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4D Sensors: Unifying the Space and Time Domain with Ultra-Fast Silicon Detectors

4D Sensors: Unifying the Space and Time Domain with Ultra-Fast Silicon Detectors.

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4D Sensors: Unifying the Space and Time Domain with Ultra-Fast Silicon Detectors

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  1. 4D Sensors: Unifying the Space and Time Domain with Ultra-Fast Silicon Detectors Hartmut Sadrozinski, with Scott Ely, VitaliyFadeyev, Zachary Galloway, Jeffrey Ngo, Colin Parker, Brett Petersen, Abe SeidenSCIPP, Univ. of California Santa CruzNicoloCartiglia, AmadeoStaianoINFN TorinoMara Bruzzi, Riccardo Mori, Monica Scaringella, Anna VinattieriUniversitade Firenze

  2. “4D” • Ultra-Fast Silicon Detectors (UFSD) incorporate the time-domain into the excellent position resolution of semiconductor sensors • they provide in the same detector and readout chain • ultra-fast timing resolution [10’s of ps] • precision location information [10’s of mm] A crucial element for UFSD is the charge multiplication in silicon sensors investigated by RD50, which permits the use of very thin detectors without loss of signal-to-noise. • 2 questions need to be addressed for UFSD: • can they work: signal, capacitance, collection time vs. thickness • will they work: required gain and E-field, fast readout • We hope that we will answer the questions within an RD50 Common Project (GiulioPellegrini) Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  3. Up to now, semiconductor sensors have supplied precision data only for the 3 space dimensions (diodes, strips, pixels, even “3D”), while the time dimension has had limited accuracy (e.g. to match the beam structure in the accelerator). We believe that being able to resolve the time dimension with ps accuracy would open up completely new applications not limited to HEP Proposal: Combined-function pixel detector will collect electrons from thin n-on-p pixel sensors read out with short shaping time electronics Charge multiplication with moderate gain g ~10 increases the collected signal Need very fast pixel readout Motivation for UFSD Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  4. Benefits of Ultra-Fast Silicon Detectors - Tracking: Identifying with high precision the temporal signature of different events allows for their association and it reduces random coincidences. Traditional tracking is often overwhelmed by combinatorial backgrounds, which can be dramatically reduced by adding a 4th dimension (time) per point. - Time of Flight (ToF): ToF is already used in many commercial applications such as ToF-enhanced PET and Mass Spectroscopy ToF, however with precision one order of magnitude higher than the goal of UFSD (~500 ps vs. ~50 ps). ToF is also used in particle physics as a tool for particle identification. ToF can also be used in 3D and Robotic Vision: the ability to accurately measure the travel time of light pulses reflected by an object at unknown distance is of paramount importance to reconstruct 3D images, fundamental in imaging and robotic vision. UFSD will offer a spatial precision of a few mm at low illumination power, allowing for battery operated, portable systems. - Particle counting: UFSDperformance would allow developing new tools in single particle counting applications with unprecedented rate capabilities. For example, in the treatment of cancer using hadron beams, such a tool would measure the delivered dose to patients by directly counting the number of hadrons. Material science experiments using soft x-rays will benefit from the combination of high rate and precision location that UFSDoffers. Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  5. Remote Sensing in HEP Time of flight determines position: with σt=10 ps, σx= 3 mm, i.e. locate a proton within 3 mm in 20 cm long IP Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  6. TOF for Particle Identification in Space The Alpha Magnetic Spectrometer (AMS) detector, operating in the International Space Station since 2011, performs precision measurements of cosmic ray composition and flux. The momentum of the particles is measured with high-resolution silicon sensors inside a magnetic field of about 1 m length. Atime resolution of 10 picoseconds, the “Holy Grail” of Cosmic Ray Physics: the distinction between anti-carbon ions and anti-protons can be achieved up to a momentum of 200 GeV/c. Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  7. Future: 4-D Ultra-Fast Si Detectors ? Protons of 200 MeV have a range of ~ 30 cm in plastic scintillator. The straggling limits the WEPL resolution. Replace calorimeter/range counter by TOF: Light-weight, combine tracking with WEPL determination Range straggling limit for 200 MeV p Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  8. Positron Emission Tomography PET Study accumulation of radioactive tracers in specific organs. The tracer has radioactive positron decay, and the positron annihilates within a short Distance with emission of 511 keVγ pair, which are observed in coincidence. Perfect Picture: Resolution and S/N Effects: Resolution of detector (pitch) Positron range A-collinearity Parallax (depth) T: true event S: Compton Scatter R: Random Coincidence A. Del Guerra, RESMDD12 Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  9. Reduce Accidentals & Improve Image: TOF-PET PET t1 t2 TOF-PET Localization uncertainty: Dd= c x Dt /2 When Dt = 200 ps ➔Dd = 3 cm @ VCI K. Yamamoto 2012 IEEE NSS-MIC Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  10. TOF – PET SNR Improvement • The improved source localization due to timing • leads to an improvement in signal-to-noise • and an increase in Noise Equivalent Count NEC For a given acquisition time and dose to the patient, TOF can provide better image quality and improved lesion detection. OR with TOF the scan time and dose can be reduced while keeping the same image quality ( better clinical workflow and added comfort for the patient). M. Conti, Eur. J. Nucl. Med. MoI Imaging (2011) 38:1147-1157 Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  11. Can it work? UFSD Collected Charge Realistic gain & cap Good time resolution Per 1 cm Signal = thickness*EPM (EPM = 73 e-/mm Collection time = thickness/vsat (vsat = 80 mm/ns) WRONG For thickness > 5 um, Capacitance to the backplane Cb << Cint For thickness = 2 um, Cb ~ ½ of Cint, and we might need bipolar (SiGe)? Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  12. Details of Collected Charge in Thin Sensors Energy loss measurement for charged particles in very thin silicon layers S. Meroli, D. Passeri and L. Servoli 11 JINST 6 P06013 Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  13. Correct UFSD Collected Charge Realistic gain & cap Good time resolution Per 1 cm Gain needed for a sensor thickness of 10 µm Pixel about 4 1 cm long strips about 20 (much less than APD’s or SiPM) Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  14. Impact Ionization A. Macchiolo,16th RD50 Workshop Barcelona, Spain, May 2010 Charge multiplication in path length ℓ : At the breakdown field in Si of 270kV/cm: ae≈ 1 pair/um ah ≈ 0.1 pair/um → In the linear mode (gain ~10), consider electrons only Raise maximum and minimum E-field as close to breakdown field as possible Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  15. Non-uniform E-Field across a pixel/strip Example of electric field: Ф = 1.6·1015 n/cm2, U = 900 V Non-uniform Field across the implant results in charge collection difference Gregor Kramberger, 19th RD50 Workshop, CERN, Nov 2011 A. Macchiolo, 16th RD50 Workshop Barcelona, Spain, May 2010 Even if non-uniformity of field across the implant is only 30%, a large fraction of the center of the implant does not exhibit charge multiplication before sensor breakdown ! Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  16. M. Köhler, et al., Nucl. Physics B – Proceed. Supplements 215, 1, (2011), 247-249 Charge Multiplication C.M. RD50 investigated C.M. and found it in irradiated sensors only. C.M. exists if signal is in excess of pre-rad value orin excess of trapping measurementsAdvantage of thin sensors because of high E-field But indication of excess noise. I. Mandic et al., Nucl. Instr. and Meth. A 612, (2010 ) 474-477. G. Casse et al, NIM A 624, 2, (2010) 401–404 Expectation from trapping extrapolation Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  17. Epi, short drift on planar diode g = 6.5 Using red laser and a’s probes E-field and gainclose to the junction, where it counts. Diode gives uniform field. J. Lange et al., Nucl.Instrum.Meth A622, 49-58, 2010. Need uniform field: 3D or diode-like Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  18. CERN fixed-target experiment (NA62) needs very fast pixel sensors: Gigatracker (GTK) Prototype CFD system (INFN Torino) has ~ 100 ps resolution, predicted to be 30 ps in next iteration. Optimized for 200mm sensors and hole collection (?), could it be re-designed for electron collection from 2 – 10mm sensors? What about fast readout: Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

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  23. Firenze ps Laser Data: 50 um p-on-n 6kW-cm FWHM becomes constant at about 150 V bias Rise times RT and trise are ~ independent of bias: Bandwidth of system Above 120V bias, the field > 25kV/cm, i.e. large enough to saturate the drift velocity, i.e. constant collection time. • Laser: 1.2 ps pulse width & 10 ns period,red 740 nm, penetrates ~6 um. • Oscilloscope: 500 MHz bandwidth • Charge collection of electrons moving away from laser spot • Terminal velocity ~ 100um/ns, i.e. expected collection time ~500ps for high fields Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  24. Study of ’s from Thorium 230 50 um thick P-type epi diodes Challenge for manufacturers: For charge multiplication, need breakdown voltage >1000V!! Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  25. Pulses from Th 230 alpha’s Do NOT expect: Charge multiplication Expect collection time of ~ 500ps for over-depleted bias (drift velocity is saturated) large rise time dispersion for low bias voltage

  26. Assume doping distributions with maximum 2 doping distributions, uniform in depth,“padsfields” Doping Profiles & Biasing + n p- epi + p substr. Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

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  31. G. Kramberger, Preliminary! Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  32. G. Kramberger, Preliminary! Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  33. G. Kramberger, Preliminary! Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  34. G. Kramberger, Preliminary! Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  35. Explanation of rapid rise and level Rapid rise of signal up to 100V during the depletion of the sensor. “plateau” beyond this : gain almost constant beyond ~50V ? Toy Simulation Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  36. Why/How does C.M. work stably? Breakdown associated with charge multiplication in high fields: Our experience with drift chambers tells us that you need a “quenching” mechanism That’s why the “magic gas” worked, a mixture of 4 gases: It added to the high gain of Ar the quenching of CO2, isobutane, and methylal or DME. The fact that we observe gain in low-resistivity (low-R) silicon at RT and low currents as well as in irradiated sensors with large numbers of defects and high currents seems to indicate that the quenching comes from the large numbers of defects which provide trapping of excessive charges. Planar vs. 3D: “smart money” is on planar, although 3D has a uniform 1/r field around electrode it seems to be harder to get the proper implant profile for the high field section. Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  37. 4D UFSD Score Card March 2013 Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

  38. Quo Vadis with 4D UFSD? • Fast developments: • First Presentation June 2, 2012 in Bari for RD50 • November 2012: Common Project within RD50 accepted • Research project funded by DoE within the SCIPP Instrumentation Section • 2 EU Research proposals submitted • including Torino (Frontend ASIC), Vienna (DAQ) • March 2013: Gain of ~10 seen in un-irradiated diodes • March 2013: submission of dedicated strip sensors for gain studies (CNM) • Spring 2013: Spanish grad student Marta to come to SCIPP • SCIPP’s role: • Application of SiGe in front-end (work with Torino) • Simulations (Marta & Colin & ..) • Pulse shape studies (need fast scope and increasingly faster pre-amps!) • Strip readout vs. pixel readout Hartmut F.-W. Sadrozinski: UFSD SCIPP 2013

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