Applications of Silicon Detectors

Transcription

1 SCIPP Applications of Silicon Detectors Motivation Principle of Operations The Rise of Silicon Detectors Applications Charged Particle Tracking Photon Detection

2 Precision Particle Tracking Detectors In Particle Physics, many new phenomena tend to be associated with heavy quarks. The Higgs search will depend on tagging heavy flavor jets, CP violation is being measured in the b system. Heavy quarks have a finite life time τ, and can be identified by the decay length in the lab z γβcτ (= 250um in BaBar). Detached Vertexes In B and anti-b Primary Z Vertex Vertexing precision depends on: distance of the detectors from the interaction point, the lever arm, and the intrinsic position resolution of the detector This requires detectors in close proximity (few cm) of the beams with an intrinsic position resolution of 10-25um. High particle densities in jets require fast, fine-grained detectors. This is possible only with semiconductor detectors.

3 Particle Tracking Detectors for Theorists Choose a fine-grained detector to localize charged particles: Passing of particle leaves a trail of temporal ionization (>10,000e) (see next) Take advice from your local guru and collect it electronically -> apply electric field, record tiny current I s (<ua in 10 ns) = signal Problem: Resistivity of detector material : I n = V/R gives large current Way out: block current with capacitor Problem: large current still gives background noise ~ I n Ways out: Ultra-high resistivity materials (Diamonds, SiC, few Mohm-cm) Reverse biased diode on Si (few kohm-cm, industry grade)

4 Electrostatics of Silicon Strip Detectors Resistivity given by concentration of dopants N (donors or acceptors). Charge can t be collected from the conductive bulk : have to deplete it of mobile carriers (e), leaving the bulk charged Depletion depth depends on bias voltage Capacitance measured the depletion depth W 1/C 2 V Bias

5 Dynamics of Silicon Strip Detectors Charge Collection: Drifting Charges Induce Charges on Electrodes Drift Velocity E operating field, µ mobility Induced Charges V ql : Weighting Potential (Ramos, 1937) Signal Current due to drifting charges i k = -qµ Ε(x) F k (x) F k (x) : Weighting Field (Cap) Collection Time Scale Signal ends when charge arrives at the strip

6 Further Reading for the Curious

7 Signal in Tracking Detectors Charged Particle Energy Loss (aka Stopping Power, Linear Energy Loss LET) Signal-to-Noise Ratio: Signal ~ Thickness Noise ~ Area, 1/ τ s Directional Information compromised by Multiple Scattering Energy loss de/dx (MeV cm 2 g 1 ) Silicon ~1/β 1.5 measure p MIP Bethe-Bloch p/m = βγ e ± Electron momentum (MeV/c) Muon momentum (MeV/c) Multiple Scattering angle Rad µ ± Without radiative losses -> Thin, low z materials -> Improves at High Energy Radiation Length X o

8 Properties of Silicon Strip Detectors Reverse Bias of junction: only thermal current generation Scale : Band gap 1.12eV vs. kt = 1/40eV: huge Boltzmann factor Cooling needed only in ultra-low noise applications. Wafer thickness 300um = 0.3%RL: 23k e-h pairs Depletion Voltage ~ thickness 2 : <100V Collection Time of e-h pairs: ~20ns Area is given by wafer size: 4 & 6 => Ladders Readout electronics (S/N typically > 20) Al µm SiO 2 p + implant at ground n + implant holes Depletion region. Charged particle traversing region produces ~80 electron/hole pairs per micron µm Al at ~ 100V

9 Evolution of Silicon Detectors Large Area Double-sided Si Drift 3-D Hybrid Pixels n n p p n n n n Monolythic: CCD, MAP

10 The Rise of Silicon Detectors Development of Area of SSD and # of Electronics Channels follow Moore s Law Larger - CMS 10M Channels, 230m 2 Faster - ATLAS 22ns Cheaper - CMS ~$5/cm 2 Silicon Area [m 2 ] o O: SCIPP Mark Year GLAST o o CMS ATLAS NOMAD D0 AMS-02 Agile MEGA LEP AMS-01 CDF o o o BaBar LPS CDF Pamela # of Electronics Channels [in k] Mark2 CDF LEP LPS WIZARD Year BaBar D0 CDF AMS-01 NOMAD AMS-02 GLAST Agile Pamela CMS ATLAS MEGA

11 The Rise of Silicon Detectors Silicon Area vs. # of Electronics Channels 100 Limited Resources (Power) in Space GLAST CMS ATLAS Area [m 2 ] Mark2 NOMAD AMS-02 Agile MEGA AMS-01 D0 LEP CDF BaBar CDF LPS Pamela Long Ladders possible with: Bonding and Encapsulation # of Channels [k] Edge joint and wire bonds before encapsulation

12 The Rise of Silicon Detectors Trends in the Cost of Silicon Detectors Cost of processing wafers reduced ~ 4x Increased Area 4 -> 6 Better utilisation of area Cost /Area [ $/cm 2 ] Improved Quality e.g. GLAST detectors: <2nA/ cm 2 <2*10-4 bad channels 1 Cost /Area of Single-sided Silicon Strip Detectors (double-sided factor 2.5 higher) Mark 2 DC coupl. ZEUS DC coupl. Nomad (untested) Year GLAST "4" GLAST 6" 4 " Blank Wafer Price 6 " Wafer Size ATLAS CDF CMS 4" 6" (Guestimates by HFWS)

13 DC (Drift Chamber) vs. SSD (Silicon Strip Detector) What to do next? Excellent Control E, Gain DC Many tricky parts Job Shoppers Discreets Hybrids E, T, HV, Gas, Whiskers δ-rays, sparks Tasks Team Electrostatic Design Manufacturing Assembly Read out Operations Performance Excellent Silicon Valley Silicon Valley, Modular Silicon Valley ASICs Never Calibrate Low Power Fast, SSD Big S/N

14 Typical Low Tech University Jobs What to do next?

15 Typical Low Tech University Jobs What to do next?

16 Tracking Milestones: Fixed Target That s how it all began Fixed Target experiments with high rates: Silicon Detectors ~ 5cm x5cm Na11 (ACCMOR), Na14, E706. E691 Detect heavy decaying particles through their finite decay distance What to do next? Fanout-Cables Amplifiers

17 Tracking Milestones: Vertex Detectors The big step forward in Mark2: ASIC s (A. Litke et al) Vertex Detector Paradigm ASIC s, Few thin layers, Close in. Every LEP Experiment has a Vertex Detectors: ALEPH {A. Litke et al) Double-Sided AC-coupled

18 Tracking Detectors: CCD 300M pixel CCD device for SLD (A. Seidem, T. Schalk, B. Schumm) Few um resolution in two coordinates Follow the (Industrial) Leader k 2 DMT CFHT Megacam WFHRI_1 SAO/MMT Megacam SNAPsat Number of pixels UH8K EROS2 QUEST NOAO 8k MACHO UH4K 2k 2k SLD X CFH12K SDSS NAOJ RGO BTC NOAO 4K CFHT MOCAM Suprime 16k 2 8k 2 4k Year UW ESO OmegaCAM NOAO 8k (thinned) DEIMOS UH8K (thinned) MAGNUM CTIO 8k ESO 8k MSSSO/WFI Detached Vertexes In B and anti-b Primary Z Vertex

19 Tracking Milestones: Speed and Rad.Hardness LPS at HERA (D. Dorfan, N. Spencer, J. DeWitt, N. Cartiglia, E. Barberis, A. Seiden, D. Williams, HFWS ) Fixed Target at Collider Importance of Electronics: rad hard fast low noise low power 56 planes, 50k channels Elliptical shapes! 2mm from 800GeV beam Hadron-Machines: Radiation Damage 2 chip set: Bipolar+CMOS

20 Tracking Milestones: Highest Luminosity LHC ATLAS: Silicon Tracker (A. Seiden, D. Dorfan, A. Grillo, N. Spencer, S.Kachiguin, F. Rosenbaumm, M. Wilder, HFWS) Simple Detectors,Optimized Electronics Thermal management Vertex Detector Inner Detector Change in Paradigm: coverage of large area electronics inside tracker volume Temperature Range : -17 o C (cooling pipe) to +16 o C (ASICs)

21 Tracking Milestones: Highest Luminosity LHC Continued Paradigm Change: >20 layers of Si, outside radius : ~1.1m ~1R.L. in tracking volume almost exact size of old wire chambers! Silicon has arrived: all Silicon Inner Detector Si Area 223m 2, -6 Wafers (Ariane Frey et al)

22 Technology Transfer of Silicon Detectors Protons Biology Small-scale X-rays Medicine Large-scale γ-rays Space Science C.Rays Charged Particle Tracking in HEP Industrial Base

23 Si Tracking in Space: Sileye Sileye Investigate light flashes seen by Cosmo-/Astro-nauts during Orbital flights. Cosmonaut Adveev on Mir Occurrence of flashes well correlated with areas of high flux of Cosmic ray particles.

24 Photon Detection in Astronomy: Direction, Direction,.. Mass attenuation coefficient (cm 2 g 1 ) Optical- X-rays Need Focus: Lenses Mirrors Collimators Coded Masks Proximity Photon Attenuation Coefficient Rayleigh (coherent) Compton total Silicon λ varies by 10 5! pair production ,000 10,000 Photon energy (MeV) Compton Partial Direction γ Attenuation of Phtotons N(x) = N o e - λ x Attenuation coefficient λ= (7/9)/X o anticoincidence shield < 0.3% Conversions in one SSD! photoelectric Pair- Production Direction conversion foil particle tracking detectors e + e calorimeter (energy measurement)

25 GLAST: Pair Conversion Telescope Gamma-rays convert into e + e - pairs, are tracked and their energy measured Gamma is reconstructed from e + e - tracks charged particle γ anticoincidence shield conversio n foils Reconstruct Vertex particle tracking detectors calorimeter (energy measurement) e+ e- Converter Thickness t Conversion Probability ~ t Pointing RMS ~ t New Paradigm:Add material into tracking volume: Maximize Number of Converters 2 1

26 GLAST Gamma-Ray Large Area Space Telescope An Astro-Particle Physics Partnership Exploring the High-Energy Universe Design Optimized for Key Science Objectives 4 x 4 Array of Towers Anticoincidence Shield Understand particle acceleration in AGN, Pulsars, & SNRs Resolve the γ-ray sky: unidentified sources & diffuse emission Determine the high-energy behavior of GRBs & Transients Proven technologies and 7 years of design, development and demonstration efforts Precision Si-strip Tracker (TKR) Hodoscopic CsI Calorimeter (CAL) Segmented Anticoincidence Detector (ACD) Advantages of modular design NASA, DoE, DoD, INFN/ASI, Japan, CEA, IN2P3, Sweden Gamma Ray Tracker Module Calorimeter Module Grid Challenges of Science in Space Launch Limited Resources Space Environment Resolving the γ-ray sky

27 Tracker Grid DAQ Electronics GLAST Large Area Telescope (LAT) ACD Calorimeter Thermal Blanket Array of 16 identical Tower Modules, each with a tracker (Si strips SSD) 10,000 SSD 83m 2 area ~1M channels, ~ 5M wire bonds A calorimeter (CsI with PIN diode readout) and DAQ module. Surrounded by finely segmented ACD (plastic scintillator with PMT readout).

28 Tower Structure (walls, fasteners) Engineering: SLAC, Hytec Procurement: SLAC I SCIPP (R. Johnson, W. Atwood, W. Rowe, A. Webster, N. Spencer, S. Kachiguine, W. Kroeger, M. Hirayama, M. Sugizaki, B. Baughman, HFWS) SSD Procurement, Testing SSD Ladder Japan, Italy, SLAC I Assembly Italy I GLAST Silicon Tracker Tower Assembly and Test SLAC (2) Italy (16) 10,368 Tray Assembly and Test Italy I Electronics Design, Fabrication & Test UCSC, SLAC I Cable Plant UCSC I Most Production and Assembly Steps done in Industry = I Testing: Academic & Research Institutions 648 Composite Panel & Converters Engineering: SLAC, Hytec, and Italy Procurement: Italy I

29 Typical High Tech University Jobs 2 trays and 2 observers 4 trays, 10 eyes & 10 hands 2 delicate hands All done and all smiles. 17 trays!

30 Astrophysics: Imaging, Tracking Application of Silicon Detectors: No Limits We build instruments to explore the structure of our world from Quarks (<10-20 m) to the entire Universe (>10 28 m). Medicine: Imaging X-talography: Imaging Nuclear Physics X-Spectroscopy Silicon Detectors are used for experimentation at every scale. Gravitation Electro-magnetic Weak Strong Particle Physics: Tracking The largest SSD systems are in Astro- and Particle Physics. We trying to play catch-up in Life Sciences.

31 TKR Interconnects: Industry Job ~ 1,000,000 TKR Channels ~ 6,000,000 encapsulated Wire Bonds

32 GLAST Front-End Electronics ASIC Binary Readout: Low-power (~200uW/channel) Peaking time 1.3 ms Low noise (Noise occupancy <10-5 ) Threshold set in every ASIC Separate Masks for Trigger and Readout in every Channel Trigger = OR of one Si plane (1536 channels) Pulse Height: Time over-threshold on the OR of every Si plane Distinguish single tracks from two tracks in one strip Electron Events Photon Events

33 Prototyping of the GLAST SSD The SSD design has been finalized and procurement is underway 11,500 SSD inlude 10% Spares Qualify Prototypes from HPK (experience with ~5% of GLAST needs) 0.1*specs +340 Additional Prototypes: Micron (UK), STM (Italy), CSEM (Switzerland)

34 Radiobiology

35 Some Basic Questions in Radiobiology: It s the DNA, stupid! Are there different classes of damage depending on the Linear Energy Transfer (LET) and number of ionizations/dna molecule? LET Low High # of Ionizations Damage Repairable? Irreparable? Very High >12 By-stander effect: Damage is being transmitted to distant cells Effect of OH - radicals in the damage process Recombination & Saturation? Improve dosimetry of proton beam for cancer therapy Collaboration (NASA-CalSpace) Loma Linda U. & UCSC (SCIPP & CfO) (A. Seiden, R. Johnson, W. Kroeger, P. Spradlin, B. Keeney, HFWS)

36 Radiation Damage DNA Ionization event (formation of water radicals) Primary particle track Light damage- reparable delta rays e - OH Water radicals attack the DNA Clustered damage- irreparable The mean diffusion distance of OH radicals before they react is only 2-3 nm

37 Project Goals Establishment of a nanodosimetric gas model to simulate ionizations in DNA and associated water Plasmid-based DNA model to measure DNA damage Develop models to correlate nanodosimetry with DNA damage

38 Principle of Nanodosimetry (Statistical Approach) 1nm solid 1 1 atm X 1000 X atm (~1 torr) DNA Propane gas Low pressure propane gas

39 Schematic of Nanodosimeter particle low pressure gas δ electron ion E 2 (strong) vacuum ion counter E 1 differential pumping

40 Setup and Silicon Modules Localization of Protons 2 Silicon Strip Detector (SSD) Modules ND Vessel SSD DAQ VME CRATE Ion counter PC W/ DAQ PCI Card

41 ND Ion Cluster Spectra millivolts Event with 6 ions microseconds A primary particle event is followed by an ion trail registered by the ion counter (electron multiplier) For low-let irradiation, most events are empty

42 ND Ion Cluster Spectra Ion Cluster Spectra 100 Ave. Clustersize as a function of LET P (22Mev) He (4.5MeV) C (70MeV) C (20MeV) de/dx [MeV/(g/cm 2 )] Ion cluster spectra depend on particle type and energy as well as position of the primary particle track The average cluster size increases with increasing LET

43 Proton Energy Measurement TOT vs. Proton Energy Measurement vs. Expectation 100 TOT Saturation TOT & Resolution measured TOT expected 10 LLUMC Synchrotron P Beam GLAST SLAC Test Beam Proton Energy [MeV]

44 Connection Nanodosimetry - Radiobiology Radiation Plasmid Sample Nanodosimeter Incubation with Base Excision Enzymes mobility 0 minutes 15 minutes 30 minutes 60 minutes 120 minutes ssb dsb intact Relative frequency %90 %88 %86 %16 %14 %12 %10 %8 %6 %4 %2 %0 Gel Electrophoresis Ionization Cluster Spectra protons 4 MeV α 5 MeV Cluster size Frequency of lesions of different complexities

45 Radiobiological Model Plasmid (phaze) Irradiation of thin film of plasmid DNA in aqueous solution Three structural forms: superhelical (no damage) open circle (single strand break) linear (double strand break) Separation by agarose gel electrophoresis Fluorescent staining and dedicated imaging system

46 What is needed? Global (Nanodosimetry): Well in Hand? Ionization Cluster Spectra Radiation Plasmid Sample Nanodosimeter Incubation with Base Excision Enzymes mobility 0 minutes 15 minutes 30 minutes 60 minutes 120 minutes ssb dsb intact Relative frequency %90 %88 %86 %16 %14 %12 %10 %8 %6 %4 %2 %0 Gel Electrophoresis protons 4 MeV α 5 MeV Cluster size Frequency of lesions of different complexities Local: Needs Improvement No Radiometry Measurement Correlated with Damage on individual DNA Molecule Correlation needed! Tag individual Interaction, Investigate Damage in detail on struck molecules

47 Particle Tracking Silicon Microscope (PTSM) Protons produce damage AND identify damaged organism Worms in Liquid Phase (directly on SSD) Transfer to Automated Microscope when Occupancy ~ 10% Double-sided SSD: x-y coordinate, Energy, Cluster characteristics. Assay with Automated Microscope using stored x-y coordinates

48 SCIPP Gametogenesis in the adult hermaphrodite of C. elegans oocyte eggs in uterus spermatheca gonad vulva

49 Chromosome structures in the gonad of the adult hermaphrodite

50 SCIPP 0-8h: II (early embryogenesis) + III (diakinesis oocyte) 8-24h: III + IV + V + VI (diplotene to pachytene nuclei)

51 Medicine

52 Application: Compton Camera in Medicine Compton Camera: Silicon detector measures the first scatter Calorimeter measures the energy and direction

53 Strip Detectors in Medicine: Mammography Large objects, proximity focussing Need large detectors! Scan collimated X-ray Source across Si strips X-ray source scan direction Gammex RMI phantom at 0.7 mgy MGD precollimator object silicon strip detector aft-collimator Excized breast tissue 5 cm x 7 cm x 4 cm at 0.3 mgy MGD

54 Strip Detectors in Medicine: Mammography Stationary Telescope of Flat Synchrotron beam and Collimator and edge-on Si Detector Scan Sample/Patient. Edge-on Si strips Have high efficiency No Ghost problem = Pixels

55 Acknowledgements LLUMC Vladimir Bashkirov George Coutrakon Pete Koss WIS Amos Breskin Rachel Chechik Sergei Shchemelinin Guy Garty Itzik Orion Bernd Grosswendt - PTB UCSD - Radiobiology John Ward Jamie Milligan Joe Aguilera UCSC - SCIPP Abe Seiden Hartmut Sadrozinsky Brian Keeney Wilko Kroeger Patrick Spradlin The nanodosimetry project has been funded by the National Medical Technology Testbed (NMTB) and the US Army under the U.S. Department of the Army Medical Research Acquisition Activity, Cooperative Agreement # DAMD The views and conclusions contained in this presentation are those of the presenter and do not necessarily

56 SCIPP A Silicon Telescope For Nanodosimetry A collaboration between Loma Linda University Medical Center, the Weizmann Institute of Science, UC San Diego, and the Santa Cruz Institute for Particle Physics, UC Santa Cruz

57 Collaborators Loma Linda University Medical Center Reinhard Shulte Vladimir Bashkirov Weizmann Institute of Science Amos Breskin Rachel Chechik Sergei Shchemelinin George Coutrakon Peter Koss Guy Garty Itzhak Orion University of California, San Diego John F. Ward Joe Aguilera Jamie Milligan Santa Cruz Institute for Particle Physics (University Of California, Santa Cruz) Abe Seiden Hartmut Sadrozinski Robert P Johnson Wilko Kroeger Patrick Spradlin Brian Keeney

58 SCIPP Radiation Damage To DNA Ionization event (formation of water radicals) Primary particle track Light damage- reparable delta rays e - OH Water radicals attack the DNA Clustered damage- irreparable The mean diffusion distance of OH radicals before they react is only 2-3 nm

59 SCIPP Bethe-Bloch in ND Linear Energy Transfer LET: f ( ) [MeV/ g ] dx de = βγ cm2 E = X, X = ρ l [ g ] dx de cm2 Radiation damage in DNA occurs within 2-3nm Energy loss de/dx (MeV cm 2 g 1 ) Silicon ~1/β 1.5 ρ l( propane) = DNA ρ l( DNA) propane ρ l( propane@1mbar) = STP ρ l( propane@ STP) 1mbar l( propane@1mbar) = l( DNA) 1nm( DNA) = 1mm( propane@1mbar) measure p MIP p/m = βγ e ± Rad Electron momentum (MeV/c) Muon momentum (MeV/c) µ ± Without radiative losses

60 SCIPP 1nm solid 1 µ 1 atm. X 1000 X atm. DNA Propane gas Low pressure propane gas

61 SCIPP 4 Silicon Detectors give position and LET, allow trigger on any combination of planes Eweak electron Incoming Proton X-Y NOT TO SCALE Estrong Ion Aperture Counter Low Pressure Gas Vacuum Ion Y-X

62 Setup and Silicon Modules Localization of Protons 2 Silicon Strip Detector (SSD) Modules SMD Readout VME CRATE Ion Counter PC W/ DAQ PCI Card

63 SCIPP Time-Over-Threshold (TOT): Digitization of Position and Energy with large Dynamic Range TOT Measurement vs Charge in MIP's Effect of Threshold and Voltage TOT SLAC TOT LLUMC Input Charge [fc] TOT charge LET!

64 SCIPP Charge Sharing in SMD s

65 SCIPP TOT Spectra For Low-Energy Protons- An absolute calibration of SMD TOT Spectra for low-energy Protons 250MeV 40MeV 24MeV 17MeV TOT [us]

66 Results Proton energy [MeV] Mean TOT [us] RMS TOT [us] Charge Deposition 400um Si [fc] TOT expected by Bethe-Bloch [us] 13,

67 SCIPP TOT vs. Proton Energy Measurement vs. Expectation 100 TOT Saturation TOT and & Resolution measured Measured TOT TOT expected expected through Bethe-Bloch 10 LLUMC Synchrotron P Beam GLAST SLAC Test Beam Proton Energy [MeV]

68 Proton Energy Measurement σ E = E/ TOT* σ TOT = 1/( TOT/ E)* σ TOT TOT Measured y = * x^( ) R= ToT measured dtot/de = -965*0.79*E =-763*E σ Ε /Ε 10 1 Resolution of TOT System LET Energy E(MeV) σ ΤΟΤ /ΤΟΤ TOT Saturation Proton Energy [MeV] 0.01

69 SCIPP Conclusion 1. Silicon Detectors allow flexible triggering on primary particles. 2. Silicon Detectors yield fantastic spatial resolution We can Measure LET to 10-20% in each of 4 planes µm Given LET, we know Energy to 20-25% in each plane through Bethe-Bloch up to 250 MeV Silicon detectors give Nanodosimetry position and energy, making it possible to simulate ionization of DNA in a gas.