Researchers Develop X-ray Polarimeter with 15% Modulation for Solar Flare Observation and Analysis

Solar flares, powerful bursts of energy from the sun, remain challenging to fully understand, but a new X-ray polarimeter promises to shed light on their complex behaviour. Kouichi Hagino, Tatsuaki Kato, and Toshiya Iwata, along with their colleagues, have developed a system utilising micro-pixel CMOS sensors to measure the polarisation of X-rays emitted during these flares. This research represents a significant step forward, as previous studies have confirmed the underlying principle but lacked practical evaluation for observing actual solar events. The team’s measurements demonstrate the polarimeter’s sensitivity to X-ray polarisation across a key energy range, and their calculations suggest the system, when combined with existing telescope technology, could detect even weak polarisation signals from moderate-sized flares, offering valuable insights into the processes driving these energetic phenomena.

This system incorporates a 2. 5 μm pixel CMOS image sensor with a 12. 8 mm x 12. 8 mm imaging area, coupled with a Zynq System-on-Chip for data processing, and demonstrates sensitivity to X-ray polarisation, exhibiting a modulation factor of 5.15% across an energy range of 6, 22 keV. Detailed measurements reveal the sensitive layer thickness to be approximately 5 μm, with insensitive layers measuring 0. 8 μm (silicon), 2. 1 μm (silicon dioxide), and 0. 24 μm (copper), resulting in a quantum efficiency of 3.

4% at 10 keV. These findings indicate that, when combined with existing telescope technology, this micro-pixel CMOS polarimeter system has the potential to detect X-ray polarisation from M-class solar flares, offering a new avenue for studying the energetic processes within these events. Researchers acknowledge that the system’s efficiency remains relatively low, currently at only a few percent, and this limits the speed of data acquisition. Future work will likely focus on improving the quantum efficiency and reducing noise to enhance the system’s sensitivity and ability to rapidly capture data from these dynamic solar phenomena. The ability to measure X-ray polarisation will allow scientists to distinguish between thermal and non-thermal electron emissions, determine the energy distribution during flares, and probe the transport processes of accelerated particles, potentially revealing details about electron anisotropy and acceleration mechanisms. This advancement promises to unlock new insights into the fundamental physics governing solar flares and the energetic processes within our sun, opening avenues for future research and potentially improving space weather forecasting.

X-ray Polarimetry for Astrophysical Environments

X-ray polarimetry is rapidly becoming a vital tool for understanding high-energy phenomena in astrophysics and solar physics. Measuring the polarisation of X-rays provides unique information about the physical processes occurring in extreme environments, often inaccessible through traditional X-ray observations. This technique is being applied to several key areas. In astrophysics, scientists are using X-ray polarimetry to study black hole systems, probing the geometry of accretion disks and jets around black holes. They are also investigating active galactic nuclei, mapping their magnetic field structure and emission mechanisms, and examining neutron stars and pulsars to understand their extreme magnetic fields.

Furthermore, researchers are studying supernova remnants to investigate particle acceleration and magnetic field amplification. In solar physics, the focus is on solar flares, coronal magnetic fields, and coronal mass ejections, aiming to understand the magnetic field configurations and dynamics of these events. Several technologies are driving these advancements. CMOS sensors are becoming increasingly popular as detection elements due to their high sensitivity, low power consumption, and potential for miniaturisation. Micro-pattern gas detectors are also being used.

Coded aperture masks are employed to create imaging polarimeters. Focusing optics, such as grazing incidence mirrors and multi-layer optics, are used to increase sensitivity. Some approaches involve modulating the polarisation of incoming X-rays. Sophisticated data reconstruction algorithms are needed to process the raw detector data. Access to high-intensity X-ray beamlines and dedicated test facilities is crucial for development and calibration.

Accurate calibration of detector efficiency is also essential. Several missions and projects are contributing to this field. The Imaging X-ray Polarimetry Explorer (IXPE) is a key mission. The Focusing Optics X-ray Solar Imager (FOXSI) is a sounding rocket mission using focusing optics. The Solar Polarimeter for the ReSuRRection mission (SPR-N) was a past experiment on the CORONAS-F satellite. Numerous projects are focused on improving CMOS sensors for X-ray polarimetry, and dedicated beamlines are being developed at facilities like Spring-8. In summary, X-ray polarimetry is a vibrant and rapidly evolving field poised to unlock the mysteries of the high-energy universe and the Sun.

Solar Flare X-ray Polarimetry with CMOS Sensors

Researchers have developed a novel X-ray polarimeter employing micro-pixel CMOS sensors specifically for observing solar flares. This system utilises a 2. 5 μm pixel CMOS image sensor with a 12. 8 mm x 12. 8 mm imaging area, coupled with a Zynq System-on-Chip for data processing, and successfully demonstrated sensitivity to X-ray polarisation, achieving a modulation factor of 5.

15% within an energy range of 6, 22 keV. Through measurements at synchrotron facilities, they determined the thicknesses of the sensor’s various layers, which led to an estimated quantum efficiency of 3. 4% at 10 keV. These findings indicate that, when combined with existing telescope technology, this micro-pixel CMOS polarimeter system has the potential to detect X-ray polarisation from M-class solar flares, offering a new avenue for studying the energetic processes within these events. Researchers acknowledge that the system’s efficiency remains relatively low, currently at only a few percent, and this limits the speed of data acquisition. Future work will likely focus on improving the quantum efficiency and reducing noise to enhance the system’s sensitivity and ability to rapidly capture data from these dynamic solar phenomena.

CMOS Polarimeter Detects Solar Flare X-rays

This research details the development of a new X-ray polarimeter designed for observing solar flares, utilising micro-pixel CMOS sensors. The team successfully demonstrated that the polarimeter is sensitive to X-ray polarisation, achieving a modulation factor of 5. 15% within an energy range of 6, 22 keV. Detailed measurements reveal the sensitive layer thickness to be approximately 5 μm, with insensitive layers measuring 0. 8 μm (silicon), 2.

1 μm (silicon dioxide), and 0. 24 μm (copper), resulting in a quantum efficiency of 3. 4% at 10 keV. These findings indicate that, when combined with existing telescope technology, this micro-pixel CMOS polarimeter system has the potential to detect X-ray polarisation from M-class solar flares, offering a new avenue for studying the energetic processes within these events. Researchers acknowledge that the system’s efficiency remains relatively low, currently at only a few percent, and this limits the speed of data acquisition. Future work will likely focus on improving the quantum efficiency and reducing noise to enhance the system’s sensitivity and ability to rapidly capture data from these dynamic solar phenomena.