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LTP diagnostics

LTP diagnostics. Alberto Lobo ICE-CSIC & IEEC. Why is diagnostics analysis needed in the LTP?. LISA ’s top level sensitivity requirement is:. LISA :. This is so very demanding a previous LPF mission is planned, with a relaxed sensitivity requirement:. LPF :.

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LTP diagnostics

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  1. LTP diagnostics Alberto Lobo ICE-CSIC & IEEC Barcelona, LISA #7, 20 June 2008

  2. Why is diagnostics analysis needed in the LTP? LISA’s top level sensitivity requirement is: LISA: This is so very demanding a previous LPF mission is planned, with a relaxed sensitivity requirement: LPF: Even ifLTP works to top perfection, a fundamental queston remains: How do we make it to LISA’s sensitivity? Barcelona, LISA #7, 20 June 2008

  3. Refer to poster by Conchillo & Gesa, no. 33 DDS: Data Management& Diagnostics Subsystem • Diagnostics items: • Purpose: • Noise split up • Sensors for: • Temperature • Magnetic fields • Charged particles • Calibration: • Heaters • Induction coils • DMU: • Purpose: • LTP computer • Hardware: • Power Distribution Unit (PDU) • Data Acquisition Unit (DAU) • Data Processing Unit (DPU) • Software: • Boot SW • Application SW: • Diagnostics items • Phase-meter • Interfaces Barcelona, LISA #7, 20 June 2008

  4. Diagnostics items use • The methodology: • Split up total noise readout into parts –e.g., thermal, magnetic,... • Identify origin of excess noise of each kind • Orient future research in appropriate direction for improvement 1. Sensitive diagnostics hardware needs to be designed and built 2.a) Suitable places for monitoring must be identified. b) Algorithms for information extraction need to be set up. 3. Creative research activity thereafter... Barcelona, LISA #7, 20 June 2008

  5. Approach: 1) Apply controlled perturbation a to the system 2) Measure “feed-through” coefficient between force and perturbation: 3) Measure actuala with suitable sensors 4) Estimate contribution of a by linear interpolation: 5) Substract out from total detected noise: 6) Iterate process for all identified perturbations Noise reduction philosophy Problem: to assess the contribution of a given perturbation to the total noise force. Barcelona, LISA #7, 20 June 2008

  6. Location NTCs Comments Req. No Optical Bench 4 Near base corners 3.1 Optical Windows 4 2 per OW 3.2 Inertial Sensors 8 2 on each of the outer x-faces of the IS EH 3.3 LCA mounting struts 6 1 per strut, near centre 3.4 Total 22 --- --- Thermal and sensor requirements Global LTP stability requirement: 10-4 K/ÖHz , 1 mHz < f < 30 mHz Sensor sensitivity requirement: 10-5 K/ÖHz , 1 mHz < f < 30 mHz Barcelona, LISA #7, 20 June 2008

  7. DMU test campaign Transfer function Thermal damper Barcelona, LISA #7, 20 June 2008

  8. DMU test campaign DMU EQM Barcelona, LISA #7, 20 June 2008

  9. DMU test campaign Open thermal damper, wiring and DMU Insulating anechoic chamber for the test Barcelona, LISA #7, 20 June 2008

  10. Digital processing Analog processing PSD3(f) PSDdiff(f) PSDint(f) PSD1(f) + + + y (t) PSDy(f) Integrator N x(t) S/H A/D M 2 A Z-1 + + - m(t) n(t) SN(f) nA/D(t) SNA/D(f) 1/2 FEE Readout electronics PC data acquisition program FEE Analog PCB FEE A/D PCB DMU test campaign Barcelona, LISA #7, 20 June 2008

  11. DMU test campaign Test general schematics Barcelona, LISA #7, 20 June 2008

  12. DMU test campaign Example run Barcelona, LISA #7, 20 June 2008

  13. DMU test campaign Barcelona, LISA #7, 20 June 2008

  14. DMU test campaign Barcelona, LISA #7, 20 June 2008

  15. Thermal sensing summary • Fully compliant with requirements • Thermal gradients slightly distort performance at low frequency • Magnetic properties of NTCs not an issue • Research ongoing for improvements for LISA, encouraging • first results Refer to poster presentation by Pep Sanjuan, no. 27 and yesterday presentation Barcelona, LISA #7, 20 June 2008

  16. Heaters Heaters will be used to measure thermal feedthroughs Barcelona, LISA #7, 20 June 2008

  17. Heaters Barcelona, LISA #7, 20 June 2008

  18. Heaters Measurements: Temperatures T5, T6 in IS1, T11, T12 in IS2 Laser Metrology x1 for IS1, x2= x1+ D for IS2 Thermal signals: temperature closest to activated heater Data Analysis: fit data to ARMA(2,1): • Should be OK in MBW –even beyond!–, and for each OW • Can easily be improved, if necessary, at lower frequencies Barcelona, LISA #7, 20 June 2008

  19. Heaters Refer to poster presentation by Miquel Nofrarias, no. 38 Barcelona, LISA #7, 20 June 2008

  20. Magnetic disturbances in the LTP • Main problem is magnetic noise. This is due to various causes: • Random fluctuations of magnetic field and its gradient • DC values of magnetic field and its gradient • Remnant magnetic moment of TM and its fluctuations • Residual high frequency magnetic fields Test masses are a AuPt alloy 70% Au + 30% Pt of low susceptibility a = 46 mm m = 1,96 kg and low remnant magnetic moment: Barcelona, LISA #7, 20 June 2008

  21. Quantification of magnetic effects If a magnetic field B acts on a small volume d3x with remnant magnetisation M, and susceptibility c, the force on this small volume is: Total force requires integration over TM volume, or: Most salient feature is non-linearity of force dependenceonB. Barcelona, LISA #7, 20 June 2008

  22. Magnitude Value DC magnetic field 10 mT DC magnetic field gradient 5 mT/m Magnetic field fluctuation rms PSD 650 nT/ÖHz Magnetic field gradient rms PSD 250 (nT/m) /ÖHz Magnetic susceptibility 10-5 Remnant magnetic moment 10-8 Am2 Summary of magnetic requirements Barcelona, LISA #7, 20 June 2008

  23. Magnetic sensor requirements Req 2: A minimum 4 magnetometers. Req 2-1: Resolution of 10 nT/sqrt(Hz) within MBW. Req 2-2: Two magnetometers located along x-axis, each as close as possible to the centre of one of the TM, not farther than 120 mm. Req 2-3: The other two may be offset from the x-axis by an amount not larger than 120 mm (TBC), their x coordinate should fall between the IS's at distances TBC. Req 2-4: Operation of magnetometers compatible with full science performance. Req 2-5: Final exact choice of magnetometer locations depends on final configuration of magnetic sources. Limited adjustment of magnetometer positions to within +/- 10 cm along x, y and z must be allowed until system CDR. Barcelona, LISA #7, 20 June 2008

  24. Magnetometer layout • Magnetometers type: • 4 Flux-gate, 3-axis • magnetometers • Model is TFM100G2 from • Billingsley Magnetics. Areas for magnetometer accommodation Barcelona, LISA #7, 20 June 2008

  25. Magnetometers’ accommodation Barcelona, LISA #7, 20 June 2008

  26. Magnetic field map Barcelona, LISA #7, 20 June 2008

  27. Magnetic field reconstruction • Exact reconstruction not possible with 4 magnetometers and • around 50 dipole sources (+solar panel) • Tentative approaches attempted so far: • Linear interpolation • Weighted interpolation –various schemes • Statistical simulation (“equivalent sources”) • Best possible: Multipole field structure estimation: • Only feasible up to quadrupole approximation, though, • given only four magnetometers in LCA. Barcelona, LISA #7, 20 June 2008

  28. Multipole reconstruction theory In vacuum, A multipole expansion of B follows that corresponding to y(x): The coefficients alm(r) depend on the magnetisation M(x). In an obvious notation, structure is: Barcelona, LISA #7, 20 June 2008

  29. Somewhat legthy calculations lead to: with Multipole reconstruction theory • Evaluation of multipole terms is based on some assumptions: • Magnetisation is due to magnetic dipoles only • Such dipoles are outside the LCA. Barcelona, LISA #7, 20 June 2008

  30. Fit criterion is to minimise squared error: Multipole reconstruction theory Idea is now to fit measured field values to a limited multipole expansion model. Arithmetic sets such limit to quadrupole: Barcelona, LISA #7, 20 June 2008

  31. Multipole reconstruction theory Arithmetics of reconstruction algorithm: Data channels: 12 Mlm dipole: 3 Mlm quadrupole: 5 Mlm octupole: 7 these 3 are uniformfield components 3+5 = 8 < 12 => some redundancy, OK 3+5+7 = 15, 3 unknowns too many! • Summing up: • Full multipole structure up to quadrupole level. • This is poor, only first order polynomial approximation • Errors large --easily 100%, and rather unpredictable • Order of magnitude should be OK Barcelona, LISA #7, 20 June 2008

  32. Multipole reconstruction theory • Ways to improve magnetic diagnostics accuracy: • Fluxgates are: • Only 4 • Far from TMs • Large size –long sensor heads, ~2 cm We have recently started preliminary activites at IEEC to assess feasibility of using AMR’s as an alternative to fluxgates. This kind of research is intended for LISA. Barcelona, LISA #7, 20 June 2008

  33. Magnetometers tests m-metal enclosure Billingsley TFM Barcelona, LISA #7, 20 June 2008

  34. Magnetometers tests LTP req. Billingsley TFM Barcelona, LISA #7, 20 June 2008

  35. Magnetometers comparative Barcelona, LISA #7, 20 June 2008

  36. SQUID test of AMR device Barcelona, LISA #7, 20 June 2008

  37. Magnetic diagnostics summary • Fluxgate magnetometers are extremely sensitive • Sensor core is large => space resolution limits • Sensor core is permalloy => distance to TM constraints • Box is large and somewhat heavy => few sampling positions • AMRs indicate good sensitivity • They are very tiny • Weakly magnetic –due to small mass • More thorough investigation needed –underway at IEEC Refer to poster presentation by Nacho Mateos, no. 33 Barcelona, LISA #7, 20 June 2008

  38. measure c (w ~ 1 mHz) Control coils Philosophy: to apply controlled periodic magnetic fields: Force comes then a two frequencies: Coils must be long (2400 turns), to maintain reduced heat dissipation (~few mW). Barcelona, LISA #7, 20 June 2008

  39. Control coils • Purpose: • To measure c in flight • To measure M in flight • To drive magnetic noise Coils must comply with suitable reqs. of power and stability. Workings with DMU have been successfully tested and reported. Barcelona, LISA #7, 20 June 2008

  40. Coil Magnetometer Coil Magnetometer General LTP layout Barcelona, LISA #7, 20 June 2008

  41. Radiation Monitor • Ionising particles will hit the LTP, causing spurious signals in the IS. • These are mostly protons (~90%), but there are also He ions (~8%) • and heavier nuclei (~2%). • Charging rates vary depending on whether • Galactic Cosmic Rays (GCR), or • Solar Energetic Particles (SEP) • hit the detector, as they present different energy spectra. • This has been shown by extensive simulation work at ICL. • Therefore a Radiation Monitor should provide the ability to distinguish • GCR from SEP events. • This means RM needs to determine energies of detected particles. Barcelona, LISA #7, 20 June 2008

  42. Radiation Monitor ICL simulations, based on GEANT-4. (Peter Wass and Henrique Araujo) Barcelona, LISA #7, 20 June 2008

  43. Radiation Monitor • It is a particle counter with some • specific capabilities: • It counts particle hits • Retrieves spectral information • (coincident counts) • Can (statistically) tell GCR • from SEP events • Electronics is space qualified Barcelona, LISA #7, 20 June 2008

  44. RM accommoation in S/C Sun Earth Barcelona, LISA #7, 20 June 2008

  45. In place for test at PSI, Nov-2005 Barcelona, LISA #7, 20 June 2008

  46. In place for test at PSI, Nov-2005 Barcelona, LISA #7, 20 June 2008

  47. Radiation Monitor data Radiation Monitor data are formatted in a histogram-like form. A histogram is generated and sent (to OBC) every 614.4 sec. Barcelona, LISA #7, 20 June 2008

  48. Summary • Thermal diagnostics: • Sensors fully in place • Heaters: in place, and integrating in EMP • Improved sensitivity towards LISA in progress • Magnetic diagnostics: • Sensors fully in place, sub-optimum expected performance • Research in progress towards LISA • Coils fully in place, working on EMP • Radiation Monitor: • EQM built, green light to FM, PSI tests coming up • More on RM in Tim’s talk Barcelona, LISA #7, 20 June 2008

  49. End of Presentation Barcelona, LISA #7, 20 June 2008

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