Post on 14-Jun-2020
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The Semiconductor Drift Detector(SDD)
The Concept of Semiconductor Drift DetectorHistory of the development
Transport of charged carriers in thin fully depleted semiconductor detectors in direction parallel to the large surface of the detector.
Ionizing particle
Anode
0.3 mm
Drift < 40mm
Drift of charged carriers in silicon
Reverse-biased one sided step p-n junction in 1dimension
Negative electric field -E
dE/dx=r/e
+
N typeP type
-
Depleted region
Space chargeNegative potential -U
E=-dU/dx
e-h+
Depletion from two sides
P+ rectifying contacts
N+ ohmiccontacts
n- bulkSection shown below
SDD principle
Ionizing particleRectifying electrodes
Anodes
* M f PR t
Low capacitance anode
EP
XEP
X
EP
XEP
X
The first signals from a SDD
The classical PIN diode detector
n
n+
p+ -Vcc
The anode capacitance is proportional to the detector active area
The SDD for X-ray spectroscopy
n
n+
p+ -Vcc
p+
AnodeThe electrons are collected by the small anode,characterised by a low output capacitance whichis independent on the active area of the detector.
The SDD structure
• The electrons, generated in the fully depleted silicon by the X-ray photons, are collected by the small anode (having a very low capacitance, Cdet=150fF).
• The integrated front-end transistor (n-JFET) allows the capacitive matching between detector and amplifier(Cdet≈Cgate)
Anode
Ring #1
last RingClear
Entrance window
n-JFET
p+
G SD
path ofelectronsn Si
_
Advantages: very high energy resolution at fast shaping times, due to the small anode capacitance, independent of the active area of the detector
The integrated JFET
Detector produced at the MPI Halbleiterlabor, Munich, Germany
SDD performances
0 1 2 3 4 5 6 7 8Energy [keV]
0
500
1000
1500
2000
2500
Cou
nts
152 eV FWHM
Mn-Kα
Mn-Kβ
0 1 2 3 4 5 6 7 8Energy [keV]
1
10
100
1000
10000
Cou
nts
Mn-Kα
Mn-Kβ
Si-escape
• 55Fe spectrum measured with the SDD module at T= -8°C and a shaping time of 0.5 µs.
The integrated JFET
FET
Guard electrode
Anode
The “conventional” central anode containing the FET
FET
Anode
Electrons
The “lateral” anode with side FET
FET
The new Silicon Drift Detector Droplet (SD3)
Anode
FET
Anode
electrons
The resolution of the new SD3
STANDARD SDDAnode capacitance = 150 fFFWHM= 150 eV (typ)
at T= -10°C
DROPLET SDDAnode capacitance = 50 fFFWHM= 130 eV (typ)
at T= -20°CPeak/Background > 5000
5000 5500 6000 6500 7000ENERGY [eV]
0
2000
4000
6000
8000
CO
UN
TS
Fe55
Kα
Kβ
FWHM=131 eV
Performances with soft X-ray
Some applications of thesingle-element SDDsin X-ray spectroscopy
Analysis of the alloy composition of the ‘Lupa Capitolina’
Musei Capitolini, Roma
XRF spectrum of the bronze alloy of the ‘Lupa’
0 10000 20000 30000ENERGIA [eV]
1
10
100
1000
10000
100000
CO
NTE
GG
I
KαSn
Kα
Kβ
Fe
Kα
Kβ
Cu
LαLβ
Lγ1
PbLαSn
KαCl
KαCa
Element distribution on the ‘Lupa’ body
Sn
05
101520253035
0 90 180 270 360Angle
%
Pb
02468
10121416
0 90 180 270 360Angle
%
Fe
00.5
11.5
22.5
33.5
0 90 180 270 360
Angle
%
Analysis of the alloy composition of the “Spinario”
Musei Capitolini, Roma
Analysis of a bronze roman sculpture
01020304050
0 50 100
% Rame
% S
tagn
o
Capo
Corpo
0
0.1
0.2
0.3
0.4
0.5
0.6
0 20 40 60 80 100
% R ame
CapoCorpo
0
5
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15
20
25
30
35
0 20 40 60 80 100
% R ame
CapoCorpo
0
0.5
1
1.5
2
2.5
0 20 40 60 80 100
% R ame
% F
erro Capo
Corpo
00.10.20.30.40.50.6
0 20 40 60
%Stagno
% N
Iche
l
Capo
Corpo
Correlation diagrams of the bronze compositionof several points of the head and of the body of the sculpture, showing that the two parts have been produced with different fusion (maybe in a differenthistorical period). The last diagram shows that Ni has been probably introduced as impurity of Sn.
Analysis of an Egyptian Linen (Antinopolis, III century A.C.)
Museo Vaticano, Roma
2 4 6 8 10 12 14 16 18Energy [keV]
0
2000
4000
6000
8000
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12000
14000C
ount
s
+ Pb (Lα)
Fe (Kβ))
Ca (Kα)
W (Lα)
Au (Lα)
Ca (Kβ)
Fe (Kα)
As (Lβ)
Pb (Lβ)
As (Kα)
Yellow ochre Fe(OH)3
8 9 10 11 12 13 14Energy [keV]
0
1000
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3000
4000
5000
Cou
nts
+ Pb (Lα)
As (Kβ))
W (Lα)
Au (Lα)
As (Kα)
Au (Lβ)
Pb (Lβ)Gold Au
It can not be only W becauseW Lα / W Lβ should be ≈1
Orpiment As2S3
Au (Lα) + W (Lβ)
Au (Lβ)
Analysis of the earring
Authenticity verification
1 2 3 4 5 6 7 8Energy [keV]
0.0
0.2
0.4
0.6
0.8
Norm
alize
din
tens
ity[a
.u.]
Ti-KαK-Kα
(a)
Fe-Kα
Fe-KβCa-KαArClSi
S
1 2 3 4 5 6 7 8Energy [keV]
0.0
0.2
0.4
0.6
0.8
Nor
mal
ized
inte
nsity
[a.u
.]
Mn-KαTi-Kα
K-Kα
S
(b)
Fe-Kα
Fe-KβCa-Kα
ArClSi
1 2 3 4 5 6 7 8Energy [keV]
0.0
0.2
0.4
0.6
0.8
Nor
mal
ized
inte
nsity
[a.u
.]
Mn-KαK-Kβ
K-Kα
S
(c)
Fluorescence spectra of a document in a reference point (a) and in a point where stain removerwas supposed to be applied (b) (the spectra are normalized with respect to the Ti-Kα line).In (c) the difference between the two spectra (a) and (b) is reported, revealing a probableapplication of a conventional stain remover containing S, K, and Mn.
Multi-element SDDs
The 12-element SDD detector
Center hole2.4 mm
SDD cell5 mm2
Detector chip17x17 mm2
Sensitive area12x5 mm2
= 60mm2
“Front” Sidecollecting anode,JFET,Basing electrodes
Detector thickness 300 µm
“Back” Sidenon-structured radiation entrance window.
The 12-element SDD detector
Detector performances
2000 2500 3000 3500 4000Channels
0
1000
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3000
Cou
nts 165 eV FWHM
2000 2500 3000 3500 4000Channels
0
1000
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Cou
nts 155 eV FWHM
2000 2500 3000 3500 4000Channels
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Cou
nts
160 eV FWHM
2000 2500 3000 3500 4000Channels
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nts
160 eV FWHM
2000 2500 3000 3500 4000Channels
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nts
153 eV FWHM
2000 2500 3000 3500 4000Channels
0
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3000C
ount
s 152 eV FWHM
2000 2500 3000 3500 4000Channels
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nts
150 eV FWHM
2000 2500 3000 3500 4000Channels
0
1000
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3000
Cou
nts
152 eV FWHM
2000 2500 3000 3500 4000Channels
0
1000
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4000
Cou
nts 153 eV FWHM
2000 2500 3000 3500 4000Channels
0
1000
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4000
Cou
nts
148 eV FWHM
2000 2500 3000 3500 4000Channels
0
1000
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nts
152 eV FWHM
2000 2500 3000 3500 4000Channels
0
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nts 156 eV FWHM
55Fe radioactive source – T = -10 °C – Tennelec TC244 gaussian shaping amplifier τsh = 0.5 µsCount rate ≈ 10 kcps / channel. Average FWHM: 154.7 eV
A new multi-element Semiconductor Srift Detector optimized for XRF Elemental Mapping
Project FELIX INFN Gr.5 2003-04
A new multi-element Semiconductor Srift Detector optimized for XRF Elemental Mapping
Thickness 450 µm14 mm
Front sideCollecting anode and transistor
Back sideRadiation entrance window
SDD4 collimator
Collimated area ≈ 4 x 15 mm2
SDD4: collecting region
Collecting anodeand input JFET
Ultra-lowDetector + JFETcapacitance:Cd+Cg ≈ 120 fF
SDD4 potential energy
Collecting anodeand
input JFET
Radiation entrancewindow
CDET+CJFET ≈ 120fF
130.4 FWHM
Det 1
130.4 FWHM
Det 2
130.3 FWHM
Det 3
132.1 FWHM
Det 4
SDD4 preliminary results
Radiation source: 55FeCount rate ≈ 2 kcps / channelτsh=1.5µs NO collimation
SDD4 preliminary results
Peak to valley ratio
P/V≈6000
Tsh=500ns Beam collimated: ∅≈500µm
SDD4 preliminary resultsResolution vs count rate
55FeTsh=350ns
Counts per channel
SDD4 measurement head setup
SDD4
Sample
Polycapillarylens
The ceramic board with electronic components
The collimator
The Peltier refrigerators and the Be windows
Peltierelements
Berilliumwindow
Berilliumwindow
Readout electronics + Data acquisition systemfor the SDD4
VPA
VPA
VPA
VPA fast/slow shaper
peak stretcher
peak stretcher
peak stretcher
peak stretcher
fast/slow shaper
fast/slow shaper
fast/slow shaper
ADC
FPGA
+
RAM
RESET
SEL
VLSI chip
HOST PC
Scheme of principle of the new fast acquisition system presently under development (the histogram is made ‘on board’)
Researchers involved: A.Longoni, C.Guazzoni, S.Buzzetti
PRESTAZIONI DEL NUOVO SISTEMA DI ACQUISIZIONE
1 10 100 1000 10000Input rate [kcps]
1
10
100
1000
Out
put r
ate
[kcp
s]Channel #1Channel #2Channel #3Channel #4Fitting: X*exp(-X*2200e-6)Y = X
Tau=450nsPT=920nsRT=1500nsST=60nsPUR Disabled
Rate performance
Some applications of themulti-element SDDs
The concept of the multi-element spectrometer for XRF elemental mapping
Researchers involved: A.Longoni, C.Fiorini
Poly-capillary X-ray minilens
MicrofocusX-ray generator
Sample
A polycapillaryX-ray lens
allows:
an higher photon fluxin a small excitation spot
Poly-capillary X-ray minilens
MicrofocusX-ray generator
SDD ring detector
A ring detector centeredon the excitation beam
allows
•a larger collection angle of the fluorescence
•an higher detection efficiency at low energy
A multi-element detector allows:
•an higher detection rate for the same total active area
The excitation-detection unit
CapillaryX-ray lens
Microfocus X-ray generator * W anode50 kV max DC voltage, 30 W max anode load
12 element SDD
The X-ray mini-lens parametersBeam FWHM in focus
30
35
40
45
50
55
60
65
70
75
0 5 10 15 20 25 30
E (keV)
FWH
M (u
m)
Gain in focus
0
500
1000
1500
2000
2500
3000
0 5 10 15 20 25 30
E (keV)
Gai
n
Measured with 15 µm pinhole
70 µm
2500
f1
L
f2
Φ
f1=40 mmf2=20 mmL=77 mmΦ=0.094 rad
The spatial resolution of the spectrometer - 1
MicrofocusX-ray generatorW anode
Poly-capillary X-ray minilens
SDD ring detector
Silicon wafer knife edge cut300 µm thick
x
Be window D
Knife-edge test
D=1mm FWHM=78µm(slightly out of focus)
Geology
6 mm
Chromite
0 1 2 3 4 5 6 7 8 9 10Energy [keV]
1
10
100
1000
Cou
nts
Si Ca
Cr
Fe
Ni
W
Chromite: main elements
6 mm
Lombard buckle – inlaid work (agemina) Second quarter of VII century A.C.Trezzo d’Adda, Italy
Ag Fe
Cu
7 mm
Roman (?) ring
Ag
Pb Si2 mm
Mretallurgy: study of an Iron-Nichel alloyFe Ni
0.5 mm0.5 mm
Fe Ni
Iron powder with Nickel grains partially diffused on the Iron surfaceduring the syntherization process at 1120 C
Biolology
Poly-capillary X-ray minilens
MicrofocusX-ray generator
SDD ring detector
Sample: Leaf
C substrate
A leaf feed with a fertilizer
K Ca Mn
Fe Cu
Leaf ‘fluorescence’ (detail)
Scanned area 6x6 mm, 61x61 points, 100µm x 100µm pitch, 0.5s meas time per point, 6 SDD activeMax counts/pixel: K 406 Ca 2386 Mn 1902 Fe 3822 Cu 6874
Leaf ‘radiography’ (detail)
Poly-capillary X-ray minilens
MicrofocusX-ray generator
SDD ring detector
Sample: Leaf
Ca substrate
Absorption of Kα Ca line (3.69 keV)Scan: 21x21points, 250 µm x 250 µm steps, measurement time 1s/point
TechnologyAlumina board for electronic circuits
Scanned area4x4mm2
Gold coating
Silver strips
41x41 sampled points100x100 µm steps1 s measurement time per point
AuAg Al
The Gamma ray imaging detectors
SDD arrays coupled with a scintillator crystal
Development of a small Anger Camera for high position resolution γ-ray imaging
Applications in Medical Imaging:
• compact diagnostic systems for human imaging(thyroid gland diagnostic, brain imaging, breast imaging..)
• small animal imaging systems with < 0.5 mm positionresolution
The first prototype of SDD - CsI(Tl) Anger camera
Milliporepaper
CsI(Tl) crystal
2.4 mm
C.Fiorini, et al., Nucl. Instr. Meth., Vol. A512, 2003.
Total area = 5 mm2×19 ~ 1cm2
CsI(Tl) thickness = 3 mmT = -10°C
E = 122 keV (57Co)
SDD - CsI(Tl) Anger camera: final results
⇒ intrinsic resolution~ 160 µm
ø collimator ~ 180 µm
E=122keV (57Co) ⇒ factor 10 better than conventionalAnger Cameras
500 µm
500 µm
0.5 mm
0.5 mm
0.71 mm
57Co position scan
γ-ray Imaging57Co source
lead slab
γ-ray detector 1 mm
0.5 mm
The monolithic array of 77 SDDs: front side
29 mm
26 mm
• 77 units, 8.7 mm2 each
⇒ active area = 6.7 cm2
• active area: 29 × 26 mm2
• two interconnection layersavailable (polysilicon, Al)
• output pads for bias/signals placed outsidethe active area
Detector back side
Anti-reflectivecoatings implementedExpected QE > 80%
lambda = 560nm
0 10 20 30 40 50 60 70 80 90Degrees
0
10
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30
40
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trans
mis
sion
bonding pads
Preliminary caracterization of the whole array:55Fe spectra measured with bias optimized for each unit
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room Tτshaping = 0.25µsVBACK optimized foreach unit: -76V ÷ -94V(alternatively R#1 canbe optimized for eachunit, with the same results)
noise is good anduniform amongall units
(3 units are not working)
The DRAGO project *(DRift detector Array-based Gamma camera for Oncology)
Purpose:development of a compactAnger Camera for γ-ray imagingwith sub-millimeter resolution
scintillator
77 SDD array
Peltier coolerflex cables to FE board
* Project INFN Gr.5 2003-05
The large-area SDDs
SDD 1cm2 x 3 for the experiment SIDDHARTAINFN – EU 6° program
Structuredside
Radiationentrancewindow
Unstructuredside
E ≈ 110 V/cm
E ≈ 80 V/cm
Detector Setup
e-
e+ toroidal H-target cell
scintillator = trigger
detector module 2 x 3 cm²
∑ 32 modules <-> 192 cm²
Conclusions
The Dectors here presented are today the best results of the “nearly old”idea of the the SDDs (E. Gatti and P. Rehak, 1983).
SDDs (under different commercial names) are nowadays widely used inseveral applications (SEMs, Synchrotrons, Portable XRF spectrometers, Mars exploration, …).Other devices derived from the original idea of Gatti and Rehak, the “fully depleted” PN-CCDs, are flying in a satellite for X-ray astronomy(XMM mission).New devices, similarly derived from the original idea, are on the way:CDDs, DEPMOS pixel arrays, avalanche SDDs, ….
The INFN has believed in SDDs and has supported their development,in cooperation with the MPI Halblaiterlabor, from the very beginning of these devices.