1 / 49

GOSSIP : a vertex detector combining a thin gas layer as signal generator with a

GOSSIP : a vertex detector combining a thin gas layer as signal generator with a CMOS readout pixel array. GOSSIP. G as O n S limmed SI licon P ixels. Time Projection Chamber (TPC): 2D/3D Drift Chamber The Ultimate Wire (drift) Chamber. track of charged particle. E-field

fatima-ortega
Download Presentation

GOSSIP : a vertex detector combining a thin gas layer as signal generator with a

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. GOSSIP: a vertex detector combining a thin gas layer as signal generator with a CMOS readout pixel array GOSSIP Gas On SlimmedSIlicon Pixels

  2. Time Projection Chamber (TPC): 2D/3D Drift Chamber The Ultimate Wire (drift) Chamber track of charged particle E-field (and B-field) Wire plane Wire Plane + Readout Pads Pad plane

  3. Let us eliminate wires: wireless wire chambers 1996: F. Sauli: Gas Electron Multiplier (GEM)

  4. 1995 Giomataris & Charpak: MicroMegas Ideally: a preamp/shaper/discriminator channel below each hole….

  5. The MediPix2 pixel CMOS chip 256 x 256 pixels pixel: 55 x 55 μm2 per pixel: - preamp - shaper - 2 discr. - Thresh. DAQ - 14 bit counter - enable counting - stop counting - readout image frame - reset We apply the ‘naked’ MediPix2 chip without X-ray convertor!

  6. Cubic drift volume: 14 x 14 x 14 mm3 Cathode (drift) plane: - 700 V Drift space: 15 mm (gas filled) Micromegas: - 350 V Baseplate MediPix2 pixel sensor Brass spacer block Printed circuit board Aluminum base plate cosmic muon Very strong E-field above (CMOS) MediPix!

  7. 55Fe, 1s No source, 1s 55Fe, 10s 14 mm Friday 13 (!) Feb 2004: signals from a 55Fe source (220 e- per photon); 300 m x 500 m clouds as expected The Medipix CMOS chip faces an electric field of 350 V/50 μm = 7 kV/mm !! We always knew, but never saw: the conversion of 55Fe quanta in Ar gas

  8. Single electron efficiency • no attachment • homogeneous field in • avalanche gap • low gas gain • simple exponential grown • of avalanche •  • No Curran or Polya • distributions but simply: Prob(n) = 1/G . e-n/G Eff = e-Thr/G Thr: threshold setting (#e-) G: Gas amplification

  9. New trial: NIKHEF, March 30 – April 2, 2004 Essential: try to see single electrons from cosmic muons (MIPs) Pixel preamp threshold: 3000 e- (due to analog-digital X-talk) Required gain: 5000 – 10.000 New Medipix New Micromegas Gas: He/Isobutane 80/20 !Gain up to 30 k! He/CF4 80/20 …… It Works!

  10. He/Isobutane 80/20 Modified MediPix Sensitive area: 14 x 14 x 15 mm3 Drift direction: Vertical max = 15 mm

  11. He/Isobutane 80/20 Modified MediPix Sensitive area: 14 x 14 x 15 mm3 Drift direction: Vertical max = 15 mm

  12. He/Isobutane 80/20 Modified MediPix δ-ray? Sensitive area: 14 x 14 x 15 mm3 Drift direction: Vertical max = 15 mm

  13. MediPix modified by MESA+, Univ. of Twente, The Netherlands Non Modified Modified Pixel Pitch: 55 x 55 μm2 Bump Bond pad: 25 μm octagonal 75 % surface: passivation Si3N4 New Pixel Pad: 45 x 45 μm2 Insulating surface was 75 % Reduced to 20 %

  14. Vernier, Moire, Nonius effect Pitch MediPix: 55 μm Pitch Micromegas: 60 μm Periodic variation in gain per 12 pixels Non-modified MediPix Modified MediPix has much less Moire effect Focussing on (small) anode pad Continues anode plane is NOT required Reduction of source capacity! No charge spread over 2 or 4 pixels

  15. De-focussing Modified focusing De-focussing focusing Non Modified InGrid: perfect alignment of pixels and grid holes! Small pad: small capacitance!

  16. ‘Micromegas’ INtegrate Micromegas GRID and pixel sensor InGrid By ‘wafer post processing’ at MESA+, Univ. of Twente

  17. Integrate GEM/Micromegas and pixel sensor: InGrid ‘GEM’ ‘Micromegas’ By ‘wafer post processing’

  18. For KABES II, there are two options. • The TPC with transverse drift option would need strips rather than pixels. • But it could be interesting to have an InGrid-like integrated mesh. • The thin Si or CMOS+gas option would need a very high rate capability. • CAST (CERN Axion Solar Telescope) seems to be a more straightforward application. • It simply requires a possibility of triggering a common stop. • This is why Esther Ferrer-Ribas, from CAST, will join us. • - The polarimetry application (challenging Belazzini) is very interesting • for people from the Astrophysics division. The requirement is very similar to CAST's. • - The MicroTPC might have applications in nuclear physics or in Babar, for instance. • - There are other applications (X-ray beam monitor for SOLEIL) which I can talk about tomorrow. • - The protection issue is essential in all Micromegas applications.

  19. ! With 1 mm layer of (Ar/Isobutane) gas we have a fast TPC! • thick enough for 99 % MIP detection efficiency • thin enough for max. drift time < 25 ns (LHC bunchX) • Replace {Si sensor + amplifier} by gas layer: •  tracker for intense radiation environment After all: until 1990 most vertex detectors were gas detectors! Si solved granularity problems associated with wires.

  20. GOSSIP: Gas On Slimmed SIlicon Pixels MIP MIP Micromegas (InGrid) Cathode foil CMOS pixel array CMOS pixel chip Drift gap: 1 mm Max drift time: 16 ns

  21. Essentials of GOSSIP: • Generate charge signal in gas instead of Si (e-/ions versus e-/holes) • Amplify # electrons in gas (electron avalanche versus FET preamps) • Then: • No radiation damage in depletion layer or pixel preamp FETs • No power dissipation of preamps, required for Si charge signals • No detector bias current • 1 mm gas layer + 20 μm gain gap + CMOS (almost digital!) chip • After all: it is a TPC with 1 mm drift length (parallax error!) Max. drift length: 1 mm Max. drift time: 16 ns Resolution: 0.1 mm  1.6 ns

  22. Ageing Efficiency Position resolution Rate effects Radiation hardness HV breakdowns Power dissipation Material budget

  23. Ageing Remember the MSGCs…… • Little ageing: • the ratio (anode surface)/(gas volume) is very high w.r.t. wire chambers • little gas gain: 5 k for GOSSIP, 20 – 200 k for wire chambers • homogeneous drift field + homogeneous multiplication field • versus 1/R field of wire. Absence of high E-field close to a wire: • no high electron energy; little production of chemical radicals • Confirmed by measurements(Alfonsi, Colas) • But: critical issue: ageing studies can not be much accelerated!

  24. Efficiency • Determined by gas layer thickness and gas mixture: • Number of clusters per mm: 3 (Ar) – 10 (Isobutane) • Number of electrons per cluster: 3 (Ar) - 15 (Isobutane) • Probability to have min. 1 cluster in 1 mm Ar: 0.95 • With nice gas: eff ~ 0.99 in 1 mm thick layer should be possible • But……. • Parallax error due to 1 mm thick layer, with 3rd coordinate 0.1 mm: • TPC/ max drift time 16 ns; σ = 0.1 mm; σ = 1.6 ns: feasible! • Lorentz angle • We want fast drifting ions (rate effect) • little UV photon induced avalanches: good quenching gas

  25. Position resolution 0 Q 20 ns • Transversal coordinates limited by: • Diffusion: single electron diffusion 0 – 40/70 µm • weighed fit: ava 20/30 µm • 10 e- per track: σ = 8/10 µm • pixel dimensions: 20 x 20 – 50 x 50 μm2 • Note: we MUST have sq. pixels: no strips (pad capacity/noise) • Good resolution in non-bending plane! • Pixel number has NO cost consequence (m2 Si counts) • Pixel number has some effect on CMOS power dissipation • δ-rays: can be recognised & eliminated • 3rd (drift) coordinate • limited by: • Pulse height fluctuation • gas gain (5 k), pad capacity, # e- per cluster • With Time Over Threshold: σ = 1 ns ~~ 0.1 mm

  26. Rate effects 0 Q 20 ns SLHC @ 2 cm from beam pipe: 10 tracks cm-2 25 ns-1 400 MHz cm-2! • ~10 e- per track (average) • gas gain 5 k • most ions are discharged at grid • after traveling time of 20 ns • a few percent enter the drift space: time • Some ions crossing drift space: takes 20 – 200 μs! • ion space charge has NO effect on gas gain • ion charge may influence drift field, but this does little harm • ion charge may influence drift direction: change in lorentz angle ~0.1 rad • B-field should help

  27. Data rate Hit Pixel (single electron) data: 8 bit column ID 8 bit row ID 4 bit timing leading edge 4 bit timing trailing edge total 24 bits/hit pixel 100 e-/ 25 ns cm2 380 Gb/s per chip (2 x 2 cm2) Cluster finding: reduction factor 10: 40 Gb/s Horisberger: Data rate, DAQ, data transmission is a limiting factor for SLHC Required: rad hard optical links with 1 mm3 light emittors per chip!

  28. Radiation hardness • Gas is refreshed: no damage • CMOS 130 nm technology: ? TID • ? NIEL • ? SEU: design/test • need only modest pixel input stage • How is 40 Gb/s hit pixel data transferred? • need rad hard optical link per chip!

  29. HV breakdowns: InGrid issue 1) High-resistive layer 3) ‘massive’ pads 2) High-resistive layer 4) Protection Network

  30. Power dissipation • For GOSSIP CMOS Pixel chip: • Per pixel: • - input stage (1.8 μA/pixel) • monostable disc/gate • Futher: data transfer logic • guess: 0.1 W/cm2 •  Gas Cooling feasible!

  31. Detector Material budget ‘Slimmed’ Si CMOS chip: 20 μm Si Pixel resistive layer 1 μm SU8 eq. Anode pads 1 μm Al Grid 1 μm Al Grid resistive layer 5 μm SU8 eq. Cathode 1 μm Al

  32. Gas instead of Si • Pro: • no radiation damage in sensor • modest pixel input circuitry • no bias current, no dark current (in absence of HV breakdowns..!) • requires (almost) only digital CMOS readout chip • low detector material budget • Typical: Si foil. New mechanical concepts: • self-supporting pressurised co-centric balloons • low power dissipation • (12”) CMOS wafer  Wafer Post Processing  dicing 12” pcs • no bump bonding • ‘simple’ assembly • operates at room temperature • less sensitive for X-ray background • 3D track info per layer • Con: • Gas chamber ageing: not known at this stage • Needs gas flow (but can be used for cooling….)

  33. How to proceed? • InGrid 1 available for tests in October: • rate effects (all except change in drift direction) • ageing (start of test) •  Proof-of-principle of signal generator: Xmas 2004! • InGrid 2: HV breakdowns, beamtests with MediPix (TimePix1 in 2005) • TimePix2: CMOS chip for Multi Project Wafer test chip • GOSSIPO ! Dummy wafer

  34. Essential Ingredients of GOSSIP CMOS chip • RATE • Assume application in Super LHC: • Bunch crossing 25 ns • 10 tracks per (25 ns cm2) • 10 e- per track (average: Landau fluct.) • So: 4 MHz/mm2 tracks!, 40 MHz/mm2 single electrons!

  35. Q 10 - 20 ns Chargesignal on pixel input pad • Signal shape is well defined and uniform • No bias current, no dark current • Signal is subject to exponential distribution • may be large, but limited by • chamber ageing • space charge (rate) effects

  36. Input Pad capacity • preamp stage, noise, power • Input pads may be small: focusing • Too small pads: chamber ageing • capacity to neighbors & metal layers • capacity due to gas gain grid • Pixel size: 50 x 50 - 20 x 20 μm2 • 4 fF seems feasible

  37. Time resolution • preamp-disc speed, noise, power • Measurement 3rd coordinate: σdrift time: 25/16 = 1.5 ns • Time over threshold: slewing correction • drift time related to BX • Record: leading edge - BX • trailing edge - BX • BX ID

  38. Data Readout ALL data: 80 MB s-1 mm-2 ( 15 GB/s per chip) Maybe possible in 10 years from now: - optical fibre per chip - Vertex can be used as trigger For SLHC: Use BX ID info (typical Vertex policy) - tell BX ID to all (Rows/Columns/Pixels) - get data from (Row/Column/Pixel)

  39. Gossipo • MultiProjectWafer submit in 130 nm CMOS technology • Test of essential GOSSIP ingredients: • Low power, low input capacity preamp/shaper/discriminator • 1.5 ns TDC (per discriminator output) • Data transfer • Maybe not all of this in a first submit • Maybe with less ambitious specifications

  40. Amplifier-shaper-discriminator • How to apply a test pulse? • using gas gain grid (all channels fire) • capacitive coupling test pulse strip • reality: with a gas gain grid(!) • What to do with the output? • (bonded) contact: digital feedback?! • TDC + DAQ? • TDC • - 1.5 ns clock: derived on-board from 40 MHz BX clock? • 640 MHz clock distribution (per pixel?!) • DLL?

  41. (My) goal of this meeting: • Are there any showstoppers in this stage? • can we define a Gossipo concept (block diagram)? • Can we estimate the amount of work?

More Related