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SPIN 2004 Oct. 14, 2004 W. Kim, S.S. Stepanyan, S. Woo, M. Rasulbaev, S. Jin

Polarization Measurements of the Target with water and DPPH. SPIN 2004 Oct. 14, 2004 W. Kim, S.S. Stepanyan, S. Woo, M. Rasulbaev, S. Jin (Kyungpook National University) S. Korea. Optical Pumping Mechanism. Spin exchange with optically pumped alkali metal rubidium vapor.

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SPIN 2004 Oct. 14, 2004 W. Kim, S.S. Stepanyan, S. Woo, M. Rasulbaev, S. Jin

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  1. Polarization Measurements of the Target with water and DPPH SPIN 2004 Oct. 14, 2004 W. Kim, S.S. Stepanyan, S. Woo, M. Rasulbaev, S. Jin (Kyungpook National University) S. Korea

  2. Optical Pumping Mechanism Spin exchange with optically pumped alkali metal rubidium vapor.

  3. Diode Laser optics Oven (160 oC) cell pickup coil Coils providing uniform magnetic field RF drive coils Instrument Control Optical Pumping Procedure

  4. H0 Mz a M RF Coil y Æ Mxy x Nuclear Magnetic Resonance Resonance condition: If an RF field of frequency equal to Larmor frequency is applied orthogonal to H0 holding field , the particles can undergo reversal of their magnetic dipole moment orientation.

  5. Adiabatic Fast Passage • AFP sweep is produced sweeping main magnetic field through the resonance up and down the spin rotates an angle approaching 180° as the process is adiabatic. T1– spin-lattice relaxation time; H1 – magnetic component of RF field; H0 – Holding magnetic field amplitude; – gyromagnetic ratio;

  6. NMR Setup Schematic

  7. NMR Setup for 3He Target at KNU Helmholtz coil system NMR Electronics

  8. Optics Setup

  9. Optics

  10. NMR signal creation program

  11. Laser control program

  12. NMR measurement program

  13. Test of the NMR Setup Voltage induced in the pick-up coils [mV] NMR setup as a Receiver Holding Magnetic Field [G] Loop ~ NMR setup: 3 metersPhase: 40.00 degrees External RF radiation generator turned off

  14. Q-curve • Q-curve of pick-up coil circuit fitted with Lorentzian. • RF signal amplitude adjustments

  15. Calibration Constant for Polarization Measurements (1) The signal induced in the pick-up coils by the AFP sweep and detected by the lock-in amplifier is proportional to the macroscopic magnetization M of the sample; S: amplitude of the lock-in amplifier signal k: prop. Constant, taking a count gains, losses in the cables, …μ: magnetic moment of the sample.n: density of the spins .P: polarization of the sample The ratio of the Helium NMR signal height SHe to the water NMR signal height Sw

  16. Polarization of the He target proportional to magnetization. : amplitude of the water signal : amplitude of the Helium signal, : magnetic moments of protons in water and 3He nucleus. Calibration Constant for Polarization Measurements (2)

  17. Polarization Calculation The value of the water sample polarization is calculated from Boltzman statistics: Tw : water temp [K]B : Resonance Holding fieldν (=91kHz) : RF field frequency 1 Amagat (amg) = amplitude of the water signal extracted from the fit of the average NMR data.

  18. Experimental g-factor for DPPH : g=2.039±0.023 very close to electron Used DPPH (5gr, 1cm3 powder) as material for calibration 10 turns of Pickup coils around DPPH Holding Field for 91kHz is less than 0.5G during AFP sweep DPPH (Solid 2.2-Diphenil-1-Picrylhydrazyl) for Calibration of Polarization.

  19. DPPHSignal Y Chanel Dispersion X Chanel Absorption

  20. Water Signal

  21. Summary • NMR system constructed and calibrated for polarization measurements of the polarized 3He Target with AFP method. • Signal-to-noise ratio improved by making coils for NMR setup for polarization measurements. • Measurements performed with DPPH and water

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