Folie 1

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The WODEAN Projectpresent status
Gunnar LindstroemUniversity of Hamburg
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Experimental request Detector property  
Reliable detection of mips S/N 10 reachable
with
                                                 
     
Proton-proton collider Energy 2 x 7
TeV Luminosity 1034 Bunch crossing every 25
nsec Rate 40 MHz pp-collision event rate
109/sec (23 interactions per bunch
crossing) Annual operational period 107
sec Expected total op. period 10 years
LHC properties
period of 10 years low dissipation power at
moderate cooling   Silicon pixel and microstrip
detectors meet all requirements for LHC How about
future developments?
LHC-Challenge for Tracking Detectors

employing minimum minimum detector thickness
material budget
High event rate excellent time- (10 ns)
high track accuracy position resolution (10
µm)
Silicon Detectors Favorite Choice for Particle
Tracking
Example Large Hadron Collider LHC, start 2007

• Proton-proton collider, 2 x 7 TeV
• Luminosity 1034
• Bunch crossing every 25 nsec, Rate 40 MHz
• event rate 109/sec (23 interactions per bunch
  crossing)
• Annual operational period 107 sec
• Expected total op. period 10 years

LHC properties
Experimental requests Detector
properties Reliable detection of mips
S/N 10 High event rate
time position resolution high track accuracy
10 ns and 10 µm Complex
detector design low voltage
operation in normal
ambients Intense radiation field
Radiation tolerance up to during 10 years
1015 hadrons/cm² Feasibility, e.g.
large scale
availability 200 m² for CMS
known technology, low cost
! Silicon Detectors meet all Requirements !
Intense radiation field Radiation tolerance up
to
throughout operational 1015 1MeV eq. n/cm²
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LHC ATLAS Detector a Future HEP Experiment
Overall length 46m, diameter 22m, total
weight 7000t, magnetic field 2T ATLAS
collaboration 1500 members
principle of a silicon detector solid state
ionization chamber
micro-strip detectorfor particle tracking
2nd general purpose experiment CMS, with all
silicon tracker!
For innermost layers pixel detectors
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Main motivations for RD on Radiation Tolerant
Detectors Super - LHC

• LHC upgrade ?LHC (2007), L 1034cm-2s-1
  f(r4cm) 31015cm-2
• ?Super-LHC (2015 ?), L 1035cm-2s-1
  f(r4cm)
  1.61016cm-2
• LHC (Replacement of components) e.g. - LHCb Velo
  detectors (2010) - ATLAS Pixel B-layer
  (2012)
• Linear collider experiments (generic RD)Deep
  understanding of radiation damage will be
  fruitful for linear collider experiments where
  high doses of e, g will play a significant role.

? 5
CERN-RD48
CERN-RD50
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Radiation Damage in Silicon Sensors

• Two types of radiation damage in detector
  materials
• ? Bulk (Crystal) damage due to Non Ionizing
  Energy Loss (NIEL
• - displacement damage, built up of crystal
  defects
• I. Increase of leakage current (increase of
  shot noise, thermal runaway)
• II. Change of effective doping concentration
  (higher depletion voltage, under- depletion)
• III. Increase of charge carrier trapping
  (loss of charge)
• ? Surface damage due to Ionizing Energy Loss
  (IEL) - accumulation of charge in the
  oxide (SiO2) and Si/SiO2 interface
  affects interstrip capacitance (noise factor),
  breakdown behavior,
• ! Signal/noise ratio most important quantity !

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Deterioration of Detector Properties by
displacement damage NIEL
Point defects clusters
Dominated by clusters
Damage effects generally NIEL, however
differences between proton neutron damage
important for defect generation in silicon bulk
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Radiation Damage Leakage current
Increase of Leakage Current
. with particle fluence

• Leakage current decreasing in time
  (depending on temperature)
• Strong temperature dependence

• Damage parameter ? (slope in figure)
  Leakage current
  per unit volume
  and particle fluence
• ? is constant over several orders of fluenceand
  independent of impurity concentration in Si ?
  can be used for fluence measurement

Consequence Cool detectors during
operation! Example I(-10C) 1/16 I(20C)
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Radiation Damage Effective doping concentration
Change of Depletion Voltage Vdep (Neff)
. with particle fluence
Hamburg model
Type inversion Neff changes from positive
to negative (Space Charge Sign Inversion)
before inversion
after inversion
n
n
p
p
Consequence Cool Detectors even during beam off
(250 d/y)alternative acceptor/donor
compensation by defect enginrg.,e.g. see
developm. with epi-devices (Hamburg group)
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Summary

• Silicon Detectors in the inner tracking area of
  future colliding beam experiments have to
  tolerate a hadronic fluence of up to Feq
  1016/cm²
• Deterioration of the detector performance is
  largely due to bulk damage caused by non ionizing
  energy loss of the particles
• Reverse current increase (originating likely from
  both point defects and clusters) can be
  effectively reduced by cooling. Defect
  engineering so far not successful
• Change of depletion voltage severe, also affected
  by type inversion and annealing effects.
  Modification by defect engineering possible, for
  standard devices continuous cooling essential
  (freezing of annealing)
• Charge trapping is the ultimate limitation for
  detector application, responsible trapping
  centers widely unknown, cooling and annealing
  have little effects

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Outline for a correlated project

• Main issue charge trapping, the ultimate
  limitation for detector applications in future
  HEP experiments source for trapping so far
  unknown! Maximum F to be tolerated 1.5E16
  n/cm².
• Charge trapping independent of material type
  (FZ, CZ, epi) and properties (std, DO,
  resistivity, doping type). not depending on
  type of irradiating particles and energy (23 GeV
  protons, reactor neutrons), if F normalised to
  1 MeV neutron equivalent values (NIEL). In
  contrast to IFD and Neff there are almost no
  annealing effects (in isothermal annealing
  studies up to 80C).
• Correlated project use all available
  methods DLTS, TSC, PITS, PL, trecomb, FTIR,
  PC, EPR concentrate on single material (MCz
  chosen with possibility of std. FZ for checking
  of unexpected results. Use only one type of
  irradiation, most readily available (TRIGA
  reactor at Ljubljana) and do limited number of F
  steps between 1E12 and 3E16 n/cm².

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1st WODEAN batch sample list
150 samples n-MCz lt100gt1 kOcm (OKMETIC, CiS) 84
diodes, 48 nude standard, 16 nude thick
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Irradiations
Date November 2006 Delivery to Hamburg 8
January 2007 Distribution to WODEAN members 9
February 2007 Important Info about
irradiations F 1E15 n/cm² T 20C, duration
10 min F 2E15 n/cm² high flux dF/dt 2E12
n/cm²s Temperature increase during
irradiation 3E15 t 25 min, temp. rising to
70-80C within 15 min (then saturating) 1E1
6 t 80 min, temp. 70-80C 3E16 t 4h,
10min, severe self anneal expected
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2nd WODEAN batch sample list
90 samples n-FZ lt111gt, 2 kOcm (Wacker, STM) 67
diodes, 24 nude thick samples
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Irradiations
Date EarlyApril 2007 Delivery to Hamburg
foreseen 11 June 2007 Distribution to WODEAN
members foreseen end June 2007 Important Info
about irradiations (as for 1st batch) F 1E15
n/cm² T 20C, duration 10 min F 2E15
n/cm² high flux dF/dt 2E12 n/cm²s Temperatur
e increase during irradiation 3E15 t 25
min, temp. rising to 70-80C within 15 min
(then saturating) 1E16 t 80 min, temp.
70-80C 3E16 t 4h, 10min, severe self
anneal expected
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Hamburg, 08-May-2007 WORKSHOP ON DEFECT ANALYSIS
WODEAN -RD50 internal project- I. Project
Object The project is based on discussions during
the first WODEAN meeting, which was proposed
during the RD50 workshop at CERN, November 2005
and finally held in Hamburg, 24/25 August, 2006.
The main object was to address the problem of
defect generation in detector grade silicon using
a variety of available techniques. By doing this
in a correlated project it is hoped to get more
insight in defect creation and a better
understanding of their implications for the
operability in extremely harsh radiation
environments. Thus the main focus is set by the
application of silicon detectors in the innermost
tracking area of the future SLHC experiments,
where accumulated hadron fluences of up to
1.51016 cm-2 (1 MeV neutron equivalent) have to
be tolerated. Surveying the main effects of
radiation damage for detector properties (reverse
current increase, change of depletion voltage and
reduction of the charge collection for traversing
minmum ionizing particles), the latter effect was
screened out to be most challenging. Indeed
charge carrier trapping would ultimately limit
the applicability of silicon detectors.
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II Project Outline Guide lines Restrictions for
the main objects such that results can be
obtained within a reasonable time of 1 year with
possible extension for a 2nd year. Common
correlated project making optimum use of all
available methods, intercomparability of
obtained results (same material, identical
irradiation, identical annealing steps etc.) As
charge trapping is largely independent of the
detector material, the project is restricted to
MCz (magnetic Czochralski) and in a 2nd step to
StFZ (standard float zone), both n-type As charge
trapping after hadron irradiation is largely
independent of particle type and energy (if
fluence is NIEL normalised to 1 MeV neutrons),
irradiations to be performed at the TRIGA reactor
Ljubljana Maximum (1MeV neutron equivalent)
hadron fluence expected in SLHC is 1.51016 cm-2.
Irradiations should therefore cover a range from
values usable for the most sensitive methods
(DLTS) up to well above 11016 cm-2 in manageable
steps.Methods for investigations C-DLTS Univ.
Hamburg, Oslo, Minsk I-DLTS Univ. Florence TSC
Univ. Hamburg, NIMP Bucharest PITS ITME
Warsaw PL Kings College London, ITME
Warsaw Lifetime Univ. Vilnius FTIR Univ.
Oslo PC Univ. Vilnius EPR NIMP Bucharest, ITME
Warsaw Detecor characteris. (C/V, I/V, TCT)
CERN-PH, Univ HH, JSI Ljubljana
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Memberlist with affiliation NIMP Bucharest
Sergiu Nistor, Ioana Pintilie (also guest in
Hamburg Univ.) CERN-PH Michael Moll Hamburg
University Eckhart Fretwurst, Gunnar Lindstroem,
Ioana Pintilie (from NIMP) Florence University
Mara Bruzzi, David Menichelli JSI Ljubljana
Gregor Kramberger Kings College London Gordon
Davies Minsk University Leonid Makarenko Oslo
University Bengt Gunnar Svensson, Leonid Murin
(guest from Minsk) Vilnius University Eugenius
Gaubas, Juozas Vaitkus ITME Warsaw Pawel
Kaminski, Roman Kozlowski, Mariusz Pawlowski,
Barbara Surma Needs to be updated!, Sergiu
Nistor resigned, new members Anfrey Aleev
(ITEP)? III. Present Status A first batch of 120
different MCz samples (material from Okmetic
diodes and nude samples processed by CiS, 3 mm
thick samples for FTIR and EPR from CERN) had
been irradiated at the TRIGA reactor in November
2006 and distributed to the different
collaborators. 11 irradiation fluences were
chosen between 31011 and 31016 cm-2 with the
smallest values for DLTS and the largest ones for
EPR. A 2nd batch of FZ samples had been sent to
Ljubljana and will be irradiated soon. First
results on the measurements as well as an upgrade
of the project program will be discussed in the
2nd WODEAN workshop scheduled on 2nd and 3rd June
2007 in Vilnius. A summary will then be presented
on the following RD50 workshop.
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IV. Project Budget Proposal Total budget
breakdown Material-, processing, masks, special
preparations 35.000,- CHF Subcontracted
analysis 10.000,- CHF Total
budget 45.000,- CHF Requested support from
RD50 common fund MCz- and FZ material
5.000,- CHF Processing 15.000,- CHF Analysis
(SIMS, spreading resistance,) 10.000,-
CHF Total requested support from RD50 30.000,-
CHF Contributions from WODEAN members CERN-EP
2.000,- CHF Florence University 2.000,-
CHF Hamburg University 8.000,- CHF Oslo
University 3.000,- CHF All other
Institutes contributions in kind Total
contribution from WODEAN members 15.000,-
CHF It is proposed that the finacial management
for the RD50 support will be handled by the
detector group, Institute for Experimental
Physics, Hamburg University.
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Finally
Last changes to the application as internal
project accepted as is what did we learn
this meeting discussion about overview report
for RD50 modifications for working program what
else should be done with existing MCz samples,
isochronal anneal! interchanging results
inbetween workshops continuously next
workshop date end 2007 Changes to WODEAN member
list Diode characterisation M. Moll (CERN-PH)
included I-DLTS D. Menichelli (Florence)
observer (manpower problems) EPR Sergiu Nistor
(NIMP) observer (future participation possible)