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Advances in Magnetometer TechnologyU.S. Marines will no longer have to worry about what is hidden behind the next rock – they will knowBy Tom LaPuzzaA six-year collaboration by Space andNaval Warfare Systems Center Pacific (SSCPacific) scientists and engineers, withcolleagues in Sweden and Sicily, has putnew force protection technology into thehands of U.S. Marines, who will be takingit to the battlefield sometime this year.Drs. Adi Bulsara and Visarath In, servingas principal investigators, and severalother SSC Pacific personnel, have beenworking with physicists and engineersfrom the University of Catania in Italy andthe Swedish Defense Research Agency(FOI) in Stockholm, to harness the substantialpotential of nonlinear dynamicsfor military and civilian applications.These applications include battlefieldsensors disguised as rocks that can communicatewith each other and pass vitalinformation to military planners via satellitelinks. Similar sensors can be placedon the seafloor and detect swimmers anddivers passing in the water column a fewmeters away.An add-on to the U.S. Marines’ TacticalRemote Sensor System (TRSS) will allowa reconnaissance patrol to image armedindividuals even through a wall, and canalso be deployed in remote areas as anunattended ground sensor for persistentsurveillance. Other sensors, the sizeof clothing buttons, can also be distributedrandomly around a building to alertsecurity personnel to the presence ofintruders.Technology DevelopmentThe basic idea of using the principles ofnonlinear dynamics in developing a magnetometerwith a simpler readout basedon the idea of spike timing, which underpinsthe neural code, came during a 2003discussion between Dr. Bulsara, his colleaguesin Stockholm, and professor LucaGammaitoni of the University di Perugiain Italy.“We were chatting and jotting somethoughts on a chalkboard, when it hit usthat the physics would allow us to developa magnetometer that could sense minutechanges in a magnetic field caused byThe magnetometer to be placed on the U.S. Marines’ Tactical Remote Sensor System and the “rock”under which it would be hidden to gather information without being noticeable to those passing by.objects made of ferrous metal, leading toa wide range of applications,” Dr. Bulsarasaid.“Of course, the basic fluxgate magnetometerhad been around since WorldWar II; however, the idea of modifying thereadout to mimic the process wherebyneurons are believed to code and processinformation in the nervous system wasdifferent. We realized quite rapidly thatif certain physics constraints were met,then the idea afforded simplicity and elegancewhich are always desirable in newconcepts. We persuaded FOI to do a quickexperiment to test the idea (it worked),and [we] wrote a long article about it inPhysical Review A in 2003,” Dr. Bulsara said.“Over the next six years, we rigorouslyproved the physics and began developingvarious pieces of hardware. It’s a reflectionon the dynamics of the groupthat one of the products of that early discussionand subsequent development,the single core magnetometer, is ready togo into the field within only six years fromthe initial ideas as an additional sensor ofthe TRSS that gives the Marines some remarkablecapabilities, including the abilityto ‘see’ moving ferrous material (e.g.,rifles) through walls.”After Visarath In and Joe Neff arrived atthe lab, research accelerated and theoreticalwork aimed at better understandingthe physics of coupled nonlinear oscillatorsrapidly evolved into the “coupledcoremagnetometer” which involvescoupling an odd number of wound ferromagneticcores cyclically to one anotherin a ring oscillator configuration. A magnetometerbased on the unique physicsof this configuration is far more sensitivethan the single core magnetometer.The coupled-core magnetometer isbeing refined, with a number of practicalissues remaining to be addressed.However, it will likely render the singlecore magnetometer obsolete in a coupleof years. The SSC Pacific group and theirinternational collaborators are exploringother sensors and devices that employthe unique features of the coupled oscillatorconfiguration.TRSSTRSS, developed mostly by other organizations,is a handheld device weighingonly a few pounds, but it carries acoustic,infrared, seismic and magnetic sensors.The SSC Pacific contribution is a magnetometerabout 4 inches by 4 inches(shown on the next page) that will replace26 CHIPS www.chips.navy.mil Dedicated to Sharing Information - Technology - Experience