Hard X-ray compton polarimetry with the PENGUIN-M instrument in the spaceborne experiment CORONAS-PHOTON (original) (raw)
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Prospects of the Hard X-Ray Instrument POLAR to Measure Polarization of Solar Flares
Journal of Applied Mathematics and Physics, 2015
In-depth studies of solar flares emissions and energy releases include analyses of polarization data. Polarization gives clear information about mechanisms and processes leading to electron acceleration and photon production. Despite of many past attempts, the key energy range of hard X-rays was only rarely explored and results were inconclusive. To large extend it was due to greater instrumental complications. Currently several novel polarimeters are either to be employed or under constructions for both balloon and satellite based observations. The novel hard X-ray polarimeter POLAR is an instrument developed by a collaboration between Switzerland, China and Poland. It is primarily designed for high accuracy polarization measurements from the prompt photon emissions of the gamma-ray bursts. The satellite orientation and instrument pointing direction make it also capable for precise measurements of polarization in solar flares. The instrument should fly in near future onboard of the Chinese Space Station TG2.
Astronomy and Astrophysics, 2011
Aims. We study the polarization of hard X-ray (HXR) sources in the solar atmosphere, including Compton backscattering of photons in the photosphere (the albedo effect) and the spatial distribution of polarization across the source. Methods. HXR photon polarization and spectra produced via electron-ion bremsstrahlung emission are calculated from various electron distributions typical for solar flares. Compton scattering and photoelectric absorption are then modelled using Monte Carlo simulations of photon transport in the photosphere to study the observed (primary and albedo) sources. Polarization maps across HXR sources (primary and albedo components) for each of the modelled electron distributions are calculated at various source locations from the solar centre to the limb. Results. We show that Compton scattering produces a distinct polarization variation across the albedo patch at peak albedo energies of 20-50 keV for all anisotropies modelled. The results show that there are distinct spatial polarization changes in both the radial and perpendicular to radial directions across the extent of the HXR source at a given disk location. In the radial direction, the polarization magnitude and direction at specific positions along the HXR source will either increase or decrease with increased photon distribution directivity towards the photosphere. We also show how high electron cutoff energies influence the direction of polarization at above ∼100 keV. Conclusions. Spatially resolved HXR polarization measurements can provide important information about the directivity and en-ergetics of the electron distribution. Our results indicate the preferred angular resolution of polarization measurements required to distinguish between the scattered and primary components. We also show how spatially resolved polarization measurements could be used to probe the emission pattern of an HXR source, using both the magnitude and the direction of the polarization.
X-Ray Polarization of Solar Flares Measured with Rhessi
Solar Physics, 2006
The degree of linear polarization in solar flares has not yet been precisely determined despite multiple attempts to measure it with different missions. The high energy range, in particular, has very rarely been explored, due to its greater instrumental difficulties. We approached the subject using the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) satellite to study six X-class and 1 M-class flares in the energy range between 100 and 350 keV. Using RHESSI as a polarimeter requires the application of strict cuts to the event list in order to extract those photons that are Compton scattered between two detectors. Our measurements show polarization values between 2 and 54%, with errors ranging from 10 to 26% in 1σ level. In view of the large uncertainties in both the magnitude and direction of the polarization vector, the results can only reject source models with extreme properties.
Gamma‐Ray Polarimetry of Two X‐Class Solar Flares
The Astrophysical Journal, 2006
We have performed the first polarimetry of solar flare emission at γ-ray energies (0.2-1 MeV). These observations were performed with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) for two large flares: the GOES X4.8-class solar flare of 2002 July 23, and the X17-class flare of 2003 October 28. We have marginal polarization detections in both flares, at levels of 21 ± 9% and-11 ± 5% respectively. These measurements significantly constrain the levels and directions of solar flare γ-ray polarization, and begin to probe the underlying electron distributions.
Response of the Compton polarimeter POLAR to polarized hard X-rays
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011
POLAR is a novel compact space-borne Compton polarimeter conceived for a precise measurement of hard X-ray polarization and optimized for the detection of Gamma-Ray Burst (GRB) photons in the energy range 50-500 keV. In December 2009 we have performed a systematic calibration of one modular unit of POLAR at four energy levels (200, 288, 356 and 511 keV) with a 100% polarized synchrotron radiation source at the beam line ID15A at ESRF. The detector was displaced several times on the beam line in order to achieve a uniform illumination, which mimics the flux from a GRB placed on the zenith of the experiment. Several rotations of the detector on the beam axis allowed us to test the response of POLAR to several polarization angles. Two different analysis methods to reconstruct the polarization angle of the beam and the modulation factor m 100 are presented; the first relies on the existence of a unpolarized sample, produced by merging two data sets with orthogonal polarization directions, and is less dependent on systematic effects due to asymmetries in the detector; the second is independent from unpolarized measurements, and will likely be used to analyze the polarization of GRB during the flight. Both methods reconstruct the input polarization angle within 21 and produce modulation factors m 100 between 30% and 50% depending on the beam energy. Monte Carlo simulations performed with GEANT4 confirm the experimental results.
Imaging X-ray Polarimeter for Solar Flares (IXPS)
Experimental Astronomy, 2011
We describe the design of a balloon-borne Imaging X-ray Polarimeter for Solar flares (IXPS). This novel instrument, a Time Projection Chamber (TPC) for photoelectric polarimetry, will be capable of measuring polarization at the few percent level in the 20–50 keV energy range during an M- or X-class flare, and will provide imaging information at the ∼10 arcsec level. The primary objective of such observations is to determine the directivity of nonthermal high-energy electrons producing solar hard X-rays, and hence to learn about the particle acceleration and energy release processes in solar flares. Secondary objectives include the separation of the thermal and nonthermal components of the flare X-ray emissions and the separation of photospheric albedo fluxes from direct emissions.
First Two Months Operation of Hard X-ray Polarimeter PENGUIN-M On-board Satellite CORONAS-PHOTON
galprop.stanford.edu
The operation of the "PENGUIN-M" device on board the "CORONAS-PHOTON" spacecraft during first months in orbit is described. Characteristics of the device are given as well as general description of software for experimental data processing and analysis. The progress of in-flight adjustment of the "PENGUIN-MD" detector unit in actual background conditions is described. Observation results are reported for soft X-ray solar flare emission and hard X-rays from cosmic gamma-ray bursts. The registered events were used for estimating the sensitivity of the device.
Coronal scattering as a source of flare-associated polarized hard X-rays
Solar Physics, 2003
We consider the scattering of flare-associated X-rays above 1 keV at coronal heights, particularly from regions of enhanced density. This includes a discussion of the polarization of the scattered X-rays. Although the scattered radiation would not be bright by comparison with the total hard X-ray flux from a flare, its detectability would be enhanced for events located a few degrees behind the limb for which the dominant "footpoint" hard X-ray sources are occulted. Thus we predict that major flares occurring beyond the solar limb may be detectable via scattering in density enhancements that happen to be visible above the limb, and that such sources may be strongly polarized. Since thin-target bremsstrahlung will generally greatly exceed the scattered thick-target flux in flare loops themselves, these considerations apply only to coronal structures that do not contain significant populations of non-thermal electrons.