Improving X-ray detection

Researchers at the US National Institute of Standards and Technology (NIST) have developed an improved experimental X-ray detector that could pave the way to a new generation of wide-range, high-resolution trace chemical analysis instruments.

In a recently published technical paper, the researchers described how they used improved temperature-sensing and control systems to detect X-rays across a very broad range of energies (6keV or more), with pinpoint energy resolution (an uncertainty of only 2eV).

The detector’s ability to distinguish between X-rays with very similar energies should be especially useful to the semiconductor industry for chemical analysis of microscopic circuit features or contaminants. Many types of high-resolution microscopes routinely used in the industry and throughout science produce detailed chemical maps by scanning a surface with electrons and then analysing the X-rays emitted, which are characteristic of specific elements.

The NIST device, an improved version of its previous microcalorimeter X-ray detector, uses a quantum-level, transition edge sensor (TES). A TES works by measuring the current across a thin metal film that is held at the transition temperature between a superconducting state and normal conductance. A single X-ray photon striking the detector raises the temperature enough to alter the current proportional to the energy of the photon.