A small satellite version of a soft x-ray polarimeter

Marshall, Herman L.; Heine, Sarah N. T.; Garner, Alan; Gullikson, Eric M.; Günther, Hans Moritz; Leitz, Christopher; Masterson, Rebecca; Miller, Eric D.; Zhang, William; Malaquin, Rozenn Boissay; Caiazzo, Ilaria; Chakrabarty, Deepto; Davidson, Rosemary; Gallo, Luigi; Heilmann, Ralf K.; Kara, Erin; Marscher, A. P.; Schulz, Norbert S.

doi:10.1117/12.2562811

Cited by 7 publications

(13 citation statements)

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“…We note that other future developments in x-ray astrophysics may also require a better understanding of charge diffusion in solid-state image sensors. These include x-ray polarimetry 11 and very high-resolution x-ray imaging. 12 Table 1 Requirements for future x-ray probe and Flagship missions.…”

Section: Introductionmentioning

confidence: 99%

Measurement and simulation of charge diffusion in a small-pixel charge-coupled device

LaMarr

Prigozhin

Miller

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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Future high-resolution imaging x-ray observatories may require detectors with both fine spatial resolution and high quantum efficiency at relatively high x-ray energies (E ≥ 5 keV). A silicon imaging detector meeting these requirements will have a ratio of detector thickness to pixel size of six or more, roughly twice that of legacy imaging sensors. The larger aspect ratio of such a sensor's detection volume implies greater diffusion of x-ray-produced charge packets. We investigate consequences of this fact for sensor performance, reporting charge diffusion measurements in a fully depleted back-illuminated CCD with a thickness of 50 μm and pixel size of 8 μm. We are able to measure the size distributions of charge packets produced by 5.9 and 1.25 keV x-rays in this device. We find that individual charge packets exhibit a Gaussian spatial distribution and determine the frequency distribution of event widths for a range of detector bias (and thus internal electric field strength) levels. At the largest bias, we find a standard deviation for the largest charge packets (produced by x-ray interactions closest to the entrance surface of the device) of 3.9 μm. We show that the shape of the event width distribution provides a clear indicator of full depletion and use a previously developed technique to infer the relationship between event width and interaction depth. We compare measured width distributions to simulations. Although we can obtain good agreement for a given detector bias, with our current simulation, we are unable to fit the data for the full range of bias levels with a single set of simulation parameters. We compare traditional, "sum-above-threshold" algorithms for individual event amplitude determination to Gaussian fitting of individual events and find that better spectroscopic performance is obtained with the former for 5.9 keV events, whereas the two methods provide comparable results at 1.25 keV. The reasons for this difference are discussed. We point out the importance of read-noise driven charge detection thresholds in degrading spectral resolution, and note that the derived read noise requirements for mission concepts such as AXIS and Lynx are probably too lax to assure that spectral resolution requirements can be met. While the measurements reported here were made with a CCD, we note that they have implications for the performance of high aspect-ratio silicon active pixel sensors as well.

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Section: Introductionmentioning

confidence: 99%

Measurement and simulation of charge diffusion in a small-pixel charge-coupled device

LaMarr

Prigozhin

Miller

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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“…The science objectives and observing plan are the same as for PiSoX, so we refer the reader to the PiSoX paper 2 for more details. In one year, the GOSoX mission would obtain spectropolarimetric measurements across the 0.2-0.4 keV band for about a dozen sources to measure polarization fractions as small as 3-10%.…”

Section: Science Objectivesmentioning

confidence: 99%

“…A "minimum mission" we consider scientifically useful is to obtain > 10% MDP for each of 3 sources from both of our two categories, driving the instrument requirements. 2 Published spectra for these sources were used to compute count rates in the GOSoX instrument. In addition to the science targets is a "null" calibrator -a bright, unresolved binary of cool stars with thermal coronae.…”

Section: Science Objectivesmentioning

confidence: 99%

“…The approach is nearly identical to that of a mission proposed for the NASA Astrophysics Pioneers program, PiSoX. 2 For this paper, we will describe the basic design of GOSoX and the concept study of the GOSoX mission, as carried out by JPL Team X (hereafter, Team X), funded by the NASA AS 3 program. The AS 3 program was an opportunity for mission concept studies in the scope of CubeSats, SmallSats, and secondary RideShare opportunities.…”

Section: Introductionmentioning

confidence: 99%

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The Globe Orbiting Soft X-ray (GOSoX) polarimeter concept study

Marshall

Heine

Davidson

et al. 2021

Optics for EUV, X-Ray, and Gamma-Ray Astronomy X

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We describe an implementation of a broad-band soft X-ray polarimeter, substantially based on previous designs. This implementation, the Globe-Orbiting Soft X-ray Polarimeter (GOSoX) is a SmallSat, designed for NASA's call for Astrophysics Science SmallSat Studies (AS 3 ). As in a related mission concept PiSoX, the grating arrangement is designed optimally for the purpose of polarimetry with broad-band focussing optics by matching the dispersion of the spectrometer to a laterally graded multilayers (LGML). The system can achieve polarization modulation factors over 90%. For GOSoX, the optics are lightweight Si mirrors in a one-bounce parabolic configuration. Critical Angle Transmission (CAT) gratings from opposite sectors are oriented to disperse to a LGML forming a channel covering the wavelength range from 31 Å to 75 Å (165 -400 eV). Upon satellite rotation, the intensities of the dispersed spectra, after reflection and polarizing by the LGMLs, give the three Stokes parameters needed to determine a source's linear polarization fraction and orientation. The design can be extended to higher energies as LGMLs are developed further. We describe the potential scientific return and traceability, proposed mission concept and design, and estimated mission costs, following the results of the JPL Team X concept study.

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“…We note that other future developments in X-ray astrophysics may also require a better understanding of charge diffusion in solid-state image sensors. These include X-ray polarimetry 11 and very high-resolution X-ray imaging. 12 We have been developing advanced CCDs for use in Lynx.…”

Section: Introductionmentioning

confidence: 99%

Measurement and simulation of charge diffusion in a small-pixel charge-coupled device

LaMarr¹,

Prigozhin²,

Miller³

et al. 2022

Preprint

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Future high-resolution imaging X-ray observatories may require detectors with both fine spatial resolution and high quantum efficiency at relatively high X-ray energies (E ≥ 5 keV ). A silicon imaging detector meeting these requirements will have a ratio of detector thickness to pixel size of six or more, roughly twice that of legacy imaging sensors. The larger aspect ratio of such a sensor's detection volume implies greater diffusion of X-ray-produced charge packets. We investigate consequences of this fact for sensor performance, reporting charge diffusion measurements in a fully-depleted back-illuminated CCD with a thickness of 50 µm and pixel size of 8 µm. We are able to measure the size distributions of charge packets produced by 5.9 keV and 1.25 keV X-rays in this device. We find that individual charge packets exhibit a gaussian spatial distribution, and determine the frequency distribution of event widths for a range of detector bias (and thus internal electric field strength) levels. At the largest bias, we find a standard deviation for the largest charge packets (produced by X-ray interactions closest to the entrance surface of the device) of 3.9 µm. We show that the shape of the event width distribution provides a clear indicator of full depletion, and use a previously developed technique to infer the relationship between event width and interaction depth. We compare measured width distributions to simulations. Although we can obtain good agreement for a given detector bias, with our current simulation we are unable to fit the data for the full range of of bias levels with a single set of simulation parameters. We compare traditional, 'sum-above-threshold' algorithms for individual event amplitude determination to gaussian fitting of individual events and find that better spectroscopic performance is obtained with the former for 5.9 keV events, while the two methods provide comparable results at 1.25 keV. The reasons for this difference are discussed. We point out the importance of read-noise driven charge detection thresholds in degrading spectral resolution , and note that the derived read noise requirements for mission concepts such as AXIS and Lynx are probably too lax to assure that spectral resolution requirements can be met. While the measurements reported here were made with a CCD, we note that they have implications for the performance of high aspect-ratio silicon active pixel sensors as well.

show abstract

A small satellite version of a soft x-ray polarimeter

Cited by 7 publications

References 54 publications

Measurement and simulation of charge diffusion in a small-pixel charge-coupled device

Measurement and simulation of charge diffusion in a small-pixel charge-coupled device

The Globe Orbiting Soft X-ray (GOSoX) polarimeter concept study

Measurement and simulation of charge diffusion in a small-pixel charge-coupled device

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