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MRI of lung airspaces using gases with MR-active nuclei ((3) He, (129) Xe, and (19) F) is an important area of research in pulmonary imaging. The volume-controlled administration of gas mixtures is important for obtaining quantitative information from MR images. State-of-the-art gas administration using plastic bags (PBs) does not allow for a precise determination of both the volume and timing of a (3) He bolus.A novel application unit (AU) was built according to the requirements of the German medical devices law. Integrated spirometers enable the monitoring of the inhaled gas flow. The device is particularly suited for hyperpolarized (HP) gases (e.g., storage and administration with minimal HP losses). The setup was tested in a clinical trial (n = 10 healthy volunteers) according to the German medicinal products law using static and dynamic ventilation HP-(3) He MRI.The required specifications for the AU were successfully realized. Compared to PB-administration, better reproducibility of gas intrapulmonary distribution was observed when using the AU for both static and dynamic ventilation imaging.The new AU meets the special requirements for HP gases, which are storage and administration with minimal losses. Our data suggest that gas AU-administration is superior to manual modes for determining the key parameters of dynamic ventilation measurements.

We have measured the neutron electric form factor ${G}_{\mathrm{en}}$ via ${}^{3}\stackrel{\ensuremath{\rightarrow}}{\mathrm{He}}(\stackrel{\ensuremath{\rightarrow}}{e}{,e}^{\ensuremath{'}}n)\mathrm{pp}$ at ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.67(\mathrm{GeV}/c{)}^{2}$ using the 3-spectrometer facility of the A1 Collaboration at the Mainz Microtron and a dedicated neutron detector. High pressure polarized ${}^{3}\stackrel{\ensuremath{\rightarrow}}{\mathrm{He}}$ gas was used as a target of polarized neutrons. ${G}_{\mathrm{en}}$ is determined from the ratio of the asymmetries ${A}_{\ensuremath{\perp}}{/A}_{\ensuremath{\parallel}}$ measured in quasifree kinematics with the target spin perpendicular and parallel to the momentum transfer. We find ${G}_{\mathrm{en}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.052\ifmmode\pm\else\textpm\fi{}0.011\ifmmode\pm\else\textpm\fi{}0.005$.

It is well known that a finite neutrino mass would provide a backing not only for modern theories of particle physics beyond the standard model, but, in a literal sense, for the whole universe, also. Whereas particle physicists would accept more or less any positive result as a gauge of their theories, the astrophysicists calculate that a mass of the order of 10 eVlc2 (averaged over the three flavors) of the many relic neutrinos from the big bang would mark the turning point from an open to a closed universe. No wonder, therefore, that physicists set out to hunt the neutrino mass by any possible means.

A Comment on the Letter by Takashi Nakajima, Phys. Rev. Lett. 99, 024801 (2007). The authors of the Letter offer a Reply.

The strongly spin-dependent absorption of neutrons in nuclear spin-polarized (3)He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable (3)He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A short survey of their use under experimental conditions, e.g. large solid-angle polarization analysis, is given. In neutron particle physics NSFs are used in precision measurements to test fundamental symmetry concepts.

Eine von Null verschiedene Neutrinomasse konnte nicht nur den immer noch spekulativen Elementarteilchentheorien jenseits des Standardmodells Halt geben, sondern daruber hinaus auch dem gesamten Universum; ersteres im ubertragenen, letzteres im wortlichen Sinne. Wahrend die Teilchenphysik mehr oder weniger jeden Meswert als Fixpunkt ihrer Theorien akzeptieren wurde, sieht die Astrophysik bei einer Masse der vielen, vom Urknall her ubriggebliebenen Neutrinos in der Grosenordnung von 10 eV/c2 den Wendepunkt vom offenen zum geschlossenen Universum. Das hier geschilderte Tritium-Experiment liefert einen Wert von < 7,2 eV/c2.

Assessment of the temporal and spatial dynamics of hyperpolarized Helium-3 (3He) distribution in the lung with ultrafast gradient-echo magnetic-resonance imaging.Coronal images of the lung were acquired using ultrafast gradient-echo pulse sequences with TR/TE = 3.3 ms/1.3 ms (slice thickness, 40 mm) and TR/TE = 2.0 ms/0.7 ms (without slice selection). A series of 80 or 160 projection images was obtained with 210 ms or 130 ms temporal resolution, respectively. Imaging was performed during several respiratory cycles after application of a single bolus of 300 mL hyperpolarized 3He. Measurements were performed in six healthy volunteers (spontaneous breathing).Different phases of in- and expiration could be visualized. During the course of consecutive respiratory cycles the 3He signal decreased due to dilution of 3He in residual alveolar gas and by inspired air, relaxation due to oxygen and the RF pulses, and due to Helium-3 washout. The signal of a single bolus of 3He was detected in the lung for up to four respiratory cycles. Anatomical structures were better visualized on slice selective images than on images without slice selection.Distribution of inspired 3He within the tracheobronchial tree and alveolar space and its washout can be visualized by ultrafast imaging of a single bolus of hyperpolarized 3He gas. This method may allow for regional analysis of lung function with temporal and spatial resolution superior to conventional methods.

Conventional 1H-MRI of the lung is restricted by susceptibility effects and low proton density: Recently, imaging of lung ventilation in MRI has become feasible using hyperpolarised inert gases with a spin of I = 1/2, such as 3He and 129Xe, as inhalative "contrast agents". New technical developments, preclinical and clinical application of this method are described.With optical laser pumping high polarisation rates can be achieved, resulting in a high signal-to-noise ratio (S/N). A dedicated application system allows accurate administration of 3He boli at different time points during inspiration. Thus, dynamic ventilation imaging becomes possible. Prerequisites for this method include a dedicated coil as well as a spectroscopy option at the MRI system. Fast sequences and low flip angles are employed to comply with the relaxation of hyperpolarise 3He in vivo.Overall homogeneous signal intensity (SI) represents physiological conditions. Obstructive lung disease is associated with generalised or localised signal inhomogeneity. Different time constants of specific lung regions are probably responsible for this kind of inhomogeneous inspiratory distribution of ventilation. Tumours show a clear ventilation deficit, correlating with non-ventilated lung areas.3He MRI is a promising new modality for the evaluation of ventilation distribution under different pathological conditions. This may include obstructive lung disease and assessment of ventilation distribution before and after thoracic surgery. Furthermore, evaluation of patients with acute lung failure and validation of ventilator settings in anaesthesia may be performed.

In the frame of the A1-Collaboration at the Mainz Microtron a test measurement of doubly polarized 3He(e,e′n) scattering from a high pressure target was performed in July aiming for the determination of the neutron electric form factor Gen at high momentum transfer (Q2=0.7(GeV/c)2). Due to the small value of Gen compared to Gmn a preferred procedure is to determine the asymmetry in the exclusive quasi elastic scattering of polarized electrons (P≈70%, I⩾2μA) from polarized 3He. The scattered electrons are detected in a high resolution magnetic spectrometer while the scattering angles of the outgoing neutrons are measured in a plastic scintillator. In this reaction the polarized 3He nucleus serves as an effective polarized neutron target. Because of the large magnetic field gradients caused by the spectrometer and limited space at the target place, the 3He gas is polarized elsewhere and transported to the target place in specially prepared glass cells. The glass cells are designed for high pressure (up to 10 bar) and with thin windows to prevent background. To reduce the relaxation due to the magnetic field gradients a μ-metal shielded guiding field of 4 Gauss is used. The guiding field is generated by three independent coils which permit the rotation of the target spin in any direction desired, especially perpendicular and parallel with respect to q. So we are able to take the ratio of the asymmetries A⊥/A∥, which in first order depends only on kinematical factors and the ratio Gen/Gmn. The method of metastable optical pumping is used to polarize the 3He at about 1 mbar with a LNA laser (≈6W). Subsequently the gas is compressed by means of a two-stage-piston compressor up to 6 bar with a polarization of roughly 45%.In the frame of the A1-Collaboration at the Mainz Microtron a test measurement of doubly polarized 3He(e,e′n) scattering from a high pressure target was performed in July aiming for the determination of the neutron electric form factor Gen at high momentum transfer (Q2=0.7(GeV/c)2). Due to the small value of Gen compared to Gmn a preferred procedure is to determine the asymmetry in the exclusive quasi elastic scattering of polarized electrons (P≈70%, I⩾2μA) from polarized 3He. The scattered electrons are detected in a high resolution magnetic spectrometer while the scattering angles of the outgoing neutrons are measured in a plastic scintillator. In this reaction the polarized 3He nucleus serves as an effective polarized neutron target. Because of the large magnetic field gradients caused by the spectrometer and limited space at the target place, the 3He gas is polarized elsewhere and transported to the target place in specially prepared glass cells. The glass cells are designed for high pressure (up...

Magnetic Resonance Imaging (MRI) usually relies on magnetization of hydrogen nuclei (protons) in water or molecules in tissue as source of the signal. Biological environments with low proton content, notably the lungs, are difficult to image. Inhaling of hyperpolarized 3He gas opens the possibility to investigate ventilated spaces by MRI. To overcome the loss in signal due to the low density of the gas the nuclear polarization of the 3He spins is greatly enhanced by laser Optical Pumping. For more than three decades Optical Pumping of noble gases has been investigated, using spin exchange scattering (SE) or metastability exchange scattering (ME). Since powerful resonant laser light is available for Optical Pumping, large quantities of 3He gas can be operated. The original interest was the development of dense spin polarized targets for fundamental research in physics. As a spin off, the possibility of MRI of lung tissue filled with hyperpolarized 129Xenon was demonstrated in 1994. Later 3He was used for M...

of the study is the visualisation of normal pulmonary ventilation in healthy volunteers and the evaluation of abnormalities in patients with different lung diseases using 3He magnetic resonance imaging (3He-MRI).Hyperpolarized 3He gas (V = 300 ml, p = 3 x 10(5) Pa, polarised to 35-45% by optical pumping, provided in special glass cells) was inhaled by eight healthy volunteers and ten patients with different lung diseases. A 3D FLASH sequence (TR = 11.8 ms; TE = 5 ms; matrix 144 x 256, FOV 350 mm, section thickness 7-10 mm, coronal orientation) was performed in a single breath-hold (22-42 s). Clinical and radiological examinations were available for correlation.The studies were successfully carried out in 8/8 volunteers and in 8/10 patients. The central airways were constantly visualised with intermediate to high signal intensity. The lung parenchyma of volunteers with normal ventilatory function showed rather homogeneous intermediate to high signal, whereas patients with chronic obstructive lung disease and/or pneumonia presented severe signal inhomogeneities. Space-occupying lesions and pleural effusion caused large areas with little or no signal. The represented the lesion and adjacent ventilatory disturbances whose extent had not been presumed from chest x-ray or CT. The spatial resolution was higher than in ventilation scintigraphy.3He MRI is a promising new modality for the assessment of pulmonary ventilation and its anomalies.

The application of Collinear Resonance Ionization Spectroscopy for the determination of 89,90Sr contaminations in various environmental samples is presented, demonstrating the versatility of this highly specialized and isotope‐selective ultra‐trace determination technique. Additionally to these studies we have analysed the different processes, which lead to nonselective ionization and hence cause background. Optimization of the experimental conditions resulted in a significant lowering of the detection limit to a value of 3×106 atoms of 90Sr (corresponding to an activity of 2mBq) in the presence of up to 1017 atoms of stable 88Sr. In a parallel measurement trace determination of both isotopes 89Sr and 90Sr is possible with a detection limit for 89Sr of 108 atoms. Measurements on different samples, ranging from air filter samples of 1958 up to today, soil, vegetation, milk and human urine samples as well as cooling water from nuclear power plants document the applicability and the specifications of the tec...

Collinear resonance ionization spectroscopy has been developed as a sensitive technique for fast trace detection of 90Sr and 89Sr in the environment. A detection limit for 90Sr of 107 atoms in the presence of 1017 atoms in the presence of 1017 atoms of stable Strontium has been achieved, while the applicability of the method has been demonstrated on real world samples. After collection and chemical separation, strontium is surface ionized, accelerated to 33keV and mass separated. The ions are neutralized and the emerging fast atoms interact with an argon ion laser beam (γ=364 nm) in a quasi‐collinear geometry. Optical excitation starts from the long‐lived 5s4d3 D2 state of strontium, which is populated in the charge exchange process, and the fast atoms are selectively excited into the high‐lying 5s23f3F3 Rydberg state. The Rydberg‐atoms are subsequently field‐ionized and detected by a channeltron detector after energy selection. The described method was successfully used to determine the 90Sr‐content in a...

The proposal by Jerkins et al (2010 New J. Phys. 12 043022) to determine the neutrino mass from a complete kinematic reconstruction of the β-decay of trapped, cold tritium atoms is reanalyzed here. It is found that this innovative concept will hardly lead to competitive results because of the following shortcomings that have been identified: (i) a viable concept for a β-spectrometer with the required performance is missing; (ii) a factor of 106 in the event rate is missing; and (iii) controlling spurious electromagnetic potentials to the level of 10−13 Tm and 10−9 V is hardly conceivable.

The strongly spin-dependent absorption of neutrons in nuclear spin polarized 3He opens the possibility to polarize beams of thermal and epithermal neutrons. An effective 3He neutron spin filter (NSF) requires high 3He nuclear polarization as well as a filter thickness corresponding to amount of gas in the order of 1 bar 1. We realized such a filter using direct optical pumping of metastable 3He∗ atoms in a 3He plasma at 1 mb. Metastable exchange scattering transfers the angular momentum to the whole ensemble of 3He atoms. At present 3.6 × 1018 3He-atoms s−1 are polarized up to 68%. Subsequent polarization preserving compression by a two-stage compressor system enables to prepare NSF cells of about 300 cm3 volume with 3 bar of polarized 3He within 2 h. 3He polarizations up to 53% were measured in a cell with a filter length of about 15 cm. By this cell a thermal neutron beam from the Mainz TRIGA reactor was polarized. A wavelength selective polarization analysis by means of Bragg scattering revealed a neutron polarization of 84% at a total transmission of 12% for a neutron wavelength of 1 A.

The new methods of laser spectroscopy have not only increased the precision of optical experiments by large factors, but also have increased their sensitivity to a level where they become feasible for the small numbers of atoms produced far off stability. The author gives a brief discussion of atomic hyperfine structure and isotope shift of optical spectra before describing some of these experiments.

A Rb-magnetometer was constructed for a wide range of application. It uses a very small optically pumped resonance cell with an active volume of less than 0.1 cm3 as the sensor element. The cell is housed in a small probe containing polarizer, rf-coil, heater and photoelement. The pumping light is brought to the resonance cell by use of a 3 m long fibre optics. The magnetometer allows continuous monitoring or stabilizing magnetic fields from about 3·10−8T to beyond 0.3T. The ultimate sensitivity of the instrument is of the order of 10−10T. Observing the Hanle signal in the transverse mode of optical pumping the instrument can be used for zero field detection and for the measurement for weak fields by means of field compensation.

Microwave transitions between the Zeeman split doublet states 22 P 1/2 and 22 P 3/2 of7Li have been measured using the optical double resonance method. The fine structure separation was determined to bev fs=10.053.184(58) MHz. The hyperfine structure was well resolved and led to considerably improved precision of the diagonal coupling constantsa 1/2=45.914(25) MHz,a 3/2=−3.055(14) MHz,b=−0.221(29) MHz. Furthermore, the contact, spin dipolar and orbital magnetic hyperfine constants are evaluated using additional results from level crossing experiments, which are more sensitive on the non-diagonal magnetic hyperfine constanta 3/2,1/2. The results are in good agreement with recent theoretical calculations. The nuclear quadrupole moment is derived fromb to beQ(7Li)=−41(6) mbarn.

A resonant ionization mass spectrometer has been developed as an analytical tool for the detection of trace elements, especially of plutonium and other radionuclides. The sample, deposited on a rhenium filament, is evaporated by electrical heating and the atoms of the element under investigation are selectively ionized by laser light delivered from three dye lasers pumped by a copper vapour laser. The resulting photoions are detected in a time-of-flight spectrometer with a channelplate detector. For plutonium a mass resolution of M/δM=1500 was obtained and an overall detection efficiency of 4×10−6 was determined for stepwise excitation and ionization via autoionizing states. With a laser light bandwidth of 3–5 GHz neighbouring isotopes could be suppressed by a factor of 20 due to isotope shifts in the excitation transitions. The isotope composition of synthetic samples was measured and good agreement was found with mass spectroscopic results. The influence of the hyperfine structure on the isotope ratios is discussed.

The possibilities of determining nuclear spin, moments and variation in charge volume by optical pumping of on line masseparated isotopes are described for the example of the isotopic chain lY1Hg-205Hg. The variation in nuclear charge volume (6 ) along this chain and in particular its abrupt change for the lightest Hg-isotopes, indicating a phase transition in nuclear structure, are discussed. 1. Introduction. - This talk is based on expe- riments (I), (2), (3) performed recently by a visiting team (*) at the ISOLDE facility at CERN with the members : J. Bonn, G. Huber, H.-J. Kluge, U. Kopf, L. Kugler, J. Rodriguez, and E. W. Otten. The investigation of the hyperfine structure (hfs) and isotopic shift (IS) of optical spectra allows the determination of the basic nuclear ground state properties : spin (I), magnetic moment (p,), electric quadrupole moment (Q,), and change of the mean squared radius of the nuclear charge distribution between different isotopes (6 ). The subject has therefore widely been explored in the past for stable and long lived isotopes (4), (5) and contributed substantially to the systematic topography of nuclear structure in the valley of stability which could be established within the last two decades. Still basical and quantitative questions are open in understanding nuclear matter. In this situation it makes from first principles is missing. In this situation it makes sense to enlarge the scope of investigations principally. In particular we should be in a position to choose and change systematically the parameters N and Z of a nucleus independently and free from the boun- dary condition of being close to the stable valley. With other words, a systematic investigation of nuclear properties along lines of constant Z or N across the full array of nuclei which we can reach in our days, would give us a much wider and more reliable view on the topography of nuclear structure (*) In the course of the experiments the team changed its home university from Heidelberg to Mainz.

The nuclear Zeeman levels of the ground state of Barium (6s21S0, F=I=3/2) were polarized by means of optical pumping with the resonance line (6s21S0−6s 6p1P1, λ=5535 A). The magnetic field was calibrated by means of optical pumping of sodium. The magnetic moments, calculated from the nuclear Hf-Zeeman-transitions at 228 Gauss are μ135=0,83651 (6) μN μ137=0,93573 (6) μN (with diamagnetic correction).

The3 P 1 state of Ca (τ≈0,5 msec) was populated by resonance-absorption of the intercombination line (λ=6572,8 A). The radio-frequency-transitions between the Zeeman-sublevels of the excited state were observed by means of optical double-resonance. Because of the oscillator-strength of the intercombination line being extremely small, a second excitation method, namely with electron impact, was tried. Both methods yielded equivalent results. In order to determine theg J -value of the3 P 1-state the static magnetic field was calibrated by Zeeman-transitions in the ground state of Na, the transitions being detected by optical pumping,g J was found to be 1,50105(7) in agreement with the theoretical value 1,50108.

High frequency transitions in the hyperfine structure of the excited 7 / sup 2/P/sub 3/2/ terms of the Cs I-spectrum were detected by means of the double resonance method. The measurements were made on a 0.2 mc sample of a fission product which contained the radioisotopes Cs/sup 135/ and Cs/sup 137/ as well as the stable isotope Cs/sup 133/ in approxi mately equal concentrations. For the nuclear quadrupole moments of the radioisotopes the values Q(Cs/sup 135/) = (+0.049 plus or minus 0.002) x 10/sup -24/ cm/sup 2/ and Q(Cs/sup 137/) = (+0.05 0 plus or minus 0.002) x 10/sup -24/ cm were obtained. (tr-auth)

Laser resonance ionization mass spectrometry has been investigated as a method for the determination of trace amounts of actinides and technetium. A high sensitivity and selectivity have been achieved by three-step photoionization of the elements in the atomic state followed by time-of-flight measurement for mass analysis. The system for photoionization consists of three dye lasers which are pumped simultaneously by a copper vapour laser of 30 W average power at a pulse repetition rate of 6.5 kHz. The time-of-flight spectrometer has a mass resolution better than 2500. By ionization via autoionization states and by saturation in each excitation step a detection limit of less than 108 atoms of actinides or of technetium in the sample can be reached.

The nuclear Zeeman levels of the odd isotopes of Ytterbium (171Yb,171 I=1/2;173Yb,173 I=5/2) were polarized in the atomic ground state (6s 2 1 S 0) by means of optical pumping with the resonance line (6s 2 1 S 0 ↔ 6s6p 1 P 1,λ=3988 a). The magnetic moments, calculated from the nuclear Hf-Zeeman transitions in a magnetic field of 228 Gauss are171 Μ I=0.49188 (2)Μ K 173 Μ I=0,67755 (3)Μ K (with diamagnetic correction applied).

Nuclear spin, moments and isotope shifts of charge radii have been measured by laser spectroscopy for about 70 nuclear states in the range 48 ≦ Z ≦ 50, 54 ≦ N ≦ 78. 1/2--states in heavy In-isotopes cross the Schmidt line, indicating complex nuclear structure. Magnetic as well as spectroscopic quadrupole moments of most of the odd odd In-isotopes can be reproduced satisfactorily by coupling the respective experimental moments of odd even and even odd neighbouring nuclei. The isotope shift of all three elements exhibits a parabolic shape, which is superimposed to the almost linear droplet model expectation. The shape can be fitted quantitatively to Talmis core polarization model. The curvature of the parabola which peaks in the middle of the neutron shell is a direct measure of the collective contribution to the charge radius. It corresponds to deformation parameters 〈β2〉 twice as large as observed from B(E2, 0+→2 1 + ) values. One suggests, therefore, that the latter one does not exhaust the full collectivity of the nuclear ground state. By comparing to charge radii in the Rb and Cs region one derives isotonic and isobaric shifts in accordance with the droplet model. The isobaric shifts may be interpreted as a build up of a neutron skin in a simple way.

In this talk I will review optical pumping (OP) experiments performed by our group to ISOLDE, CERN, in a series of Hg isotopes spanning from mass number 181 to 205 (first results in refs. [1] and [2], final in refs. [3] and [4]. I will then discuss what impact these measurements had on nuclear structure research far off stability and how the results of the latter are retroacting again on the optical work. In particular they ask for isotope shifts (IS) of light even Hg isotopes which we are prepared to measure by laser spectroscopy. Further I would like to communicate briefly first results of optical pumping experiments on “exotic” Rb and Cs isotopes. Finally I will discuss plans for laser spectroscopy on fast mass-separated beams which might favourably be applied to isotopes far off stability.

The application of lasers in fundamental nuclear research has been devoted predominantly to the investigation of nuclear structure of unstable isotopes through the measurement of isotope shift and hyperfine splitting of the atomic spectrum of the nuclei in question. From the isotope shift one deduces the change of nuclear charge distribution — or more precisely the change of the mean-squared nuclear charge radius δ -, whereas the hyperfine structure yields the spin (I), the magnetic moment (μI) and the electric quadrupole moment (Qs) of the nucleus. These four nuclear properties form the cornerstones for any quantitative theory of nuclear structure. In this respect, systematic measurements, throughout the nuclear chart of elements are particularly important. This implies experiments on extended series of isotopes which reach far out into the region of unstable and short-lived nuclei.

The excited 7/sup 2/P/sub 3/2/ term of the neutral atom was investigated in Cs/sup 135/ and Cs/sup 137/ by the Doppler resonance method. An isotopic mixture containing 39.4% Cs /sup 133/, 30% Cs/sup 135/, and 30.6% Cs/sup 137/ was used in the measurements. The nuclear quadrupole moments were calculated to be Q(Cs/sup 135/) = +(0.049 plus or minus O.0l) x 10/sup -24/ and Q(Cs/sup 137/) = +(0.050 plus or minus 0.01) x 10/sup -24/ cm/sup 2/. (J.S.R.)