Present status of the 129Xe comagnetometer development for neutron EDM measurement

A ¹²⁹Xe comagnetometer designed for the measurement of neutron electric dipole moment (nEDM) as precisely as 1 × 10^?27e cm is presented. Highly nuclear spin polarized ¹²⁹Xe are introduced into an EDM cell where the ¹²⁹Xe spin precession is detected by means of the two-photon transition. The geometric phase effect (GPE) which generates the false nEDM was quantitatively discussed and the systematic error of nEDM from the GPE was estimated considering the buffer-gas suppression due to Xe atomic collisions. Research and development are in progress to construct the ¹²⁹Xe comagnetometer with a field sensitivity of 0.3 fT. At present, about 70 % nuclear spin polarized ¹²⁹Xe atoms have been obtained in a spin exchange opitial pumping cell, that are in the process of being transferred into the EDM cell via a cold trap.     

Intravascular delivery of hyperpolarized129Xenon forin vivo MRI

The nuclear polarization of¹²⁹Xe and³He can be enhanced by several orders of magnitude by using optical pumping techniques, thus allowing NMR detection of xenon and helium in very low concentrations. The benefits of optically enhanced magnetic resonance (MR) are already exploited in MR imaging of the lungs using optically polarized³He. The high solubility of xenon in blood and lipids suggests a variety ofin vivo MR applications, for instance perfusion measurements or functional MR studies. This article reviews some current work directed towards delivery of optically polarized xenon forin vivo MR applications.     

Towards a new measurement of the neutron electric dipole moment

Precision measurements of particle electric dipole moments (EDMs) provide extremely sensitive means to search for non-standard mechanisms of T (or CP) violation. For the neutron EDM, the upper limit has been reduced by eight orders of magnitude in 50 years thereby excluding several CP violation scenarios. We report here on a new effort aiming at improving the neutron EDM limit by two orders of magnitude, down to a level of 3 × 10⁻²⁸ e·cm. The two central elements of the approach are the use of the higher densities which will be available at the new dedicated spallation UCN source at the Paul Scherrer Institute, and the optimization of the in-vacuum Ramsey resonance technique, with storage chambers at room temperature, to reach new limits of sensitivity.     

Search for electric dipole moment in 129Xe atom using a nuclear spin oscillator

We aim to measure the electric dipole moment (EDM) of a diamagnetic atom ¹²⁹Xe using an optical-detection nuclear spin maser technique. The relation of EDM in a diamagnetic atom to nuclear Schiff moment and fundamental sources generating it is discussed, and the present status for the development of our experimental setup is presented.     

Ultra-sensitive magnetometry based on free precession of nuclear spins

We discuss the design and performance of a very sensitive low-field magnetometer based on the detection of free spin precession of gaseous, nuclear polarized ³He or ¹²⁹Xe samples with a SQUID as magnetic flux detector. The device will be employed to control fluctuating magnetic fields and gradients in a new experiment searching for a permanent electric dipole moment of the neutron. Furthermore, with the detection of the free precession of co-located ³He/¹²⁹Xe nuclear spins it can be used as ultra-sensitive probe for non-magnetic spin interactions, since the magnetic dipole interaction (Zeeman-term) drops out. Characteristic spin precession times T₂ ^* of up to 60 h were measured. The achieved signal-to-noise ratio of more than 5000:1 leads to an expected sensitivity level (Cramer-Rao lower bound) of δB≈1 fT after an integration time of 220 s and of δB≈10^-4 fT after one day. By means of a co-located ³He/¹²⁹Xe magnetometer, noise sources inherent in the magnetometer could be investigated, showing that CRLB is fulfilled, at least down to δB≈10^-2 fT. The reason for such a high sensitivity is that free precessing ³He (¹²⁹Xe) nuclear spins are almost completely decoupled from the environment. Therefore, this type of magnetometer is particularly attractive for precision field measurements where long-term stability is required.     

129Xe and131Xe NMR of xenon on silica surfaces at 77 K

Little is known about¹²⁹Xe NMR spectral features and spin-lattice relaxation behavior, and the dynamics of xenon atoms, for xenon adsorbed on solid surfaces at cryogenic temperatures (≤77 K), where exchange with gas-phase atoms is not a significant complication. We report¹²⁹Xe NMR experiments at 9,4 T that provide such information for xenon adsorbed onto the hydroxylated surface of a number of microporous silica samples at 77 K. A convenient design for these cryogenic experiments is described. Dynamics of surface-adsorbed xenon atoms on the time scale of seconds can be observed by¹²⁹Xe NMR hole-burning experiments; much slower dynamics occurring over hours and days are evidenced from changes with time of the¹²⁹Xe NMR chemical shifts. The peak maxima occur in the region ca. 180–316 ppm, considerably downfield of¹²⁹Xe shifts previously reported on surfaces at higher temperatures, and closer to the shift of xenon bulk solid (316.4±1 ppm). The¹²⁹Xe spin-lattice relaxation timesT ₁ range over five orders of magnitude; possible explanations for both nonexponential relaxation behavior and extremely shortT ₁ values (35 ms) are discussed. Preliminary¹³¹Xe and¹H NMR results are presented, as well as a method for greatly increasing the sensitivity of¹²⁹Xe NMR detection at low temperatures by using closely-spaced trains of rf pulses.     

Development of co-located 129Xe and 131Xe nuclear spin masers with external feedback scheme

We report on the operation of co-located ¹²⁹Xe and ¹³¹Xe nuclear spin masers with an external feedback scheme, and discuss the use of ¹³¹Xe as a comagnetometer in measurements of the ¹²⁹Xe spin precession frequency. By applying a correction based on the observed change in the ¹³¹Xe frequency, the frequency instability due to magnetic field and cell temperature drifts are eliminated by two orders of magnitude. The frequency precision of 6.2 μHz is obtained for a 10⁴ s averaging time, suggesting the possibility of future improvement to ≈ 1 nHz by improving the signal-to-noise ratio of the observation.     

Atomic Electric Dipole Moment Measurement Using Spin Exchange Pumped Masers of 129Xe and 3He

We have measured the T-odd permanent electric dipole moment of 129Xe with spin exchange pumped masers and a 3He comagnetometer. The comagnetometer provides a direct measure of several systematic effects that may limit electric dipole moment sensitivity, and we have directly measured the effects of changes in leakage current that result when the applied electric field is changed. Our result, d(129Xe) = 0.7+/-3.3(stat)+/-0.1(syst)x10(-27)e cm, is a fourfold improvement in sensitivity.     

Hyperpolarised gas filling station for medical imaging using polarised 129Xe and 3He

We report the design, construction, and initial tests of a hyperpolariser to produce polarised ¹²⁹Xe and ³He gas for medical imaging of the lung. The hyperpolariser uses the Spin-Exchange Optical Pumping method to polarise the nuclear spins of the isotopic gas. Batch mode operation was chosen for the design to produce polarised ¹²⁹Xe and polarised ³He. Two-side pumping, electrical heating and a piston to transfer the polarised gas were some of the implemented techniques that are not commonly used in hyperpolariser designs. We have carried out magnetic resonance imaging experiments demonstrating that the ³He and ¹²⁹Xe polarisation reached were sufficient for imaging, in particular for in vivo lung imaging using ¹²⁹Xe. Further improvements to the hyperpolariser have also been discussed.     

Searches for Lorentz violation in 3He/129Xe clock comparison experiments

We discuss the design and performance of a very sensitive low-field magnetometer based on the detection of free spin precession of gaseous, nuclear polarized ³He or ¹²⁹Xe samples with a SQUID as magnetic flux detector. Characteristic spin precession times $T_2^\ast$ of up to 115 h were measured in low magnetic fields (about 1 μT) and in the regime of motional narrowing. With the detection of the free precession of co-located ³He/¹²⁹Xe nuclear spins (clock comparison), the device can be used as ultra-sensitive probe for non-magnetic spin interactions, since the magnetic dipole interaction (Zeeman-term) drops out in the weighted frequency difference, i.e., Δω?=?ω _He ???γ _He /γ _Xe ·ω _Xe . We report on searches for Lorentz violating signatures by monitoring the Larmor frequencies of co-located ³He/¹²⁹Xe spin samples as the laboratory reference frame rotates with respect to distant stars (sidereal modulation).     

Iron-57 Mössbauer spectroscopic study of fluorinated strontium orthoferrite

A nuclear spin maser of a new type, that employs a feedback scheme based on optical nuclear spin detection, has been fabricated. The spin maser is operated at a low static field of 30 mG by using the optical detection method. The frequency stability and precision of the spin maser have been improved by a highly stabilized current source for the static magnetic field. An experimental setup to search for an electric dipole moment (EDM) in ¹²⁹Xe atom is being developed.     

An apparatus for NMR of laser polarized 129Xe on single crystal surfaces

Due to a lack of at least 2 orders of magnitude in the amount of sample nuclei, single crystal surfaces are out of reach for conventional NMR measurements. Our aim is to prove that highly polarized ¹²⁹Xe provides a technique to overcome this restriction. Therefore an apparatus for polarizing ¹²⁹Xe up to 0.7 by spin transfer from optically pumped Rb has been designed as well as an NMR spectrometer in combination with a UHV chamber with sample cleaning, cooling and characterization abilities and a special manifold of glass stopcocks with a liquid nitrogen cooled trap for dosing nitrogen free polarized Xe into the chamber onto the surface. This revised version was published online in August 2006 with corrections to the Cover Date.     

The study of Xe adsorption behavior in meso-size pores of carbon black materials using laser-polarized 129Xe NMR spectroscopy

The meso size pores of carbon black materials with Pt critically affect catalysts which play an important role for fuel cells of electric vehicles. Time-consuming BET methods are usually used to measure the physisorption enthalpy which determines the characteristics of catalysts. The laser polarized method enhances 129Xe polarization by 4 orders of magnitude, overcoming a low sensitivity, making this measurement technique faster than conventional experiments. In this paper, we first demonstrate Laser-Polarized 129Xe NMR Spectroscopy for studying carbon black materials with Pt of fuel cells of electric vehicles in order to determine the physisorption enthalpy. At the same time, T1 experiments using Laser-Polarized 129Xe will be discussed in order to clarify the surface condition and adsorption behavior.     

Performance assessment of a new laser system for efficient spin exchange optical pumping in a spin maser measurement of <Superscript>129</Superscript>Xe EDM

We demonstrate spin-exchange optical pumping of ¹²⁹Xe atoms with our newly made laser system. The new laser system was prepared to provide higher laser power required for the stable operation of spin maser oscillations in the ¹²⁹Xe EDM experiment. We studied the optimum cell temperature and pumping laser power to improve the degree of ¹²⁹Xe spin polarization. The best performance was achieved at the cell temperature of 100 ^°C with the presently available laser power of 1 W. The results show that a more intense laser is required for further improvement of the spin polarization at higher cell temperatures in our experiment.     

Optimization of continuous flow pump cells used for the production of hyperpolarized <Superscript>129</Superscript>Xe: A theoretical study

Laser-polarized xenon can be used to increase the sensitivity of NMR experiments by 4–5 orders of magnitude, enabling numerous applications in physics, chemistry, biology, and medicine. For the production of hyperpolarized (hp) ¹²⁹Xe, continuous flow pump cells are commonly used. Based on a 3D numerical model consisting of eight partial differential equations [1], we describe the optimization of continuous flow cells with respect to several experimental parameters in this contribution. We also compare our simulations with data from literature. PACS 32.80.Bx     

Chemical-Shifts in Magnetic-Resonance of the 3He Nucleus in Liquid Solvents and Comparison with Other Noble Gases

Gas-to-solution solvent shifts of ³He dissolved in 17 pure liquids were measured. Two types of samples were used, under helium pressures of about 2 and 30 atm. No measurable pressure effect on the shift could be detected. The gas-to-solution shifts are dominated by the bulk susceptibility, for which correction was made. The resulting medium-shift range in our solvents is about 0.8 ppm. Hence ³He provides an excellent probe for the detection of minute local magnetic fields at the site of noble-gas atoms. For the first time shifts in liquid solvents for all four NMR-accessible noble-gas nuclei (³He, ²¹Ne, ⁸³Kr, and ¹²⁹Xe) can be compared. The medium shifts of ³He show a roughly linear correlation to medium shifts of ¹²⁹Xe, ⁸³Kr, and ²¹Ne in the same solvents. The corrected relative solvent shifts, that is, the solvent effects divided by σ_d, the diamagnetic shielding of the free atom, and by the number of nearest-neighbor solvent molecules, are approximately equal for all four noble gases.     

Nuclear electric dipole moment of He

A permanent electric dipole moment (EDM) of a physical system requires time-reversal (T) and parity (P) violation. Experimental programs are currently pushing the limits on EDMs in atoms, nuclei, and the neutron to regimes of fundamental theoretical interest. Here we calculate the magnitude of the P-, T-violating EDM of ³He and the expected sensitivity of such a measurement to the underlying P-, T-violating interactions. Assuming that the coupling constants are of comparable magnitude for π-, ρ-, and ω-exchanges, we find that the pion-exchange contribution dominates. Our results suggest that a measurement of the ³He EDM is complementary to the planned neutron and deuteron experiments, and could provide a powerful constraint for the theoretical models of the pion–nucleon P-, T-violating interaction.     

NMR chemical shifts of129Xe dissolved in various oxygen and nitrogen substituted straight chain aliphatic compounds

Xenon-129 NMR spectra have been measured for dilute solutions of¹²⁹Xe dissolved in a series of n-alcohols and primary n-alkyl amines, as well as ethylene glycol and water. The chemical shifts recorded for¹²⁹Xe in the alcohols and amines are found to be linearly related to solvent composition expressed in terms of the individual methyl and methylene groups as well as the nitrogen and oxygen bearing functional groups making up these compounds. This behavior is consistent with a simple model which considers the van der Waals contribution to the chemical shift of¹²⁹Xe to result from pair interactions between a dissolved Xe atom and the individual methyl, methylene, and functional groups from which the solvent molecules are derived. The¹²⁹Xe chemical shifts caused by the ?CH₂?, ?NH₂, and ?OH groups are found to be quite similar in magnitude, each being approximately twice that of a ?CH₃ group.     

Nuclear spin maser and experimental search for 129 Xe atomic EDM

The present status of an active spin maser which is being developed for an experimental search for ¹²⁹Xe atomic electric dipole moment (EDM) is presented. In order to realize the long term stability of maser frequency, systematic effects for the spin maser operation were investigated. The correlations in the maser frequency with the solenoid current, the environmental field and the cell temperature were found. With the solenoid current and environmental field being stabilized and the cell temperature lowered, a frequency precision of 7.9 nHz has been achieved for the maser operation.