Fig. 1: Hybrid pixel detector and LGAD sensors.

a Layout of the hybrid pixel detector used. The iLGAD sensor, where X-rays are converted into electric charge, is connected pixel-by-pixel to the EIGER readout electronics using bump bonding. The readout chip is biased, controlled, and read out through wire-bond pads. b Sketch of the cross-section of the inverse-LGAD sensor. X-rays enter from the top through a thin entrance window composed of passivation and a shallow n⁺ doping layer. The p⁺ gain layer forms a junction with a high electric field, enabling charge multiplication via impact ionization. The signal is induced in the p⁺ pixels, which are connected to the readout electronics using bump bonding. c Multiplication factor M as a function of photon absorption depth for standard (red) and shallow (black) iLGAD variations⁴⁵. The blue lines and secondary y-axis axis represent the transmission of 500 eV (dashed) and 1000 eV (dash-dotted) photons.