Solid State Detectors 6 T Bowcock 1 Schedule

Solid State Detectors- 6 T. Bowcock 1

Schedule 1 2 3 4 5 6 Position Sensors Principles of Operation of Solid State Detectors Techniques for High Performance Operation Environmental Design Measurement of time New Detector Technologies 2

New Technologies • Si developments – Oxygenated Si – p-type Si • • • Diamond Cryogenic Si Deep Sub-Micron Processing Nanotechnologies Physics 3

Oxygenated Si • Introduce oxygen into the wafer before fabrication • O 2 permeated by diffusion • Furnace – 1100 to 1200 C • Performance • Manufacturer – e. g. Micron 4

Oxygenated Si 5

Oxygenated Si Trying to unfold the performance 6

Oxygenated Si • Performance with diodes superb – factor 2 improvement • Strip performance seems to be about 20% better 7

p-type Si • As irradiated n-type – use n-strips • Advantages – single sided processing – detector does not invert • Slightly degraded performance 8

P-type Si 9

Cryogenic Operation • 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 10

Cryogenic Operation • DELPHI detectors 11

Cryogenic Operation 12

Cryogenic operation 13

Cryogenic Operation 14

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? 15

Diamond • Use Diamond as a material – radiation hard – cheap(!) – large area 16

Diamond Formation • Chemical Vapour Deposition(CVD) Larger crystals 20 -30 microns Small crystals of order microns substrate 17

Diamond Charge • Charge produced by ionization • Traps – interstitials – vacancies – shallow and deep • Charge Collection Distance 18

Diamond Performance 19

Diamond Performance 20

Diamond • Very high fluences – at current radiation levels does not out perform Si – limited charge collection distance • small crystals? 21

Summary of Current New Technologies • Si reaching maturity – extension such as O 2 fine tune performance • New generation of materials (e. g. diamond) can be used under extreme conditions 22

Speculative Technology • Plastic diodes • New Si processing 23

Organic diodes • “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). PPV 24

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 they can form a singlet excited state which can decay and emit light • The colour of the light is dependent on the HOMOLUMO energy gap. 25

Polymer diodes • TV screens – very commercial • If becomes viable perhaps we can benefit • R&D – flexible – robust – cheap 26

Deep Sub-Micron Processing • 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(!) 27

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 28

Nanotechnology • Look and manufacture things on the sub-nm scale • Si(111) surface • Ga. As 29

Nanotechnology • A 200 Å x 200 Å constant current STM image of an alpha-Fe 2 O 3(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. Fe 2 O 3(0001) lattice. 30

Nanotechnology • If we could find a way of recording mip through a material – ultimate 0. 1 nm scale detector – electronic (slow!) r/o 31

Physics • From applied physics point of view all these technologies are very interesting • How applicable are they to particle physics? • Ultimate measurement as resolution improves 32

Particle Physics • Detector resolution – Vertex • topology of vertex • decay lengths – Tracking • momentum of particles • usually large volume gas detector 33

Vertex Finding • Heavy quarks decay quickly – b in about 1 ps (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 34

Vertex Finding If you have good resolution you don’t need to get so close 35

Vertex Finding • In telescope – limited by mechanical accuracy – thermal expansion etc • Practical limit to resolution JUST from these considerations O(1 micron) • Multiple Scattering 36

Multiple Scattering • Multiple Coulomb Scattering • About 1 mr /p for 300 microns of Si 1 micron at 10 Ge. V 1 cm 37

Multiple Scattering • Angles give mass resolution for hadronic decays • Already ms limited in many cases – slow pions < 0. 5 Ge. V/c • HEP seems to be less interested in hadronic decays masses than decay rates – CPT not approachable by this method 38

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? 39

Tracking • High resolution detectors useful – detectors have large gas volumes – large volumes make calorimetry expensive • Momentum measurement 40

Momentum measurement 4 h. R=d 2 h P=0. 3 BR d R 41

Momentum Measurement • Measurement of sagitta is key – multiple scattering counts – Si usually not used – Time Projection Chamber (? ) 42

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 43

Conclusion • • • Detectors have developed in 100 yrs 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 44