Solid State Detectors- 6 T. Bowcock

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

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

4 Oxygenated Si Introduce oxygen into the wafer before fabrication O2 permeated by diffusion –1100 to 1200 C Performance Manufacturer –e.g. Micron Furnace

5 Oxygenated Si

6 Trying to unfold the performance

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

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

9 P-type Si

10 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

11 Cryogenic Operation DELPHI detectors

12 Cryogenic Operation

13 Cryogenic operation

14 Cryogenic Operation

15 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?

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

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

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

19 Diamond Performance

20 Diamond Performance

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

22 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

23 Speculative Technology Plastic diodes New Si processing

24 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

25 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.

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

27 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(!)

28 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

29 Nanotechnology Look and manufacture things on the sub-nm scale Si(111) surface GaAs

30 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.

31 Nanotechnology If we could find a way of recording mip through a material –ultimate 0.1 nm scale detector –electronic (slow!) r/o

32 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

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

34 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

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

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

37 Multiple Scattering Multiple Coulomb Scattering About 1mr /p for 300 microns of Si 1 micron at 10GeV 1 cm

38 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

39 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?

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

41 Momentum measurement R h d 4hR=d 2 P=0.3BR

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

43 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

44 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