Prototype Sensor Status and Measurements u Sensor Response Measurements u Mechanical Response u Noise Expectations u DAQ Status

Sensitivity Measurement u Use antiquated HP 10Hz – 500MHz network analyzer to measure sensor response u Drive top (S1) or bottom (S2) RF drive electrode u Use stripline splitter to combine sense electrode signals (T) u Use directional couplers to normalize network analyzer output (R) »Cable length adjusted to give flat phase response  Measure position using microscope with graticule (20  m)

Sensor Response for Single RF Drive u T/R Amplitude (Yellow) and Phase (Blue) Cantilever Centered (+2  m)Cantilever near Top (-118  m) RF Drive on Top Electrode RF Drive on Bottom Electrode

Sensor Response for Single RF Drive u Plot top and bottom sensor response vs position

Predicted Sensor Response u Use difference between top and bottom response to predict sensor response u Data well fit by quadratic

Sensor Response – T&B RF Drive u Configuration changed to split RF signal and drive both top and bottom sensors »This is the way the sensors actually operate u Center position readily identifiable »Amplitude changes sign when crossing center position »At minimum amplitude (A), dA/df = 0, d  /df maximum

Measured T&B Drive Sensor Response u Plot minimum amplitude vs position »Small frequency dependence – may be artifact of choosing minimum amplitude

Sensor Response with “T” Splitter u Alternative to using splitters is to simply connect together T&B drive, sense signals »Keep all path differences inside sensor enclosure u Impedance can be matched at operating frequency with appropriate L’s and C’s u Amplitude, Phase diagram more complicated »I-Q amplitudes may be more easily understood

Sensor Mechanical Response u Mechanical response well characterized by SHO »Well defined transfer function needed for feedback control

Mechanical and Electronic Noise u Mechanical noise for pendulum from Saulson, PRD 42, 2437 (1990) u Electronic noise determined by first RF amplifier (3 dB Noise Figure) u Corrected noise account for pendulum transfer function »60 pm integrated mechanical noise ( Hz) »37 pm integrated electronic noise ( Hz) for 23 dBm RF drive

DAQ Status u Input Signal Processing (I, Q, Seismometers) »Sensor Electronics (generates I, Q signals) »Frequency Devices Programmable Gain Amplifier (32 channels) »Frequency Devices Programmable Filters (24 channels) u Output Signal Processing (Frequency, Deflectors, Movers) »Precision Analog Systems Amplifier (16 channels) –(8) 0-40V outputs to drive Sensor Deflectors –(8) 0-10V outputs to drive Trek HV amplifiers »Trek High Voltage Amplifiers (8 channels) –0-1000V outputs to drive Movers »RF Source Module (8 channels) –Specifications written, cost estimate from Controls in preparation u Conversion and Control »Pentek A/D, D/A Converters (24 channels) »Pentek DSP »VMIC Digital I/O board (RF Source coarse frequency control) u Interface »(3) Patch panels provide necessary wiring »Custom cables required to interconnect VME modules, patch panels

DAQ Status in Pictures

Plans for Missing Pieces Near term focus is to correlate two vertical sensors u (2) Rhode and Schwartz RF Generators on order to provide RF sources u Have already purchased enough RF components for two sensors »Mini-circuits/Pulsar RF amplifiers, splitters, IQ demodulators, filters, etc. u Need low-noise DC amplifier for I/Q signals (4 channels) »Will build locally