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G070517-00-0Charging Workshop - MIT - July071 T.J. Sumner – ICL lead and LIST Henrique Araujo, Markus Schulte, Diana Shaul, Christian Trenkle (now Astrium), Simon Waschke, Peter Wass (now Trento) Heritage ( 10 year mission ) Electrostatic Modelling LTP EM Design GEANT Modelling Imperial College – LISA and LISAPF G070517-00-0
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Charging Workshop - MIT - July072 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
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G070517-00-0Charging Workshop - MIT - July073 Lorentz force noise Metallic Enclosure (Blaser)
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G070517-00-0Charging Workshop - MIT - July074 Lorentz force noise See later!
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G070517-00-0Charging Workshop - MIT - July075 Electrostatic forces
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G070517-00-0Charging Workshop - MIT - July076 Electrostatic forces Common-mode voltage effects disappear to first order in force Differential-mode voltages used for charge measurement – see later
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G070517-00-0Charging Workshop - MIT - July077 Summary of Charge Limits Effect Limit (C) Lorentz Noise4x10 -11 (10 -4 Hz) Displacement Noise4x10 -11 Charge Noise ( d) 1.4x10 -11 (10 -4 Hz) Stiffness (assymmetry)3x10 -12 (≡70mV) Stiffness ( V dm ) 10 -8 Stiffness (1V cm )4x10 -13 Potential (noise)10 -2 Potential (noise) (1V cm )3x10 -11 Assumptions!! dd10 m VnVn 10 V/ Hz
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G070517-00-0Charging Workshop - MIT - July078 LISA Geant4 Geometry Model S/C: LISA Solid Model (GSFC/NASA) ~200 placed volumes (85% total mass) LTP IS: CAD (Carlo Gavazzi Space) 46 mm cube test mass, YZ injection
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G070517-00-0Charging Workshop - MIT - July079
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G070517-00-0Charging Workshop - MIT - July0710 Charged Particle Environment Galactic Cosmic Rays Solar Flare Events
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G070517-00-0Charging Workshop - MIT - July0711 Geant4 Physics Processes Electromagnetics E th = 250 eV Photo/Electronuclear Hadronics Intra-nuclear cascades for protons and light ions Decays Hadronic Models Most G4 physics, including latest developments* * Working within GEANT4 development team
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G070517-00-0Charging Workshop - MIT - July0712
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G070517-00-0Charging Workshop - MIT - July0713 Charging Multiplicity Charge Spectrogram LISA solmin Statistical Fluctuations LISA solmin Q= Q i 2 ~2.5 Q 1
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G070517-00-0Charging Workshop - MIT - July0714 Charging Spectrum LISA solmin Charging Spectra I
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G070517-00-0Charging Workshop - MIT - July0715 Spectral Charging Efficiency p stopping in test mass Cascade/String change-over String Model G4QGSP Cascade Model G4BinaryCascade p stopping before TM
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G070517-00-0Charging Workshop - MIT - July0716 primarysolarGCR fluxtimeline particleactivity , /s/cm 2 , % N 0 (x10 6 ) CPU, daysT, sN 0 /N Q protons 4.2992.0121.11502002189 He-4min0.3156.814.4123211002 He-3 0.05911.314.11216831073 Total4.66100149.6174−419 protons 1.8991.953.3702001889 He-4max0.1426.99.311462849 He-3 0.02361.18.0102402928 Total2.0610070.691−359 LISA Results CERN LSF Cluster 2.2x10 8 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
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G070517-00-0Charging Workshop - MIT - July0717 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 !
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G070517-00-0Charging Workshop - MIT - July0718 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
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G070517-00-0Charging Workshop - MIT - July0719 Shaul et al., 2004 Data Analysis and Clean-up
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G070517-00-0Charging Workshop - MIT - July0720 Charging from Solar Events Large solar flares (<1 /yr) can seriously disrupt normal operation More modest flares (~1/yr) can deposit >10 9 charges in ~1 day Small but frequent flares (>5 /yr) will contaminate the science data Recommendation on specification of radiation monitor for LISAPF SEP Event DistributionSEP Event Prediction solar maximum
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G070517-00-0Charging Workshop - MIT - July0721 Charging from Solar Flares I Small SEP Event (GOES - May 20 2001) Event fluence 6x10 5 p/cm 2 Charging rate at peak flux ~160 +e/s Total event charge ~3x10 6 +e Frequency 5-10 /year Event fluence ~10 9 p/cm 2 Charging rate at peak flux ~130 000 +e/s Total event charge ~5x10 9 +e Frequency << 1 /year Large SEP Event (GOES - Sep 29 1989) Need to characterise SEP distribution to lower fluences
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G070517-00-0Charging Workshop - MIT - July0722 CR Variability – INTEGRAL and POLAR No dramatic concern - some indications of isolated CR fluctuations, probably induced by solar events.
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G070517-00-0Charging Workshop - MIT - July0723 Radiation Monitor ICL Detector concept: 2 PIN diodes in tetescopic configuration: PINs have been kindly provided by GLAST collaboration
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G070517-00-0Charging Workshop - MIT - July0724 Radiation Monitor Coincidence spectrum for GCRCoincidence spectrum for SEP
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G070517-00-0Charging Workshop - MIT - July0725 Radiation Monitor PIN Diode PCB Cu shielding Radiation Monitor Geometry GCR + SEP particle fluxes Energy Spectrum 600s Energy Spectrum - entire simulation Angular acceptance
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G070517-00-0Charging Workshop - MIT - July0726 The CMS is a distributed system Lamp assembly UV Lamps and optics Electronics Fibre-optic cables Inertial Sensor Electronics Interface kit Computer Software Spacecraft Electronics Modules Optical Bench Procedures Design Parameters Subsystem TestsSystem Tests CMS functions
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G070517-00-0Charging Workshop - MIT - July0727 Inertial Sensor Design Electrode isolation Capacitance matrix Capacitance gradient Cross-coupling matrix Caging design Charge sensitivity – electrode layout
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G070517-00-0Charging Workshop - MIT - July0728 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.
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G070517-00-0Charging Workshop - MIT - July0729 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
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G070517-00-0Charging Workshop - MIT - July0730 Charge Neutralisation LT i lf T f vc 2 T vc ~ 3x10 10 photons/s Oxford Instruments HPSUV1000 fibre Caburn FFTUV1000 (Special – remade in titanium with epoxy seal)
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G070517-00-0Charging Workshop - MIT - July0731 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 ~ 6x10 3 charges/s —500 V/m/eV gives Q/ t ~ 3x10 4 charges/s Differential Surface Illumination using individual lamp currents to modify electron fluxes —L( ) and L(I) Charge Transport - t
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G070517-00-0Charging Workshop - MIT - July0732 Polar Ouput Charge Transport
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G070517-00-0Charging Workshop - MIT - July0733 Differential Surface Illumination Charge Transport Electrode:Housing:TM 1 : 1.3 : 0.1 1 : 1.1 : 13.1 -3.9x10 3 < <+3.5x10 3 /s Add dc bias to drive harder when required x5
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G070517-00-0Charging Workshop - MIT - July0734 Charge Transport Test Rig UV Lamp
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G070517-00-0Charging Workshop - MIT - July0735 Charge control with lamps Electrode lamp off TM lamp off, electrode lamp on TM Lamp on Rate ~ ±40000e/s Simulator with physics in place for LTP UV Lamp OFF UV Lamp ON
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G070517-00-0Charging Workshop - MIT - July0736 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
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G070517-00-0Charging Workshop - MIT - July0737
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