Design of the charged particle diverter for the ATHENA mission

Ferreira, Ivo; Ayre, Mark; Bavdaz, Marcos; Guainazzi, M.; Stefanescu, A.; Komárek, Michael; Valenta, T.; Hynek, R.; Závodník, M.; Sobotka, Piotr; Pejchal, T.; Badin, Viktor; Kalousek, Radek; Bačovský, Jaromír; Horák, Michal; Flajšman, Lukáš; Wojewoda, Ondřej; Zlámal, Jakub

doi:10.1117/12.2312226

Cited by 7 publications

(14 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It may also be possible to replicate the field of the solenoids here using permanent magnets, perhaps by using single large magnets for each solenoid that have a surface current such that they replicate the effect of a coil of wires. Alternatively, it may be possible to replicate a solenoid field using a ring of magnets for each solenoid similar to that used by primary particle magnetic diverters in existing missions 23 . While passive magnetic shielding like this would remove the power requirements of generating such a magnetic field, the magnets may need to be graded-Z shielded 24 to ensure that fluorescence from high atomic number materials in the magnets does not influence the detector background (although this might also have to be done in the case of copper solenoids).…”

Section: Full Cosmic Ray Proton Spectrum Simulation Resultsmentioning

confidence: 99%

Effectiveness of a dual solenoid magnetic shield at reducing x-ray-like background in silicon-based x-ray detectors

Davis

Hall

2023

J. Astron. Telesc. Instrum. Syst.

View full text Add to dashboard Cite

.Magnetic shielding has been used during past and current x-ray astronomy missions to shield detectors from electrons entering through telescope optics, and soft proton diverters have also been planned for future missions. However, simulations performed throughout the past decade have discovered that a significant proportion of x-ray-like background originates from secondary electrons produced in spacecraft shielding surrounding x-ray detectors, which hit detectors isotropically from all directions. Here, the results from Geant4 simulations of a simple dual solenoid magnetic field surrounding a 450 μm thick detector with several on-chip layers based on the structure of preliminary designs for the ATHENA Wide Field Imager are presented. We found that for a magnetic field strength at the middle between the two coils of equal to or greater than ∼12 mT, a dual solenoid magnetic field is extremely effective at preventing secondary electrons depositing between 2 and 7 keV and induced by galactic cosmic protons from reaching the detector. While the exact level of background reduction would depend on specific spacecraft and detector design, this magnetic shielding method could remove almost all background associated with backscattering and absorbed electrons, which are expected to account for approximately two thirds of the expected off-axis background in silicon-based x-ray detectors of several hundred microns in thickness and would likely be even more effective for thinner detectors where x-ray-like background is even more dominated by electrons. The magnetic field structure necessary for doing this could be produced using a set of solenoids or neodymium magnets providing that power requirements can be sufficiently optimized or neodymium fluorescence lines can be sufficiently attenuated, respectively. Testing would also have to be done to ensure that detectors it is used on are sufficiently magnetically hard; for context, the current limit for magnetic field strength around the ATHENA Wide Field Imager is 1 mT although CCD97s, another type of space-based x-ray detector, are magnetically hard at least above 6.4 mT.

show abstract

Section: Full Cosmic Ray Proton Spectrum Simulation Resultsmentioning

confidence: 99%

Effectiveness of a dual solenoid magnetic shield at reducing x-ray-like background in silicon-based x-ray detectors

Davis

Hall

2023

J. Astron. Telesc. Instrum. Syst.

View full text Add to dashboard Cite

show abstract

“…20 The method of mitigating this source of damaging particles and background is to divert their path with a magnetic field. A magnetic diverter has been designed for the Athena/WFI, 21 which consists of a circular Halbach array using individual magnets, and the LEDA design draws inspiration from that design by scaling it down to the single detector.…”

Section: Magnetic Diverter Designmentioning

confidence: 99%

“…The former is based on the geometry of the X-ray optics and the position and size of the X-ray detector. 21,23,24 Based on the geometry, a deflection angle of about 10 to 13 degrees is needed for an approximate 500 mm distance of the diverter from the detector. The required energy range is more complicated, and there is considerable effort needed to understand the soft proton environment and their interaction with the detector filters.…”

Section: Magnetic Diverter Designmentioning

confidence: 99%

“…The starting assumption is that all protons < 75 keV must be deflected, which is in line with conclusions from. 21,24 Figure 10 shows the diverter as three layers of the magnets in a mechanical fixture. Because the Halbach array has a finite thickness and gaps between the magnets, its field is not uniform in a plane parallel to the array, as would be desired.…”

Section: Magnetic Diverter Designmentioning

confidence: 99%

See 1 more Smart Citation

Background simulations for the high energy x-ray probe (HEX-P)

Madsen,

Fleischhack,

Violette

et al. 2023

UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XXIII

View full text Add to dashboard Cite

HEX-P is an X-ray probe-class mission concept that will combine high angular resolution (<15 arcsec) with broad band spectral coverage (0.2 -80 keV) to enable revolutionary new insights into the important astrophysical questions of the next decade identified by the 2020 Decadal Survey. Sensitivity is key to the instrument performance and estimating the background a crucial step in the development of the design and prediction of the instrument performance. The HEX-P orbit is at L1, and since L1 has hosted no prior missions with X-ray coverage that can be used to estimate the background level, the particle background has to be simulated. We present here the simulations done to evaluate the contribution to the background from charged particles, which show that the high energy background is dominated by hadronic activation in the detector mass and prompt leptons. To reduce the additional cosmic X-ray background (CXB), which is non-charged, the instruments are fitted with apertures and blocking plates of a graded-Z material to attenuate the CXB to a level an order of magnitude below the requirement.

show abstract

“…3 The ESA and ATHENA team developed a novel concept to minimize the background induced by soft protons. 6 A Hallbach array of magnets is placed between the optical system and each of the detectors. The one in front of WFI is pear-shaped, has a diameter of 35 cm and its magnets weigh 21 kg.…”

Section: Introductionmentioning

confidence: 99%

Geant4 simulation of the residual background in the ATHENA wide field imager from protons deflected by the charged particle diverter

Galgóczi¹,

Jean-Paul²,

Fioretti³

et al. 2022

Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray

Self Cite

View full text Add to dashboard Cite

X-ray telescopes opened up a new window into the high-energy universe. However, the last generation of these telescopes encountered an unexpected problem: their optics focused not only X-rays but low-energy (so called soft) protons as well. These protons are very hard to model and can not be distinguished from X-rays. For example, 40% of XMM-Newton observations is significantly contaminated by soft proton induced background flares. In order to minimize the background from such low-energy protons the Advanced Telescope for High ENergy Astrophysics (ATHENA) satellite introduced a novel concept, the so called Charged Particle Diverter (CPD). It is an array of magnets in a Hallbach design, which deflects protons below 76 keV before they would hit the Wide Field Imager (WFI) detector. In this work, we investigate the effect of scattering of the deflected protons with the CPD walls and the inner surfaces of the WFI detector assembly. Such scattered protons can loose energy, change direction and still hit the WFI. In order to adopt the most realistic instrument model, we imported the CAD model of both the CPD and the WFI focal plane assembly. Soft protons corresponding to ≈2.5 hours of exposure to the L1 solar wind are simulated in this work. The inhomogeneous magnetic field of the CPD is included in the simulation. We present a preliminary estimate of the WFI residual background induced by soft proton secondary scattering, in the case of the optical blocking filter present in the field of view. A first investigation of the volumes responsible for scattering the protons back into the field of view is reported.

show abstract

Design of the charged particle diverter for the ATHENA mission

Cited by 7 publications

References 6 publications

Effectiveness of a dual solenoid magnetic shield at reducing x-ray-like background in silicon-based x-ray detectors

Effectiveness of a dual solenoid magnetic shield at reducing x-ray-like background in silicon-based x-ray detectors

Background simulations for the high energy x-ray probe (HEX-P)

Geant4 simulation of the residual background in the ATHENA wide field imager from protons deflected by the charged particle diverter

Contact Info

Product

Resources

About