Search

The prototype of a nuclear-polarized hydrogen/deuterium molecular source based on the classical Stern–Gerlach design was tested at the Budker Institute of Nuclear Physics. Its major components are an annular nozzle cooled down to 6.5 K and two superconducting sextupole magnets. The measured flow of polarized hydrogen molecules was 3 × 1012 mol/s at a total gas flow through the nozzle of 4 ×10–2 Torr L/s. The results obtained will be used to construct a more intense source of polarized molecules.

We simulate the motion of hydrogen and deuterium molecules in the magnetic system of a setup intended for obtaining nuclear-spin-polarized molecules. Spatial separation of molecules with different magnetic moment projections by the spin filtration method in a nonuniform magnetic field is performed using superconducting sextupole magnets. Calculations are carried out for a magnetic field induction of 3.7 T at the poles and a nozzle temperature of 7 K. Simulation show that the ratio of polarized flux of hydrogen molecules to the detector to the total flux from the source nozzle is 2.3 × 10–6, nuclear polarization being close to 100%. Calculations performed for deuterium reveal that this ratio is 7 times smaller due to the smallness of the magnetic moment relative to hydrogen molecules. Trajectories of molecules in the magnetic system and their spatial distribution are represented graphically. Mathematical aspects of the algorithm of the computer program developed for this purpose are considered.

The paper presents the results of measurement of three tensor analyzing power components for the incoherent π 0 -meson photoproduction on a deuteron in the photon energy range of 250 – 500 MeV, the proton energy range of 15 – 200 MeV, and the neutron energy range of 15 – 150 MeV. The incoherent π 0 -meson electroproduction on a deuteron was used as a source of quasireal photons for the incoherent π 0 -meson photoproduction. The experiment was performed using an internal tensor-polarized gas deuterium target of the VEPP-3 electron storage ring by the proton-neutron coincidence method. The results of measurement of the tensor analyzing power components are compared with the results of statistical modeling performed in the framework of a theoretical model.

The results of measurements of three tensor analyzing power components of the reaction of incoherent photoproduction of a π0-meson on a deuteron in the ranges of proton and neutron energies, 15–200 and 15–150 MeV, respectively, are presented. The experiment is performed on an internal tensor-polarized gaseous deuterium target of a VEPP-3 electron storage ring using the method of proton and neutron coincidence counting. The results of measurements of tensor analyzing power components are compared with those obtained by statistical modeling performed within a theoretical model.

The setup is designed to produce spin-polarized hydrogen and deuterium molecules. Superconducting sextupole magnets with a magnetic induction of 3.4 T near the poles and a field gradient of 320 T/m were used for the spatial separation of molecules with different magnetic moments by spin filtration in an inhomogeneous magnetic field. The choice of the location of the polarized-molecule source elements is justified. Cryogenic pumps are used in the molecular-beam detection chamber in order to obtain an ultrahigh vacuum. At a nozzle temperature of 7 K, the measured flux of spin-polarized hydrogen molecules is 3 × 1012 molecules/s. For deuterium, the measured flux is lower by more than seven times due to the small magnetic moments.

We present the first accurate results of measurements of the tensor analyzing power component $$T_{20}$$ for the coherent neutral pion photoproduction on the deuteron. The measurements were performed at the Budker Institute of Nuclear Physics at VEPP-3 storage ring using the internal tensor polarized deuterium target. The measurements cover the region of photon energy from 200 to 450 MeV and the region of the center-of-mass pion polar angle from 100 to 140 degrees. The results obtained are compared with predictions of several theoretical models.

Results obtained by measuring three components of the tensor analyzing power in the reaction of π- meson photoproduction on deuterons in the range of photon energies 300–800 MeV and proton energies 15–70 MeV are presented. The experiment was performed with an internal tensor-polarized deuterium target at the VEPP-3 electron storage ring, employing the method of recording two protons in coincidence. The obtained measurement results for the tensor analyzing power are compared with theoretical predictions.

The first results of a double polarization experiment to extract the asymmetry of the reaction of photoproduction of a π- meson by a linearly polarized photon on a tensor-polarized deuteron in the energy range of the virtual photon (300–700 MeV) are presented. The measurements were performed on an internal tensor-polarized deuterium target in the VEPP-3 electron-positron storage ring for the electron beam energy equal to 2 GeV. The experiment employed the method of recording two protons and the scattered electron in coincidence. The obtained measurement results are compared with the theoretical predictions obtained in the momentum approximation with allowance for πN and NN rescattering in the final state.

Three components of the tensor analyzing power of the exclusive π − meson photoproduction on a deuteron, γ d → p p π − , are measured simultaneously for the photon energy range ( 300 – 900 ) MeV , detecting a pair of protons in the energy range ( 50 – 200 ) MeV . The experiment made use of an internal tensor-polarized deuterium gas target of the VEPP-3 electron storage ring and the two-proton coincidence recording method. The results obtained are compared with theoretical predictions within the framework of the diagrammatic approach.

This paper presents new results for the [Formula: see text]-component of the tensor analyzing power of the reaction [Formula: see text] in the photon energy range of [Formula: see text]. The experimental statistics accumulated in 2013 at the VEPP-3 accelerator-storage complex is used. The reaction events are identified by the coincidence registration of the proton and two [Formula: see text]-quanta from the decay of the neutral pion. To determine the [Formula: see text]-component, the asymmetry of the yields with respect to the change of sign of the tensor polarization of the deuterium target is measured. The experimental results are compared with the theoretical calculations in which the MAID 2007 model is used as the elementary pion–nucleon photoproduction amplitude and contributions from the pion–nucleon and nucleon–nucleon rescattering are taken into account.

Numerical and analytical calculations of the virtual photon spectrum have been performed for the electroproduction of negatively charged pions on a deuteron. The numerical calculations of the virtual photon spectrum were performed without recourse to any approximations while a number of approximations were admitted in the derivation of the analytical expression. A comparison of the results of an exact numerical calculation of the virtual photon spectrum with the results of a calculation obtained using an approximate analytical expression for the virtual photon spectrum has been performed for the first time. It is shown that the discrepancy between the virtual photon spectra obtained with the help of numerical and analytical methods can reach 10% in the kinematic region of photoproduction of pions with intermediate energies. It follows from the obtained results that in the statistical modeling of the yields of the reaction of photoproduction of negatively charged pions on a deuteron it is necessary to use the exact virtual photon spectrum obtained with the help of numerical methods whereas in the statistical modeling of the asymmetry of reactions of photoproduction of negatively charged pions on a deuteron it is sufficient to use the approximate analytical expression for the virtual photon spectrum.

A novel source of polarized hydrogen and deuterium molecules has been tested. The use of sextupole superconducting magnets allows us to select molecules with the nuclear spin projection −1 for hydrogen and −2 for deuterium. The measured beam intensity of polarized hydrogen molecules for the nozzle temperature range of 6.5–30 K and a gas flow rate up to 5 ⋅ 1 0 − 2 Torr ⋅ l ∕ s is presented. The measured flux of polarized hydrogen molecules of ≈ 3 ⋅ 1 0 12 mol ∕ s is in reasonable agreement with estimations. The obtained results can be used as a basis for the development of a high-intensity source of polarized molecules.

The study of polarization effects in reactions with a simplest nucleus, deuteron, plays an important role for the investigation of deuteron structure as well as for the research of the properties of the strong interaction. However, data on the tensor observables in the electro- and photoreactions with deuteron appeared not so long ago. We present here a brief overview of the experiments on three such reactions with a deuteron: elastic scattering, photodisintegration and coherent photoproduction of the neutral pion.

A novel source of polarized hydrogen and deuterium molecules has been tested. The use of sextupole superconducting magnets allows us to select molecules with the nuclear spin projection -1 for hydrogen and -2 for deuterium. The measured beam intensity of polarized hydrogen molecules for the nozzle temperature range of 6.5 – 30 K and a gas flow rate up to 6.6∙10^-2 mbar∙l/s is presented. The measured flux of polarized hydrogen molecules of ~ 3 ∙10^12 mol/s is in reasonable agreement with the Monte-Carlo simulation. The obtained results can be used as a basis for the development of a high-intensity source of polarized molecules.

The three components of the tensor analyzing power of the exclusive π– meson photoproduction reaction on deuterons measured simultaneously in the photon energy ranges 300–900 MeV and 50–210 MeV are presented. The experiment made use of an internal tensor-polarized deuterium-gas target of the VEPP-3 electron storage ring and the two-proton coincidence recording method. The results obtained are compared with theoretical predictions.

At the VEPP-4M collider the record accuracy of 10−6 of an absolute beam energy calibration was achieved with the resonant depolarization technique in the energy range including the J/ψ, ψ(2S), ψ(3770) resonances as well as the τ - lepton production threshold. This report discusses the methods, equipment and the results.

The possibility of producing polarized molecules of hydrogen isotopes by their spin separation in the inhomogeneous field of superconducting magnets has been demonstrated. This method proposed in our previous works has been implemented with a source of polarized atoms developed at the Budker Institute for Nuclear Physics. The measured flux of polarized molecules is compared with the simulation results. The possibility of developing a more intense source of polarized molecules is discussed.

The spin dynamics of a hydrogen atom during the passage of a periodic magnetic structure is discussed. The occupation numbers of the components of the hyperfine structure are considered as a function of time. The characteristic low-frequency oscillations are visible, which have a direct analogue in the effect of nuclear magnetic resonance. An envelope forms of these oscillations are found using the Krylov-Bogolyubov-Mitropol'skii method. The dependence of spin dynamics on the parameters of the magnetic structure is investigated. It is shown that this dependence is very sensitive to the structure of the magnetic field., 8 pages, 4 figures

The paper presents the results of measurements of the tensor analyzing power component [Formula: see text] for the coherent neutral pion photoproduction on the deuteron. The measurements were performed in the Budker Institute of Nuclear Physics using the internal tensor polarized deuterium target at VEPP-3 storage ring. The measurements covered the region of the photon energy 240 — 420[Formula: see text]MeV and the region of the center-of-mass pion polar angle 100–140[Formula: see text]. The results of measurements were compared with the calculations performed within frameworks of several theoretical models.

The paper presents results of a double polarization experiment to extract an asymmetry of the $\pi^{-}$ -meson photoproduction on a tensor-polarized deuteron by a linearly polarized photon. The energy of photons lies in the range (300-700) MeV. The measurements were performed on the internal tensor-polarized deuterium target in the VEPP-3 electron-positron storage ring for the electron beam energy equal to 2 GeV. In the experiment, two protons and a scattered electron were detected in coincidence. The results of the measurement are compared with theoretical predictions made in the framework of impulse approximation, taking into account the $\pi N$ and NN-rescattering in the final state.

The use of nuclear polarized fuel, {\it{i.e.}}~polarized D, T or $^3$He, for coming fusion reactors promises to increase their energy output and to optimize the complete fusion process in various ways. But before these advantages can be utilized, several questions have to be answered and technical issues must be overcome. Among others, the members of the PREFER collaboration started to investigate the different challenges of ``polarized fusion''.

The AuL3 XAFS spectra of gold nanoparticles in cavities of cucurbit[6,7]uril are measured. Gold clusters are found to be characterized by smaller (by 0.03 A) interatomic distances and a considerable reduction in the Au–Au coordination numbers (NAu–Au ≤ 6) as compared with bulk gold. For all samples, the size distribution of Au nanoparticles is established to have two maxima corresponding to Au in the cavities of cucurbituril molecules with sizes of D(Au) ≤ 1 nm and to macroaggregates of gold. A threefold increase in the Debye–Waller factor at 12 K for nanoparticles in comparison with the bulk metal and a corresponding increase in structural disorder are found. Special physical and chemical properties of small gold particles are dictated by structural disorder, deformations, and stresses increasing with a decrease in size. No visible differences in the Au electronic states upon the transition from bulk to nanoparticles are detected.

An experiment to measure tensor analyzing power component T 20 of the coherent photoproduction reaction of a neutral pion on a tensor-polarized deuterium target $$\left( {\gamma \vec d \to d\pi ^0 } \right)$$ is described. Measurements are made in two kinematic ranges: photon energy E γ = 200–500 MeV and neutral pion escape angle $$\Theta _{\pi ^0 }^{cm} = 100^ \circ - 140^ \circ$$ , E γ = 300–600 MeV, and $$\Theta _{\pi ^0 }^{cm} = 40^ \circ - 70^ \circ$$ . A hyperfine internal gas polarized target is used in the experiment. Detectors of neutral pions and deuterons register these particles when they coincide. The degree of target polarization and experimental luminosity are measured via the registration of elastic electron scattering on a deuteron at a low momentum of transfer. The preliminary experimental results are compared to certain theoretical predictions.

Proton electromagnetic form factors are among the most important sources of information about the internal structure of the proton. Two different methods for measuring these form factors, the method proposed by Rosenbluth and the polarization-transfer method, yield contradictory results. It is assumed that this contradiction can be removed upon taking into account the hard part of the contribution of two-photon exchange to the cross section for elastic electron-proton scattering. This contribution can measured experimentally via a precision comparison of the cross sections for the elastic scattering of positrons and electrons on protons. Such a measurement, performed at the VEPP-3 storage ring in Novosibirsk at the beam energies of 1.6 and 1.0 GeV for positron (electron) scattering angles in the ranges of θ e = 15°–25° and 55°–75° in the first case and in the range of θ e = 65°–105° in the second case is described in the present article. Preliminary results of this experiment and their comparison with theoretical predictions are described.

Measurements are presented of the tensor analyzing power of the Т21 component of photoproduction of a π–meson on a deuteron. The measurements were performed on the VEPP-3 storage ring using an internal tensor-polarization deuterium target. The experimental results are compared with theoretical calculations.

Results obtained by measuring three components of the tensor analyzing power in the reaction of π− -meson photoproduction on a deuteron at final-proton momenta between 300 and 700 MeV/c are presented. The measurements in question were performed at the VEPP-3 storage ring by using its internal deuterium-gas target featuring a tensor polarization with the aid of detection of two protons in coincidence. The experimental results obtained in this way are compared with their counterparts calculated theoretically.

New accurate measurement of tensor analyzing power $$T_{20}$$ in the reaction $$\gamma + \mathbf {d}\rightarrow \pi ^0 +d$$ has been performed at the VEPP-3 storage ring at Budker Institute, in an energy range $$200

An experiment to measure component T 20 of the tensor analyzing power for the coherent photo-production of neutral pions on polarized deuterons is described. The measurements cover the photon energies in the ranges E γ = 200–500 MeV and E γ = 300–600 MeV, and the emission angles of neutral pions in the ranges = $\theta _{\pi ^0 }^{c.m.} $ = 100°–140° and = $\theta _{\pi ^0 }^{c.m.} $ = 60°–65°, respectively. The experiment uses a hyperfine internal gas polarized target. Detectors of neutral pions and deuterons register these particles in coincidence. The target’s degree of polarization and luminosity is measured by detecting elastic electron-deuteron scattering at low momentum transfer. A selection of the preliminary results is presented.

The paper discusses the results of measurement for three components of tensor analyzing power for the reaction of incoherent [Formula: see text]-meson photoproduction on a deuteron within the proton energy range of 15–200[Formula: see text]MeV and the neutron energy range of 15–150[Formula: see text]MeV. The experiment was performed on the deuterium internal gas target of VEPP-3 electron accelerator using the protons and neutrons coincidence counting technique. The results of measurements of the tensor analyzing power’s components are compared with the results of statistical modeling performed within the frameworks of a theoretical model.

The progress in the field of thermonuclear fusion in the last years is very impressive. Lately, intensive discussions are concentrated on the application of polarized fuel for fusion, in order to maximize the efficiency of nuclear fuel utilization. At the moment the only sources of polarized hydrogen isotopes are sources of polarized atoms created for the use of nuclear physics experiments. The intensity of the best sources of polarized beams is less then \(10^{17}\) atoms \(\mathrm{s}^{-1}\) and limited by intrabeam scattering. This intensity is certainly not enough for tokamak reactor which requires at least \(10^{21}\) atoms \(\mathrm{s}^{-1}\). Here we discuss the possibility to obtain nuclear spin polarized molecules of hydrogen isotopes by their separation in a nonuniform magnetic field. Using the sources of molecules with large area it seems possible to overcome the limitations associated with intrabeam scattering and to obtain beams of polarized molecules of greater intensity in comparison with the atomic beam sources.

We report on the status of the Novosibirsk experiment on a precision measurement of the ratio $R$ of the elastic $e^+ p$ and $e^- p$ scattering cross sections. Such measurements determine the two-photon exchange effect in elastic electron-proton scattering. The experiment is conducted at the VEPP-3 storage ring using a hydrogen internal gas target. The ratio $R$ is measured with a beam energy of 1.6 GeV (electron/positron scattering angles are $\theta = 55 \div 75^{\circ}$ and $\theta = 15 \div 25^{\circ}$) and 1 GeV ($\theta = 65 \div 105^{\circ}$). We briefly describe the experimental method, paying special attention to the radiative corrections. Some preliminary results are presented., Comment: 5 pages, 6 figures and 1 table; contribution to the Proceedings of the PHIPSI11 Workshop (Novosibirsk, Russia, 19-22 September 2011)

At BINP the construction of the tagging system for almost-real photons (TS) is in progress. The energy of tagging photons can be up to 1.5 GeV. The projected energy resolution of TS is better then 1%. For at least a half of photons the linear polarization can be determined. The tagging system will extend the possibilities for photoreaction studying at VEPP-3 significantly. TS would allow to perform a complete kinematics reconstruction, thus permitting a reliable rejection of the background processes; to extend the measurements to higher photon energy; to enabling Σ-asymmetry measurements and double polarization experiments.

All three components of the tensor analyzing power for the reaction of [Formula: see text]-meson photoproduction on a deuteron have been measured in photon energy range of 280–500[Formula: see text]MeV and proton energy range of 15–70[Formula: see text]MeV. The experiment has been conducted on an internal tensor-polarized deuterium gas target of the VEPP-3 electron storage ring using the method of detecting two final protons in coincidence. Measured components of the tensor analyzing power have been compared with calculations results obtained within the framework of diagrammatic approach.

An overview of the recently completed, current, and planned experiments with internal targets at the VEPP-3 electron-positron storage ring in Novosibirsk is given. The results of the experiment to separately measure the deuteron form factors in elastic ed scattering in the range of momentum transfer Q 2 = 8−15 fm−2 are provided. The results of measuring the tensor analyzing power components of the tensor-polarized deuteron photodisintegration reaction in the range of γ-quantum energies E γ = 25−600 MeV are presented. The tensor analyzing powers of the coherent photoproduction of a neutral pion on a tensor-polarized deuteron have been measured for the first time. The almost-real photon tagging system being created is discussed. The status of the experiment under way to determine the contribution of two-photon exchange to the elastic ep scattering cross section is described.

The tensor asymmetry of exclusive π−-meson photoproduction on polarized deuterons was investigated. The T20 and T22 components of the reaction analyzing power contribute to the measured asymmetry. The detector made it possible to record two outgoing protons in coincidence in the range of polar angles θ1,2 = 44° − 88° and in the momentum range p1,2 = 350 − 700 MeV c−1. The measurements were performed at the VEPP-3 storage ring (Novosibirsk) using an internal target. The experimental results are compared with theoretical calculations.

We propose an experiment to search for a new gauge boson A' in $e^+e^-$ annihilation by means of a positron beam incident on a gas hydrogen target internal to the bypass at the VEPP-3 storage ring. The search method is based on a missing mass spectra in the reaction $e^+e^-\rightarrow \gamma$ A'. It allows observation of the A' signal independently of its decay modes and life time. The projected result of this experiment corresponds to an upper limit on the square of the coupling constant $\varepsilon^2=3\cdot 10^{-8}$ with a signal-to-noise ratio of two to one at an A' mass of 5-20 MeV., Comment: 20 pages, 17 figures

The components of the tensor analyzing powers, T20, T21, and T22, of the coherent photoproduction of a π0 meson on a deuteron have been measured for photon energies of 250–450 MeV and pion emission angles of 90°–145°. The results are compared with the theoretical predictions.

The ratio of the elastic ${e}^{+}p$ to ${e}^{\ensuremath{-}}p$ scattering cross sections has been measured precisely, allowing the determination of the two-photon exchange contribution to these processes. This neglected contribution is believed to be the cause of the discrepancy between the Rosenbluth and polarization transfer methods of measuring the proton electromagnetic form factors. The experiment was performed at the VEPP-3 storage ring at beam energies of 1.6 and 1.0 GeV and at lepton scattering angles between 15\ifmmode^\circ\else\textdegree\fi{} and 105\ifmmode^\circ\else\textdegree\fi{}. The data obtained show evidence of a significant two-photon exchange effect. The results are compared with several theoretical predictions.

A new method to determine the polarization of an electron beam circulating in a storage ring by a non-destructive way, based on measuring the asymmetry in scattering of beam electrons on electrons of the internal polarized gas jet target, has been developed and tested at the VEPP-3 storage ring.

The polarimeter for the internal tensor polarized deuterium gas target is described. Polarimeter is based on a target asymmetry measurement of elastic ed-scattering at a small momentum transfer. It was used in elastic and inelastic scattering experiments at VEPP-3 electron storage ring.

Analysis of the beam intensities from the atomic beam sources are reviewed. Formation of the free molecular flow is discussed in more detail. Suggested beam formation model may satisfactorily describe observed experimental data. A more detailed experimental investigation of the free molecular flow formation from the isentropic expansion would be very helpful for the optimization of the focusing magnet system of the polarized ABS to get the highest intensity of the beam.

The status of the design work on an electrostatic tandem-accelerator with vacuum insulation for 2.5 MeV protons and up to 40 mA constant current is reported. This machine is to be used for solving problems of neutron therapy and the detection of explosives by nuclear-resonance absorption of γ-rays.

The ratio of the elastic e(+)p to e(-)p scattering cross sections has been measured precisely, allowing the determination of the two-photon exchange contribution to these processes. This neglected contribution is believed to be the cause of the discrepancy between the Rosenbluth and polarization transfer methods of measuring the proton electromagnetic form factors. The experiment was performed at the VEPP-3 storage ring at beam energies of 1.6 and 1.0 GeV and at lepton scattering angles between 15° and 105°. The data obtained show evidence of a significant two-photon exchange effect. The results are compared with several theoretical predictions.

A precise comparison of the cross sections for the elastic scattering of electrons and positrons on protons was performed recently at the VEPP-3 storage ring in Novosibirsk, Russia. To provide the proposed accuracy, the energies of the electron and positron beams used during the experiment needed to be carefully maintained. This paper describes a special beam energy measurement system used in this experiment. This system is based on measuring the maximum energy of laser photons backscattered from electron and positron beams. It provides continuous beam energy measurements with a total relative uncertainty of less than $4.4 \cdot 10^{-5}$., 13 pages, 10 figures

We describe a precise measurement of the ratio of the ( e + p ) to ( e − p ) elastic scattering cross sections. This comparison is sensitive to the effect of two-photon exchange contributions which may be the cause for inconsistent extractions of the proton form factors obtained using different methods. The experiment was performed at storage ring VEPP–3, Novosibirsk at energies of positron/electron beams of 1.0 and 1.6 GeV with electron/positron scattering angles θ = 65÷105° for the first case and 15÷25° and 55÷75° for the second case. Details of the experiment and the preliminary results are presented.

This paper describes a new multipurpose event generator, ESEPP, which has been developed for the Monte Carlo simulation of unpolarized elastic scattering of charged leptons on protons. The generator takes into account the lowest-order QED radiative corrections to the Rosenbluth cross section including first-order bremsstrahlung without using the soft-photon or ultrarelativistic approximations. ESEPP can be useful for several significant ongoing and planned experiments., 28 pages, 5 figures, 2 tables