PRECISE MAGNETOMETERS ON BASE OF PULSED NMR TECHIQUES G.Karpov, A.Medvedko, E.Shubin, Budker Institute of Nuclear Physics SB RAS, Novosibirsk, Russia

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  • PRECISE MAGNETOMETERS ON BASE OF PULSED NMR TECHIQUESG.Karpov, A.Medvedko, E.Shubin,

    Budker Institute of Nuclear Physics SB RAS, Novosibirsk, Russia.Budker INP, NovosibirskRUPAC 2006

  • Main features:Budker INP, NovosibirskRUPAC 2006Precise Magnetometers on base of pulsed NMR techniquesIn 1999-2006 a new generation of precise Magnetometers on base of pulsed NMR techniques has been developed and fabricated at BINP.1) High precision: field measurement error less than 10-5, resolution is of order 10-7 (for homogeneous fields) 2) Wide field range: 0.02513 T 3) Large field range provided with one probe: BMAX/BMIN is up to 304) Acceptable field gradients: grad(B)/B up to 510-4/mm 5) Multichannel measurements6) Small probe dimensions: minimal probe thickness is ~1 mm7) Small probe sensitive volume up to 1 mm38) Capability of measurements at liquid helium temperature9) VME standard

  • PULSED NMR TECHNIQUE USED IN BINP MAGNETOMETERS Spin echo signalFID signalLarmor frequency of nuclear precession , where gyromagnetic ratioFourier-transformationFNMR = L0 /(2), L0 precession frequency in the centre of probe sensitive volumeIf RF pulses frequency FRF is close to precession frequency FL (FRF - FL < 1/T90) free induction decay (FID) signal and spin echo signal with precession frequency are appeared.B magnetic field value

    6

    0

    0

    0

    0

    0

    0.0000000002

    0.0000000031

    0.0000000458

    0.0000005574

    0.0000055595

    0.0000453999

    0.0003035391

    0.0016615573

    0.0074465831

    0.0273237224

    0.0820849986

    0.201896518

    0.4065696597

    0.670320046

    0.904837418

    1

    0.904837418

    0.670320046

    0.4065696597

    0.201896518

    0.0820849986

    0.0273237224

    0.0074465831

    0.0016615573

    0.0003035391

    0.0000453999

    0.0000055595

    0.0000005574

    0.0000000458

    0.0000000031

    0.0000000002

    0

    0

    0

    0

    FNR

    Signal spectrum

    Frequency

    1

    -2000

    -1900

    -180.010

    -170.020

    -160.030

    -150.060.0000000002

    -140.10.0000000031

    -130.130.0000000458

    -120.1850.0000005574

    -110.250.0000055595

    -100.350.0000453999

    -90.50.0003035391

    -80.680.0016615573

    -70.830.0074465831

    -60.940.0273237224

    -50.980.0820849986

    -40.9990.201896518

    -310.4065696597

    -20.9990.670320046

    -10.980.904837418

    00.941

    10.830.904837418

    20.680.670320046

    30.50.4065696597

    40.350.201896518

    50.250.0820849986

    60.1850.0273237224

    70.130.0074465831

    80.10.0016615573

    90.060.0003035391

    100.030.0000453999

    110.020.0000055595

    120.010.0000005574

    1300.0000000458

    1400.0000000031

    150.0000000002

    160

    170

    180

    190

    1

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    0

    F

    2

    3

  • Functional diagram of NMR Magnetometers

  • Digital signal processing

    Obtained in the magnet 3.S of VEPP-4 NMR waveform envelope and weighting function

    Purpose: finding of the module and sign of difference frequency FD = FNR FSYN

    Signal-to-noise ratio in frequency domain:

    where ES signal energy, SN noise spectral density

    Matched filtering: signal array before Fourier transformation is multiplied on matched weighting function.

    2

    0.02060741960.0000258681

    0.02211481450.0000573909

    0.02209093240.0001234098

    0.02163216360.0002572081

    0.02172955150.0005195747

    0.02492048870.0010172778

    0.02910251020.0019304541

    0.03380566940.0035506486

    0.04207987950.0063297154

    0.05004180080.0109367675

    0.05427709570.0183156389

    0.06206299970.0297292164

    0.06516638260.0467706224

    0.06273762890.0713166827

    0.05176833190.1053992246

    0.03851356760.1509774185

    0.06206087340.2096113872

    0.13013010180.2820629517

    0.22097024830.3678794412

    0.32810621670.4650431881

    0.45250722490.5697828247

    0.58408558990.6766338462

    0.70970339430.7788007831

    0.82237869610.8688150563

    0.91472850010.9394130628

    0.97576291330.984496437

    0.99998874991

    0.98776300060.984496437

    0.9405757440.9394130628

    0.86138705050.8688150563

    0.75612808410.7788007831

    0.63317292320.6766338462

    0.50534231670.5697828247

    0.38299503330.4650431881

    0.26986357260.3678794412

    0.17463697680.2820629517

    0.1039754640.2096113872

    0.06870527210.1509774185

    0.06599343350.1053992246

    0.07214563470.0713166827

    0.07392361720.0467706224

    0.07259966630.0297292164

    0.06868798320.0183156389

    0.06013203140.0109367675

    0.05021554850.0063297154

    0.0455003130.0035506486

    0.04265301460.0019304541

    0.03546312840.0010172778

    0.03371185150.0005195747

    0.03034997270.0002572081

    0.02466499640.0001234098

    0.02620590960.0000573909

    0.02620087340.0000258681

    0.02365448640.0000113009

    0.023209570.0000047851

    0.01900847680.0000019638

    "weighting"function

    waveformenvelope

    Time 3 ms

    Normalized signal and weighting function

    s_sem

    -0.090.0550.0541870617

    -0.0460.0050.0237713543

    -0.016-0.0210.0135631942

    -0.003-0.0420.0216321636

    0.005-0.0530.0273492559

    0-0.0520.026714616

    -0.008-0.0460.0239868842

    -0.015-0.0470.0253457927

    -0.024-0.0560.0313003775

    -0.029-0.0520.0305881852

    -0.027-0.0540.0310166121

    -0.023-0.0570.0315774146

    -0.019-0.0570.0308673391

    -0.015-0.060.031773226

    -0.008-0.0570.0295703394

    -0.002-0.0490.0251943485

    0-0.0430.0220909324

    -0.003-0.040.0206074196200.0000258681

    0.002-0.0430.0221148145210.0000573909

    0-0.0430.0220909324220.0001234098

    0.003-0.0420.0216321636230.0002572081

    0.005-0.0420.0217295515240.0005195747

    0.012-0.0470.0249204887250.0010172778

    0.02-0.0530.0291025102260.0019304541

    0.019-0.0630.0338056694270.0035506486

    0.025-0.0780.0420798795280.0063297154

    0.032-0.0920.0500418008290.0109367675

    0.031-0.1010.0542770957300.0183156389

    0.037-0.1150.0620629997310.0297292164

    0.049-0.1170.0651663826320.0467706224

    0.057-0.1080.0627376289330.0713166827

    0.065-0.0770.0517683319340.1053992246

    0.074-0.0120.0385135676350.1509774185

    0.0720.0970.0620608734360.2096113872

    0.0680.2440.1301301018370.2820629517

    0.0310.4290.2209702483380.3678794412

    -0.0290.6380.3281062167390.4650431881

    -0.1170.8730.4525072249400.5697828247

    -0.2321.1130.5840855899410.6766338462

    -0.3771.3290.7097033943420.7788007831

    -0.5371.5080.8223786961430.8688150563

    -0.6981.6380.9147285001440.9394130628

    -0.8451.7010.9757629133450.984496437

    -0.9641.6910.9999887499461

    -1.0511.610.9877630006470.984496437

    -1.091.4710.940575744480.9394130628

    -1.0831.280.8613870505490.8688150563

    -1.0191.0620.7561280841500.7788007831

    -0.9120.8290.6331729232510.6766338462

    -0.7810.5980.5053423167520.5697828247

    -0.6310.3970.3829950333530.4650431881

    -0.4770.220.2698635726540.3678794412

    -0.3320.0730.1746369768550.2820629517

    -0.2-0.0310.103975464560.2096113872

    -0.098-0.0910.0687052721570.1509774185

    -0.025-0.1260.0659934335580.1053992246

    0.02-0.1390.0721456347590.0713166827

    0.044-0.1370.0739236172600.0467706224

    0.053-0.1310.0725996663610.0297292164

    0.05-0.1240.0686879832620.0183156389

    0.04-0.110.0601320314630.0109367675

    0.023-0.0950.0502155485640.0063297154

    0.01-0.0880.045500313650.0035506486

    0.002-0.0830.0426530146660.0019304541

    -0.002-0.0690.0354631284670.0010172778

    -0.009-0.0650.0337118515680.0005195747

    -0.003-0.0590.0303499727690.0002572081

    -0.001-0.0480.0246649964700.0001234098

    0.001-0.0510.0262059096710.0000573909

    0-0.0510.0262008734720.0000258681

    -0.002-0.0460.0236544864730.0000113009

    0.004-0.0450.02320957740.0000047851

    0-0.0370.0190084768750.0000019638

    0.002-0.0410.0210884929

    -0.001-0.0360.0185018681

    -0.005-0.0320.0166392343

    -0.003-0.0290.0149780424

    -0.001-0.0350.0179883292

    -0.007-0.0360.0188411208

    -0.009-0.0320.0170775958

    s_sem

    "weighting"function

    waveformenvelope

    Time 3 ms

    Normalized signal and weighting function

  • Two modes of operation1) Search mode: scanning with Synthesizer frequency in specifying range and finding of coarse value of NMR frequency 2) Measurement mode: precise measurement of NMR frequency; Synthesizer frequency is close to NMR frequency and follows to it

  • During the measurement cycle signal accumulation is performed: summing of N registered NMR signals (digit arrays). It follows to signal-to-noise ratio increasing in times.Simultaneously with signal accumulation digital signal processing is performed. During the cycle M digital processing of the signal accumulated in cycle M-1 is performed. Measurement cycle structureTime duration of the elementary cycle TC = 20100 msNumber of accumulated signals N = 10100

  • Structure of the Magnetometers Control SystemVME crate controller

    Magnetometers microcontroller

    VME busETHERNET

    Magnetometers functional partsOS: LINUX or VxWorksHigh levelLow level

  • NMR probes