Scientists develop highly sensitive high-energy X-Ray detector to peer into extreme cosmic environments

In a major step forward for decoding our universe, an international team of scientists from Physical Research Laboratory, Ahmedabad, and Stanford University, USA, has successfully developed a highly sensitive X-ray detector that could help us investigate the universe’s most extreme environments. The breakthrough involves a one-dimensional position-sensitive detector designed for Compton X-ray polarimeters. The new technology aims to measure the polarization of high-energy, or hard, X-rays emitted by cosmic giants like black holes and pulsars. The team included researchers 

Polarization refers to the direction in which light waves vibrate. Studying polarized X-rays from space helps astronomers understand the shape and magnetic fields of distant cosmic objects that produced the light. However, measuring hard X-rays is incredibly difficult because these high-energy photons are scarce, and our instruments lacked the sensitivity to catch them. To solve this, the researchers built their new detector using a Sodium Iodide crystal. This material is known as a scintillator because it produces a tiny flash of light whenever an X-ray photon crashes into it. 

The team attached silicon light sensors, known as Silicon Photomultipliers, to both ends of a ten-centimetre-long Sodium Iodide crystal. When an X-ray hits the crystal, the resulting flash of light travels to both ends. The photomultiplier then amplifies this flash of light enough to be measurable. By comparing the brightness of the light that reaches each end, the scientists can calculate exactly where the X-ray struck the crystal. Furthermore, by adding the two signals together, they can determine the exact energy of the incoming X-ray.

To test their new detector, the researchers placed the crystal in a completely dark room and fired X-rays at it using a radioactive Americium source. They moved the source step-by-step along the length of the crystal to see how well the sensors could track the impacts. They discovered that by requiring both sensors to detect light at the same time, a technique called coincidence reading, they could filter out false signals caused by thermal heat inside the electronics. This new method reduced the background noise by a massive factor of ten. 

This new design is a vast improvement over previous models, which used a slower-reacting crystal and only had a sensor on one end. Those older detectors were only sensitive to X-rays that hit very close to the sensor, making them inefficient for large-scale space observations. The new dual-ended design ensures the detector remains sensitive across its entire length while also providing crucial information about the X-ray’s location and energy.

The researchers, however, noted that the detector’s efficiency drops by up to forty percent near the extreme ends of the crystal because some light is lost bouncing around inside the housing before it can reach the sensors. Additionally, while the detector currently works well for X-rays with energies down to thirty kiloelectron-volts, the team hopes to optimize their electronics to detect even weaker X-rays down to twenty kiloelectron-volts, which is the optimal range for space observations.

This technological leap promises to revolutionize our view of the universe’s most extreme and violent phenomena. By equipping future small satellites with these highly sensitive, dual-ended detectors, astronomers will finally be able to clearly capture the elusive hard X-rays emitted by cosmic heavyweights, such as the swirling disks of superheated gas around black holes or the intense magnetic storms of rapidly spinning pulsars. Because this advanced instrument can simultaneously measure the precise energy, location, and polarization of these incoming photons, it could help cut through the astronomical noise to reveal the 3D shapes and magnetic structures of distant celestial bodies. It gives scientists a new tool to map out the high-energy cosmos, test the fundamental laws of physics under extreme conditions, and ultimately deepen our understanding of how the most mysterious objects in our universe function and evolve.