. The modeling with MCNP and PHITS codes well interpreted the pulse height spectra for SDD with LiF with different thicknesses.

Measurements of radiation quality factor on Mars with the Mars Science Laboratory Radiation Assessment Detector

We report the first long-term measurements of the radiation quality factor of energetic charged particles on the surface of Mars. The Radiation Assessment Detector (RAD) aboard the Mars Science Laboratory rover, also known as Curiosity, has been operating on Mars since 2012. RAD contains thin silicon detectors that record the ionization energy loss of energetic charged particles. The particles are dominantly galactic cosmic rays (GCRs) and the products of their interactions in the Martian atmosphere, with occasional contributions from solar energetic particles (SEPs). The quality factor on the surface of Mars is influenced by two factors: variations in the shielding provided by the atmosphere, and changes in the spectrum of the incident energetic particle flux due to the 11-year solar cycle. The two cannot be easily disentangled using the data alone, but insights can be gained from calculations and Monte Carlo simulations.

In-Situ Measurement of Distribution of Lithium Atoms in Li-Ion Batteries and Their Components Using Thermal Neutron Beam

Nowadays, rechargeable Li-ion batteries are widely used in various devices. The further development of these secondary batteries depends on investigation of new materials for electrodes, electrolyte and interphases. The many physical or electrochemical methods, e.g., x-ray diffraction, x-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), can evaluate or investigate various aspects of these materials. Nevertheless, none of these methods can provide experimental spatial distribution of lithium atoms within full cell, half cell or some prospective materials. This very important information can be supplemented by nondestructive nuclear analytical technique, Neutron Depth Profiling (NDP) [1]. This unique technique is based on irradiation of samples by an intense beam of thermal neutrons and analyzing the energy loss of charged particles following the 6Li(n,α)3T reaction. The high nominal resolving power (depth resolution) of this method, about 10 nm, charge neutrality of neutron beam and high cross section of the capture reaction, 940 b, enable various in-situ measurements in various electrochemical conditions. Beside traditional NDP technique the above mentioned reaction can be exploited for high resolution imaging of 2D distribution of lithium in thin samples [2]. The both method capability for investigation of Li-ion battery samples will be discussed and examples of usage will be presented in this contribution.

Ultrafast InAs Quantum Dot Scintillation Detector

High-efficiency, picosecond scintillation detectors are critically needed for many applications, particularly in the fields of medical imaging, high energy physics and nuclear security. Recently, we proposed a design and considerations for a semiconductor scintillator composed of InAs Quantum Dots (QDs) acting as luminescence centers in a GaAs stopping matrix/waveguide, integrated with a photodetector grown epitaxially on top of the waveguide (WG) [1]. This material has appealing potential photonic properties including high light yield (~240,000 photons/MeV) due to the narrow semiconductor bandgap, fast capture of electrons in QDs (2-5ps) and high radiation hardness (>104 Gy). The high refractive index of GaAs (n=3.4) ensures light emitted by the QDs is waveguided within the GaAs matrix, which can then be collected by an integrated InGaAs p-i-n photodiode (PD). A proof-of-concept integrated scintillation detector (Fig. 1) was grown using molecular beam epitaxy on a GaAs substrate. It has a 20 μm thick GaAs layer with embedded sheets of modulation p-type doped InAs QDs. A generic excitation source is shown interacting with the GaAs matrix, resulting in QD luminescence, which is then waveguided towards an InGaAs PD, grown on top of the WG and tuned to the QD luminescence band (~1150 nm). Employing QD structure engineering improves the internal efficiency of the QD luminescence to ~60% at room temperature and reduces overall waveguide attenuation to about 3-4 cm-1. A sample, as shown in Fig. 1, was used to evaluate the timing characteristics of 5.5 MeV alpha particle responses. The source had a radioactivity of 1 µCi, suspended in air approximately 1 cm above the QD waveguide. The scintillation response (Fig. 2) had a decay time of 0.3 ns, corresponding to QD recombination time, and a noise-limited time resolution of 54 ps (Fig. 3). With a 2D waveguide and an integrated PD covering only 16% of the WG width, the collected charge averaged 1.5x105 electrons (Fig. 4), corresponding to a collection efficiency of about 14%. This can be estimated as 34,000 photoelectrons per 1 MeV of incident energy, given about 1 MeV of alpha particle energy loss in air. This data confirms the unique photonic properties of this scintillation detector, which has the potential to be much faster than any currently used inorganic scintillator. Additionally, technologies for separating an epitaxial film from a substrate and bonding multiple waveguides using organic adhesives are tested and evaluated. [1] S. Oktyabrsky, et al. "Integrated Semiconductor Quantum Dot Scintillation Detector: Ultimate Limit for Speed and Light Yield," IEEE TNS, 63, 656 (2016). Figure 1

Determination of 18F positron range in PET imaging using Monte Carlo simulation - Geant4 code

Objective: To determine the distribution of the positron range of radionuclide 18F using Monte Carlo Simulation. Method: 18F is widely available for routine clinical use. In this work, we perform a theoretical calculation of the distribution of the 18F positron range using Monte Carlo (MC) simulation. To collect a statistically significant sample of distance values between the beta emitter point and the Line Of Response (LOR), approximately50000 tracks in water were generated and propagated until annihilation. The radial cumulative probability distribution G2 D(δ) as a function of was adjusted and the analytical formulae was obtained. Finding: The maximum, mean and 1D values of the positron range for 18F simulated and propagated in water are calculated and compared with other studies. The application of Monte Carlo simulation for positron range calculation emphasizes the adoption of this calculation for the radionuclide properties and their propagated medium. The calculation results of beta particle energy loss are in good agreement with many studies that dealt with the same matter having the same energy range. The bin size, source shape, simulation code and propagation medium are the main parameters responsible on the slight differences in the positron range calculation results. Application: It is well known from most existing studies that PET resolution blurring is coupled to the positron range and that it is important to take this range into account in the image reconstruction process. In this study, we calculated the positron range of 18F in water, which is not an obvious affect and it is related to the values of Emean and Emax of 18F 0.250 MeV and 0.635MeV, respectively. These values will cause positron particles to propagate in the medium with a range not exceeding 2 mm with an FWHM(px) is 0.16 mm and FWTM(px) is 1.05 mm. Keywords: Geant4 Code, Positron Emission Tomography, Positron Range

Time‐dependent simulation of ion stopping: Charge transfer and electronic excitations

The energy loss of charged particles in matter has been studied for many decades, both, analytically and via computer simulations. While the regime of high projectile energies is well understood, low energy stopping in solids is more challenging due to the importance of non‐adiabatic effects and electronic correlations. Here we consider two problems: the charge transfer between substrate and projectile and the role of electronic correlations, specifically formation of doubly occupied lattice sites in the material during the stopping process. The former problem is treated by time‐dependent density functional theory simulations and the latter by non‐equilibrium Green functions.

Charged particle identification using the liquid Xenon calorimeter of the CMD-3 detector

Abstract This paper describes a currently being developed procedure of the charged particle identification for CMD-3 detector, installed at the VEPP-2000 collider. The procedure is based on the application of the boosted decision trees classification method, and uses as input variables the specific energy losses of charged particles in the 14 layers of the liquid Xenon calorimeter. The performance of the procedure is demonstrated by an example of the extraction of events of e + e − → K + K − ( γ ) process in the center of mass energy range from 1.28 to 1.65 GeV.