1. Gossipo-3: a prototype of a Front-end Pixel Chip for Read-out of Micro-Pattern Gas Detectors. TWEPP-09, Paris, France. September 22, 2009. Christoph Brezina 2, Klaus Desch 2, Harry van der Graaf 1, Vladimir Gromov 1, Ruud Kluit 1, Andre Kruth 2, Francesco Zappon 1 1 National Institute for Subatomic Physics (Nikhef), Amsterdam, 2 Institute of Physics, Bonn University Vladimir Gromov

2. TWEPP-09 V.Gromov222/09/09 Outline  Read-out of Micro-pattern gas detectors  Gossipo-3 prototype: functionality and features  Design and performance of basic circuits  Plans and perspectives

3. TWEPP-09 V.Gromov322/09/09 Micro-pattern gas detectors: layout and features - particle track image (projection) - 3D track reconstruction - - no sensor leakage current compensation - low parasitic capacitance (less than 10fF) - micro-discharges in avalanche gap Cluster3 Cathode (drift) plane Gas Amplification Structure Cluster2 Cluster1 Readout chip 1mm …1m → Drift gap 400V 50um → Avalanche gap Gas-avalanche detector combining a gas layer as signal generator with a CMOS readout pixel array Front-end circuit Cpar

4. TWEPP-09 V.Gromov422/09/09 Readout Chip for MPGDs 2007: GOSSIPO-2 - technology: 0.13μm CMOS - array: 16 x 16, 256 pixels - pixel: 55 um x 55 um - active area: 0.88mm 2 - event clock: 40MHz - high resolution TDC-per-pixel architecture (bin=1.8 ns) - range: 350ns (4-bits @ 25ns) 2009: GOSSIPO-3 / GOSSIPO-4 - technology: 0.13μm CMOS - array: 32 x 32, 1024 pixels - pixel: 60μm x 60μm - active area: 3mm 2 - event clock: 40MHz - accuracy (bin size): 1.73ns - range: 102μs (12-bits @ 25ns) - ToT accuracy: σ = 200e - (27ns) - ToT range: 6.4μs (8-bits @25ns) - Hit Counting mode - noise: σ = 70e - - fast response: 20ns (rise time) - power (goal): 100mW/cm 2 (3μW/ch) GOSSIPO-2 GOSSIPO-3 GOSSIPO-4

5. TWEPP-09 V.Gromov522/09/09 Gossipo-3: MPW prototype Features each pixel measures: - hit arrival time → cluster’s drift time - time-over-threshold → charge deposit - number of hit (24 bits) triggering options: - external common stop read-out options: - serial read-out of all the pixels other functionalities: - auto clear (no stop signal after expected latency) - INGRID & pixel analog signal monitors Time mode Hit Counting mode

6. TWEPP-09 V.Gromov622/09/09 TDC with local oscillator Hit signal Local oscillator output (F fast = 640MHz) Start Stop Clock signal (F slow = 40MHz). Trigger signal Stop N slow N fast Time = N slow / freq slow + N fast /freq fast Start Stop Local oscillator Pixel_1 Hit 40MHz Clock Bus Out Power ≈ Hit_Rate ● 6 μW / MHz per channel → 0.16 μW @ 27.2KHz

7. TWEPP-09 V.Gromov722/09/09 Gossipo-3: the pixel Layout of the pixel LFSR = Counters (data taking) or LFSR = Shift registers (data read-out) Control signals - Clock - TRIGGER (common stop) - TOKEN - RESET Preamp Discr. control Local fast oscillator (600MHz) Local fast oscillator (600MHz) 4 bit Fast counter 8 bit ToT counter 12 bit Slow counter 6 bit Pixel configuration Memory Threshold DAC pad -Threshold - Mask Time / Counting HIT Block diagram of the pixel oscillator Logic: counters & control Preamp & comparator DAC

8. TWEPP-09 V.Gromov822/09/09 Diagrams (TIME mode) Preamp_out Hit (asynchronous) Clock (40MHz) Counter Fast Counter ToT Trigger Counter Slow Token Reset Data taking phase (LFSR = Counter) Data read-out Phase (LFSR = Shift Registers) ToT State diagram

9. TWEPP-09 V.Gromov922/09/09 Local oscillator :basic limitations NAND EN OUT Delay = T fast /2 = Function (Temp, Vdd) EN T fast (1.72 ns) OUT - 12% / 100mV 2% / 10 ◦ C Channel-to-channel statistical spread is 4% VDD effectTEMP effect 0ns…T slow (25 ns) 0…15 (4-bit TDC) 2.2 2.1 2 1.9 1.8 1.7 1.6 1.05 1.1 1.15 1.2 1.25 1.3 Power supply voltage, Volts 0 20 40 60 80 100 2.2 2.1 2 1.9 1.8 1.7 Temperature, ◦ C T fast,ns

10. TWEPP-09 V.Gromov1022/09/09 Local oscillator : reproducibility ∆t max = 0.5ns (accumulated) Pixel-to-pixel mismatchPixel-to-pixel mismatch σ(∆T fast /T fast ) ≈ 2% ● (N●W ● L) -0.5 Monte Carlo simulations. vdd_osc Nominal situation Upper limitLow limit 0.61 V 1.72 ns 0.76 V 1.73 ns 1.13 ns2.26ns 1.1 V 1.72 ns T fast =1.73ns Process variationProcess variation clock period =25ns

11. TWEPP-09 V.Gromov1122/09/09 Local oscillator: frequency tunability Opam p Off-chip cap 10μF 4bit DAC Bandgap Current Reference with Temp. Gradient vdd=1.2V 1.14k 2k U vdd_osc = 0.6V…1.1V Functionality - tunes oscillation frequency - power supply ripple rejection - temperature compensation Common on-chip LDO: voltage regulatorCommon on-chip LDO: voltage regulator Uref

12. TWEPP-09 V.Gromov1222/09/09 The front-end Time Uin Uin + 70mV Uin + Qin / Cfb -Time ● Isat Tfb /Cfb exp[-Time/(Cfb ● Ron Tfb )] Uout Tfb in saturationTfb in triode Features - low time jitter, time walk - constant current feedback (1nA) - high gain (1mV / fF) U out 170fF To Comp C par ≈ 10 fF Tfb Cfb =Cds+Cdg+Cdb+Cdj ≈ 1 fF Input pad (22μm x 22μm) OPAMP Discharge protection Ib = 6nA 2.4/2.4 0.48/2.4

13. TWEPP-09 V.Gromov1322/09/09 The front-end circuit Main specifications:Main specifications: - low power consumption (3μW/ch) - fast response (20ns) - low noise (σ =70 e - ) - channel-to-channel threshold spread (σ =70e - no equalization) (σ = 5e - with equalization)

14. TWEPP-09 V.Gromov1422/09/09 Time-over-threshold measurements Uout charging discharging Qin, e - ToT, ns Q max =28 000e - 0.13ns / e - Time, sec C par =10fF Cfb= 1fF OPAMP Ib = 1nA Qin Qin=400e - … 28000e - Features - wide dynamic range (up to 28ke - ) - resolution σ = 200e - (27ns) - poor channel-to-channel uniformity (spread is 20%) ToT threshold 0 1μ 2μ 3μ 4μ 5μ 0.4 0.3 0.2 0.1 0 Uout,V

15. TWEPP-09 V.Gromov1522/09/09 Discharge protection C SP = 20fF SiNProt (7μm thick) InGrid Q dis = U HV ●C SP = 8pC U HV = - 400V High resistive protection layer C GR = 25pF InGrid U HV = - 400V Read-out chip 1.4cm x 1.4cm Q dis = U HV ●C GR = 10 000pC Read-out chip 1.4cm x 1.4cm NO protection layerNO protection layerWith protection layerWith protection layer Qdis SiNProt layer limits the size the discharge 50μm

16. TWEPP-09 V.Gromov1622/09/09 Protection device: Q dis = 8pC n+n+ n+n+ P-well in_preamp ( Udc=+0.424V) GND Standard NFET (W=1μm, L=0.24 μm) U in_preamp No protection With protection ← -1V (no damage of the MOSFET’s) ← -7.5V (the MOSFET’s will be damaged) I MOS_channel p+p+ GND I diode n-type inversion layer Features - small area (W=1μm, L=0.24μm) - low parasitic capacitance (1.3fF) - negligible leakage current (250pA)

17. TWEPP-09 V.Gromov1722/09/09 Conclusions  Gossipo-3 is a prototype of a Front-end Pixel Chip (0.13μm CMOS technology) for Read-out of Micro- Pattern Gas Detectors.  Every pixel is equipped a high resolution TDC (1.7ns) covering dynamic range up to 100us and a ToT counter to evaluate the charge deposit.  The chip can also operate in hit counting mode.  Gossipo-3 is taped-out for MPW production run (September 21).