1 Fast Timing via Cerenkov Radiation‏ Earle Wilson, Advisor: Hans Wenzel Fermilab CMS/ATLAS Fast Timing Simulation Meeting July 17,

2 Overview Conducted simulations using a 6x6mm x 9cm Quartz bar and an incident beam of 7TeV protons:  Observed photons statistics: photon spectrum, prevalence of secondary photons etc.  Obtained arrival time and timing resolution using the quantum efficiency of the Hamamatsu MCP R3809U-65.  Studied effects of varying angle of incident proton beam.  Compared results from Hamamatsu with Photek 240. Started simulations using aerogel:  Observed Photon statistics.  Studied effects of Rayleigh Scattering. 2

3 Quartz Bar Geometry and Set-up -Quartz bar: 6x6 mm x 9cm. -6X6 mm sensitive detectors on each end. -Incident beam of 7TeV protons perpendicular to bar. -No air gap between detectors and quartz bar. -Only Cerenkov radiation. Scintillation, Rayleigh scattering and dispersion were not added. 3

4 Toolbox Geant4: Simulates processes inside radiator, i.e. Quartz bar and Aerogel. Includes  Electro-magnetic physics  Cerenkov radiation  Rayleigh Scattering (only for Aerogel)‏  Absorption  Dispersion  Reflection, refraction etc...  Outputs ROOT file for analysis ROOT: Simulates processes inside detector  Quantum Efficiency  Jitter  Outputs ROOT file for analysis.

5 Quartz Bar Properties 5

6 Comparing Geant4 to calculations Geant 4 Calculatio n 6

7 Photon Spectrum/Statistics Geant 4 (primary photons)‏ Calculation Geant 4 (Secondary photons)‏  Geant4 compares very well with standard calculations.  Secondary photons radiate mostly in the blue/ultra-violet but there are significantly fewer secondary photons than primary photons.  However, for a given event, there could be more secondary photons than primaries.  This could have a major effect on timing and time resolution. Refractive Index: Events Results Taken at the moment of creation. Primary Photons Secondary Photons

8 Quantum Efficiency Hamamatsu MCP R3809U-65 Photek 240  The Hamamatsu has a better overall quantum efficiency, peaking at 40% at ~520nm.  Photek 240 has a lower overall Q.E. but much better sensitivity in the blue/ultraviolet range.

9 Average Number of Photons and Photoelectrons at Each Detector vs. Angle of Incident Beam -Jitter: 30 psec -Gain: 100 -Cerenkov angle: Each data point is the average of 1000 events. Photons Photoelectrons: Hamamatsu MCP R3809U-65 Photoelectrons: Photek 240 Cerenkov Angle

10 Arrival Time and Timing- Resolution vs. Angle Incident Beam -Timing and timing resolution obtained using DCOG Method -Cerenkov Angle: Jitter: 30 psec, Gain: 100 -Each data point is taken over 1000 events. -Best timing resolution of ~2.8 psec at 65 degrees. Photoelectrons: Hamamatsu MCP-PMT R3809U-65 Photoelectrons: Photek 240 Photoelectrons: Hamamatsu MCP-PMT R3809U Cerenkov Angle Arrival time: ~0.24nsec Cerenkov Angle: Timing resol. ~3.2 psec

11 11 Aerogel (SiO 2 )Dimensions: 4cm X 4cm X 1cm Silicon MCP-PMT dimensions: 4cm X 4cm Refractive Index: Incident 7TeV Simulation of Aerogel Radiator

12 12 Refractive Index: Material Properties of Aerogel NOTE THE SCALES Obtained values from a Geant4 example for Rich Detector simulation for LHCb:

13 Without Rayleigh ScatteringWith Rayleigh Scattering Refractive Index: ~10% loss of Photons Simulation of Aerogel Radiator

14 Simulation of the Aerogel Counter Without Rayleigh Scattering Refractive Index: Aerogel (SiO 2 )Dimensions: 4cm X 4cm X 1cm Silicon MCP-PMT dimensions: 4cm X 4cm Plane Mirror: 5cm * 5cm Mirror Tilt: 45 degrees Incident 7TeV We plan to compare simulations with test beam results. 40 mm

15 Create identical set-up of test beam experiment with Aerogel. Compare simulation results with experimental results. Explore ways to optimize experiment. For Quartz Bar Simulation: vary the position of the incident proton beam and observe changes in timing resolution. Vary length and thickness of Quartz Bar and observe changes in timing resolution Upcoming Work