Measurements Of Low-energy Electrons Research Articles

Detection of low-energy electrons with transition-edge sensors

We present the detection of electrons with kinetic energy in the 100 eV range with transition-edge sensors (TESs). This has been achieved with a (100×100)-μm2 Ti/Au bilayer TES, with a critical temperature of about 84 mK. The electrons are produced directly in the cryostat by an innovative cold source based on field emission from vertically aligned multiwall carbon nanotubes. We obtain a Gaussian energy resolution between 0.8 and 1.8 eV for fully absorbed electrons in the (90–101)eV energy range, which is found to be compatible with the resolution of this same device for photons in the same energy range. This work opens possibilities for high-precision energy measurements of low-energy electrons. Published by the American Physical Society 2024

Michel electron reconstruction using cosmic-ray data from the MicroBooNE LArTPC

The MicroBooNE liquid argon time projection chamber (LArTPC) has been taking data at Fermilab since 2015 collecting, in addition to neutrino beam, cosmic-ray muons. Results are presented on the reconstruction of Michel electrons produced by the decay at rest of cosmic-ray muons. Michel electrons are abundantly produced in the TPC, and given their well known energy spectrum can be used to study MicroBooNE's detector response to low-energy electrons (electrons with energies up to ~ 50 MeV). We describe the fully-automated algorithm developed to reconstruct Michel electrons, with which a sample of ~ 14,000 Michel electron candidates is obtained. Most of this article is dedicated to studying the impact of radiative photons produced by Michel electrons on the accuracy and resolution of their energy measurement. In this energy range, ionization and bremsstrahlung photon production contribute similarly to electron energy loss in argon, leading to a complex electron topology in the TPC. By profiling the performance of the reconstruction algorithm on simulation we show that the ability to identify and include energy deposited by radiative photons leads to a significant improvement in the energy measurement of low-energy electrons. The fractional energy resolution we measure improves from over 30% to ~ 20% when we attempt to include radiative photons in the reconstruction. These studies are relevant to a large number of analyses which aim to study neutrinos by measuring electrons produced by νe interactions over a broad energy range.

How to Really Measure Low Energy Electrons in Space

There is little argument in the space plasma physics community that in-situ, low energy electron measurements are technically challenging. The primary obstacle has been the effects of spacecraft charging on the measured three-dimensional electron velocity space distribution. A successful spacecraft charging correction algorithm used with the three-dimensional electron instrument aboard the Ulysses spacecraft has clarified the role of spacecraft and instrument parameters in the eventual reconstruction of low energy electron distributions. Suggestions for instrument and spacecraft modifications that can minimize spacecraft charging effects are presented in this paper. The emphasis is on designs that lend themselves to robust correction algorithms.

A hitherto unrecognized source of low-energy electrons in water

Most of the low-energy electrons emitted from a material when it is subjected to ionization radiation are believed to be directly ionized secondary electrons. Coincidence measurements of the electrons ejected from water clusters suggests many are produced by a quantitatively new mechanism, known as intermolecular Coulombic decay. Low-energy electrons are the most abundant product of ionizing radiation in condensed matter. The origin of these electrons is most commonly understood to be secondary electrons1 ionized from core or valence levels by incident radiation and slowed by multiple inelastic scattering events. Here, we investigate the production of low-energy electrons in amorphous medium-sized water clusters, which simulate water molecules in an aqueous environment. We identify a hitherto unrecognized extra source of low-energy electrons produced by a non-local autoionization process called intermolecular coulombic decay2 (ICD). The unequivocal signature of this process is observed in coincidence measurements of low-energy electrons and photoelectrons generated from inner-valence states with vacuum-ultraviolet light. As ICD is expected to take place universally in weakly bound aggregates containing light atoms between carbon and neon in the periodic table2,3, these results could have implications for our understanding of ionization damage in living tissues.

The Effect of Depletion Layer Thickness in Avalanche Photodiodes for Measurement of Low-energy Electrons

We have tested APDs (Type spl 3989 and Z7966, Hamamatsu Photonics K.K.) using an electron beam. The Z7966, which has a depletion layer of 10 μ m , is firstly focused on and tested in our former paper [K. Ogasawara, K. Asamura, T. Mukai, Y. Saito, Nucl. Instr. and Meth. A 545(3) (2005) 744] for the energy range of 5–20 keV. The result shows that the pulse height distribution of the APD signal exhibits a significant peak for electrons with energies above 8 keV, and positions of their peaks show a good linearity. The condition of the peak production at energies below 8 keV was attributed to the thickness of the dead layer on the surface of APDs. Now we have tuned up our electron acceleration system up to 40 keV, and tested Z7966 by electrons of higher energies. The result shows that the output pulse height distributions of this Z7966 were distorted over 30 keV. In order to examine the distortion of pulse height distributions, we have made a Monte Carlo numerical simulation of particle transport inside the APD. The result shows that the highest energy limit is expected to be determined by the thickness of the depletion layer inside the APD. Therefore, we have tried an APD type spl 3989, which has a thicker depletion layer ( 30 μ m ) and a thinner dead layer. As is expected, the spl 3989 responded to 2–40 keV electrons with fine peaks in the output pulse height distributions. The energy resolution was lower than 1 keV for 2–20 keV electrons, and 5 keV for 40 keV electrons. The linearity of the response was also good. According to the Monte Carlo simulation, electrons up to about 60 keV are expected to be well detectable.

Avalanche photodiode for measurement of low-energy electrons

We report on the performance of an Avalanche Photodiode (APD) produced by Hamamatsu Photonics Co. Ltd. (Type Z7966-20) for measurements of low energy electrons. We have set up an electron gun, which can generate a 1–20 keV electron beam impinging onto the APD in a vacuum chamber. The result shows that the pulse height distribution (PHD) of the APD signal exhibits a significant peak for electrons with energies above 8 keV, and the variation of the PHD peak shows a good linearity with the energy of incident electrons. The energy resolution is quite good, though it slightly depends on the electron energy. In the case of low-energies (lower than 10 keV), the pulse height distribution has a characteristic tail on the low energy side, and the energy resolution becomes a little worse. The position of the peak appears on a slightly lower channel than is expected from data at higher energies (near 20 keV). Qualitatively, the low-energy tail is caused by the dead-layer on the surface of the device. The nonlinearity and the worse resolution of the peaks for higher energy electrons may have resulted from a space-charge effect due to created e–h pairs. For a quantitative understanding, we have made a Monte Carlo particle simulation of charge transport and collection inside the APD.

Doubly Excited States in Helium Close to the Double Ionization Threshold: Angular and Energy Resolved Partial Cross Sections

This is a report about a novel experiment on double excitation of Helium by absorption of synchrotron radiation close to the double ionization threshold at 79 eV. Partial cross-sections for single-ionization from 78.15 eV up to 78.9 eV (photon energy) with an energy resolution of 3 meV have been measured. The technique described in this article allows for an angular and energy resolved measurement of low energy electrons with a high detection efficiency due to an angular acceptance of 4π solid angle.

Active spacecraft potential control for Cluster – implementation and first results

Abstract. Electrostatic charging of a spacecraft modifies the distribution of electrons and ions before the particles enter the sensors mounted on the spacecraft body. The floating potential of magnetospheric satellites in sunlight very often reaches several tens of volts, making measurements of the cold (several eV) component of the ambient ions impossible. The plasma electron data become contaminated by large fluxes of photoelectrons attracted back into the sensors. The Cluster spacecraft are equipped with emitters of the liquid metal ion source type, producing indium ions at 5 to 9 keV energy at currents of some tens of microampere. This current shifts the equilibrium potential of the spacecraft to moderately positive values. The design and principles of the operation of the instrument for active spacecraft potential control (ASPOC) are presented in detail. Experience with spacecraft potential control from the commissioning phase and the first two months of the operational phase are now available. The instrument is operated with constant ion current for most of the time, but tests have been carried out with varying currents and a "feedback" mode with the instrument EFW, which measures the spacecraft potential . That has been reduced to values according to expectations. In addition, the low energy electron measurements show substantially reduced fluxes of photoelectrons as expected. The flux decrease in photoelectrons returning to the spacecraft, however, occurs at the expense of an enlarged sheath around the spacecraft which causes problems for boom-mounted probes.Key words. Space plasma physics (spacecraft sheaths, wakes, charging); Instruments and techniques; Active perturbation experiments

Plasmon production by the decay of hollow Ne atoms near an Al surface

Measurements of low-energy electrons emitted by 4.5-keV Ne q1 -ion impact on an Al surface are discussed for incident charge states q51 ‐6. Spectral structures found near 11 eV are attributed to the decay of bulk plasmons. A method is given to determine absolute values for the experimental electron yield from the plasmon decay. Absolute plasmon yields are studied as a function of the incidence angle of the projectile and the observation angle of the electron. A cosinelike angular distribution is found for the ejected electrons indicating that the plasmons decay well below the surface. The experimental data are compared with model calculations providing information about the plasmon production mechanisms.

Nuclear targets, recoil ion catchers and reaction chambers

The main features of nuclear targets, recoil ion catchers and reaction chambers used in nuclear spectroscopic investigations involving in-beam multi-e- γ spectrometers are discussed. The relative importance of the δ-ray background due to the accelerated ion–target and the recoil-ion–target interaction is estimated. Its impact on the prompt low-energy electron measurements is stressed. Finally a few general features of the interplay between accelerated ion beams, targets and recoil ion catchers particularly relevant for these measurements are broadly discussed and illustrated with typical examples of in-beam e- γ studies.

Low‐energy electron measurements at Ganymede with the Galileo spacecraft: Probes of the magnetic topology

During the close flyby of Ganymede by the Galileo spacecraft on 6 September 1996 a plasma analyzer was used to obtain comprehensive measurements of the thermal electron plasmas in the vicinity of this moon. Our initial analyses are directed toward the character of energy influxes into Ganymede's polar caps and the pitch angle distributions for warm electrons in the energy range of 70 eV to 4.5 keV. The source of these electrons is Jupiter's plasma sheet within which Ganymede was embedded during the flyby. These electrons were present along the entire trajectory and provide the opportunity to use their pitch angle distributions with respect to the magnetic field in order to investigate the magnetic field topology at Ganymede. Observations of the loss cones for these pitch angle distributions are a simple means of determining whether or not a given magnetic field line intersects the moon's surface. It is found that the observed pitch angle distributions are inconsistent with the current magnetostatic model for the magnetic fields in the vicinity of Ganymede. Thus a major revision of this model is required that accounts for the contributions of the plasma dynamical interaction in order to achieve a more accurate assessment of an intrinsic magnetic moment in the interior of this moon. In addition, the electron energy fluxes into the polar cap at the time of flyby were measured to be about 1 erg/cm²‐s, or a total of approximately 5 × 1016 ergs/s over each polar cap available for excitation and ionization of any atmosphere near the moon's surface.

Type III bursts traced from the solar surface to 1 AU

We trace type III radio bursts from the sun until they can be observed as in situ electrons at the ISEE-3 spacecraft. Our study extends over the period of operation of the electron experiment on ISEE-3 from August 1978 to November 1979. Our observations include data from solar flares, kilometric type III burst spectra from ISEE-3, and in situ measurements of low energy electrons from ISEE-3. By carefully restricting the data sets involved, we find a peak of 20° width in the number of flares associated with in situ electrons near 60° west solar longitude. This peak shows that the electron beams of type III bursts are not spread over a great range of longitudes as earlier studies indicate, but are fairly limited in spatial extent. However, even in that longitude range only 40% of type III-flare events are associated with in situ electrons.

The Plasma Instrument for AMPTE IRM

The AMPTE IRM plasma instrument package consists of three sensors. Two of them measure complete 3-D velocity-distribution functions of ions and electrons every spacecraft revolution (i.e., 4.35 s). The third sensor is a retarding potential analyzer (RPA) for low-energy electron measurements. The 3-D measurements consist of countrates at 30 energies and 128 angles evenly distributed over the 4xr solid-angle sphere. The energy range is 15 eV-30 keV for electrons and 20 eV/q-40 keV/q for ions. The RPA extends the electron measurements to lower energies. Three microcomputers within the experinent perform extensive on-board data-processing functions. Two of them compute the moments (density, velocity, temperature tensor, and heat flux vector) of the distribution functions of ions and electrons in real time. The third compresses the RPA data and computes an indication for the spacecraft potential.

Measurements of low energy electrons and ions during long-lived solar particle events

Following a solar flare in April 1979, a stream of ions and electrons appeared in interplanetary space for about 8 days. The ions follow a classic ESP pattern. Large fluxes of low energy (2–11 keV) electrons are also present throughout the event. Several distinct populations of these electrons can be identified in association with filaments of interplanetary magnetic field. The electron energy spectrum is remarkably well fit by a power law exponent -2.7 during most of the event.

Correlated electric field and low‐energy electron measurements in the low‐altitude polar cusp

Correlated electric field and low‐energy electron measurements are presented for two passes of Hawk‐eye 1 through the south polar cusp at 2000‐km altitude during local morning. In one case the electric field reversal coincides with the boundary of detectable 5.2‐keV electron intensities and the equatorward boundary of the cusp. In the other case the electric field reversal and the 5.2‐keV electron trapping boundary coincide, but the equatorward edge of the cusp as determined from the presence of 180‐eV electron intensities is 5° invariant latitude equatorward of the electric field reversal. We conclude that in the second case, electron intensities associated with the polar cusp populate closed dayside field lines, and hence the corresponding equatorward edge of these electron intensities is not always an indicator of the boundary between closed dayside field lines and polar cap field lines.

Comment on low energy electron measurements in the Jovian magnetosphere

We suggest that the low energy electrons reported by Intriligator and Wolfe (1974) in the outer magnetosphere of Jupiter may actually be photoelectrons and/or secondary electrons from the Pioneer spacecraft surfaces. The electron spectrum is similar to the observed photoelectron spectrum on earth‐orbiting satellites where differentially charged surfaces have deflected the electrons into particle detectors.

Measurement of low-energy electrons in the day airglow and day side auroral zone from Atmosphere Explorer C

The photoelectron spectrometer experiment on Atmosphere Explorer C has obtained high-resolution spectra of the energy distribution of 2- to 500-eV electrons in the thermosphere at altitudes above 155 km. The photoelectron spectrum in the day airglow has been measured in detail over a wide range of altitude, latitude, and local time. Structure observed near 27 eV is assigned to photoelectrons ejected from atomic oxygen by the intense solar He II (304 A) radiation. The photoelectron energy distribution is shown to have a sharp cutoff near 60 eV. In addition to the day airglow data, spectra are also presented showing low-energy (100--500 eV) electron precipitation near the polar boundary of the auroral oval at magnetic local times near 0830. The precipitation is a low-energy inverted ''V'' type event occurring over an extremely narrow range of invariant latitude ($delta$$lambda$ approximately 0.3$sup 0$). The electron stream is about 50 eV wide at the half-maximum intensity points and changes in energy from 100 to 500 eV. Instrument calibration in the laboratory, performance of the experiment in orbit, and plans for further analysis of the large body of data which now exists are discussed in detail. (auth)

Near-simultaneous measurement of low-energy electrons by sounding rocket and satellite

An auroral sounding rocket was launched from Fort Churchill at 0453 UT on April 24, 1968. At the time of the rocket flight, the Vela 3B satellite was passing through the magnetotail plasma sheet at very nearly the same magnetic local time. Electron spectra obtained from experiments on these vehicles are well described by central Maxwell-Boltzmann populations, with indications of a high-energy tail; the satellite spectra also suggest the presence of a low-energy tail. The higher-temperature spectra measured on the rocket may be derived from the satellite spectra by adiabatic compression.

Universal time control of the south polarFlayer during the IGY

A reexamination of south polar F layer data from the International Geophysical Year has been made, and these results were compared with recent satellite measurements of low-energy electrons. The ionospheric data were plotted so that they would show more clearly the dominance of universal time in the control of polar F layer electron densities. This plot of the data also establishes the clear dependence of polar F layer electron densities on corrected geomagnetic latitude. Comparison between the latitudinal dependence of the F layer electron densities and that of the low-energy electron measurements shows close agreement. This agreement suggests that influxes of low-energy electrons into the ionosphere may be responsible for maintaining or enhancing the south polar F layer. Thus, if universal time control of the F layer is due to precipitation of low-energy electron fluxes, one could say that electron precipitation itself must be dependent on universal time. The latitudinal dependence of south polar F layer electron densities indicates that in winter the area of universal time control is restricted to corrected geomagnetic latitudes greater than 50°. Other workers have indicated that in summer universal time control existed at midlatitudes, but only in the South American sector. Present satellite measurements do not support an intrusion of these low-energy electrons down to midlatitudes. Thus, an unknown process confined to this area in summer appears to be operating.

Pioneer 6 plasma measurements in the magnetosheath

Measurements of the magnetosheath plasma made by the MIT plasma experiment during the outbound passage of Pioneer 6 in the dusk meridian (December 16, 1965) are presented and compared with theoretical predictions and other simultaneous experimental measurements for the same region. Though comparison with theory indicates that the plasma flow around the earth agrees in many ways with a gasdynamic model, observed discrepancies in the density ratio across the bow shock and the non-Maxwellian velocity distribution in the magnetosheath warrant further explanation. Proton observations in the magnetosheath next to the bow shock indicate that the non-Maxwellian high-energy tail of the proton velocity distribution may be due in part to an effect that is independent of the main flow. Magnetosphere and magnetosheath low-energy electron measurements indicate a region of anisotropic flux in the magnetosphere near the magnetopause.