Transcript eLISA_oct2
Charge Management Charging Effects Charging Processes Charge Control Technology LISAPF eLISA Summary and way forward for eLISA T J Sumner First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Charging Effects Time dependent forces* Fl Q (t )v B QE Hall Fl Qv B Metallic Enclosure (Blaser) For interplanetary fields shielding from electrode housing and vacuum housing – limited by access holes η ~ 0.01 Interplanetary fields unlikely to be of concern, but be careful to maintain conducting enclosure integrity No shielding against test-mass motion relative to housing – uncancelled interplanetary residual plus internally generated static fields First eLISA Consortium Meeting - APC, Paris 22nd October 2012 *Assumes VT = 0 Charging Effects Time dependent forces* Q t C Q t Ci Vi 2 2C k C i 1 k 2 n Q t 4A A d 2 2 3 2C d d 2 Q 2A k 2 3 C d 2 Common-mode voltage effects disappear to first order in force Differential-mode voltages used for charge measurement 2 C Cr Q C Q r k 2 V Vcm 2 k k C C k First eLISA Consortium Meeting - APC, Paris 22nd October 2012 *Assumes VT = 0 Charging Effects Time dependent forces Q 2 2A k 2 3 C d k 7 10 % Q 2 10 charge k 30pC 100mV First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Charging Effects Acceleration noise an 2 2 Q 4A QQn 4A 2 4A 2 1 d d d n 2 3 3 2 3 2mC d C d mC d 2 a n 2 C r C r Qn Q V Vn k k mC mC 2 2 Q C C r Cr Q V Vcm 2 2 k k mC mC k 2 an QvBn QnvB 2 2 First eLISA Consortium Meeting - APC, Paris 22nd October 2012 2 2 k n2 2 Charging Processes Uncaging – significant fractions of a volt potentials left on separating metallic surfaces – either sign Cosmic-Rays & Solar Energetic Particles GEANT4 – particle tracking GeV to 100eV – p + He Araújo et al. Astropart.Phys. 22, 451 (2005). Galactic Cosmic Rays First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Charging Processes primary solar particle activity GCR flux F, /s/cm2 F, % N0 (x106) CPU, days T, s N0/NQ 4.29 92.0 121.1 150 200 2189 0.315 6.8 14.4 12 321 1002 0.0591 1.3 14.1 12 1683 1073 4.66 100 149.6 174 − 419 1.89 91.9 53.3 70 200 1889 0.142 6.9 9.3 11 462 849 0.0236 1.1 8.0 10 2402 928 2.06 100 70.6 91 − 359 protons He-4 min He-3 Total protons He-4 Charge Spectrogram timeline max He-3 Total Solar minimum primary solar particle activity TM 0 TM 1 R, e/s sM, e/s SR,e/s/√Hz R, e/s sM, e/s SR,e/s/√Hz 79.5 1.6 30.0 82.3 1.6 30.4 14.5 0.6 14.9 15.3 0.6 15.5 2.15 0.1 5.6 2.07 0.1 5.7 96.2 1.7 34.0 99.7 1.7 34.6 35.6 1.2 23.8 39.4 1.3 25.4 7.1 0.4 12.4 7.0 0.4 12.8 0.90 0.06 3.9 0.89 0.06 4.0 Total 43.6 First eLISA Consortium Meeting - APC, Paris 22nd October 2012 1.3 27.1 47.3 1.4 28.7 R~100 +e/s SR=34.6 +e/s/Hz1/2 protons He-4 He-3 Includes estimate for additional low-energy processes min Total protons He-4 He-3 max Charging Processes FLUKA cr protons +37 /s at solar minimum cf +41 /s First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Charging Processes See also Mulligan et al. JGR, Evidence for relevant non-Gaussian events First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Charging Processes Solar Energetic Particles First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Charge Control Design – trade-off within gravitational reference sensor design Initialisation – e.g. after uncaging to deal with unknown charge residual on test-mass Charge measurement, timed exposure to UV (with bias voltage boost) Preparation – iterative adjustment to prepare test-mass for science data taking Charge measurement, timed differential exposure to UV Science data – slow continuous closed loop feedback to: Reduce coherent artefacts in science data due to cyclic force build-up Suppress low-frequency 1/fn (n≥1) acceleration noise Charge measurement, timed differential exposure to UV Radiation monitor assistance for pre-emptive strike Recovery – rapid response to occasional large excursions Charge measurement, timed exposure to UV (with bias voltage boost) Caging mechanism assistance? [Data processing – removal of artefacts from science data] Instrument history Radiation monitor data Other solar activity data Science data First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Technology (eLISA and LISAPF) Hardware UV source Optical harness Sensor interface coupling Actuation/sensing electronics – [Front-end electronics] Radiation Monitor Electrode/Housing surfaces Test-mass surfaces On-board software Charge measurement Commanding Closed-loop feedback Data Processing Identification/removal of artefacts Quality flags Modelling/Simulation tools Laboratory test-bed(s) First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Technology (LISAPF) LISAPF solution: First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Technology (LISAPF) LISAPF hardware: ULU (UV Lamp Unit) ISUK FOH First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Technology LISAPF validation status: » » » » » ICL test-bed results - - demonstrated rapid discharge First Trento torsion balance results - - bipolar control, measurement, noise Discharge Modelling/simulation - - agreement with experiment DFACS closed loop operations - - devised viable algorithm Subsequent Trento torsion balance results - - inability to achieve bipolar control – surface properties implicated LISAPF Discharge Working Group – see later » Radiation monitor beam tests - - Wass and Hollington Bias voltage on TM (V) vs time (s) Au Bias voltage on TM (V) 4 2 0 -100 -2 100 300 -4 500 18/06/02 24/06/02 -6 -8 -10 Time (s) First eLISA Consortium Meeting - APC, Paris 22nd October 2012 LISAPF Dicharge Working Group S2-ASD-RP-3230, Discharge Working Group Executive Summary Problem: Discharge efficiency compromised by mismatch between surface properties of primary and secondary surfaces Reflectivity QY Photo-electron energy distribution First eLISA Consortium Meeting - APC, Paris 22nd October 2012 LISAPF Discharge Working Group Recommendations from DWG: ISS FM manufacturing adaptations Apply ‘tube mirror’ to ISUKs JF02 and JF04 Adapt gold coating (specification) for TM spheres First eLISA Consortium Meeting - APC, Paris 22nd October 2012 LISAPF Discharge Working Group Recommendations from DWG: ISS FM manufacturing adaptations Apply ‘tube mirror’ to ISUKs JF02 and JF04 Adapt gold coating (specification) for TM spheres ISH FM AIT adaptations Apply plasma cleaning to surfaces before AIT Handling requirements for defined “no-touch” zones on surfaces Nitrogen storage of surfaces at all possible times Apply bake-out of integrated ISS FM at 125°C Apply UV cleaning of surfaces in the integrated ISS FM (pending qualification success) First eLISA Consortium Meeting - APC, Paris 22nd October 2012 ISUK Modification Render of final design after iteration with CGS First eLISA Consortium Meeting - APC, Paris 22nd October 2012 ISUK Modification Image of the hole in the mirror • ISUK mirrors before coating • Prior to final iteration Image of the hole in the mirror Top View Glue coated by Gold Mirror#2 Top View First eLISA Consortium Meeting - APC, Paris 22nd October 2012 • Coating trials at Selex Galileo optical coatings Technology (eLISA) Tripling a red laser with BBO 212nm LISA Studies: • Hardware » Controlled surface preparation » Improved/more detailed microphysics modelling/understanding » UV Lamps - shorten wavelength, second technology – Laser diodes/LEDs » Radiation Monitor definition • Operations » How to deal with two test-masses in the same spacecraft in a co-ordinated way? Data artefacts, Live time » How to deal with three spacecraft in a co-ordinated way? Data artefacts, moderate SEPS varying spatially/temporally from one spacecraft to another, Live time » Use of radiation monitor within the control loop • Data Analysis » Simulator including effects induced by both charge and charge control operations » Identification of artefacts » Removal of artefacts » Data Quality indicators • AOB » More space weather studies » GEANT4 with new spacecraft » Lessons from LISAPF First eLISA Consortium Meeting - APC, Paris 22nd October 2012 ESA Technology Study AO/1-6482/10/NL/HB - LISA CHARGE MANAGEMENT SYSTEM Facility for longer term First eLISA Consortium Meeting - APC, Paris 22nd October 2012 AO/1-6482/10/NL/HB - LISA CHARGE MANAGEMENT SYSTEM Phase 1 First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Phase 2 Some progress SRIS First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Some progress UVDM First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Tripling a red laser with BBO 212nm UV Light Sources UV LEDS SETI CRYSTAL-IS First eLISA Consortium Meeting - APC, Paris 22nd October 2012 UV Light Sources – A/C synchronisation? Complicated by additional AC First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Summary »Charge control is crucial for eLISA operations »Charge control is crucial to the eLISA noise budget »Charge control impacts on the whole payload/(system?) »LISAPF will probably demonstrate that all aspects of charge control for eLISA are viable but marginal »There is still a long ‘shopping list’ of improvements/ optimisations required for eLISA First eLISA Consortium Meeting - APC, Paris 22nd October 2012 Way Forward Item LISAPF eLISA UV type Hg Mode Next step Comment Desirability LED/Laser EBB/EM Simpler, less aging, wider temp range, flexibility Very High DC AC or DC EM/EBB Increased safety margin High Surface study As supplied End-toend spec. Test Facility Better surface control High Control loop SigmaPWM delta – 2 1 lamp lamps Test facility Lower noise Very high Model ASD ICL Update model Payload independence High GRS LTP LTP+ Review Avoid caging, discharge electrode? Medium First eLISA Consortium Meeting - APC, Paris 22nd October 2012