A MAPS-based readout of an electromagnetic calorimeter for the ILC Nigel Watson (Birmingham Univ.) Motivation Physics simulations Sensor simulations Testing Summary For the CALICE MAPS group J.P.Crooks, M.M.Stanitzki, K.D.Stefanov, R.Turchetta, M.Tyndel, E.G.Villani (STFC-RAL) Y.Mikami, O.D.Miller, V.Rajovic, NKW, J.A.Wilson (Birmingham) J.A.Ballin, P.D.Dauncey, A.-M.Magnan, M.Noy (Imperial)

ILC: high performance calorimetry Essential to reconstruct jet-jet invariant masses in hadronic final states, e.g. separation of W+W, Z0Z0, tth, Zhh, H Mass (jet1+jet2) Mass (jet3+jet4) E/E = 60%/E E/E = 30%/E Equivalent best LEP detector Goal at ILC LEP/SLD: optimal jet reconstruction by energy flow Explicit association of tracks/clusters Replace poor calorimeter measurements with tracker measurements – no “double counting” Little benefit from beam energy constraint, cf. LEP Nigel Watson / Birmingham EPS'07, 19-Jul-2007

ECAL design principles Shower containment in ECAL,  X0 large Small Rmoliere and X0 – compact and narrow showers int/X0 large,  EM showers early, hadronic showers late ECAL, HCAL inside coil Lateral separation of neutral/charged particles/’particle flow’ Strong B field to suppresses large beam-related background in detector Compact ECAL (cost of coil) Tungsten passive absorber Silicon pixel readout, minimal interlayer gaps, stability “Swap-in” alternative to Si diode detector designs, e.g. in LDC, SiD CMOS process, more mainstream: Industry standard, multiple vendors (schedule, cost) (At least) as performant – ongoing studies Simpler assembly Power consumption larger – but better thermal properties Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Weighted no. pixels/event Incoming photon energy (GeV) Basic concept for MAPS Swap ~0.5x0.5 cm2 Si pads with small pixels “Small” := at most one particle/pixel 1-bit ADC/pixel, i.e. Digital ECAL Effect of pixel size How small? EM shower core density at 500GeV is ~100/mm2 Pixels must be<100100mm2 Our baseline is 5050mm2 Gives ~1012 pixels for ECAL – “Tera-pixel APS” Weighted no. pixels/event 50mm >1 particle/ pixel 100mm Incoming photon energy (GeV) Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Tracking calorimeter 5050 μm2 MAPS pixels ZOOM SiD 16mm2 area cells

Geant4 energy of simulated hits Physics simulation 0.5 GeV MPV = 3.4 keV σ = 0.8 keV 5 GeV 200 GeV Geant4 energy of simulated hits Ehit (keV) MAPS geometry implemented in Geant4 detector model (Mokka) for LDC detector concept Peak of MIP Landau stable with energy Definition of energy: E a Npixels Artefact of MIPS crossing boundaries Correct by clustering algorithm Optimal threshold (and uniformity/stability) important for binary readout 20 GeV photons s(E)/E Threshold (keV) Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Architecture-specific CALICE INMAPS ASIC1 0.18mm feature size First round, four architectures/chip (common comparator+readout logic) INMAPS process: deep p-well implant 1 μm thick under electronics n-well, improves charge collection 4 diodes Ø 1.8 mm Architecture-specific analogue circuitry Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Device level simulation Physics data rate low – noise dominates Optimised diode for Signal over noise ratio Worst case scenario charge collection Collection time Signal/noise 0.9 μm 1.8 μm 3.6 μm Distance to diode (charge injection point) Signal/Noise Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Near future plans 3 July: 1st sensors delivered to RAL Work ongoing on the set of PCBs holding, controlling and reading the sensor. Test device-level simulations using laser-based charge diffusion measurements at RAL l=1064, 532,355 nm,focusing < 2 μm, pulse 4ns, 50 Hz repetition, fully automated Cosmics and source setup, Birmingham and Imperial, respectively. Potential for beam test at DESY end of 2007 Expand work on physics simulations Test performance of MAPS ECAL in GLDC and SiD detector concepts Emphasis on re-optimisation of particle flow algorithms Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Summary Concept of CMOS MAPS digital ECAL for ILC Multi-vendors, cost/performance gains New INMAPS deep p-well process (optimise charge collection) Four architectures for sensor on first chips, delivered to RAL Jul 2007 Tests of sensor performance, charge diffusion to start in August Physics benchmark studies with MAPS ECAL to evaluate performance relative to standard analogue Si-W designs, for both SiD and LDC detector concepts Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Backup slides… Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Type dependant area: capacitors, and big resistor or monostable Architectures on ASIC1 Presampler Preshaper Type dependant area: capacitors, and big resistor or monostable Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Beam background studies purple = innermost endcap radius 500 ns reset time  ~ 2‰ inactive pixels Beam-Beam interaction by GuineaPig Detector: LDC01sc 2 scenarios studied : 500 GeV baseline, 1 TeV high luminosity Nigel Watson / Birmingham EPS'07, 19-Jul-2007

The sensor test setup 1*1 cm² in total 5 dead pixels 2 capacitor arrangements 2 architectures 6 million transistors, 28224 pixels 5 dead pixels for logic : hits buffering (SRAM) time stamp = BX (13 bits) only part with clock lines. 7 * 6 bits pattern per row 84 pixels 42 pixels Row index Data format 3 + 6 + 13 + 9 = 31 bits per hit Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Impact of digitisation E initial : geant4 deposit Neighbouring hit: hit ? Neighbour’s contribution no hit ? Creation of hit from charge spread only + noise σ = 100 eV, minus dead areas : 5 pixels every 42 pixels in one direction All contributions added per pixel + noise σ = 100 eV What remains in the cell after charge spread assuming perfect P-well Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Device level simulation Physics data rate low – noise dominates Optimised diode for Signal over noise ratio Worst case scenario charge collection Collection time. Using Centaurus TCAD for sensor simulation + CADENCE GDS file for pixel description Collected charge Signal/noise 0.9 μm 1.8 μm 3.6 μm Distance to diode Distance to diode Nigel Watson / Birmingham EPS'07, 19-Jul-2007

Digitisation procedure %Einit Einit Geant4 Einit in 5x5 μm² cells Apply charge spread Eafter charge spread Register the position and the number of hits above threshold + noise only hits : proba 10-6  ~ 106 hits in the whole detector BUT in a 1.5*1.5 cm² tower : ~3 hits. Importance of the charge spread : Add noise to signal hits with σ = 100 eV (1 e- ~ 3 eV  30 e- noise) Sum energy in 50x50 μm² cells Esum Nigel Watson / Birmingham EPS'07, 19-Jul-2007