View
32
Download
0
Category
Tags:
Preview:
DESCRIPTION
Past, present and future of Gravitational Wave detection Science. J. Alberto Lobo, Bellaterra, 13-O ct o be r -2004. Presentation summary. Current GW detection research status: Acoustic detectors Interferometers LISA LPF and the LTP The Diagnostics and DMU subsystems - PowerPoint PPT Presentation
Citation preview
Past, present and future of Gravitational Wavedetection ScienceJ. Alberto Lobo, Bellaterra, 13-October-2004
Presentation summaryCurrent GW detection research status:Acoustic detectorsInterferometersLISALPF and the LTPThe Diagnostics and DMU subsystemsFuture prospects
Earth based GW detectors
Bar conceptIdea of an acoustic detector (bar) is to link masses with a spring:so thatand GW signal gets selectively amplified around frequency W.Strongdirectionality
Real bar detectors Two well separated aluminum bars (~1000 km) Resonance at ~1 kHz Piezoelectric non-resonant transducers Impulse sensitivity:
h~10-16
Coincidence analysis Tens of sightings claimed in one year Claims questioned and eventually disproved Hawking and Gibbons: energy innovation theory Giffard: bar quantum limitNew generation cryogenic and ultra-cryogenic bars
EXPLORER detector at CERN (ROG)
Resonant transducerh ~ 5x10-19
Resonant motion sensorBeat spectrum:
Bar detector sensitivity
MiniGrail, Leiden
Interferometric detector working principle
Interferometric detector designFabry-Prot arms:Photodiode: dark fringe: Photon flux waste Shot noise importantLight recycling technique: Power recycling Signal recyclingDelay lines
Details of VIRGOCascina site, near Pisa
Details of VIRGO
Summary status of LIGONov. 1999: Official inaugurationFeb. 2002: Engineering run E7, 6 monthsSep. 2002: Science run S1, 17 days, + TAMA + GEO-600Feb. 2003: Science run S2, 59 days,Nov. 2003: Science run S3, 70 days, + TAMA + GEO-600
End of 2004: Science run S4: ~4 weeksSpring 2005: Commissioning, ~6 monthsAutumn 2005: Science run S5, ~6 monthsAfter: Full observatory operation
LIGO Science run S3, and GEO-600
there are many GW sources at low frequenciesEarth-based detectors are seismic noise limitedthe solution is to go out to space
LISA
Brief chronology:
LISA conceptTest masses5 million km, 30 mHzTransponder scheme
LISA sensitivity
Comparison with Earth detectors
LISAs assured sources
Cumulative Weekly S/N Ratios during Last Year Before MBH-MBH Coalescence
LISA orbit
Orbit dynamics
The three spacecraftThermal shieldDownlink antennasFEEPBaffleSolar panels SupportstructuresScience moduleStar tracker
The science module
LISA mission summary
LISA PathFinder (formerly SMART-2)LPFIt will carry on board the LTP.However it will be in a smaller scale, both in size and sensitivity.Essentially, LTP will check:
drag free technology picometre interferometry other important subsystems and software
LPF
LPF Funding Agencies and countries
LTP concept1. One LISA arm is squeezed to 30 centimetres:2. Relax sensitivity by one order of magnitude, also in band:
LTP functional architecture
LPF orbit
LTP functional architecture
Drag-free subsystem
Drag-free working conceptCourtesy of S. Vitale
Drag-free working conceptCourtesy of S. Vitale
Drag-free working conceptCourtesy of S. Vitale
Drag-free working conceptCourtesy of S. Vitale
Drag-free working conceptCourtesy of S. Vitale
Drag-free working conceptCourtesy of S. Vitale
Drag-free working conceptCourtesy of S. Vitale
Drag-free working conceptCourtesy of S. Vitale
Drag-free working conceptCourtesy of S. Vitale
Capacitive position sensing principleBias: few volts at 100 kHzNanometre precision comfortably attained
Rotational and translational control example
Inertial sensor structure
LTP functional architecture
LTP optical metrologyPower = 1 mWl = 1.064 mmSignal:
LTP interferometerReadout: quadrant InGaAs photodiodes
The LTP EM optical bench
The LTP EM OB: after-shake tests: phase
LTP functional architecture
The LTP structureASD, courtesy of S. Vitale
The LTP structureASD, courtesy of S. Vitale
The LTP structureASD, courtesy of S. Vitale
The LTP structureASD, courtesy of S. Vitale
The LTP structureASD, courtesy of S. Vitale
The LTP structureASD, courtesy of S. Vitale
The science spacecraftThe science spacecraft carries the the LTP and DRS, the micro-propulsion systems and the drag free control system. Total mass about 470kgInertial sensor core assemblies mounted in a dedicated compartment within the central cylinder.DRS Colloid thrusters mounted on opposing outer panels. Payload electronics and spacecraft units accommodated as far away as possible from the sensors to minimise gravitational, thermal and magnetic disturbances. FEEP and cold-gas micro-propulsion assemblies arranged to provide full control in all axes.Courtesy of G. Racca
LTP functional architecture
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:
Data Processing Unit (DPU) Power Distribution Unit (PDU) Data Acquisition Unit (DAU)
Software:
Process phase-meter readout Charge management control UV light control Caging mechanism drive (TBC) DFACS split (?)
Noise analysis concept
Noise apportioning Direct forces on test mass: Thermal gradients Magnetic forces Fake interferometer noise Coupling to S/C: Test mass position fluctuations Drag free response delay Charged particle showersDiagnostics items
Noise reduction philosophyProblem: to assess the contribution of a given perturbation to the noise force fint.
ExampleCourtesy of S. Vitale
Various diagnostics items Temperature and temperature gradients:
Sensors: thermometers at suitable locations Control: heaters at suitable locations
Magnetic fields and magnetic field gradients:
Sensors: magnetometers at suitable locations Control: induction coils at suitable locations
Charged particle showers (protons):
Sensors: radiation monitor (Mona Lisa) Control: non-existentSpecifications follow from mission top level requirements
Diagnostics science requirementsTBRM
DDS current development statusThermal:
NTC and RTD devices identified and procured (EM) FEE designed and built (EM) First round of tests and data analysis complete New tests underwayMagnetic:
Some preliminary studies and surveys New team has recently assumed responsibilityRadiation monitor:
Full conceptual design ready Front-end Electronics Designed Rest of components selected from ESA/NASA qualified parts Some other parts to be definedDMU:
In situ design and manufacture (price) Advanced state of development, redundancy requested Software writing in progress
Conclusion and future prospects
End of presentation
IGEC
Garching delay line prototype
Delta launcher
LPF operation orbit and injection
LPF operation orbit and injection
FEEP (Field Emission Electric Propulsion)LISA needs six sets of four thrusters per S/C for full drag free control
The entire payload
Various launcher alternativesRockotDneprAriane 5
The LTP optical bench
Thermal diagnostics: current status Sensor choice: NTC & RTD to be tested
Thermal diagnostics: current status16 bit dataNTC1RTD1RTD2RTD2NTC3NTC2RTD2Test Philosophy
Thermal diagnostics: clean room at NTE
Thermal diagnostics: foaming process
Thermal diagnostics: sensor inserts
Thermal diagnostics: first NTC results
Magnetometer top level requirements from LTP magnetic requirements (TBC).Sample rate: 0.33 sample/second (x 3 components)Bits/sample: 16Range: variable ( 10 T, 30 T 100 T)Resolution (FS/216) variable (0.305 nT, 0.91 nT, 3.05 nT)Noise (for SNR=10 dB in 10 T range) 40 pt / sqrt Hz @ 0.15HzMass, power, drift.Survey of suitable magnetometer technologies. Candidate: Fluxgate Magnetometer.Magnetic diagnostics
Magnetic Field10 TMagnetic Field Gradient5 TMagnetic Field PSD650 nTMagnetic Field Gradient PSD25 nT
TechnologyFGMAMRMGMRMHEMMeasurementVectorialVectorialVectorialVectorialRange1 pT 1 T100 pT- 1 T100 pT- 1 T1uT- 100 TPrecision(noise)5-10 pT/Hz @ 1 Hz3-10 nT/Hz @ 1 Hz20 pT/Hz @ 100 Hz10 nT/Hz @ 1HzDrift0.2 nT/yr30-50 ppm/C(temp)600 ppm/C(temp)600 ppm/C(temp)600 ppm/CPower Consumption
Magnetic diagnosticsHelmholtz coil configurations analysed:Preliminary magnetometer survey: flux-gate, Hall effect,
Radiation monitor18 x 18 mm2 10 x 10 mm2 10 mmTelescopic Configuration reduces the Angular acceptance on particles and gives a better spectral resolution.
Radiation MonitorData Control & Analysis
DMU Block Diagram
DMU mechanical design
DMU mechanical design
Recommended