<p>We describe the imaging concept used by the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) project. In its high-altitude balloon payload form, GRIPS is equipped with a rotating grid (Multi-Pitch Rotating Modulator, MPRM) with 13 pitches ranging from <InlineEquation ID="IEq1"> <EquationSource Format="MATHML"><math> <mo>≈</mo> <mn>12.5</mn> </math></EquationSource> <EquationSource Format="TEX">$\approx12.5$</EquationSource> </InlineEquation>” to <InlineEquation ID="IEq2"> <EquationSource Format="MATHML"><math> <mo>≈</mo> <mn>162.5</mn> </math></EquationSource> <EquationSource Format="TEX">$\approx162.5$</EquationSource> </InlineEquation>” FWHM angular resolutions. An array of spatially-differentiated (pixelized) germanium strip detectors (GeD) allows the localization of incoming photons from <InlineEquation ID="IEq3"> <EquationSource Format="MATHML"><math> <mo>∼</mo> <mn>20</mn> </math></EquationSource> <EquationSource Format="TEX">$\sim20$</EquationSource> </InlineEquation> keV to <InlineEquation ID="IEq4"> <EquationSource Format="MATHML"><math> <mo>></mo> <mn>10</mn> </math></EquationSource> <EquationSource Format="TEX">$>10$</EquationSource> </InlineEquation> MeV, to within the strip pitch of <InlineEquation ID="IEq5"> <EquationSource Format="MATHML"><math> <mo>∼</mo> <mn>0.5</mn> </math></EquationSource> <EquationSource Format="TEX">$\sim0.5$</EquationSource> </InlineEquation> mm or better. At <InlineEquation ID="IEq6"> <EquationSource Format="MATHML"><math> <mo>≳</mo> <mn>100</mn> </math></EquationSource> <EquationSource Format="TEX">$\gtrsim100$</EquationSource> </InlineEquation> keV, Compton reconstruction can also be used to reject non-solar photons and determine polarization.</p><p>In this introductory paper, we concentrate on the optical response (point-spread-function) of the imaging grid from low to high energies. We also introduce several detector effects, which become progressively more important at higher energies.</p>

Monogrid Imaging with Pixelized Detectors: The GRIPS Imaging Concept

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2025年11月28日

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Pascal Saint-Hilaire,
Gordon J. Hurford,
Albert Y. Shih,
Meredith A. Wieber

摘要

We describe the imaging concept used by the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) project. In its high-altitude balloon payload form, GRIPS is equipped with a rotating grid (Multi-Pitch Rotating Modulator, MPRM) with 13 pitches ranging from $\approx 12.5$ $\approx12.5$ ” to $\approx 162.5$ $\approx162.5$ ” FWHM angular resolutions. An array of spatially-differentiated (pixelized) germanium strip detectors (GeD) allows the localization of incoming photons from $\sim 20$ $\sim20$ keV to $> 10$ $>10$ MeV, to within the strip pitch of $\sim 0.5$ $\sim0.5$ mm or better. At $≳ 100$ $\gtrsim100$ keV, Compton reconstruction can also be used to reject non-solar photons and determine polarization.

In this introductory paper, we concentrate on the optical response (point-spread-function) of the imaging grid from low to high energies. We also introduce several detector effects, which become progressively more important at higher energies.