Ultra-Fast Silicon Detector 1 Aide memoire: we are exploring the possibility of using silicon detectors with moderate gain to achieve ~ 20 ps time resolution. Nicolo Cartiglia, INFN, Torino - UFSD - PPS Timing Nicolo Cartiglia With INFN Gruppo V, LGAD group of RD50, FBK and Trento University, Micro- Electronics Turin group Rome2 - INFN.

2 Time Resolution and slew rate Assuming constant noise, to minimize time resolution we need to maximize the S/t r term (i.e. the slew rate dV/dt of the signal)  We need large and short signals  where: - S/t r = dV/dt = slew rate - N = system noise - V th = 10 N Using the expressions in the previous page, we can write Nicolo Cartiglia, INFN, Torino - UFSD - PPS Timing

Low Gain Avalanche Detectors (LGADs) 3 The LGAD sensors, as proposed and manufactured by CNM (National Center for Micro-electronics, Barcelona): High field obtained by adding an extra doping layer E ~ 300 kV/cm, closed to breakdown voltage Gain layer High field Nicolo Cartiglia, INFN, Torino - UFSD - PPS Timing

4 Signal amplitude Reference sensor Gain ~ 10 Using laser signals we are able to measure the different responses of LGAD and traditional sensors

5 Testbeam Measurements on CNM LGAD In collaboration with Roma2, we went to Frascati for a testbeam using 500 MeV electrons Nicolo Cartiglia, INFN, Torino - UFSD - PPS Timing 300 micron thick, 5 x5 mm pads The gain mechanism preserves the Landau amplitude distribution of the output signals As measured in the lab, the gain ~ doubles going from 400 -> 800 Volt.

120 GeV 50  m EPI, Cividec BB Scope Ch1 300  m, G10 (I ~ 50  A), Cividec BB, Scope Ch2 300  m, G10 (I ~ 5  A), Cividec SCA Scope Ch3 120 GeV/c pions, CERN North Area, 23 November 2014

7 Present results and future productions Nicolo Cartiglia, INFN, Torino - UFSD - PPS Timing With WF2, we can reproduce very well the laser and testbeam results. Assuming the same electronics, and 1 mm 2 LGAD pad with gain 10, we can predict the timing capabilities of the next sets of sensors. Current Test beam results and simulations Next prototypes Effect of Landau fluctuations

8 Sensor thickness and slim edge Nicolo Cartiglia, INFN, Torino - UFSD - PPS Timing Rule: when the depletion volume reaches the edge, you have electrical breakdown. It’s customary to assume that the field extends on the side by ~ 1/3 of the thickness. edge = k* thickness k = 1 very safe k = 0.5 quite safe K = 0.3 limit depleted ~ 0.3 d non depleted By construction, thin detectors (~ 100 micron) might have therefore slim edge

9 Next CNM productions Nicolo Cartiglia, INFN, Torino - UFSD - PPS Timing 5 mm 2.5 mm 1.25 mm 0.6 mm Timescale: Spring 2015 : 200 micron Summer 2015 : 100 micron Summer 2015 : 50 micron These new productions will allow a detailed exploration of the UFSD timing capabilities, including border effects between pads, and distance from the sensor edge.

10 Electronics Nicolo Cartiglia, INFN, Torino - UFSD - PPS Timing ~ 30 channels per plane: no need for excess integration. Currently designing the analog system using MMIC components: PSA ADL5601 C Mini-Circuits PSA is a E-PHEMT based Ultra- Low Noise MMIC Amplifier operating from 50 MHz to 4 GHz, Ultra Low Noise: 0.75 dB at 1 GHz 0.98 dB at 2 GHz The ADL5601 is a broadband, 15 dB linear amplifier that operates at frequencies up to 4.0 GHz. Very nice read-out circuit designed by Stony Brook for Quartic-AFP, used at the common testbeam in December: Oscilloscope

11 Next Steps 1. Wafer Production 200 micron thick sensors by Spring and 50 micron thick sensors by Summer Production of UFSD doped with Gallium instead of Boron. 3.Front-end electronics under study, several options available. Nicolo Cartiglia, INFN, Torino - UFSD - PPS Timing