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T.J. Sumner – ICL lead and LIST

G070517-00-0. Imperial College – LISA and LISAPF. T.J. Sumner – ICL lead and LIST Henrique Araujo, Markus Schulte, Diana Shaul, Christian Trenkle (now Astrium), Simon Waschke, Peter Wass (now Trento). Electrostatic Modelling. Heritage ( 10 year mission ). LTP EM Design. GEANT Modelling.

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T.J. Sumner – ICL lead and LIST

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  1. G070517-00-0 Imperial College – LISA and LISAPF T.J. Sumner – ICL lead and LIST Henrique Araujo, Markus Schulte, Diana Shaul, Christian Trenkle (now Astrium), Simon Waschke, Peter Wass (now Trento) Electrostatic Modelling Heritage (10 year mission) LTP EM Design GEANT Modelling Charging Workshop - MIT - July07

  2. Charging of isolated proof-masses in satellite experiments Effects of free charge Lorentz force Electrostatic forces from mirror charges Spring Constants Forces from applied voltages Charging Estimates Rates Timelines Charge Management Measurement procedures Discharge procedures Charging Workshop - MIT - July07

  3. Lorentz force noise Metallic Enclosure (Blaser) Charging Workshop - MIT - July07

  4. See later! Lorentz force noise Charging Workshop - MIT - July07

  5. Electrostatic forces Charging Workshop - MIT - July07

  6. Electrostatic forces Common-mode voltage effects disappear to first order in force Differential-mode voltages used for charge measurement – see later Charging Workshop - MIT - July07

  7. Summary of Charge Limits Charging Workshop - MIT - July07

  8. LISA Geant4 Geometry Model • LTP IS: CAD (Carlo Gavazzi Space) • 46 mm cube test mass, YZ injection • S/C: LISA Solid Model (GSFC/NASA) • ~200 placed volumes (85% total mass) Charging Workshop - MIT - July07

  9. Charging Workshop - MIT - July07

  10. Charged Particle Environment Solar Flare Events Galactic Cosmic Rays Charging Workshop - MIT - July07

  11. Hadronic Models Geant4 Physics Processes Most G4 physics, including latest developments* • Electromagnetics • Eth = 250 eV • Photo/Electronuclear • Hadronics • Intra-nuclear cascades • for protons and light ions • Decays Charging Workshop - MIT - July07 * Working within GEANT4 development team

  12. Charging Workshop - MIT - July07

  13. Charge Spectrogram Statistical Fluctuations LISA solmin LISA solmin Charging Multiplicity Q=Qi2~2.5 Q1 Charging Workshop - MIT - July07

  14. Charging Spectrum LISA solmin Charging Spectra I Charging Spectrum Charging Workshop - MIT - July07

  15. String Model G4QGSP p stopping in test mass Cascade/String change-over p stopping before TM Cascade Model G4BinaryCascade Spectral Charging Efficiency Charging Workshop - MIT - July07

  16. LISA Results • CERN LSF Cluster • 2.2x108 Events • several CPU Years • 200 s exposure time Latest LISA result – Astropart Phys. 22, 451-469 (2005) Rate = +50 e/s Noise = 30 e/s/Hz-1/2 Charging Workshop - MIT - July07

  17. Non-Simulated Physics Kinetic Electron Emission • Potential Charging Processes: • Electron-induced kinetic emission • Ion-induced kinetic emission • Atom sputtering (<0.01 at/s) • X-ray transition radiation (<1 +e/s) • X-ray Cherenkov radiation (<1 +e/s) • Cosmogenic activation (<<1 +e/s) • Hadron-induced x-ray emission Kinetic emission of low energy secondary electrons (<50 eV)due to incident electrons (EIEE) and ions (IIEE) can be significant ! Charging Workshop - MIT - July07

  18. GP-B Simulations Flare result is ~2-3 times too high but does not allow for spectral modification of proton flux at GP-B orbit Charging Workshop - MIT - July07

  19. Data Analysis and Clean-up Shaul et al., 2004 Charging Workshop - MIT - July07

  20. Charging from Solar Events SEP Event Distribution SEP Event Prediction solar maximum • Large solar flares (<1 /yr) can seriously disrupt normal operation • More modest flares (~1/yr) can deposit >109 charges in ~1 day • Small but frequent flares (>5 /yr) will contaminate the science data • Recommendation on specification of radiation monitor for LISAPF Charging Workshop - MIT - July07

  21. Charging from Solar Flares I Small SEP Event (GOES - May 20 2001) Large SEP Event (GOES - Sep 29 1989) • Event fluence 6x105 p/cm2 • Charging rate at peak flux ~160 +e/s • Total event charge ~3x106 +e • Frequency 5-10 /year • Event fluence ~109 p/cm2 • Charging rate at peak flux • ~130 000 +e/s • Total event charge ~5x109 +e • Frequency << 1 /year Charging Workshop - MIT - July07 Need to characterise SEP distribution to lower fluences

  22. CR Variability – INTEGRAL and POLAR No dramatic concern - some indications of isolated CR fluctuations, probably induced by solar events. Charging Workshop - MIT - July07

  23. Radiation Monitor ICL Detector concept: 2 PIN diodes in tetescopic configuration: PINs have been kindly provided by GLAST collaboration Charging Workshop - MIT - July07

  24. Radiation Monitor Coincidence spectrum for GCR Coincidence spectrum for SEP Charging Workshop - MIT - July07

  25. PIN Diode PCB Cu shielding Radiation Monitor Angular acceptance GCR + SEP particle fluxes Energy Spectrum 600s Energy Spectrum - entire simulation Radiation Monitor Geometry Charging Workshop - MIT - July07

  26. Fibre-optic cables Lamp assembly UV Lamps and optics Inertial Sensor Electronics Interface kit Electronics Software Computer Optical Bench Spacecraft Electronics Modules Design Parameters The CMS is a distributed system CMS functions Procedures Charging Workshop - MIT - July07 Subsystem Tests System Tests

  27. Inertial Sensor Design • Electrode isolation • Capacitance matrix • Capacitance gradient • Cross-coupling matrix • Caging design • Charge sensitivity – electrode layout Charging Workshop - MIT - July07

  28. Charge Management System Charge Measurement using applied dither force in transverse direction with capacitive sensing of test-mass response. Discharge technique using differential illumination of surfaces with UV illumination, with bias voltage enhancement if needed. Charging Workshop - MIT - July07

  29. Charge Measurement • Dither Technique • Different gaps in each direction give different measurement authority • Need to see dither above residual drag-free position noise • Assume transverse dither with 1nm/Hz position noise Charging Workshop - MIT - July07

  30. Charge Neutralisation LTilfTfvc2Tvc ~ 3x1010 photons/s Oxford Instruments HPSUV1000 fibre Caburn FFTUV1000 (Special – remade in titanium with epoxy seal) Charging Workshop - MIT - July07

  31. Charge Transport - t • Dual Surface Illumination with dc bias voltage to modify ballistic trajectories • 2.1 V/m/eV gives Q/t ~ 15 charges/s • 80 V/m/eV gives Q/t ~ 6x103 charges/s • 500 V/m/eV gives Q/t ~ 3x104 charges/s • Differential Surface Illumination using individual lamp currents to modify electron fluxes • L() and L(I) Charging Workshop - MIT - July07

  32. Charge Transport • Polar Ouput Charging Workshop - MIT - July07

  33. Charge Transport • Differential Surface Illumination Electrode:Housing:TM 1 :1.3:0.1 1 :1.1 :13.1 -3.9x103< <+3.5x103 /s Add dc bias to drive harder when required  x5 Charging Workshop - MIT - July07

  34. Charge Transport Test Rig UV Lamp Charging Workshop - MIT - July07

  35. UV Lamp ON UV Lamp OFF Charge control with lamps Simulator with physics in place for LTP TM lamp off, electrode lamp on Rate ~ ±40000e/s TM Lamp on Electrode lamp off Charging Workshop - MIT - July07

  36. LISAPF Lamps • Derivative of those used on EINSTEIN and ROSAT – 6,000 hr lifetimes • Low pressure electric discharge cf rf discharge used on GPB. • 8 housed in 3.5kg package for LISAPF • 100:1 dynamic range using PWM at kHz frequencies • 3W per lamp Charging Workshop - MIT - July07

  37. Charging Workshop - MIT - July07

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