4th KSETA Plenary Workshop 2017 Tracking detectors in modern - PowerPoint PPT Presentation

4th KSETA Plenary Workshop 2017 Tracking detectors in modern par2cle physics experiments (*) Norbert Wermes University of Bonn (*) = mostly LHC, but not only 1

Outline q Tracking in the LHC -> HL-LHC environment q Some basic elements of tracking and tracking detectors q Tracking with Semiconductors q Pixels: from Hybrid to Monolithic detectors q Picosecond 2ming with silicon? q Conclusions 2 N. Wermes, Desy Kolloquium 2016

3 N. Wermes, Desy Kolloquium 2016

ATLAS Where are we? ... or ... “from chips to Higgs and back” Run 1 (2010-12) detector development LHC ≅ 10 6 x LEP in track rate ! Run 2 (2015-18): Run 1 x 5 2018 + ... Run 1 x 10 ? pixel detector module 2026 + ... Run 1 x 10 – 20 ? pp – collisions ATLAS pixel detector installa2on precise tracking 4 N. Wermes, Desy Kolloquium 2016

q spa2al precision q rate capability q radia2on tolerance q high detec2on efficiency (in-2me) q 2ming accuracy q track reconstruc2on in boosted jets q space vectors augmen2ng simple “hits” 5

ATLAS Pixel Detector in operaRon 4-hit pixel system! layer 2 layer 1 important for b-quark tagging B-layer IBL low luminosity, 2 interac2ons Cosmic 6 N. Wermes, Desy Kolloquium 2016

e ν pp -> WH -> νl + bb 22 collisions piling up 7 N. Wermes, Desy Kolloquium 2016

jet 200 pile-up events τ τ jet 78 pile-up events CMS (Run 1) ~9 cm (2σ) 8 N. Wermes, Desy Kolloquium 2016

Tasks of Tracking Detectors q provide precise space points or space point clusters (vectors) origina2ng from ionizing charged par2cles § par2cle track finding from pakerns of ATLAS measured hits (at large background & pile-up) § momentum (B-field) and angle measurement § measurement of primary and secondary ver2ces ~170 µm § mul2-track separa2on and vertex-ID in the ~16 µm core of (boosted) jets ~10 µm § for low momentum tracks: measurement of the specific ioniza2on (dE/dx) q keep the material influencing the paths of par2cles to a minimum to avoid scakering in the material and secondary interac2ons

Good tracking ... p T and IP measurement as example y approximate helix by a linearized circle L and perform a least square fit r ✓ σ p T ◆ p T 720 σ meas σ meas = p ⊗ σ MS T 0 . 3 | z | L 2 B p T N + 4 d 0 meas x 0 x Gluckstern NIM 24 (1963) 381 σ meas meas σ d 0 ⊗ σ MS r = x 0 /L = extrapola2on parameter Technology most osen used: Si - detectors op2mize σ meas un2l other effects dominate (e.g. MS) § PRO – high resolu2on σ meas ~ 10 µm 1/L 2 : the longer L the beker § CON – expensive place first plane as near as possible to the prod. point § – small N p T resol. linearly beker with B-field strength … § – small L but more confusion if many tracks – small X 0 => large mult. scatt. Increasing N improves the resolu2on, but only as 1/√N § PRO – high rate capability 10 N. Wermes, Desy Kolloquium 2016

Gas-filled versus semiconductor detectors - CDF H1 ++ material -- + N meas high low cost -- ++ rate/speed 100 µm resolu2on 10 µm field near wire E(r) ~ 1/r linear E ⇒ gas amplifica2on 26 eV needed (Ar) per e/ion pair 3.65 eV (Si) needed per e/h pair 94 e/ion pairs per cm ~10 6 e/h pairs per cm (20 000/250µm) intrinsic amplifica2on typ. 10 5 no intrinsic amplifica2on typ. noise: > 3000 e- (ENC) typ. noise: 100 e- (pixels) to 1000 e- (strips) 11 N. Wermes, Desy Kolloquium 2016

Some basics: How the signal is generated in a detector ... how does a moving charge couple to an electrode ? • respect Gauss’ law and find Shockley- Ramo theorem (Shockley: J Appl.Phys 1938, Ramo: 1939) induc2on (weigh2ng) poten2al dQ = q ~ r � w d ~ r they determine how charge movement couples to a specific electrode i S = − dQ dt = q ~ E w ~ v weigh2ng field 12 N. Wermes, Desy Kolloquium 2016

Normal Field and WeighRng Field readout readout electrode electrode Kolanoski, Wermes 2015 i S = − dQ dt = q ~ E w ~ v Recipe: To compute the weigh2ng field of a readout electrode i, set voltage of electrode i to 1 and all other electrodes to 0. 13 N. Wermes, Desy Kolloquium 2016

Examples parallel plate detector (gas filled) parallel plates with space charge (i.e. Si) E w = − 1 E w = − 1 ~ d ~ e x ~ d ~ e x velocity (v=µE) almost const. v e = ˙ x e = − µ e E ( x ) = + µ e ( a − bx ) x h = ˙ = − µ h ( a − bx ) par2cle + Z T − t(ns) i ( t ) dt = Q + Q tot = s + Q − s = ± e 14 N. Wermes, Desy Kolloquium 2016 0

Examples parallel plate detector (gas filled) parallel plates with space charge (i.e. Si) E w = − 1 E w = − 1 ~ d ~ e x ~ d ~ e x velocity (v=µE) almost const. v e = ˙ x e = − µ e E ( x ) = + µ e ( a − bx ) x h = ˙ = − µ h ( a − bx ) dangerous e.g. in CdTe 50% almost signal no signal + Z T − i ( t ) dt = Q + Q tot = s + Q − s = ± e 15 N. Wermes, Desy Kolloquium 2016 0

transient current Current pulse measurements: TCT technique e single crystal diamond is like a parallel plate detector filled with a dielectric w/o space current charge diamond 1mm pn – Diode silicon - same weigh2ng field - different electric field Fink, Lodomez, Krüger, Pernegger, Weilhammer, NW, NIM A 565 (2006), 227 e h Si => measurement of E-field 16 N. Wermes, Desy Kolloquium 2016

Signal development in a wire configuraRon E(r) ~ 1/r => gas amplifica2on => “signal” current starts only close to the wire • (*) Shockley-Ramo-recipe: • 1 φ W ( r ) = − ln r /b E W ( r ) = 1 ~ ~ e r ln b ln b r a a which fulfills (*) far away from wire (a=10 µm, b=10 mm) wire chamber signals are governed by away moving ions 17 near wire N. Wermes, Desy Kolloquium 2016

Structured electrodes signals are induced on BOTH (ALL) electrodes => exploit for second coordinate readout y x V=1 V=0 V=0 wire chamber with cathode R/O Q Q Q double sided silicon strip detector 18 N. Wermes, Desy Kolloquium 2016

How to meet the LHC rate and radiaRon challenges ... q par2cle rates ( L = 10 34 cm -2 s -1 ) note: heavy ions: L = 10 27 cm -2 s -1 § bunch crossing every 25 ns § N trk = σ L = 100 mb × 10 34 cm -2 s -1 × 120 ≈ 10 11 tracks/s in 4π = 10 6 × LEP § @ r = 5cm => 9.5 tracks/cm 2 /25 ns, but only 10 -4 per pixel (100x100 µm 2 ) q radia2on level (@ r = 5cm, per detector life2me) § total ionizing dose (TID) = energy/mass (J/kg) = 100 Mrad -> 1 Grad § non ionizing fluence (NIEL, breaks the la‚ce) = 10 15 par2cles per cm 2 -> 10 16 cm -2 § effects: ageing on wires, la‚ce damage, glue brikle, electronics, … 19 N. Wermes, Desy Kolloquium 2016

How to meet the LHC rate and radiaRon challenges ... q way out ATLAS TRT § gas-filled detectors with small cells § 2ming precision ≪ 25 ns § solid state detectors - micro structuring => finest granularity - but: sensi2ve to radia2on CMS Tracker (200 m 2 ) 20 N. Wermes, Desy Kolloquium 2016

Example for “Rming”: RPCs (resisRve plate chambers) q target: high Rming precision (trigger and 2ming chambers, e.g. ATLAS Muon Spectrometer) q gas filled chambers w/ large signals § operated in avalanche mode (≥10 kV/cm) or in streamer mode (~100kV/cm) q gas with high ionisa2on density and high quenching efficiency Kolanoski, Wermes 2015 e.g. 94.7% C 2 H 2 F 4 + 5% iC 4 H 10 + 0.3% SF 6 “avalanche” <-> “streamer” v drij <-> photon emission 10 5 m/s <-> 10 6 m/s Trigger RPC Timing RPC el. Feld 20-50 kV/cm ~100 kV/cm op. mode avalanche streamer signal < 10pC < 100pC quench 2mes shorter longer σ t 1 ns 50 ps efficiency 98% 75% 21 N. Wermes, Desy Kolloquium 2016

... “special” at the LHC: the radiaRon environment 10 MeV p 24 GeV p 1 MeV n longitudinal (nm) conduc2on band transverse (nm) valence band threshold energy to remove an atom: Si: 25 eV, diamond: 43 eV trapping charged genera2on recombina2on center defects 22 N. Wermes, Desy Kolloquium 2016

Much progress in understanding radiated Si-sensors e- trap posiRve space charge E(eV) uncharged @ RT +/- charged @ RT higher conc. aser proton than neutron irradia2on conduction band depends on oxygen content 1.12 E(30K)+ +/++ BD=bistable donor (e- trap) BD VO - /0 1.0 posiRve space charge B 0/++ strongly produced BD in oxygen rich DOFZ material A E4 - 0.8 triple vacancy, small cluster V 2 - /0 negaRve space charge tr E5 -- 0/ - -> high leakage current nega I P E F -> high leak 0.6 V 2 O complex (?) negaRve space charge moves with H(152K)0/ - causes leakage current , +/0 C i O i strongly produced in oxygen lean STFZ changes H(140K)0/ - 0.4 H(116K)0/ - to N eff extended acceptor defects +/0 I P produced equally by n,p negaRve space charge 0.2 -> reverse annealing § most defects show linear fluence dependence § cooling helps to keep I leak and rev. annealing valence band smaller § N eff changes extended defects (cluster) point defects Radu et al., J. Appl. Phys. 117, 164503 (2015) RD50, M. Moll et al., PoS (Vertex 2013) (2013) 026 23 N. Wermes, Desy Kolloquium 2016