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The design of an angular array of electron time-of-flight (eToF) spectrometers is reported, intended for non-invasive spectral, temporal, and polarization characterization of single shots of high-repetition rate, quasi-continuous, short-wavelength free-electron lasers (FELs) such as the LCLS II at SLAC. This array also enables angle-resolved, high-resolution eToF spectroscopy to address a variety of scientific questions on ultrafast and nonlinear light–matter interactions at FELs. The presented device is specifically designed for the time-resolved atomic, molecular and optical science endstation (TMO) at LCLS II. In its final version, the spectrometer comprises up to 20 eToF spectrometers aligned to collect electrons from the interaction point, which is defined by the intersection of the incoming FEL radiation and a gaseous target. The full composition involves 16 spectrometers forming a circular equiangular array in the plane normal to the X-ray propagation and four spectrometers at 54.7° angle relative to the principle linear X-ray polarization axis with orientations in the forward and backward direction of the light propagation. The spectrometers are capable of independent and minimally chromatic electrostatic lensing and retardation, in order to enable simultaneous angle-resolved photo- and Auger–Meitner electron spectroscopy with high energy resolution. They are designed to ensure an energy resolution of 0.25 eV across an energy window of up to 75 eV, which can be individually centered via the adjustable retardation to cover the full range of electron kinetic energies relevant to soft X-ray methods, 0–2 keV. The full spectrometer array will enable non-invasive and online spectral-polarimetry measurements, polarization-sensitive attoclock spectroscopy for characterizing the full time–energy structure of SASE or seeded LCLS II pulses, and support emerging trends in molecular-frame spectroscopy measurements.

Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E telescope technology, and a deep dielectric charging monitor (DDCM). The MES measures the energy spectra of 50−600 keV electrons from nine directions with a 180°×30° field of view (FOV). The HED measures the energy spectrum of 0.5−3.0 MeV electrons from one direction with a 30° cone-angle FOV. The ground test and calibration results indicate that these three sensors exhibit excellent performance. Preliminary observations show that the electron spectra measured by the MES and HED are in good agreement with the results from the magnetic electron-ion spectrometer (MagEIS) of the Van Allen Probes spacecraft, with an average relative deviation of 27.3% for the energy spectra. The charging currents and voltages measured by the DDCM during storms are consistent with the high-energy electron observations of the HED, demonstrating the effectiveness of the DDCM. The observations of the EEDP on board the three MEO satellites can provide important support for theoretical research on the radiation belts and the applications related to space weather.

Bu çalışmada, elektron spektrometresi kullanılarak, Helyum (He) atomunun rezonans düzeylerinin açısal değişimleri ölçülmüştür. 200 eV enerjili elektron demeti, yüksek vakum ortamında He atomları ile çarpıştırılarak koparılan ve saçılan elektronlar dedekte edilmiştir. Elektron spektrometresi deney düzeneği; vakum sistemi, elektron tabancası, hedef gaz He, saçılan ve koparılan elektronları dedekte eden iki elektron enerji analizörü, elektron dedektörleri, sinyal işleme ünitesi ve Faraday Elektron Toplayıcıdan (FET) oluşmaktadır. Bu çalışmada, soygaz element serisinde olan Helyum atomunun kendiliğinden iyonlaşma enerji seviyeleri 10o-80o açı aralığında incelenmiştir. Enerji değerleri 32,5-35 eV olarak alınmıştır. Küçük açılarda rezonans profillerinin simetri durumlarının daha baskın olduğu görülürken, büyük açılara doğru kayıldıkça hem simetrik hem asimetrik yapıda oldukları görülmüştür., In this work, the angular variations of the He atom for the resonance levels were experimentally measured by electron spectrometer. 200 eV energetic electron beam collided with Helium (He) gas in high vacuum and scattered electrons were detected. Measurements were taken for angular variation for fixed incident electron energy. The experimental setup in the electron collision laboratory consists of an electron gun, as target He atom, two electron energy analyzers, electron detectors, signal processing units and Faraday Electron Cup (FEC). Here, the auto ionization energy levels of the He atom (in the rare gas element series) for 10o-800 angular range were examined. Differential cross section measurements (DCS) of resonance energy levels were inspected for 32,5-35 eV. Although the symmetry states of resonance profiles are more dominant in the small angle range, both symmetrical and asymmetrical structures are observed for larger angles.

We present multi-period modulation of energetic electron flux observed by the BeiDa Imaging Electron Spectrometer (BD-IES) on board a Chinese navigation satellite on 13 October 2015. Electron flux oscillations were observed at a dominant period of ∼190 s in consecutive energy channels from ∼50 to ∼200 keV. Interestingly, flux modulations at a secondary period of ∼400 s were also unambiguously observed. The oscillating signals at different energy channels were observed in sequence, with a time delay of up to ∼900 s. This time delay far exceeds the oscillating periods, by which we speculate that the modulations were caused by localized ultra-low-frequency (ULF) waves. To verify the wave–particle interaction scenario, we revisit the classic drift-resonance theory. We adopt the calculation method therein to derive the electron energy change in a multi-period ULF wave field. Then, based on the modeled energy change, we construct the flux variations to be observed by a virtual spacecraft. The predicted particle signatures well agree with the BD-IES observations. We demonstrate that the particle energy change might be underestimated in the conventional theories, as the Betatron acceleration induced by the curl of the wave electric field was often omitted. In addition, we show that azimuthally localized waves would notably extend the energy width of the resonance peak, whereas the drift-resonance interaction is only efficient for particles at the resonant energy in the original theory.

The principles and results of the development of an electron spectrometer for a facility for the laser acceleration of electrons, which is being created at the Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, jointly with the Institute of Nuclear Physics (BINP), Siberian Branch, Russian Academy of Sciences, are described. The spectrometer uses a permanent dipole magnet and a phosphor screen and is designed for an energy range of 15–150 MeV. The main requirements that determine the features of this spectrometer are as follows: the location of the basic elements in a vacuum chamber of limited volume and operation in the mode of single pulses at small charges in a pulse, at a level of 1–10 pC. Methods for selecting the measurement scheme and geometry and the requirements for the elements that constitute the spectrometer and their selection are described. It is demonstrated that the beam collimation at the spectrometer entrance allows achievement of an energy resolution of up to 5% at the high-energy limit of the measurement range. The results of testing a spectrometer prototype on the VEPP-5 beam at the BINP, at which the sensitivity of registering the charge density at a level of 0.01 pC/mm2 was experimentally achieved, are presented.

The RELEC scientific instrumentation onboard the Vernov spacecraft launched on July 8, 2014, included the DRGE gamma-ray and electron spectrometer. This instrument incorporates a set of scintillation phoswich detectors, including four identical X-ray and gamma-ray detectors in the energy range from 10 keV to 3 MeV with a total area of $\sim$500 $cm^{2}$ directed toward the nadir, and an electron spectrometer containing three mutually orthogonal detector units with a geometry factor of $\sim$2 $cm^{2} sr$, which is also sensitive to X-rays and gamma-rays. The goal of the space experiment with the DRGE instrument was to investigate phenomena with fast temporal variability, in particular, terrestrial gamma-ray flashes (TGFs) and magnetospheric electron precipitations. However, the detectors of the DRGE instrument could record cosmic gamma-ray bursts (GRBs) and allowed one not only to perform a detailed analysis of the gamma-ray variability but also to compare the time profiles with the measurements made by other instruments of the RELEC scientific instrumentation (the detectors of optical and ultraviolet flashes, the radio-frequency and low-frequency analyzers of electromagnetic field parameters). We present the results of our observations of cosmic GRB 141011A and GRB 141104A, compare the parameters obtained in the GBM/Fermi and KONUSWind experiments, and estimate the redshifts and Eiso for the sources of these GRBs. The detectability of GRBs and good agreement between the independent estimates of their parameters obtained in various experiments are an important factor of the successful operation of similar detectors onboard the Lomonosov spacecraft., 19 pages, 8 figures

Understanding of generation and characterization of fast electrons generated in high-intensity, short-pulse laser-target interaction is important for the development of broadband x-ray sources, creation of high energy density plasma and advanced inertial confinement fusion concepts. We have characterized short-pulse laser produced fast electrons by modeling angularly resolved bremsstrahlung with 3D simulations using a hybrid particle-in-cell code, Large Scale Plasmas (LSP). The experiment was performed at UNR using a 50 TW Leopard laser delivering a 15J, 0.35 ps pulse at a peak intensity of 2×10 19 W/cm 2 . The interaction of the laser pulse with a metal foil generates relativistic electrons predominantly by the ponderomotive potential. Subsequently, the transport of the electrons produces angular dependent bremsstrahlung and high energy electrons escape from the target rear. Bremsstrahlung photons and escaped electrons were recorded with two absolutely calibrated differential filter stack spectrometers and a magnet-based electron spectrometer, respectively. The bremsstrahlung measurements were then modeled with 3-D LSP simulations by varying input electron spectrum (T hot ), divergence angle (θ) and electron beam energy (E hot ). Ranges of the electron characteristics for the Leopard laser are deduced by using a chi-square fitting and the electron spectrum measurements. For a 100 μm thick Cu target, the input fast electron parameters are estimated to be T hot =1.0-1.5MeV, θ=~70o and E hot =0.8-1.5J. The slope temperature inferred from the analysis of the bremsstrahlung agrees with the direct electron measurement. The estimated electron beam energy corresponds to a conversion efficiency of 5.3-10% from the laser to electrons producing the bremsstrahlung. To test the validity of the inferred electron parameters, modeling of bremsstrahlung data for a 100 μm Cu foil attached on a CH backing is underway. Details of the analysis method and a comparison of inferred electron information for the two target types with and without strong electron recirculation will be presented at the conference.

An Ultrafast Electron Diffraction (UED) based on an RF photocathode electron gun has the advantage of producing MeV relativistic probing electron beams, which can maintain a high time resolution of ~100 fs while keeping more electrons to improve the S/R ratio of the image. However, the jitter of driving RF power in the electron gun between pulse to pulse has an indispensable impact on the electron energy stability leading to the Time of Flight (ToF) jitter, which creates asynchronization between the pump laser and the probing electron worsening the time resolution. To stabilize the beam energy to the designed value 3 MeV and reduce the ToF jitter further, we propose controlling the electron energy based on an energy spectrometer directly. An electron spectrometer based on a C-type dipole is being designed to achieve high energy resolution. This paper will introduce the design of the energy spectrometer, and particle tracking is implemented to demonstrate the feasibility of the design.

Multi-electron−ion coincidence spectroscopy is applied for investigating metastability of the dication states formed by the S 2p Auger decay in OCS. The coincidence spectrometer developed in the present work is based on a magnetic-bottle time-of-flight electron spectrometer equipped with electrostatic retardation and ion detection capabilities. Dication spectroscopy with a fairly-high energy resolution and high statistics enables us to inspect the metastability of the individual electronic states in OCS2+.

We describe a magnetic bottle time-of-flight electron spectrometer designed for time-resolved photoemission spectroscopy of a liquid microjet using extreme UV and X-ray radiation. The spectrometer can be easily reconfigured depending on experimental requirements and the energy range of interest. To improve the energy resolution at high electron kinetic energy, a retarding potential can be applied either via a stack of electrodes or retarding mesh grids, and a flight-tube extension can be attached to increase the flight time. A gated electron detector was developed to reject intense parasitic signal from light scattered off the surface of the cylindrically shaped liquid microjet. This detector features a two-stage multiplication with a microchannel plate plus a fast-response scintillator followed by an image-intensified photon detector. The performance of the spectrometer was tested at SPring-8 and SACLA, and time-resolved photoelectron spectra were measured for an ultrafast charge transfer to solvent reaction in an aqueous NaI solution with a 200 nm UV pump pulses from a table-top ultrafast laser and the 5.5 keV hard X-ray probe pulses from SACLA.

The blooming of attosecond science (1 as = $10^{-18}$ s) has raised the need to exquisitely control the delay between two ultrashort light pulses, one of them being intense and in the visible spectral range, while the second is weak and in the Extreme Ultra-Violet spectral range. Here we introduce a robust technique, named LIZARD (Laser-dressed IoniZation for the Adjustment of the pump-pRobe Delay), allowing an active stabilization of this pump-probe delay. The originality of the method lies in an error signal calculated from a two-photon photoelectron signal obtained by photoionizing a gas target in an electronic spectrometer with the two superimposed beams. The modulation of sidebands in phase quadrature allows us to perform an \textit{in situ} measurement of the pump-probe phase, and to compensate for fluctuations with an uniform noise sensitivity over a large range of delays. Despite an interferometer length of several meters, we achieved a long term stability of 28 as RMS over hours. This method could be applied to the stabilization of other types of two-color interferometers, provided that one of the propagating beams is capable of photoionizing a target., 10 pages, 8 figures

We report on the status of a users' end-station, MAC: a Multipurpose station for Atomic, molecular and optical sciences and Coherent diffractive imaging, designed for studies of structure and dynamics of matter in the femtosecond time-domain. MAC is located in the E1 experimental hall on the high harmonic generation (HHG) beamline of the ELI Beamlines facility. The extreme ultraviolet beam from the HHG beamline can be used at the MAC end-station together with a synchronized pump beam (which will cover the NIR/Vis/UV or THz range) for time-resolved experiments on different samples. Sample delivery systems at the MAC end-station include a molecular beam, a source for pure or doped clusters, ultrathin cylindrical or flat liquid jets, and focused beams of substrate-free nanoparticles produced by an electrospray or a gas dynamic virtual nozzle combined with an aerodynamic lens stack. We further present the available detectors: electron/ion time-of-flight and velocity map imaging spectrometers and an X-ray camera, and discuss future upgrades: a magnetic bottle electron spectrometer, production of doped nanodroplets and the planned developments of beam capabilities at the MAC end-station., Comment: 14 pages, 13 figures. This is a preprint of an article published in The European Physical Journal Special Topics, 2021

The Cluster mission has produced a large data set of electron flux measurements in the Earth's magnetosphere since its launch in late 2000. Electron fluxes are measured using Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector as a function of energy, pitch angle, spacecraft position, and time. However, no adiabatic invariants have been calculated for Cluster so far. In this paper we present a step-by-step guide to calculations of adiabatic invariants and conversion of the electron flux to phase space density (PSD) in these coordinates. The electron flux is measured in two RAPID/IES energy channels providing pitch angle distribution at energies 39.2-50.5 and 68.1-94.5 keV in nominal mode since 2004. A fitting method allows to expand the conversion of the differential fluxes to the range from 40 to 150 keV. Best data coverage for phase space density in adiabatic invariant coordinates can be obtained for values of second adiabatic invariant, K, similar to 10(2), and values of the first adiabatic invariant mu in the range approximate to 5-20 MeV/G. Furthermore, we describe the production of a new data product "LSTAR," equivalent to the third adiabatic invariant, available through the Cluster Science Archive for years 2001-2018 with 1-min resolution. The produced data set adds to the availability of observations in Earth's radiation belts region and can be used for long-term statistical purposes., Zweitver��ffentlichungen der Universit��t Potsdam : Mathematisch-Naturwissenschaftliche Reihe; 1192

In space environment, the charge will be collected on the surface of the spacecraft by the combination of the surrounding space plasma and photoelectric effect, forming a suspension potential different from the background plasma environment, that is, the surface charging phenomenon. The integrated monitoring system of plasma environment and surface charging includes 4 parts: omnidirectional electron spectrometer, omnidirectional ion spectrometer, surface potential probe and magnetometer. The main function is to detect the space plasma environment and the surface potential on the satellite, and to process, store and transmit the received signals. Ground testing and calibration have been done for all the four detectors, and the results agree well with the designed value.

We report an electron scattering experiment on argon gas where a keV electron beam is used as a probe and electrons are collected with a magnetic bottle spectrometer. For this purpose, we have built a thermionic gun that produces electron pulses with nanosecond duration by sweeping the beam across a small aperture. To reach the target, electrons must pass through the hole in an axially symmetric arrangement of strong permanent magnets required to operate the magnetic bottle. From the recorded multi-hit sequence of electron arrival times on the microchannel plate detector, a kinetic energy spectrum is built that allows an analysis of the elastic and inelastic electron scattering channels by means of the coincidence technique. After a description of the instrumental configuration and discussion of suitable working parameters, the results of an angle-integrated (e, 2e) experiment are presented for 800 eV electron scattering on argon atoms.

An overview of the gas-phase endstation with the multi-coincidence setup at the FinEstBeAMS beamline in the MAX IV 1.5 GeV storage ring is presented. A detailed description of the functional design of the endstation together with the data acquisition concept and first test measurements is given., Since spring 2019 ▸ an experimental setup consisting of an electron spectrometer and an ion time-of-flight mass spectrometer for diluted samples has been available for users at the FinEstBeAMS beamline of the MAX IV Laboratory in Lund, Sweden. The setup enables users to study the interaction of atoms, molecules, (molecular) microclusters and nanoparticles with short-wavelength (vacuum ultraviolet and X-ray) synchrotron radiation and to follow the electron and nuclear dynamics induced by this interaction. Test measurements of N2 and thiophene (C4H4S) molecules have demonstrated that the setup can be used for many-particle coincidence spectroscopy. The measurements of the Ar 3p photoelectron spectra by linear horizontal and vertical polarization show that angle-resolved experiments can also be performed. The possibility to compare the electron spectroscopic results of diluted samples with solid targets in the case of Co2O3 and Fe2O3 at the Co and Fe L 2,3-absorption edges in the same experimental session is also demonstrated. Because the photon energy range of the FinEstBeAMS beamline extends from 4.4 eV up to 1000 eV, electron, ion and coincidence spectroscopy studies can be executed in a very broad photon energy range.

We report experimental results on relativistic electron beam (REB) transport in a set of cold and shock-heated carbon samples using the high-intensity kilojoule-class OMEGA EP laser. The REB energy distribution and transport were diagnosed using an electron spectrometer and x-ray fluorescence measurements from a Cu tracer buried at the rear side of the samples. The measured rear REB density shows brighter and narrower signals when the targets were shock-heated. Hybrid PIC simulations using advanced resistivity models in the target warm-dense-matter (WDM) conditions confirm this observation. We show that the resistivity response of the media, which governs the self-generated resistive fields, is of paramount importance to understand and correctly predict the REB transport.

Background : Autoionization is an indirect ionization process that significantly increases the total ionization cross section of the atom. Measurements of electron autoionizing spectra in a broad range of impact energies and the determination of their total intensity allow obtaining the absolute value of the autoionization contribution (the autoionization cross section) and its energy behavior. Methods : The study of the ejected-electron spectra of strontium atoms were carried out by using an electron spectrometer. It consists of a source of the incident electron beam, an electron energy analyzer (of 127° electrostatic type deflector) and an atomic beam source. To minimize the influence of the anisotropy of the angular distribution of ejected electrons, the measurements were carried out at a "magic" observation angle of 54.7°. The incident and ejected-electron energy resolutions were about 0.4 eV and 0.07 eV, respectively. The increment step of the incident electron energy was 0.1 eV in the near-threshold energy region. The autoionization cross section was determined as the normalized sum of total intensities of ejected-electron spectra measured at different impact energies. Results : Autoionization cross section for 4p 6 shell of strontium atoms was determined in an incident-electron energy range from the lowest autoionization threshold (20,98 eV) up to 600 eV. Energy behavior of the cross section is characterized by the presence of the strong resonance structure in the threshold region of 21-30 eV and a broad maximum at approximately 100 eV. Cross section reaches its maximum value of 1.6×10 -16 сm 2 at 24.8 eV. We analyze the excitation and decay processes of the 4p 5 n 1 l 1 n 2 l 2 n 3 l 3 autoionizing states. They determine the magnitude and the energy behavior of the autoionization cross section. Conclusions : The strong resonant excitation of the levels in 4p 5 4d5s 2 , 4p 5 4d 2 5s, and 4p 5 5s 2 5p configurations determines the resonant behavior of the measured autoionization cross section at low impact energies. Shape and magnitude of the cross section at high impact energies are determined by the total contribution from dipole-allowed and singlets autoionizing levels in the configurations 4p 5 4d5s 2 , 4p 5 4d 2 5s.

The KLL Auger electron spectra of Zr (Z = 40) and Nb (Z = 41) following respectively the electron capture (EC) decay of 90Nb and the de-excitation of the isomeric state of 91mNb were investigated in detail using a combined electrostatic electron spectrometer and radioactive sources prepared by surface sorption on a polycrystalline carbon substrate. For both elements, energies, relative intensities, and natural widths of all the nine well-resolved basic spectrum components were determined and compared with theoretical predictions and with results of previous measurement as well. Results of our ab initio multiconfiguration Dirac-Hartree-Fock calculations are discussed also in relation to the solid-state effect. Indications of an influence of the EC decay on the absolute energy of the KL2L3(1D2) transition (so-called atomic structure effect) in Zr were found. The effect of the retarded current-current interaction on the KL1L2(3P0) transition intensity was observed to be appreciable for the investigated elements in accordance with the prediction.

Using a hypocycloidal electron spectrometer, the total scattering cross section of slow (0–9 eV) electrons and the dissociative electron attachment cross section for thymine molecules in the gas phase were measured. The ionization cross section for a thymine molecule was studied in the energy range of 9–32 eV. Some features were found in the scattering cross section, caused by the formation and decay of short-lived states of the molecular negative ion. Three of them (E = 0.32, 1.71, and 4.03 eV) relate to shape resonances; the others, which are observed for the first time, refer to the Feshbach resonances (or core-excited resonances). In the total dissociative attachment cross section in the energy range of E < 4 eV, a clear structure is observed due to the formation of a negative ion (T–H)–, and a less intense structure associated with the total contribution of fragment thymine ions is found above 4 eV. The correlation of the features found in the total scattering cross section and in the dissociative attachment cross section is assessed. The absolute total scattering cross section was obtained by normalizing the measured curve to the theoretical calculation. In the total ionization cross section, features are observed that are associated both with the effect of the formation of fr-agment ions and with ionization due to the ejection of electrons from the orbitals of the outer shell of the molecule.