Solid State Detectors- 6 T. Bowcock
1 Position Sensors 2 Principles of Operation of Solid State Detectors 3 Techniques for High Performance Operation 4 Environmental Design 5 Measurement of time 6 New Detector Technologies Schedule
New Technologies • Si developments • Oxygenated Si • p-type Si • Diamond • Cryogenic Si • Deep Sub-Micron Processing • Nanotechnologies • Physics
Introduce oxygen into the wafer before fabrication O2 permeated by diffusion 1100 to 1200 C Performance Manufacturer e.g. Micron Furnace Oxygenated Si
Oxygenated Si Trying to unfold the performance
Oxygenated Si • Performance with diodes superb • factor 2 improvement • Strip performance seems to be about 20% better
As irradiated n-type use n-strips Advantages single sided processing detector does not invert Slightly degraded performance p-type Si
Lazarus Effect cool detector down it appears to repair itelf standard technology but cold diodes Strip detectors irradiated while cold double sided monitor both p and n side Cryogenic Operation
Cryogenic Operation • DELPHI detectors
Cryogenic Operation • Lazarus effect could be observed • charge injection into a reverse biased detector • filling traps with electrons • uncontrolled • fine tuned with temperature&frequency • Is there a way to control this?
Use Diamond as a material radiation hard cheap(!) large area Diamond
Diamond Formation • Chemical Vapour Deposition(CVD) Larger crystals 20-30 microns Small crystals of order microns substrate
Diamond Charge • Charge produced by ionization • Traps • interstitials • vacancies • shallow and deep • Charge Collection Distance
Diamond • Very high fluences • at current radiation levels does not out perform Si • limited charge collection distance • small crystals?
Summary of Current New Technologies • Si reaching maturity • extension such as O2 fine tune performance • New generation of materials (e.g. diamond) can be used under extreme conditions
Speculative Technology • Plastic diodes • New Si processing
“In 1989 it was discovered that a conjugated polymer, poly(1,4-phenylenevinlyene) (PPV), could be used as a light emitting layer in LEDs. This discovery has wide ranging commercial possibilities, e.g., the preparation of lightweight, large, multicoloured, flat panel displays for televisions and computer screens is now a realistic possibility”. (D. Burn). Organic diodes PPV
Polymer Diodes • A simple LED consists of a polymer sandwiched between two metal electrodes. • The electrons and holes charges move in opposite directions and if they end up on the same polymer chain then they can form a singlet excited state which can decay and emit light • The colour of the light is dependent on the HOMO-LUMO energy gap.
TV screens very commercial If becomes viable perhaps we can benefit R&D flexible robust cheap Polymer diodes
Current generation of processing at 0.16 level or better. CMOS designs intrinsically radiation hard bulk effects vanish Better readout chips higher density improved VLSI low cost high radiation pixel detectors(!) Deep Sub-Micron Processing
Deep Sub-Micron • Large areas • High resolution • What we need for large area high quality production of detectors • COST inhibitive at the moment • CCD large scale high resolution
Look and manufacture things on the sub-nm scale Si(111) surface GaAs Nanotechnology
Nanotechnology • A 200 Å x 200 Å constant current STM image of an alpha-Fe2O3(0001) surface . This image shows two types of island, which are ordered, forming a hexagonal superlattice. The unit cell of the superlattice has a characteristic dimension of 40 ± 5 Å and is rotated by 30 degrees from the alpha-Fe2O3(0001) lattice.
Nanotechnology • If we could find a way of recording mip through a material • ultimate 0.1 nm scale detector • electronic (slow!) r/o
From applied physics point of view all these technologies are very interesting How applicable are they to particle physics? Ultimate measurement as resolution improves Physics
Particle Physics • Detector resolution • Vertex • topology of vertex • decay lengths • Tracking • momentum of particles • usually large volume gas detector
Vertex Finding • Heavy quarks decay quickly • b in about 1ps (mm in current machines) • t in fs or less (where primary hadronisation occurs) • Increasing resolution would improve our separation of b-quarks from the primary collision • decrease luminosity
Vertex Finding If you have good resolution you don’t need to get so close
Vertex Finding • In telescope • limited by mechanical accuracy • thermal expansion etc • Practical limit to resolution JUST from these considerations O(1 micron) • Multiple Scattering
Multiple Scattering • Multiple Coulomb Scattering • About 1mr /p for 300 microns of Si 1 micron at 10GeV 1 cm
Multiple Scattering • Angles give mass resolution for hadronic decays • Already ms limited in many cases • slow pions < 0.5 GeV/c • HEP seems to be less interested in hadronic decays masses than decay rates • CPT not approachable by this method
Vertex Finding • For fast (active r/o) devices we are probably within a factor 10 of limit with current technology • Topology of the decays • thin retaining signal • surface nano-readout • alignment?
Tracking • High resolution detectors useful • detectors have large gas volumes • large volumes make calorimetry expensive • Momentum measurement
Momentum measurement 4hR=d2 h P=0.3BR d R
Momentum Measurement • Measurement of sagitta is key • multiple scattering counts • Si usually not used • Time Projection Chamber (?)
Summary (New Technology) • We are close to performance limits (for what we need) … micron level precision active detectors • New Technology gives performance in extreme cases • e.g. radiation • extreme resolution • cost
Conclusion • Detectors have developed in 100yrs • Understood basic solid state detectors • Research that is being followed • New Horizons/Technologyes • Up to you to have the good ideas • and find the physics that needs it