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<strong>Silicon</strong> <strong>Detectors</strong> !<br />
Manfred Krammer!<br />
Institute of High Energy Physics, Vienna, Austria!
<strong>Silicon</strong> <strong>Detectors</strong> <br />
Content!<br />
2 Basics!<br />
3 Detector Structures!<br />
4 Performance!<br />
6 The CMS Inner Tracker!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 1!
2 Basics!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 2!
2.1 Materials <br />
Elemental semiconductors!<br />
! Germanium: Used in nuclear physics, due to small band gap<br />
(0.66 eV) needs cooling (usually done with liquid nitrogen at 77 K)!<br />
! <strong>Silicon</strong>: Standard material for vertex and tracking detectors in high<br />
energy physics, can be operated at room temperature, synergies with<br />
micro electronics industry.!<br />
! Diamond (CVD or single crystal): Large band gap, requires no<br />
depletion zone, very radiation hard, drawback is a low signal and high<br />
cost!!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 3!
2.1 Materials <br />
Compound semiconductors!<br />
Compound semiconductors consist of two (binary semiconductors) or<br />
more atomic element. Depending on the column in the periodic system<br />
of elements one differentiates between IV-IV- (e.g. SiGe, SiC), III-V-,<br />
und II-VI compounds!<br />
! important III-V compounds:!<br />
– GaAs: Faster and probably more radiation resistant than Si. !<br />
!Drawback is less experience in industry and cost.!<br />
– GaP, GaSb, InP, InAs, InSb, InAlP!<br />
! important II-VI compounds: !<br />
– CdTe: High atomic numbers (48+52) hence very efficient to detect<br />
photons.!<br />
– ZnS, ZnSe, ZnTe, CdS, CdSe, Cd 1-x Zn x Te, Cd 1-x Zn x Se!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 4!
2.2 Material Properties <br />
Bond model of semiconductors!<br />
Example of column IV elemental semiconductor (2dim projection) :!<br />
T = 0 K! T > 0 K!<br />
Valence electron!<br />
Conduction electron!<br />
! Each atom has 4 closest neighbors, the 4 electrons in the outer shell are<br />
shared and form covalent bonds.!<br />
! At low temperature all electrons are bound!<br />
! At higher temperature thermal vibrations break some of the bonds " free e -<br />
cause conductivity (electron conduction)!<br />
! The remaining open bonds attract other e - " The holes change position<br />
(hole conduction)!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 5!
2.2 Material Properties <br />
Energy bands: isolator–semiconductor–metal!<br />
In an isolated atom the electrons have only discrete energy levels. In solid state<br />
material the atomic levels merge to energy bands. In metals the conduction and<br />
the valence band overlap, whereas in isolators and semiconductors these levels<br />
are separated by an energy gap (band gap). In isolators this gap is large.!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 6!
2.2 Material Properties <br />
Intrinsic carrier concentration!<br />
! Due to the small band gap in semiconductors electrons already occupy!<br />
the conduction band at room temperature.!<br />
!<br />
! Electrons from the conduction band may recombine with holes.!<br />
!<br />
! A thermal equilibrium is reached between excitation and recombination!<br />
Charged carrier concentartion n e = n h = n i !<br />
This is called intrinsic carrier concentration:!<br />
$<br />
n i = N C N V " exp # E g<br />
&<br />
% 2kT<br />
'<br />
) * T 3 $<br />
2<br />
" exp # E g<br />
&<br />
( % 2kT<br />
'<br />
)<br />
(<br />
In ultrapure silicon the intrinsic carrier concentration is1.45·10 10 cm -3 . !<br />
!<br />
With approximately 10 22 Atoms/cm 3 about 1 in 10 12 silicon atoms is ionised.!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 7!
2.3 Constructing a Detector <br />
The ideal semiconductor detector!<br />
One of the most important parameter of a detector is the signal to noise ratio<br />
(SNR). A good detector should have a large SNR. However this leads to two<br />
contradictory requirements:!<br />
# Large signal <br />
" low ionisation energy " small band gap!<br />
# Low noise <br />
" very few intrinsic charge carriers " large band gap!<br />
An optimal material should have E g ≈ 6 eV. !<br />
In this case the conduction band is almost empty at room temperature and the<br />
band gap is small enough to create a large number of e - h + pairs through<br />
ionisation.!<br />
Such a material exist, it is Diamond. However even artificial diamonds (e.g. CVD<br />
diamonds) are too expensive for large area detectors.!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 8!
2.3 Constructing a Detector <br />
Estimate SNR in an intrinsic silicon detector!<br />
Lets make a simple calculation for silicon: ! ! ! !<br />
!Mean ionization energy I 0 = 3.62 eV, mean energy loss per flight path<br />
!dE/dx = 3.87 MeV/cm, intrinsic charge carrier density at T = 300 K<br />
!n i = 1.45 · 10 10 cm -3 . !<br />
Assuming a detector with a thickness of d = 300 µm and an area of A = 1 cm 2 .!<br />
" Signal of a mip in such a detector:!<br />
!<br />
dE dx " d<br />
I 0<br />
= 3.87"106 eV cm" 0.03cm<br />
3.62eV<br />
"!Intrinsic charge carrier in the same volume (T = 300 K):!<br />
# 3.2"10 4 e $ h + $pairs<br />
n i<br />
d A =1.45 "10 10 cm -3 " 0.03cm"1cm 2 # 4.35 "10 8 e $ h + $pairs<br />
!<br />
!<br />
"!Number of thermal created e – h + -pairs are four orders of magnitude larger<br />
than signal!!!!<br />
Have to remove the charge carrier! !<br />
! !" Depletion zone in reverse biased pn junctions!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 9!
2.4 Doping <br />
Bond model: n-doping in Si!<br />
Doping with an element 5 atom (e.g. P, As, Sb). The 5 th valence electrons is<br />
weakly bound.!<br />
The doping atom is called donor!<br />
The released conduction electron<br />
leaves a positively charged ion!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 10!
2.4 Doping <br />
Bond model: n-doping in Si!<br />
The energy level of the donor is just below the edge of the conduction band. At<br />
room temperature most electrons are raised to the conduction band.!<br />
The fermi level E F moves up. !<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 11!
2.4 Doping <br />
Bond model: p-doping in Si!<br />
Doping with an element 3 atom (e.g. B, Al, Ga, In). One valence bond<br />
remains open. This open bond attracts electrons from the neighbor atoms.!<br />
The doping atom is called acceptor. !<br />
The acceptor atom in the lattice is<br />
negatively charged.!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 12!
2.4 Doping <br />
Bond model: p-doping in Si!<br />
The energy level of the acceptor is just above the edge of the valence band. At<br />
room temperature most levels are occupied by electrons leaving holes in the<br />
valence band.!<br />
The fermi level E F moves down. !<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 13!
2.5 The p-n Junction <br />
Creating a p-n junction!<br />
At the interface of an n-type and p-type semiconductor the difference in the fermi<br />
levels cause diffusion of surplus carries to the other material until thermal equilibrium<br />
is reached. At this point the fermi level is equal. The remaining ions create a space<br />
charge and an electric field stopping further diffusion.!<br />
The stable space charge region is free of charge carries and is called the depletion<br />
zone.!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 14!
2.5 The p-n Junction <br />
Operation with forward bias!<br />
p-n junction with forward bias!<br />
Applying an external voltage V with the anode<br />
to p and the cathode to n e- and holes are<br />
refilled to the depletion zone. The depletion<br />
zone becomes narrower.!<br />
!<br />
!<br />
The potential barrier becomes smaller by eV<br />
and diffusion across the junction becomes<br />
easier. The current across the junction<br />
increases significantly.!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 15!
2.5 The p-n Junction <br />
Operation with reverse bias!<br />
p-n junction with reverse bias!<br />
Applying an external voltage V with the cathode<br />
to p and the anode to n e- and holes are pulled<br />
out of the depletion zone. The depletion zone<br />
becomes larger.!<br />
!<br />
!<br />
The potential barrier becomes higher by eV and<br />
diffusion across the junction is suppressed. The<br />
current across the junction is very small<br />
leakage current.!<br />
" Thats the way we operate our semiconductor detector!!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 16!
2.5 The p-n Junction <br />
Width of the depletion zone!<br />
Example of a typical p + -n junction in a silicon detector:!<br />
Effective doping concentration N a = 10 15 cm –3 in p+ region and N d = 10 12 cm –3 in<br />
n bulk.!<br />
Without external voltage:!<br />
W p = 0.02 µm !<br />
W n = 23 µm!<br />
Applying a reverse bias voltage of 100 V:!<br />
W p = 0.4 µm !<br />
W n = 363 µm!<br />
Width of depletion zone in n bulk:!<br />
W "<br />
2# 0 # r µ$V<br />
with!<br />
" =<br />
1<br />
e µN eff<br />
p + n junction!<br />
V !… !External voltage!<br />
" !… !specific resistivity!<br />
µ !… !mobility of majority charge carriers!<br />
N eff !… !effective doping concentration!<br />
!<br />
!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 17!
2.5 The p-n Junction <br />
Current-voltage characteristics!<br />
Typical current-voltage of a p-n junction (diode): exponential current increase<br />
in forward bias, small saturation in reverse bias.!<br />
!<br />
Ideal diode equation:! * #<br />
I = I 0 " exp eV & -<br />
% ( ) 1 I<br />
,<br />
/ 0 … reverse saturation current!<br />
+ $ kT ' .<br />
!<br />
S.M. Sze, Semiconductor Devices , J. Wiley & Sons, 1985!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 18!
2.6 Detector Characteristics <br />
Leakage Current!<br />
A silicon detector is operated with reverse bias, hence reverse saturation<br />
current is relevant (leakage current). This current is dominated by thermally<br />
generated e - h + pair. Due to the applied electric field they cannot recombine and<br />
are separated. The drift of the e - and h + to the electrodes causes the leakage<br />
current. !<br />
Measured detector leakage current, CMS<br />
strip detector (measurement at room<br />
temperature):!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 19!
2.6 Detector Characteristics <br />
Depletion Voltage!<br />
The depletion voltage is the minimum voltage at which the bulk of the sensor is<br />
fully depleted. The operating voltage is usually chosen to be slightly higher<br />
(overdepletion).!<br />
High resistivity material (i.e. low doping) requires low depletion voltage.!<br />
Depletion voltage as a function of the<br />
material resistivity for two different<br />
detector thicknesses (300 µm, 500 µm).!<br />
reverse bias voltage V [V]!<br />
resistivity " [kOhm cm]!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 20!
2.6 Detector Characteristics <br />
Capacitance of a detector!<br />
For a typical Si p-n junction (N a >> N d >> n i ) the detector capacitance is given<br />
as:!<br />
!<br />
C =<br />
" 0<br />
" r<br />
2µ# V $ A<br />
Measured detector capacitance as a<br />
function of the bias voltage, CMS strip<br />
detector:!<br />
" !… !specific resistivity of the bulk!<br />
µ !… !mobility of majority charge carrier!<br />
V !… !bias voltage !!<br />
A !… !detector surface!<br />
!<br />
!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 21!
3 Detector Structures!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 22!
3.1 Microstrip Detector <br />
DC coupled strip detector!<br />
Through going charged particles create e - h + pairs in the depletion zone (about<br />
30.000 pairs in standard detector thickness). These charges drift to the electrodes.<br />
The drift (current) creates the signal which is amplified by an amplifier connected<br />
to each strip. From the signals on the individual strips the position of the through<br />
going particle is deduced. !<br />
!<br />
A typical n-type Si strip detector:!<br />
! p + n junction: <br />
N a ≈ 10 15 cm -3 , N d ≈ 1–5·10 12 cm -3 !<br />
! n-type bulk: ! > 2 k#cm <br />
" thickness 300 µm !<br />
! Operating voltage < 200 V.!<br />
! n + layer on backplane to improve<br />
ohmic contact!<br />
! Aluminum metallization !<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 23!
3.1 Microstrip Detector <br />
AC coupled strip detector!<br />
AC coupling blocks leakage current from the amplifier.!<br />
! Integration of coupling capacitances in<br />
standard planar process.!<br />
! Deposition of SiO 2 with a thickness of 100–<br />
200 nm between p+ and aluminum strip!<br />
! Depending on oxide thickness and strip width<br />
the capacitances are in the range of 8–<br />
32 pF/cm.!<br />
! Problems are shorts through the dielectric<br />
(pinholes). Usually avoided by a second layer<br />
of Si 3 N 4 .!<br />
AC coupled strip detector:!<br />
Several methods to connect the bias voltage: polysilicon resistor,<br />
punch through bias, FOXFET bias.!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 24!
3.1 Microstrip Detector <br />
Polysilicon bias – 1!<br />
! Deposition of polycristalline silicon between p + implants and a common bias<br />
line. !<br />
! Sheet resistance of up to R s ≈ 250 k#/$. Depending on width and length a<br />
resistor of up to R ≈ 20 M# is achieved (R = R s·length/width).!<br />
! To achieve high resistor values winding poly structures are deposited.!<br />
! Drawback: Additional production<br />
steps and photo lithograpic masks<br />
required.!<br />
Cut through an AC coupled strip<br />
detector with integrated poly resistors:!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 25!
3.1 Microstrip Detector <br />
Polysilicon bias – 2!<br />
Top view of a strip detector with<br />
polysilicon resistors:!<br />
CMS-Microstrip-Detektor: Close view of<br />
area with polysilicon resistors, probe<br />
pads, stip ends.!<br />
CMS Collaboration, <strong>HEPHY</strong> Vienna!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 26!
3.3 Hybrid Pixel <strong>Detectors</strong> <br />
Principle!<br />
Flip-Chip pixel detector:!<br />
On top the Si detector, below the readout chip,<br />
bump bonds make the electrical connection for<br />
each pixel. !<br />
Detail of bump bond connection.<br />
Bottom is the detector, on top the<br />
readout chip:!<br />
S.L. Shapiro et al., Si PIN Diode Array Hybrids for Charged !<br />
Particle Detection, Nucl. Instr. Meth. A 275, 580 (1989)!<br />
L. Rossi, Pixel <strong>Detectors</strong> Hybridisation, !<br />
Nucl. Instr. Meth. A 501, 239 (2003)!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 27!
3.3 Hybrid Pixel <strong>Detectors</strong> <br />
Bump bonding process – 2!<br />
Electron microscope pictures before and after the reflow production step. !<br />
PbSn bump, diameter 25 µm, pitch: 50 µm, reflow by heating to app. 300 °C.!<br />
L. Rossi, Pixel <strong>Detectors</strong> Hybridisation, Nucl. Instr. Meth. A 501, 239 (2003)!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 28!
4 Performance!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 29!
4.1 Signal to Noise Ratio <br />
Introduction!<br />
! The signal generated in a silicon detector depends essentially only!<br />
on the thickness of the depletion zone and on the dE/dx of the !<br />
particle.!<br />
!<br />
!<br />
! The noise in a silicon detector system depends on various !<br />
parameters: geometry of the detector, the biasing scheme, the !<br />
readout electronics, etc. !<br />
!<br />
! Noise is typically given as equivalent noise charge ENC. This is !<br />
the noise at the input of the amplifier in elementary charges. !<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 30!
4.1 Signal to Noise Ratio <br />
Noise contributions!<br />
The most important noise contributions are:!<br />
1. Leakage current (ENC I )!<br />
2. Detector capacity (ENC C )!<br />
3. Det. parallel resistor (ENC Rp )!<br />
4. Det. series resistor (ENC Rs )!<br />
Alternate circuit diagram of a<br />
silicon detector. !<br />
The overall noise is the quadratic sum of all contributions:!<br />
ENC = ENC 2 C + ENC 2 2<br />
I + ENC Rp<br />
2<br />
+ ENC Rs<br />
!<br />
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4.1 Noise Contributions <br />
Detector capacity!<br />
The detector capacity at the input of a charge sensitive amplifier is<br />
usually the dominant noise source in the detector system. !<br />
This noise term can be written as:!<br />
ENC C<br />
= a + b " C<br />
The parameter a and b are given by the design of the (pre)-amplifier.<br />
C is the detector capacitance at ! the input of the amplifier channel.!<br />
Integration time t p is crucial, short integration time leads usually to<br />
larger a and b values. Integration time is depending on the accelerator<br />
time structure.!<br />
Typical values are (amplifier with ~ 1 µs integration time): !<br />
a ≈ 160 e und b ≈ 12 e/pF!<br />
To reduce this noise component segmented detectors with short<br />
strip or pixel structures are preferred. !<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 32!
4.1 Signal to Noise Ratio <br />
Summary!<br />
To achieve a high signal to noise ratio in a silicon detector system the<br />
following conditions are important:!<br />
! Low detector capacity (i.e. small element size)!<br />
! Low leakage current!<br />
! Large bias resistor!<br />
! Short and low resistance connection to the amplifier!<br />
! Usually long integration time!<br />
Obviously some of the conditions are contradictory. Detector and<br />
front end electronics have to be designed as one system. The<br />
optimal design depends on the application.!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 33!
4.2 Position Resolution <br />
Introduction!<br />
The position resolution – the main parameter of a position detector –<br />
depends on various factors, some due to physics constraints and some<br />
due to the design of the system (external parameters). !<br />
! Physics processes:!<br />
! External parameter:!<br />
– Statistical fluctuations of the energy loss!<br />
– Diffusion of charge carriers!<br />
– Binary readout (thresh hold counter) or read out of<br />
analogue signal value!<br />
– Distance between strips (strip pitch)!<br />
– Signal to noise ratio!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 34!
4.2 Position Resolution <br />
Statistical fluctuation of the energy loss – 1!<br />
! <strong>Silicon</strong> position detectors are thin (300–500 µm) and absorb only a small<br />
fraction of the total energy of through going particles. !<br />
! The energy loss dE/dx follows a Landau distribution, an asymmetric<br />
probability function with a long tail to large energy deposits.!<br />
! Example of a mip measured in a 300 µm thick silicon detector:!<br />
o<br />
o<br />
Most probable energy loss<br />
(Maximum of the distribution):<br />
78 keV in 300 µm " ≈ 72 e – h +<br />
pairs per µm!<br />
Mean of the energy loss:<br />
116 keV in 300 µm " ≈ 108 e – h +<br />
pairs per µm!<br />
Pions and Protons:!<br />
W. Adam et al., CMS note 1998/092 (1998)!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 35!
4.2 Position Resolution <br />
Diffusion – 2!<br />
! h + created close to the anode (i.e. the n + backplane) and e - created<br />
close to he cathode (i.e. the p + strips or pixels) have the longest drift<br />
path. As a consequence the diffusion acts much longer on them<br />
compared to e - h + with short track paths. !<br />
" The signal measured comes from many overlapping Gaussian<br />
distributions. !<br />
Drift and diffusion acts on charge carriers:!<br />
Charge density distribution for 5<br />
equidistant time intervalls: !<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 36!
4.2 Position Resolution <br />
Threshold readout versus analogue readout!<br />
! Threshold readout (one strip signal):!<br />
" position:! x = strip position<br />
" resolution: !<br />
" x # p 12<br />
p<br />
x<br />
!… !distance between strips<br />
(readout pitch)!<br />
!… !position of particle track!<br />
! charge center of gravity (signal on two strips):!<br />
!<br />
" position: !<br />
!<br />
!<br />
!<br />
!<br />
x = x 1 +<br />
" resolution: !<br />
h 1<br />
( x 2 " x 1 ) = h 1 x 1 + h 2 x 2<br />
h 1 + h 2 h 1 + h 2<br />
" x "#<br />
p<br />
SNR<br />
x 1 ,x 2 … position of 1 st and<br />
2 nd strip!<br />
h 1 ,h 2 … signal on 1 st and<br />
2 nd strip!<br />
SNR … signal to noise ratio!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 37!<br />
!<br />
!
4.2 Position Resolution <br />
Example – influence of readout pitch and SNR!<br />
Example of a detector with strip pith of 25 µm and analogue readout.!<br />
The position resolution is plotted as a function of the SNR.!<br />
Bottom curve: every strip is connected to the readout electronics!<br />
Top curve: every 2 nd strip is connected, one intermediate strip!<br />
!<br />
To benefit from intermediate strips<br />
large SNR is required!!<br />
A. Peisert, <strong>Silicon</strong> Microstrip <strong>Detectors</strong>, !<br />
DELPHI 92-143 MVX 2, CERN, 1992!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 38!
6.3 The CMS Inner Tracker!<br />
! ! !!<br />
! ! !The CMS Inner Tracker!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 39!
6.3 The CMS Inner Tracker <br />
The CMS Experiment!<br />
CMS<br />
A Compact Solenoidal Detetor for LHC<br />
MUON CHAMBERS<br />
INNER TRACKER<br />
E.M. CRYSTAL CAL.<br />
HADRON CAL.<br />
VERY FORWARD<br />
CALORIMETER<br />
Total Weight : 12,000 t.<br />
Overall diameter : 14.00 m<br />
Overall length : 20.00 m<br />
Magnetic field : 4 Tesla<br />
SUPERCONDUCTING COIL<br />
RETURN YOKE<br />
CMS 1000<br />
jlb<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 40!
6.3 The CMS Inner Tracker <br />
Layout of the detector!<br />
Inner Barrel –TIB<br />
Inner Disks –TID<br />
Outer Barrel –TOB<br />
Pixel<br />
End cap –TEC<br />
2,4 m<br />
Volume 24.4 m 3<br />
temperature -10 0 C<br />
dry atmosphere<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 41!
6.3 The CMS Inner Tracker <br />
Some numbers!<br />
Strip detector: <br />
!~200 m 2 of silicon sensors <br />
!24,244 single silicon sensors <br />
!15,148 modules <br />
!9,600,000 strips $ electronics channels <br />
!75,000 read out chips (APV25) <br />
!25,000,000 Wire bonds!<br />
!<br />
Pixel detector:!<br />
!1 m 2 detector area!<br />
!1440 pixel modules!<br />
!66 million pixels!<br />
!<br />
Industrial type of production in many laboratories worldwide.!<br />
!Largest <strong>Silicon</strong> detector built so far !!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 42!
6.3 The CMS Inner Tracker <br />
A worldwide collaboration!<br />
55 institutes from 9 countries (Austria, Belgium, Finland, <br />
!France, Germany, Italy, Switzerland, UK, USA) <br />
About 500 scientists and engineers involved in the design and construction!<br />
of the CMS inner tracker.!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 43!
6.3 The CMS Inner Tracker <br />
Example of strip module geometries!<br />
27 mechanical different modules + 2 types of alignment modules !<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 44!
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 45!
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 46!
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 47!
Tracker Insertion!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 48!
6.3 The CMS Inner Tracker <br />
The pixel detector!<br />
~50 cm!<br />
~1 m!<br />
~40 cm!<br />
Pixel size: 100 µm x 150 µm!<br />
Barrel Pixel: <br />
3 barrel layers at r of 4.3, 7.3, 10.4 cm <br />
11520 chips (48 million pixels)!<br />
Forward Pixel: <br />
4 disks at z of ±35.5 and ±46.5 cm <br />
4320 chips (18 million pixels) <br />
Modules dilted by 20 o for better <br />
charge sharing!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 49!
6.3 The CMS Inner Tracker <br />
The pixel detector - construction!<br />
Hybrid Pixel Technology: <br />
Readout chips (ROCs) bump bonded to high resistivity silicon sensor!<br />
Barrel Pixel sensor wafer:! Bump bonds:!<br />
Thickness 270 µm <br />
n + -pixels in n-bulk with <br />
p-spray (CIS) or p-stop (SINTEF) <br />
<br />
!<br />
Bump bonding process <br />
Barrel: Indium, In-house at PSI <br />
Forward: PbSn at two vendors (RTI, IZM) <br />
!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 50!
6.3 The CMS Inner Tracker <br />
Barrel pixel: module design!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 51!
6.3 The CMS Inner Tracker <br />
A barrel pixel module !<br />
The barrel pixel consists of about 800 modules!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 52!
6.3 The CMS Inner Tracker <br />
A half disc of the forward pixel detector!<br />
Forward Pixel: consists of 672 plaquettes !<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 53!
6.3 The CMS Inner Tracker <br />
PIxel insertion!<br />
Barrel Pixel!<br />
Forward Pixel!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 54!
6.3 The CMS Inner Tracker <br />
Possible discoveries at the LHC: Higgs!<br />
A promising discovery channel for a light Standard Model Higgs Boson is!<br />
ttH"jjb l%b bb:!<br />
Final state 6 jets (4 b-jets), 1 lepton, !<br />
1 neutrino (missing Energy):!<br />
…a superb task for the <strong>Silicon</strong> detector…!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 55!
6.3 The CMS Inner Tracker <br />
Simulation from CMS: Higgs!<br />
Simulation of a 120 GeV Higgs decaying inside the CMS <strong>Silicon</strong> tracker:!<br />
M. Krammer, Praktikum 2010/11! <strong>Silicon</strong> <strong>Detectors</strong>! 56!
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