Speaker
Description
Hybrid detectors are the state-of-the-art technology widely used in imaging experiments using hard X-rays. They are also highly attractive for soft X-ray experiments (200 eV – 2 keV) due to their high frame rate, large area coverage, and strong radiation tolerance. However, in the soft X-ray energy range, their performance is limited by the low quantum efficiency of silicon sensors, which are typically used in hard X-ray domain, and by a low signal-to-noise ratio. To overcome these limitations, inverse Low-Gain Avalanche Diodes (iLGADs) with a thin entrance window are being developed at the Paul Scherrer Institute in collaboration with Fondazione Bruno Kessler.
iLGAD sensors, bump-bonded to 25 µm pitch charge-integrating Mönch chips, have been characterized using soft X-rays at the 4th-generation synchrotron radiation source MAX IV in Sweden. We will present the results of these measurements, including the spectral response of iLGADs with different gain layer designs at various temperatures and X-ray energies. The spectrum produced by iLGADs features a two-peak structure: a hole-initiated multiplication peak and an electron-initiated multiplication peak, corresponding to photon absorption before and after the gain layer, respectively. We will demonstrate the relationship between photon absorption depth and the proportion of hole- and electron-initiated multiplication at different X-ray energies. Based on this relationship, we are able to determine the thicknesses of the n+ layer beneath the entrance window and of the gain layer.
Additionally, we have observed a decrease in signal amplitude at X-ray energies above the Silicon K-edge, and an additional peak just below the electron-initiated multiplication peak. Through detailed spectral analysis, we will explore the relationship between signal amplitude reduction, iLGAD gain, and photon absorption depth. Finally, we will discuss the possible causes of the additional peak and the signal amplitude reduction, along with plans for further testing and improvements of iLGADs for soft X-ray detection.
| Workshop topics | Sensor materials, device processing & technologies |
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