Speaker
Description
The Swiss Light Source 2.0, a 4th generation synchrotron radiation source based on a Diffraction-Limited Storage Ring (DLSR), offers high brilliance and coherence with a fundamental pulse repetition rate of 500 MHz. In the soft X-ray branch, Time-Resolved Scanning Transmission X-ray Microscopy (TR-STXM) technique previously utilized Avalanche Photodiodes (APDs) to study dynamic phenomena with a time resolution of few hundred picoseconds using pump-probe techniques and leveraging on the bunch structure of the machine. However, the increased photon flux following the upgrade leads to a significant pile-up of X-ray pulses in APDs, limiting their performance and requiring a segmented detector to distribute the photons over several readout channels.
In collaboration with the Fondazione Bruno Kessler, we designed circular Trench-Isolated Low-Gain Avalanche Diodes (TI-LGADs) segmented into eight sectors with independent readout pads to address this challenge. This allows separating signals of individual pulses, supporting eight times the flux compared to the existing single-channel APD. In this study, the time resolution of a readout sector was characterized using a 660 nm red laser and soft X-ray photons (500–1400 eV) at the SoftiMAX beamline of MAX IV in Sweden read out using an oscilloscope. The impact of sensor bias voltage, beam intensity, and photon energy on time resolution was systematically investigated. Furthermore, we found the time resolution was also influenced by the bandwidth and sampling rate of the oscilloscope and the quality (slew rate) of the reference signal synchronized to the synchrotron.
A time resolution of <100 picoseconds has been demonstrated highlighting the potential of TI-LGADs for high-flux soft X-ray detection at the upgraded SLS-2.0.
The experimental results will be presented in this contribution and further improvements for soft X-ray detection will be discussed.
