Pixel detectors:
status, plans & applications of the gaseous
GridPix/Gossip detector
anda new vacuum electron multiplying
detector
Harry van der Graaf, Nikhef, Amsterdam
Monday Sept 5 KEK
Thursday Sept 7 Kamioka

Gossip

1 mm

GridPix: readout of TPC ionisation charge

Gossip: Gas On Slimmed SIlicon Pixels
Essential: thin gas layer (1 mm)
Gossip: replacement of Si tracker

He/Isobutane
80/20
Modified MediPix

14 mm

δ-ray!

Efficiency for
detecting single
electrons:< 95 %

GridPix:
the electronic bubble chamber
April 2004

Application of MicromegasNew:- pixel chip as active anode readout- MEMS made Micromegas: Integrated Grid InGrid

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- resetWe apply the ‘naked’ MediPix2 chip
without X-ray convertor!

Applied chips:
Medipix-2
TimePix
PSI-46
FE-I4TimePix-3: underway: submission
Dec 2011

Wafer post-processing:InGrid
Hex / Pillars

Grids
Siliconwafer

HV biasing

InGrid: an Integrated Grid on Si (wafers or chips)• perfect alignment of grid holes and pixel pads
• small pillars Ø, hidden pillars, full pixel area coverage• Sub-micron precision: homogeneity• Monolithic readout device: integrated electron amplifierFull post-processing of a TimePix• Timepix chip + SiProt + Ingrid:

14 mm
MESA+

“Uniform”
IMT
Neuchatel

Charge mode

two beta‟s from 90Sr in a 0.2 T B-field

100 GeV Muon in testbeam 2010 @ CERN

Particle Detection 9-10 UVA/VU 2002

9

Gossip testbeam August 12 – 22 , 2010

Maarten van Dijk
Martin Fransen
Harry van der Graaf
Fred Hartjes
Wilco Koppert
Sjoerd Nauta
Rolf Schön

Testbeam Aug 2010, RD51/H4, SPS, CERN

Typical event in all 4 detectors (angle 10°)

Typical event in GridPix under 45°
Very small diffusion but big time slewing

From aside

From topSummary of Performance of Gossip- track position resolution:15 μm: simulation 15 μm;- single electron efficiency: > 90 %- track detection efficiency: 99.6 %; simulation 99.4 %Three new infrastructural issues:- New gas- miniHV- ReLaXd readout interface for TimePix-Medipix

Gas versus Si (or Gossip versus Si detectors)

Pro:- no radiation damage in sensor: gas is exchanged- modest pixel (analog) input circuitry: low power, little space- no bias current: simple input circuit- low detector material budget: 0.06 % radiation length/layer
typical: Si foil. New mechanical concepts- low power dissipation : little FE power (2 μW/pixel); no bias dissipation- operates at room temperature (but other temperatures are OK)- less sensitive for neutron and X-ray background- 3D track info per layer if drift time is measured- gas is cheap (and very cheap wrt. Si sensors!), and light- single (free drifting) electron sensitiveCon:- Gaseous chamber: discharges (sparks): destroy CMOS chip- gas-filled proportional chamber: ‘chamber ageing’- limit in spatial resolution due to low primary gas-particle
interaction statistics- Needs gas flow
- Parallax error: 1 ns drift time measurement may be required- diffusion of (drifting) electrons in gas limits spatial resolution

There is a broad interest in GridPix chips

Commercial production is under development
at IZM-Fraunhofer, Berlin.

Goal:
to make robust InGrids on 8” wafers,
for a low price, in large numbers
IZM-Berlin
MESA+/Univ of Twente
Nikhef
Univ. of Bonn
SaclayNew R&D: the all-ceramic GridPix:- Si TimePix chip
- SiNitride protection layer- SiNitride InGrid
common thermal expansion coefficient: 6 x 10-6 K-1

First GEMGrid with SiO2 as insulating spacer between grid and substrate
Victor Blanco Carballo, MESA+/Nikhef

August 2011:First
IZM GridPixs!

- wire bonding pads covered with SiNitride film
- InGrid peel-off at edges (due to unfortunate last correction treatment…..!)- Good outlook to have low-cost mass production in October 2011

intentions to make available:- GridPix chips- ReLaXd readout system (Ethernet out)
- chip carrier boards- DAQ & Control software+- NewGas system: pre-mix bottles- miniHV High Voltage (low current) supplies

ReLaXd Readout

Support & CO2 cooling!

Special requirements for
flammable gas
Gas mixture from 120 l JSP
gas bottle
Whole gas system including
bottle contained in leak tray
Checking gas leaks bymeasuring deficit between
input flow and exhaust flow
Connected to flammable gas
exhaust lineminiHV HighVoltage (low current) system- HV: - 1000 V or – 2000 V- Current: up to 5 μA
- current measurement: 20 pA resolution- CAN bus (pc) controlled- discharges are monitored & counted

LabView controlled gas
Flow logged each minutesystemAlarm at leak rate > 3 ml/min

Operation

Shut off at integrated leak volume of 30 ml

Gas flow set between 5 and 50 ml/min
Possible calibration error by factory (flowtoo low)Applications of GridPix and Gossip

ATLAS:“The baseline ATLAS inner tracker upgrade is an all­ silicondetector. New technologies such as GridPix and the Gossip
version of it could become an alternative sensor technology to
pursue for part of the detector. They would only be adopted incase of major performance or cost advantages over silicon
technology, or if technical issues are found in the silicon projects
in the next 2--3 years. The EB has considered the Gossip R&D
proposal, and supports this R&D for a limited duration of 3 years
to demonstrate and quantify performance, cost and reliability. In
2013, ATLAS will review the results and consider if there aresufficient elements for further pursuance of this technology for
ATLAS”

5 (double) layer Gossip Pixel

ATLAS Upgrade

4 layer Gossip Strixel

radiator
3 layers Gossip TRT& LVL1 trigger

Alternative for TimePix:

GOssip in ATlas
Inner Layer: 7 double Goat strings

Gossip made with FE-I4 pixel chip:rate effect studies (in testbeam)

Gossip readout
Gossip detector unit
Ø60mm Beampipe

P-string conductor(+voltage)

CO2 cooling channels

G-string conductor(+voltage)

Testbeam Nov 5 – 12, 2007
PS/T9: electrons and pions, 1 – 15 GeV/c
L=30 mm
V0

V1
f
Transition Radiator

0.05 mm

Anatoli Romaniouk, Serguei Morozov, Serguei Konovalov
Martin Fransen, Fred Hartjes, Max Chefdeville, Victor Blanco Carballo

Particle Identification
Samples pions (left) and electrons (right)

6 GeV/cLVL1 Momentum Trigger

Double (Si) layers

Two points:
Track segment(vector)
Requires inter-pixel chipcommunication

Gossip measures track segment
in single layer

projected track lengthis measure for momentum:- directly available (LVL1)- at no (extra) cost (mass, power)- at larger R: gas drift gap ~20 mm~ 12 BXs

Requires fast on-pixel chip processing
We are using 130 nm tech.
What about 45 nm tech?

LVL1 trigger from inner tracker

Length of projected track
is direct measure for momentumLVL1 TPC

Transition
Radiator

TRT

LVL1 trigger for threshold momentum
Particle Identification: electron-pion discrimination

WIMP search, bi-phase Xenon• GridPix TPC
as
WIMP / DBD
detector

Source: Direct Searches for Dark Matter, Elena Aprile, EPS - HEP, July 21 2009, Krakow, Poland

4th RD51 Collaboration Meeting
Maarten van DijkIn gas phase:
GridPix (=TimePix + InGrid)
with grid facing down!

Detects single electron eventswith 99% efficiency!
[Essentially due to small pixel
input pad capacity]Gridpix in Xenon: Test setup• Collaboration DARWIN/XENON

4th RD51 Collaboration Meeting
Maarten van Dijk

55Fe in pure argon,
HVgrid = 340 V
P = 1 bar
T = -70 C
at NLR cryostat
gain: ~ 200 !

In Andre Rubbia’s cryostate @ CERN

Results:- TimePix functions well in LAr temperature (-180 C)- In pure Argon, gas gain is limited to ~ 10. Confirmed by other (GEM & TGEM tests)
UV light avalancje propagation?
Needs to be understood: simulations. A gain of 300 would be sufficient.
GEMGrid?
- InGrid collapses at low temperature, due to differences in thermal expansionof InGrid materials (epoxy, aluminium, Si).
Requires all-ceramic GridPix: also good for outgassing.

Operation without quencher: pure Ar, Xe, at cryogenic temperatures

Limit photon propagation towards cathodes

Of interest: RIKEN GEMs (with one electrode stripped!)
Just fix foil on TimePix chipTimePix chipgasliquid (Xe, Ar)
E-field

Transient at
liquid level

Leave out InGrid!
Gas multiplicationin gap between
chip and liquid surface!
Gap ~ 50 microns,
needs active feedback
control.

Gaseous 0-v Double Beta Decay Experiments

superNEMO:
Geiger tracker+
scintillators

hyperNEMO
TPC with GridPix readout

E-field

B-field:- Beta tracks contained in gas volume- momentum measurement from init curvature- total absorption: energy measurement
good energy resolution!

GridPix as photon detector- Photon conversion on InGrid, possibly covered with CsI- Photon conversion in gas (100 eV – 1 MeV)

Gaseous Photomultiplier• Photoelectric effect• Future possibility:
CsI layer on grid4th RD51 Collaboration Meeting
Maarten van Dijk

X-ray Polarimeter proposed by R. Bellazzini

Distribution of direction of photo-electron of (fully) polarised X-rays

With ECAP/University of Erlangen

PolaPix
GridPix as (gas-filled) photon detector for applications in space observatories
via tracking photo-electron or Compton-electron. Measurement of- photon energy- photon direction- polarisationin the range of 1 – 511 keV photons

photo-electron
after photon interaction

X-ray source

Compton Scattered(polarised) photons

Thilo Michel (Univ. of Erlangen/ECAP)A new solid state tracking
detector:
Electron Emission Membranes
and a MEMS made vacuum
electron multiplier
only ideas: no dataA very successful photon detector: the Photomultiplier (1934)- good quantum efficiency- rather fast
- low noise- little dark current, no bias current- radiation hard
- quite linear- voluminous & heavy- no position resolution- expensive- quite radioactive- can‟t stand B fields

Reduce size of dynodes (volume downscaling):- keep potentials as they were (Vstep ~ 200 V)- (non relativistic) electron trajectories sameform, but smaller (volume)- multiplication yield: identical- 1st dynode: focussing, yield- pixel input source capacity: only ~ 10 fF- required gain ~1000 = 2.54 = : 5 dynodes sufficient
Apply MEMS Technology

glass window
photo cathode
1st dynode2nd – 5th dynode

1 mm
input pads
pixel chip

VACUUM!
No „gas amplification‟

Use a MicroChannelPlate MCP?

MCP (invacuum)John Vallerga: TimePix + MCPs
We do not know how to make MEMS made MCP.
Problem: aspect ratio of holes MEMS:micro electron mechanical systems

Quantum Limited Imaging Detectors, RIT
2009, John Vallerga, jvv@ssl.berkeley.edu

The transmission dynode: ultra thin (20 - 100 nm) layers
diamond
SiNitride (Si3N4) Si doped (SiRichNitride, SRN)
CsI
doped SiO2

- ultra fast (single electron) detector: σ = 10 ps- E-force much larger than Lorenz force: operates in B-field- radiation hard
- low mass
In vacuum: no gaseous detector………..

Thickness 15 nm!

SiliconNitride

Delft University of Technology: DIMES

50 μmSiNitride (Si-doped)(insulating) SiO2Essential:- apply pixel circuitry: granularity, small source capacitance- apply infinite high (free ballistic electron) mobility in vacuum!

TwinGrid

TripleGrid

Development of MEMS technology
Wafer Post Processing„There is plenty of room at the top‟ supported by Dutch Economical Affairs

GemGrid

GemGridwith
SiO2 insulator

QuintGrid may be realized earlier
Development // Transmission Dynodes

We can make TripleGrids!

Reinforcement bars required:creates dead regions

Problematic for 1st transmission dynode50 μmFor tracking of fast charged particles (MIPS):
Replace photocathode byElectron Emission Membraneelectron emission membrane

Emits (at least one) electron at thecrossing point of membrane surface
and MIP, with a high probability

aluminium foil:- at least 1 electron is emitted in 4 % of the cases- energy of electron: 0 – 5 eV
- probability depends on surface condition- increase to 6 % if layer of AlOxide is present

Possible improvements in electron emission efficiency:- low work function (CsI, bi-alkali, CVDiamond)- surface treatment: CVDiamond, nanotubes, fractals- Extracting electric field
Try to develop membrane with 50 – 95 % efficiency!

MIPSkin effect: only skin of ~ 50 nm participates in EE.
Rise of EE efficiency by surface enlargement: meandering, modulating, roughening

2nd order modulation, 3rd order..…fractals!
Extracting E-field: constant at surface

Work function
Interesting: - photo cathodes of PMs (bi-alkali etc)
- coating of dynodes of PMs- Eff Alu, Cu: ~ 4 %- Eff ceramics (Diamond, CsI, Si3N4): 10 - 20 %?

Exctracting electric field (close to cold electron emission)- nano grass

Conclusions
MultiPix
MEMS made vacuum electron multiplier integrated on pixel chip
MultiPix + „classical‟ photo cathode
Timed Photon Counter TiPC Tipsy

MultiPix + Electron Emission Membrane
MIP tracking detector

1” x 1”, 2 mm thick

Timed Photon Counter TiPC Tipsy- good quantum efficiency- ultra fast, ps time resolution- low noise- little dark current, no bias current- radiation hard
- perfectly linear (high granularity)- flat, thin & light- 2D position resolution ~ 10 μm- potentially cheap……!
- little radioactive- can stand B fields

Potentially outperforms APDs, G-APDs, SPADs, dSiPMs, QUPIDs
Consumer application: 3D pictures by measurement Time-of-Flight…….!

1” x 1”, 500 μm thick

MIP Tracking detector- moderate track efficiency 50 – 90 %- ultra fast, ps time resolution- low noise- little dark current, no bias current- radiation hard

- flat, thin & light- 2D position resolution ~ 10 μm- potentially cheap……!
- can stand B fields- no 3D track vector info (GridPix)

Outperforms Si trackers in terms of time resolution- high rate experiments- BX timing: ILC/CLIC experiments