Comparison of 35 and 50 {\mu}m thin HPK UFSD after neutron irradiation up to 6*10^15 neq/cm^2

TL;DR

This study compares 35 and 50 micrometer thick HPK UFSD sensors after neutron irradiation up to 6×10^15 neq/cm^2, highlighting the advantages of the thinner sensors in timing, bias voltage, and power within the tested fluence range.

Contribution

It provides the first detailed comparison of 35 μm and 50 μm thick UFSD sensors under high neutron irradiation, demonstrating the benefits of thinner sensors for timing and operational parameters.

Findings

35 μm UFSD shows better timing resolution post-irradiation.

Thinner sensors operate effectively at lower bias voltages.

Power consumption is reduced in 35 μm UFSD.

Abstract

We report results from the testing of 35 {\mu}m thick Ultra-Fast Silicon Detectors (UFSD produced by Hamamatsu Photonics (HPK), Japan and the comparison of these new results to data reported before on 50 {\mu}m thick UFSD produced by HPK. The 35 {\mu}m thick sensors were irradiated with neutrons to fluences of 0, 1*10^14, 1*10^15, 3*10^15, 6*10^15 neq/cm^2. The sensors were tested pre-irradiation and post-irradiation with minimum ionizing particles (MIPs) from a 90Sr \b{eta}-source. The leakage current, capacitance, internal gain and the timing resolution were measured as a function of bias voltage at -20C and -27C. The timing resolution was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction method for both. Within the fluence range measured, the advantage of the 35 {\mu}m thick UFSD in timing accuracy, bias voltage and power can be established.