An international team from the Physical Research Laboratory (PRL), Ahmedabad, and Stanford University has built a highly sensitive, one-dimensional position-sensitive X‑ray detector designed for Compton X‑ray polarimeters, a development that could let astronomers measure the polarization of hard X‑rays from extreme cosmic sources such as black holes and pulsars. The laboratory prototype, tested with a radioactive source, combines a ten-centimetre Sodium Iodide scintillator with silicon photomultiplier sensors at both ends to record where and with what energy incoming X‑ray photons hit the detector.
Polarization describes the direction in which light waves vibrate; measuring it for high-energy X‑rays reveals the shapes and magnetic fields of the distant objects that produced them. Hard X‑rays are difficult to measure because they are far less common than lower-energy photons and require very sensitive detectors. To overcome this, the researchers used a Sodium Iodide crystal that emits a small flash of light when struck by an X‑ray photon and read that light with Silicon Photomultipliers at each end of the crystal.
When an X‑ray interacts with the crystal the flash travels to both ends. By comparing the brightness seen by each photomultiplier, the team can infer the interaction position along the crystal; by summing the two signals they obtain the X‑ray’s energy. In lab tests, the group placed the crystal in a dark chamber and scanned it with an Americium source moved stepwise along its length. Requiring simultaneous detection by both sensors — a coincidence readout — filtered out false thermal signals and reduced background noise by about a factor of ten.
The dual-ended design is a marked improvement over earlier single-ended detectors that used slower scintillators and were sensitive only near the sensor. The new approach maintains sensitivity across the full crystal while providing both location and energy information. The team did note efficiency falls by up to 40 percent near the crystal’s extreme ends, where some scintillation light is lost inside the housing. The prototype currently detects X‑rays down to about 30 kiloelectron‑volts (keV); the researchers aim to refine the electronics to reach roughly 20 keV, the optimal band for many space observations.
If miniaturised and flown on small satellites, these dual-ended Compton polarimeter detectors could finally capture elusive hard X‑rays from accretion disks, magnetised pulsars and other high-energy phenomena, helping map three-dimensional structures and magnetic fields and test physics under extreme conditions.
Original Source: https://researchmatters.in/news/scientists-develop-highly-sensitive-high-energy-x-ray-detector-peer-extreme-cosmic
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Publish Date: 2026-06-16 06:00:00
