The low Earth orbit radiation environment and its impact on the prompt background of hard x-ray focusing telescopes

Fioretti, Alessandro; Bulgarelli, A.; Malaguti, G.; Bianchin, V.; Trifoglio, M.; Gianotti, F.

doi:10.1117/12.926248

Cited by 13 publications

(11 citation statements)

References 46 publications

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“…As the Earth completely fills the 0-bounce and 2-bounce apertures during occultation mode, we assume that the astrophysical components contribute negligible flux, and include only the internal detector components when modeling the occulted data. In particular, the Earth albedo flux is suppressed by at least one order of magnitude compared to the CXB and GRXE over the energy range of our analysis [111][112][113]. The spectral index and relative normalization of the internal power-law are frozen to their best-fit occultation-mode values during fits to the science data, shown in Figs.…”

Section: Nustar Spectral Modelingmentioning

confidence: 91%

NuSTAR tests of sterile-neutrino dark matter: New Galactic bulge observations and combined impact

Roach

Perez

et al. 2020

Phys. Rev. D

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We analyze two dedicated NuSTAR observations with exposure ∼190 ks located ∼10°from the Galactic plane, one above and the other below, to search for x-ray lines from the radiative decay of sterile-neutrino dark matter. These fields were chosen to minimize astrophysical x-ray backgrounds while remaining near the densest region of the dark matter halo. We find no evidence of anomalous x-ray lines in the energy range 5-20 keV, corresponding to sterile neutrino masses 10-40 keV. Interpreted in the context of sterile neutrinos produced via neutrino mixing, these observations provide the leading constraints in the mass range 10-12 keV, improving upon previous constraints in this range by a factor ∼2. We also compare our results to Monte Carlo simulations, showing that the fluctuations in our derived limit are not dominated by systematic effects. An updated model of the instrumental background, which is currently under development, will improve NuSTAR's sensitivity to anomalous x-ray lines, particularly for energies 3-5 keV.

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Section: Nustar Spectral Modelingmentioning

confidence: 91%

NuSTAR tests of sterile-neutrino dark matter: New Galactic bulge observations and combined impact

Roach

Perez

et al. 2020

Phys. Rev. D

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“…The background environment in an equatorial, low-Earth orbit (LEO), has been extensively discussed in other published works. 7,8 In this section we summarize the main populations of particles and photons which contribute to the on-board background, and which are the inputs to the Monte Carlo simulations of the XGIS instrument. Figure 3 shows the average differential fluxes of these components.…”

Section: Background Sourcesmentioning

confidence: 99%

The XGIS instrument on-board THESEUS: Monte Carlo simulations for response, background, and sensitivity

Campana¹,

Fuschino²,

Labanti³

et al. 2021

Preprint

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The response of the X and Gamma Imaging Spectrometer (XGIS) instrument onboard the Transient High Energy Sky and Early Universe Surveyor (THESEUS) mission, selected by ESA for an assessment phase in the framework of the Cosmic Vision M5 launch opportunity, has been extensively modelled with a Monte Carlo Geant-4 based software. In this paper, the expected sources of background in the Low Earth Orbit foreseen for THESEUS are described (e.g. diffuse photon backgrounds, cosmic-ray populations, Earth albedo emission) and the simulated on-board background environment and its effects on the instrumental performance is shown.

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“…It has been used for the study of the shielding optimization of the Simbol-X and the New Hard X-ray Mission (NHXM) telescopes, and the overall study of the X-ray background radiation in Low Earth Orbit. 42 We use the BoGEMMS framework to simulate the soft proton funnelling into XMM-Newton optics and their impact on the EPIC/pn X-ray spectrum. A simplified model of the XMM-Newton mirror module has been developed ( Figure 5), using as example of Wolter-I X-ray shell the XrayTel exercise provided by the Geant4 user support team.…”

Section: Bogemms Simulationmentioning

confidence: 99%

Monte Carlo simulations of soft proton flares: testing the physics with XMM-Newton

et al. 2016

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Low energy protons (< 100 − 300 keV) in the Van Allen belt and the outer regions can enter the field of view of X-ray focusing telescopes, interact with the Wolter-I optics, and reach the focal plane. The funneling of soft protons was discovered after the damaging of the Chandra/ACIS Front-Illuminated CCDs in September 1999 after the first passages through the radiation belt. The use of special filters protects the XMM-Newton focal plane below an altitude of 70000 km, but above this limit the effect of soft protons is still present in the form of sudden flares in the count rate of the EPIC instruments that can last from hundreds of seconds to hours and can hardly be disentangled from X-ray photons, causing the loss of large amounts of observing time. The accurate characterization of (i) the distribution of the soft proton population, (ii) the physics interaction at play, and (iii) the effect on the focal plane, are mandatory to evaluate the background and design the proton magnetic diverter on board future X-ray focusing telescopes (e.g. ATHENA). Several solutions have been proposed so far for the primary population and the physics interaction, however the difficulty in precise angle and energy measurements in laboratory makes the smoking gun still unclear. Since the only real data available is the XMM-Newton spectrum of soft proton flares in orbit, we try to characterize the input proton population and the physics interaction by simulating, using the BoGEMMS framework, the proton interaction with a simplified model of the X-ray mirror module and the focal plane, and comparing the result with a real observation. The analysis of ten orbits of observations of the EPIC/pn instrument show that the detection of flares in regions far outside the radiation belt is largely influenced by the different orientation of the Earth's magnetosphere respect with XMM-Newton's orbit, confirming the solar origin of the soft proton population. The Equator-S proton spectrum at 70000 km altitude is used for the proton population entering the optics, where a combined multiple and Firsov scattering is used as physics interaction. If the thick filter is used, the soft protons in the 30-70 keV energy range are the main contributors to the simulated spectrum below 10 keV. We are able to reproduce the proton vignetting observed in real data-sets, with a ∼ 50% decrease from the inner to the outer region, but a maximum flux of ∼ 0.01 counts cm −2 s −1 keV −1 is obtained below 10 keV, about 5 times lower than the EPIC/MOS detection and 100 times lower than the EPIC/pn one. Given the high variability of the flare intensity, we conclude that an average spectrum, based on the analysis of a full season of soft proton events is required to compare Monte Carlo simulations with real events.

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The low Earth orbit radiation environment and its impact on the prompt background of hard x-ray focusing telescopes

Cited by 13 publications

References 46 publications

NuSTAR tests of sterile-neutrino dark matter: New Galactic bulge observations and combined impact

NuSTAR tests of sterile-neutrino dark matter: New Galactic bulge observations and combined impact

The XGIS instrument on-board THESEUS: Monte Carlo simulations for response, background, and sensitivity

Monte Carlo simulations of soft proton flares: testing the physics with XMM-Newton

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