Source of polarised deuterons

The proposed project assumes the development of a universal high-intensity source of polarized deuterons (protons) using a charge-exchange plasma ionizer. The design output current of the source will be up to 10mA for ↑ D⁺(↑ H⁺) and polarization will be up to 90% of the maximal vector (±1) and tensor (+1,−2) polarization. The project is based on the equipment which was supplied within the framework of an agreement between JINR and IUCF (Bloomington, USA). The project will be realized in close cooperation with INR (Moscow, Russia). The source will be installed in the linac hall (LU-20) and polarization of beams will be measured at the output of LU-20. The main purpose of the project is to increase the intensity of the accelerated polarized beams at the JINR Accelerator Complex up to 10¹⁰ d/pulse. Calculations and first accelerator runs have shown that the depolarization resonances are absent for the deuteron beam in the entire energy range of the NUCLOTRON. The source could be transformed into a source of polarized negative ions if necessary. The period of reliable operation without participation of the personnel should be within 1000 hours. The project should be implemented within two to two and a half years from the start of funding.     

Photoproduction of π+ mesons on polarized protons at photon energies between 0.5 and 2.2 GeV

The target asymmetry T = (σ↑ ? σ↓)/(σ↑ + σ↓) for the reaction γp → π⁺n has been measured at the Bonn 2.5 GeV electron synchrotron for a pion c.m. angle of 40° and γ energies between 0.5 and 2.2 GeV. Butanol was used as the target material. About 35% of the protons could be polarized using the dynamic-polarization method in a continuous-flow cryostat operating at 1°K and 25 kG. The π⁺ mesons were detected in a magnetic-spectrometer system. Considerable structure in the asymmetry was observed.     

Accurate rest frequencies of submillimeter-wave lines of H2D and D2H

We re-examined the submillimeter-wave transition frequencies of H₂D⁺ (J = 1₁₀ − 1₁₁ at 372.4 GHz) and D₂H⁺ (J = 1₁₀ − 1₀₁ at 691.7 GHz) to resolve suggested slight difference in velocity (v_LSR) of these species detected in the cold pre-stellar core 16293E recently. Both H₂D⁺ and D₂H⁺ were generated in a magnetically confined extended-negative glow discharge of a gaseous mixture of H₂/D₂/Ar. A combination of small improvements in various aspects of the measurements such as double modulation technique combined with a conventional frequency modulation and magnetic field modulation and more efficient signal accumulation method allowed us to improve signal-to-noise ratio, and thus to determine the transition frequencies more accurately. Both transition frequencies for the H₂D⁺ and D₂H⁺ lines have been thus determined to be 372421.385(10) and 691660.483(20) MHz, respectively. These precise rest frequencies suggest that the v_LSR of H₂D⁺ and D₂H⁺ in the pre-stellar core 16293E are indeed different as indicated in a recent astronomical observation. In addition, in this investigation, another transition of H₂D⁺ which falls in this frequency region, J = 3₂₁ − 3₂₂ transition, has been observed at 646430.293(50) MHz. As H₂D⁺ is a lightest asymmetric-top molecule and it is difficult to predict the rotational transition frequencies by using the effective asymmetric rotor Hamiltonian, any new observation of the rotational lines will be useful to improve the molecular parameters. The molecular constants for the ground state have been obtained for H₂D⁺ and D₂H⁺ by fitting these new measured frequencies together with the combination differences.     

^3 \overrightarrow {He} (γ, π°)^3 \overrightarrow {He} as the nuclear probeas the nuclear probe

The state of polarization of the recoil nucleus inγ+³He→π°+³He as well as the asymmetry in the differential cross-section when the initial³He is polarized are studied together with the differential cross-section taking into consideration theS, S′ andD-state admixtures in the nuclear wavefunctions. In view of the considerable spin dependence in the photoproduction amplitudes these observables are found to be quite sensitive to the small admixtures ofS′ andD-states in the nuclear wave-functions.     

Parity violation in the 17/2− isomer of93Tc

The parity-violating mixing of the 17/2^? and 17/2⁺ levels in⁹³Tc nuclei, polarized by the tilted multifoil interaction, was measured by the observation of the forwardbackwardγ-ray asymmetry. The asymmetry was determined to beA _γ=1.18(48)×10^?3. The nuclear polarization was determined in a measurement of the quadrupole interaction in a⁹²Mo isomer and the parity violation matrix element 〈H _PV〉 is found to be ¦〈H _PV〉¦ =0.8(4) meV.     

Spin physics at HERMES

The primary goal of the HERMES experiment is the study of the spin structure of the nucleon. Results on the measured inclusive and semi-inclusive hadron asymmetries using a polarized positron beam on polarized ³He, hydrogen and deuterium targets are here presented. In the covered kinematic range, 0.023<x _Bj <0.6 and 1 GeV²<Q ²<10GeV² the polarized quark distribution were determined for all up (u+?u) and down (d+?) quarks, and separately for valence and sea quarks. The up quark polarization is positive, and the down quark polarization is negative. The polarization of the sea is consistent with zero in the measured range. A first indication of a positive gluon polarization is presented, based on the measured spin asymmetry in the photo-production of hadron pairs with high transverse momentum p _T . This asymmetry is negative, which is in contrast to the measured positive asymmetry for inclusive experiments.     

The structural and electric behavior of SrBi2Ta2O9 ferroelectric thin films with H+ implantation

The structural and electrical characteristics of H⁺-implanted SrBi₂Ta₂O₉ (SBT) ferroelectric thin films were investigated by X-ray diffraction analysis and electrical measurements. 25 keV H⁺ with doses ranging from 1 × 10¹⁴/cm² to 3 × 10¹⁵/cm² were implanted into the Sol-Gel prepared SBT ferroelectric thin films. The X-ray diffraction patterns of SBT films show that no difference appears in the crystalline structure of H⁺-implanted SBT films compared with unimplanted films. Ferroelectric properties measurements indicate that both remnant polarization and the coercive electric field of H⁺-implanted SBT films decrease with increasing the implantation dose. The disappearance of ferroelectricity was found in the H⁺-implanted SBT films up to a dose of 3 × 10¹⁵/cm². The leakage current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the H⁺-implanted SBT films were also discussed before and after a recovery process.     

Kontinuierlicher Absorptionsquerschnitt von Argon im Bogenplasma

Optical pumping on Cs¹³³ atoms was performed by means of a new transmission technique. The cesium vapor was pumped towards equilibrium by an intensive circulary polarizedD ₁ orD ₂ light beam. A weakD ₁ detecting beam was polarized alternately σ⁺, σ^? and allowed one to measure continuously amount and sign of the absorption difference between σ⁺ and σ^? light. The measured signals are proportional to the electron spin polarization. The new technique was used to investigate the influence of Cs buffer gas collisions on the pumping cycle and to measure the influence of radio frequency induced Zeeman transitions on the ground state polarization. In addition the variation of magnetic field and of pumping light intensity and polarization was studied. Some measurements demonstrate the high sensitivity of the applied method. The obtained qualitative results are discussed and further experiments are proposed.     

Chemisorption of H2 on W(100): Absolute sticking probability,coverage, and electron stimulated desorption

Measurements of both the absolute sticking probability near normal incidence and the coverage of H₂ adsorbed on W(100) at ~ 300K have been made using a precision gas dosing system; a known fraction of the molecules entering the vacuum chamber struck the sample crystal before reaching a mass spectrometer detector. The initial sticking probability S₀ for H₂/W(100) is 0.51 ± 0.03; the hydrogen coverage extrapolated to S = 0 is 2.0 × 10¹⁵ atoms cm^?2. The initial sticking probability S₀ for D₂/W(100) is 0.57 ± 0.03; the isotope effect for sticking probability is smaller than previously reported. Electron stimulated desorption (ESD) studies reveal that the low coverage β₂ hydrogen state on W(100) yields H⁺ ions upon bombardment by 100 eV electrons; the ion desorption cross section is ~ 1.8 × 10^?23 cm². The H⁺ ion cross section at saturation hydrogen coverage when the β₁ state is fully populated is ? 10^?25 cm². An isotope effect in electron stimulated desorption of H⁺ and D⁺ has been found. The H⁺ ion yield is ? 100 × greater than the D⁺ ion yield, in agreement with theory.     

Theoretical study of deuteron polarization in γ+d → π0+d

The state of polarization of the recoil deuteron in γ+d → π⁰+d on unpolarized and target polarized deuterons is analyzed in detail. A new set of statistical tensors is introduced to describe non-oriented systems, such as the recoil deuteron in γ+d → π⁰+d, and their relationships to the vector and tensor polarization parameters are established. The new statistical tensors reduce, in the case of oriented systems, to Fano's statistical tensors. Numerical results are computed using two different deuteron models for polarized photon asymmetry, polarized target asymmetry and the vector and tensor polarizations of the recoil deuteron, and these are presented at various c.m. pion production angles at different energies in the region of the first π-N resonance. The study of these parameters is suggested as a promising source of information on isoscalar pion photoproduction amplitudes.     

Studies of basic limitations on production, transport and acceleration of the high intensity polarized H− beam in the RHIC polarized ion source

Basic limitations on the high-intensity polarized H^? ion beam production and transport were experimentally studied in charge-exchange collisions of the neutral atomic hydrogen beam in the Na-vaporjet ionizer cell. The energy dependence of space-charge effects on the beam instabilities and losses were studied and described in the model of synthetic H⁺ — H^? beam transport. A xenon gas admixture to the H^? ion production cell and beam transport line greatly improves the space-charge compensation, which is also successfully described in the simulations. These studies are the part of the polarized source upgrade project for RHIC.     

Linearly-polarized Tm-doped double-clad fiber laser

We report a linearly polarized Tm doped fiber laser. The fiber laser was set up by using a piece of polarization maintaining Tm doped double clad fiber of 5 m length as gain medium and a polarization beam splitter as a polarization selector. The fiber laser was pumped by a fiber pigtailed laser diode working at 790 nm with a maximum output power of 90 W. The linearly polarized Tm laser operated at wavelength around 2030 nm. A maximum output power up to 21.9 W was achieved when the pump power was 63.27 W with a threshold of 11.92 W, a slope efficiency of about 43.7%, and a polarization extinction ratio of 92.7% (11.37 dB). In addition to the blue fluorescence, we also observed the violet fluorescence under high pump power level. The up-conversion fluorescence was considered to be attributed to the ¹ G ₄ → ³ H ₆, and ¹ D ₂ → ³ F ₄ transitions of Tm ions, respectively.     

Neutron diffraction study on the hyperfine-induced nuclear spin order in the antiferromagnet PrSn3

At several $\text{(h+}\text{1}\text{2}\text{0 0)}$ reciprocal lattice positions of PrSn₃, we observed Bragg scattering of neutrons which is purely due to the nuclear spin polarization of ¹⁴¹Pr, and could measure the temperature dependence of the polarization between 10 mK and 4.2 K. From the perfectly polarized state of the nuclear spins, the difference between the spin-dependent nuclear scattering lengths b⁺ and b^- has been determined to be b⁺ - b^- = -0.110 ± 0.006 × 10^-12 cm, which is significantly larger in magnitude than the previously reported value. An additional electronic polarization which is linearly proportional to the nuclear spin polarization has also been observed.     

Beitrag zur Kernspektroskopie an36Cl,90Y und40K durch Messung der Polarisation von γ-Strahlung nach Neutroneneinfang

The circular polarization ofγ-rays following the capture of polarized thermal neutrons in nuclei was measured. The degree of polarization confirmed the spin 2⁺ for the 0.777 MeV level of⁹⁰Y and the spin 0^? or 3^? for the 0.029 MeV level of⁴⁰K. Further theE2/M1 mixing ratio of the 8.58 MeV decay to the ground state of³⁶Cl was measured.     

The RHIC polarized source upgrade

The RHIC polarized H^? ion source is being upgraded to higher intensity and polarization for use in the RHIC polarization physics program at enhanced luminosity RHIC operation. The higher beam intensity will allow reduction of the longitudinal transverse beam emittance at injection to AGS to reduce polarization losses in AGS. There is also a planned RHIC luminosity upgrade by using the electron beam lens to compensate the beam-beam interaction at collision points. This upgrade is also essential for future BNL plans for a high-luminosity electron-proton (ion) Collider eRHIC. The basic limitations on the high-intensity H^? ion beam production in charge-exchange collisions of the neutral atomic hydrogen beam in the Na-vapor jet ionizer cell were experimentally studied.     

Investigation of the external-magnetic-field dependence of polarization transfer in a 8Li-6Li disordered nuclear system

Random walks in disorderedmedia are studied by considering the example of the delocalization of nuclear polarization in an ensemble of ⁸Li beta-active nuclei produced in (n, γ) reactions induced by polarized thermal neutrons in LiF single crystals. The process is initiated by magnetic dipole-dipole interactions. It consists in polarization transfer from a primarily polarized ⁸Li nucleus to the closest (stable) ⁶Li nuclei and in subsequent polarizationmigration over 6Li nuclei, the return of the polarization in question to the ⁸Li nucleus being possible. In order to obtain information about the polarization of ⁸Li nuclei, the asymmetry of beta radiation from them was measured with respect to the external magnetic field H ₀. The process was studied until it reached the diffusion asymptotic regime. The concentration of ⁶Li was varied between 3% and 10%, while the field strength H ₀ was changed from 200 to 1200 G. It is shown that microscopic theory is in satisfactory agreement with the experimental results obtained in the way outlined above. A comparison with the investigation of the mathematically allied process of the Förster electricdipole transfer of localized excitons is performed.     

Single-spin asymmetry of inclusive π 0-meson production in 40-GeV pion interactions with a polarized target in the target-fragmentation region

Data on the single-spin asymmetry (A _N) of inclusive π ⁰ production in 40-GeV pion interactions with a polarized target, π^? + _↑→π⁰+X, are presented for the target-fragmentation region. The result is A _N=(?13.8±3.8)% for ?0.8<x _Fp _T<2 GeV/c and is compatible with zero for ?0.4<x _Fp _T<1.5 GeV/c. At a π ⁰ momentum of about 1.7 GeV/c in the c.m. frame, the asymmetry becomes nonzero both in the central and in the target-fragmentation region. The behavior of the asymmetry is similar to that observed in the beam-fragmentation region of the E-704 (FNAL, 200 GeV) and STAR (BNL, 20 TeV) experiments, which employed a polarized proton beam.     

Transverse polarization of the lepton in the decay process <Emphasis Type="Italic">B</Emphasis> → <Emphasis Type="Italic">Dlν</Emphasis><Subscript>l</Subscript> due to electromagnetic final-state interaction

The emergence of transverse polarization of the lepton in the decay processes B⁰ → D^?l⁺ν_l and \(B^ + \to \bar D^0 l + \nu _l \) for l = τ, μ is studied on the basis of the Standard Model in the leading approximation of heavy-quark effective theory. It is shown that a nonzero transverse polarization appears owing to electromagnetic final-state interactions at the one-loop level. Diagrams involving D and D* mesons in the intermediate state and making a nonzero contribution to the transverse polarization of the outgoing lepton are considered. If only these mesons are taken into account in evaluating the mean values of the τ-lepton polarization in the decays B⁰→D^?τ⁺ν_τ and \(B^ + \to \bar D^0 \tau ^ + \nu _\tau \), the results are 2.60×10^-3 and ?1.59×10^?3, respectively. The corresponding values of the transverse muon polarization averaged over the Dalitz plot are 2.97×10^?4 and-6.79×10^?4.