Low Energy Particle Detector Research Articles

Observation of Anomalous Electron Fluxes Induced by GRB221009A on CSES-01 Low-energy Charged Particle Detector

High-energy, long gamma-ray bursts (GRBs) can be generated by the core collapse of massive stars at the end of their lives. When they happen in the close-by universe they can be exceptionally bright, as seen from the Earth in the case of the recent, giant, long-lasting GRB221009A. GRB221009A was produced by a collapsing star with a redshift of 0.152: this event was observed by many gamma-ray space experiments, which also detected an extraordinary long gamma-ray afterglow. The exceptionally large fluence of the prompt emission of about 0.013 erg cm−2 illuminated a large geographical region centered on India and including Europe and Asia. We report in this paper the observation of sudden electron flux changes correlated with GRB221009A and measured by the HEPP-L charged particle detector on board the China Seismo-Electromagnetic Satellite, which was orbiting over Europe at the time of the GRB event. The time structure of the observed electron flux closely matches the very distinctive time dependence of the photon flux associated with the main part of the emission at around 13:20 UTC on 2022 October 9. To test the origin of these signals, we set up a simplified simulation of one HEPP-L subdetector: the results of this analysis suggest that the signals observed are mostly due to electrons created within the aluminum collimator surrounding the silicon detector, providing real-time monitoring of the very intense photon fluxes. We discuss the implications of this observation for existing and forthcoming particle detectors on low Earth orbits.

Low energy signatures of nonlocal field theories

The response of inertial particle detectors coupled to a scalar field satisfying nonlocal dynamics described by nonanalytic functions of the d'Alembertian operator $\Box$ is studied. We show that spontaneous emission processes of a low energy particle detector are very sensitive to high-energy nonlocality scales. This allows us to suggest a nuclear physics experiment ($\sim$ MeV energy scales) that outperforms the sensitivity of LHC experiments by many orders of magnitude. This may have implications for the falsifiability of theoretical proposals of quantum gravity.

A geometric factor calculation method based on the isotropic flux assumption

One of the instruments onboard the China Seismic Electromagnetic Satellite (CSES) is the Low Energy Particle Detector (LEPD). The primary objective of LEPD is to provide measurements of the fluxes, energy spectra and pitch angles of 100 keV to 10 MeV electrons and protons from 2 to 50 MeV in the Earth's magnetosphere. The geometric factor is one of the principle parameters of a detector, which converts the physical quantity—count rate to the particle quantity-flux. In this paper, we calculated the geometric factor of LEPD via computer modeling of an isotropic radiation environment. It was first demonstrated that the radiation intensity related should obey a cosine-law, then a general sampling method of generating this distribution via GPS of GEANT4 was explained. Furthermore, combined with flux normalization, a comparison of the geometric factor calculation of a set of 2-layer detectors with different shapes (cylinder, truncated cone and rectangle) was performed. Results show a generally good agreement between simulation and analytical calculations for the cylinder and truncated cone detectors, and the result of the rectangular one, for which there is no accurate analytical formula, is consistent with the previous simulated results by others. As a practical instance of the 2-layer rectangle detector, the geometric factor of LEPD is 10.336±0.036 cm2·sr for 10 MeV proton and 8.211±0.032 cm2·sr for 8 MeV electron.

Design and performance study of the LEPD silicon tracker onboard the CSES satellite

The low energy particle detector (LEPD) is one of the main payloads onboard the China seismic electromagnetic satellite (CSES). The detector is designed to ascertain space electrons (0.1–10 MeV) and protons (2–50 MeV). It has the capability of identifying the electrons and protons, to measure the energy spectrum and the incident angle of the particles. The LEPD is made up of a silicon tracker system, a CsI (Tl) mini-calorimeter, an anti-coincidence system made by plastic scintillator, as well as electronics and a data acquisition system (DAQ). The tracker is also a kind of ΔE-E telescope; it consists of two layers of double-sided silicon strip detectors (DSSD). The signals emerging from the silicon tracker can be read out by two pieces of application specific integrated circuit (ASIC), which also can generate an event trigger for the LEPD. The functions of the DSSD system in the LEPD for charged particles were tested by 241Am @5.486 MeV α particles. The results show that the DSSD system works well, and has high performance to detect charged particles and measure the position of incident particles.

Solar wind plasma interaction with solar probe plus spacecraft

Abstract. 3-D PIC (Particle In Cell) simulations of spacecraft-plasma interactions in the solar wind context of the Solar Probe Plus mission are presented. The SPIS software is used to simulate a simplified probe in the near-Sun environment (at a distance of 0.044 AU or 9.5 RS from the Sun surface). We begin this study with a cross comparison of SPIS with another PIC code, aiming at providing the static potential structure surrounding a spacecraft in a high photoelectron environment. This paper presents then a sensitivity study using generic SPIS capabilities, investigating the role of some physical phenomena and numerical models. It confirms that in the near- sun environment, the Solar Probe Plus spacecraft would rather be negatively charged, despite the high yield of photoemission. This negative potential is explained through the dense sheath of photoelectrons and secondary electrons both emitted with low energies (2–3 eV). Due to this low energy of emission, these particles are not ejected at an infinite distance of the spacecraft and would rather surround it. As involved densities of photoelectrons can reach 106 cm−3 (compared to ambient ions and electrons densities of about 7 × 103 cm−3), those populations affect the surrounding plasma potential generating potential barriers for low energy electrons, leading to high recollection. This charging could interfere with the low energy (up to a few tens of eV) plasma sensors and particle detectors, by biasing the particle distribution functions measured by the instruments. Moreover, if the spacecraft charges to large negative potentials, the problem will be more severe as low energy electrons will not be seen at all. The importance of the modelling requirements in terms of precise prediction of spacecraft potential is also discussed.

Living the Dream [WIE from Around the World

Shouleh Nikzad is a principal member of staff and a technical group supervisor and lead for the Advanced Detector Arrays and Nanosciences Group at NASA's Jet Propulsion Laboratory (JPL). Her research interests include high sensitivity ultraviolet and UV-NIR imaging arrays using silicon and III-nitride materials, low-energy particle detector arrays, photocathodes, quantum dot based devices, and novel detector concepts. In her tenure at JPL, she has initiated, developed, and managed successful detector and device programs including advanced n-channel p-type delta doped CCDs, extension of the CCD response for EUV and low energy particle detection, high-speed delta doped CCD camera, HAD, and human eye-inspired curved focal plane arrays. She has developed UV cameras for novel UV imaging devices and applications and her interests extend into bioapplications, medical imaging, and brain mapping.

Third Space Weather Summit Held for Industry and Government Agencies

The potential for space weather effects has been increasing significantly in recent years. For instance, in 2008 airlines flew about 8000 transpolar flights, which experience greater exposure to space weather than nontranspolar flights. This is up from 368 transpolar flights in 2000, and the number of such flights is expected to continue to grow. Transpolar flights are just one example of the diverse technologies susceptible to space weather effects identified by the National Research Council’s Severe Space Weather Events—Understanding Societal and Economic Impacts: A Workshop Report (2008). To discuss issues related to the increasing need for reliable space weather information, experts from industry and government agencies met at the third summit of the Commercial Space Weather Interest Group (CSWIG) and the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center (SWPC), held 30 April 2009 during Space Weather Week (SWW), in Boulder, Colo. Devrie Intriligator (Carmel Research Center, Inc.) and W. Kent Tobiska (Space Environment Technologies (SET)) cochaired the summit. In opening the session, Intriligator praised SWPC and Thomas Bogdan, its director, for implementing CSWIG’s request for External Space Weather Data Store (E-SWDS), a near–real time operational database electronic communication method between SWPC and external core partner users. Bogdan discussed SWPC priorities, goals, and plans. Bogdan said he anticipates that more stable budgets will enable SWPC to continue hardware modernization, hire and train forecasters, and put the ENLIL model into operation. He noted that SWPC is working with NOAA aviation and other core entities on overlapping concerns involving space weather. David Bouwer (SET), who represented CSWIG during the E-SWDS implementation, praised the SWPC staff, summarized E-SWDS’s advantages, and answered questions about E-SWDS. Intriligator raised CSWIG’s concerns about the quality and availability of data, including data from a possible replacement for the Advanced Composition Explorer (ACE) satellite at Lagrange point L1 and from satellites such as National Polar-orbiting Operational Environmental Satellite System (NPOESS), Geostationary Operational Environmental Satellites (GOES), and Defense Meteorological Satellites Program (DMSP). Intriligator stressed that a rapid launch of an L1 replacement is urgently needed because ACE is unable to return reliable real-time solar wind data during space weather events such as the 2003 Halloween storm (NOAA Technical Memorandum OAR SEC-88, “Halloween space weather storms of 2003”). In addition, other ACE instruments, such as its low-energy particle detectors, have suffered degradation. Many space weather forecasts need ACE and other data as inputs. If the crucial real-time input data are not available, the space weather community may not be able to test and validate forecasting models during the upcoming solar maximum. To address this situation, Bogdan discussed two possible options: buying data from a commercial satellite at L1, and an interagency cooperative launch of Deep Space Climate Observatory (DSCOVR), a satellite that NASA has built but not launched due to funding issues. Bogdan also summarized the National Space Weather Program (NSWP) participation in the Committee for Space Environmental Sensor Mitigation Options (CSESMO) with Office of Science and Technology Policy and Office of Management and Budget staff. Michael Bonadonna (Office of the Federal Coordinator for Meteorology) summarized recent NSWP activities, including updating NSWP, determining the scope of CSESMO activities, and organizing the 2009 Space Weather Enterprise Forum. In addition, Bonadonna discussed the 2006 “Report of the Assessment Committee for the National Space Weather Program”

Interaction of Titan's ionosphere with Saturn's magnetosphere

Titan is the only Moon in the Solar System with a significant permanent atmosphere. Within this nitrogen-methane atmosphere, an ionosphere forms. Titan has no significant magnetic dipole moment, and is usually located inside Saturn's magnetosphere. Atmospheric particles are ionized both by sunlight and by particles from Saturn's magnetosphere, mainly electrons, which reach the top of the atmosphere. So far, the Cassini spacecraft has made over 45 close flybys of Titan, allowing measurements in the ionosphere and the surrounding magnetosphere under different conditions. Here we review how Titan's ionosphere and Saturn's magnetosphere interact, using measurements from Cassini low-energy particle detectors. In particular, we discuss ionization processes and ionospheric photoelectrons, including their effect on ion escape from the ionosphere. We also discuss one of the unexpected discoveries in Titan's ionosphere, the existence of extremely heavy negative ions up to 10000amu at 950km altitude.

Low Energy Particle Detector Using a Superconducting Transition Edge Sensor

Precise measurement of neutron beta decay tests predictions of the Standard Model of electroweak interaction. The coefficient a of the antineutrino/electron angular correlation is determined by measuring the energy spectrum of the recoil protons generated in the neutron beta decay. A proton spectrometer required for this measurement demands high detection efficiency, high energy resolution and a large detection area. We have begun development of a transition edge sensor (TES) microcalorimeter for use as a low energy particle detector. To realize the large detection area we have designed a pixelated TES array incorporating a parallel biasing scheme. Our TES device consists of 4-pixels using a Au/Ti/Au trilayer film adjusted to a superconducting transition temperature of Tc ~ 380 mK. This temperature is convenient for use in a 3He cryostat with a pulse tube refrigerator. The Au films improve thermal conductivity, thereby reducing position dependent effects and allow an increased detector area.

Latitudinal and longitudinal displacement of cusp ion precipitation controlled by IMF By and Bz

Abstract Dependence of the location of the cusp precipitation on the orientation of interplanetary magnetic field (IMF) is investigated using data from the Akebono satellite taken at altitudes of several thousands of km. More than a hundred cusp precipitation events have been identified with the low-energy particle detector (LEP) onboard Akebono. The observed energy spectra of ions precipitating at the cusp are dispersed by the convection motion of field lines. We pay special attention to the location where precipitating ions have the highest energy in the energy dispersion curve as recorded along the satellite’s path; such location would represent the one nearest to the foot point of the dayside reconnection line (we here assume that the cusp ion injection is triggered by the magnetopause reconnection). We study this location as a proxy for the foot point of the reconnection line and call it „ion entry point” in this paper. Our analysis shows that the location of the „ion entry point” has a strong dependence on the sign and magnitude of IMF B y and B z. B y and B z have almost orthogonal effects on the location of the entry point, with the latitudinal displacement linearly related to B z, and the longitudinal displacement linearly related to B y. We find that the B z dependence of the ion entry point is represented by a single regression line for entire range of B z irrespective of its north/south polarity. We also find that the B y dependence is larger for positive B z than for negative B z. The distribution of ion entry points for positive IMF B y is almost a mirror image of that for negative IMF B y with respect to the noon-midnight meridian plane. We discuss the dependence of the „ion entry point” on the IMF from the viewpoint of where and how the magnetopause reconnection (merging) occurs for various orientations of IMF.

Magnetospheric and ionospheric response to a substorm: Geotail HEP‐LD and Polar PIXIE observations

The High Energy Particle ‐ Low energy particle Detector experiment (HEP‐LD) on board the Geotail spacecraft and the Polar Ionospheric X‐ray Imaging Experiment (PIXIE) on board the Polar satellite have been used to examine a substorm event. On December 10, 1996, around 1700 UT, a substorm event with two onsets took place. The event occurred during a weak magnetic storm that started on December 9. Several of the classical substorm features were observed during the event: reconnection and neutral‐line formation in the near‐Earth geomagnetic tail, injection of energetic particles at geosynchronous orbit, and particle precipitation into the ionosphere. Magnetic field line mapping of the energetic precipitation area into the geomagnetic tail shows that the substorm development on ground is closely correlated with topological changes in the near‐Earth tail. In the first onset, mainly soft electrons are involved, with only a transient energetic precipitation delayed relative to the onset. The second onset about 30 min later includes both soft and energetic electrons. The source regions of both onsets are found to be located near the earthward edge of the plasma sheet, while the source region of the transient energetic precipitation during the first onset is in the distant tail. Magnetic reconnection occurs sporadically and burst‐like before the onsets. Both onsets appear to be triggered by northward turning of the interplanetary magnetic field. The study also demonstrates that the concept of pseudobreakups should be used with care unless global observations are available.

Propagation velocities and dimensions of plasmoid structures in the near‐Earth magnetotail

Measurements from the High Energy Particle‐Low energy particle Detector experiment (HEP‐LD) and Magnetic Field experiment (MGF) onboard the GEOTAIL spacecraft are used to estimate characteristic flow velocities and scale sizes of plasmoid structures released in the near‐Earth magnetotail during substorm events. Bulk velocities are derived from the azimuthal distribution of energetic ions and typical scale sizes are thereafter calculated from the duration of the plasmoid signatures. The results show great variability from one event to another. Velocities range from 250–700 km/s and scale sizes were in the range 3–9 RE for the events studied. Despite the great variability, the velocities are somewhat lower than earlier observations from the distant tail.

Latitudinal displacement of cusp ion precipitation: Akebono observations

The solar wind and interplanetary magnetic field (IMF) dependence of low-altitude cusp properties is investigated using data from the Akebono satellite. More than a hundred cusp events are identified with the low energy particle detector (LEP) on board Akebono and are compared to solar wind and IMF data obtained by IMP 8. We have tentatively defined a starting location of the cusp ion precipitation as the location where observed cusp ions had the highest energy in the energy dispersion curve recorded along the satellite path. It is found that the thus defined starting latitude of cusp precipitation correlates almost linearly with IMF B z regardless of its sign. In addition, we studied the solar wind velocity ( V sw ) dependence of the starting latitude.

Energetic oxygen ion bursts in the distant magnetotail as a product of intense substorms: Three case studies

On the basis of Geotail high energy particle ‐ low energy particle detector (HEP‐LD) observations, this paper reports on three energetic (144 – 4000 keV) oxygen burst sequences detected in the distant tail (Xgse = −40 to −66 RE) and their relation to substorm signatures. Those energetic oxygen ion bursts lasted only 20 to 30 min and exhibited strong beam‐like structures. Two of the events (at about 1000 and 1900 UT on February 13, 1994) occurred in tailward flowing plasma after the flow direction changed from earthward to tailward; geostationary and ground based observations detected intense substorm activity during these periods, and the local magnetic field component Bz assumed predominantly negative values. The occurrence of a magnetic field with southward polarity and oxygen bursts embedded in tailward flowing plasma is consistent with the basic signatures of reconnection (formation of a neutral line) in the magnetotail. The third energetic oxygen burst with earthward flow was observed relatively close to Earth on August 27, 1993, X= −40 RE. No reversal in the plasma flow direction was seen, and the magnetic field polarity was essentially positive throughout the event. This is consistent with a “near‐Earth” neutral line that had formed beyond X=−40 RE. We conclude that (1) a large amount of heavy ions from the ionosphere can be transferred to the distant tail and accelerated to high energies during substorm activity and that (2) these oxygen O+ ions from the polar ionosphere can be considered as “tracer ions” in the substorm dynamical process.

Geotail observations of energetic ion species and magnetic field in plasmoid‐like structures in the course of an isolated substorm event

On January 15, 1994, the ion spectrometer high energy particle ‐ low energy particle detector (HEP‐LD) on the Japanese spacecraft Geotail observed five quasi‐periodic energetic ion bursts in the deep tail (X=−96 RE). These bursts were associated with plasmoid‐like structures in the magnetic field components. In. addition, three multiple TCR groups were identified in the interval. The observations in the distant tail occurred during a time interval of substorm activity which also produced multiple injections in the geosynchronous orbit region. The HEP‐LD observations show that Bz bipolar plasmoid‐like structures are associated with tailward flowing particle bursts. However, earthward flowing particle bursts are predominantly associated with bipolar signatures in By. In addition, an oxygen burst was seen in the back of a plasmoid (postplasmoid) which showed both By and Bz bipolar magnetic field signatures. The oxygen burst lasted for 23 min, and the density ratio (O/H) reached 15% for the HEP‐LD energy range (in the same plasmoid, this ratio was approximately 1% before the oxygen burst). The oxygen burst exhibited a strong beam‐like structure which occupied only 6 ∼ 7% of the full solid angle (4π). We suggest that energized oxygen ions of ionospheric origin travel downtail in the narrow postplasmoid‐plasma sheet which trails the plasmoid. Furthermore, we suggest that the magnetosphere dissipated larger quantities of energy during this very intense substorm event by ejecting multiple relatively small plasmoids rather than through the formation and ejection of a single large plasmoid.

Statistical aspects of particle-induced electron emission

The emission statistics of electrons from a W target induced by neutral He0 and Ar0 projectiles have been studied. A probabilistic model is considered for the 'electron emission events' that take place when a projectile bombards the target. The usual two-step model involving initial liberation of electrons from the target atoms in a sequence of collisions and transport of these electrons away from the target surface forms the basis for discussion of the electron emission statistics. Poisson and negative binomial distributions are considered because these fit our measured data well, and their probabilistic postulates are not inconsistent with the known experimental data. It is shown that back-scattered electrons from the detector surface play no significant role in the statistical analysis of the measured data. The quantum efficiency of detection of low-energy particle detectors can differ by about 10% between calculations using Poisson and negative binomial distributions.

The Energetic Particle Spectrometer HEP onboard the GEOTAIL Spacecraft.

The instruments for the HEP (High Energy Particle) experiments of the GEOTAIL mission, launched in July 1992, consist of 5 spectrometers (LD, BD, MI-1, MI-2 and HI). The LD (Low energy particle Detector) and the BD (Burst Detector) are mainly used to measure electrons, protons, helium and oxygen ions which reflect plasma dynamics in the magnetotail region. On the other hand, MI-1, MI-2 (Medium energy Isotope telescope-1, -2) and HI (High energy Isotope telescope) are used to measure the isotope abundance of solar flare particles and cosmic ray particles which reflect physical conditions of interplanetary space and origin of these particles

Detection of 10–20 keV H+, He+ ions and electrons by planar oxide passivated and ion implanted silicon diodes

A low noise UV-enhanced silicon photodiode has been modified into a low energy particle detector by removing the antireflection oxide layer. The electronic noise of a 100 mm2 device and a conventional charge sensitive preamplifier has been measured to 2.3 keV FWHM at room temperature operation. The response of this detector to low energy particles has been investigated. Electrons with 10 keV initial energy looses 0.8 keV in the surface deadlayer. Further, the sum of the energy losses in the deadlayer and to nuclear collisions have been measured to about 3.8 keV for 10 keV protons and 5.4 keV protons and 5.4 keV for 12 keV He+ ions

The low energy particle detector sled (≈30 keV–3.2 MeV) and its performance on the phobos mission to mars and its moons

A low energy particle detector system (SLED) is described which was designed to measure the flux densities of electrons and ions in the energy range from ≈30 keV to a few MeV in (a) the varying solar aspect angles and temperatures pertaining during the Cruise Phase of the Phobos Mission and (b) in the low temperature environment (reaching −25° C) pertaining during Mars Encounter. Representative data illustrating the excellent functioning of SLED during both phases of the mission are presented.

Extreme ultraviolet induced forward photoemission from thin carbon foils

Thin carbon foils have become integral parts of low-energy particle detectors in forthcoming space experiments. In these devices, the foil acts as electron source for signal generation. Since 10–20-eV photons can also generate electrons from these foils and since intense HLα and He i resonance lines prevail in space environment, forward photoemission yield in carbon foils must be investigated. Crabon foils of 2.0, 7.0, and 14.0 μg cm−2 thickness (density 1.35 g cm−3) are subjected to 121.6-nm or 10.2-eV photons and 58.4-nm or 21.2-eV photons and the corresonding forward photoemission yield and transmittance are obtained. Energy distributions of photoemitted electrons are also measured.