GOSSIP a new vertex detector for ATLAS Harry van der Graaf NIKHEF, Amsterdam Univ. of Bonn, Nov 23, 2006

New gaseous detectors: the application of pixel sensors as direct anode NIKHEFAuke-Pieter Colijn Alessandro Fornaini Harry van der Graaf Peter Kluit Jan Timmermans Jan Visschers Maximilien Chefdeville Saclay CEA DAPNIAPaul Colas Yannis Giomataris Arnaud Giganon Univ. Twente/Mesa+Jurriaan Schmitz CERN/Medipix ConstmEric Heijne Xavie Llopart Michael Campbell Thanks to: Wim Gotink Joop Rovenkamp Arnaud Giganon Harry van der Graaf, NIKHEF, Amsterdam University of Bonn Oct 14, 2004

GOSSIP: Gas On Slimmed SIlicon Pixels CMOS pixel array MIP InGrid Drift gap: 1 mm Max. drift time: 16 ns MIP CMOS pixel chip ‘slimmed’ to 30 μm Cathode foil

Si (vertex) track detector GOSSIP CMOS chip Si depletion layer V bias Si strip detectors Si pixel detectors MAPs Gas: 1 mm as detection medium 99 % chance to have at least 1 e- Gas amplification ~ 1000: Single electron sensitive All signals arrive within 16 ns Cluster3 Cathode (drift) plane Integrated Grid (InGrid) Cluster2 Cluster1 Slimmed Silicon Readout chip Input pixel 1mm, 100V 50um, 400V 50um

April 2004Micromegas + MediPix 2 NIKHEF/Saclay/Univ. Twente : MediPix2 pixel sensor Brass spacer block Printed circuit board Aluminum base plate Micromegas Cathode (drift) plane 55 Fe Baseplate Drift space: 15 mm MIPs No source, 1s 55 Fe, 1s He/Isobutane 80/20 Modified MediPix δ-ray! 14 mm

Integrate Micromegas and pixel sensor: InGrid ‘wafer post processing’ by Univ. of Twente, MESA+ ’ “there is plenty of room at the top”

Prototypes hidden pillars!

Energy resolution in Argon IsoC 4 H 10 80/20 Observation of two lines: K 5.9 keV K 6.4 keV FWHM of the K α distribution 16.7 % Gain fluctuations < 5% Very good energy resolution: Very precise dimensions d < 0.1 μm May 2005

A-Si not adequate? Then TwinGrid

Gas instead of Si Pro Low mass detector! - low power: 2 μW/pixel (analog), 0.6 μW/pixel (digital) Total 2.6 μW/pixel  0.1 W/cm 2 due to: - extremely low source capacitance (10 fF) - fast & arbitrary large charge signals - no bias current  little material required for power & cooling - Thinning (Slimming) of CMOS pixel chip to 50 μm detection layer: only 0.06 % radiation length  new vertex detector: 5 – 10 layers instead of 3 Input pad Substrate C fb =1fF Ground plane Output M1 M2 M3 M6 LM Ground

Gas instead of Si Pro - a GOSSIP detector measures a track segment instead of a point-in-space: - single-electron sensitive (eff > 95 %) - ~ 10 e- along 1 mm track length - spatial resolution: 50 μm / √10 = 15 μm 14 mm 3 - radiation hardness - gas is flushed - CMOS chip (130, 90, 45 nm technology): sufficiently radiation hard for SLHC - very low sensitivity for neutrons, X-rays and gammas - ‘simple’ CMOS chip: - modest (small area) analog input circuits - no bias current: simpeler input circuit - pixel area available for data storage & communication - Cheap

Gas instead of Si Con - GOSSIP has 1 mm detection layer: - parallax error: elimination requires drift time measurement - with single-electron measurement: track segment data per layer! - Gas-filled detector: - chamber ageing (deposit on electrodes) - discharges (sparks, too large signals) ruin CMOS chip  showstoppers !

CMOS Chip protection against - discharges - sparks - HV breakdowns - too large signals Emperical method: Try RPC principle Amorph Si (segmented) Silicon Protection: SiProt

- RPC principle: reduction of local E-field - Avalanche charge: electrostatic induction towards input pad - Specific resistance: - high enough to ‘block’ avalanche charge - low enough to flow signal current - layer thickness 4 μm, R vol > 0.2 – 100 GΩ/cm Technology A-Si deposit: standard wafer post processing, but wafers may get too hot Univ. of Neuchatel/IMT/P. Jarron (CERN) uses this for integrated X-ray sensor/convertor on MediPix Test: put Thorium in gas: Radon α-decays: - large (proportional) signals - Discharges: like short circuits plasma A-Si

The SiProt chamber Low temperature deposition (< 250°C) of a 4 μm thick a-Si layer of Ω.cm resistivity Experimental setup: –1 bare anode and 1 a-Si covered anode with Micromegas on top –Gain curve with an Iron 55 source –Induce discharges by means of 5 MeV alphas from Th source in gas –Record grid signals Micromegas grids prot. anode un-prot. anode Aluminum a-Si To digital scope or pre-amplifier

SiProt chamberTh container Digital scope cathode

Discharge Signals study No preamplifier Ar 20 % iC 4 H 10 Signals from ~ 5 MeV alphas Fast digital scope

UN PROT - no hot plasma on pixel input pads - reduced charge & current Looks like it works! Next: try on Medipix chips Discharge signals: short-circuit between grid and anode due to plasma

55 Fesource Look at the pulses from a (calibrated) preamplifier (low grid voltage) Look at the current flowing through the power supply (high grid voltage) No sparks up to 570 V on the grid ! Next step: SiProt (and InGrid) on Medipix, TimePix from current from pulse height Gain measurement

Ageing Ageing of a GOSSIP detector versus wire chambers: - Ratio of anode surface/chamber volume: - thin wire surface versus anode plane (~20x) - Low gas gain (1 k) due to fast signal and low source capacity (~20x) total factor: 400 x So: application as GOSSIP vertex detector in Super LHC MIP/cm 2 seems feasible First try

Ageing: remember the MSGCs….

Irradiation with 8 keV X-rays: No rate effects up to anode current density of 0.2 / mm 2  very fast track counting possible! Irradiation with 8 keV X-rays: No rate effects up to anode current density of 0.2 μA / mm 2  very fast track counting possible! After 0.3 Coulomb/mm2:  (eq. 3.7 x MIPs/cm 2 !!) deposit of carbon polymer on anode is clearly visible. Micromegas is clean (?!) Little deposit on cathode, and…… Chamber still worked!

Ongoing projects

Very low (parasitic) capacitance at the input (C par → 10fF). C par = 10fF…50fF Coaxial-like layout of the input interconnection. Parasitic metal-to-metal fringe capacitances. C fb R fb C par I in (t) Q in Output Open loop voltage gain of the OPAMP A Input pad Substrate C fb =1fF Ground plane Output M1 M2 M3 M6 LM Ground GOSSIPO-1: test of preamp-shaper-discriminator for GOSSIP ‘MultiProjectWafer’ in 0.13 μm technology

Triple well layout: isolation of digital and analog sections Guard rings GND GND_ana VDD_ana P-type substrate P-well N-well Analog P-type FET area Analog N-type FET area Digital N-type FET area substrate current GND GND_ana VDD_ana

- match extreme small source capacity: 15 fF - peaking time: 40 ns - noise (expected: 60 e- input eq.) - power: 2 μW/pixel (!) MultiProject Wafer: Vladimir Gromov/NIKHEF CERN Micro-electronics group - Input noise eq. reached - No effect of digital switching within pixel GOSSIPO chip Submitted December 2005.

test of preamp-shaper-discriminator and 700 MHz TDC per pixel 0.13 μm technology containing 16 x 16 pixels Submission Nov 29, 2006 Can be used for GOSSIP demo ! GOSSIPO-2

New mechanics + cooling concepts for Gossip - As little as possible material - detector consists of foil! - less power required (  less cooling) w.r.t. Si string: power, chip support, cooling ‘laundry line’

- Ladder strings fixed to end cones - Integration of beam pipe, end cones & pixel vertex detector - 5/10 layers (0.06 % rad. length each!) seems feasible Virtual goal: ATLAS pixel upgrade

Stainless steel tube: - string - power - CO 2 cooling Gossip chip + InGrid drift gap cathode foil ladder cross section data lines (Cu/kapton) casted aluminium ladder side view ladder top view

First practical GOSSIP with CMS Vertex Pixel FE chip: PSI 46 (+ ATLAS FE pixel chip?) - apply A-Si protection layer - apply InGrid - mount Gossips on pcb: ‘ beam telescope’ - Testbeam 1 st half 2007 PSI, Univ. Nijmegen, NIKHEF,

Gossip projects at NIKHEF Univ. Twente/ Saclay CERN PSI EUDET - Discharge protection - InGrid/TwinGrid/TripleGrid - Construction of detector: MediPix2 + SiProt + InGrid - Construction of detector: TimePix + SiProt + InGrid - Beam Telescope with CMS PSI 46 pixel chip - Ageing studies - CO 2 cooling

Gossip: the electronic bubble chamber NIKHEFHarry van der Graaf Jan Timmermans Jan Visschers Maximilien Chefdeville Vladimir Gromov Ruud Kluit Fred Hartjes Els Koffeman Martin Fransen Saclay CEA DAPNIAPaul Colas Yannis Giomataris Dan Burke Univ. Twente/Mesa+Jurriaan Schmitz Cora Salm Sander Smits Victor Blanco Carballo CERNErik Heine Medipix Consortium Thanks to: Wim Gotink Joop Rovenkamp

Sr-90 β-source 1.2 mm