Transcript Gax pixel detector for x-ray observation

Gas pixel detector
for x-ray observation
David Attié1
M. Campbell3, M. Chefdeville1,2, P. Colas1, E. Delagnes1, Y. Giomataris1,
H. van der Graaf2, X. Llopart3, J. Timmermans2, J. Visschers2,
1.
[email protected]
2.
3.
Astrophysics Detector Workshop – Nice – November 18th, 2008
1
Outline
Introduction: motivations for a gas pixel detector
1. The TimePix readout chip
• Description
• TimePix Syncronization Logic
2. Micro Pattern Gaseous Detector TPC
• Description of Micromegas
• Integrated Micromegas: InGrid
• Micro-TPC
3. Application for x-ray observations
• Measurement of primary statistics in gas
• TPC-based polarimeter
Conclusion
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
2
Motivations for pixelized gaseous detector
• Gaseous detector advantages:
– 2D/3D imaging
– Low occupancy and low radiation length X0
 mean free path could be important
• Spatial resolution:
– σxy limited by the pad size (pitch/√12)
– narrow charge distribution (RMS ~15 μm)
• High granularity:
– δ-ray recognition/suppression in TPC
– possibility to count primary clusters & electrons
– direction & energy of tracks:
low-energy e- for X-ray polarimetry
ALICE TPC simulations
Bellazzini et al. NIMA 560, 2006, 425
 Digital TPC as a x-ray polarimeter for astrophysics observations
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
3
Astronomical x-ray polarimetry
• Interpretations based on spectral and timing data are often ambiguous;
polarization measurements will resolve the ambiguities.
• Polarization of astrophysical sources may give signature of:
– Emission processes: cyclotron, synchrotron, non thermal bremmstrahlung
(Westfold, 1959; Gnedin & Sunyaev, 1974; Rees, 1975)
– Scattering on aspherical accreting plasmas: disks, blobs, columns
(Rees, 1975; Sunyaev & Titarchuk, 1985; Mészáros, P. et al. 1988)
– Vacuum polarization and birefringence through extreme magnetic fields
(Gnedin et al., 1978; Ventura, 1979; Mészáros & Ventura, 1979)
• Geometry of x-ray sources and physical properties of emission sites
– magnetic field strength and direction in compacts objects
– environment (disk or spherical) in supermassive black holes (AGN)
– accretion geometry
• Cosmic ray acceleration in supernova remnants
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Description of the TimePix chip
• Chip (CMOS ASIC) upgraded in the EUDET framework for high energy physics
from the Medipix2 chip developed first for medical applications
Pixel
• IBM technology 0.25 μm on 6 layers
• Characteristics:
55 mm
Synchronization
Logic
4
55 mm
Counter
Llopart et al., NIMA 581 (2007) 361
• Noise: ~ 650 e– 70 e- per pixel, Cin ~ 15 fF
[email protected]
14080 mm (pixel array)
1
2
3
4
5
Configuration latches
preamp/shaper
threshold discriminator
register for configuration
TimePix synchronization logic
14-bit counter
THL
disc.
–
–
–
–
–
Interface
Preamp/shaper
• For each pixel:
55 μ m
16120 mm
– surface: 1.4 x 1.6 cm2
– matrix of 256 x 256
– pixel size: 55 x 55 μm2
1
2
3
5
14111 mm
55 μ m
Astrophysics Detector Workshop – Nice – November 18th, 2008
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TimePix Synchronization Logic Control
• Each pixel can be configured
independently in 5 different
modes
Timepix
Medipix
Mode
TOT Mode
100 MHz
Internal Shutter
• Internal clock up to 100 MHz
Shutter
DACs values
Mask
P1
P0
Mode
0
0
0
Masked
0
0
1
Masked
0
1
0
Masked
0
1
1
Masked
1
0
0
Medipix
1
0
1
TOT
1
1
0
Timepix-1hit
10 ns
Internal Clock
Digital Signal
Analog Signal
not detected
detected
1
1
1
Timepix
Summed charge
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Astrophysics Detector Workshop – Nice – November 18th, 2008
6
Detectors using TimePix chip
Solid detector
Gas detector
x, y, F(x, y)  2D
Drift cathode grid
x, y, z(t), E(x,y)  3D
X-ray source
Ionizing
particle
Gas volume
+
-
Semiconductor
sensor
Flip-chip
bump bonding
connections
+
Amplification System (MPGD)
+
Medipix2/TimePix chip
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TimePix chip
Astrophysics Detector Workshop – Nice – November 18th, 2008
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InGrid: Integrated Micromegas Grid
• Micromegas is a Micro Pattern Gaseous Detector formed by a metallic
micromesh (hole pitch 70 μm) sustained by 50 μm pillars above the anode (pads)
• Multiplication between anode and mesh
• Gain is a function of the electric field and the gap up to 105
• Integrate Micromegas detector directly on a CMOS chip by post-processing
but need resistive layer protection: ~20 μm of amorphous silicon (a-Si:H)
e-
~ 1 kV/cm
[email protected]
~ 80 kV/cm
PCB
pad
NIKHEF
(MESA+,
Univ. Twente)
CERN
Resistive layer for protection of a-Si:H
Astrophysics Detector Workshop – Nice – November 18th, 2008
IMT
Neuchatel
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InGrid: energy resolution
• Energy resolution depends on the
grid geometry
• Grids can be very flat
Escape peak
Kα
Escape peak
Kβ
13.6 %
FWHM
– best energy resolution achieved:
 13.6 % with 55Fe source in P10
– removal of Kβ 6.5 keV line:
 11.7 % @ 5.9 keV in P10
• Hole pitch down to 14 μm
with various diameters
Gap: 50 μm; Hole picth: 32 μm,Ø: 14 μm
• Different gaps (35-75 μm)
• Until now: grid is 1 μm of Al
but can also be increased to 5 μm
by electrolysis to be more robust
[email protected]
Kβ-filtered spectrum
with Cr foil
Astrophysics Detector Workshop – Nice – November 18th, 2008
11.7%
FWHM
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Micro-TPC using TimePix/Micromegas
• Micro-TPC with a 6 cm height field cage
• Size : 4 cm × 5 cm × 8 cm
Windows for
X-ray sources
Cover
6 cm
Windows for
β sources
Field cage
Micromegas
mesh
• Gas mixture at atmospheric pressure
TimePix chip
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
10
Micro-TPC TimePix/Micromegas
• TimePix chip
+ SiProt 20 μm
+ Micromegas
•
55Fe
source
• Ar/Iso (95:5)
• Time mode
• z = 25 mm
• Vmesh = -340 V
• tshutter = 283 μs
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
11
Measurements of primary statistics in gases
• Diffusion σt should be big enough to separate electrons: e- per pixel ~ 1
• Study of primary electrons and Fano factor F using RMS
• Spectrum of number of electrons for 2000 events:
RMS 2 
F b 1 ε

N
εN
F: Fano factor
√b: single e- gain distribution rms (%)
ε: detection efficiency
N: number of primary e-
 Sensitive to Kα & Kβ lines
TimePix+Ingrid+ 15 μm SiProt
Argon + 5% Isobutane
 FWHM = 9,5 %
 5.9 keV line at ~ 226 e-
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Polarimetry using photoelectric absorption
• Ideal polarimeter is a track imager with:
resolution elements < mean free path of photoelectron
E
X-ray
Photoelectron
• Differential photoelectron cross-section emitted
from the atomic s-orbital in non relativist limit:
2
dσ
2
5 4  me c 

 4 2r0 Z α 
dΩ
h
υ


7
2
Auger
electron
sin 2 θ cos 2 φ
1  β cos θ 4
θ
φ
dσ
 cos 2 φ maximum in the plane x-ray direction
dΩ
Nmax
• θ polar angle, φ azimutal angle
• Emission angles are modulated by the polarization P
P 
Nmax  Nmin
B

N
2A  B
[email protected]
N (φ )  A  B cos (φ  φpol )
2
Nmin
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Prototype TPC polarimeter using TimePix/Micromegas
• TimePix chip
+ SiProt 20 μm
+ Micromegas
•
55Fe
source
• Ne/Iso (90:10)
• TOT mode
• z < 5 mm
• Vmesh = -450 V
• tshutter = 0.2 s
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Prototype TPC polarimeter using TimePix/Micromegas
• Identify the cluster
Photoelection + eauger track in Neon+10 Isobutane
• •TimePix
chip
Determination
of the polarization
+ SiProt 20 μm
Barycentre
+ Micromegas
Principal axis
•
55Fe
source
Reconstructed absorption point
φ
Reconstructed
• Ne/Iso
(90:10) photoemission
direction with identification
of the absorption point and the
• TOT mode
removal of the final part
of the track
• z < 5 mm
φ photoemission angle
• •VLow
-450of
V Neon  e
mesh =
Ek-edge
auger are
isotropically emitted with a small
fraction
ofsthe photon energy
• tshutter
= 0.2
• In low Z gas mixture tracks are
longer so angular reconstruction is easier
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
15
Prototype TPC polarimeter using TimePix/Micromegas
• Double structure operated for the first time (He/Iso, 80:20,
55Fe,
30 mm gap)
• No protection layer  chip survived ~5 hours, protection layer still necessary
• Recent test of silicon nitride (Si3N4) protection layer of 7.5 μm very promising
450V
100V
NIKHEF
(MESA+, Univ. Twente)
[email protected]
55Fe
210
Po
in He/Iso in TOT mode
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Example of TPC for x-ray polarimeter
Drift
Electrode
Readout Strips
130 μm pitch
GEM like
Black et al. NIMA 581, 2007, 755
Gas mixture: Neon/DME 50:50 at 0,6 atm
Photoelectron
y
e- Drift
x(t)
X-ray
x
Trigger
• Uniform response
• Modulation (P ~50 %)
• No false modulation
• An encouraging start
• Quantum efficiency ~ 6%
[email protected]
Image
Polarized 6.4 keV photons
2O mm
Counts
z
Differentiated
Waveforms
Digitized
Waveforms
y
Unpolarized
5.9 keV photons
o
0
45
o
o
90
Photoemission electron angle (degree)
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Conclusions
• TimePix chip/Micromegas + SiProt: demonstrator for the digital TPC
 useful tool for x-ray observations (polarimeter for space telescope: IXO?)
• Identification of the photoelectron angle by imaging the photoelectron track
is very promising for soft x-ray polarimetry ( 2 keV < Eγ < 50 keV) with a
quantum efficiency up to a few percent.
• Need a polarized source and a biggest “Polarimeter/Timepix” collaboration
• Ultimate resolution for a TPC thanks to the single electron sensibility:
Micro-TPC is an excellent tool to characterize photon absorption in gases
• Still some technologic issues:
 Self triggering capability
 How to improve the readout of the chips (speed and larger surface) ?
- through Si connectivity: avoiding bonding wires
- fast readout technology (~5 Gb/s)
 Sealed detector
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
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The TimePix collaboration
• NIKHEF
Harry van der Graaf
Martin Fransen
Jan Timmermans
Jan Visschers
Sipho van der Putten
Arno Aarts
• Saclay CEA/DAPNIA
David Attié
Paul Colas
Esther Ferrer-Ribas
Arnaud Giganon
Yannis Giomataris
Marc Riallot
• Univ. Twente/Mesa+
Jurriaan Schmitz
Victor Blanco Carballo
Cora Salm
Sander Smits
• FREIBURG
A. Bamberger
K. Desch
U. Renz
M. Titov
N. Vlasov
A. Zwerger
P. Wienemann
• CERN
[email protected]
Erik Heijne
Xavier Llopart
Medipix Consortium
β- from 90Sr source in He/Isobutane 80:20
Thank you for your attention
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Backup slides
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Astrophysics Detector Workshop – Nice – November 18th, 2008
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Micromegas & GEMs (MPGD)
Technology choice for TPC readout: Micro Pattern Gaseous Detector
• more robust than wires
• fast signal & high gain
• better ageing properties
• no E×B effect
• low ion backdrift
• easier to manufacture
GEM
Micromegas
• MICROMEsh GAseous Structure
(Y. Giomataris et al., 1996)
• Gas Electron Multiplier (F. Sauli, 1997)
• 2 copper foils separated by kapton
• metallic micromesh (typical pitch 50μm)
• multiplication takes place in holes
• sustained by 50μm pillars, multiplication
between anode and mesh, high gain
• low
use gain
of 2 or 3 stages
Avalanche
50 µm
40 kV/cm
~50 µm
80 kV/cm
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
~1000 µm
1 kV/cm
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Micromegas & GEMs (MPGD)
Technology choice for TPC readout: Micro Pattern Gaseous Detector
• more robust than wires
• fast signal & high gain
• better ageing properties
• no E×B effect
• low ion backdrift
• easier to manufacture
GEM
Micromegas
• simplicity
• 2- or 3- stage amplification
• single stage of amplification
• easy operation
• natural ion feedback suppression
• low field above the electronics
• discharges non destructive
• low discharge probability
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Mixtures of gases containing argon: gain curves
100000
Iso : 1%
Iso : 2%
Iso : 3%
Iso : 4%
Iso : 5%
CF4 : 3%, Iso : 1%
CF4 : 3%, Iso : 2%
CF4 : 3%, Iso : 3%
CH4 : 6%
CH4 : 7,5%
CH4 : 9%
iC4H10
CH4 : 10%
CH4 : 5%, CF4 : 3%
10000
CH4 : 5%, CF4 : 5%
CH4 : 5%, CF4: 10%
CH4 : 10%, CF4 : 3%
CH4 : 5%, CO2 : 3%
Gain
CH4 : 10%, CO2 : 10%
CO2 : 10%
CO2 : 20%
CO2 : 30%
CO2 : 10%, Iso 2%
CO2 : 10%, Iso 5%
CO2 : 10%, Iso 10%
CF4 : 3%, CO2 : 1%
CF4 : 3%, CO2 : 3%
1000
CF4 : 3%, CO2 : 5%
Iso : 2%, CH4 : 10%
Iso : 5%, CH4 : 10%
Iso : 10%, CH4 : 10%
Ethane 10%
CO2, CH4
C 2H 6
Ethane 5%
Ethane 3,5%
Ethane 2%
Ethane 3,5% - CO2 10%
Ethane 3,5% - CF4 3%
Ethane 3,5% - CF4 10%
Micromegas Mesh : 50 mm gap of 10x10 cm² size
Ethane 3,5% - Iso 2%
100
50
55
60
65
70
75
80
85
90
95
100
Field (kV/cm/atm)
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Readout system for Medipix2/TimePix chip
• MUROSv2.1:
–
–
–
–
–
Serial readout
VHDCI cable of length <3m
read 8 chips in mosaic
tunable clock [30-200MHz]
~40fps @160MHz
http://www.nikhef.nl/pub/experiments/medipix/muros.html
• USB:
– Serial readout
– ~5 fps@20MHz
http://www.utef.cvut.cz/medipix/usb/usb.html
• Mosaic achitecture:
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Astrophysics Detector Workshop – Nice – November 18th, 2008
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TimePix chip schematic
Previous Pixel
For each pixel
Ref_Clkb
Clk_Read
Mux
4 bits thr
Adj
Mask
Input
Mux
Preamp
Disc
Shutter
THR
Ctest
Testbit
P0
Polarity
Timepix
Synchronization
Logic
Shutter_in
t
P1
14 bits
Shift
Register
Conf
8 bits
configuration
Test Input
Ovf Control
Ref_Clk
Clk_Read
Next Pixel
Analogic part
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Digital part
Astrophysics Detector Workshop – Nice – November 18th, 2008
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TimePix chip architecture
14080 mm (pixel array)
analog power: 440 mW
digital power (Ref_Clk = 80 MHz): 450 mW
serial readout (@ 100 MHz): 9.17 ms
parallel readout (@ 100 MHz): 287 μs
3584-bit Pixel Column-255
–
–
–
–
16120 mm
• Characteristics:
3584-bit Pixel Column-1
• Reference clock per pixel up to 100 MHz
3584-bit Pixel Column-0
• 36×106 transistors on 6 layers
(~550 transistors/pixel  13.5 μW)
• Pixel modes:
–
–
–
–
masked
counting mode (Medipix, Timepix-1h)
Time-Over-Threshold
 “charge” info
Common stop
 “time” info
256-bit Fast Shift Register
Bandgap + 13 DACs
LVDS
IO
In
Logic
LVDS
32-bit CMOS Output
Out
14111 mm
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
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First TimePix Quad
516
• First Timepix quad
21
3
+ 300 μm Si crystal
1. Medipix mode counting
-
55Fe
source
- tshutter =40 s
2. Time mode
-
90Sr
Y
source
- tshutter = 237 μs
3. Time-Over-Threshold mode
-
241Am
source
- tshutter = 5 s
Llopart & Campbell, CERN
1
1
0
1
[email protected]
X (column number)
2953
250.8
45.75
5905
500.5
90.5
Astrophysics Detector Workshop – Nice – November 18th, 2008
516
8858
750.3
135.3
1.181e+004
1000
180
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TimePix & GEMs
Ar CO2 70/30
Freiburg (+Bonn)
• Cartes de 181x181 en
mode Time & et en TOT
He CO2 70/30
• Fournit les informations
charge & temps en même
temps
[email protected]
• Fort potentiel pour la
séparation de traces
Astrophysics Detector Workshop – Nice – November 18th, 2008
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TimePix using Micromegas
• Timepix chip + Micromegas on frame:
Moiré effects
+ pillars
• Timepix chip + SiProt + Ingrid:
“Uniform”
MESA+
Resistive layer for protection
IMT
Neuchatel
[email protected]
“counting” mode
Astrophysics Detector Workshop – Nice – November 18th, 2008
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Micro-TPC TimePix/Micromegas
• TimePix chip
+ SiProt 20 μm
+ Micromegas
•
90Sr
source
• Ar  He
• Time mode
• z ~ 40 mm
• Vmesh = -340 V
• tshutter = 180 μs
spark-proof !
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
30
Micro-TPC TimePix/Micromegas
• TimePix chip
+ SiProt 20 μm
+ Micromegas
•
90Sr
source
• Ar/Iso (95:5)
• Time mode
• z ~ 40 mm
• Vmesh = -340 V
• tshutter = 180 μs
[email protected]
Astrophysics Detector Workshop – Nice – November 18th, 2008
31
Gas mixture containing Neon
http://www-cxro.lbl.gov
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Simulated quality factor
Bellazzini et al., NIMA 572 (2007) 167
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Astrophysics Detector Workshop – Nice – November 18th, 2008
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