Speaker
Description
We report measurements of uniformity of time resolution, signal
amplitude, and charged particle detection efficiency across the sensor surface
of Ultra-Fast Silicon Detectors (UFSD). Comparisons of performance of sensors
with different doping concentrations, and different active thicknesses are
presented, as well as their temperature dependance and radiation tolerance up to
$6\times 10^{14}$~n/cm$^2$. Results were obtained during Spring 2017 campaign at the Fermilab test beam
facility using 120 GeV proton beams, and a high precision pixel tracking
detector. UFSD sensors based on the Low-Gain Avalanche Detector (LGAD) design
were manufactured by the the Centro Nacional de Microelectr`onica (CNM) and
Hamamatsu Photonics (HPK) were tested in the experiments. The uniformity of the
sensor response in pulse height, efficiency and timing resolution were found to
be good pre-radiation, with time resolution around 30-40 psec depending on
operating conditions. A ``no-response'' area between pads which exhibitwas
measured to be around 70~$\mu$m for CNM and 110$\mu$m for HPK sensors. After a
neutron fluence of $6\times 10^{14}$~n/cm$^2$ the CNM sensor exhibits a large
gain variation of a factor 2.5 when comparing metallized and non-metallized
sensor areas. Irradiated CNM sensor achieved time resolution of 30~psec for the
metallized part, and 40~psec for the non-metallized area, while the time
resolution of the HPK sensor was measured to be 30~psec.
