Speaker
Description
At PSI, we are developing inverse Low-Gain Avalanche Diode (iLGAD) sensors in collaboration with Fondazione Bruno Kessler (FBK) to extend the application of hybrid detectors to the soft X-ray range. iLGAD features an internal gain layer, which enables a significant increase in the signal-to-noise ratio (SNR) for soft X-ray detection. To account for the shallow absorption depth of low-energy photons, we implemented a thin entrance window (TEW) in the iLGAD to enhance its quantum efficiency (QE).
In this presentation, we will report on the QE measurements of the latest TEW batch, which exceed 85% at 250 eV—comparable to state-of-the-art soft X-ray detectors. Beyond QE, we will also present recent beam-test results obtained at the MAX IV synchrotron using soft X-rays from 390 eV to 2500 eV. The iLGAD was bump-bonded to the MÖNCH [1] charge-integrating readout chip, featuring a pixel size of 25 μm. The results demonstrate that single-photon detection can be achieved at 400 eV with an SNR > 5.
Furthermore, a reduction in signal amplitude was observed at the Si K-edge (1839 eV). To investigate this, a grazing incidence beam test was performed at ESRF using a focused beam to map the gain at various photon absorption depths. The analysis reveals that the gain for photons absorbed immediately after the gain layer is lower than for deeper absorption. At the Si K-edge, the X-ray attenuation length drops sharply from 14 μm to 1 μm, shifting the majority of photon absorption into this lower-gain region and explaining the observed amplitude drop. These experimental findings show good agreement with dynamic gain simulations using TCAD.
[1] M. Ramilli, et al 2017 JINST 12 C01071