Detector R&D Seminar
Wednesday 9 Oktober, 10:30 – 12.00h, at Nikhef in H331
Speaker: Prof. dr. R. Klanner (Hamburg University)
Title: "Challenges for and Optimization of Silicon Pixel Sensors for the European XFEL"
The high instantaneous intensity and the high repetition rate of 4.5 MHz of the European X-Ray Free-Electron Laser XFEL pose new challenges for imaging detectors. The specific requirements for the detectors are a dynamic range of up to more than 104 photons of typically 12.4 keV per pixel for an XFEL pulse duration of < 100 fs, with a clear separation of 1 from 0 photons, and a radiation tolerance for doses up to 1 GGy for 3 years of operation. Within the AGIPD Collaboration the Hamburg group has systematically studied the consequences of these requirements for p+n silicon sensors and has optimized the sensor design using TCAD simulations. In February 2013 the first batches have been received and first measurements show that the optimization has been successful.
The topics discussed in particular are:
– Measurements and simulations of the so-called plasma effect, which occurs for high instantaneous charge densities
– Experimental determination of the density of oxide-charges, interface traps and surface currents for X-ray doses up to 1GGy using C/G-V (Capacitance/Conductance-Voltage) as function of frequency and TDRC (Thermal Dielectric Relaxation Current) measurements using different test structures.
– Experimental study of the accumulation layer and field distribution at the Si-SiO2 interface and of the boundary conditions on the passivation of the sensor.
– TCAD optimization for the AGIPD Pixel Sensor with respect to breakdown voltage for a X-ray dose varying from 0 to 1 GGy over the sensor
– Comparison of the breakdown voltage of the optimized sensor with a non-radiation-optimized sensor up to 10 MGy.