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Geophysical Service Inc./Texas Instruments

Laser Magnetometry Using DBR Laser Pumped Helium Isotopes: Beyond “Juno at Jupiter” (LEOS April 24, 2008) Robert E. Slocum, PhD Chief Technical Officer Polatomic, Inc. 1810 Glenville Drive Richardson, TX 75080 (972) 690-0099. Geophysical Service Inc./Texas Instruments

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Geophysical Service Inc./Texas Instruments

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  1. Laser Magnetometry Using DBR Laser Pumped Helium Isotopes:Beyond “Juno at Jupiter” (LEOS April 24, 2008)Robert E. Slocum, PhDChief Technical OfficerPolatomic, Inc.1810 Glenville DriveRichardson, TX 75080(972) 690-0099

  2. Geophysical Service Inc./Texas Instruments Circled are Cecil H. Green (L) and Robert E. Slocum (R) Sputnik October 1957

  3. Vector Helium 4 Magnetometer (VHM) sensor concept. Mariner 4 launch for Mars 11/28/64

  4. Vector Mode OperationVariable Density Optical Filter Triaxial Helmholtz Coil System BS Circular Polarizer  Laser IR Detector Exciter • Metastable helium subjected to circular polarized radiation and rotating magnetic sweep field BS. • Optical pumping efficiency and absorption depends on angle between field and optical axis. • Signal  cos2 , minimum signal and maximum absorption at  = /2.

  5. Vector ImplementationBias Nulling Field Mode Triaxial Helmholtz Coil System IF Feedback Field BS BF Circular Polarizer  Sensor Amplifier Phase Demod Laser B0 V  IF IR Detector Exciter BS IS Sweep Field Sweep Osc. • Signal  cos2 . • External ambient field B0 causes phase shift of signal. • Feedback steady field BF to null ambient field and cause maximum absorption to occur at =/2. • Feedback currents IF are a measure of the ambient field components.

  6. NOBLE PRIZE RESEARCH CONTRIBUTING TO TECHNOLOGY OF LASER MAGNETIC FIELD SENSORS 2000ZHORES I. ALFEROV, and HERBERT KROEMER for developing semiconductor heterostructures used in high-speed- and opto-electronics and JACK ST. CLAIR KILBY for his part in the invention of the integrated circuit. 1997CLAUDE COHEN-TANNOUDJI for development of methods to cool and trap atoms with laser light. 1989NORMAN F. RAMSEY for the invention of the separated oscillatory fields method and its use in the hydrogen maser and other atomic clocks. HANS G. DEHMELT and WOLFGANG PAUL for the development of the ion trap technique. 1981NICOLAAS BLOEMBERGEN and ARTHUR L. SCHAWLOW for their contribution to the development of laser spectroscopy. 1966ALFRED KASTLER for the discovery and development of optical methods for studying hertzian resonances in atoms. 1964CHARLES H. TOWNES, NICOLAY GENNADIYEVICH BASOV and ALEKSANDR MIKHAILOVICH PROKHOROV for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle. 1956WILLIAM SHOCKLEY, JOHN BARDEEN and WALTER HOUSER BRATTAIN for their researches on semiconductors and their discovery of the transistor effect. 1955POLYKARP KUSCH for his precision determination of the magnetic moment of the electron. 1952FELIX BLOCH and EDWARD MILLS PURCELL for their development of new methods for nuclear magnetic precision measurements and discoveries in connection therewith. 1944ISIDOR ISAAC RABI for his resonance method for recording the magnetic properties of atomic nuclei. 1943OTTO STERN for his contribution to the development of the molecular ray method and his discovery of the magnetic moment of the proton. 1933ERWIN SCHRÖDINGER and PAUL ADRIEN MAURICE DIRAC for the discovery of new productive forms of atomic theory. 1932WERNER HEISENBERG for the creation of quantum mechanics, the application of which has, inter alia, led to the discovery of the allotropic forms of hydrogen. 1922NIELS BOHR for his services in the investigation of the structure of atoms and of the radiation emanating from them. 1918MAX KARL ERNST LUDWIG PLANCK in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta. 1902HENDRIK ANTOON LORENTZ and PIETER ZEEMAN in recognition of the extraordinary service they rendered by their researches into the influence of magnetism upon radiation phenomena.

  7. Fig. 1 Energy level diagram for helium 4.

  8. He4 Cell Sensing Element:Variable Density Optical Filter – Magnetically Controlled He4 Cell m=+1 m=+1m= 0m=-1 E = h0 23S1 m= 0 Energy E = h0 HF Discharge m=-1 11S0 HF Exciter Magnetic Field B0 B0 • Glass cell contains He4 at low pressure (~1.5 Torr). • HF discharge produces metastable 23S1 ground state. • External ambient field B0 splits energy into three Zeeman levels m=+1,0,-1. • Separation energy E = h0 where 0 = (e / 2) B0 and e / 2 = 28.0249540 Hz/nT • Metastables in 23S1 level are atomic magnets.

  9. Optical Pumping 23P0 He4 Cell 23P0 D0 (1082.91 nm) D0 Laser m=+1m= 0m=-1 23S1 m=+1 HF Discharge E = h0 23S1 m= 0 HF Exciter 11S0 E = h0 m=-1 • Pumping produces non-equilibrium distribution of atoms among different energy levels. • m=+1,0,-1 sublevels are equally populated in thermal equilibrium. • m=-1 has high absorption probability for circular polarized 1083 nm laser radiation. • 23P0 atoms decay to m sublevels at equal rates. • Laser pumping produces magnetic moment M opposite field as atoms shift to m=0,+1.

  10. Scalar Mode OperationMagnetically-Driven Spin Precession (MSP) Helmholtz Coil System BRF Circular Polarizer Laser IR Detector Exciter • Metastable helium subjected to circular polarized radiation and RF magnetic field BRF . • Absorption increases when RF magnetic field is at resonance (Larmor frequency) 0 . • RF resonant radiation causes transitions between magnetic sublevels (E = h0 ). • Separation energy E = h0 where 0 = (e / 2) B0 and e / 2 = 28.0249540 Hz/nT. • B0 = 1.42 x 106 Hz / 28.0249540 Hz/nT = 50,669 nT.

  11. Scalar Mode ImplementationMagnetically-Driven Spin Precession (MSP) Helmholtz Coil System BRF Circular Polarizer BRF B0 0 Sensor Amplifier Phase Demod RF Oscillator Laser IR Detector Exciter Sweep Oscillator • Apply periodic sweep to RF oscillator. • Causes periodic modulation of detector output. • Phase synchronous demodulation determines 0 .

  12. OSP BLOCH EQUATIONS The OSP effect can be described using the modified Bloch equations for description of the behavior of the bulk magnetization M in an optically pumped medium as it experiences magnetic resonance. The time dependent magnetization M0(t)/ is given byM0(t) = A + Bcos t, where the OSP magnetic resonance drive frequency is  = 2 (is the actual Larmor frequency for the helium sample). The optically detected light beam intensity is given by Is(t) = KM0(t)M(t), where K is a proportionality constant and M(t) is the magnetization along the optical axis. The Bloch equations can be solved for the case where the beam has 100% modulation (A = 0) to obtain the following expression for Is(t): Is(t) =1/4KB2sin2 / {1 + ( - 0)22} + 1/4 KB2sin2  {cos 2t/ [1 + ( - 0)22] + ( - 0)sin 2t / [1 + ( - 0)22]}.

  13. Scalar Mode OperationOptically-Driven Spin Precession (OSP) 0 Circular Polarizer Laser IR Detector Exciter • Metastable helium subjected to pulsed circular polarized radiation. • Optical pumping efficiency increases at Larmor frequency 0 . • 0 = (e / 2) B0 and e / 2 = 28.0249540 Hz/nT. • B0 = 1.42 x 106 Hz / 28.0249540 Hz/nT = 50,669 nT.

  14. Scalar Mode ImplementationOptically-Driven Spin Precession (OSP) 0 Circular Polarizer 0 B0 Sensor Amplifier Invert Out Phase Demod RF Oscillator Laser IR Detector Exciter Sweep Oscillator 0 • Apply periodic sweep to RF oscillator. • Causes periodic modulation of detector output. • Phase synchronous demodulation determines 0 .

  15. Comparison of OSP and MSP magnetic resonance signals for identical laser pump source and helium cells. OSP RESONANCE MSP RESONANCE

  16. An oblique view of the Juno spacecraft shows the three solar panels, one of which carries the magnetometer (yellow extension on the upper solar panel in this image). The main body of the spacecraft is underneath the high gain antenna, which is used for communications to Earth. The three solar panels are built in four-hinged sections that allow the spacecraft to fit within the rocket for launch. The Juno spacecraft in front of Jupiter. Juno is one of the largest planetary spacecraft to ever be launched.

  17. Omni-directional laser-pumped sensor and lamp-pumped sensor.

  18. Self-Calibrating Vector Helium Magnetometer Photodiode B He-4 cell Photodiode A Optical Isolator PM Fiber He-4 cell Laser Intensity Modulator λ/2 λ/4 Collimating Lens Tri-Axial Coils Polarizing Beamsplitter Cubes

  19. ELECTRONICS UNIT Technical Objectives for Self-Calibrating Vector Helium Magnetometer SENSOR UNIT • Vector field measurement • Self-calibrated by scalar measurement • Calibrated range of ±(1,000 nT to 65,000 nT) • Omni-directional sensitivity • Fiber-coupled laser • Bias Field Nulling (BFN) technique for vector measurements • Optical Spin Precession (OSP) for scalar measurements • Reduced sensor volume and mass • Calibrated vector accuracy of 1 nT • Sensitivity of 5 pT/√Hz

  20. MVLM Calibration Process • Calibration Requirements • Nine coefficients required to calibrate vector magnetometer. • Three offsets in absence of magnetic field. • Three scale factors (gains) for normalization of axes. • Three non-orthogonality angles which build up orthogonal system in sensor. • Year 3/NCE Algorithm Implementation Completed • Vector mode measurements made using BFN technique (goal = 0.1% accuracy). • Scalar mode measurements made using OSP and MSP technique (goal = 0.001% accuracy). • Multiplex vector and scalar measurements for different sensor orientations. • Acquire data and calculated calibration coefficients. • Developed calibration algorithm evolved from compensation algorithm used for Navy airborne systems. • NASA/ESA Standard for Calibration • Use of MSP or OSP provides omni-directional pre-flight scalar field values used for vector calibration using single MVLM cell. This method can be validated in future calibration experiments at the GSFC coil facility.

  21. 15 August, 2005 Learning Data Set

  22. POLATOMIC 2000 SINGLE AXIS GRADIOMETER ON 25 cm SPACING MAD MCM Noise characteristics the POLATOMIC 2000 based on 45 minute data collection period.

  23. MPA and/or UAV LCS AUV Barrier The Continuous Challenge: Understand and Manage Our Own Platform Signatures While Exploiting The Enemy’s Underwater Magnetic and Electric Fields

  24. AN/ASQ-233 MAD P-3C III Retrofit CurrentAN/ASQ-233 SystemMAD On-line/Off-line Off-line Off-Line WRA’s 16 2 Space (cu. Ft.) 4.7 1.2 Weight (lbs.) 143 28 Power (Watts) 450 111 MAD Maneuver Programmer SG-887 / ASW-31 Computer Indicator CGA Vector Sensor Output Coils(3) AMP/Power Supply Control ASA-65 AN/ASQ-81 Sensor AN/ASQ-81 Amplifier AN/ASQ-81 Control ASQ-81(V) RO-32 Recorder Control Amplifier AN/ASA-64 Processor ASA-71 Current P-3C III MAD System Sensor Processor/Control/ Display AN/ASQ-233 MAD

  25. TRANSITION PLATFORMS P-3C MAD Upgrade P-8A SH-60 Seahawk MAD Upgrade Fire Scout VTUAV Insitu M-ScanTM The worlds most sensitive airborne magnetometer in flight testing in 2008. “CAN POLATOMIC SOLVE A MAGNETICS PROBLEM ON YOUR PROGRAM?”

  26. Spectral Densities

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