High-Field Spin Exchange Optical Pumping of Cesium Salts An - PowerPoint PPT Presentation

Spin Exchange Optical Pumping Experimental Setup Results High-Field Spin Exchange Optical Pumping of Cesium Salts An Experimental Project Ben Andrew Olsen Princeton University Adviser: William Happer November 12, 2007 Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Experimental Setup Results 1 Spin Exchange Optical Pumping Basic Picture SEOP with Cesium Vapor CsH and CsF 2 Experimental Setup Optical Pumping Setup High-Frequency NMR Probe 3 Results Cesium Fluoride Cesium Hydride Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF Basics of SEOP Optically pump alkali metal vapor Polarized alkali atoms in the vapor interact with atoms of another species Increase the net nuclear polarization of the other species (hyperpolarization) Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF Applications of Hyperpolarization Fundamental Physics High energy physics: Spin polarized beams of particles Atomic physics: Spin-dependent interactions, gyroscopes In vivo Imaging Inhale hyperpolarized gas for lung imaging Inject or ingest hyperpolarized material to track intake into tissue Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF Basics of SEOP in Solids Optically pump the alkali metal vapor Polarized alkali atoms diffuse toward cell walls Polarized alkali atoms in the vapor interact (and exchange) with alkali atoms in the solid Increase the net nuclear polarization of alkali atoms in the solid Detect net polarization using pulse NMR Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF A Cartoon of SEOP Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF A Cartoon of SEOP Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF A Cartoon of SEOP Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF SEOP with Cesium Vapor Complications to our simple picture: I = 7 / 2: 8 levels with hyperfine structure Electron spin and orbital angular momenta are coupled Several transitions to pump Questions to answer: Do electron or nuclear polarization currents dominate SEOP? Can we polarize the other nuclei in the salt? Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF D 2 Transitions in Cesium Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF Simulation of SEOP in Cesium Electron spin current J s and nuclear spin current J I to the cell walls for some transitions: Transition J s J I ( b + ) − − ( b − ) + + ( e + ) + − Red indicates the larger magnitude current. At opposite polarization, the magnitudes of J s , J I decrease by a few orders of magnitude. Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF Cesium Hydride Polarization enhancement by SEOP has been seen for Cs in CsH (K. Ishikawa et al., Phys. Rev. Lett. 98(18), 2007) Enhancement by a factor of 4 for allowed transitions We want to measure the dependence of enhancement on photon polarization Cells with such high Cs enhancement are good candidates for H enhancement For H in CsH, T 1 ∼ 1000 s at room temperature For Cs in CsH, T 1 ∼ 300 s at room temperature Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Basic Picture Experimental Setup SEOP with Cesium Vapor Results CsH and CsF Cesium Fluoride There is little published data on CsF relaxation times 19 F and 1 H have similar gyromagnetic ratios The same probe and spectrometer electronics can be used Both 19 F and 1 H are spin - 1 / 2 We expect similar relaxation mechanisms, hence similar T 1 We also expect T 1 for 133 Cs to be the same CsCl crystal structure above 300 K, otherwise NaCl crystal structure Other cesium salts have CsCl crystal structure Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Optical Pumping Setup Experimental Setup High-Frequency NMR Probe Results Optical Pumping Setup Shutter Multi-mode Fiber Fiber Coupler Polarizing Beam Splitter 335 290.1 GHz λ /4 Plate Chopper Wavemeter Single-Mode Fiber NMR 400 02.30 PC 05.10 Lock-In Amplifier 0 5 3 1 5 0 0 0 0 NMR Spectrometer Alkali Cell Photodiode Diode Pump Laser Ti:Sapphire Laser Figure from B. Patton, Ph.D. Thesis, Princeton University, Sep. 2007 Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Optical Pumping Setup Experimental Setup High-Frequency NMR Probe Results High-Frequency NMR Probe Inductive coil for producing tipping pulses and detecting sample polarization Variable capacitors for adjusting resonant response Holds vapor cell steadily in beam path Electrically isolated from probe cap Ideally hydrogen-free Coil made completely of bare copper Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Optical Pumping Setup Experimental Setup High-Frequency NMR Probe Results High-Frequency NMR Probe Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Cesium Fluoride Experimental Setup Cesium Hydride Results T 1 Measurements in CsF Green data points from D. K. Hutchins and S. M. Day, Phys. Rev. , 180(2), Apr 1969 Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Cesium Fluoride Experimental Setup Cesium Hydride Results Cs NMR Enhancement in CsH Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Cesium Fluoride Experimental Setup Cesium Hydride Results 1 H NMR Large background signal Shorter T 1 ( ∼ 100 s) Narrow spectral feature Spectral feature from H in CsH is very broad T 1 is very long, so we can’t average as much Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Cesium Fluoride Experimental Setup Cesium Hydride Results 1 H NMR Subtraction Averaging Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Cesium Fluoride Experimental Setup Cesium Hydride Results 1 H NMR Enhancement Ben Andrew Olsen High-Field SEOP of Cesium Salts

Spin Exchange Optical Pumping Experimental Setup Conclusions Results Conclusions CsF is a poor candidate for SEOP T 1 for 19 F is short CsF is very difficult to deal with Heteronuclear SEOP is possible in CsH Enhancement is small Background subtraction is imperfect Electron and nuclear spin currents are comparable in homonuclear SEOP Dependence of angular momentum currents on photon polarization is not well understood Ben Andrew Olsen High-Field SEOP of Cesium Salts