1. The UHH Detector Laboratory
Universität Hamburg
Institut für Experimentalphysik
Detektorlabor
Doris Eckstein
MC-PAD Kick-Off Meeting, CERN, 13./
Outline:
Projects
Expertise and Infrastructure
Examples

2. The Institute of Experimental Physics
has groups working on:
Particle Physics and Detector Physics
ATLAS, CMS, ZEUS, H1, HESS, ILC, OPERA
Accelerator Physics
FLASH, PETRA III, XFEL, ILC
Laser- and X-Ray Physics
DYNAMIX, X-Ray Spectroscopy, STM, SXRD
Physics Department

3. R&D Projects of the Detector Lab
Development of radiation hard silicon detectors
Marie Curie International Training Network MC-PAD:
P2 ‘Hybrid Pixel Detectors’ and
P3 ‘Radiation Hard Crystals / 3D Detectors’
RD50 Collaboration:
Radiation hard Silicon materials/sensors
CMS SLHC upgrade:
Central European Consortium – Silicon Sensors for tracking at intermediate to large radii
Helmholtz Alliance:
Virtual Detector Lab and radiation hard silicon sensors for SLHC
HPAD-XFEL

4. Silicon Detectors for Vertexing and Tracking
are used for vertexing, lifetimes, triggering, tracking, even dE/dx
are used in all current HEP experiments
detect MIPs
are fast (~10ns) and precise (~10μm)
(crazy geometries, run in vacuum, cover large surface)
are radiation tolerant
LHC starting 2008:
Luminosity L = 1034 cm-2s-1
in 10 years (500 fb-1) F (r=4cm) ~ 3·1015 cm-2
Oxygenated Silicon (ROSE-Collaboration RD48)
replacement might be necessary
sLHC starting 201x:
Luminosity L = 1035 cm-2s-1
in 5 years (2500 fb-1) F (r=4cm) ~ 1.6·1016 cm-2
new materials/technologies under investigation (RD50 Collaboration)

5. Radiation Damage in Silicon Sensors
Two general types of radiation damage:
Bulk damage due to Non Ionizing Energy Loss
- displacement damage, built up of crystal defects –
Change of Effective Doping Concentration Neff
type inversion
higher depletion voltage  possibly under-depletion  loss of signal, increased noise
junction moves from p+ to n+ side
influenced by impurities in Si (oxygen, carbon,…)  defect engineering, material dependence!
Increase of Leakage Current
shot noise  thermal runaway, power consumption  hard to bias
 temperature dependent  need cooling
Increased carrier Trapping
Charge loss  at 1016cm-2 λ≤20μm charge collection distance!
Surface damage due to Ionizing Energy Loss
accumulation of charge in the oxide (SiO2) and Si/SiO2 interface
 inter-strip capacitance (noise factor), breakdown behavior, …
CMS
MC-PAD
RD50
HPAD-XFEL

6. R&D to develop materials, technologies and simulations for
Silicon sensors modules at intermediate to large radii of a
new CMS tracker for SLHC
Establish a sensor technology valid for the outer radii of the tracker
Investigate the maximum durable irradiation fluence
 minimum possible radius
Stick to planar technology and strixel-like structures, with the possibility of inlcuding a 2nd metal layer for signal routing
Provide a single connection technology and minimize material budget by combining sensor and readout

7. Expertise and Infrastructure
Irradiation campaigns
(CERN, Ljubljana, Stockholm, Darmstadt, Karlsruhe, DORIS,…)
Macroscopic damage vs. time/annealing for different materials
Leakage current Ileak  I/V (Probe stations, also cooled)
Neff  Vdep  C/V (Probe stations, also cooled)
CCE  τe,h  Transient Current Technique
Nox, Neff  sensor stability  C/V (Probe station, also cooled)
evolution with time  annealing (ovens)
overall performance  multi-channel TCT (new)
test beam
Microscopic damage vs. time/annealing for different materials:
Thermally Stimulated Current, Deep Level Transient Spectroscopy
characterisation of damage levels (introduction rate, energy level, )
kinetics vs. time/annealing
relate to macroscopic damage
Overall detector performance
Multi-channel TCT
Test beam
Incorporate results I. and II. into simulation of
sensor “static” (ISE TCAD)
charge collection

8. Optimization of Sensor Design - Strategy
Study of Macroscopic Properties through IV, CV, TCT
Study of Microscopic Defects
through DLTS, TSC
 Neff, I, e,h depending on Doping, Irradiation, Annealing
Sensor Simulation/ Optimization E, I, C as function of Irradiation, Material,...
Simulation of Carge Collection in Detector dE/dx  sensor  FE electronics
 Efficiency, spatial resolution, …
Verification through multi-channel TCT, Testbeam

9. Example Setup: Multi-Channel TCT
TCT (Transient Current Technique) records the time-resolved current of the device under test.
Inject laser light  record pulse shape
With multiple channels: add sensitivity to position, record neighbouring strips/ pixels
Example: 300 V, Spotsize FWHM 5 µm
injection of 660 nm light from backside (holes)
optics
high intensity sub-ns laser
2.5 GHz Scope
linear tables
defined set-up
32 channels
automated control (PC)

10. Example: Microscopic - Macroscopic
Radiation damage – reverse current
No known point defects responsible – cluster defects?
found a means to measure cluster concetration by using the bistability of E4 and E5
n-irradiated, 3x1011 cm-2
C(T0)-C(Tanneal) vs. I(T0)-I(Tanneal)

11. Summary
Aims:
quantitative understanding of Si sensor performance in harsh radiation environment
improve sensor performance
optimize sensor design (for given material, dose/fluence)
Techniques:
Measurements
macroscopic: I/V, C/V, TCT, multi-TCT
microscopic: DLTS, TSC
Simulations of sensor ‘static’ and ‘dynamic’ properties