WorldWideScience

Sample records for antiprotonic helium atom

  1. Antiprotonic Helium Atoms

    OpenAIRE

    Kartavtsev, O. I.

    1995-01-01

    Metastable antiprotonic helium atoms $^{3,4}\\! H\\! e\\bar pe$ have been discovered recently in experiments of the delayed annihilation of antiprotons in helium media. These exotic atoms survive for an enormous time (about tens of microseconds) and carry the extremely large total angular momentum $L\\sim 30-40$. The theoretical treatment of the intrinsic properties of antiprotonic helium atoms, their formation and collisions with atoms and molecules is discussed.

  2. Capture of slow antiprotons by helium atoms

    OpenAIRE

    Revai, J.; Shevchenko, N.V.(Nuclear Physics Institute, Řež, 25068, Czech Republic)

    2004-01-01

    A consistent quantum mechanical calculation of partial cross-sections leading to different final states of antiprotonic helium atom was performed. For the four-body scattering wave function, corresponding to the initial state, as well as for the antiprotonic helium wave function, appearing in the final tate, adiabatic approximations was used. Calculations were carried out for a wide range of antiprotonic helium states and incident energies of the antiproton. Obtained energy dependances of som...

  3. Laser Spectroscopy of Antiprotonic Helium Atoms

    CERN Multimedia

    2002-01-01

    %PS205 %title\\\\ \\\\Following the discovery of metastable antiprotonic helium atoms ($\\overline{p}He^{+} $) at KEK in 1991, systematic studies of their properties were made at LEAR from 1991 to 1996. In the first two years the lifetime of $\\overline{p}He^{+}$ in liquid and gaseous helium at various temperatures and pressures was measured and the effect of foreign gases on the lifetime of these atoms was investigated. Effects were also discovered which gave the antiproton a 14\\% longer lifetime in $^4$He than in $^3$He, and resulted in important differences in the shape of the annihilation time spectra in the two isotopes.\\\\ \\\\Since 1993 laser spectroscopy of the metastable $\\overline{p}He^{+}$ atoms became the main focus of PS205. Transitions were stimulated between metastable and non-metastable states of the $\\overline{p}He^{+}$ atom by firing a pulsed dye laser beam into the helium target every time an identified metastable atom was present (Figure 1). If the laser frequency matched the transition energy, the...

  4. Antiprotonic helium

    CERN Multimedia

    Eades, John

    2005-01-01

    An exotic atom in w hich an electron and an antiproton orbit a helium nucleus could reveal if there are any differences between matter and antimatter. The author describes this unusual mirror on the antiworld (5 pages)

  5. The ASACUSA experiment at CERN's AD antiproton decelerator catches antiprotons in helium, where the antiprotons replace electrons, giving exotics atoms.

    CERN Multimedia

    Loïez, P

    2000-01-01

    Photo 03: Laser beams are prepared for shooting at antiprotonic helium atoms. Left to right: Masaki Hori (Tokyo University) and John Eades (CERN). Photo 01: Dye laser triggered by "YAG" laser. Photo 02: Masaki Hori adjusting optical system of laser beams.

  6. Primary population of antiprotonic helium states

    OpenAIRE

    Révai, J.; Shevchenko, N.V.(Nuclear Physics Institute, Řež, 25068, Czech Republic)

    2003-01-01

    A full quantum mechanical calculation of partial cross-sections leading to different final states of antiprotonic helium atom was performed. Calculations were carried out for a wide range of antiprotonic helium states and incident (lab) energies of the antiproton.

  7. Laser spectroscopy of the antiprotonic helium atom – its energy levels and state lifetimes

    CERN Document Server

    Hidetoshi, Yamaguchi

    2003-01-01

    The antiprotonic atom is a three-body exotic system consisting of an antiproton, an electron and a helium nucleus. Its surprising longevity was found and has been studied for more than 10 years. In this work, transition energies and lifetimes of this exotic atom were systematically studied by using the antiproton beam of AD(Antiproton Decelerator) facility at CERN, with an RFQ antiproton decelerator, a narrow-bandwidth laser, Cerenkov counters with fast-response photomultiplier tubes, and cryogenic helium target systems. Thirteen transition energies were determined with precisions of better than 200 ppb by a laser spectroscopy method, together with the elimination of the shift effect caused by collisions with surrounding atoms. Fifteen lifetimes (decay rates) of short-lived states were determined from the time distributions of the antiproton-annihilation signals and the resonance widths of the atomic spectral lines. The relation between the magnitude of the decay rates and the transition multipolarity was inv...

  8. Shift and broadening of resonance lines of the antiprotonic helium atoms in liquid He-4

    OpenAIRE

    Adamczak, Andrzej; Bakalov, Dimitar

    2013-01-01

    The shift and broadening of the resonance lines in spectrum of the antiprotonic helium atoms $\\bar{p}\\mathrm{He}^{+}$ located in fluid and superfluid $^4$He have been calculated. The contributions to the shift and broadening from collective degrees of freedom in liquid $^4$He have been estimated using the phenomenological response function. Effects due to the interaction of $\\bar{p}\\mathrm{He}^{+}$ with a single $^4$He atom have been calculated in the quasistatic approximation using the exper...

  9. Effect of static electric field on cross sections in antiproton impact ionization of atomic helium

    International Nuclear Information System (INIS)

    We report the effect of static electric fields in different geometrical features on the collisional ionization of helium atoms by antiproton. The Classical Trajectory Monte Carlo (CTMC) method with a model interaction potential has been used to simulate the differential and total ionization cross sections in antiproton–helium atom collisions in the energy range of 10–500 keV with and without electric fields. The calculated ionization cross sections are in reasonable agreement with the recently reported experimental and theoretical results. The effects of the external electric fields are seen to be quite prominent.

  10. Antiprotonic helium atomcules

    Directory of Open Access Journals (Sweden)

    Sauge Sébastien

    2012-10-01

    Full Text Available About 3% of antiprotons ( stopped in helium are long-lived with microsecond lifetimes, against picoseconds in all other materials. This unusual longevity has been ascribed to the trapping of on metastable bound states in He+ helium atom-molecules thus named atomcules. Apart from their unique dual structure investigated by laser spectroscopy – a near-circular quasi-classical Rydberg atom with l ~ n – 1 ~ 37 or a special diatomic molecule with a negatively charged nucleus in high rotational state with J = l – the chemical physics aspects of their interaction with other atoms or molecules constitute an interesting topic for molecular physics. While atomcules may resist to million collisions in helium, molecular contaminants such as H2 are likely to destroy them in a single one, down to very low temperatures. In the Born-Oppenheimer framework, we interpret the molecular interaction obtained by ab initio quantum chemical calculations in terms of classical reactive channels, with activation barriers accounting for the experiments carried out in He and H2. From classical trajectory Monte Carlo simulations, we show that the thermalization stage strongly quenches initial populations, thus reduced to a recovered 3 % trapping fraction. This work illustrates the pertinence of chemical physics concepts to the study of exotic processes involving antimatter. New insights into the physico-chemistry of cold interstellar radicals are anticipated.

  11. Atomic approaches in metastable antiprotonic helium atoms. REPLY to 'analysis of the lifetimes and fractions of antiprotons trapped in metastable antiprotonic-helium states' by I. Shimamura and M. Kimura

    International Nuclear Information System (INIS)

    In the present note the authors clarify the purpose of YO and complement its essential points, thus showing that the criticisms of SK are inappropriate. The paper YO [1] was aimed at discussing some new aspects related to the metastability of hadronic helium atoms which had been discovered when negative kaons [2], negative pions [3] and antiprotons [4] were stopped in liquid helium. The delayed fraction, time spectrum shape and lifetimes were the observables. Further experimental studies are in progress [5], and as of today there is no successful explanation for these interesting phenomena. So, YO tried to give brief and rather qualitative estimates for the observations in an intuitive way, considering only the leading terms. The following problems are discussed in as simple a manner as possible, starting from the exotic-atom viewpoints of Condo [6] and Russell [7]: i)the atomic core polarization effect, ii)the structure and radiative lifetimes, iii)the non-statistical distribution of the angular momentum and an estimate of the delayed fraction, and iv)the isotope effect, though the title represents only i). To respond to the comments of SK, it is important to consider the correspondence between the atomic approach and the molecular approach for the metastable antiprotonic helium atom of Condo-Russell. We therefore begin this note with a discussion of this aspect. (author)

  12. Isotope Effects on Delayed Annihilation Time Spectra of Antiprotonic Helium Atoms in Low-Temperature Gas

    CERN Document Server

    Ketzer, B; Daniel, H; Von Egidy, T; Niestroj, A; Schmid, S; Schmid, W; Yamazaki, T; Sugai, I; Nakayoshi, K; Hayano, R S; Maas, F E; Torii, H A; Ishikawa, T; Tamura, H; Morita, N; Horváth, D; Eades, John; Widmann, E

    1996-01-01

    The delayed annihilation time spectra (DATS) of antiprotonic helium atoms have been studied in isotopically pure low temperature ^3He and ^4He gas at various densities. The DATS taken at 5.8~K and 400~mbar are very similar in shape except for i) a small difference in the time scale and ii) the presence of a distinct fast decay component in the case of ^3He. The ratio of overall trapping times (mean lifetimes against annihilation), R = T_{\\mathrm{trap}}(\\mbox{^{4}He})/T_{\\mathrm{trap}}(\\mbox{^{3}He}), has been determined to be 1.144 \\pm 0.009, which is in good agreement with a theoretical estimate yielding R = [(M^*(\\mbox{\\overline{\\mathrm{p}}}\\mbox{^{4}He})/ M^*(\\mbox{\\overline{ \\mathrm{p}}}\\mbox{^{3}He})]^2=1.14, where M^* denotes the reduced mass of the \\mbox{\\overline{\\mathrm{p}}}\\mbox{He^{++}}\\ system. The presence of a short-lived component with a lifetime of (0.154\\pm 0.007)\\ \\mbox{\\mus} in the case of \\mbox{^{3}He}\\ suggests that the \\mbox{\\overline{\\mathrm{p}}}\\mbox{^{3}He^{+}}\\ atom has a state of in...

  13. Laser spectroscopy of antiprotonic helium and pionic helium

    International Nuclear Information System (INIS)

    ASACUSA (Atomic Spectroscopy and Collisions Using Slow Antiproton) experiment of CERN has observed two-photon spectroscopy by making non-linear transitions of the antiprotons which have occupied highly excited levels. The metastable antiproton helium atoms are studied by irradiating two laser light photons propagating in the counter direction. As the result, the spectrum of narrow line width was observed by making the Doppler width of the resonant transition to decrease. And the anti-proton helium transition frequency was measured with the accuracy of (2.3∼5) X10-9. The mass ratio of the antiproton and the electron has been decided to be Mp/me =1836.152674(23) from the comparison of quantum electrodynamics calculation and the present experimental result. The pion-Helium experiment instrument has been also constructed at the ring cyclotron of PSI (Paul Sherer Institute) toward the successful laser spectroscopy of this atom. When this atom is observed, the π- mass can be obtained with the accuracy higher than 6∼8 orders of magnitude which may contribute to the direct measurement of the upper limit value of muon neutrino mass in the Particle Data Book Mass although various difficulties may be encountered. This report describes briefly the laser spectroscopy at first and then the recent situation of the experiments. (S. Funahashi)

  14. Antiprotonic-hydrogen atoms

    International Nuclear Information System (INIS)

    Experimental studies of antiprotonic-hydrogen atoms have recently made great progress following the commissioning of the low energy antiproton facility (LEAR) at CERN in 1983. At the same time our understanding of the atomic cascade has increased considerably through measurements of the X-ray spectra. The life history of the p-bar-p atom is considered in some detail, from the initial capture of the antiproton when stopping in hydrogen, through the atomic cascade with the emission of X-rays, to the final antiproton annihilation and production of mesons. The experiments carried out at LEAR are described and the results compared with atomic cascade calculations and predictions of strong interaction effects. (author)

  15. Isotope effects on delayed annihilation time spectra of antiprotonic helium atoms in a low-temperature gas

    International Nuclear Information System (INIS)

    The delayed annihilation time spectra (DATS) of antiprotonic helium atoms have been studied in isotopically pure low-temperature 3He and 4He gas at various densities. The DATS taken at 5.8 K and 400 mbar are very similar in shape except for (i) a small difference in the time scale and (ii) the presence of a distinct fast decay component in the case of 3He. The ratio of overall trapping times (mean lifetimes against annihilation), R=Ttrap(4He)/Ttrap(3He), has been determined to be 1.144 ± 0.009, which is in good agreement with a theoretical estimate yielding R=[M*(bar p4He)/ M*(bar p3He)]2=1.14, where M* denotes the reduced mass of the bar pHe2+system. The presence of a short-lived component with a lifetime of 0.154±0.007μs in the case of 3He suggests that the bar p3He+atom has a state of intermediate lifetime on the border between a metastable zone and an Auger-dominated short-lived zone. The fraction of antiprotons trapped in metastable states at 5.8 K and 400 mbar is lower by 22.2(4)% for 3Hethan for 4He. All the data can be fitted fairly well with simple three-level and four-level cascade models. copyright 1996 The American Physical Society

  16. Isotope effects on delayed annihilation time spectra of antiprotonic helium atoms in a low-temperature gas

    Science.gov (United States)

    Ketzer, B.; Hartmann, F. J.; Daniel, H.; von Egidy, T.; Niestroj, A.; Schmid, S.; Schmid, W.; Yamazaki, T.; Sugai, I.; Nakayoshi, K.; Hayano, R. S.; Maas, F. E.; Torii, H. A.; Ishikawa, T.; Tamura, H.; Morita, N.; Horváth, D.; Eades, J.; Widmann, E.

    1996-04-01

    The delayed annihilation time spectra (DATS) of antiprotonic helium atoms have been studied in isotopically pure low-temperature 3He and 4He gas at various densities. The DATS taken at 5.8 K and 400 mbar are very similar in shape except for (i) a small difference in the time scale and (ii) the presence of a distinct fast decay component in the case of 3He. The ratio of overall trapping times (mean lifetimes against annihilation), R=Ttrap(4He)/Ttrap(3He), has been determined to be 1.144 +/- 0.009, which is in good agreement with a theoretical estimate yielding R=[M*(p¯ 4He)/ M*(p¯ 3He)]2=1.14, where M* denotes the reduced mass of the p¯He2+system. The presence of a short-lived component with a lifetime of 0.154+/-0.007 μs in the case of 3He suggests that the p¯ 3He+atom has a state of intermediate lifetime on the border between a metastable zone and an Auger-dominated short-lived zone. The fraction of antiprotons trapped in metastable states at 5.8 K and 400 mbar is lower by 22.2(4)% for 3than for 4He. All the data can be fitted fairly well with simple three-level and four-level cascade models.

  17. Nuclear Excitations by Antiprotons and Antiprotonic Atoms

    CERN Multimedia

    2002-01-01

    The proposal aims at the investigation of nuclear excitations following the absorption and annihilation of stopped antiprotons in heavier nuclei and at the same time at the study of the properties of antiprotonic atoms. The experimental arrangement will consist of a scintillation counter telescope for the low momentum antiproton beam from LEAR, a beam degrader, a pion multiplicity counter, a monoisotopic target and Ge detectors for radiation and charged particles. The data are stored by an on-line computer.\\\\ \\\\ The Ge detectors register antiprotonic x-rays and nuclear @g-rays which are used to identify the residual nucleus and its excitation and spin state. Coincidences between the two detectors will indicate from which quantum state the antiprotons are absorbed and to which nuclear states the various reactions are leading. The measured pion multiplicity characterizes the annihilation process. Ge&hyphn. and Si-telescopes identify charged particles and determine their energies.\\\\ \\\\ The experiment will gi...

  18. Prospects of CPT tests using antiprotonic helium and antihydrogen

    International Nuclear Information System (INIS)

    Testing CPT to the highest possible precision using the laser spectroscopy of antiprotonic helium atoms (a neutral three-body system consisting of an antiproton, a helium nucleus and an electron) is the current goal of ASACUSA collaboration at CERN AD. The present status and future prospects are discussed in the first half of the talk. Our program will be extended in the future to include the microwave spectroscopy of ground-state hyperfine splitting of antihydrogen. The physics motivations and possible measurement schemes are presented in the second half

  19. Atomic Spectroscopy and Collisions Using Slow Antiprotons \\\\ ASACUSA Collaboration

    CERN Multimedia

    Matsuda, Y; Lodi-rizzini, E; Kuroda, N; Schettino, G; Hori, M; Soter, A; Pirkl, W; Mascagna, V; Malbrunot, C L S; Yamazaki, Y; Eades, J; Simon, M; Massiczek, O; Sauerzopf, C; Breuker, H; Nagata, Y; Uggerhoj, U I; Mc cullough, R W; Toekesi, K M; Venturelli, L; Widmann, E; Zmeskal, J; Kanai, Y; Hayano, R; Knudsen, H; Kristiansen, H; Todoroki, K; Bartel, M A; Moller, S P; Charlton, M; Leali, M; Diermaier, M; Kolbinger, B

    2002-01-01

    ASACUSA (\\underline{A}tomic \\underline{S}pectroscopy \\underline{A}nd \\underline{C}ollisions \\underline{U}sing \\underline{S}low \\underline{A}ntiprotons) is a collaboration between a number of Japanese and European research institutions, with the goal of studying bound and continuum states of antiprotons with simple atoms.\\\\ Three phases of experimentation are planned for ASACUSA. In the first phase, we use the direct $\\overline{p}$ beam from AD at 5.3 MeV and concentrate on the laser and microwave spectroscopy of the metastable antiprotonic helium atom, $\\overline{p}$He$^+$, consisting of an electron and antiproton bound by the Coulomb force to the helium nucleus. Samples of these are readily created by bringing AD antiproton beam bunches to rest in helium gas. With the help of techniques developed at LEAR for resonating high precision laser beams with antiproton transitions in these atoms, ASACUSA achieved several of these first-phase objectives during a few short months of AD operation in 2000. Six atomic tr...

  20. Production of ultra slow antiprotons, its application to atomic collisions and atomic spectroscopy - ASACUSA project

    International Nuclear Information System (INIS)

    The Atomic Spectroscopy And Collisions Using Slow Antiprotons (ASACUSA) project aims at studying collision dynamics with slow antiprotons and high precision spectroscopy of antiprotonic atoms. To realize these purposes, the production of high quality ultra slow antiproton beams is essential, which is achieved by the combination of antiproton decelerator (AD) from 3 GeV to 5 MeV, a radio frequency quadrupole (RFQ) decelerator from 5 MeV to 50 keV, and finally an electromagnetic trap from 50 keV to 10 eV. From the atomic physics point of view, an antiproton is an extremely heavy electron and/or a negatively charged proton, i.e., the antiproton is a unique tool to shed light on collision dynamics from the other side of the world. In addition to this fundamentally important feature, the antiproton has also a big practical advantage, i.e., it annihilates with the target nuclei emitting several energetic pions, which provides high detection efficiency with very good time resolution. Many-body effects which are of great importance to several branches of science will be studied through ionization and antiprotonic atom formation processes under single collision conditions. Various antiprotonic atoms including protonium (p anti-p) are expected to be meta-stable in vacuum, which is never true for those in dense media except for antiprotonic helium. High precision spectroscopy of protonium will for the first time become feasible benefited by this meta-stability. The present review reports briefly the production scheme of ultra slow antiproton beams and several topics proposed in the ASACUSA project

  1. Antiproton trapping in various helium media: report of the HELIUMTRAP experiment at LEAR

    International Nuclear Information System (INIS)

    HELIUMTRAP (PS205) investigates the recently discovered anomalously long-lived states of antiprotons in various helium media. An overview is given of experiments stopping antiprotons in several phases of helium performed at LEAR in the last two years. (author)

  2. Delayed annihilation of antiprotons in helium gas

    International Nuclear Information System (INIS)

    The delayed annihilation of antiprotons, which was recently discovered in liquid 4He at KEK, has been studied at CERN in gas-phase 4He and 3He. The annihilation time spectra in gas 4He at various pressures were found to be similar to that for liquid 4He. The observed average lifetime in the region t > 1μsec for 3 atm 4He was about 3.2μsec, while for 3 atm 3He gas it was 2.8μsec, i.e. shorter by 15 %. The time spectra show a growth-decay type function, which is indicative of the presence of a series of metastable states. For 4He and 3He they have nearly identical shapes, differing only in the time scale by 14 ± 3 %. These observations are qualitatively consistent with the atomic model of p-bare-He++ proposed by Condo. The time spectra were found to be sensitive to the presence of small amounts (as small as 20 ppm) of H2. No evidence was seen for delayed annihilation in gaseous Ne. 36.10. (author)

  3. Method for laser spectroscopy of metastable pionic helium atoms

    International Nuclear Information System (INIS)

    The PiHe collaboration is currently attempting to carry out laser spectroscopy of metastable pionic helium atoms using the high-intensity π− beam of the ring cyclotron facility of the Paul Scherrer Institute. These atoms are heretofore hypothetical three-body Coulomb systems each composed of a helium nucleus, a π− occupying a Rydberg state, and an electron occupying the 1s ground state. We briefly review the proposed method by which we intend to detect the laser spectroscopic signal. This complements our experiments on metastable antiprotonic helium atoms at CERN

  4. Calculation of transition probabilities and ac Stark shifts in two-photon laser transitions of antiprotonic helium

    OpenAIRE

    HORI, MASAKI; Korobov, Vladimir I.

    2010-01-01

    Numerical ab initio variational calculations of the transition probabilities and ac Stark shifts in two-photon transitions of antiprotonic helium atoms driven by two counter-propagating laser beams are presented. We found that sub-Doppler spectroscopy is in principle possible by exciting transitions of the type (n,L)->(n-2,L-2) between antiprotonic states of principal and angular momentum quantum numbers n~L-1~35, first by using highly monochromatic, nanosecond laser beams of intensities 10^4...

  5. A new cryogenic target and microwave cavity for hyperfine structure spectroscopy of antiprotonic helium

    International Nuclear Information System (INIS)

    Full text: A new cryostat with pulse tube refrigeration and gas-tight microwave cavity with a laser and antiproton window has been designed and built to study the hyperfine structure of antiprotonic helium-3. The improvements between this and the old system will be explained. (author)

  6. Meas.of the Ratio Between Double and Single Ionization of Helium for Antiprotons

    CERN Multimedia

    2002-01-01

    The aim of this experiment is to measure the ratio between double and single ionization of helium by antiprotons in the energy range $>$~3~MeV. Comparison with already existing proton data will yield information on the mechanisms for double ionization, which could not be extracted from previous comparisons between ratios measured for equivelocity electrons and protons. The most basic information to be obtained from an antiproton experiment will be the amount of correlation existing between the two electrons in the ground-state helium atom.\\\\ \\\\ The equipment consists of a gas cell, which employs slow-ion collection via the so-called condenser-plate method for the absolute sum of partial-ionization cross sections and determination of the relative contribution of multiple charged ions by TOF. The gas cell has movable entrance and exit slits and a grid system to account for secondary emission from the collection of slow ions. Together with a field of 800~V/cm in the collision region, the potentials of the TOF sp...

  7. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures thereof

  8. Low-energy collisions of antiprotons with atoms and molecules

    International Nuclear Information System (INIS)

    Time-dependent close-coupling calculations were performed using the impact parameter method for antiproton and proton collisions with alkali-metal atoms and hydrogen molecules. The targets are described as effective one-electron systems using appropriate model potentials. The proton data verify the employed method while the results for antiprotons improve the literature on these systems considerably. Cross sections for ionization and excitation as well as electron-energy spectra and stopping power will be presented.

  9. Atomic spectra in a helium bubble

    OpenAIRE

    Nakatsukasa, Takashi; Yabana, Kazuhiro; Bertsch, George F.

    2002-01-01

    Density functional theory (DFT) is applied to atomic spectra under perturbations of superfluid liquid helium. The atomic DFT of helium is used to obtain the distribution of helium atoms around the impurity atom, and the electronic DFT is applied to the excitations of the atom, averaging over the ensemble of helium configurations. The shift and broadening of the D1 and D2 absorption lines are quite well reproduced by theory, suggesting that the DFT may be useful for describing spectral perturb...

  10. Precision spectroscopy of the helium atom

    Institute of Scientific and Technical Information of China (English)

    Shui-ming HU; Zheng-Tian LU; Zong-Chao YAN

    2009-01-01

    Persistent efforts in both theory and experiment have yielded increasingly precise understanding of the helium atom. Because of its simplicity, the helium atom has long been a testing ground for relativistic and quantum electrodynamic effects in few-body atomic systems theoretically and experimentally.Comparison between theory and experiment of the helium spectroscopy in ls2p3pJ can potentially extract a very precise value of the fine structure constant a. The helium atom can also be used to explore exotic nuclear structures. In this paper, we provide a brief review of the recent advances in precision calculations and measurements of the helium atom.

  11. Helium atom scattering from surfaces

    CERN Document Server

    1992-01-01

    High resolution helium atom scattering can be applied to study a number of interesting properties of solid surfaces with great sensitivity and accuracy. This book treats in detail experimental and theoretical aspects ofthis method as well as all current applications in surface science. The individual chapters - all written by experts in the field - are devoted to the investigation of surface structure, defect shapes and concentrations, the interaction potential, collective and localized surface vibrations at low energies, phase transitions and surface diffusion. Over the past decade helium atom scattering has gained widespread recognitionwithin the surface science community. Points in its favour are comprehensiveunderstanding of the scattering theory and the availability of well-tested approximation to the rigorous theory. This book will be invaluable to surface scientists wishing to make an informed judgement on the actual and potential capabilities of this technique and its results.

  12. ASACUSA hits antiproton jackpot

    CERN Multimedia

    2001-01-01

    The Japanese-European ASACUSA collaboration, which takes its name from the oldest district of Tokyo, approaches the antimatter enigma in a different way from the other two AD experiments, by inserting antiprotons into ordinary atoms. Last month the collaboration succeeded in trapping about a million antiprotons. The ASACUSA antiproton trap (lower cylinder), surmounted by its liquid helium reservoir. Looking on are Ken Yoshiki-Franzen, Zhigang Wang, Takahito Tasaki, Suzanne Reed, John Eades, Masaki Hori, Yasunori Yamazaki, Naofumi Kuroda, Jun Sakaguchi, Berti Juhasz, Eberhard Widmann and Ryu Hayano. A key element of the ASACUSA apparatus is its decelerating Radiofrequency Quadrupole magnet, RFQD. After tests with protons in Aarhus, this was installed in ASACUSA's antiproton beam last October (Bulletin 41/2000, 9 October 2000). Constructed by Werner Pirkl's group in PS Division, the RFQD works by applying an electric field to the AD antiproton pulse the opposite direction to its motion. As the antiprotons slo...

  13. Trapping fermionic and bosonic helium atoms

    OpenAIRE

    Stas, R. J. W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures thereof-are cooled to a temperature around 1 mK and form the starting point of the presented studies. The studies include an investigation of cold ionizing collisions in the absence of resonant light, an i...

  14. Ionization of atomic hydrogen by 30 1000 keV antiprotons

    Energy Technology Data Exchange (ETDEWEB)

    Knudsen, H.; Mikkelsen, U.; Paludan, K. [Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Kirsebom, K.; Moller, S.P.; Uggerhoj, E. [Institute for Synchrotron Radiation, University of Aarhus, DK-8000 Aarhus C (Denmark); Slevin, J. [Department of Experimental Physics, St. Patrick`s College, Maynooth (Ireland); Charlton, M. [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Morenzoni, E. [Paul Scherrer Institut, Villigen, CH-4234 (Switzerland)

    1995-06-05

    Ionization in collisions between antiprotons and atomic hydrogen is perhaps the least complicated and most fundamental process that can be treated by atomic-collision theory. We present measurements of the ionization cross section for 30--1000 keV antiprotons colliding with atomic hydrogen.

  15. Antiprotons

    Science.gov (United States)

    Chamberlain, Owen; Segre, Emilio; Wiegand, Clyde

    1955-11-29

    Since the development of Dirac's theory of the electron and the brilliant confirmation of one of its most startling predictions by the discovery of the positron by Anderson, it has been assumed most likely that the proton would also have its charge conjugate, the antiproton. The properties that define the antiproton are: (a) charge equal to the electron charge (also in sign); (b) mass equal to the proton mass; (c) stability against spontaneous decay; (d) ability to annihilate by interaction with a proton or neutron, probably generating pions and releasing in some manner the energy 2 mc{sup 2}; (e) generation in pairs with ordinary nucleons; (f) magnetic moment equal but opposite to that of the proton; (g) fermion of spin 1/2. Not all these properties are independent, but all might ultimately be subjected to experiment.

  16. Calculation of transition probabilities and ac Stark shifts in two-photon laser transitions of antiprotonic helium

    International Nuclear Information System (INIS)

    Numerical ab initio variational calculations of the transition probabilities and ac Stark shifts in two-photon transitions of antiprotonic helium atoms driven by two counter-propagating laser beams are presented. We found that sub-Doppler spectroscopy is, in principle, possible by exciting transitions of the type (n,L)→(n-2,L-2) between antiprotonic states of principal and angular momentum quantum numbers n∼L-1∼35, first by using highly monochromatic, nanosecond laser beams of intensities 104-105 W/cm2, and then by tuning the virtual intermediate state close (e.g., within 10-20 GHz) to the real state (n-1,L-1) to enhance the nonlinear transition probability. We expect that ac Stark shifts of a few MHz or more will become an important source of systematic error at fractional precisions of better than a few parts in 109. These shifts can, in principle, be minimized and even canceled by selecting an optimum combination of laser intensities and frequencies. We simulated the resonance profiles of some two-photon transitions in the regions n=30-40 of the p4He+ and p3He+ isotopes to find the best conditions that would allow this.

  17. Current status of antiproton impact ionization of atoms and molecules: theoretical and experimental perspectives

    DEFF Research Database (Denmark)

    Kirchner, Tom; Knudsen, Helge

    2011-01-01

    Experimental and theoretical progress in the field of antiproton-impact-induced ionization of atoms and molecules is reviewed. We describe the techniques used to measure ionization cross sections and give an overview of the experimental results supplemented by tables of all existing data. An...... status of our understanding of antiproton impact ionization. The related issues of energy loss measurements and antiproton therapy are briefly described and directions for possible future work are pointed out as well....

  18. Ionization of helium by slow antiproton impact: total and differential cross sections

    CERN Document Server

    Borbély, S; Nagele, S; Tőkési, K; Nagy, L; Burgdörfer, J

    2014-01-01

    We theoretically investigate the single and double ionization of the He atom by antiproton impact for projectile energies ranging from $3$~keV up to $1000$~keV. We obtain accurate total cross sections by directly solving the fully correlated two-electron time-dependent Schr\\"odinger equation and by performing classical trajectory Monte-Carlo calculations. The obtained quantum-mechanical results are in excellent agreement with the available experimental data. Along with the total cross sections, we also present the first fully \\textit{ab initio} doubly differential data for single ionization at 10 and 100~keV impact energies. In these differential cross sections we identify the binary-encounter peak along with the anticusp minimum. Furthermore, we also point out the importance of the post-collisional electron-projectile interaction at low antiproton energies which significantly suppresses electron emission in the forward direction.

  19. Photoassociation of cold metastable helium atoms

    NARCIS (Netherlands)

    Woestenenk, G.R.

    2001-01-01

    During the last decades the study of cold atoms has grown in a great measure. Research in this field has been made possible due to the development of laser cooling and trapping techniques. We use laser cooling to cool helium atoms down to a temperature of 1 mK and we are able to tr

  20. Interaction of antiprotons with Rb atoms and a comparison of antiproton stopping powers of the atoms H, Li, Na, K, and Rb

    DEFF Research Database (Denmark)

    Lühr, Armin Christian; Fischer, Nicolas; Saenz, Alejandro

    Ionization and excitation cross sections as well as electron-energy spectra and stopping powers of the alkali metal atoms Li, Na, K, and Rb colliding with antiprotons were calculated using a time-dependent channel-coupling approach. An impact-energy range from 0.25 to 4000 keV was considered. The...... target atoms are treated as effective one-electron systems using a model potential. The results are compared with calculated cross sections for antiproton-hydrogen atom collisions....

  1. Forbidden transitions in the helium atom

    CERN Document Server

    Lach, G; Lach, Grzegorz; Pachucki, Krzysztof

    2001-01-01

    Nonrelativistically forbidden, single-photon transition rates between low lying states of the helium atom are rigorously derived within quantum electrodynamics theory. Equivalence of velocity and length gauges, including relativistic corrections is explicitly demonstrated. Numerical calculations of matrix elements are performed with the use of high precision variational wave functions and compared to former results.

  2. Comparison of single-electron removal processes in collisions of electrons, positrons, protons, and antiprotons with hydrogen and helium

    International Nuclear Information System (INIS)

    We present and compare total cross sections for single-electron removal in collisions of electrons, positrons, protons, and antiprotons with atomic hydrogen and helium. These cross sections have been calculated using the classical trajectory Monte Carlo technique in the velocity range of 0.5--7.0 a.u. (6.25--1224 keV/u). The cross sections are compared at equal collision velocities and exhibit differences arising from variations in mass and sign of charge of the projectile. At low and intermediate velocities these differences are large in both the ionization and charge transfer channels. At high velocities the single-ionization cross section for each of these singly charged particles becomes equal. However, the differences in the single-charge-transfer cross sections for positron and proton impact persist to very large velocities. We extend our previous work [Phys. Rev. A 38, 1866 (1988)] to explain these mass and sign of the charge effects in single-electron removal collisions

  3. A naturally occurring trap for antiprotons

    International Nuclear Information System (INIS)

    The phenomenon of delayed annihilation of antiprotons in helium is the first instance of a naturally occurring trap for antimatter in ordinary matter. Recent studies of this effect at CERN are summarized, and plans are described for laser excitation experiments to test its interpretation in terms of metastable exotic helium atom formation. (author)

  4. High precision spectroscopy of pionic and antiprotonic atoms; Spectroscopie de precision des atomes pioniques et antiprotoniques

    Energy Technology Data Exchange (ETDEWEB)

    El-Khoury, P

    1998-04-15

    The study of exotic atoms, in which an orbiting electron of a normal atom is replaced by a negatively charged particle ({pi}{sup -}, {mu}{sup -}, p, {kappa}{sup -}, {sigma}{sup -},...) may provide information on the orbiting particle and the atomic nucleus, as well as on their interaction. In this work, we were interested in pionic atoms ({pi}{sup -14} N) on the one hand in order to determine the pion mass with high accuracy (4 ppm), and on the other hand in antiprotonic atoms (pp-bar) in order to study the strong nucleon-antinucleon interaction at threshold. In this respect, a high-resolution crystal spectrometer was coupled to a cyclotron trap which provides a high stop density for particles in gas targets at low pressure. Using curved crystals, an extended X-ray source could be imaged onto the detector. Charge-Coupled Devices were used as position sensitive detectors in order to measure the Bragg angle of the transition to a high precision. The use of gas targets resolved the ambiguity owing to the number of K electrons for the value of the pion mass, and, for the first time, strong interaction shift and broadening of the 2p level in antiprotonic hydrogen were measured directly. (author)

  5. Neutral atom lithography with metastable helium

    Science.gov (United States)

    Allred, Claire Shean

    In this dissertation we describe our performance of resist assisted neutral atom lithography using a bright beam of metastable 23S1 Helium (He*). Metastable Helium atoms have 20 eV of internal energy making them easy to detect and able to destroy a resist. The He* is produced by a reverse flow DC discharge source and then collimated with the bichromatic force, followed by three optical molasses velocity compression stages. The atoms in the resulting beam have a mean longitudinal velocity of 1125 m/s and a divergence of 1.1 mrad. The typical beam flux is 2 x 109 atoms/mm2s through a 0.1mm diameter aperture 70 cm away from the source. The internal energy of the atoms damages the molecules of a self assembled monolayer (SAM) of nonanethiol. The undisturbed SAM protects a 200 A layer of gold that has been evaporated onto a prepared Silicon wafer from a wet chemical etch. Two methods are used to pattern the He* atoms before they destroy the SAM. First, a Nickel micro mesh was used to protect the SAM. These experiments established an appropriate dosage and etch time for patterning. The samples were analyzed with an atomic force microscope and found to have an edge resolution of 63 nm. Then, patterning was accomplished using the dipole force the atoms experience while traversing a standing wave of lambda = 1083nm light tuned 500MHz below the 23S 1 → 23P2 transition. Depending on the intensity of the light, the He* atoms are focused or channeled into lines separated by lambda/2. The lines cover the entire exposed length of the substrate, about 3 mm. They are about 3 mm long, corresponding to about twice the beam waist of the laser standing wave. Thus there are 6 x 10 3 lines of length 5500lambda. These results agree with our numerical simulations of the experiment.

  6. Diffusion behaviors of helium atoms at two Pd grain boundaries

    Institute of Scientific and Technical Information of China (English)

    XIA Ji-xing; HU Wang-yu; YANG Jian-yu; AO Bing-yun

    2006-01-01

    The diffusion behaviors of helium atoms at two symmetric grain boundaries (Σ5{210} and Σ3 {112}) of Pd were investigated using molecular dynamics simulations through an analytical embedded-atom method(MAEAM) model. The simulations demonstrate that the interstitial helium atoms are easily trapped at the grain boundaries and precipitated into clusters. Due to the closed-shell electronic configurations of both helium and palladium,Pd grain boundaries yield strong capability of retaining helium atoms. By calculating the mean square displacements(MSD) of an interstitial helium atom at the grain boundaries,the diffusion coefficients were determined,and the linear fits to Arrhenius relation. The diffusion activation energies of interstitial helium atom at these two Pd grain boundaries were also evaluated.

  7. Neutron density distributions from antiprotonic 208Pb and 209Bi atoms

    OpenAIRE

    Klos, B.; Trzcinska, A.; Jastrzebski, J.; Czosnyka, T.; Kisielinski, M.; Lubinski, P.; Napiorkowski, P.; Pienkowski, L.; Hartmann, F. J.; Ketzer, B.; Ring, P.; Schmidt, R.; von Egidy, T.; Smolanczuk, R.; S. Wycech

    2007-01-01

    The X-ray cascade from antiprotonic atoms was studied for 208Pb and 209Bi. Widths and shifts of the levels due to the strong interaction were determined. Using modern antiproton-nucleus optical potentials the neutron densities in the nuclear periphery were deduced. Assuming two parameter Fermi distributions (2pF) describing the proton and neutron densities the neutron rms radii were deduced for both nuclei. The difference of neutron and proton rms radii /\\r_np equal to 0.16 +-(0.02)_{stat} +-...

  8. Precision Measurement of the Energies and Line Shapes of Antiprotonic Lyman and Balmer Transitions From Hydrogen and Helium Isotopes

    CERN Multimedia

    2002-01-01

    % PS207 \\\\ \\\\ For the study of the antiproton-proton and antiproton-nuclear spin-spin and spin-orbital interaction at threshold a high resolution measurement is proposed of the line shapes and energy shifts of antiprotonic K$\\alpha$ and L$\\alpha$ transitions of hydrogen and helium isotopes. The intense LEAR beam, stopped in the cyclotron trap at low gas pressure, provides a unique~X-ray~source with sufficient brightness. Charge coupled devices with their excellent background rejection and energy resolution allow a precise determination of the strong shifts and widths of the 1s hyperfine states of protonium, in addition the detection of the $\\bar{p}$D K$\\alpha$ transition should be possible. A focussing crystal spectrometer with a resolution $\\Delta$E/E of about l0$ ^- ^{4} $, which is superior in the accuracy of the energy determination by two orders of magnitude as compared to the present detection methods, will be used to measure the energies of the L$\\alpha$ transitions. This permits a first direct measure...

  9. Nuclear polarizability of helium isotopes in atomic transitions

    OpenAIRE

    Pachucki, K.; Moro, A. M.

    2006-01-01

    We estimate the nuclear polarizability correction to atomic transition frequencies in various helium isotopes. This effect is non-negligible for high precision tests of quantum electrodynamics or accurate determination of the nuclear charge radius from spectroscopic measurements in helium atoms and ions. In particular, it amounts to $28(3)$ kHz for 1S-2S transition in 4He+.

  10. Study of X-Ray and $\\gamma$-Ray Spectra from Antiprotonic Atoms at the Slowly Extracted Antiproton Beam of LEAR

    CERN Multimedia

    2002-01-01

    This experiment will study the X-ray spectra of antiprotonic atoms and the $\\gamma$ spectra of residual nuclei after the antiproton absorption. We intend to begin with measurements on selected isotopically pure targets. Strong interaction effects, the antiproton absorption and the atomic cascade are analysed through the measurement of energies, lineshapes, relative and absolute intensities of all observable lines. The experiments are continued to determine st in resolved fine structure levels and in different isotopes of the same element. Coincidence techniques may be applied. All components of the experimental set-up are already existing from previous experiments and we could begin the measurements with any slowly extracted beam of low energy at LEAR.

  11. Harmonic oscillator model for the helium atom

    CERN Document Server

    Carlsen, Martin

    2015-01-01

    A harmonic oscillator model in four dimensions is presented for the helium atom to estimate the distance to the inner and outer electron from the nucleus, the angle between electrons and the energy levels. The method is algebraic and is not based on the choice of correct trial wave function. Three harmonic oscillators and thus three quantum numbers are sufficient to describe the two-electron system. We derive a simple formula for the energy in the general case and in the special case of the Wannier Ridge. For a set of quantum numbers the distance to the electrons and the angle between the electrons are uniquely determined as the intersection between three surfaces. We show that the excited states converge either towards ionization thresholds or towards extreme parallel or antiparallel states and provide an estimate of the ground state energy.

  12. A Study of Confined Helium Atom

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The helium atom confined by a spherical parabolic potential well is studied employing the adiabatic hyperspherical approach method. Total energies of the ground and three low-excited states are obtained as a function of the confined potential radii. We find that the energies of a spherical parabolic potential well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. We find also that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values. The results for the three-dimensional spherical potential well and the two-dimensional disc-like potential well are compared with each other. We find that the energy difference between states in a two-dimensional parabolic potential is also obviously larger than the corresponding levels for a spherical parabolic potential.

  13. Classical Helium Atom with Radiation Reaction

    CERN Document Server

    Camelio, G; Galgani, L

    2011-01-01

    We study a classical model of Helium atom in which, in addition to the Coulomb forces, the radiation reaction forces are taken into account. This modification brings in the model a new qualitative feature of a global character. Indeed, as pointed out by Dirac, in any model of classical electrodynamics of point particles involving radiation reaction one has to eliminate, from the a priori conceivable solutions of the problem, those corresponding to the emission of an infinite amount of energy. We show that the Dirac prescription solves a problem of inconsistency plaguing all available models which neglect radiation reaction, namely, the fact that in all such models most initial data lead to a spontaneous breakdown of the atom. A further modification is that the system thus acquires a peculiar form of dissipation. In particular, this makes attractive an invariant manifold of special physical interest, the zero--dipole manifold, that corresponds to motions in which no energy is radiated away (in the dipole appro...

  14. Information on antiprotonic atoms and the nuclear periphery from the PS209 experiment

    OpenAIRE

    Trzcinska, A.; Jastrzebski, J.; Czosnyka, T.; von Egidy, T.; Gulda, K.; Hartmann, F. J.; Iwanicki, J.; Ketzer, B.; Kisielinski, M.; Klos, B.; Kurcewicz, W.; Lubinski, P.; Napiorkowski, P. J.; Pienkowski, L.; Schmidt, R.

    2001-01-01

    In the PS209 experiments at CERN two kinds of measurements were performed: the in-beam measurement of X-rays from antiprotonic atoms and the radiochemical, off-line determination of the yield of annihilation products with mass number A_t -1 (less by 1 than the target mass). Both methods give observables which allows to study the peripheral matter density composition and distribution.

  15. Atomic origins of solid helium bubbles in tungsten

    International Nuclear Information System (INIS)

    Solid helium bubbles were directly observed in the helium ion implanted tungsten (W), by different transmission electron microscopy (TEM) techniques at room temperature. The diameters of these solid helium bubbles range from 1 nm to 8 nm in diameter with the mean bubble size about 3 nm. The selected area electron diffraction (SAED) and fast Fourier transform (FFT) images revealed that solid helium bubbles possess body-centered cubic (bcc) structure with a lattice constant of 0.447 nm. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images further confirmed the existence of helium bubble in tungsten. The present findings provide an atomic level view of the microstructure evolution of helium in the materials, and revealed the existence of solid helium bubbles in materials. (rapid communication)

  16. Study of the anti-hydrogen atom and ion formation in the collisions antiproton-positronium

    International Nuclear Information System (INIS)

    The future CERN experiment called GBAR intends to measure the gravitational acceleration of antimatter on Earth using cold (neV) anti-hydrogen atoms undergoing a free fall. The experiment scheme first needs to cool anti-hydrogen positive ions, obtained thanks to two consecutive reactions occurring when an antiproton beam collides with a dense positronium cloud.The present thesis studies these two reactions in order to optimise the production of the anti-ions. The total cross sections of both reactions have been computed in the framework of a perturbation theory model (Continuum Distorted Wave - Final State), in the range 0 to 30 keV antiproton kinetic energy; several excited states of positronium have been investigated. These cross sections have then been integrated to a simulation of the interaction zone where antiprotons collide with positronium; the aim is to find the optimal experimental parameters for GBAR. The results suggest that the 2P, 3D or, to a lower extend, 1S states of positronium should be used, respectively with 2, less than 1 or 6 keV antiprotons. The importance of using short pulses of antiprotons has been underlined; the positronium will have to be confined in a tube of 20 mm length and 1 mm diameter. In the prospect of exciting the 1S-3D two-photon transition in positronium at 410 nm, a pulsed laser system had already been designed. It consists in the frequency doubling of an 820 nm pulsed titanium-sapphire laser. The last part of the thesis has been dedicated to the realisation of this laser system, which delivers short pulses (9 ns) of 4 mJ energy at 820 nm. (author)

  17. A metastable helium trap for atomic collision physics

    International Nuclear Information System (INIS)

    Full text: Metastable helium in the 23S state is an important species for atom optics and atomic collision physics. Because of its large internal energy (20eV), long lifetime (∼8000s) and large collision cross section for a range of processes, metastable helium plays an important role in atmospheric physics, plasma discharges and gas laser physics. We have embarked on a program of studies on atom-atom and electron-atom collision processes involving cold metastable helium. We confine metastable helium atoms in a magneto-optic trap (MOT), which is loaded by a transversely collimated, slowed and 2-D focussed atomic beam. We employ diode laser tuned to the 1083 nm (23S1 - 23P21) transition to generate laser cooling forces in both the loading beam and the trap. Approximately 10 million helium atoms are trapped at temperatures of ∼ 1mK. We use phase modulation spectroscopy to measure the trapped atomic density. The cold, trapped atoms can collide to produce either atomic He+ or molecular He2+ ions by Penning Ionisation (PI) or Associative Ionisation (AI). The rate of formation of these ions is dependant upon the detuning of the trapping laser from resonance. A further laser can be used to connect the 23S1 state to another higher lying excited state, and variation of the probe laser detuning used to measure interatomic collision potential. Electron-atom collision processes are studied using a monochromatic electron beam with a well defined spatial current distribution. The total trap loss due to electron collisions is measured as a function of electron energy. Results will be presented for these atomic collision physics measurements involving cold, trapped metastable helium atoms. Copyright (1999) Australian Optical Society

  18. Galactic cosmic-ray propagation in the light of AMS-02: I. Analysis of protons, helium, and antiprotons

    CERN Document Server

    Korsmeier, Michael

    2016-01-01

    We present novel constraints on cosmic-ray propagation in the Galaxy using the recent precise measurements of proton and helium spectra from AMS-02, together with preliminary AMS-02 data on the antiproton over proton ratio. To explore efficiently the large (up to eleven-dimensional) parameter space we employ the nested-sampling algorithm as implemented in the \\textsc{MultiNest} package, interfaced with the \\textsc{Galprop} code to compute the model-predicted spectra. We use VOYAGER proton and helium data, sampling the local inter-stellar spectra, to constrain the solar modulation potential. We find that the turbulence of the Galactic magnetic field is well constrained, i.e., $\\delta=0.30^{+0.03}_{-0.02}(stat)^{+0.10}_{-0.04}(sys)$, with uncertainties dominated by systematic effects. Systematic uncertainties are determined checking the robustness of the results to the minimum rigidity cut used to fit the data (from 1 GV to 5 GV), to the propagation scenario (convection vs no-convection), and to the uncertainti...

  19. Corrections to the Nonrelativistic Ground Energy of a Helium Atom

    Institute of Scientific and Technical Information of China (English)

    段一士; 刘玉孝; 张丽杰

    2004-01-01

    Considering the nuclear motion, we present the nonrelativistic ground energy of a helium atom by using a simple effective variational wavefunction with a flexible parameter k. Based on the result, the relativistic and radiative corrections to the nonrelativistic Hamiltonian are discussed. The high precision value of the helium ground energy is evaluated to be -2.90338 a.u. With the relative error 0.00034%.

  20. The Weakest Link: Bonding between Helium Atoms

    Science.gov (United States)

    Lohr, Lawrence L.; Blinder, S. M.

    2007-01-01

    A highly simplified model for helium dimers that reproduces their essential features without the need for elaborate computation is presented. The He-He potential is predicted to have minimum of 10.9 K at a nuclear separation of 5.61 bohrs.

  1. Direct High-Precision Measurement of the g-Factor of a Single Antiproton Stored in a Cryogenic Penning Trap

    CERN Document Server

    Ulmer, S; Blaum, K; Quint, W; Walz, J

    2012-01-01

    We propose a direct high-precision measurement of the magnetic moment, or g-factor, of a single antiproton stored in a cryogenic Penning trap. Currently the most precise value of the magnetic moment of the antiproton is extracted from hyperfine spectroscopy of antiprotonic helium atoms, and known with a relative precision of $10^{-3}$, only . With the experiment proposed in this Letter of Intent we aim at a measurement with a relative precision of $10^{-9}$ or better.

  2. Four-Parameter Scheme for Ground Level of Helium Atom

    Institute of Scientific and Technical Information of China (English)

    HU Xian-Quan; XU Jie; MA Yong; ZHENG Rui-Lun

    2006-01-01

    In this paper, the ground state wave function of four parameters is developed and the expression of the ground state level is derived for the helium atom when the radial Schrodinger equation of the helium atom is solved.The ground energy is respectively computed by the optimized algorithms of Matlab 7.0 and the Monte Carlo methods.Furthermore, the ground state wave function is obtained. Compared with the experiment value and the value with the variation calculus in reference, the results of this paper show that in the four-parameter scheme, not only the calculations become more simplified and precise, but also the radial wave function of the helium atom meets the space symmetry automatically in ground state.

  3. Electronically excited rubidium atom in a helium cluster or film

    Science.gov (United States)

    Leino, Markku; Viel, Alexandra; Zillich, Robert E.

    2008-11-01

    We present theoretical studies of helium droplets and films doped with one electronically excited rubidium atom Rb∗ (P2). Diffusion and path integral Monte Carlo approaches are used to investigate the energetics and the structure of clusters containing up to 14 helium atoms. The surface of large clusters is approximated by a helium film. The nonpair additive potential energy surface is modeled using a diatomic in molecule scheme. Calculations show that the stable structure of Rb∗Hen consists of a seven helium atom ring centered at the rubidium, surrounded by a tirelike second solvation shell. A very different structure is obtained when performing a "vertical Monte Carlo transition." In this approach, a path integral Monte Carlo equilibration starts from the stable configuration of a rubidium atom in the electronic ground state adsorbed to the helium surface after switching to the electronically excited surface. In this case, Rb∗Hen relaxes to a weakly bound metastable state in which Rb∗ sits in a shallow dimple. The interpretation of the results is consistent with the recent experimental observations [G. Auböck et al., Phys. Rev. Lett. 101, 035301 (2008)].

  4. Giant Helium Dimers Produced by Photoassociation of Ultracold Metastable Atoms

    OpenAIRE

    Leonard, J.; Walhout, M.; Mosk, A. P.; Mueller, T.; Leduc, M; Cohen-Tannoudji, C.

    2003-01-01

    We produce giant helium dimers by photoassociation of metastable helium atoms in a magnetically trapped, ultracold cloud. The photoassociation laser is detuned red of the atomic $2^3S_1 - 2^3P_0 $ line and produces strong heating of the sample when resonant with molecular bound states. The temperature of the cloud serves as an indicator of the molecular spectrum. We report good agreement between our spectroscopic measurements and our calculations of the five bound states belonging to a $0_u^+...

  5. An investigation of high fractions of metastable helium atoms

    Institute of Scientific and Technical Information of China (English)

    X.P.Feng(冯贤平); B.W.James

    2003-01-01

    Penning type discharge was adopted to excite helium atoms. It is suitable for generating high densitymetastables at a range from 0.1 mTorr to 0.5 Tort. The highest metastable density of 3.5 × 1010 cm-3was observed at a static gas pressure of 0.5 Torr. The highest fraction of metastables (N21s/NHe) of 10-3in a low gas pressure was obtained. The variation of the magnetic field strength on the discharge doesnot result in a significant density change of the metastable helium atoms. When no magnetic field wasapplied, no discharge took place.

  6. Electronic state of helium atoms in nickel metal

    International Nuclear Information System (INIS)

    The molecular orbital calculations are carried out for model clusters to investigate the electronic state of the interstitial helium atoms implanted into nickel metal. The computational method used is the discrete variational Xα (DV-Xα) method. In order to study the difference in the electronic structures of helium atoms between at the tetrahedral site and at the octahedral one, the computations are performed using model clusters, Ni4He and Ni6He. The bond strength is evaluated by the use of Mulliken population analysis. The computations are also carried out for the larger cluster Ni14He to investigate the size effect of the cluster model. Furthermore, the electronic structure of the He9 cluster in Ni metal is studied, using the Ni14He9 cluster model which includes both of tetrehedral and octahedral interstitial He atoms. This paper discusses the interactions between He and Ni atoms when both interstitial He atoms coexist. (orig.)

  7. Using Uncertainty Principle to Find the Ground-State Energy of the Helium and a Helium-like Hookean Atom

    Science.gov (United States)

    Harbola, Varun

    2011-01-01

    In this paper, we accurately estimate the ground-state energy and the atomic radius of the helium atom and a helium-like Hookean atom by employing the uncertainty principle in conjunction with the variational approach. We show that with the use of the uncertainty principle, electrons are found to be spread over a radial region, giving an electron…

  8. Physics at CERN's Antiproton Decelerator

    CERN Document Server

    Hori, M

    2013-01-01

    The Antiproton Decelerator of CERN began operation in 1999 to serve experiments for studies of CPT invariance by precision laser and microwave spectroscopy of antihydrogen ($\\bar{\\rm H}$) and antiprotonic helium ($\\bar{p}{\\rm He}^+$). The first 12 years of operation saw cold $\\bar{\\rm H}$ synthesized by overlapping clouds of positrons ($e^+$) and antiprotons ($\\bar{p}$) confined in magnetic Penning traps. Cold $\\bar{\\rm H}$ was also produced in collisions between Rydberg positronium atoms and $\\bar{p}$. Ground-state $\\bar{\\rm H}$ was later trapped for up to $\\sim 1000$ s in a magnetic bottle trap, and microwave transitions excited between its hyperfine levels. In the $\\bar{p}{\\rm He}^+$ atom, UV transitions were measured to a precision of (2.3-5) $\\times$ $10^{-9}$ by sub-Doppler two-photon laser spectroscopy. From this the antiproton-to-electron mass ratio was determined as $M_{\\bar{p}}/m_e=$1836.1526736(23), which agrees with the p value. Microwave spectroscopy of $\\bar{p}{\\rm He}^+$ yielded a measurement o...

  9. The Helium Atom and Isoelectronic Ions in Two Dimensions

    Science.gov (United States)

    Patil, S. H.

    2008-01-01

    The energy levels of the helium atom and isoelectronic ions in two dimensions are considered. The difficulties encountered in the analytical evaluation of the perturbative and variational expressions for the ground state, promote an interesting factorization of the inter-electronic interaction, leading to simple expressions for the energy. This…

  10. Resonances of the helium atom in a strong magnetic field

    DEFF Research Database (Denmark)

    Lühr, Armin Christian; Al-Hujaj, Omar-Alexander; Schmelcher, Peter

    2007-01-01

    We present an investigation of the resonances of a doubly excited helium atom in a strong magnetic field covering the regime B=0–100  a.u. A full-interaction approach which is based on an anisotropic Gaussian basis set of one-particle functions being nonlinearly optimized for each field strength is...

  11. A Complete Model Helium Atom: Theoretical Emissivities, the Case B Approximation, and the Primordial Helium Abundance

    Science.gov (United States)

    Porter, R. L.; Bauman, R. P.; MacAdam, K. B.; Ferland, G. J.

    2004-12-01

    We have completed the development of a new model helium atom for the spectra simulation code Cloudy. All relevant astrophysically significant processes are included, and the spectrum is solved self-consistently with the thermal and ionization structure of the simulated system. We present here an overview of the differences that distinguish our model from those by previous authors. We also compare predicted case B emissivities with those from previous works. The differences will have significant consequences for the interpretation of spectra of a wide variety of systems. We also explore deviations from the case B approximation and present an estimate of the primordial helium abundance.

  12. Unified treatment of hadronic annihilation and protonium formation in slow collisions of antiprotons with hydrogen atoms

    Science.gov (United States)

    Sakimoto, Kazuhiro

    2013-07-01

    Antiproton (p¯) collisions with hydrogen atoms, resulting in the hadronic process of particle-antiparticle annihilation and the atomic process of protonium (p¯p) formation (or p¯ capture), are investigated theoretically. As the collision energy decreases, the collision time required for the p¯ capture becomes necessarily longer. Then, there is the possibility that the p¯-p annihilation occurs significantly before the p¯ capture process completes. In such a case, one can no longer consider the annihilation decay separately from the p¯ capture process. The present study develops a rigorous unified quantum-mechanical treatment of the annihilation and p¯ capture processes. For this purpose, an R-matrix approach for atomic collisions is extended to have complex-valued R-matrix elements allowing for the hadronic annihilation. Detailed calculations are carried out at low collision energies ranging from 10-8 to 10-1 eV, and the annihilation and the p¯ capture (total and product-state selected) cross sections are reported. Consideration is given to the difference between the direct annihilation occurring during the collision and the annihilation of p¯p occurring after the p¯ capture. The present annihilation process is also compared with the annihilation in two-body p¯+p collisions.

  13. Quantum entanglement for helium atom in the Debye plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yen-Chang, E-mail: linyc@pub.iams.sinica.edu.tw [Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei 106, Taiwan (China); Graduate Institute of Applied Science and Engineering, Fu-Jen Catholic University, New Taipei City 24205, Taiwan (China); Fang, Te-Kuei, E-mail: 051420@mail.fju.edu.tw [Department of Physics, Fu Jen Catholic University, New Taipei City 24205, Taiwan (China); Ho, Yew Kam, E-mail: ykho@pub.iams.sinica.edu.tw [Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei 106, Taiwan (China)

    2015-03-15

    In the present work, we present an investigation on quantum entanglement of the two-electron helium atom immersed in weakly coupled Debye plasmas, modeled by the Debye-Hückel, or screened Coulomb, potential to mimic the interaction between two charged particles inside the plasma. Quantum entanglement is related to correlation effects in a multi-particle system. In a bipartite system, a measurement made on one of the two entangled particles affects the outcome of the other particle, even if such two particles are far apart. Employing wave functions constructed with configuration interaction B-spline basis, we have quantified von Neumann entropy and linear entropy for a series of He {sup 1,3}S{sup e} and {sup 1,3}P{sup o} states in plasma-embedded helium atom.

  14. Quantum entanglement for helium atom in the Debye plasmas

    International Nuclear Information System (INIS)

    In the present work, we present an investigation on quantum entanglement of the two-electron helium atom immersed in weakly coupled Debye plasmas, modeled by the Debye-Hückel, or screened Coulomb, potential to mimic the interaction between two charged particles inside the plasma. Quantum entanglement is related to correlation effects in a multi-particle system. In a bipartite system, a measurement made on one of the two entangled particles affects the outcome of the other particle, even if such two particles are far apart. Employing wave functions constructed with configuration interaction B-spline basis, we have quantified von Neumann entropy and linear entropy for a series of He 1,3Se and 1,3Po states in plasma-embedded helium atom

  15. Low helium permeation cells for atomic microsystems technology.

    Science.gov (United States)

    Dellis, Argyrios T; Shah, Vishal; Donley, Elizabeth A; Knappe, Svenja; Kitching, John

    2016-06-15

    Laser spectroscopy of atoms confined in vapor cells can be strongly affected by the presence of background gases. A significant source of vacuum contamination is the permeation of gases such as helium (He) through the walls of the cell. Aluminosilicate glass (ASG) is a material with a helium permeation rate that is many orders of magnitude lower than borosilicate glass, which is commonly used for cell fabrication. We have identified a suitable source of ASG that is fabricated in wafer form and can be anodically bonded to silicon. We have fabricated chip-scale alkali vapor cells using this glass for the windows and we have measured the helium permeation rate using the pressure shift of the hyperfine clock transition. We demonstrate micro fabricated cells with He permeation rates at least three orders of magnitude lower than that of cells made with borosilicate glass at room temperature. Such cells may be useful in compact vapor-cell atomic clocks and as a micro fabricated platform suitable for the generation of cold atom samples. PMID:27304286

  16. Isotopic and Symmetry Effects in the Collision of Atomic Helium

    Science.gov (United States)

    Bouledroua, Moncef; Bouchelaghem, Fouzia; Tahar Bouazza, M.; Reggami, Lamia

    2006-11-01

    The thermophysical properties of a helium dilute gas at low and high temperatures are revisited with new and recent potential data points. The second virial coefficients are computed in order to assess the accuracy of the constructed He-He potentials. The results, mainly at high temperatures, are in a good agreement with the published values. The isotopic effects due to the presence of ^4He and ^3He atoms are also examined and the calculations of various transport parameters, namely diffusion, viscosity, and thermal conductivity, are extended to include the nuclear spins and the symmetry effects, which arise from the identity and indistinguishability of the colliding atoms.

  17. Ab initio potential energy curve for the helium atom pair and thermophysical properties of the dilute helium gas. I. Helium-helium interatomic potential

    OpenAIRE

    Vogel, Eckhard; Bich, Eckard; Hellmann, Robert

    2007-01-01

    Abstract A helium-helium interatomic potential energy curve was determined from quantum-mechanical \\textit{ab initio} calculations. Very large atom-centred basis sets including a newly developed d-aug-cc-pV8Z basis set supplemented with bond functions and \\textit{ab initio} methods up to Full CI were applied. The aug-cc-pV7Z basis set of Gdanitz (\\emph{J. Chem. Phys.}, \\textbf{113}, 5145 (2000)) was modified to be more consistent with the aug-cc-pV5Z and aug-cc-pV6Z basis set...

  18. Coupled-Channel Investigation of the Collision of Protons and Antiprotons with Hydrogen- Like Atoms in the 2s States

    Institute of Scientific and Technical Information of China (English)

    Reda S. Tantawi

    2003-01-01

    The influence of the electric charge of both the projectile and the target nucleus on the cross section of the inelastic collision of protons and antiprotons with atoms is investigated at energies ranging from i to 2500 KeV. The impact parameter method is used to analyse the cross sections of the excitation of the n = 3 states of H atom and He+, Li2+ ions being initially in the excited 2s states. The calculated cross sections for hydrogen atoms are compared with the other theoretical results based on coupled-channels methods.

  19. Isotopically selective collinear laser photoionization of accelerated helium atoms

    International Nuclear Information System (INIS)

    Collinear two-step laser photoionization of 3He and 4He isotopes, accelerated to energies of up to 3.9 keV, is described. It is shown that the ionization selectivity in the case of the rare isotope 3He is 106 for a residual-gas pressure of 10-7 Torr in the vacuum system. The sensitivity is limited by collisions that result in the excitation of fast metastable atoms to Rydberg states in the field-free region, and by impact ionization of fast atoms in the region of the ionizer. It is shown that the ionization of helium atoms excited to n3D states occurs along the adiabatic and diabatic channels

  20. Electronic Relaxation Processes of Transition Metal Atoms in Helium Nanodroplets

    Science.gov (United States)

    Kautsch, Andreas; Lindebner, Friedrich; Koch, Markus; Ernst, Wolfgang E.

    2014-06-01

    Spectroscopy of doped superfluid helium nanodroplets (He_N) gives information about the influence of this cold, chemically inert, and least interacting matrix environment on the excitation and relaxation dynamics of dopant atoms and molecules. We present the results from laser induced fluorescence (LIF), photoionization (PI), and mass spectroscopy of Cr and Cu doped He_N. From these results, we can draw a comprehensive picture of the complex behavior of such transition metal atoms in He_N upon photo-excitation. The strong Cr and Cu ground state transitions show an excitation blueshift and broadening with respect to the bare atom transitions which can be taken as indication for the solvation inside the droplet. From the originally excited states the atoms relax to energetically lower states and are ejected from the He_N. The relaxation processes include bare atom spin-forbidden transitions, which clearly bears the signature of the He_N influence. Two-color resonant two-photon ionization (2CR2PI) also shows the formation of bare atoms and small Cr-He_n and Cu-He_n clusters in their ground and metastable states ^c. Currently, Cr dimer excitation studies are in progress and a brief outlook on the available results will be given. C. Callegari and W. E. Ernst, Helium Droplets as Nanocryostats for Molecular Spectroscopy - from the Vacuum Ultraviolet to the Microwave Regime, in Handbook of High-Resolution Spectroscopy, eds. M. Quack and F. Merkt, John Wiley & Sons, Chichester, 2011. A. Kautsch, M. Koch, and W. E. Ernst, J. Phys. Chem. A, 117 (2013) 9621-9625, DOI: 10.1021/jp312336m F. Lindebner, A. Kautsch, M. Koch, and W. E. Ernst, Int. J. Mass Spectrom. (2014) in press, DOI: 10.1016/j.ijms.2013.12.022 M. Koch, A. Kautsch, F. Lackner, and W. E. Ernst, submitted to J. Phys. Chem. A

  1. Penning collisions of laser-cooled metastable helium atoms

    Science.gov (United States)

    Pereira Dos Santos, F.; Perales, F.; Léonard, J.; Sinatra, A.; Wang, Junmin; Saverio Pavone, F.; Rasel, E.; Unnikrishnan, C. S.; Leduc, M.

    2001-04-01

    We present experimental results on the two-body loss rates in a magneto-optical trap of metastable helium atoms. Absolute rates are measured in a systematic way for several laser detunings ranging from -5 to -30 MHz and at different intensities, by monitoring the decay of the trap fluorescence. The dependence of the two-body loss rate coefficient β on the excited state ( 23P2) and metastable state ( 23S1) populations is also investigated. From these results we infer a rather uniform rate constant Ksp = (1+/-0.4)×10-7 cm3/s.

  2. Non-sequential double ionization of helium-like atom

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, author investigated the effect of the Coulomb potential of the core of atomic helium on the rescattering processes. Through the calculation author concluded that the Coulomb potential effect may not play an important role in causing the discrepancy between the experimental data and theoretical results of Kuchievs model, and the NS ionization is dependent on the frequency of the laser field. Furthermore, it is concluded that the strength of the laser field and the charge number of the core affect the frequency regime corresponding to the peak value of the NS ionization rate.

  3. Atom trapping: application to electron collision studies of metastable helium

    International Nuclear Information System (INIS)

    Full text: We report on the first measurements of electron scattering from metastable helium atoms (He) confined in a magneto-optic trap (MOT). Using conventional crossed beam techniques, measurement of electron scattering cross sections for He is experimentally very difficult, due the intrinsically low atomic densities produced by nozzle discharge sources, and the need to locate the interaction region well away from stray electric and magnetic fields. Electron interactions with excited state atoms are fundamentally important to many naturally processes in atmospheric and astrophysical chemistry, gas lasers and plasma processing. Until these experiments, no data for He existed in the intermediate (10-100 eV) range to verify theoretical predictions. Our MOT contains up to 108 atoms at temperatures of ∼1mK that act as a high (∼109 cm-3) density target for a pulsed electron beam. We employ optical molasses to reduce the atomic velocity, and hence the trap decay time when released from the optical and magnetic fields. The total cross section is determined using phase modulation spectroscopy to measure the fractional loss rate of the trapped atoms with the electron gun on, and the electron current density is measured using scanning wire techniques to yield the absolute total cross section

  4. Microwave multiphoton ionization and excitation of helium Rydberg atoms

    International Nuclear Information System (INIS)

    We study experimentally and theoretically the detailed field-amplitude dependence of the multiphoton ionization and excitation probability of highly excited n03S helium atoms in a 9.924-GHz linearly polarized microwave electric field. For ionization, with principal quantum numbers in the range n0=25--32, we use a quasistatic analysis that employs integration of the time-dependent Schroedinger equation using basis states of the static field Hamiltonian. The calculated results are used to interpret the observed ionization threshold structure. For excitation, the results of n03S→n03L, L>2 excitation experiments are explained quantitatively and precisely using a theory of multiphoton resonances. We present maps of quasienergy levels that allow the study of the dynamics of the field-switching transients. These transient effects are analyzed along the lines of standard atomic collision theory and are shown to determine the shape of the observed resonances

  5. Electronic Structure of Helium Atom in a Quantum Dot

    Science.gov (United States)

    Jayanta, K. Saha; Bhattacharyya, S.; T. K., Mukherjee

    2016-03-01

    Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization method. To be specific, precise energy eigenvalues of bound 1sns (1Se) (n = 1-6) states and the resonance parameters i.e. positions and widths of 1Se states due to 2sns (n = 2-5) and 2pnp (n = 2-5) configurations of confined helium below N = 2 ionization threshold of He+ have been estimated. The two-parameter (Depth and Width) finite oscillator potential is used to represent the confining potential due to the quantum dot. It has been explicitly demonstrated that the electronic structural properties become sensitive functions of the dot size. It is observed from the calculations of ionization potential that the stability of an impurity ion within a quantum dot may be manipulated by varying the confinement parameters. A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the width of the quantum cavity is also discussed here. TKM Gratefully Acknowledges Financial Support under Grant No. 37(3)/14/27/2014-BRNS from the Department of Atomic Energy, BRNS, Government of India. SB Acknowledges Financial Support under Grant No. PSW-160/14-15(ERO) from University Grants Commission, Government of India

  6. Application of cold beam of atoms and molecules for studying luminescence of oxygen atoms stimulated by metastable helium

    International Nuclear Information System (INIS)

    We describe a method for creating a high flux beam of cold atoms and molecules. By using this beam method, spectroscopic studies of the afterglow of oxygen-helium gas mixtures at cryogenic temperatures were performed. The cooling by helium vapor of a helium jet containing trace amounts of oxygen after passing through a radiofrequency discharge zone led to the observation of strong emissions from atomic oxygen. The effect results from the increased efficiency of energy transfer from metastable helium atoms and molecules to the atomic oxygen in the cold dense helium vapor. The effect might find application for the detection of small quantities of impurities in helium gas as well as possible laser action

  7. Collisions of low-energy antiprotons and protons with atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Luehr, Armin

    2010-02-18

    Antiproton (anti p) collisions have evolved to a powerful tool for the testing of dynamic electron correlations in atoms and molecules. While advances in the understanding of anti p collisions with the simplest one- and two-electron atoms, H and He, have been achieved experiment and theory did not agree for low-energy anti p+He collisions (<40 keV), stimulating a vivid theoretical activity. On the other hand, only very few theoretical anti p studies can be found considering molecular as well as other atomic targets, in contrast to proton (p) collisions. This is in particular true for anti p impacts on H{sub 2} despite its fundamental role in representing the simplest two-electron molecule. The obtained results may be useful for the anti p experiments at CERN (e.g., antihydrogen production) and in particular for the facility design of low-energy anti p storage rings (e.g., at FLAIR) where a precise knowledge of the anti p interaction with the dominant residual-gas molecule H{sub 2} is needed. In this work a nonperturbative, time-dependent numerical approach is developed which describes ionization and excitation of atoms or molecules by either anti p or p impact based on the impact-parameter method. A spectral close-coupling method is employed for solving the time-dependent Schroedinger equation in which the scattering wave function is expanded in (effective) one- or two-electron eigenstates of the target. This includes for the first time a full two-electron, two-center description of the H{sub 2} molecule in anti p collisions. The radial part of the one-electron eigenstates is expanded in B splines while the two-electron basis is obtained with a configurationinteraction approach. Calculations are performed for anti p collisions with H, H{sub 2}{sup +}, and H{sub 2} as well as with He and alkali-metal atoms Li, Na, K, and Rb. Additionally, data are obtained for p collisions with H{sub 2}, Li, Na, and K. The developed method is tested and validated by detailed

  8. A high-intensity beam of metastable helium atoms with good velocity resolution

    International Nuclear Information System (INIS)

    The excitation of a low-energy ground state helium beam to its metastable states by electron impact is analysed. It is shown that the narrowest velocity distribution for the resulting metastable helium beam is obtained by directing the helium and electron beams parallel or antiparallel. A source of metastable helium atoms was constructed according to this analysis which produced a beam of 3 x 1014 metastable atoms/s sr with a velocity resolution of 3% FWHM for a room-temperature beam (E = 66 MeV). A possible source of errors in time-of-flight experiments with metastable atoms is pointed out. (author)

  9. Collisions of low-energy antiprotons and protons with atoms and molecules

    International Nuclear Information System (INIS)

    Antiproton (anti p) collisions have evolved to a powerful tool for the testing of dynamic electron correlations in atoms and molecules. While advances in the understanding of anti p collisions with the simplest one- and two-electron atoms, H and He, have been achieved experiment and theory did not agree for low-energy anti p+He collisions (2 despite its fundamental role in representing the simplest two-electron molecule. The obtained results may be useful for the anti p experiments at CERN (e.g., antihydrogen production) and in particular for the facility design of low-energy anti p storage rings (e.g., at FLAIR) where a precise knowledge of the anti p interaction with the dominant residual-gas molecule H2 is needed. In this work a nonperturbative, time-dependent numerical approach is developed which describes ionization and excitation of atoms or molecules by either anti p or p impact based on the impact-parameter method. A spectral close-coupling method is employed for solving the time-dependent Schroedinger equation in which the scattering wave function is expanded in (effective) one- or two-electron eigenstates of the target. This includes for the first time a full two-electron, two-center description of the H2 molecule in anti p collisions. The radial part of the one-electron eigenstates is expanded in B splines while the two-electron basis is obtained with a configurationinteraction approach. Calculations are performed for anti p collisions with H, H2+, and H2 as well as with He and alkali-metal atoms Li, Na, K, and Rb. Additionally, data are obtained for p collisions with H2, Li, Na, and K. The developed method is tested and validated by detailed comparison of the present findings for p impacts and for anti p+He collisions with literature data. On the other hand, total and differential cross sections for ionization and excitation of the targets by anti p impact complement the sparse literature data of this kind. Results gained from different targets as well

  10. Electronic structure of helium atom in a quantum dot

    CERN Document Server

    Saha, Jayanta K; Mukherjee, T K

    2015-01-01

    Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization method. To be specific, precise energy eigenvalues of bound 1sns (1Se) [n = 1-6] states and the resonance parameters i.e. positions and widths of 1Se states due to 2sns [n = 2-5] and 2pnp [n = 2-5] configuration of confined helium below N = 2 ionization threshold of He+ have been estimated. The two-parameter (Depth and Width) finite oscillator potential is used to represent the confining potential representing the quantum dot. It has been explicitly demonstrated that electronic structure properties become a sensitive function of the dot size. It is observed from the calculations of ionization potential that the stability of an impurity ion within quantum dot may be manipulated by varying the confinement parameters. A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the wi...

  11. A Helium Atom Confined by a Spherical Gaussian Potential Well

    Institute of Scientific and Technical Information of China (English)

    QIU Liang; XIE Wen-Fang; WANG An-Min

    2008-01-01

    The helium atom confined by a non-impenetrable spherical box, i.e., a spherical Gaussian potential well which possesses finite height and range, is studied employing the exact diagonalization method. Total energies of the ground and three low-excited states are obtained as a function of the confined potential radii. We find that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values. The results for the three-dimensional spherical potential well and the two-dimensional disc-like potential well are compared with each other: in general, the energies of the states decrease and the energy intervals between states increase with the reduction of the space dimensions.

  12. S142 set-up to detect X-ray from antiproton-proton atoms (protonium).

    CERN Multimedia

    1978-01-01

    This experiment was designed by the Daresbury-Mainz-TRIUMF Collaboration and was located in the m14 partially separated antiproton beam in the PS South Hall. It used a gaseous hydrogen target, 1 m long, surrounded by a ring of proportional counters, surrounded in turn by a ring of 36 scintillators strips to aid in the annihilation product identification. Ugo Gastaldi (centre)

  13. First principles investigation of cluster consisting of hydrogen–helium atoms interstitially-trapped in tungsten

    International Nuclear Information System (INIS)

    We evaluate the binding energies of mixed helium and hydrogen clusters consisted of interstitially trapped atoms in bcc tungsten by first-principles calculations based on density functional theories. It is shown that helium-rich interstitially-trapped clusters have the positive binding energies and the low electron-density region expand as the number of helium in the cluster increase. Thus, the helium-rich interstitially trapped clusters can act as a trapping site for hydrogen, and interstitially trapped helium interrupts or disturbs the hydrogen diffusion in tungsten

  14. Semiclassical calculation of ionisation rate for Rydberg helium atoms in an electric field

    Institute of Scientific and Technical Information of China (English)

    Wang De-Hua

    2011-01-01

    The ionisation of Rydberg helium atoms in an electric field above the classical ionisation threshold has been examined using the semiclassical method, with particular emphasis on discussing the influence of the core scattering on the escape dynamics of electrons. The results show that the Rydberg helium atoms ionise by emitting a train of electron pulses. Unlike the case of the ionisation of Rydberg hydrogen atom in parallel electric and magnetic fields,where the pulses of the electron are caused by the external magnetic field, the pulse trains for Rydberg helium atoms are created through core scattering. Each peak in the ionisation rate corresponds to the contribution of one core-scattered combination trajectory. This fact further illustrates that the ionic core scattering leads to the chaotic property of the Rydberg helium atom in external fields. Our studies provide a simple explanation for the escape dynamics in the ionisation of nonhydrogenic atoms in external fields.

  15. Preparations for HFS spectroscopy of antiprotonic 3He

    International Nuclear Information System (INIS)

    Full text: Antiprotonic helium (pHe) is a neutral exotic atom, consisting of a helium nucleus, an electron and an antiproton. The interactions of the angular momenta and spins of its constituents cause splitting within the principle states. The measured transition frequencies between hyperfine levels can be compared with three-body QED calculations as a test of the theory. Previous measurements have been performed on p4He. The next two years will be dedicated to measuring a similar transition within p3He. Due to the additional coupling to the helion spin, it consists of an octuplet of states instead of a quadruplet. A new microwave cavity has been designed and is being constructed for the transition frequency of 11.14 GHz. This cavity has been simulated using the high frequency structure simulator HFSS to obtain the correct cavity dimensions. A new cryostat to cool the target is under construction. Numerical simulations are also in progress. (author)

  16. Associative ionization of neon and helium atoms by collisions of excited helium (31p) atoms of thermal energies

    International Nuclear Information System (INIS)

    The relative cross-sections of ionizing collisions between He + He and He + Ne atoms, have been studied, the helium being excited in a state (31p) by a laser beam. The results obtained made it possible (a) to reveal in a direct manner the production of molecular ions He2+ and He Ne+ and (b) to determine the relative change in the associative ionizing cross-section in the area (0.035 - 0.17 eV) in the He (31P) + Ne collision, despite the very short life of the He (31P) excited state (1.7 ns). The production of He2+ ions from an He (3 1P) + He collision sets an upper limit to the appearance potential of these ions. The experimental study of the associative ionization in the He (31P) + Ne system made it possible to extend the utilization of the GAMMA(R) self ionization model, already tested for the metastable states, to the radiative states. The GAMMA(R) model seems well suited for the description of collisions of the A excited + B type, where the excitation energy of A is greater than the ionization potential of B

  17. Professor Walter Oelert, leader of the team which created the first atoms of antihydrogen at the Low Energy Antiproton Ring (LEAR) in January 1996

    CERN Multimedia

    Laurent Guiraud

    1996-01-01

    Antiparticles were predicted in the work of Paul Dirac in the 1920's, since when physicists have identified all the necessary antiparticle constituents of an antiparticle atom - antielectrons (positrons), antiprotons and antineutrons. However, an antihydrogen atom wasn't produced until the PS210 experiment at CERN in 1995. PS210 used the LEAR accelerator, which was then nearing the end of its lifetime, so everything in the experiment had to work first time. After installing the equipment in spring 1995, the experiment took place in the autumn, in two hour periods over 4 weeks. The experiment team collided energetic antiprotons from LEAR with a heavy element, a challenge for them as well as the LEAR operators. Proving that antihydrogen atoms had been formed required several more weeks of data analysis, but the announcement that nine antihydrogen atoms had been produced came on 4 January 1996.

  18. Effects of discharge current and voltage on the high density of metastable helium atoms

    Institute of Scientific and Technical Information of China (English)

    Feng Xian-Ping(冯贤平); D Andruczyk; B W James; K Takiyama; S Namba; T Oda

    2003-01-01

    Both hollow-cathode and Penning-type discharges were adopted to excite helium atoms to a metastable state.Experimental data indicate that Penning discharge is more suitable for generating high fractions of metastables in a low-density helium beam for laser-induced fluorescence technique in measuring electric fields at the edge of a plasma.The metastable density increases with increasing helium gas pressure in the range of 1.33× 10-2-66.7Pa. The highest metastable density of 3.8 × 1016m-3 is observed at a static gas pressure of 66.7Pa. An approximately linear relationship between the density of metastable helium atoms and the plasma discharge current is observed. Magnetic field plays a very important role in producing a high density of metastable atoms in Penning discharge.

  19. Effects of discharge current and voltage on the high density of metastable helium atoms

    Institute of Scientific and Technical Information of China (English)

    FengXian-Ping; DAndruczyk; BWJames; KTakiyama; SNamba; TOda

    2003-01-01

    Both hollow-cathode and Penning-type discharges were adopted toexcite helium atoms to a metastable state. Experimental data indicate that Penning discharge is more suitable for generating high fractions of metastables in a low-density helium hean for laser-induced fluorescence technique in measuring electric fields at the edge of a plasma. The metastable density increases with increasing helium gas pressure in the range of 1.33×10-2-66.7Pa. The highest metastable density of 3.8×1016m-3 is observed at a static gas pressure of 66.7Pa. An approximately linear relationship between the density of metastable helium atoms and the plasma discharge current is observed. Magnetic field plays a very important role in producing a high density of metastable atoms in Penning discharge.

  20. Nuclear physics with antiprotons

    International Nuclear Information System (INIS)

    The use of antiproton beams in Nuclear Physics has been until now limited to a few total and reaction cross section measurements and to the study of antiprotonic atoms. This situation is presently about to change with the advent of the low Energy Antiproton Ring ''LEAR'' at CERN which started to deliver antiprotons for Physics experiments in July 1983. But what can we learn from Nuclear Physics with antiprotons. To answer this question I will first review basic and simple features of the low energy antiN-N interaction and their energy dependence. I will show that the antiproton is an interesting probe to explore the nucleus and bring informations complementary to that already provided by the other usual probe like e, p, π, α particles etc... I will in turn point out a few points that make a nucleus a very useful laboratory to study the antiN-N elementary interaction and get informations that are not available in the free antiN-N interaction

  1. Introduction to Density Functional Theory: Calculations by Hand on the Helium Atom

    Science.gov (United States)

    Baseden, Kyle A.; Tye, Jesse W.

    2014-01-01

    Density functional theory (DFT) is a type of electronic structure calculation that has rapidly gained popularity. In this article, we provide a step-by-step demonstration of a DFT calculation by hand on the helium atom using Slater's X-Alpha exchange functional on a single Gaussian-type orbital to represent the atomic wave function. This DFT…

  2. Atomic scattering from an adsorbed monolayer solid with a helium beam that penetrates to the substrate

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Bruch, L.W.; Dammann, Bernd

    2013-01-01

    Diffraction and one-phonon inelastic scattering of a thermal energy helium atomic beam are evaluated in the situation that the target monolayer lattice is so dilated that the atomic beam penetrates to the interlayer region between the monolayer and the substrate. The scattering is simulated by...

  3. Laser-excitation atomic fluorescence spectroscopy in a helium microwave-induced plasma

    Science.gov (United States)

    Schroeder, Timothy S.

    The focus of this dissertation is to report the first documented coupling of helium microwave induced plasmas (MIPs) to laser excitation atomic fluorescence spectroscopy. The ability to effectively produce intense atomic emission from both metal and nonmetal analytes gives helium microwave induced plasmas a greater flexibility than the more commonly utilized argon inductively coupled plasma (ICP). Originally designed as an element selective detector for non-aqueous chromatography applications at low applied powers (plasma has been applied to aqueous sample determinations at higher applied powers (>500 W). The helium MIP has been shown to be a very powerful analytical atomic spectroscopy tool. The development of the pulsed dye laser offered an improved method of excitation in the field of atomic fluorescence. The use of laser excitation for atomic fluorescence was a logical successor to the conventional excitation methods involving hollow cathode lamps and continuum sources. The highly intense, directional, and monochromatic nature of laser radiation results in an increased population of atomic species in excited electronic states where atomic fluorescence can occur. The application of laser excitation atomic fluorescence to the analysis of metals in a helium microwave induced plasma with ultrasonic sample nebulization was the initial focus of this work. Experimental conditions and results are included for the aqueous characterization of manganese, lead, thallium, and iron in the helium MIP- LEAFS system. These results are compared to previous laser excitation atomic fluorescence experimentation. The effect of matrix interferences on the analytical fluorescence signal was also investigated for each element. The advantage of helium MIPs over argon ICPs in the determination of nonmetals in solution indicates that the helium MIP is an excellent candidate for laser excitation atomic fluorescence experiments involving nonmetals such as chlorine, bromine, iodine, and

  4. The Effects of the Pauli Exclusion Principle in Determining the Ionization Energies of the Helium Atom and Helium-Like Ions

    Science.gov (United States)

    Deeney, F. A.; O'Leary, J. P.

    2012-01-01

    For helium and helium-like ions, we have examined the differences between the values of the ionization energies as calculated from the Bohr theory and those measured in experiments. We find that these differences vary linearly with the atomic number of the system. Using this result, we show how the Bohr model for single-electron systems may be…

  5. ALPHA freezes antiprotons

    CERN Multimedia

    CERN Bulletin

    2010-01-01

    Laboratories like CERN can routinely produce many different types of antiparticles. In 1995, the PS210 experiment formed the first antihydrogen atoms and a few years later, in 2002, ATRAP and ATHENA were already able to produce several thousand of them. However, no experiment in the world has succeeded in ‘trapping’ these anti-atoms in order to study them. This is the goal of the ALPHA experiment, which has recently managed to cool down the antiprotons to just a few Kelvin. This represents a major step towards trapping the anti-atom, thus opening a new avenue into the investigation of antimatter properties.   Members of the ALPHA collaboration working on the apparatus in the Antiproton Decelerator experimental hall at CERN. Just like the atom, the anti-atom is neutral. Unlike the atom, the anti-atom is made up of antiprotons (as opposed to protons in the atom) and positrons (as opposed to electrons). In order to thoroughly study the properties of the anti-atoms, scien...

  6. Dynamics of thermoluminescence spectra of impurity-helium condensates containing stabilized nitrogen and oxygen atoms

    International Nuclear Information System (INIS)

    The results of investigations of thermoluminescence dynamics during destruction of neon-helium and krypton-helium condensates containing stabilized nitrogen and oxygen atoms are presented. Spectra of the thermoluminescence of a krypton-helium condensate contained bands of N and O atoms and NO molecules. The intensities of the bands in these spectra were found to increase simultaneously during destruction processes in the temperature range 1.5-15 K. Observation of the NO molecules provides clear evidence for chemical reactions in the nanoclusters comprising the sample at low temperatures. Destruction of neon-helium samples occurred in two stages. During the first stage the α-group of N atoms surrounded by Ne and N2 molecules dominated the spectra. During the second stage, the spectra contained intense bands of N and O atoms stabilized in a molecular nitrogen matrix. The unusual characteristics of the thermoluminescence spectra were observed, and their changes were explained in terms of the shell structure of impurity nanoclusters which comprised the impurity-helium condensates.

  7. Classical trajectory Monte Carlo model calculations for the antiproton-induced ionization of atomic hydrogen at low impact energy

    CERN Document Server

    Sarkadi, L

    2015-01-01

    The three-body dynamics of the ionization of the atomic hydrogen by 30 keV antiproton impact has been investigated by calculation of fully differential cross sections (FDCS) using the classical trajectory Monte Carlo (CTMC) method. The results of the calculations are compared with the predictions of quantum mechanical descriptions: The semi-classical time-dependent close-coupling theory, the fully quantal, time-independent close-coupling theory, and the continuum-distorted-wave-eikonal-initial-state model. In the analysis particular emphasis was put on the role of the nucleus-nucleus (NN) interaction played in the ionization process. For low-energy electron ejection CTMC predicts a large NN interaction effect on FDCS, in agreement with the quantum mechanical descriptions. By examining individual particle trajectories it was found that the relative motion between the electron and the nuclei is coupled very weakly with that between the nuclei, consequently the two motions can be treated independently. A simple ...

  8. Antiproton radiotherapy

    CERN Document Server

    Bassler, Niels; Beyer, Gerd; DeMarco, John J.; Doser, Michael; Hajdukovic, Dragan; Hartley, Oliver; Iwamoto, Keisuke S.; Jakel, Oliver; Knudsen, Helge V.; Kovacevic, Sandra; Møller, Søren Pape; Overgaard, Jens; Petersen, Jørgen B.à; Solberg, Timothy D.; Sørensen, Brita S.; Vranjes, Sanja; Wouters, Bradly G.; Holzscheiter, Michael H.

    2008-01-01

    Antiprotons are interesting as a possible future modality in radiation therapy for the following reasons: When fast antiprotons penetrate matter, protons and antiprotons have near identical stopping powers and exhibit equal radiobiology well before the Bragg-peak. But when the antiprotons come to rest at the Bragg-peak, they annihilate, releasing almost 2 GeV per antiproton–proton annihilation. Most of this energy is carried away by energetic pions, but the Bragg-peak of the antiprotons is still locally augmented with ∼20–30 MeV per antiproton. Apart from the gain in physical dose, an increased relative biological effect also has been observed, which can be explained by the fact that some of the secondary particles from the antiproton annihilation exhibit high-LET properties. Finally, the weakly interacting energetic pions, which are leaving the target volume, may provide a real time feedback on the exact location of the annihilation peak. We have performed dosimetry experiments and investigated the rad...

  9. Antiproton production

    International Nuclear Information System (INIS)

    The results for the antiproton momentum spectrum produced in proton reactions on lead at the CERN Antiproton Accumulator is scaled to AGS operating conditions using the Sanford-Wang formula with no correction for target material. Yield predictions as a function of momentum are shown for 28.3 GeV protons on beryllium and results are converted to antiproton beam flux. The AGS Medium Energy Separated Beam has a flux which is a factor of 2 lower than Sanford-Wang predictions. This may be due to factors affecting beam acceptance

  10. Absolute number densities of helium metastable atoms determined by atomic absorption spectroscopy in helium plasma-based discharges used as ambient desorption/ionization sources for mass spectrometry

    International Nuclear Information System (INIS)

    The absolute number densities of helium atoms in the 2s 3S1 metastable state were determined in four plasma-based ambient desorption/ionization sources by atomic absorption spectroscopy. The plasmas included a high-frequency dielectric barrier discharge (HF-DBD), a low temperature plasma (LTP), and two atmospheric-pressure glow discharges, one with AC excitation and the other with DC excitation. Peak densities in the luminous plumes downstream from the discharge capillaries of the HF-DBD and the LTP were 1.39 × 1012 cm−3 and 0.011 × 1012 cm−3, respectively. Neither glow discharge produced a visible afterglow, and no metastable atoms were detected downstream from the capillary exits. However, densities of 0.58 × 1012 cm−3 and 0.97 × 1012 cm−3 were measured in the interelectrode regions of the AC and DC glow discharges, respectively. Time-resolved measurements of metastable atom densities revealed significant random variations in the timing of pulsed absorption signals with respect to the voltage waveforms applied to the discharges. - Highlights: • We determine He metastable number densities for four plasma types • The highest number densities were observed in a dielectric barrier discharge • No helium metastable atoms were observed downstream from the exits of glow discharges

  11. Lattice location and annealing behaviour of helium atoms implanted in uranium dioxide single crystals

    Science.gov (United States)

    Belhabib, T.; Desgardin, P.; Sauvage, T.; Erramli, H.; Barthe, M. F.; Garrido, F.; Carlot, G.; Nowicki, L.; Garcia, P.

    2015-12-01

    Helium behaviour in irradiated uranium dioxide may play an important role in the mechanical stability of nuclear fuels during and after its use in nuclear power plants. Helium migration mechanisms in bulk UO2 have already been the subject of theoretical studies but there is a lack of experimental data relating to the most stable location in the crystal. To this end, we have studied uranium dioxide samples implanted with helium ions at low fluence before and after thermal annealing in the range 600 and 800 °C. UO2 single crystals were implanted with 50 keV-3He ions at the fluence of 1 × 1015 at cm-2 and the location in the lattice of helium atoms was investigated using NRA (Nuclear Reaction Analysis) based on the reaction of 3He with deuterons (3He (d,p) 4He) in a channelling mode, recording angular scans across axes and planes. Furthermore, the uranium sub-lattice was analysed by the classical RBS method. After implantation, the experimental angular scans recorded across the main crystallographic axes and along major planes show that the helium atoms in their large majority occupy octahedral interstitial sites. No modification of the occupied crystallographic site was found after annealing at 600 °C. Conversely, no crystallographic relationship between matrix and helium signals was revealed following annealing at 800 °C. The latter feature is likely related to the clustering of implanted helium atoms into gas-filled bubbles. These experimental results have been quantified and interpreted using Monte Carlo simulations with the McChasy code.

  12. Line intensity ratios of helium atom in an ionizing plasma

    International Nuclear Information System (INIS)

    Effective emission rate coefficients Cemeff(λ), line intensity ratios, Cemeff(λ1)/Cemeff(λ2), and Seff/Cemeff(λ), with Seff the ionization rate coefficient, are obtained by the collisional radiative model for an ionizing plasma using new excitation and ionization rate coefficients. In the plasma with electron density ne > 104 cm-3, Cemeff(λ) for various lines are enlarged, since the normalized population densities for the metastable states, n(21,3S)/nHe, becomes large, and the excitation rate coefficients from 21,3S, C21,3S→i, are large compared to that from the ground state C11S→i. In high ne plasma (ne > 1012 cm-3), with frequent electron impacts on the excited heliums, n(i)/nHe become constant to ne, which results in the decrease of Cemeff(λ). Hot electrons and resonance scattering, which are often important for the experimental applications, are included in this model. A small amount of hot electrons (several percents) can enhance the line emission and ionization rates for low electron temperature plasma with Te (Te 1S - n1P) and enlarges n1P and 21S populations when the column density of helium gas nHe x L exceeds 2x1013 [cm-2]. (author)

  13. Resonant two-photon ionization spectroscopy of Al atoms and dimers solvated in helium nanodroplets

    International Nuclear Information System (INIS)

    Resonant two-photon ionization (R2PI) spectroscopy has been applied to investigate the solvation of Al atoms in helium droplets. The R2PI spectra reveal vibrational progressions that can be attributed to Al–Hen vibrations. It is found that small helium droplets have very little chance to pick up an aluminum atom after collision. However, the pick-up probability increases with the size of the helium droplets. The absorption band that is measured by monitoring the ions on the mass of the Al dimer is found to be very little shifted with respect to the Al monomer band (∼400 cm−1). However, using the same laser wavelength, we were unable to detect any Aln photoion with n larger than two

  14. ELASTIC AND INELASTIC HELIUM ATOM SCATTERING AT A CLEAVED MICA SHEET

    NARCIS (Netherlands)

    BRUSDEYLINS, G; SCHMICKER, D

    1995-01-01

    A mica sheet has been cleaved in situ in a UHV beam scattering apparatus. The diffraction of the helium atoms shows sharp Bragg peaks. In the [110] and [110] directions of the hexagonal surface the intensities of the Bragg peaks are analysed in terms of a sinusoidal corrugation. With hard wall scatt

  15. Helium in chirped laser fields as a time-asymmetric atomic switch

    Czech Academy of Sciences Publication Activity Database

    Kaprálová-Žďánská, Petra Ruth; Moiseyev, N.

    2014-01-01

    Roč. 141, č. 1 (2014), 014307. ISSN 0021-9606 R&D Projects: GA ČR GAP205/11/0571 Institutional support: RVO:61388955 Keywords : Atom lasers * Laser pulses * Helium Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.952, year: 2014

  16. The validity of Kinoshita's expansion for S-state eigenfunctions of the helium atom

    International Nuclear Information System (INIS)

    The incorrectness of an assertion by Kinoshita (Phys. Rev.; 105:1490 (1957)) of having found a set of variables in which helium atom eigenfunctions are analytic is demonstrated by making explicit an earlier statement of Fock (Izv. Akad. Nauk.; 18:161 (1954)). Some other flaws in Kinoshita's article are pointed out. (author)

  17. Excitation of the shear horizontal mode in a monolayer by inelastic helium atom scattering

    DEFF Research Database (Denmark)

    Bruch, L. W.; Hansen, Flemming Yssing

    2005-01-01

    Inelastic scattering of a low-energy atomic helium beam (HAS) by a physisorbed monolayer is treated in the one-phonon approximation using a time-dependent wave,packet formulation. The calculations show that modes with shear horizontal polarization can be excited near high symmetry azimuths of the...

  18. Calculation of inelastic helium atom scattering from H2/ NaCl(001)

    DEFF Research Database (Denmark)

    Bruch, L.W.; Hansen, Flemming Yssing; Traeger, F.

    2011-01-01

    The one-phonon inelastic low energy helium atom scattering theory is adapted to cases where the target monolayer is a p(1 × 1) commensurate square lattice. Experimental data for para-H2/NaCl(001) are re-analyzed and the relative intensities of energy loss peaks in the range 6 to 9 meV are determi...

  19. Atomic and molecular spectroscopy of transition metals in condensed helium

    International Nuclear Information System (INIS)

    Full text: We investigated laser induced fluorescence spectra of copper and gold atoms and dimers thereof isolated in solid and liquid 4He. Among the atomic spectral lines the most interesting ones are forbidden transitions that involve electrons from inner d-shells which are screened from the surrounding He atoms by the outer s-shell and are therefore much less affected by the interaction with the He matrix. Indeed, the observed spectral lineshapes are much narrower than those of transitions involving outer shell electrons. Another important result is the observation of well resolved vibrational structures in five molecular bands of the Au2 and Cu2 dimers. We expect that the analysis of those spectra will significantly advance our understanding of impurity atoms and molecules in condensed He. (author)

  20. Ultracold atomic collisions in tight harmonic traps: Perturbation theory, ionization losses and application to metastable helium atoms

    CERN Document Server

    Beams, T J; Whittingham, I B

    2004-01-01

    Collisions between tightly confined atoms can lead to ionization and hence to loss of atoms from the trap. We develop second-order perturbation theory for a tensorial perturbation of a spherically symmetric system and the theory is then applied to processes mediated by the spin-dipole interaction. Redistribution and loss mechanisms are studied for the case of spin-polarized metastable helium atoms and results obtained for the five lowest s states in the trap and trapping frequencies ranging from 1 kHz to 10 MHz.

  1. Proceedings of the 10 May 1989 Antiproton Technology Workshop: Addendum

    Science.gov (United States)

    Nordley, Gerald D.

    1989-09-01

    Antiprotons are particles of antimatter which release highly penetrating radiation when they are stopped in normal matter. According to presentations at the Antiproton Technology Workshop this radiation can be used, in very small quantities, to image objects and determine their composition and density. In larger amounts, the radiation could be used to kill cancer tumors or produce highly localized heating and shock waves. Titles of presentations include: Stopping Power of MeV Proton and Antiproton Beams; Recent Simulation Results of ASTER; Pbar Testing of Hydrogen Effects in Sealed Carbon-Carbon Composites; Potential for Antiprotons in Radiation Oncology; Prospects for a Commercial Antiproton Source; Prospects for Exciting Extreme States in Nuclear Matter with Intense Antiproton Beams; Status of AL Studies Relating to condensed Antimatter; Electromagnetic Traps for Atomic Antihydrogen; Antihydrogen Production; Antiproton Catalyzed Fusion; Antiproton Induced Fusion Reaction; Modeling Antiproton-Plasma Interactions; Introduction to CP Violation Studies with Pbars; and Antiproton Production Calculation by the Multistring Model VENUS.

  2. Theoretical and experimental study of the Stark effect in the ground state of alkali atoms in helium crystals

    OpenAIRE

    Ulzega, Simone; Weis, Antoine

    2007-01-01

    This thesis work describes a detailed study of the Stark interaction in the ground state of cesium atoms trapped in a solid helium matrix. The motivation for the investigation of electric field effects on alkali species implanted in solid helium is related to the original main goal of our experimental activities, i.e., the measurement of a permanent atomic electric dipole moment (EDM). The existence of an atomic EDM simultaneously violates the discrete symmetries of time reversal (T) and pari...

  3. The fine structure of niobium condensates deposited from ion-atomic fluxes in helium atmosphere

    International Nuclear Information System (INIS)

    Helium gas influence on the structural characteristics of niobium coatings deposited by low-energy metallic Nb ion-stoic fluxes in He atmosphere is investigated. It is shown that He implantation in Nb films during condensation is accompanied with the decreasing of the mean size of condensate grains. At the same time, He atoms modify no physical processes of the fine structure formation. Using thermodesorption spectroscopy we have determined that He atoms mainly belong to vacancy/vacancy-solute complexes in Nb coatings. Our conclusion is that such complexes play a dominant role in formation of the fine structure of vacuum coatings deposited from ion-atomic fluxes

  4. Laser spectroscopy of atoms in superfluid helium for the measurement of nuclear spins and electromagnetic moments of radioactive atoms

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, T., E-mail: tomomi.fujita@riken.jp [Osaka University, Department of Physics (Japan); Furukawa, T. [Tokyo Metropolitan University, Department of Physics (Japan); Imamura, K.; Yang, X. F. [RIKEN Nishina Center (Japan); Hatakeyama, A. [Tokyo University of Agriculture and Technology, Department of Applied Physics (Japan); Kobayashi, T. [RIKEN Center for Advanced Photonics (Japan); Ueno, H. [RIKEN Nishina Center (Japan); Asahi, K. [Tokyo Institute of Technology, Department of Physics (Japan); Shimoda, T. [Osaka University, Department of Physics (Japan); Matsuo, Y. [Hosei University, Department of Advanced Sciences (Japan); Collaboration: OROCHI Collaboration

    2015-11-15

    A new laser spectroscopic method named “OROCHI (Optical RI-atom Observation in Condensed Helium as Ion catcher)” has been developed for deriving the nuclear spins and electromagnetic moments of low-yield exotic nuclei. In this method, we observe atomic Zeeman and hyperfine structures using laser-radio-frequency/microwave double-resonance spectroscopy. In our previous works, double-resonance spectroscopy was performed successfully with laser-sputtered stable atoms including non-alkali Au atoms as well as alkali Rb and Cs atoms. Following these works, measurements with {sup 84−87}Rb energetic ion beams were carried out in the RIKEN projectile fragment separator (RIPS). In this paper, we report the present status of OROCHI and discuss its feasibility, especially for low-yield nuclei such as unstable Au isotopes.

  5. Laser spectroscopy of atoms in superfluid helium for the measurement of nuclear spins and electromagnetic moments of radioactive atoms

    International Nuclear Information System (INIS)

    A new laser spectroscopic method named “OROCHI (Optical RI-atom Observation in Condensed Helium as Ion catcher)” has been developed for deriving the nuclear spins and electromagnetic moments of low-yield exotic nuclei. In this method, we observe atomic Zeeman and hyperfine structures using laser-radio-frequency/microwave double-resonance spectroscopy. In our previous works, double-resonance spectroscopy was performed successfully with laser-sputtered stable atoms including non-alkali Au atoms as well as alkali Rb and Cs atoms. Following these works, measurements with 84−87Rb energetic ion beams were carried out in the RIKEN projectile fragment separator (RIPS). In this paper, we report the present status of OROCHI and discuss its feasibility, especially for low-yield nuclei such as unstable Au isotopes

  6. Controlled Reactions between Ultracold Alkali and Metastable Helium Atoms

    CERN Document Server

    Flores, Adonis Silva; Knoop, Steven

    2016-01-01

    In an ultracold, optically trapped mixture of $^{87}$Rb and metastable triplet $^4$He atoms we have studied trap loss for different spin-state combinations, for which interspecies Penning ionization is the main two-body loss process. We observe long trapping lifetimes for the purely quartet spin-state combination, indicating strong suppression of Penning ionization loss by at least two orders of magnitude. For the other spin-mixtures we observe short lifetimes that depend linearly on the doublet character of the entrance channel. We compare the extracted loss rate coefficient with recent predictions of multichannel quantum-defect theory for reactive collisions involving a strong exothermic loss channel and find near-universal loss for doublet scattering. Our work demonstrates control of reactive collisions by internal atomic state preparation, which also implies magnetic field tunability.

  7. Radial correlation limits of helium and heliumlike atoms

    International Nuclear Information System (INIS)

    Radial correlation limits of two-electron atoms with atomic numbers Z=1-10 are calculated by using modified Kinoshita wave functions in which all the parameters are optimized. The optimal Kinoshita functions show a rapid energy convergence with the increasing number N of constituent terms, and the radial energies convergent to 10 significant figures are obtained. The results show that both the calculated and estimated values of the radial correlation limits in the literature are insufficiently accurate. In the case of He, for example, the present calculation gives -2.879 028 764 hartrees with N=40, while the best literature value is -2.879 028 6 hartrees. (orig.). With 3 tabs

  8. Production of a Bose Einstein condensate of metastable helium atoms

    Science.gov (United States)

    Santos, F. Pereira Dos; Léonard, J.; Wang, Junmin; Barrelet, C. J.; Perales, F.; Rasel, E.; Unnikrishnan, C. S.; Leduc, M.; Cohen-Tannoudji, C.

    2003-04-01

    We recently observed a Bose-Einstein condensate in a dilute gas of 4He in the 23S1 metastable state. In this article, we describe the successive experimental steps which led to the Bose-Einstein transition at 4.7 μK: loading of a large number of atoms in a MOT, efficient transfer into a magnetic Ioffé-Pritchard trap, and optimization of the evaporative cooling ramp. Quantitative measurements are also given for the rates of elastic and inelastic collisions, both above and below the transition.

  9. Atomic delay in helium, neon, argon and krypton

    International Nuclear Information System (INIS)

    Photoionization by an eXtreme UltraViolet (XUV) attosecond pulse train (APT) in the presence of an infrared pulse (RABBITT method) conveys information about the atomic photoionization delay. By taking the difference of the spectral delays between pairs of rare gases (Ar,He), (Kr,He) and (Ne,He) it is possible to eliminate in each case the larger group delay (‘attochirp’) associated with the APT itself and obtain the Ar, Kr and Ne Wigner delays referenced to model calculations of the He delay. In this work we measure how the delays vary as a function of XUV photon energy but we cannot determine the absolute delay difference between atoms due to lack of precise knowledge of the initial conditions. The extracted delays are compared with several theoretical predictions and the results are consistent within 30 as over the energy range from 10 to 50 eV. An ‘effective’ Wigner delay over all emission angles is found to be more consistent with our angle-integrated measurement near the Cooper minimum in Ar. We observe a few irregular features in the delay that may be signatures of resonances. (paper)

  10. Atomic delay in helium, neon, argon and krypton

    Science.gov (United States)

    Palatchi, Caryn; Dahlström, J. M.; Kheifets, A. S.; Ivanov, I. A.; Canaday, D. M.; Agostini, P.; DiMauro, L. F.

    2014-12-01

    Photoionization by an eXtreme UltraViolet (XUV) attosecond pulse train (APT) in the presence of an infrared pulse (RABBITT method) conveys information about the atomic photoionization delay. By taking the difference of the spectral delays between pairs of rare gases (Ar,He), (Kr,He) and (Ne,He) it is possible to eliminate in each case the larger group delay (‘attochirp’) associated with the APT itself and obtain the Ar, Kr and Ne Wigner delays referenced to model calculations of the He delay. In this work we measure how the delays vary as a function of XUV photon energy but we cannot determine the absolute delay difference between atoms due to lack of precise knowledge of the initial conditions. The extracted delays are compared with several theoretical predictions and the results are consistent within 30 as over the energy range from 10 to 50 eV. An ‘effective’ Wigner delay over all emission angles is found to be more consistent with our angle-integrated measurement near the Cooper minimum in Ar. We observe a few irregular features in the delay that may be signatures of resonances. .

  11. Creation evidence of the second non-dispersive Zakharenko wave by helium atomic beams in superfluid helium-II at low temperatures

    Indian Academy of Sciences (India)

    A A Zakharenko

    2007-10-01

    In this work, the experimental results of the creation of the second non-dispersive Zakharenko wave (ph = g ≠ 0) in the negative roton branch (the so-called second sound) of the bulk elementary excitations (BEEs) energy spectra are introduced. Several BEE signals detected by a bolometer situated in the isotopically pure liquid helium-II at low temperatures ∼ 100 mK are shown, which give evidence of negative roton creation in the liquid by helium atomic beams striking the liquid surface. The negative roton signals were clearly distinguished by the following ways: the negative roton signal created by helium atomic beams appeared earlier than the positive roton signal created by the beams, and presence of both positive and negative roton signals together. It is natural that the negative roton creation by the beams requires the 4He-atom energies ∼ 12 K, while the positive roton creation by the atomic beams requires energies ∼ 35 K. Therefore, successive increase in the heater power resulting in an increase in the 4He-atom energies gives solid evidence that the negative rotons are first created in the liquid by the helium atomic beams.

  12. Performance of Hyperspherical Harmonic Expansionon the Low-lying Pand D States of Helium Atom

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The wave functions of the n 1,3P (n=2,3,4) and the n 1,3D (n=3,4,5) low-lying states ofthe helium atom are expanded into the complete sets of the symmetrically adapted basis functionsfrom hyperspherical harmonic functions in the angle part and of generalized Laguerre functions inthe radial part respectively, and are then augmented by the simplest type of Jastrow correlationfactor to incorporate electron-nucleus cusp only. The excellent agreement between the presentnonrelativistic eigen-energies and those from the sophisticated configuration interaction (CI)method for the examined states indicates that the hyperspherical harmonic method can also be applied to the P and the D excited states of the helium atom.

  13. Antiproton Target

    CERN Multimedia

    1980-01-01

    Antiproton target used for the AA (antiproton accumulator). The first type of antiproton production target used from 1980 to 1982 comprised a rod of copper 3mm diameter and 120mm long embedded in a graphite cylinder that was itself pressed into a finned aluminium container. This assembly was air-cooled and it was used in conjunction with the Van der Meer magnetic horn. In 1983 Fermilab provided us with lithium lenses to replace the horn with a view to increasing the antiproton yield by about 30%. These lenses needed a much shorter target made of heavy metal - iridium was chosen for this purpose. The 50 mm iridium rod was housed in an extension to the original finned target container so that it could be brought very close to the entrance to the lithium lens. Picture 1 shows this target assembly and Picture 2 shows it mounted together with the lithium lens. These target containers had a short lifetime due to a combination of beam heating and radiation damage. This led to the design of the water-cooled target in...

  14. The Antiproton Accumulator becomes Antiproton Decelerator

    CERN Multimedia

    1980-01-01

    The photos show the Antiproton Accumulator (AA) transformed into Antiproton Decelerator. The AA was used at CERN between 1981 and 1999 before being replaced by the Antiproton Decelerator (AD). The AA was used to collect and stochastically cool antiprotons used in proton-antiproton collisions in the SPS collider. This lead to the discovery of the W and Z bosons in 1983 and the Nobel Prize for Carlo Rubbia and Simon van der Meer in 1984.

  15. Visualization of steps and surface reconstructions in Helium Ion Microscopy with atomic precision.

    Science.gov (United States)

    Hlawacek, Gregor; Jankowski, Maciej; Wormeester, Herbert; van Gastel, Raoul; Zandvliet, Harold J W; Poelsema, Bene

    2016-03-01

    Helium Ion Microscopy is known for its surface sensitivity and high lateral resolution. Here, we present results of a Helium Ion Microscopy based investigation of a surface confined alloy of Ag on Pt(111). Based on a change of the work function of 25meV across the atomically flat terraces we can distinguish Pt rich from Pt poor areas and visualize the single atomic layer high steps between the terraces. Furthermore, dechanneling contrast has been utilized to measure the periodicity of the hcp/fcc pattern formed in the 2-3 layers thick Ag/Pt alloy film. A periodicity of 6.65nm along the 〈11¯2〉 surface direction has been measured. In terms of crystallography a hcp domain is obtained through a lateral displacement of a part of the outermost layer by 1/3 of a nearest neighbor spacing along 〈11¯2〉. This periodicity is measured with atomic precision: coincidence between the Ag and the Pt lattices is observed for 23 Ag atoms on 24 Pt atoms. The findings are perfectly in line with results obtained with Low Energy Electron Microscopy and Phase Contrast Atomic Force Microscopy. PMID:26720438

  16. Characterization of the Plasma Edge for Technique of Atomic Helium Beam in the CIEMAT Fusion Device

    International Nuclear Information System (INIS)

    In this report, the measurement of Electron Temperature and Density in the Boundary Plasma of TJ-II with a Supersonic Helium Beam Diagnostic and work devoted to the upgrading of this technique are described. Also, simulations of Laser Induced Fluorescence (LIF) studies of level populations of electronically excited He atoms are shown. This last technique is now being installed in the CIEMAT fusion device. (Author )

  17. Energy levels in helium and neon atoms by an electron-impact method

    Science.gov (United States)

    Taylor, N.; Bartle, K. D.; Mills, D.; Beard, D. S.

    1981-03-01

    Electronic energy levels in noble gas atoms may be determined with a simple teaching apparatus incorporating a resonance potentials tube in which the electron beam intensity is held constant. The resulting spectra are little inferior to those obtained by more elaborate electron-impact methods and complement optical emission spectra. Singlet-triplet energy differences may be resolved, and the spectra of helium and neon may be used to illustrate the applicability of Russell-Saunders and other, ''intermediate,'' coupling schemes.

  18. Quantized vortices in superfluid helium and atomic Bose-Einstein condensates

    OpenAIRE

    Tsubota, Makoto; Kasamatsu, Kenichi; Kobayashi, Michikazu

    2010-01-01

    This article reviews recent developments in the physics of quantized vortices in superfluid helium and atomic Bose-Einstein condensates. Quantized vortices appear in low-temperature quantum condensed systems as the direct product of Bose-Einstein condensation. Quantized vortices were first discovered in superfluid 4He in the 1950s, and have since been studied with a primary focus on the quantum hydrodynamics of this system. Since the discovery of superfluid 3He in 1972, quantized vortices cha...

  19. Continuous Compressed Sensing for Surface Dynamical Processes with Helium Atom Scattering

    Science.gov (United States)

    Jones, Alex; Tamtögl, Anton; Calvo-Almazán, Irene; Hansen, Anders

    2016-06-01

    Compressed Sensing (CS) techniques are used to measure and reconstruct surface dynamical processes with a helium spin-echo spectrometer for the first time. Helium atom scattering is a well established method for examining the surface structure and dynamics of materials at atomic sized resolution and the spin-echo technique opens up the possibility of compressing the data acquisition process. CS methods demonstrating the compressibility of spin-echo spectra are presented for several measurements. Recent developments on structured multilevel sampling that are empirically and theoretically shown to substantially improve upon the state of the art CS techniques are implemented. In addition, wavelet based CS approximations, founded on a new continuous CS approach, are used to construct continuous spectra. In order to measure both surface diffusion and surface phonons, which appear usually on different energy scales, standard CS techniques are not sufficient. However, the new continuous CS wavelet approach allows simultaneous analysis of surface phonons and molecular diffusion while reducing acquisition times substantially. The developed methodology is not exclusive to Helium atom scattering and can also be applied to other scattering frameworks such as neutron spin-echo and Raman spectroscopy.

  20. Metastable helium atom density in a single electrode atmospheric plasma jet during sample treatment

    Science.gov (United States)

    Zaplotnik, R.; Bišćan, M.; Popović, D.; Mozetič, M.; Milošević, S.

    2016-06-01

    The metastable He atoms play an important role in atmospheric pressure plasma jet (APPJ) chemistry processes and in the plasma generation. This work presents cavity ring-down spectroscopy (CRDS) investigation of metastable helium atom (2{{3}}{{S}1} ) densities in a single electrode APPJ during sample treatment. A spatially resolved density distribution of a free jet (without sample) was measured at a He flow rate of 2 slm. The maximum measured density of a free jet was around 7× {{10}11} cm‑3. With the insertion of a sample the densities increased up to 10 times. Helium metastable atoms, in a single electrode helium APPJ (2 slm, ≈2.5 kV, pulsed DC, 10 kHz repetition rate), decayed exponentially with a mean lifetime of 0.27+/- 0.03 μs. Eight different samples of the same sizes but different conductivities were used to investigate the influence of a sample material on the He metastable densities. The correlation between sample conductivities and metastable He densities above the sample surface was found. Metastable He density can also be further increased with decreasing sample distance, increasing conductive sample surface area and by increasing He flow.

  1. Continuous Compressed Sensing for Surface Dynamical Processes with Helium Atom Scattering.

    Science.gov (United States)

    Jones, Alex; Tamtögl, Anton; Calvo-Almazán, Irene; Hansen, Anders

    2016-01-01

    Compressed Sensing (CS) techniques are used to measure and reconstruct surface dynamical processes with a helium spin-echo spectrometer for the first time. Helium atom scattering is a well established method for examining the surface structure and dynamics of materials at atomic sized resolution and the spin-echo technique opens up the possibility of compressing the data acquisition process. CS methods demonstrating the compressibility of spin-echo spectra are presented for several measurements. Recent developments on structured multilevel sampling that are empirically and theoretically shown to substantially improve upon the state of the art CS techniques are implemented. In addition, wavelet based CS approximations, founded on a new continuous CS approach, are used to construct continuous spectra. In order to measure both surface diffusion and surface phonons, which appear usually on different energy scales, standard CS techniques are not sufficient. However, the new continuous CS wavelet approach allows simultaneous analysis of surface phonons and molecular diffusion while reducing acquisition times substantially. The developed methodology is not exclusive to Helium atom scattering and can also be applied to other scattering frameworks such as neutron spin-echo and Raman spectroscopy. PMID:27301423

  2. Continuous Compressed Sensing for Surface Dynamical Processes with Helium Atom Scattering

    Science.gov (United States)

    Jones, Alex; Tamtögl, Anton; Calvo-Almazán, Irene; Hansen, Anders

    2016-01-01

    Compressed Sensing (CS) techniques are used to measure and reconstruct surface dynamical processes with a helium spin-echo spectrometer for the first time. Helium atom scattering is a well established method for examining the surface structure and dynamics of materials at atomic sized resolution and the spin-echo technique opens up the possibility of compressing the data acquisition process. CS methods demonstrating the compressibility of spin-echo spectra are presented for several measurements. Recent developments on structured multilevel sampling that are empirically and theoretically shown to substantially improve upon the state of the art CS techniques are implemented. In addition, wavelet based CS approximations, founded on a new continuous CS approach, are used to construct continuous spectra. In order to measure both surface diffusion and surface phonons, which appear usually on different energy scales, standard CS techniques are not sufficient. However, the new continuous CS wavelet approach allows simultaneous analysis of surface phonons and molecular diffusion while reducing acquisition times substantially. The developed methodology is not exclusive to Helium atom scattering and can also be applied to other scattering frameworks such as neutron spin-echo and Raman spectroscopy. PMID:27301423

  3. Study of helium and beryllium atoms with strong and short laser field; Etude des atomes d'helium et de beryllium en champ laser intense et bref

    Energy Technology Data Exchange (ETDEWEB)

    Laulan, St

    2004-09-01

    We present a theoretical study of the interaction between a two-active electron atom and an intense (10{sup 14} to 10{sup 15} W/cm{sup 2}) and ultrashort (from a few 10{sup -15} to a few 10{sup -18} s) laser field. In the first part, we describe the current experimental techniques able to produce a coherent radiation of high power in the UV-XUV regime and with femtosecond time duration. A theoretical model of a laser pulse is defined with such characteristics. Then, we develop a numerical approach based on B-spline functions to describe the atomic structure of the two-active electron system. A spectral non perturbative method is proposed to solve the time dependent Schroedinger equation. We focalize our attention on the description of the atomic double continuum states. Finally, we expose results on the double ionization of helium and beryllium atoms with intense and short laser field. In particular, we present total cross section calculations and ejected electron energy distributions in the double continuum after one- and two-photon absorption. (author)

  4. Negative ion productions in high velocity collision between small carbon clusters and Helium atom target

    International Nuclear Information System (INIS)

    We measured absolute double capture cross section of Cn+ ions (n=1,5) colliding, at 2.3 and 2.6 a.u velocities, with an Helium target atom and the branching ratios of fragmentation of the so formed electronically excited anions Cn−*. We also measured absolute cross section for the electronic attachment on neutral Cn clusters colliding at same velocities with He atom. This is to our knowledge the first measurement of neutral-neutral charge exchange in high velocity collision.

  5. Measurement of the hyperfine splitting of {sup 133}Cs atoms in superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Imamura, K., E-mail: kimamura@riken.jp [RIKEN Nishina Center (Japan); Furukawa, T. [Tokyo Metropolitan University, Department of Physics (Japan); Yang, X. F. [Peking University, School of Physics (China); Mitsuya, Y. [Meiji University, Department of Physics (Japan); Fujita, T. [Osaka University, Department of Physics (Japan); Hayasaka, M. [Tokyo Gakugei University, Department of Physics (Japan); Kobayashi, T. [RIKEN Center for Advanced Photonics (Japan); Hatakeyama, A. [Tokyo University of Agriculture and Technology, Department of Applied Physics (Japan); Ueno, H. [RIKEN Nishina Center (Japan); Odashima, H. [Meiji University, Department of Physics (Japan); Matsuo, Y. [Hosei University, Department of Advanced Sciences (Japan)

    2015-04-15

    We have been developing a new nuclear laser spectroscopy method named “OROCHI” (Optical RI-atom Observation in Condensed Helium as Ion-catcher). OROCHI utilizes superfluid helium (He II) not only as an efficient stopping medium of highly energetic ions but also as a host matrix of in-situ atomic laser spectroscopy. Using these characteristic of He II, we produce atomic spin polarization and measure Zeeman and hyperfine structure (HFS) splitting using laser-RF (radio frequency) / MW (microwave) double resonance method. From the measured energy splittings, we can deduce nuclear spins and moments. So far, we have conducted a series of experiments using both stable ({sup 85,87}Rb, {sup 133}Cs, {sup 197}Au, {sup 107,109}Ag) and unstable isotopes ({sup 84,86}Rb) to confirm the feasibility of OROCHI method, especially observing Zeeman resonance and determining nuclear spins. The measurement of HFS splitting of atoms introduced into He II is indispensable to clarify the nuclear properties by deducing nuclear moments as well as the study of nuclear spins. For this purpose, we perform a precision measurement of HFS of {sup 133}Cs atoms immersed in He II using laser ablation technique. In this paper, we describe the result of the experiment.

  6. Measurement of the hyperfine splitting of 133Cs atoms in superfluid helium

    International Nuclear Information System (INIS)

    We have been developing a new nuclear laser spectroscopy method named “OROCHI” (Optical RI-atom Observation in Condensed Helium as Ion-catcher). OROCHI utilizes superfluid helium (He II) not only as an efficient stopping medium of highly energetic ions but also as a host matrix of in-situ atomic laser spectroscopy. Using these characteristic of He II, we produce atomic spin polarization and measure Zeeman and hyperfine structure (HFS) splitting using laser-RF (radio frequency) / MW (microwave) double resonance method. From the measured energy splittings, we can deduce nuclear spins and moments. So far, we have conducted a series of experiments using both stable (85,87Rb, 133Cs, 197Au, 107,109Ag) and unstable isotopes (84,86Rb) to confirm the feasibility of OROCHI method, especially observing Zeeman resonance and determining nuclear spins. The measurement of HFS splitting of atoms introduced into He II is indispensable to clarify the nuclear properties by deducing nuclear moments as well as the study of nuclear spins. For this purpose, we perform a precision measurement of HFS of 133Cs atoms immersed in He II using laser ablation technique. In this paper, we describe the result of the experiment

  7. Prospects for precision measurements of atomic helium using direct frequency comb spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Eyler, E.E.; Chieda, D.E. [Connecticut Univ., Physics Dept., Storrs, CT (United States); Stowe, M.C.; Thorpe, M.J.; Schibli, T.R.; Ye, J. [Colorado Univ., Dept. of Physics, JILA, National Institute of Standards and Technology, Boulder, CO (United States)

    2008-06-15

    We analyze several possibilities for precisely measuring electronic transitions in atomic helium by the direct use of phase-stabilized femtosecond frequency combs. Because the comb is self-calibrating and can be shifted into the ultraviolet spectral region via harmonic generation, it offers the prospect of greatly improved accuracy for UV and far-UV transitions. To take advantage of this accuracy an ultracold helium sample is needed. For measurements of the triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap metastable 2{sup 3}S state atoms. We analyze schemes for measuring the two-photon 2{sup 3}S {yields} 4{sup 3}S interval, and for resonant two-photon excitation to high Rydberg states, 2{sup 3}S {yields} 3{sup 3}P {yields} n{sup 3}S, D. We also analyze experiments on the singlet-state spectrum. To accomplish this we propose schemes for producing and trapping ultracold helium in the 1{sup 1}S or 2{sup 1}S state via intercombination transitions. A particularly intriguing scenario is the possibility of measuring the 1{sup 1}S {yields} 2{sup 1}S transition with extremely high accuracy by use of two-photon excitation in a magic wavelength trap that operates identically for both states. We predict a 'triple magic wavelength' at 412 nm that could facilitate numerous experiments on trapped helium atoms, because here the polarizabilities of the 1{sup 1}S, 2{sup 1}S and 2{sup 3}S states are all similar, small, and positive. (authors)

  8. Investigation of isotopically-selective laser collinear photoionization of accelerated helium atoms

    International Nuclear Information System (INIS)

    Results are presented of investigations of collinear two-step laser photoionization of 3He and 4He isotopes accelerated to energies up to 3.9 keV. It is shown that selectivity of ionization of the rare isotope 3He is 106 for a residual vacuum in the system fo 10-7 mm Hg. It is limited by collision processes leading to the excitation of fast metastable atoms into Rydberg state in the field-free region and to impact ionization of the fast atoms in the region of the ionizer. The ionization of fast Rydberg atoms in a transverse electric field is investigated. It is shown that the ionization of helium atoms excited into the n3D states proceeds via adiabatic and diabatic channels

  9. Prospects for precision measurements of atomic helium using direct frequency comb spectroscopy

    CERN Document Server

    Eyler, E E; Stowe, Matthew C; Thorpe, Michael J; Schibli, T R; Ye, Jun

    2007-01-01

    We analyze several possibilities for precisely measuring electronic transitions in atomic helium by the direct use of phase-stabilized femtosecond frequency combs. Because the comb is self-calibrating and can be shifted into the ultraviolet spectral region via harmonic generation, it offers the prospect of greatly improved accuracy for UV and far-UV transitions. To take advantage of this accuracy an ultracold helium sample is needed. For measurements of the triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap metastable $2 ^3S$ state atoms. We analyze schemes for measuring the two-photon $2 ^3S \\to 4 ^3S$ interval, and for resonant two-photon excitation to high Rydberg states, $2 ^3S \\to 3 ^3P \\to n^3S,D$. We also analyze experiments on the singlet-state spectrum. To accomplish this we propose schemes for producing and trapping ultracold helium in the $1 ^1S$ or $2 ^1S$ state via intercombination transition. A particularly intriguing scenario is the possibility of direct singlet state sp...

  10. Penning and dissociative ionizations of methane molecules in collisions with metastable helium atoms

    International Nuclear Information System (INIS)

    Measurements of relative ion production yields in the Penning and dissociative ionizations of methane molecules on impact of metastable helium atoms have been carried out using a new crossed-beam apparatus, ''Perfectron''. Due to the perfect focusing property of the perfectron, the total ion yield as well as differential ion yield of each reaction channel can be measured. Though the measurement is at present only preliminary and no attempt is made to discriminate between 21S and 23S states in the primary helium beam, obtained spectra are in good agreement with those of Cermak et. al. and of Herce et. al. in the measurement of total ion yields. The CH3+ ions are most abundant in contrast with electron impact where the parent CH4+ ions predominate. On the other hand, in the measurement of differential ion yields at 00 with respect to the methane beam, the parent CH4+ ions slightly predominate over the fragment CH3+ ions. (author)

  11. Three-body interactions in the condensed phases of helium atom systems

    International Nuclear Information System (INIS)

    In this work we investigate how the description of several properties of helium atoms in the condensed phases are affected by the three-body terms of a very accurate inter-atomic potential. We introduce two phenomenological parameters in the three-body part of the inter-atomic potential in order to describe properly the equations of state of the solid and liquid phases. The calculations were performed using the multi-weight extension to the diffusion Monte Carlo method which allows accurate calculations of small energy differences in a significant way. The results show how the equations of state for both the liquid and solid phases and properties like the isothermal compressibility, the equilibrium, melting and freezing densities are affected by three-body interactions

  12. Focussing a helium atom beam by reflection from a concave surface

    International Nuclear Information System (INIS)

    Results of 1-dimensional focussing of a Helium-atom beam reflected from a concave, cylindrical surface are presented. The atomic beam is created by a supersonic expansion and collimated by a skimmer and two slits, variable in size (5-20 μm). For grazing incident angles of a few milliradian the beam is coherently reflected by quantum reflection. Beam profiles at the focus are measured by cutting off the intensity by scanning a knife edge with a piezo (analogy to waist measurement by a razor blade in laser optics). The width of the focus is limited by the source size, by spherical aberration and by diffraction effects. We tune the deBroglie-wavelength by changing the temperature of the atom beam source to see how diffraction influences the focus' width and shape. The smallest focus achieved so far is 1.0±0.1 μm

  13. Ultra-sensitive atomic magnetometer for studying magnetization fields produced by hyperpolarized helium-3

    Science.gov (United States)

    Zou, Sheng; Zhang, Hong; Chen, Xi-yuan; Chen, Yao; Lu, Ji-xi; Hu, Zhao-hui; Shan, Guang-cun; Quan, Wei; Fang, Jian-cheng

    2016-04-01

    An ingenious approach to acquire the absolute magnetization fields produced by polarized atoms has been presented in this paper. The method was based on detection of spin precession signal of the hyperpolarized helium-3 with ultra-sensitive atomic magnetometer of potassium by referring to time-domain analysis. At first, dynamic responses of the mixed spin ensembles in the presence of variant external magnetic fields have been analyzed by referring to the Bloch equation. Subsequently, the relevant equipment was established to achieve the functions of hyperpolarizing helium-3 and detecting the precession of spin-polarized noble gas. By analyzing the transient response of the magnetometer in time domain, we obtained the relevant damping ratio and natural frequency. When the value of damping ratio reached the maximum value of 0.0917, the combined atomic magnetometer was in equilibrium. We draw a conclusion from the steady response: the magnetization fields of the polarized electrons and the hyperpolarized nuclei were corresponding 16.12 nT and 90.74 nT. Under this situation, the nuclear magnetization field could offset disturbing magnetic fields perpendicular to the orientation of the electronic polarization, and it preserved the electronic spin staying in a stable axis. Therefore, the combined magnetometer was particularly attractive for inertial measurements.

  14. Electron emission in collisions of fast highly charged bare ions with helium atoms

    Science.gov (United States)

    Mondal, Abhoy; Mandal, Chittranjan; Purkait, Malay

    2016-01-01

    We have studied the electron emission from ground state helium atom in collision with fast bare heavy ions at intermediate and high incident energies. In the present study, we have applied the present three-body formalism of the three Coulomb wave (3C-3B) model and the previously adopted four-body formalism of the three Coulomb wave (3C-4B). To represent the active electron in the helium atom in the 3C-3B model, the initial bound state wavefunction is chosen to be hydrogenic with an effective nuclear charge. The wavefunction for the ejected electron in the exit channel has been approximated to be a Coulomb continuum wavefunction with same effective nuclear charge. Effectively the continuum-continuum correlation effect has been considered in the present investigation. Here we have calculated the energy and angular distribution of double differential cross sections (DDCS) at low and high energy electron emission from helium atom. The large forward-backward asymmetry is observed in the angular distribution which is explained in terms of the two-center effect (TCE). Our theoretical results are compared with available experimental results as well as other theoretical calculations based on the plain wave Born approximation (PWBA), continuum-distorted wave (CDW) approximation, continuum-distorted wave eikonal-initial state (CDW-EIS) approximation, and the corresponding values obtained from the 3C-4B model [S. Jana, R. Samanta, M. Purkait, Phys. Scr. 88, 055301 (2013)] respectively. It is observed that the four-body version of the present investigation produces results which are in better agreement with experimental observations for all cases.

  15. Spin-statistic selection rules for multiphoton transitions: Application to helium atoms

    Science.gov (United States)

    Zalialiutdinov, T.; Solovyev, D.; Labzowsky, L.; Plunien, G.

    2016-01-01

    A theoretical investigation of the three-photon transition rates 2 1P1→2 1S0,1 1S0 and 2 3P2→2 1S0,1 1S0 for the helium atom is presented. Photon energy distributions and precise values of the nonrelativistic transition rates are obtained with employment of correlated wave functions of the Hylleraas type. The possible experiments for the tests of the Bose-Einstein statistics for multiphoton systems are discussed.

  16. Spin-Statistic Selection Rules for Multiphoton Transitions: Application to Helium Atom

    CERN Document Server

    Zalialiutdinov, T; Labzowsky, L; Plunien, G

    2016-01-01

    A theoretical investigation of the three-photon transition rates $ 2^1P_1\\rightarrow 2^1S_0\\;,1^1S_0 $ and $ 2^3P_2\\rightarrow 2^1S_0\\;,1^1S_0 $ for the helium atom is presented. Photon energy distributions and precise values of the nonrelativistic transition rates are obtained with employment of correlated wave functions of the Hylleraas type. The possible experiments for the tests of the Bose-Einstein statistics for multiphoton systems are discussed.

  17. Monte Carlo calculation of the Born-Oppenheimer potential between two helium atoms

    International Nuclear Information System (INIS)

    Fully correlated Hylleraas-type electronic wave functions and a biased-selection Monte Carlo method have been used to find a rigorous upper bound to the Born-Oppenheimer potential between two helium atoms. The potential agrees with the experimental results of Burgmans, Farrar, and Lee (BFL) to within 1.4 Monte Carlo standard deviations for all nuclear separation distances calculated (4.5--15.0a/sub B/). At the potential minimum of 5.6a/sub B/ this bound (-7.10 +- 0.30 Ry) is slightly below the BFL value of -6.70 Ry

  18. Monte Carlo calculation of the Born-Oppenheimer potential between two helium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Lowther, R.E.; Coldwell, R.L.

    1980-07-01

    Fully correlated Hylleraas-type electronic wave functions and a biased-selection Monte Carlo method have been used to find a rigorous upper bound to the Born-Oppenheimer potential between two helium atoms. The potential agrees with the experimental results of Burgmans, Farrar, and Lee (BFL) to within 1.4 Monte Carlo standard deviations for all nuclear separation distances calculated (4.5--15.0a/sub B/). At the potential minimum of 5.6a/sub B/ this bound (-7.10 +- 0.30 Ry) is slightly below the BFL value of -6.70 Ry.

  19. Hylleraas-Configuration Interaction calculations on the 1 ^1S ground state of helium atom

    OpenAIRE

    Ruiz, Maria Belen

    2012-01-01

    Hylleraas-Configuration Interaction (Hy-CI) calculations on the ground $1^1$S state of helium atom are presented using s-, p-, d-, and f-Slater orbitals of both real and complex form. Techniques of construction of adapted configurations, optimization of the orbital exponents and structure of the wave function expansion are explored. A new method to evaluate the two-electron kinetic energy integrals occurring in the Hy-CI method has been tested here and compared with other methods. The non-rel...

  20. Electron correlation in fast ion-impact single ionization of helium atoms

    International Nuclear Information System (INIS)

    A four-body distorted-wave approximation is applied for theoretical analysis of the fully differential cross sections (FDCS) for proton-impact single ionization of helium atoms in their ground states. The nine-dimensional integrals for the partial amplitudes are analytically reduced to closed-form expressions or some one-dimensional integrals which can be easily calculated numerically. Calculations are performed in the scattering and perpendicular planes. The influence of the target static electron correlations on the process is investigated using a number of different bound-state wave functions for the ground state of the helium targets. An illustrative computation is performed for 75-keV proton-helium collisions and the obtained results are compared with experimental data and other theoretical predictions. Although for small momentum transfers, the comparison shows a reasonable agreement with experiments in the scattering and perpendicular planes, some significant discrepancies are still present at large momentum transfers in these planes. However, our results are compatible and for some cases, better than those of the other sophisticated calculations. (paper)

  1. Radiative and non-radiative electron capture from carbon atoms by relativistic helium ions

    International Nuclear Information System (INIS)

    Interaction of radiation with helium atoms and/or ions is of interest in various astrophysical applications. The reverse reactions of fast 150 MeV/amu 3He++ ions with solid C targets have been studied at the isochronous cyclotron of the RCNP in Osaka. The singly ionized helium ions resulting from capture of the target electrons to the projectile were observed with the use of large magnetic spectrograph, Grand Raiden, set at θ = 0 deg with respect to the beam. The yield ratios of singly to doubly ionized helium ions emerging from thin foils, He+/He++, have been measured as a function of the foil thickness. Extrapolating the results to zero target thickness permits to determine the cross section values separately for electron stripping from 3He+ ions and for electron capture to 3He++ ions. The radiative and non-radiative contributions to the capture cross section were determined in a separate experiment which the 84 keV (C.M.) photons were observed in coincidence with the He+ ejectiles. The results are compared with theoretical predictions. (author)

  2. Antiproton Cancer Therapy

    DEFF Research Database (Denmark)

    Bassler, Niels

    Antiprotons are interesting as a modality in radiation therapy for the following reasons: When fast antiprotons penetrate matter, they behave as protons. Well before the Bragg-peak, protons and antiprotons have near identical stopping powers exhibit equal radiobiology. But when the antiprotons co...

  3. Measurement of interaction between antiprotons

    Czech Academy of Sciences Publication Activity Database

    Adamczyk, L.; Bielčík, J.; Bielčíková, Jana; Federič, Pavol; Chaloupka, P.; Rusňák, Jan; Rusňáková, O.; Šimko, Miroslav; Šumbera, Michal; Tlustý, David; Trzeciak, B. A.; Vértési, Robert

    2015-01-01

    Roč. 527, č. 7578 (2015), s. 345-348. ISSN 0028-0836 R&D Projects: GA ČR GA13-20841S Institutional support: RVO:61389005 Keywords : STAR collaboration * antiprotons * protons Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 41.456, year: 2014

  4. Quantum interference in attosecond transient absorption of laser-dressed helium atoms

    CERN Document Server

    Chen, Shaohao; Gaarde, Mette B; Schafer, Kenneth J

    2013-01-01

    We calculate the transient absorption of an isolated attosecond pulse by helium atoms subject to a delayed infrared (\\ir) laser pulse. With the central frequency of the broad attosecond spectrum near the ionization threshold, the absorption spectrum is strongly modulated at the sub-\\ir-cycle level. Given that the absorption spectrum results from a time-integrated measurement, we investigate the extent to which the delay-dependence of the absorption yields information about the attosecond dynamics of the atom-field energy exchange. We find two configurations in which this is possible. The first involves multi photon transitions between bound states that result in interference between different excitation pathways. The other involves the modification of the bound state absorption lines by the IR field, which we find can result in a sub-cycle time dependence only when ionization limits the duration of the strong field interaction.

  5. Cross section database for collision processes of helium atom with charged particles. 1. Electron impact processes

    International Nuclear Information System (INIS)

    A comprehensive and critically assessed cross section database for the inelastic collision processes of ground state and excited helium atoms colliding with electrons, protons and multiply-charged ions has been prepared at the Data and Planning Center at NIFS. The present report describes the first part of the database containing the recommended data for electron impact excitation and ionization of neutral helium. An states (atomic terms) with n ≤ 4 are treated individually while the states with n > 4 are considered degenerate. For the processes involving transitions to and from n > 4 levels, suitable cross section scaling relations are presented. For a large number of electron impact transitions, both from the ground and excited states, new convergent close coupling (CCC) calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in a graphical form. (author)

  6. Velocity dependence of the absolute total ionization cross section for collisions of argon atoms with singlet and triplet metastable helium atoms

    International Nuclear Information System (INIS)

    Measurements of the velocity dependence of the absolute total ionization cross section of argon atoms upon impact with selected metastable states of helium atoms are reported. A low voltage dc discharge was used as the source of the excited atoms, and a rotating slotted disk selector was used for velocity selection of the excited atoms. Selection of the electronic spin state of the excited atoms was accomplished by irradiation of the excited atoms with radiation from a helium discharge lamp. Ionization of the argon target atoms by metastable helium atoms was studied by the gas cell technique in which all ionization products were collected. The ionization measurements were of sufficient precision to allow simultaneous determination of the cross section and the second electron ejection efficiency for each metastable state of helium. The secondary electron ejection efficiency of triplet metastable helium atoms on an electroplated gold surface was determined to be 0.440 +- 0.018 in the presence of argon gas. The secondary electron ejection efficiency of singlet metastable atoms was determined to be 0.582 +- 0.024 under similar conditions. The total ionization cross section for the He(23S)-Ar system was found to increase almost linearly from 8.8 to 21.95 A2 with an increase of relative velocity from 1162 to 2787 m/sec. After an initial increase of the cross section from 9.8 A2 to 26.2 A2 with an increase in relative velocity from 989 m/sec to 2058 m/sec, the velocity dependence of the cross section of the He(21S)-Ar system entered a saturation region in which the cross section changed very little with relative velocity. The collision energy dependence of the He(23S)-Ar system was also used to determine the values of adjustable parameters present in a current theory based on the potential curve model for Penning and associative Penning ionization

  7. Temperature and Atomic Oxygen Effects on Helium Leak Rates of a Candidate Main Interface Seal

    Science.gov (United States)

    Penney, Nicholas; Wasowski, Janice L.; Daniels, Christopher C.

    2011-01-01

    Helium leak tests were completed to characterize the leak rate of a 54 in. diameter composite space docking seal design in support of the National Aeronautics and Space Administration s (NASA's) Low Impact Docking System (LIDS). The evaluated seal design was a candidate for the main interface seal on the LIDS, which would be compressed between two vehicles, while docked, to prevent the escape of breathable air from the vehicles and into the vacuum of space. Leak tests completed at nominal temperatures of -30, 20, and 50 C on untreated and atomic oxygen (AO) exposed test samples were examined to determine the influence of both test temperature and AO exposure on the performance of the composite seal assembly. Results obtained for untreated seal samples showed leak rates which increased with increased test temperature. This general trend was not observed in tests of the AO exposed specimens. Initial examination of collected test data suggested that AO exposure resulted in higher helium leak rates, however, further analysis showed that the differences observed in the 20 and 50 C tests between the untreated and AO exposed samples were within the experimental error of the test method. Lack of discernable trends in the test data prevented concrete conclusions about the effects of test temperature and AO exposure on helium leak rates of the candidate seal design from being drawn. To facilitate a comparison of the current test data with results from previous leak tests using air as the test fluid, helium leak rates were converted to air leak rates using standard conversion factors for viscous and molecular flow. Flow rates calculated using the viscous flow conversion factor were significantly higher than the experimental air leakage values, whereas values calculated using the molecular flow conversion factor were significantly lower than the experimentally obtained air leak rates. The difference in these sets of converted flow rates and their deviation from the

  8. Measurement of interaction between antiprotons

    CERN Document Server

    ,

    2015-01-01

    One of the primary goals of nuclear physics is to understand the force between nucleons, which is a necessary step for understanding the structure of nuclei and how nuclei interact with each other. Rutherford discovered the atomic nucleus in 1911, and the large body of knowledge about the nuclear force since acquired was derived from studies made on nucleons or nuclei. Although antinuclei up to antihelium-4 have been discovered and their masses measured, we have no direct knowledge of the nuclear force between antinucleons. Here, we study antiproton pair correlations among data taken by the STAR experiment at the Relativistic Heavy Ion Collider and show that the force between two antiprotons is attractive. In addition, we report two key parameters that characterize the corresponding strong interaction: namely, the scattering length (f0) and effective range (d0). As direct information on the interaction between two antiprotons, one of the simplest systems of antinucleons, our result provides a fundamental ingr...

  9. Temperature dependence of the formation rates of hydrogen-helium mesic molecules in collisions of slow hydrogen atoms with helium

    International Nuclear Information System (INIS)

    Muon transfer from the ground state of the muonic hydrogen to helium is of special interest, since it is connected with problem of muon-catalyzed fusion in the deuterium-tritium mixture. The muon transfer rates are calculated at low energy collisions of hydrogen isotopes with helium isotopes. The calculations are carried out in an improved adiabatic approximation. The particular attention is given to the construction of the effective potential. The level energies ε00 and ε10 of the hydrogen-helium muonic molecules are presented. For collision energies ε ≤ 0.1 eV rate of the direct muon transfer does not depend on energy and amounts to λ pHe ∼ 0.06 x 108 s-1. The theoretical results λ obtained by various temperatures are compared with the available experimental data

  10. Study of helium and beryllium atoms with strong and short laser field

    International Nuclear Information System (INIS)

    We present a theoretical study of the interaction between a two-active electron atom and an intense (1014 to 1015 W/cm2) and ultrashort (from a few 10-15 to a few 10-18 s) laser field. In the first part, we describe the current experimental techniques able to produce a coherent radiation of high power in the UV-XUV regime and with femtosecond time duration. A theoretical model of a laser pulse is defined with such characteristics. Then, we develop a numerical approach based on B-spline functions to describe the atomic structure of the two-active electron system. A spectral non perturbative method is proposed to solve the time dependent Schroedinger equation. We focalize our attention on the description of the atomic double continuum states. Finally, we expose results on the double ionization of helium and beryllium atoms with intense and short laser field. In particular, we present total cross section calculations and ejected electron energy distributions in the double continuum after one- and two-photon absorption. (author)

  11. Penning and dissociative ionizations of methane molecules in collisions with metastable helium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Arikawa, Tatsuo; Kanazawa, Ken-ichi; Tsurubuchi, Seiji (Tokyo Univ. of Agriculture and Technology, Koganei (Japan). Faculty of Technology)

    1983-06-01

    Measurements of relative ion production yields in the Penning and dissociative ionizations of methane molecules on impact of metastable helium atoms have been carried out using a new crossed-beam apparatus, ''Perfectron''. Due to the perfect focusing property of the perfectron, the total ion yield as well as differential ion yield of each reaction channel can be measured. Though the measurement is at present only preliminary and no attempt is made to discriminate between 2/sup 1/S and 2/sup 3/S states in the primary helium beam, obtained spectra are in good agreement with those of Cermak et. al. and of Herce et. al. in the measurement of total ion yields. The CH/sub 3//sup +/ ions are most abundant in contrast with electron impact where the parent CH/sub 4//sup +/ ions predominate. On the other hand, in the measurement of differential ion yields at 0/sup 0/ with respect to the methane beam, the parent CH/sub 4//sup +/ ions slightly predominate over the fragment CH/sub 3//sup +/ ions.

  12. Bielectron interaction in helium atom and the corresponding spectral statistical fluctuation properties

    International Nuclear Information System (INIS)

    The spectral fluctuation properties of a quantum system are related closely to the dynamical symmetries of the system and its nonlinearity but not dependent upon number of the degrees of freedom. The energy spectrum of Helium atom is calculated, and by analysing the spectral fluctuations it is found that the residual one pair electron-electron interaction is not sufficient to change the dynamical symmetry of the nucleus-electron central field, eventhough the interaction is amplified artificially to a possible extent (as far as the dissociation of the system does not occur). It turns out that the contour plot of the potential intuitively gives the information about the symmetry of the system and indicates the degree of the symmetry breaking as well as the way how the symmetry is lost

  13. Laser absorption spectroscopy diagnostics of helium metastable atoms generated in dielectric barrier discharge cryoplasmas

    Science.gov (United States)

    Urabe, Keiichiro; Muneoka, Hitoshi; Stauss, Sven; Sakai, Osamu; Terashima, Kazuo

    2015-10-01

    Cryoplasmas, which are plasmas whose gas temperatures are below room temperature (RT), have shown dynamic changes in their physical and chemical characteristics when the gas temperature in the plasmas (Tgp) was decreased from RT. In this study, we measured the temporal behavior of helium metastable (Hem) atoms generated in a parallel-plate dielectric barrier discharge at ambient gas temperatures (Tga) of 300, 100, and 14 K and with a gas density similar to atmospheric conditions by laser absorption spectroscopy. The increments of Tgp to Tga were less than 20 K. We found from the results that the Hem lifetime and maximum density become longer and larger over one order of magnitude for lower Tga. The reasons for the long Hem lifetime at low Tga are decreases in the rate coefficients of three-body Hem quenching reactions and in the amounts of molecular impurities with boiling points higher than that of He.

  14. Learning Approach on the Ground State Energy Calculation of Helium Atom

    International Nuclear Information System (INIS)

    This research investigated the role of learning approach on the ground state energy calculation of Helium atom in improving the concepts of science teachers at university level. As the exact solution of several particles is not possible here we used approximation methods. Using this method one can understand easily the calculation of ground state energy of any given function. Variation Method is one of the most useful approximation methods in estimating the energy eigen values of the ground state and the first few excited states of a system, which we only have a qualitative idea about the wave function.The objective of this approach is to introduce and involve university teacher in new research, to improve their class room practices and to enable teachers to foster critical thinking in students.

  15. Single ionization of helium atoms by energetic fully stripped carbon ions

    Institute of Scientific and Technical Information of China (English)

    Ebrahim Ghanbari-Adivi; Sadjad Eskandari

    2015-01-01

    A four-body distorted wave approximation is presented for theoretical investigations of the single ionization of ground-state helium atoms by fully stripped carbon ions at impact energies of 2 MeV/amu and 100 MeV/amu. The nine-dimensional integrals for the partial quantum-mechanical transition amplitudes of the specified reaction are reduced to some analytical expressions or one-dimensional integrals over real variables. Fully differential cross sections (FDCSs) are calculated and compared with their experimental values as well as the results obtained from other theories. Despite the simplicity and quickness of the proposed quadrature, the comparison shows that the obtained results are in reasonable agreement with the experiment and are compatible with those of other complicated theories.

  16. Uncoupled correlated variational function in (e, 2e) and (e, 3e) calculations for ionization of the helium atom

    CERN Document Server

    Chuluunbaatar, O; Vinitsky, S I

    2002-01-01

    The uncoupled correlated variational function of the helium atom ground state declared earlier is examined in calculations of differential cross sections of fast electron impact single and double binary ionization processes. An optimal one-parametric set of orthogonal basic functions is generated to provide the considerable coincidence with the experiment and calculations with the alternative multiparametric trial wave functions.

  17. Antiproton-Decelerator (AD)

    CERN Multimedia

    Laurent Guiraud

    1998-01-01

    When the Low-Energy Antiproton Ring (LEAR) was stopped in 1996, because of its costly operation, a cheaper way of continuing low-energy antiproton physics was sought. The Antiproton-Collector (AC), added in 1987 to the Antiproton Accumulator (AA) to provide a tenfold intensity increase, was converted into the Antiproton-Decelerator (AD). Antiprotons from the target at 3.5 GeV/c are decelerated to 100 MeV/c, and fast-ejected to the experiments. Major changes were necessary. Above all, the conversion from a constant-field machine to one with a magnetic cycle, modulating the field by an impressive factor 35. New systems for stochastic and electron cooling had to be added. Beam diagnostics at an intensity of only 2E7 antiprotons was a challenge. In 2000, the AD began delivery of antiprotons to the experiments.

  18. Antiproton Accumulator (AA)

    CERN Multimedia

    Photographic Service

    1980-01-01

    The AA in its final stage of construction, before it disappeared from view under concrete shielding. Antiprotons were first injected, stochastically cooled and accumulated in July 1980. From 1981 on, the AA provided antiprotons for collisions with protons, first in the ISR, then in the SPS Collider. From 1983 on, it also sent antiprotons, via the PS, to the Low-Energy Antiproton Ring (LEAR). The AA was dismantled in 1997 and shipped to Japan.

  19. Antiprotons get biological

    CERN Multimedia

    2003-01-01

    After its final run in September, the first results of the Antiproton Cell Experiment (ACE) look very promising. It was the first experiment to take data on the biological effects of antiproton beams to evaluate the potential of antiprotons in radiation therapy.

  20. Physics with ultra-low energy antiprotons

    International Nuclear Information System (INIS)

    The experimental observation that all forms of matter experience the same gravitational acceleration is embodied in the weak equivalence principle of gravitational physics. However no experiment has tested this principle for particles of antimatter such as the antiproton or the antihydrogen atom. Clearly the question of whether antimatter is in compliance with weak equivalence is a fundamental experimental issue, which can best be addressed at an ultra-low energy antiproton facility. This paper addresses the issue. 20 refs

  1. Low Energy Antiproton Experiments -- A Review

    OpenAIRE

    Jungmann, Klaus P.

    2005-01-01

    Low energy antiprotons offer excellent opportunities to study properties of fundamental forces and symmetries in nature. Experiments with them can contribute substantially to deepen our fundamental knowledge in atomic, nuclear and particle physics. Searches for new interactions can be carried out by studying discrete symmetries. Known interactions can be tested precisely and fundamental constants can be extracted from accurate measurements on free antiprotons ($\\bar{p}$'s) and bound two- and ...

  2. Polarization of antiprotons by antiproton decay

    International Nuclear Information System (INIS)

    The production of polarized antiproton beams at Fermilab is briefly reviewed. Two types of high-energy anti p polarimeters are described - the Coulomb-nuclear polarimeter and the Primakoff-effect polarimeter. The production of 8.9 GeV/c polarized antiprotons before entering the Fermilab accumulator ring is then discussed. 5 refs., 6 figs

  3. Calculations of Electron Structure of Endohedrally Confined Helium Atom with B-Spline Type Functions

    Institute of Scientific and Technical Information of China (English)

    QIAO HaoXue; SHI TingYun; LI BaiWen

    2002-01-01

    The B-spline basis set method is used to study the properties of helium confined endohedrally at thegeometrical centre of a fullerene. The boundary conditions of the wavefunctions can be simply satisfied with thismethod. From our results, the phenomenon of "mirror collapse" is found in the case of confining helium. The interestingbehaviors of confining helium are also discussed.

  4. Antiproton Radiotherapy Peripheral Dose from Secondary Neutrons produced in the Annihilation of Antiprotons in the Target

    CERN Document Server

    Fahimian, Benjamin P; Keyes, Roy; Bassler, Niels; Iwamoto, Keisuke S; Zankl, Maria; Holzscheiter, Michael H

    2009-01-01

    The AD-4/ACE collaboration studies the biological effects of antiprotons with respect to a possible use of antiprotons in cancer therapy. In vitro experiments performed by the collaboration have shown an enhanced biological effectiveness for antiprotons relative to protons. One concern is the normal tissue dose resulting from secondary neutrons produced in the annihilation of antiprotons on the nucleons of the target atoms. Here we present the first organ specific Monte Carlo calculations of normal tissue equivalent neutron dose in antiproton therapy through the use of a segmented CT-based human phantom. The MCNPX Monte Carlo code was employed to quantify the peripheral dose for a cylindrical spread out Bragg peak representing a treatment volume of 1 cm diameter and 1 cm length in the frontal lobe of a segmented whole-body phantom of a 38 year old male. The secondary neutron organ dose was tallied as a function of energy and organ.

  5. Four-body charge transfer processes in collisions of bare projectile ions with helium atoms

    Science.gov (United States)

    Jana, S.; Mandal, C. R.; Purkait, M.

    2015-02-01

    Single-electron capture by a bare ion from a helium atom at intermediate and high energies in the framework of four-body distorted wave (DW-4B) approximation in both prior and post form has been considered. In the entrance channel, the initial bound state wave function is distorted by the incoming projectile ion, and the corresponding distortion is related to the Coulomb continuum states of the active electron and the residual target ion in the field of the projectile ion respectively. Continuum states of the active electron and the projectile ion in the field of the residual target ion are also included in the exit channel. It may be mentioned that the effect of dynamic electron correlation is explicitly taken into account through the complete perturbation potential. The total single-electron capture cross sections are obtained by summing over all contributions up to n = 3 shells and sub-shells respectively. In addition, the differential cross sections for alpha particle-helium collision are calculated at impact energies of 60, 150, 300, 450, and 630 keV amu-1, respectively. The cross sections exhibit a monotonically decreasing angular dependence, with clear peak structures around 0.1 to 0.2 mrad being found at low impact energies. The current theoretical results, both in prior and post forms of the transition amplitude for symmetric and asymmetric collision, are compared with the available theoretical and experimental results. Current computed results have been found to be satisfactory in comparison with other theoretical and experimental findings.

  6. Four-body charge transfer processes in collisions of bare projectile ions with helium atoms

    International Nuclear Information System (INIS)

    Single-electron capture by a bare ion from a helium atom at intermediate and high energies in the framework of four-body distorted wave (DW-4B) approximation in both prior and post form has been considered. In the entrance channel, the initial bound state wave function is distorted by the incoming projectile ion, and the corresponding distortion is related to the Coulomb continuum states of the active electron and the residual target ion in the field of the projectile ion respectively. Continuum states of the active electron and the projectile ion in the field of the residual target ion are also included in the exit channel. It may be mentioned that the effect of dynamic electron correlation is explicitly taken into account through the complete perturbation potential. The total single-electron capture cross sections are obtained by summing over all contributions up to n = 3 shells and sub-shells respectively. In addition, the differential cross sections for alpha particle–helium collision are calculated at impact energies of 60, 150, 300, 450, and 630 keV amu−1, respectively. The cross sections exhibit a monotonically decreasing angular dependence, with clear peak structures around 0.1 to 0.2 mrad being found at low impact energies. The current theoretical results, both in prior and post forms of the transition amplitude for symmetric and asymmetric collision, are compared with the available theoretical and experimental results. Current computed results have been found to be satisfactory in comparison with other theoretical and experimental findings. (paper)

  7. Antiproton Focus Horn

    CERN Multimedia

    1974-01-01

    Was used for the AA (antiproton accumulator). Making an antiproton beam took a lot of time and effort. Firstly, protons were accelerated to an energy of 26 GeV in the PS and ejected onto a metal target. From the spray of emerging particles, a magnetic horn picked out 3.6 GeV antiprotons for injection into the AA through a wide-aperture focusing quadrupole magnet.For a million protons hitting the target, just one antiproton was captured, 'cooled' and accumulated. It took 3 days to make a beam of 3 x 10^11 -, three hundred thousand million - antiprotons.

  8. Helium clusters as cold, liquid matrix for the laser spectroscopy of silver atoms, silver clusters and C60 fullerenes

    International Nuclear Information System (INIS)

    One of the main obstacles in the study of gas phase metal clusters is their high temperature. Even cooling in a seeded beam is only of limited used, since the condensation continuously releases energy into the system. As a consequence, spectroscopic studies of free metal clusters typically yield broad structures, which are interpreted as plasma resonances of a free electron gas. An experiment on ionic sodium clusters has shown that low temperatures lead to a narrowing of the absorption bands and the appearance of additional structure, that can not be explained within the free electron model. Thus the need for cold clusters is evident. In principle the deposition of metal clusters into inert matrices eliminates the temperature problem but it can also inflict strong changes on the electronic spectra. Droplets of liquid helium serve as a much more gentle matrix that avoids many of the above problems. In this thesis the new technique of helium droplet spectroscopy is presented as a tool for the study of extremely cold metal clusters. Clusters of silver up to a mass greater than 7000 amu have been produced by pickup of single atoms by a beam of helium droplets. The droplets are formed in a supersonic expansion. The cluster's binding energy is removed by evaporative cooling and the system remains at 0.4 K. The doped droplets are probed by laser spectroscopy with a depletion technique or resonant two photon ionization. We were able to measure the first UV absorption spectrum of metal atoms (silver) inside helium droplets. Another experiment shows that a small fraction of the captured silver atoms resides on the surface of the droplet like alkali atoms. In a two photon process previously unobserved s- and d-Rydberg states of the free silver atom (20 left angle n left angle 80) were excited. The silver atoms, initially embedded in the helium droplets, are found to move to the surface and desorb when excited to the broadened 5p level. This is the first result showing laser

  9. Interaction of antiproton with nuclei

    Czech Academy of Sciences Publication Activity Database

    Hrtánková, Jaroslava; Mareš, Jiří

    Vol. 234. Dordrecht: Springer, 2015, s. 93-98. ISSN 0304-3843. [5th International Conference on Exotic Atoms and Related Topics (EXA). Vienna (AT), 15.09.2014-19.09.2014] R&D Projects: GA ČR(CZ) GAP203/12/2126 Institutional support: RVO:61389005 Keywords : antiproton-nucleus interaction * RMF model * G-parity Subject RIV: BE - Theoretical Physics

  10. Measurement of the Antiprotonic Lyman- and Balmer X-rays of $\\overline{p}H$ and $\\overline{p}D$ Atoms at Very Low Target Pressures

    CERN Multimedia

    2002-01-01

    The aim of this experiment is to measure the energies and intensities of the n @A 1 (Lyman) and n @A 2 (Balmer) tansitions with high accuracy in both @*H and @*D, from which the strong interaction effects of the 1s- and 2p-level can be extracted. These observables may be related to the antiproton-proton and antiproton-neutron scattering length. \\\\ \\\\ Since in these targets collisional Stark effect occurs, we will stop the antiprotons in extreme thin gaseous targets (pressure as low as 10 Torr), where no Stark effect occurs and the 2-1 transition is favoured. In order to use antiprotons with high efficiency despite of the low target density, we will trap antiprotons of a momentum of 100 MeV/c in a magnetic field of cyclotron characteristics. The antiprotons are decelerated by their energy loss in the target gas. The focusing properties of the magnetic field serve to compensate the multiple scattering and we will end up with a concentrated stopping distribution at the centre. Due to the long orbiting time, back...

  11. Prospects for Antiproton Experiments at Fermilab

    CERN Document Server

    Kaplan, Daniel M

    2011-01-01

    Fermilab operates the world's most intense antiproton source. Newly proposed experiments can use those antiprotons either parasitically during Tevatron Collider running or after the end of the Tevatron Collider program. For example, the annihilation of 5 to 8 GeV antiprotons is expected to yield world-leading sensitivities to hyperon rare decays and CP violation. It could also provide the world's most intense source of tagged D^0 mesons, and thus the best near-term opportunity to study charm mixing and, via CP violation, to search for new physics. Other measurements that could be made include properties of the X(3872) and the charmonium system. An experiment using a Penning trap and an atom interferometer could make the world's most precise measurement of the gravitational force on antimatter. These and other potential measurements using antiprotons offer a great opportunity for a broad and exciting physics program at Fermilab in the post-Tevatron era.

  12. Proceedings of the Antiproton Technology Workshop held in Upton, New York on 10 May 1989

    Science.gov (United States)

    Nordley, Gerald D.

    1989-05-01

    Titles of presentations included: Stopping Power of MeV Proton and Antiproton Beams; Recent Simulation Results of ASTER; Pbar Testing of Hydrogen Effects in Sealed Carbon-Carbon Composites; Potential for Antiprotons in Radiation Oncology; Prospects for a Commercial Antiproton Source; Prospects for Exciting Extreme States in Nuclear Matter with Intense Antiproton Beams; Status of AL Studies Relating to Condensed Antimatter; Electromagnetic Traps for Atomic Antihydrogen; Antihydrogen Production; Headquarters DoE Antiproton Activities; Antiproton Catalyzed Fusion; Antiproton Induced Fusion Reaction; Options for a Laboratory Microfusion Facility; Modeling Antiproton-Plasma Interactions; Concepts for Experimental Determination of Radiation Shielding and Metal Clad Pellet Performance; Introduction to CP Violation Studies with Pbars; Search for CP Violation in Pbar-P to J/psi; Studies of Rare Models of Pbar-P Annihilation; and Antiproton Production Calculation by the Multistring Model VENUS Computer Code.

  13. Surface Structure of Lithium Doped Potassium Tantalate (KLT) using Helium Atom Scattering.

    Energy Technology Data Exchange (ETDEWEB)

    Fatema, Rifat [Florida State University; Van Winkle, David [Florida State University; Skofronick, J. G. [Florida State University; Sanfron, Sanford a [Department of Chemistry and Biochemistry, Florida State University; Flaherty, F. A. [Valdosta State University, Valdosta, GA; Boatner, Lynn A [ORNL

    2013-01-01

    The structures of the (001) surface of potassium tantalate doped with nominally 2, 4 and 7% lithium have been investigated using high resolution helium atom scattering. The surfaces were prepared by cleaving single crystal samples in situ under UHV conditions. Diraction measurements in the region around the He specular re ection angle soon after cleaving yielded specular peaks initially with broad shoulders. However, over a period of about an hour, the widths of these specular peaks decreased markedly as the shoulders diminished into the background. Drift spectra measurements of the stabilized surfaces revealed that the step heights separating surface terraces were predominantly multiples of the cubic unit cell dimension, about 4A, rather than multiples of a half unit cell, 2A, expected from the cleaving of these crystals. Together these results suggest that after cleaving these surfaces are rapidly modied by migration of ions to the surface from the near-surface. Further, half-order diraction peaks were observed in the <100> azimuth a short time after cleaving samples at room temperature, indicating that domains with (21) structure had formed.

  14. Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps

    Institute of Scientific and Technical Information of China (English)

    WANG Ji-Cheng; ZHOU Ke-Ya; WANG Yue-Yuan; LIAO Qing-Hong; LIU Shu-Tian

    2011-01-01

    We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using 87 Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap. The loss rates from the magneto-optic trap and the pure magnetic trap are compared and show significant differences. The collision cross sections as a function of trap depth for helium gas are obtained. These findings are significant for extracting the information about the different cross sections when the trap depth is changed.%@@ We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using 87Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap.The loss rates from the magneto-optic trap and the pure magnetic trap are compared and show significant differences.The collision cross sections as a function of trap depth for helium gas are obtained.These findings are significant for extracting the information about the different cross sections when the trap depth is changed.

  15. Thermal equilibrium/disequilibrium features in the excited-state temperature of atomic helium in MAP-II divertor simulator

    International Nuclear Information System (INIS)

    Doppler–Stark spectrometry and laser Thomson scattering diagnostics for helium plasmas were applied to the MAP-II (material and plasma) steady-state linear divertor simulator at the University of Tokyo. In recombining plasmas, as the volumetric recombination proceeded, atomic, ionic and electron temperatures converged to the same values, which indicated the achievement of thermal equilibrium. On the other hand, in ionizing plasmas, in addition to the collisional heating of bulk atoms, excess heating of atoms in the high principal quantum number states (above Griem’s boundary) was observed. This disequilibrium feature can be attributed to the presence of two prevailing conditions: that the characteristic time of the charge-exchange process of the atoms with ions in the system became shorter than the lifetime of the excited atoms spent above Griem’s boundary, and that the population influx from above Griem’s boundary is considerably larger than that from below the boundary

  16. Single and double electron capture cross sections in keV-collisions between fully stripped ions with helium atom

    OpenAIRE

    Ibaaz, Aicha; Dubois, Alain

    2015-01-01

    International audience We present cross section calculations for single-, double-capture, and double capture to auto-ionizing states occurring in the course of collisions between fully stripped ions Aq+ (q≤10) and helium atom at impact energies ranging from 0.25 to 625 keV/u. These calculations were performed by applying a semiclassical nonperturbative close coupling approach, based on the expansion of the scattering wave function into asymptotic bielectronic states with proper translation...

  17. Hyperspherical partial wave calculation for double photoionization of the helium atom at 20 eV excess energy

    International Nuclear Information System (INIS)

    The hyperspherical partial wave approach has been applied here in the study of double photoionization of the helium atom for equal-energy-sharing geometries at 20 eV excess energy. Calculations have been done both in length and velocity gauges and are found to agree with each other, with the CCC results and with experiments and to exhibit some advantages for the corresponding three-particle wavefunction over other wavefunctions in use

  18. Hyperspherical partial wave theory for photo double ionization of the helium atom at 20 eV excess energy

    CERN Document Server

    Das, J N; Paul, S

    2003-01-01

    Hyperspherical partial wave theory has been applied here in the study of photo double ionization of the helium atom for equal energy sharing geometry at 20 eV excess energy. Calculations have been done both in length and velocity gauges and are found to agree nicely with each other, with the CCC results and with experiments and exhibit some advantages of the corresponding three particle wave function over other wave functions in use.

  19. The CERN antiproton collector

    International Nuclear Information System (INIS)

    The Antiproton Collector is a new ring of much larger acceptance than the present accumulator. It is designed to receive 108 antiprotons per PS cycle. In order to be compatible with the Antiproton Accumulator, the momentum spread and the emittances are reduced from 6% to 0.2% and from 200 π mm mrad to 25 π mm mrad respectively. In addition to the ring itself, the new target area and the modifications to the stochastic systems of the Antiproton Accumulator are described. (orig.)

  20. Time evolution of cascade processes of muonic atoms in hydrogen-helium mixtures

    International Nuclear Information System (INIS)

    Time dependence of population of muonic hydrogen states in hydrogen-helium mixtures is calculated for principal quantum number n. Number of muons transferred to helium nuclei is also determined. Dependence of population of the ground state of muonic hydrogen qlsHe on time and target density and helium concentration is also considered. The results are in agreement with recent experimental data. The comparison of the calculated yield of K lines of x-ray in pure hydrogen and deuterium with experimental data indicates on essential role of Coulomb de-excitation process. Possible Stark mixing is also analyzed

  1. Neutrons from Antiproton Irradiation

    DEFF Research Database (Denmark)

    Bassler, Niels; Holzscheiter, Michael; Petersen, Jørgen B.B.

    relative biological effect (RBE) has already been beam measured in spread out Bragg peaks of antiprotons, relative to that found in the plateau region. However, the antiproton annihilation process is associated with a substantial release of secondary particles which contribute to the dose outside the...

  2. LEAR: antiproton extraction lines

    CERN Multimedia

    Photographic Service

    1992-01-01

    Antiprotons, decelerated in LEAR to a momentum of 100 MeV/c (kinetic energy of 5.3 MeV), were delivered to the experiments in an "Ultra-Slow Extraction", dispensing some 1E9 antiprotons over times counted in hours. Beam-splitters and a multitude of beam-lines allowed several users to be supplied simultaneously.

  3. Antiproton Radiation Therapy

    DEFF Research Database (Denmark)

    Bassler, Niels; Holzscheiter, Michael H.; Petersen, Jørgen B.B.

    2007-01-01

    investigated the radiobiological properties using antiprotons at 50 and 125 MeV from the Antiproton Decelerator (AD) at CERN. Dosimetry experiments were carried out with ionization chambers, alanine pellets and radiochromic film. Radiobiological experiments were done with Chinese V79 WNRE hamster cells. Monte...

  4. Ionization and excitation of Rydberg states in collisions of fast metastable helium atoms with He, Ne, and N2

    International Nuclear Information System (INIS)

    The experimental values of the cross sections of elementary collision processes involving neutral atoms and covering the energy range 01.-1,000 keV are of interest because they can be used to model some phenomena which occur under laboratory conditions and in outer space, and also to check the precision of various models and methods used in the theory of atomic collisions. The latter task is particularly important at moderate collision energies (usually below 100 keV) where the Born approximation for the cross sections of collisional processes gives results greatly at variance with the experimental data and the precision of the more complex theoretical methods being developed at present requires a careful experimental check. Here, the cross sections for ionization and excitation into Rydberg states (n = 21-27) were determined for fast (accelerated to 3.9 keV) metastable helium atoms colliding with He, Ne, and N2. An analysis of the collisionally excited helium atoms in terms of their principal quantum number was carried out using for the ionization by an electric field a system capable of separation in accordance with n and was calibrated using signals from Rydberg states excited selectively by laser radiation

  5. Antiprotons at Solar Maximum

    CERN Document Server

    Bieber, J W; Engel, R; Gaisser, T K; Roesler, S; Stanev, T; Bieber, John W.; Engel, Ralph; Gaisser, Thomas K.; Roesler, Stefan; Stanev, Todor

    1999-01-01

    New measurements with good statistics will make it possible to observe the time variation of cosmic antiprotons at 1 AU through the approaching peak of solar activity. We report a new computation of the interstellar antiproton spectrum expected from collisions between cosmic protons and the interstellar gas. This spectrum is then used as input to a steady-state drift model of solar modulation, in order to provide predictions for the antiproton spectrum as well as the antiproton/proton ratio at 1 AU. Our model predicts a surprisingly large, rapid increase in the antiproton/proton ratio through the next solar maximum, followed by a large excursion in the ratio during the following decade.

  6. Real-time evolution of a laser-dressed Helium atom: Attosecond-resolved two-color photoionization study

    CERN Document Server

    Shivaram, Niranjan; Tong, Xiao-Min; Sandhu, Arvinder S

    2011-01-01

    Using extreme-ultraviolet attosecond-pulse-trains, we investigate the photoionization dynamics of a Helium atom in the presence of moderately-strong (~10^12 W/cm^2) femtosecond laser pulses. The electronic structure of a laser-dressed atom is traced in real-time through precision measurements of ion-yields and photo-electron angular distributions. Quantum interferences between photo-excitation paths are interpreted using the Floquet formalism. As the laser pulse intensity ramps on femtosecond timescales, we observe transitions between ionization channels mediated by different atomic resonances. The quantum phase of interfering paths is extracted for each channel and compared with simulations. Our results elucidate photoionization mechanisms in strong-fields and open the doors for photo-absorption/ionization control schemes.

  7. Modified oscillator approach to ultracold collisions in tight harmonic traps General model and application to metastable helium atoms

    CERN Document Server

    Peach, G; Beams, T J; Peach, Gillian; Whittingham, Ian B; Beams, Timothy J

    2002-01-01

    A novel modified oscillator method of calculating energy eigenvalues for colliding ultracold atoms tightly confined in harmonic potentials is presented and applied to trapped spin-polarized metastable helium atoms. The perturbed harmonic oscillator problem is characterized by a long asymptotic region beyond the effective range of the interatomic potential, and a very efficient method for integrating inwards through this outer region is developed. The calculated eigenvalues for states with $l=0$ agree closely with those computed directly from the radial Schr\\"{o}dinger equation for the trapped atoms using a discrete variable method, and with those computed self-consistently from an energy-dependent effective scattering length. Finally, the self-consistent method is generalized to collisions with $l \

  8. Coherent Atom Optics With Fast Metastable Beams: Metastable Helium Diffraction By 1D and 2D Magnetized Reflection Gratings

    Science.gov (United States)

    Grucker, J.; Baudon, J.; Karam, J.-C.; Perales, F.; Bocvarski, V.; Ducloy, M.

    2007-04-01

    1D and 2D reflection gratings (Permalloy stripes or dots deposited on silicon), immersed in an external homogeneous static magnetic field, are used to study 1D and 2D diffraction of fast metastable helium atoms He* (23S1). Both the grazing incidence used here and the repulsive potential (for sub-level m = -1) generated by the magnetisation reduce the quenching effect. This periodically structured potential is responsible for the diffraction in the incidence plane as well as for the diffraction in the perpendicular plane.

  9. Remote antiproton sources

    International Nuclear Information System (INIS)

    Antiprotons are well on their way to becoming a standard laboratory commodity. Heavy utilization of LEAR is ushering in a new era where p's achieve their logical potential, equal to that of e-,e+,H-, as controlled probes and experimental building blocks. The uniqueness and usefulness of - /SUB p/ 's for studies at low (table top) energies is well documented. The main stumbling block to universal pursuit of such studies is the overhead of - /SUB p/ production. The stability of the - /SUB p/ thus makes cogent an investigation of possibilities and limits to transporting - /SUB p/ 's in quantity. I base my discussion on LEAR as the source of - /SUB p/ 's for bottling, since it is the only concrete example to work with at present. Two other lines of contemporary research then, largely in atomic physics, pioneered by Dehmelt and collaborators, aimed at precision studies of clouds of, or single e /SUP +or-/ ,p /SUP +or-/ , or ions in large storage time traps. Second, there is work, experimental and theoretical, from the plasma physics tradition aimed at characterizing non neutral plasmas

  10. Electron-Phonon Coupling Strength at Metal Surfaces Directly Determined from the Helium Atom Scattering Debye-Waller Factor.

    Science.gov (United States)

    Manson, J R; Benedek, G; Miret-Artés, Salvador

    2016-03-17

    A new quantum-theoretical derivation of the elastic and inelastic scattering probability of He atoms from a metal surface, where the energy and momentum exchange with the phonon gas can occur only through the mediation of the surface free-electron density, shows that the Debye-Waller exponent is directly proportional to the electron-phonon mass coupling constant λ. The comparison between the values of λ extracted from existing data on the Debye-Waller factor for various metal surfaces and the λ values known from literature indicates a substantial agreement, which opens the possibility of directly extracting the electron-phonon coupling strength in quasi-2D conducting systems from the temperature or incident energy dependence of the elastic helium atom scattering intensities. PMID:26927966

  11. Fluxes of energetic neutral helium atoms from the heliosheath and the IBEX Ribbon

    Science.gov (United States)

    Swaczyna, Pawel; Grzedzielski, Stan; Bzowski, Maciej

    2014-05-01

    Full sky maps of energetic neutral hydrogen atoms (H ENA) obtained with the Interstellar Boundary Explorer revealed a bright, arc-like Ribbon, which dominates over the heliosheath emission on large swaths of the sky. We simulate the emission of helium ENA from the heliosheath and the IBEX Ribbon. To estimate the heliosheath signal, we use a set of simple models of the heliosphere, where we take the newest results from the Voyagers spacecraft into account. We simulate the evolution of energy spectra of α-particles and He+ ions using a number of binary interactions of He ions with plasma and neutral background in the heliosheath. The suprathermal ions from this distribution are a source of emerging He ENA flux, which we calculate. The fluxes in the observer frame are corrected for the Compton-Getting effect and the re-ionization losses on the path to detector. We conclude that the highest intensities should be expected from the heliospheric tail. For 1 keV He ENA, they are ~ 0.5 - 10 (cm2 ssrkeV )-1, depending on the employed model, whereas the expected intensities in the forward and flank sectors of the heliosphere in models with the heliosheath thickness ~ 25 AU do not exceed 0.02 (cm2 ssrkeV )-1 and 0.2 (cm2 ssrkeV )-1, respectively. For assessment of the IBEX Ribbon emission we compare the He ENA emissions from two models of the Ribbon origin previously developed to explain the hydrogen emission. In the first one, the Ribbon ENAs are produced outside the heliopause from the ionized neutral solar wind in the direction where the local interstellar magnetic field is perpendicular to the line-of-sight. The second model proposes the ENA production at the interface between the Local Interstellar Cloud (LIC) and the Local Bubble (LB). In the first model, the expected intensity is ~ 0.014 (cm2 ssrkeV )-1, i.e., of the order of the emission from the forward sector of the heliosphere, whereas in the second model, the intensity is ~ 2 - 7 (cm2 ssrkeV )-1. If the IBEX

  12. Potential of Energetic Neutral Helium Atoms to Resolve Structure of the Local Interstellar Medium within 0.1 Parsec

    Science.gov (United States)

    Swaczyna, P.; Grzedzielski, S.; Bzowski, M.

    2014-12-01

    Expected fluxes of energetic neutral helium atoms (He ENA) emitted from the heliosheath and created by the Ribbon secondary ENA mechanism are relatively small for the directions of the nose and flanks of the heliosphere. The mean free path against ionization in the Local Interstellar Cloud (LIC) for the He ENA reaches ~8,000 AU for atoms of energy ~5 keV, i.e., about 10 times higher than the mean free path against ionization for hydrogen atoms for the same energy. Thus observation of potential sources in the Local Interstellar Medium by an ENA detector could be possible for distances over a dozen thousand AU. This includes a potential to observe processes at the LIC boundary, to which the closest distance is likely smaller than 10,000 AU. Measurements of He ENA could potentially be used to bridge the gap between direct in situ sampling of our Galactic environment, available from Ulysses and IBEX, and the parsec-scale telescopic observations of interstellar absorption lines. Estimates of the expected heliospheric emission of He ENA are taken from a simple model of the heliosphere, for which we have obtained results consistent with HSTOF observation of He ENA. We use analytical model of the secondary ENA emission with a simple heliolatitude dependence in the supersonic solar wind. For the extraheliospheric sources, we examine simple He ENA production models on distant (detector will give opportunity to distinguish helium atoms from the general ENA flux. This added capability would provide IMAP with a potential to discover possible enhancements in the He ENA fluxes other than from the heliotail direction, which could enable studying kinetic non-equilibrium processes operating in the "dark gap" region currently inaccessible for observations by IBEX and by traditional astrophysical techniques. These processes are potentially ubiquitous in the interstellar medium.

  13. Effects of cold work and niobium on the blistering of zirconium by helium atoms

    International Nuclear Information System (INIS)

    Zr-2.5 wt% Nb and high purity zirconium, in either the fully annealed or 40% cold-worked conditions, were irradiated with 50 keV helium ions at temperatures between 100 K and 773 K to doses up to 2 x 1022 ions/m2. Above 300 K, blisters were not observed in annealed zirconium whereas at lower temperatures, extensive surface damage was produced. In Zr-2.5 wt% Nb, blisters were found in both the annealed and cold-worked alloys at all temperatures. The blistering behaviour in zirconium is related to the trapping of the implanted helium ions and the mechanical properties of these materials. Two zirconium single crystals were irradiated at 573 K and 773 K for comparison. Extensive blistering was observed in both single crystals even though no surface damage was found in the polycrystalline material irradiated under the same conditions. (orig.)

  14. Ultra-low-temperature reactions of C(3P0) atoms with benzene molecules in helium droplets

    International Nuclear Information System (INIS)

    The reaction of carbon atoms with benzene has been investigated in liquid helium droplets at T = 0.37 K. We found an addition of the carbon atom to form an initial intermediate complex followed by a ring opening and the formation of a seven-membered ring. In contrast to a previous gas phase study, the reaction is frozen after these steps and the loss of hydrogen does not occur. A calorimetric technique was applied to monitor the energy balance of the reaction. It was found that more than 267 kJ mol−1 were released in this reaction. This estimation is in line with quantum chemical calculations of the formation energy of a seven-membered carbon ring. It is suggested that reactions of this kind could be responsible for the low abundance of small polycyclic aromatic hydrocarbon molecules in the interstellar medium. We also found the formation of weakly bonded water-carbon adducts, in which the carbon atom is linked to the oxygen atom of the water molecule with a binding energy of about 33.4 kJ mol−1

  15. Beam Diagnostics for Measurements of Antiproton Annihilation Cross Sections at Ultra-low Energy

    Directory of Open Access Journals (Sweden)

    Todoroki K.

    2014-03-01

    Full Text Available The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons collaboration of CERN is currently attempting to measure the antiproton-nucleus in-flight annihilation cross sections on thin target foils of C, Pd, and Pt at 130 keV of kinetic energy. The low-energy antiprotons were supplied by the Antiproton Decelerator (AD and a radio-frequency quadrupole decelerator. For this measurement, a beam profile monitor based on secondary electron emission was developed. Data from this monitor was used to ensure that antiprotons were precisely tuned to the position of an 80-mm-diameter experimental target, by measuring the spatial profile of 200-ns-long beam pulses containing 105 − 106 antiprotons with an active area of 40 mm × 40 mm and a spatial resolution of 4 mm. By using this monitor, we succeeded in finely tuning antiproton beams on the target, and observed some annihilation events originating from the target.

  16. Numerical simulation of the double-to-single ionization ratio for the helium atom in strong laser fields

    Science.gov (United States)

    Chen, Zhangjin; Zheng, Yanyan; Yang, Weifeng; Song, Xiaohong; Xu, Junliang; DiMauro, L. F.; Zatsarinny, Oleg; Bartschat, Klaus; Morishita, Toru; Zhao, Song-Feng; Lin, C. D.

    2015-12-01

    We present calculations on the ratio between double and single ionization of helium by a strong laser pulse at a wavelength of 780 nm using the quantitative rescattering (QRS) model. According to this model, the yield for the doubly charged ion He+2 can be obtained by multiplying the returning electron wave packet (RWP) with the total cross sections (TCSs) for electron impact ionization and electron impact excitation of +He in the singlet spin channel. The singlet constraint was imposed since the interaction of the helium atom with the laser and the recollision processes both preserve the total spin of the system. An R -matrix (close-coupling) code is used to obtain accurate TCSs, while the RWPs, according to the QRS, are calculated by the strong-field approximation for high-energy photoelectrons. The laser field, which lowers the required energy for the electron to escape from the nucleus at the time of recollision, is also taken into account. The simulated results are in good agreement with the measured He+2/+He ratio over a broad range of laser intensities. The result demonstrates that the QRS approach based on the rescattering model is fully capable of quantitatively interpreting nonsequential double ionization processes.

  17. Interaction of antiprotons with nuclei

    Czech Academy of Sciences Publication Activity Database

    Hrtánková, Jaroslava; Mareš, Jiří

    2016-01-01

    Roč. 945, JAN (2016), s. 197-215. ISSN 0375-9474 R&D Projects: GA ČR(CZ) GA15-04301S Institutional support: RVO:61389005 Keywords : antiproton-nucleus interaction * antiproton annihilation * antiproton nuclear bound states Subject RIV: BE - Theoretical Physics Impact factor: 2.202, year: 2014

  18. Excitation and ionization of hydrogen and helium atoms by femtosecond laser pulses: theoretical approach by Coulomb-Volkov states

    International Nuclear Information System (INIS)

    We present a theoretical approach using Coulomb-Volkov states that appears useful for the study of atomic multi-photonic processes induced by intense XUV femtosecond laser pulses. It predicts hydrogen ionization spectra when it is irradiated by laser pulses in perturbations conditions. Three ways have been investigated. Extension to strong fields when ℎω > Ip: it requires to include the hydrogen ground state population, introducing it in standard Coulomb-Volkov amplitude leads to saturated multi-photonic ionization. Extension to multi-photonic transitions with ℎω p: new quantum paths are open by the possibility to excite the lower hydrogen bound states. Multiphoton excitation of these states is investigated using a Coulomb-Volkov approach. Extension to helium: two-photon double ionization study shows the influence of electronic correlations in both ground and final state. Huge quantity of information such as angular and energetic distributions as well as total cross sections is available. (author)

  19. Energy-dependent photoelectron angular distributions of two-color two-photon above threshold ionization of atomic helium

    International Nuclear Information System (INIS)

    Energy-dependent photoelectron angular distributions from two-color two-photon above threshold ionizations are investigated to determine the partial-wave characteristics of free-free electronic transitions in helium. Sideband photoelectron energies ranging from 0.18 to 13.0 eV are measured with different wavelengths of the perturbative infrared dressing field as well as different individually selected high-order harmonics. Using the experimentally measured cross-section ratios and anisotropy parameters together with analytical expressions derived from second-order perturbation theory, the partial-wave branching fractions going to the S and D waves in the positive and negative sidebands are determined as a function of photoelectron kinetic energy. The results provide a sensitive test for theoretical models of two-color two-photon above threshold ionization in atoms and molecules.

  20. Cancer Therapy with Antiprotons

    Science.gov (United States)

    Bassler, Niels; Holzscheiter, Michael H.; Ad-4 Collaboration

    2005-10-01

    Starting in 2003 the AD-4/ACE collaboration has studied the biological effects of antiprotons annihilating in a human tissue like material on live V-79 Chinese Hamster cells. The main goal of the work is to prove the efficacy of antiprotons for cancer therapy. In this report we discuss a critical point to be considered carefully for all particle beam radiation therapies, namely the loss of primary particles from the beam on the way to a tumor seated some distance below the surface.

  1. Biological effectiveness of antiproton annihilation

    CERN Document Server

    Holzscheiter, Michael H.; Bassler, Niels; Beyer, Gerd; De Marco, John J.; Doser, Michael; Ichioka, Toshiyasu; Iwamoto, Keisuke S.; Knudsen, Helge V.; Landua, Rolf; Maggiore, Carl; McBride, William H.; Møller, Søren Pape; Petersen, Jorgen; Smathers, James B.; Skarsgard, Lloyd D.; Solberg, Timothy D.; Uggerhøj, Ulrik I.; Withers, H.Rodney; Vranjes, Sanja; Wong, Michelle; Wouters, Bradly G.

    2004-01-01

    We describe an experiment designed to determine whether or not the densely ionizing particles emanating from the annihilation of antiprotons produce an increase in “biological dose” in the vicinity of the narrow Bragg peak for antiprotons compared to protons. This experiment is the first direct measurement of the biological effects of antiproton annihilation. The experiment has been approved by the CERN Research Board for running at the CERN Antiproton Decelerator (AD) as AD-4/ACE (Antiproton Cell Experiment) and has begun data taking in June of 2003. The background, description and the current status of the experiment are given.

  2. Three dimensional biological dose distribution of antiprotons

    International Nuclear Information System (INIS)

    The goal of external beam cancer therapy is to destroy the tumour while sparing the healthy tissue around it. In hadron therapy, the dose profile of heavy charged particles satisfies this request, because most of the energy is deposited at the end of the particle path, in the Bragg peak. Antiprotons are even more promising, thanks to the extra energy released by annihilation when captured in a normal atom at the end of range. The aim of the AD-4/ACE experiment at CERN is to determine the increase in biological dose near the Bragg peak due to densely ionizing particles emanating from the annihilation of antiprotons. Initial experiments showed the damage to cells inflicted at the end of the beam for identical damage at the skin level to be four times higher for antiprotons than for protons. The radiation field in a spread-out Bragg peak produced with antiprotons is highly mixed and for proper dose planning knowledge of linear energy transfer (LET) and relative biological efficiency (RBE) at any point in the target is needed. We are studying a number of detection methods for their response to mixed radiation fields with the goal to obtain a direct measurement of the 3D LET distribution and report on first results.

  3. Measurements of cosmic ray antiprotons with PAMELA and studies of propagation models

    CERN Document Server

    Wu, Juan

    2012-01-01

    Studying the acceleration and propagation mechanisms of Galactic cosmic rays can provide information regarding astrophysical sources, the properties of our Galaxy, and possible exotic sources such as dark matter. To understand cosmic ray acceleration and propagation mechanisms, accurate measurements of different cosmic ray elements over a wide energy range are needed. The PAMELA experiment is a satellite-borne apparatus which allows different cosmic ray species to be identified over background. Measurements of the cosmic ray antiproton flux and the antiproton-to-proton flux ratio from 1.5 GeV to 180 GeV are presented in this thesis. Compared to previous experiments, PAMELA extends the energy range of antiproton measurements and provides significantly higher statistics. The derived antiproton flux and antiproton-to-proton flux ratio are consistent with previous measurements and generally considered to be produced as secondary products when cosmic ray protons and helium nuclei interact with the interstellar med...

  4. The Facility for Antiproton and Ion Research

    Science.gov (United States)

    Langanke, K.

    2015-11-01

    In the coming years the Facility for Antiproton and Ion Research FAIR will be constructed at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. This new accelerator complex will allow for unprecedented and path-breaking research in hadronic, nuclear and atomic physics as well as applied sciences. This manuscript will discuss some of these research opportunities, with a focus on nuclear physics related to supernova dynamics and nucleosynthesis.

  5. Quasi-free scattering in the ionization and destruction of hydrogen and helium Rydberg atoms in collision with neutral targets

    International Nuclear Information System (INIS)

    Hydrogen and helium Rydberg atoms (H** and He**), with principal quantum number n ranging from 10 to 20, have been used in collision experiments from 1 to 40 keV/amu. These were produced by electron capture in a charge-exchange cell and analyzed by ionization in a modulated electric field combined with phase-sensitive detection. Three experiments have been conducted. In the first, spectra of the band of H and He Rydberg states from electron capture were produced by the modulated field technique and compared. Considerable differences were found between the two. Both types of spectra were analyzed with calculations of Stark energies and field ionization rates. Attempts were made to simulate the spectra using this information and some assumptions about the state distribution produced in the electron capture. In the second experiment, destruction cross sections for H** incident on N2, Ar, and SF6 were measured. This was a further test of the independent-particle model for Rydberg atom scattering; in this model, the atom is destroyed by quasi-free scattering of either the ionic core or the outer electron. Already proven valid for n = 20-35, this has been extended to n as low as 10, as measurements with n = 10 showed full compliance with the model. In the third experiment, not only destruction cross sections but also ionization cross sections for H** and He** incident on Xe, AR, and N2 were measured. The ionization measurement is a more sensitive test of the quasi-free scattering of the Rydberg electron. This was especially important for the Xe and Ar targets, which exhibits a Ramsauer-Townsend minimum in their free-electron scattering cross sections. The quasi-free Rydberg electron should reproduce these data. Unmistakable deviations from the quasi-free prediction were seen in Xe and N2 but not in Ar. This represents the first measurement of a breakdown of the Independent Particle Model for fast Rydberg atom scattering

  6. On the Formation of (Anionic) Excited Helium Dimers in Helium Droplets

    OpenAIRE

    Huber, Stefan E.; Mauracher, Andreas

    2014-01-01

    Metastable atomic and molecular helium anions exhibiting high-spin quartet configurations can be produced in helium droplets via electron impact. Their lifetimes allow detection in mass spectrometric experiments. Formation of atomic helium anions comprises collision-induced excitation of ground state helium and concomitant electron capture. Yet the formation of molecular helium anions in helium droplets has been an unresolved issue. In this work, we explore the interaction of excited helium a...

  7. Long-range interactions between excited helium and alkali-metal atoms

    KAUST Repository

    Zhang, J.-Y.

    2012-12-03

    The dispersion coefficients for the long-range interaction of the first four excited states of He, i.e., He(2 1,3S) and He(2 1,3P), with the low-lying states of the alkali-metal atoms Li, Na, K, and Rb are calculated by summing over the reduced matrix elements of the multipole transition operators. For the interaction between He and Li the uncertainty of the calculations is 0.1–0.5%. For interactions with other alkali-metal atoms the uncertainty is 1–3% in the coefficient C5, 1–5% in the coefficient C6, and 1–10% in the coefficients C8 and C10. The dispersion coefficients Cn for the interaction of He(2 1,3S) and He(2 1,3P) with the ground-state alkali-metal atoms and for the interaction of He(2 1,3S) with the alkali-metal atoms in their first 2P states are presented in this Brief Report. The coefficients for other pairs of atomic states are listed in the Supplemental Material.

  8. Antiprotons are another matter

    International Nuclear Information System (INIS)

    Theories of gravity abound, whereas experiments in gravity are few in number. An important experiment in gravity that has not been performed is the measurement of the gravitational acceleration of antimatter. Although there have been attempts to infer these properties from those of normal matter, none of these theoretical arguments are compelling. Modern theories of gravity that attempt to unify gravity with the other forces of nature predict that in principle antimatter can fall differently than normal matter in the Earth's field. Some of these supergravity theories predict that antimatter will fall faster, and that normal matter will fall with a small Baryon-number dependance in the earth's field. All of these predictions violate the Weak Equivalence Principle, a cornerstone of General Relativity, but are consistent with CPT conservation. In our approved experiment at LEAR (PS-200) we will test the Weak Equivalence Principle for antimatter by measuring the gravitational acceleration of the antiproton. Through a series of deceleration stages, antiprotons from LEAR will be lowered in energy to ∼4 Kelvin at which energy the gravitational effect will be measureable. The measurement will employ the time-of-flight technique wherein the antiprotons are released vertically in a drift tube. The spectrum of time-of-flight measurements can be used to extract the gravitational acceleration experienced by the particles. The system will be calibrated using H- ions which simulates the electromagnetic behavior of the antiproton, yet is a baryon to ∼0.1%. To extract the gravitational acceleration of the antiproton relative to the H- ion with a statistical precision of 1% will require the release of ∼106 to 107 particles

  9. Antiproton magnetic moment determined from the HFS of p-bar He+

    International Nuclear Information System (INIS)

    We report a determination of the antiproton magnetic moment, measured in a three-body system, independent of previous experiments. We present results from a systematic study of the hyperfine (HF) structure of antiprotonic helium where we have achieved a precision more than a factor of 10 better than our first measurement. A comparison between the experimental results and three-body quantum electrodynamic (QED) calculations leads to a new value for the antiproton magnetic moment μsp-bar=-2.7862(83)μN, which agrees with the magnetic moment of the proton within 2.9x10-3.

  10. The direct ionization processes in the collisions of partially stripped carbon and oxygen ions with helium atoms at low-to-intermediate energies

    International Nuclear Information System (INIS)

    The values of direct double-to-single ionization ratio R of helium atoms induced by Cq+, Oq++ (q = 1–4) ions at incident energies from 0.2 to 8.5MeV are measured. Based on the existing model (Shao J X, Chen X M and Ding B W 2007 Phys. Rev. A 75 012701) the effective charge of the projectile is introduced to theoretically estimate the value of R for the partially stripped ions impacting on helium atoms. The results calculated from our 'effective charge' model are in good agreement with the experimental data, and the dependence of the effective charge on the ionization energy of the projectile is also discussed qualitatively. (atomic and molecular physics)

  11. Helium in chirped laser fields as a time-asymmetric atomic switch

    Czech Academy of Sciences Publication Activity Database

    Kaprálová-Žďánská, Petra Ruth; Moiseyev, N.

    2014-01-01

    Roč. 141, č. 1 (2014), "014307-1"-"014307-14". ISSN 0021-9606 R&D Projects: GA ČR GAP205/11/0571 Institutional support: RVO:68378271 Keywords : laser excitation * chirped pulses * non-hermitian quantum mechanics * time-asymmetry Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 2.952, year: 2014

  12. Molecular dynamical simulations of helium atom interacting with the XUV field aimed at predicting partial ionization yields of helium ion in various electronic states

    Czech Academy of Sciences Publication Activity Database

    Kaprálová-Žďánská, Petra Ruth; Šmydke, Jan

    Kanazawa: Ishikawa Prefecture Museum of Art, 2011. ---. [International Workshop on Quantum Systems in Chemistry and Physics (QSCP XVI) /16./. 11.09.2011-17.09.2011, Kanazawa] Institutional research plan: CEZ:AV0Z40400503 Keywords : helium * XUV laser pulses Subject RIV: CF - Physical ; Theoretical Chemistry

  13. Antiproton-nucleus interaction

    Science.gov (United States)

    Cugnon, J.; Vandermeulen, J.

    The antiproton-nucleus physics is reviewed. On the experimental side, the recent results obtained at the LEAR, BNL and KEK facilities are analyzed. A brief summary of the main pp and pn experimental data is also given. The antiproton-nucleus interaction can lead to elasic, inelastic and charge exchange scattering and to annihilation. The latter is very dominant. The scattering cross-sections are usually analyzed in terms of complex potential models. The relationship between potentials, charge conjugation and Dirac phenomenology is discussed. Much emphasis is put on the dynamics of the antiproton annihilation on nuclei. The energy transfer, pion absorption and target response are analyzed within the intranuclear cascade model. Special interest is devoted to strangeness production, hypernucleus formation and possible annihilation on two nucleons. Signatures for this new process are searched in experimental data. Finally, the highly debated question of quark-gluon formation is analyzed. Cet article constitue une revue de la physique antiproton-noyau. Du point de vue expérimental, cette revue porte particulièrement sur les récents résultats obtenus à LEAR, BNL et KEK. On y a aussi inclus une mise à jour des faits expérimentaux principaux pour pp et pn. L'interaction antiproton-noyau conduit à la diffusion élastique, inélastique et d'xA9change de charge et à des processus d'annihilation. Habituellement, les expériences de diffusion sont analysées en termes de potentiels complexes. La relation entre ces potentiels, la conjugaison de charge et la phénoménologie de Dirac est discutée. On s'est particulièrement intéressé à la dynamique de l'annihilation d'antiprotons sur des noyaux. Le transfert d'énergie, l'absorption de pions et la réponse de la cible sont analysés dans le cadre du modèle de cascade intranucléaire. Certains autres points sont discutés plus en détail: la production d'étrangeté, la formation d'hypernoyaux et l'annihilation sur

  14. Is solid helium a supersolid?

    International Nuclear Information System (INIS)

    Recent experiments suggest that helium-4 atoms can flow through an experimental cell filled with solid helium. But that incompletely understood flow is quite different from the reported superfluid-like motion that so excited physicists a decade ago

  15. The PS 200 catching trap: A new tool for ultra-low energy antiproton physics

    International Nuclear Information System (INIS)

    Approximately one million antiprotons have been trapped and electron cooled in the PS200 catching trap from a single fast extracted pulse from LEAR. The system is described in detail, different extraction schemes are discussed, and possible applications of this instrument to ultra-low energy atomic and nuclear physics with antiprotons are mentioned

  16. FAIR - the Facility for Antiproton and Ion Research: the Universe in the Lab

    Science.gov (United States)

    Weissbach, F.

    2015-11-01

    As of the year 2018 the Facility for Antiproton and Ion Research (FAIR) will offer access to exotic ion beams and beams of antiproton of unprecedented luminosity. The facility currently under construction in Darmstadt, Germany, adjacent to the existing accelerator at the GSI Helmholtz Centre for Heavy-Ion Research, will serve several collaborations and fields simultaneously: atomic, hadron, nuclear, and plasma physics.

  17. Trapping of antiprotons -- a first step on the way to antihydrogen

    International Nuclear Information System (INIS)

    A first step towards producing and effectively utilizing antihydrogen atoms consists of trapping antiprotons. The immediate next step must then be to control, i.e. trap the produced antihydrogen. The current state of the art in trapping antiprotons and positrons is reviewed, and the challenges in trapping the resulting neutral particles are discussed

  18. The properties of helium atoms and positrons as impurities in metals

    International Nuclear Information System (INIS)

    Topics covered include: (A) atoms in simple metals: (1) the highly repulsive e-/He interaction and its consequences for binding energies in simple metals; (2) binding energy calculations for jellium and their implications for validity of pair-potential He/M interactions; and (3) the need for experimental data on high negative binding energy systems: (B) low energy positrons in simple metals: (1) behaviour of the positron especially its range (< 100A); (2) consequences for experiments on voids; and (3) possibility for non-destructive depth profiling of defect concentration. (author)

  19. Precision Spectroscopy of Kaonic Helium-3 Atoms X-rays at J-PARC

    Science.gov (United States)

    Iio, M.; Bhang, H.; Cargnelli, M.; Choi, Seonho; Curceanu, C.; Doce, O. V.; Enomoto, S.; Fujioka, H.; Fujiwara, Y.; Guaraldo, C.; Hashimoto, T.; Hayano, R. S.; Hiraiwa, T.; Ishimoto, S.; Ishiwatari, T.; Itahashi, K.; Iwasaki, M.; Kou, H.; Kienle, P.; Marton, J.; Matsuda, Y.; Noumi, H.; Ohnishi, H.; Okada, S.; Outa, H.; Sakuma, F.; Sato, M.; Sekimoto, M.; Shi, H.; Sirghi, D.; Sirghi, F.; Suzuki, T.; Tanida, K.; Tatsuno, H.; Tokuda, M.; Tomono, D.; Toyoda, A.; Tsukada, K.; Vidal, A. R.; Widmann, E.; Wunschek, B.; Yamazaki, T.; Zmeskal, J.

    2010-04-01

    We will measure the Balmer-series x-rays of kaonic-3He atoms using large-area high-resolution silicon drift x-rays detectors in order to provide the crucial information of K--nucleus strong interaction at the low energy limit. The strong interaction 2p level shift will be determined with a precision of a few eV. At the present status, the construction of all detectors is in progress. In February, 2009, the first tuning of K1.8BR beamline was performed by the secondary beam generated in J-PARC hadron facility. The data taking will be started soon.

  20. Bubble chamber: antiproton annihilation

    CERN Multimedia

    1971-01-01

    These images show real particle tracks from the annihilation of an antiproton in the 80 cm Saclay liquid hydrogen bubble chamber. A negative kaon and a neutral kaon are produced in this process, as well as a positive pion. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that had been heated to boiling point.

  1. Extra Low ENergy Antiproton

    CERN Multimedia

    To produce dense antiproton beams at very low energies (110 keV), it has been proposed to install a small decelerator ring between the existing AD ring and the experimental area. Phase-space blowup during deceleration is compensated by electron cooling such that the final emittances are comparable to the 5MeV beam presently delivered by the AD. An immediate consequence is a significant increase in the number of trapped antiprotons at the experiments as outlined in the proposal CERN/SPSC-2009-026; SPCS-P-338. This report describes the machine parameters and layout of the proposal ELENA (Extra Low ENergy Antiproton)ring also gives an approximate estimate of cost and manpower needs. Since the initial estimate, published in 2007 (CERN-AB-2007-079), the ELENA design has evolved considerably. This is due to a new location in the AD hall to acommodate for the possibility of another experimental zone, as suggested by the SPCS, and also due to improvements in the ring optics and layout. The cost estimate that is prese...

  2. Energy loss of 10 MeV/amu atomic helium in carbon

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, H.; Sakamoto, N. [Nara Women`s Univ. (Japan). Dept. of Physics; Katayama, I. [Institute for Nuclear Study, University of Tokyo, Tanashi, Tokyo 188 (Japan); Haruyama, Y.; Saito, M. [Laboratory of Applied Physics, Kyoto Prefectural University, Kyoto 606 (Japan); Yoshida, K. [Department of Nuclear Engineering, Kyoto University, Kyoto 606-01 (Japan); Tosaki, M. [Radio Isotope Research Center, Kyoto University, Kyoto 606 (Japan); Susuki, Y.; Kimura, K. [Department of Engineering Physics and Mechanics, Kyoto University, Kyoto 606-01 (Japan)

    1997-10-01

    Mean energy losses of 31.8 MeV neutral {sup 3}He atoms penetrating through thin carbon foils of 1.6-7.2 {mu}g/cm{sup 2} were measured using a high-resolution magnetic spectrograph. The measured particles are those entered into the carbon foil as {sup 3}He{sup 0} and emerged from it as {sup 3}He{sup 0}. From the attenuation measurement of {sup 3}He{sup 0} in the foils, we can regard the measured energy losses as those of {sup 3}He{sup 0} in a frozen charge state. The measured stopping power of carbon for 31.8 MeV {sup 3}He{sup 0} is 58.2 {+-} 4.9 eV/{mu}g/cm{sup 2}. Including our previous data for other partially clothed ions of the same velocity, the projectile atomic number dependence of the screening effect due to the bound electrons is roughly reproduced by the theoretical predictions based on the Born approximation. (orig.). 14 refs.

  3. Atom probe field ion microscope study of the range and diffusivity of helium in tungsten

    International Nuclear Information System (INIS)

    A time-of-flight (TOF) atom-probe field-ion microscope (FIM) specifically designed for the study of defects in metals is described. With this automated system 600 TOF min-1 can be recorded and analyzed. Performance tests of the instrument demonstrated that (1) the seven isotopes of molybdenum and the five isotopes of tungsten can be clearly resolved; and (2) the concentration and spatial distribution of all constitutents present at levels greater than 0.05 at. % in a W--25 at. % Re, Mo--1.0 at. % Ti, Mo--1.0 at. % Ti--0.08 at. % Zr (TZM), a low swelling stainless steel (LS1A) and a metallic glass (Metglas 2826) can be measured. The effect of the rate of field evaporation on the quantitative atom probe analysis of a Mo--1.0 at. % Ti alloy and a Mo--1.0 at. % Ti--0.08 at. % Zr alloy was investigated. As the field evaporation rate increased the measured Ti concentration was found to also increase. A simple qualitative model was proposed to explain the observation. The spatial distribution of titanium in a fast neutron irradiated Mo--1.0 at. % Ti alloy has been investigated. No evidence of Ti segregation to the voids was detected nor has any evidence of significant resolution of Ti from the TiC precipitates been detected. A small amount of segregation of carbon to a void was detected

  4. Antiproton compression and radial measurements

    CERN Document Server

    Andresen, G B; Bowe, P D; Bray, C C; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D R; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jorgensen, L V; Kurchaninov, L; Lambo, R; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Page R D; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Seif El Nasr, S; Silveira, D M; Storey, J W; Thompson, R I; Van der Werf, D P; Wurtele, J S; Yamazaki, Y

    2008-01-01

    Control of the radial profile of trapped antiproton clouds is critical to trapping antihydrogen. We report detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, achieved by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial profile, and its relation to that of the electron plasma. We also measure the outer radial profile by ejecting antiprotons to the trap wall using an octupole magnet.

  5. Precision Spectroscopy of Kaonic Helium-3 Atoms X-rays at J-PARC

    Directory of Open Access Journals (Sweden)

    Tanida K.

    2010-04-01

    Full Text Available We will measure the Balmer-series x-rays of kaonic-3He atoms using large-area high-resolution silicon drift x-rays detectors in order to provide the crucial information of K−-nucleus strong interaction at the low energy limit. The strong interaction 2p level shift will be determined with a precision of a few eV. At the present status, the construction of all detectors is in progress. In February, 2009, the first tuning of K1.8BR beamline was performed by the secondary beam generated in J-PARC hadron facility. The data taking will be started soon.

  6. The direct ionization processes in the collisions of partially stripped carbon and oxygen ions with helium atoms at low-to-intermediate energies

    Institute of Scientific and Technical Information of China (English)

    Zhou Chun-Lin; Shao Jian-Xiong; Chen Xi-Meng; Sun Guang-Zhi; Zou Xian-Rong

    2008-01-01

    The values of direct double- to-single ionization ratio R of helium atoms induced by Cq+,Oq+ (q=1-4) ions at incident energies from 0.2 to 8.5MeV are measured.Based on the existing model (Shao J X,Chen X M and Ding B W 2007 Phys.Rev.A 75 012701) the effective charge of the projectile is introduced to theoretically estimate the value of R for the partially stripped ions impacting on helium atoms.The results calculated from our "effective charge" model are in good agreement with the experimental data,and the dependence of the effective charge on the ionization energy of the projectile is also discussed qualitatively.

  7. Multiphoton effects in laser-assisted ionization of a helium atom by electron impact

    International Nuclear Information System (INIS)

    The dynamics of the electron impact multiphoton ionization of a He atom in the presence of an intense laser field (nγe, 2e) is studied theoretically for laser polarization (||l) and perpendicular to the incident momentum. The triple differential (TDCS) as well as the double differential (DDCS) cross sections are studied for the coplanar asymmetric geometry. The results are compared with the only available kinematically complete experiment at high incident energy (1000 eV). Significant laser modification (enhancement) is noted due to multiphoton effects in the present binary and recoil peak intensities of the TDCS for both the geometries, in qualitative agreement with the experiment. In the single photon case, the net effect of the laser field is to suppress the field free (FF) TDCS as well as the DDCS in the zeroth order approximation of the ejected electron wave function (CV), while in the first order (MCV), the cross sections are found to be enhanced. The CV multiphoton cross sections obey the famous Kroll Watson (KW) sum rule while the latter does not hold good in the corresponding MCV approximation. (authors)

  8. Biological effectiveness of antiproton annihilation

    DEFF Research Database (Denmark)

    Holzscheiter, M.H.; Agazaryan, N.; Bassler, Niels;

    2004-01-01

    We describe an experiment designed to determine whether or not the densely ionizing particles emanating from the annihilation of antiprotons produce an increase in ‘‘biological dose’’ in the vicinity of the narrow Bragg peak for antiprotons compared to protons. This experiment is the first direct...

  9. AA antiproton production target

    CERN Multimedia

    1979-01-01

    The first version of the antiproton production target was a tungsten rod, 11 cm long and 3 mm in diameter. The rod was embedded in graphite, pressure-seated into an outer casing of stainless steel. At the entrance to the target assembly was a scintillator screen, imprinted with circles every 5 mm in radius, which allowed to precisely aim the 26 GeV high-intensity proton beam from the PS onto the centre of the target rod. The scintillator screen was a 1 mm thick plate of Cr-doped alumina. See also 7903034 and 7905091.

  10. Low energy antiproton physics

    International Nuclear Information System (INIS)

    This paper summarizes the present experimental and theoretical status of antinucleon-nucleon (bar NN) interactions at low energy (below 2 GeV/c). The authors discuss elastic scattering, hyperon pair production, and annihilation into mesonic channels, including the search for exotic meson states in the annihilation debris. New results from the Low Energy Antiproton Ring (LEAR) at CERN, from KEK in Japan, and from Brookhaven National Laboratory (BNL) are now available. Some of the experiments and their comparison to theoretical predictions have been reviewed earlier. The authors extend these reviews to more recent data and theoretical calculations

  11. AA antiproton production target

    CERN Multimedia

    1979-01-01

    The first version of the antiproton production target was a tungsten rod, 11 cm long (actually a row of 11 rods, each 1 cm long) and 3 mm in diameter. The rod was embedded in graphite, pressure-seated into an outer casing made of stainless steel. The casing had fins for forced-air cooling. In this picture, the 26 GeV high-intensity beam from the PS enters from the right, where a scintillator screen, with circles every 5 mm in radius, permits precise aim at the target centre. See also 7903034 and 7905094.

  12. Antiproton Powered Gas Core Fission Rocket

    International Nuclear Information System (INIS)

    Extensive research in recent years has demonstrated that 'at rest' annihilation of antiprotons in the uranium isotope U238 leads to fission at nearly 100% efficiency. The resulting highly-ionizing, energetic fission fragments can heat a suitable medium to very high temperatures, making such a process particularly suitable for space propulsion applications. Such an ionized medium, which would serve as a propellant, can be confined by a magnetic field during the heating process, and subsequently ejected through a magnetic nozzle to generate thrust. The gasdynamic mirror (GDM) magnetic configuration is especially suited for this application since the underlying confinement principle is that the plasma be of such density and temperature as to make the ion-ion collision mean free path shorter than the plasma length. Under these conditions the plasma behaves like a fluid, and its escape from the system is analogous to the flow of a gas into vacuum from a vessel with a hole. For the system we propose we envisage radially injecting atomic or U238 plasma beam at a pre-determined position and axially pulsing an antiproton beam which upon interaction with the uranium target gives rise to near isotropic ejection of fission fragments with a total mass of 212 amu and total energy of about 160 MeV. These particles, along with the annihilation products (i.e. pions and muons) will heat the background U238 gas - inserted into the chamber just prior to the release of the antiproton - to one keV temperature. Preliminary analysis reveals that such a propulsion system can produce a specific impulse of about 3000 seconds at a thrust of about 50 kN. When applied to a round trip Mars mission, we find that such a journey can be accomplished in about 142 days with 2 days of thrusting and requiring only one gram of antiprotons to achieve it

  13. Antiproton Powered Gas Core Fission Rocket

    Science.gov (United States)

    Kammash, T.

    Extensive research in recent years has demonstrated that “at rest” annihilation of antiprotons in the uranium isotope U238 leads to fission at nearly 100% efficiency. The resulting highly-ionizing, energetic fission fragments can heat a suitable medium to very high temperatures, making such a process particularly suitable for space propulsion applications. Such an ionized medium, which would serve as a propellant, can be confined by a magnetic field during the heating process, and subsequently ejected through a magnetic nozzle to generate thrust. The gasdynamic mirror (GDM) magnetic configuration is especially suited for this application since the underlying confinement principle is that the plasma be of such density and temperature as to make the ion-ion collision mean free path shorter than the plasma length. Under these conditions the plasma behaves like a fluid, and its escape from the system is analogous to the flow of a gas into vacuum from a vessel with a hole. For the system we propose we envisage radially injecting atomic or U238 plasma beam at a pre-determined position and axially pulsing an antiproton beam which upon interaction with the uranium target gives rise to near isotropic ejection of fission fragments with a total mass of 212 amu and total energy of about 160 MeV. These particles, along with the annihilation products (i.e. pions and muons) will heat the background U238 gas - inserted into the chamber just prior to the release of the antiproton - to one keV temperature. Preliminary analysis reveals that such a propulsion system can produce a specific impulse of about 3000 seconds at a thrust of about 50 kN. When applied to a round trip Mars mission, we find that such a journey can be accomplished in about 142 days with 2 days of thrusting and requiring only one gram of antiprotons to achieve it.

  14. Secondary antiprotons as a Galactic Dark Matter probe

    CERN Document Server

    Evoli, Carmelo; Grasso, Dario

    2015-01-01

    We present a novel determination of the astrophysical uncertainties associated to the secondary antiproton flux originating from cosmic-ray spallation on the interstellar gas. We select a set of propagation models compatible with the recent B/C data from PAMELA, and find those providing minimal and maximal antiproton fluxes in different energy ranges. We use this result to determine the most conservative bounds on relevant Dark Matter (DM) annihilation channels: We find that the recent claim of a DM interpretation of a gamma-ray excess in the Galactic Center region cannot be ruled out by current antiproton data. Finally, we discuss the impact of the recently released preliminary data from AMS-02. In particular, we provide a reference model compatible with proton, helium and B/C spectra from this experiment. Remarkably, the main propagation parameters of this model are in perfect agreement with the best fit presented in our earlier statistical analyses. We also show that the antiproton-to-proton ratio does not...

  15. Treatment Plans for Antiproton Beams

    DEFF Research Database (Denmark)

    Holzscheiter, Michael; Bassler, Niels; Herrmann, Rochus;

    Antiprotons have been proposed as potential modality for particle beam cancer therapy by Gray and Kalogeropoulos in 1985. This proposal was based on the enhancement of physical dose deposition near the end of range due to the annihilation of antiprotons when captured by a nucleus and the expectat......Antiprotons have been proposed as potential modality for particle beam cancer therapy by Gray and Kalogeropoulos in 1985. This proposal was based on the enhancement of physical dose deposition near the end of range due to the annihilation of antiprotons when captured by a nucleus and the...... expectation of an enhanced RBE of this additional dose. Starting in 2003 the AD-4 collaboration at CERN has studied biological effects of antiproton beams on V79 Chinese Hamster cells and human FaDu cells. The AD-4 collaboration has developed relative and absolute dosimetry for pulsed antiproton beams. Data...... from these measurements were used to benchmark the FLUKA Monte Carlo code, which then has been used for calculations of physical dose inside and outside of the primary antiproton beam. From clonogenic survival studies on the different cell lines mentioned above we have determined biological effective...

  16. Space-time resolved density of helium metastable atoms in a nanosecond pulsed plasma jet: influence of high voltage and pulse frequency

    Science.gov (United States)

    Douat, Claire; Kacem, Issaad; Sadeghi, Nader; Bauville, Gérard; Fleury, Michel; Puech, Vincent

    2016-07-01

    Using tunable diode laser absorption spectroscopy, the spatio-temporal distributions of the helium He(23S1) metastable atoms’ density were measured in a plasma jet propagating in ambient air. The plasma jet was produced by applying short duration high voltage pulses on the electrodes of a DBD-like structure, at a repetition rate in the range 1–30 kHz. In addition to the metastable density, the spatial distribution of helium 587 nm emission intensity was also investigated to give insight into the excitation mechanisms of the He(33D) excited state inside the dielectric tube, in which no laser measurement can be performed. It is demonstrated that the shape of the radial distribution of helium He(23S1) metastable atoms strongly depends on the polarity of the applied voltage and on the repetition frequency. For positive applied voltages, a dramatic constriction of the excited species production is observed whenever the pulse repetition frequency is higher than 6 kHz, and the voltage higher than 5 kV. This shrinking of the jet structure induces an increase by one order of magnitude of the metastable atoms’ density in the jet centre which reaches values as high as 1014 cm‑3. Beyond a critical distance, associated to a transition between a positive streamer and a negative one, the distribution of the excited atoms gets back to an annular structure. For the negative polarity, no shrinking effect correlated to the pulse repetition frequency was observed. The on-axis constriction of the excited species for the high repetition rate and positive polarity is attributed to a memory effect induced by the negative ions, having a lifetime of hundreds of microseconds, left between successive pulses at the periphery of the helium gas flow.

  17. A reservoir trap for antiprotons

    CERN Document Server

    Smorra, Christian; Franke, Kurt; Nagahama, Hiroki; Schneider, Georg; Higuchi, Takashi; Van Gorp, Simon; Blaum, Klaus; Matsuda, Yasuyuki; Quint, Wolfgang; Walz, Jochen; Yamazaki, Yasunori; Ulmer, Stefan

    2015-01-01

    We have developed techniques to extract arbitrary fractions of antiprotons from an accumulated reservoir, and to inject them into a Penning-trap system for high-precision measurements. In our trap-system antiproton storage times > 1.08 years are estimated. The device is fail-safe against power-cuts of up to 10 hours. This makes our planned comparisons of the fundamental properties of protons and antiprotons independent from accelerator cycles, and will enable us to perform experiments during long accelerator shutdown periods when background magnetic noise is low. The demonstrated scheme has the potential to be applied in many other precision Penning trap experiments dealing with exotic particles.

  18. Proton-antiproton collider physics

    CERN Document Server

    Altarelli, Guido

    1989-01-01

    This volume reviews the physics studied at the CERN proton-antiproton collider during its first phase of operation, from the first physics run in 1981 to the last one at the end of 1985. The volume consists of a series of review articles written by physicists who are actively involved with the collider research program. The first article describes the proton-antiproton collider facility itself, including the antiproton source and its principle of operation based on stochastic cooling. The subsequent six articles deal with the various physics subjects studied at the collider. Each article descr

  19. Many Facets of Strangeness Nuclear Physics with Stored Antiprotons

    CERN Document Server

    Pochodzalla, Josef; Lorente, Alicia Sanchez; Rojo, Marta Martinez; Steinen, Marcell; Gerl, Jürgen; Kojouharova, Jasmina; Kojouharova, Ivan

    2016-01-01

    Stored antiprotons beams in the GeV range represent a unparalleled factory for hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of strange hadronic systems with unprecedented precision. The behavior of hyperons and -- for the first time -- of antihyperons in nuclear systems can be studied under well controlled conditions. The exclusive production of $\\Lambda\\bar{\\Lambda}$ and $\\Sigma^-\\bar{\\Lambda}$ pairs in antiproton-nucleus interactions probe the neutron and proton distribution in the nuclear periphery and will help to sample the neutron skin. For the first time, high resolution $\\gamma$-spectroscopy of doubly strange nuclei will be performed, thus complementing measurements of ground state decays of double hypernuclei with mesons beams at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange $\\Xi$-atoms are feasible and even the pr...

  20. The Antiproton Accumulator (AA)

    CERN Multimedia

    1980-01-01

    Section 06 - 08*) of the AA where the dispersion (and hence the horizontal beam size) is large. One can distinguish (left to right): A vacuum-tank, two bending magnets (BST06 and BST07 in blue) with a quadrupole (QDN07, in red) in between, another vacuum-tank, a wide quadrupole (QFW08) and a further tank . The tanks are covered with heating tape for bake-out. The tank left of BST06 contained the stack core pickup for stochastic cooling (see 7906193, 7906190, 8005051), the two other tanks served mainly as vacuum chambers in the region where the beam was large. Peter Zettwoch works on BST06. *) see: H. Koziol, Antiproton Accumulator Parameter List, PS/AA/Note 84-2 (1984)

  1. Segmented scintillation detectors with silicon photomultiplier readout for measuring antiproton annihilations

    CERN Document Server

    Sótér, A; Kobayashi, T; Barna, D; Horvath, D; Hori, M

    2014-01-01

    The Atomic Spectroscopy and Collisions Using Slow Antiprotons (ASACUSA) experiment at the Antiproton Decelerator (AD) facility of CERN constructed segmented scintillators to detect and track the charged pions which emerge from antiproton annihilations in a future superconducting radiofrequency Paul trap for antiprotons. A system of 541 cast and extruded scintillator bars were arranged in 11 detector modules which provided a spatial resolution of 17 mm. Green wavelength-shifting fibers were embedded in the scintillators, and read out by silicon photomultipliers which had a sensitive area of 1 x 1 mm^2. The photoelectron yields of various scintillator configurations were measured using a negative pion beam of momentum p ~ 1 GeV/c. Various fibers and silicon photomultipliers, fiber end terminations, and couplings between the fibers and scintillators were compared. The detectors were also tested using the antiproton beam of the AD. Nonlinear effects due to the saturation of the silicon photomultiplier were seen a...

  2. Antihydrogen and mirror-trapped antiproton discrimination: Discriminating between antihydrogen and mirror-trapped antiprotons in a minimum-B trap

    OpenAIRE

    Amole, C.; Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Butler, E.; Cesar, C. L.; S. Chapman; Charlton, M.; Deller, A.; Eriksson, S.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.

    2012-01-01

    Recently, antihydrogen atoms were trapped at CERN in a magnetic minimum (minimum-B) trap formed by superconducting octupole and mirror magnet coils. The trapped antiatoms were detected by rapidly turning off these magnets, thereby eliminating the magnetic minimum and releasing any antiatoms contained in the trap. Once released, these antiatoms quickly hit the trap wall, whereupon the positrons and antiprotons in the antiatoms annihilated. The antiproton annihilations produce easily detected s...

  3. A comparative study on total reflection X-ray fluorescence determination of low atomic number elements in air, helium and vacuum atmospheres using different excitation sources

    International Nuclear Information System (INIS)

    A comparison of trace element determinations of low atomic number (Z) elements Na, Mg, Al, P, K and Ca in air, helium and vacuum atmospheres using W Lβ1, Mo Kα and Cr Kα excitations has been made. For Mo Kα and W Lβ1 excitations a Si (Li) detector with beryllium window was used and measurements were performed in air and helium atmospheres. For Cr Kα excitation, a Si (Li) detector with an ultra thin polymer window (UTW) was used and measurements were made in vacuum and air atmospheres. The sensitivities of the elemental X-ray lines were determined using TXRF spectra of standard solutions and processing them by IAEA QXAS program. The elemental concentrations of the elements in other solutions were determined using their TXRF spectra and pre-determined sensitivity values. The study suggests that, using the above experimental set up, Mo Kα excitation is not suited for trace determination of low atomic number element. Excitation by WLβ1 and helium atmosphere, the spectrometer can be used for the determination of elements with Z = 15 (P) and above with fairly good detection limits whereas Cr Kα excitation with ultra thin polymer window and vacuum atmosphere is good for the elements having Z = 11 (Na) and above. The detection limits using this set up vary from 7048 pg for Na to 83 pg for Ti. - Highlights: • TXRF conditions are optimized for low atomic number (Z) element determinations. • Mo Kα with Be window detector can be used for elements with Z ≥ 20 (K). • W Lβ1 with Be window detector can be used for elements with Z ≥ 15 (P). • Cr Kα, UTW detector and vacuum atmosphere are suitable for elements with Z ≥ 11 (Na). • For the elements with Z ≥ 11 (Na), a separate study is needed

  4. Antiproton Star Observed in Emulsion

    Energy Technology Data Exchange (ETDEWEB)

    Chamberlain, Owen; Chupp, Warren W.; Goldhaber, Gerson; Segre,Emilio; Wiegand, Clyde; Amaldi, E.; Baroni, G.; Castagnoli, C.; Franzinetti, C.; Manfredini, A.

    1955-12-01

    In connection with the antiproton investigation at the Bevatron we planned and carried out a photographic-emulsion exposure in a magnetically selected beam of negative particles. The magnetic system was identical to the first half (one deflecting magnet and one magnetic lens) of the system used in the antiproton experiment of Chamberlain, Segre, Wiegand, and Ypsilantis. The selected particles left the copper target in the forward direction with momentum 1.09 Bev/c.

  5. Equal energy sharing double photo ionization of the Helium atom at 20eV and 40eV above threshold

    OpenAIRE

    Das, J. N.; Chakrabarti, K.; Paul, S

    2003-01-01

    In this article we present triple differential cross sections for equal energy sharing kinematics for double photoionization of the helium atom at 20 and 40eV above threshold in the framework of the hyperspherical partial wave theory. This supplements our earlier work \\cite{DCP03} in which we were successful in showing fully, gauge independence of the results in our formalism. Also in this work we treat cases in which the Stokes parameter S$_1 < 1$ so that partial polarization of the photon s...

  6. Atomic and Molecular Data for State-Resolved Modelling of Hydrogen and Helium and Their Isotopes in Fusion Plasma. Summary Report of the First Research Coordination Meeting

    International Nuclear Information System (INIS)

    The First Research Coordination Meeting of the IAEA Coordinated Research Project (CRP) on 'Atomic and Molecular Data for State-Resolved Modelling of Hydrogen and Helium and Their Isotopes in Fusion Plasma' was held 10-12 August 2011 at IAEA Headquarters in Vienna. Participants reviewed the status of the database on molecular processes of H and He, identified data needs and made plans for development of new data in connection with the CRP. The proceedings of the meeting are summarized here. Participants' summaries and work plans are also provided. (author)

  7. Ab initio interaction potentials and scattering lengths for ultracold mixtures of metastable helium and alkali-metal atoms

    Science.gov (United States)

    Kedziera, Dariusz; Mentel, Łukasz; Żuchowski, Piotr S.; Knoop, Steven

    2015-06-01

    We have obtained accurate ab initio +4Σ quartet potentials for the diatomic metastable triplet helium+alkali-metal (Li, Na, K, Rb) systems, using all-electron restricted open-shell coupled cluster singles and doubles with noniterative triples corrections CCSD(T) calculations and accurate calculations of the long-range C6 coefficients. These potentials provide accurate ab initio quartet scattering lengths, which for these many-electron systems is possible, because of the small reduced masses and shallow potentials that result in a small amount of bound states. Our results are relevant for ultracold metastable triplet helium+alkali-metal mixture experiments.

  8. Non-resonant two and three-photon ionization of the singlet and triplet metastable helium atoms of an atomic jet

    International Nuclear Information System (INIS)

    The three-photon ionization cross-section of the helium metastables He(21S) and He(23S) is determined by means of the linearly polarized radiation of a pulsed ruby laser with an emission wavelength equal to 6946.4 A at 190C. Two-photon ionization, obtained by doubling the laser beam frequency, is also studied

  9. Atomic-scale Modeling of Interactions of Helium, Vacancies and Helium-vacancy Clusters with Screw Dislocations in Alpha-Iron

    Energy Technology Data Exchange (ETDEWEB)

    Heinisch, Howard L.; Gao, Fei; Kurtz, Richard J.

    2010-05-01

    The interactions of He and vacancy defects with <111> screw dislocations in alpha-Fe are modeled using molecular statics, molecular dynamics and transition state energy determinations. The formation energies and binding energies of interstitial He atoms, vacancies and He-vacancy clusters near and within dislocations in alpha-Fe are determined at various locations relative to the dislocation core. Using the dimer transition state method the migration energies and trajectories of the He and vacancy defects near and within the screw dislocation are also determined. Both interstitial He atoms and single vacancies are attracted to and trapped in the dislocation core region, and they both migrate along the dislocation line with a migration energy of about 0.4 eV, which is about half the migration energy of vacancies in the perfect crystal and about five times the migration energy for interstitial He in the perfect crystal. Divacancies and He-divacancy complexes have migration properties within the dislocation core that are similar to those in the perfect crystal, although the stability of these defects within the dislocation may be somewhat less than in the perfect crystal.

  10. Magnetic Field Effects on the 1083 nm Atomic Line of Helium. Optical Pumping of Helium and Optical Polarisation Measurement in High Magnetic Field

    CERN Document Server

    Courtade, E; Nacher, P J; Tastevin, G; Kiersnowski, K; Dohnalik, T

    2002-01-01

    The structure of the excited $2^{3}$S and $2^{3}$P triplet states of $^{3}$He and $^{4}$He in an applied magnetic field B is studied using different approximations of the atomic Hamiltonian. All optical transitions (line positions and intensities) of the 1083 nm $2^{3}$S-$2^{3}$P transition are computed as a function of B. The effect of metastability exchange collisions between atoms in the ground state and in the $2^{3}$S metastable state is studied, and rate equations are derived, for the populations these states in the general case of an isotopic mixture in an arbitrary field B. It is shown that the usual spin-temperature description remains valid. A simple optical pumping model based on these rate equations is used to study the B-dependence of the population couplings which result from the exchange collisions. Simple spectroscopy measurements are performed using a single-frequency laser diode on the 1083 nm transition. The accuracy of frequency scans and of measurements of transition intensities is studie...

  11. Depth-Dose and LET Distributions of Antiproton Beams in Various Target Materials

    DEFF Research Database (Denmark)

    Herrmann, Rochus; Olsen, Sune; Petersen, Jørgen B.B.;

    Purpose  Radiotherapy with antiprotons is still being investigated as a possible new beam modality. Antiprotons behave much like protons until they come to rest, where they will annihilate with a target nucleus, thereby releasing additional energy. This can potentially lead to a favourable  depth...... change in the depth-dose distribution and average LET when substituting the materials. Adding boron and gadolinium up to concentrations of 1 per 1000 atoms to a water phantom, did not change the depth-dose profile nor the average LET. Conclusions  According to our FLUKA calculations, antiproton neutron...

  12. The Antiproton Accumulator (AA)

    CERN Multimedia

    1980-01-01

    A section of the AA where the dispersion (and hence the horizontal beam size) is large. One can distinguish (left to right): A large vacuum-tank, a quadrupole (QDN09*), a bending magnet (BST08), another vacuum-tank, a wide quadrupole (QFW08) and (in the background) a further bending magnet (BST08). The tanks are covered with heating tape for bake-out. The tank left of QDN09 contained the kickers for stochastic pre-cooling (see 790621, 8002234, 8002637X), the other one served mainly as vacuum chamber in the region where the beam was large. Peter Zettwoch works on QFW08. * see: H. Koziol, Antiproton Accumulator Parameter List, PS/AA/Note 84-2 (1984) See under 7911303, 7911597X, 8004261 and 8202324. For photos of the AA in different phases of completion (between 1979 and 1982) see: 7911303, 7911597X, 8004261, 8004608X, 8005563X, 8005565X, 8006716X, 8006722X, 8010939X, 8010941X, 8202324, 8202658X, 8203628X .

  13. Antiprotons in the Cosmic Rays

    Science.gov (United States)

    Nutter, Scott

    1999-10-01

    The HEAT (High Energy Antimatter Telescope) collaboration flew in May 1999 a balloon-borne instrument to measure the relative abundance of antiprotons and protons in the cosmic rays to kinetic energies of 30 GeV. The instrument uses a multiple energy loss technique to measure the Lorentz factor of through-going cosmic rays, a magnet spectrometer to measure momentum, and several scintillation counters to determine particle charge and direction (up or down in the atmosphere). The antiproton/proton abundance ratio as a function of energy is a probe of the propagation environment of protons through the galaxy. Existing measurements indicate a higher than expected value at both high and low energies. A confirming measurement could indicate peculiar antiproton sources, such as WIMPs or supersymmetric darkmatter candidates. A description of the instrument, details of the flight and instrument performance, and status of the data analysis will be given.

  14. Nuclear dynamics induced by antiprotons

    CERN Document Server

    Feng, Zhao-Qing

    2015-01-01

    Reaction dynamics in collisions of antiprotons on nuclei is investigated within the Lanzhou quantum molecular dynamics model. The reaction channels of elastic scattering, annihilation, charge exchange and inelastic collisions of antiprotons on nucleons have been included in the model. Dynamics on particle production, in particular pions, kaons, antikaons and hyperons, is investigated in collisions of $\\overline{p}$ on $^{12}$C, $^{20}$Ne, $^{40}$Ca and $^{181}$Ta from a low to high incident momenta. It is found that the annihilations of $\\overline{p}$ on nucleons are of importance on the dynamics of particle production in phase space. Hyperons are mainly produced via meson induced reactions on nucleons and strangeness exchange collisions, which lead to the delayed emission in antiproton-nucleus collisions.

  15. Antiproton annihilation in quantum chromodynamics

    International Nuclear Information System (INIS)

    Anti-proton annihilation has a number of important advantages as a probe of QCD in the low energy domain. Exclusive reaction in which complete annihilation of the valance quarks occur. There are a number of exclusive and inclusive /bar p/ reactions in the intermediate momentum transfer domain which provide useful constraints on hadron wavefunctions or test novel features of QCD involving both perturbative and nonperturbative dynamics. Inclusive reactions involving antiprotons have the advantage that the parton distributions are well understood. In these lectures, I will particularly focus on lepton pair production /bar p/A → /ell//bar /ell//X as a means to understand specific nuclear features in QCD, including collision broadening, breakdown of the QCD ''target length condition''. Thus studies of low to moderate energy antiproton reactions with laboratory energies under 10 GeV could give further insights into the full structure of QCD. 112 refs., 40 figs

  16. Effects of autoionization in electron loss from helium-like highly charged ions in collisions with photons and fast atomic particles

    CERN Document Server

    Lyashchenko, K N; Voitkiv, A B

    2016-01-01

    We study theoretically single electron loss from helium-like highly charged ions involving excitation and decay of autoionizing states of the ion. Electron loss is caused by either photo absorption or the interaction with a fast atomic particle (a bare nucleus, a neutral atom, an electron). The interactions with the photon field and the fast particles are taken into account in the first order of perturbation theory. Two initial states of the ion are considered: $1s^2$ and $(1s2s)_{J=0}$. We analyze in detail how the shape of the emission pattern depends on the atomic number $Z_{I}$ of the ion discussing, in particular, the inter-relation between electron loss via photo absorption and due to the impact of atomic particles in collisions at modest relativistic and extreme relativistic energies. According to our results, in electron loss from the $1s^2$ state autoionization may substantially influence the shape of the emission spectra only up to $Z_{I} \\approx 35-40$. A much more prominent role is played by autoi...

  17. A high resolution helium atom scattering and far infrared study of the dynamics and the lateral potential energy surface of CO molecules chemisorbed on Cu(001)

    International Nuclear Information System (INIS)

    Inelastic helium scattering (HAS) and infrared reflection adsorption spectroscopy (IRAS) have been used to measure the isotope shifts of the frequencies of both the parallel and perpendicular frustrated translation modes, as well as the frustrated rotation mode of CO molecules at on top sites on Cu(001). The measured isotope shifts for four different isotopomers indicates a significant rotational contribution to the parallel frustrated translation (T-mode), where the vibrational amplitude of the oxygen atom is significantly larger than for the carbon atom. Conversely, for the frustrated rotation the vibrational amplitude of the carbon atom was observed to be larger than for the oxygen atom. At surface temperatures above Ts=100 K a careful analysis of the peak shape of the HAS quasielastic peak shows a small broadening, which is attributed to a rapid diffusion of the CO molecules. The measured dynamic diffusion barrier of 31±10 meV is compatible with the shape of the potential at the on-top site and makes it possible to extend the potential energy surface to the region between the on-top sites. copyright 1998 American Institute of Physics

  18. Calculation of the density shift and broadening of the transition lines in pionic helium: Computational problems

    Energy Technology Data Exchange (ETDEWEB)

    Bakalov, Dimitar, E-mail: dbakalov@inrne.bas.bg [Bulgarian Academy of Sciences, INRNE (Bulgaria)

    2015-08-15

    The potential energy surface and the computational codes, developed for the evaluation of the density shift and broadening of the spectral lines of laser-induced transitions from metastable states of antiprotonic helium, fail to produce convergent results in the case of pionic helium. We briefly analyze the encountered computational problems and outline possible solutions of the problems.

  19. Efficient accumulation of antiprotons and positrons, production of slow mono-energetic beams, and their applications

    CERN Document Server

    Yamazaki, Yasunori

    2004-01-01

    Recent progress of ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) project, particularly the antiproton trapping and slow antiproton production, is discussed. An RFQD (Radio Frequency Quadrupole Decelerator) installed in the ASACUSA beam line has an excellent deceleration efficiency of 25% providing 10-130keV antiprotons, which improves the final accumulation efficiency at least one and half orders of magnitude. The decelerated antiprotons are then injected in a large volume multiring trap, stored, and electron-cooled. About 1 million antiprotons are successfully accumulated per one AD shot and 10-500eV antiprotons are extracted as a mono-energetic beam. A UHV compatible positron accumulation is newly developed combining electron plasma and an ion cloud, which yields an accumulation rate as high as 400e **+s/mCi, two and a half orders of magnitude higher than other UHV compatible schemes. A new scheme to synthesize a spin-polarized antihydrogen beam is also discussed, which will play a vit...

  20. Beam Dynamics Studies and Design Optimisation of New Low Energy Antiproton Facilities

    CERN Document Server

    Resta-Lopez, Javier; Welsch, Carsten P

    2016-01-01

    Antiprotons, stored and cooled at low energies in a storage ring or at rest in traps, are highly desirable for the investigation of a large number of basic questions on fundamental interactions. This includes the static structure of antiprotonic atomic systems and the time-dependent quantum dynamics of correlated systems. The Antiproton Decelerator (AD) at CERN is currently the worlds only low energy antiproton factory dedicated to antimatter experiments. New antiproton facilities, such as the Extra Low ENergy Antiproton ring (ELENA) at CERN and the Ultra-low energy Storage Ring (USR) at FLAIR, will open unique possibilities. They will provide cooled, high quality beams of extra-low energy antiprotons at intensities exceeding those achieved presently at the AD by factors of ten to one hundred. These facilities, operating in the energy regime between 100 keV down to 20 keV, face several design and beam dynamics challenges, for example nonlinearities, space charge and scattering effects limiting beam life time....

  1. A fussy revisitation of antiprotons as a tool for Dark Matter searches

    CERN Document Server

    Boudaud, Mathieu

    2015-01-01

    Antiprotons are regarded as a powerful probe for Dark Matter (DM) indirect detection and indeed current data from \\PAMELA\\ have been shown to lead to stringent constraints. However, in order to exploit their constraining/discovery power properly, great attention must be put into effects (linked to their propagation in the Galaxy) which may be perceived as subleading but actually prove to be quite relevant. We revisit the computation of the astrophysical background and of the DM antiproton fluxes fully including the effects of: diffusive reacceleration, energy losses including tertiary component and solar modulation (in a force field approximation). Using the updated proton and helium fluxes just released by the \\AMS\\ experiment we reevaluate the secondary astrophysical antiproton to proton ratio and its uncertainties, and compare it with the ratio preliminarly reported by \\AMS. We find no unambiguous evidence for a significant excess with respect to expectations. Yet, some preference for a flatter energy depe...

  2. LEAR (Low Energy Antiproton Ring), general view.

    CERN Multimedia

    1990-01-01

    When the Antiproton Project was launched in the late 1970s, it was recognized that in addition to the primary purpose of high-energy proton-antiproton collisions in the SPS, there was interesting physics to be done with low-energy antiprotons. In 1982, LEAR was ready to receive antiprotons from the Antiproton Accumulator (AA), via the PS. A year later, delivery of antiprotons to the experiments began, at momenta as low as 100 MeV/c (kinetic energy 5.3 MeV), in an "Ultra-Slow Extraction" mode, dispensing some E9 antiprotons over times counted in hours. For such an achievement, stochastic and electron cooling had to be brought to high levels of perfection.

  3. Withdrawal of Chinese Physics Letters 28 (2011) 043401 “Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps” by WANG Ji-Cheng et al.

    Institute of Scientific and Technical Information of China (English)

    WANG Ji-Cheng; ZHOU Ke-Ya; WANG Yue-Yuan; LIAO Qing-Hong; LIU Shu-Tian

    2011-01-01

    We announce the withdrawal of the article entitled “Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps”,which was published in Chinese Physics Letters [28(4)(2011)043401].The first author,Jicheng Wang,had participated in related research with Professor Kirk Madison's group at the Department of Physics & Astronomy at the University of British Columbia,Canada from September 2008 to February 2010.Even though consent had been granted for some of the experimental data to be used by Jicheng Wang in his own thesis,its publication had not been authorized.We apologize to Professor K.Madison for the misunderstanding,and to Chinese Physics Letters and the readers of Chinese Physics Letters for any inconvenience this mistake may have caused.%We announce the withdrawal of the article entitled "Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps", which was published in Chinese Physics Letters [28(4) (2011)043401]. The first author, Jicheng Wang, had participated in related research with Professor Kirk Madison's group at the Department of Physics & Astronomy at the University of British Columbia, Canada from September 2008 to February 2010. Even though consent had been granted for some of the experimental data to be used by Jicheng Wang in his own thesis, its publication had not been authorized. We apologize to Professor K. Madison for the misunderstanding, and to Chinese Physics Letters ad the readers of Chinese Physics Letters for any inconvenience this mistake may have caused.

  4. Equal energy sharing double photoionization of the helium atom at 20 eV and 40 eV above threshold

    International Nuclear Information System (INIS)

    In this Letter we present triple differential cross sections for equal energy sharing kinematics for double photoionization of the helium atom at 20 and 40 eV above threshold in the framework of the hyperspherical partial wave theory. This supplements our earlier work [J. Phys. B: At. Mol. Opt. Phys. 36 (2003) 2707] in which we were successful in showing fully, gauge independence of the results in our formalism. Also in this Letter we treat cases in which the Stokes parameter S1<1 so that partial polarization of the photon source is also taken into account. Agreement in shape with the convergent close coupling [A.S. Kheifets, 2003, private communication; H. Braeuning, et al., J. Phys. B: At. Mol. Opt. Phys. 31 (1998) 5149] calculation and the experiments appears to be excellent

  5. Some prospects for antiproton physics

    International Nuclear Information System (INIS)

    Some of the possibilities for fruitful research with antiprotons are outlined below. Special emphasis is placed on the possibility of learning about quark spectroscopy and dynamics using highly precise and intense anti p beams such as LEAR. It is urged that any discussion of LAMPF II give very careful consideration to the construction of a facility competitive with LEAR

  6. Biological Effectiveness of Antiproton Annihilation

    DEFF Research Database (Denmark)

    Maggiore, C.; Agazaryan, N.; Bassler, N.;

    2004-01-01

    A new experiment, AD-4/ACE (antiproton cell experiment), has been approved by the CERN Research Board. The experiment is scheduled to begin taking data in June and continue through the 2003 run cycle. The experiment is designed to determine whether or not the densely ionizing particles emanating...

  7. Antiproton Stacking in the Recycler

    CERN Document Server

    Burov, A

    2003-01-01

    Possibilities to accumulate antiprotons in the Recycler are considered for three different cases: with current stochastic cooling, with upgraded stochastic cooling and with electron cooling. With stochastic cooling only, even upgraded, Recycler looks hardly useful. However, with electron cooling at its goal parameters and reasonably good vacuum in the Recycler, this machine would be efficient.

  8. Proton-Antiproton Collider Physics

    OpenAIRE

    Shochet, Melvyn J.

    1995-01-01

    Comment: Summary of the 10th Topical Workshop on Proton-Antiproton Collider Physics, Fermilab, May 9-13, 1995. Postscript file (34 pages with 82 embedded figures; 5.7 MB) available at http://www-cdf.fnal.gov/physics/conf95/cdf3225_pbarp_wkshp_summary.ps

  9. Continuous-flow determination of aqueous sulfur by atmospheric-pressure helium microwave-induced plasma atomic emission spectrometry with gas-phase sample introduction

    Science.gov (United States)

    Nakahara, Taketoshi; Mori, Toshio; Morimoto, Satoru; Ishikawa, Hiroshi

    1995-06-01

    A simple continuous-flow generation of volatile hydrogen sulfide and sulfur dioxide by acidification of aqueous sulfide and sulfite ions, respectively, is described for the determination of low concentrations of sulfur by atmospheric-pressure helium microwave-induced plasma atomic emission spectrometry (MIP-AES) in the normal ultraviolet (UV) and vacuum ultraviolet (VUV) regions of the spectrum. For measuring spectral lines in the VUV region, the monochromator and the enclosed external optical path between the MIP source and the entrance slit of the monochromator have both been purged with nitrogen to minimize oxygen absorption below 190 nm. Sulfur atomic emission lines at 180.73, 182.04 and 217.05 nm have been selected as the analytical lines. Of the various acids examined, 1.0 M hydrochloric acid is the most favorable for both the generation of hydrogen sulfide from sulfide ions and sulfur dioxide from sulfite ions. Either generated hydrogen sulfide or sulfur dioxide is separated from the solution in a simple gas-liquid separator and swept into the helium stream of a microwave-induced plasma for analysis. The best attainable detection limits (3 σ criterion) for sulfur at 180.73 nm were 0.13 and 1.28 ng ml -1 for the generation of hydrogen sulfide and sulfur dioxide, respectively, with the corresponding background equivalent concentrations of 20.9 and 62.2 ng ml -1 in sulfur concentration. The typical analytical working graphs obtained under the optimized experimental conditions were rectilinear over approximately four orders of magnitude in sulfur concentration. The present method has been successfully applied to the recovery test of the sulfide spiked to waste water samples and to the determination of sulfite in some samples of commercially available wine.

  10. Field ionization of helium in a supersonic beam: Kinetic energy of neutral atoms and probability of their field ionization

    International Nuclear Information System (INIS)

    High detection efficiency combined with spatial resolution on a nm-scale makes the field ionization process a promising candidate for spatially resolved neutral particles detection. The effective cross-sectional area σeff can serve as a measure for the effectiveness of such a field ion detector. In the present contribution, we combine quantum-mechanical calculations of the field-modified electron density distribution near the tungsten tip surface and of the resulting local field distributions, performed using the functional integration method, with a classical treatment of the atom trajectories approaching the tip in order to calculate the σeff values for ionization of free He atoms over an apex of a tungsten field emitter tip. The calculated values are compared with experimental data for supersonic He atomic beams at two different temperatures 95 and 298 K.

  11. Collisional ionization of excited helium atoms He(n1P) in intermediate Rydberg states by polar or high electronic affinity molecules

    International Nuclear Information System (INIS)

    Collisional ionization of selectively excited helium atoms in the intermediate Rydberg states n1P (n = 14, 15, or 16) is studied in a crossed beam machine. An important He+ ion signal is detected for two types of target: (1) polar molecules (NH3, SO2, C3H60) where MJ + He(n1p) yields M(J') + He + e-; and (2) molecules with great electronic affinity (SF6, NO2) where M + He(n1P) yields M- + He+. For each of these processes, the variation of the collision as a function of kinetic energy, and the absolute value of the ionization cross section in the thermal domain (200 to 500 MeV) are measured. The results cannot be interpreted with the free electron model, which reduces the interactions in the process studied to only the Rydberg electron-molecule interaction, which is treated by bipolar Born approximation. This model predicts: no ionization of Rydberg atoms near n=14 for system (1), whereas large cross sections, attributed to molecular relaxation transitions of several quanta of rotational energy are measured; and a v-1r velocity dependence of the cross section, whereas different behavior is observed experimentally (for (1) a v-2r monotone decrease, for (2) a curve showing a maximum)

  12. A high-resolution infrared spectroscopic investigation of the halogen atom-HCN entrance channel complexes solvated in superfluid helium droplets

    CERN Document Server

    Merritt, J M; Miller, R E; K\\"upper, Jochen; Merritt, Jeremy M.; Miller, Roger E.

    2006-01-01

    Rotationally resolved infrared spectra are reported for the X-HCN (X = Cl, Br, I) binary complexes solvated in helium nanodroplets. These results are directly compared with that obtained previously for the corresponding X-HF complexes [J. M. Merritt, J. K\\"upper, and R. E. Miller, PCCP, 7, 67 (2005)]. For bromine and iodine atoms complexed with HCN, two linear structures are observed and assigned to the $^{2}\\Sigma_{1/2}$ and $^{2}\\Pi_{3/2}$ ground electronic states of the nitrogen and hydrogen bound geometries, respectively. Experiments for HCN + chlorine atoms give rise to only a single band which is attributed to the nitrogen bound isomer. That the hydrogen bound isomer is not stabilized is rationalized in terms of a lowering of the isomerization barrier by spin-orbit coupling. Theoretical calculations with and without spin-orbit coupling have also been performed and are compared with our experimental results. The possibility of stabilizing high-energy structures containing multiple radicals is discussed, ...

  13. Example of an Antiproton-Nucleon Annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Chamberlain, O.; Chupp, W.W.; Ekspong, A.G.; Goldhaber, G.; Goldhaber, S.; Lofgren, E.J.; Segre, E.; Wiegand, C.; Amaldi, E.; Baroni,G.; Castagnoli, C.; Franzinetti, C.; Manfredini, A.

    1956-02-27

    The existence of antiprotons has recently been demonstrated at the Berkeley Bevatron by a counter experiment. The antiprotons were found among the momentum-analyzed (1190 Mev/c) negative particles emitted by a copper target bombarded by 6.2-Bev protons. Concurrently with the counter experiment, stacks of nuclear emulsions were exposed in the beam adjusted to 1090 Mev/c negative particles in an experiment designed to observe the properties of antiprotons when coming to rest. This required a 132 g/cm2 copper absorber to slow down the antiprotons sufficiently to stop them in the emulsion stack. Only one antiproton was found in stacks in which seven were expected, assuming a geometric interaction cross section for antiprotons in copper. It has now been found that the cross section in copper is about twice geometric, which explains this low yield.

  14. Antiproton source beam position system

    International Nuclear Information System (INIS)

    The TeV I Beam Position Monitor (BPM) system is designed to provide a useful diagnostic tool during the commissioning and operational phases of the antiproton source. Simply stated the design goal is to provide single turn position information for intensities of > 1x109 particles, and multi-turn (clocked orbit) information for beam intensities of > 1x107 particles, both with sub-millimeter resolution. It is anticipated that the system will be used during commissioning for establishing the first turn through the Debuncher and Accumulator, for aligning injection orbits, for providing information necessary to correct closed orbits, and for measuring various machine parameters (e.g. tunes, dispersion, aperture, chromaticity). During normal antiproton operation the system will be used to monitor the beam position throughout the accumulation process

  15. Radiation studies in the antiproton source

    International Nuclear Information System (INIS)

    Experiment E760 has a lead glass (Pb-G) calorimeter situated in the antiproton source tunnel in the accumulator ring at location A50. This location is exposed to radiation from several sources during antiproton stacking operations. A series of radiation studies has been performed over the last two years to determine the sources of this radiation and as a result, some shielding has been installed in the antiproton source in order to protect the lead glass from radiation damage

  16. Enhanced creation of dispersive monolayer phonons in Xe/Pt(111) by inelastic helium atom scattering at low energies

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Bruch, Ludwig Walter

    2007-01-01

    an absorbing potential at large distance. The times now extend to beyond 100 ps and enable a clarification of processes involving transient trapping of the He atoms. The wave packet is made more monochromatic by significantly increasing the spatial width of the initial Gaussian shape. The narrower...

  17. Partial and total electronic stopping cross sections of atoms for a singly charged helium ion, Part 2

    International Nuclear Information System (INIS)

    Partial and total electronic stopping cross sections of atoms with Z (55 ≤ Z ≤ 92) for a He+ ion are tabulated as the second part of NIFS-DATA-11 (1991) on the basis of the wave-packet theory. (author)

  18. Liquid helium

    CERN Document Server

    Atkins, K R

    1959-01-01

    Originally published in 1959 as part of the Cambridge Monographs on Physics series, this book addresses liquid helium from the dual perspectives of statistical mechanics and hydrodynamics. Atkins looks at both Helium Three and Helium Four, as well as the properties of a combination of the two isotopes. This book will be of value to anyone with an interest in the history of science and the study of one of the universe's most fundamental elements.

  19. Search for Polarization Effects in the Antiproton Production Process

    International Nuclear Information System (INIS)

    For the production of a polarized antiproton beam, various methods have been suggested including the possibility that antiprotons may be produced polarized which will be checked experimentally. The polarization of antiprotons produced under typical conditions for antiproton beam preparation will be measured at the CERN/PS. If the production process creates some polarization, a polarized antiproton beam could be prepared by a rather simple modification of the antiproton beam facility. The detection setup and the expected experimental conditions are described

  20. Physics with Antiprotons at PANDA

    International Nuclear Information System (INIS)

    The PANDA experiment is part of the core project of the planned Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt (Germany)[1]. One major component of the upgraded accelerator complex is the High Energy Storage Ring (HESR) which will provide a high quality antiproton beam in the momentum range between 1.5 and 15 GeV/c. PANDA, a fixed target experiment directly implemented in the HESR, will investigate antiproton annihilations with the aim to explore fundamental questions in the cross over region of the non perturbative and the strong QCD. Due to the planned extensive physics program a multipurpose detector with a nearly complete solid angle coverage, proper particle identification over a large momentum range, and high resolution calorimetry for neutral particles is required. After an overview about the goals and the detector design of the PANDA experiment major parts of the planned physics program will be discussed, namely the meson spectroscopy and the search for exotics in the charmonium and open charm region

  1. Ultra-low Energy Antiprotons at FLAIR

    OpenAIRE

    Welsch, C.; Grieser, M.; von Hahn, R; Orlov, D.; Wolf, A.; Ullrich, J.

    2004-01-01

    The Future Accelerator Facility for Beams of Ions and Antiprotons at Darmstadt will produce the highest flux of antiprotons in the world. So far it is foreseen to accelerate the antiprotons to high energies (3-15 GeV) for meson spectroscopy and other nuclear and particle physics experiments in the HESR (High Energy Storage Ring). Within the planned complex of storage rings, it is possible to decelerate the antiprotons to about 30 MeV kinetic energy, opening up the possibility to create low en...

  2. Penning and associative ionisations of argon atoms by collisions with metastable helium atoms He(21S) and He(23S) of thermal energies 0.03-0.40eV

    International Nuclear Information System (INIS)

    This work, devoted to the 21S and 23S metastable states of the helium atom, is mainly experimental. It centres on observation of the non-bound states Ar+ and bound states HeAr+ created during collisions of these metastable atoms with argon atoms in the ground state. The Penning and associative ionisation cross-sections corresponding to these two processes were obtained as a function of the relative speed of approach of the He*+Ar particles in the thermal region 1200-4500m/s (0.3-0.40eV). The experimental time of flight method used in this experiment is original in its application to the measurement of reaction products such as Ar+ and HeAr+ ions. The results obtained testify to the efficiency of this method since the variations in the Penning ionisation cross-section sigmasub(IP)(v) and associative ionisation cross-section sigmasub(IA)(v) against speed have not been observed in other laboratories. They are given here for the couples He(23S)+Ar and He(21S) + Ar. The theoretical interpretation attempted for the cross-sections sigmasub(IP)(v) and sigmasub(IA)(v) is based on a very recent model due to the American school of Miller and the Japanese school of Nakamura. This model, common to all interpretations, can lead to different results according to whether quantum effects are taken into account

  3. Molecular Dynamics Simulations of Helium Behaviour in Titanium Crystals

    Institute of Scientific and Technical Information of China (English)

    SUN Tie-Ying; LONG Xing-Gui; WANG Jun; HOU Qing; WU Zhong-Cheng; PENG Shu-Ming; LUO Shun-Zhong

    2008-01-01

    Molecular dynamics simulations are performed to investigate the behaviour of helium atoms in titanium at a temperature of 300 K.The nucleation and growth of helium bubble has been simulated up to 50 helium atoms.The approach to simulate the bubble growth is to add helium atoms one by one to the bubble and let the system evolve.The titanium cohesion is based on the tight binding scheme derived from the embedded atom method,and the helium-titanium interaction is characterized by fitted potential in the form of a Lennard-Jones function.The pressure in small helium bubbles is approximately calculated.The simulation results show that the pressure will decrease with the increasing bubble size,while increase with the increasing helium atoms.An analytic function about the quantitative relationship of the pressure with the bubble size and number of helium atoms is also fitted.

  4. Theoretical state-selective and total cross sections for electron capture from helium atoms by fully stripped ions

    Science.gov (United States)

    Mančev, I.; Milojević, N.; Belkić, Dž.

    2015-03-01

    The four-body boundary-corrected first Born (CB1-4B) approximation is used to compute cross sections for single electron capture from helium targets by fully stripped ions. The projectile ions are H+, He2+, Li3+, Be4+, B5+, C6+, N7+, O8+, and F9+. An extensive list of theoretical state-to-state cross sections in these collisions at energies ranging from 20 to 10 000 keV/amu is given. This list includes the state-selective cross sections Qnlm for each individual triple of the usual quantum numbers { n , l , m } of the final hydrogen-like states alongside Qnl and Qn for the pertinent sub-shells and shells where the respective summations over m and { l , m } have been carried out. The maximal value of the principal quantum number n was chosen to vary from 4 (H+) to 10 (F9+) so as to satisfy the condition n ≥ZP, where ZP is the nuclear charge of the projectile. Usually, the largest cross sections stem from those values of n that match the projectile charge (n =ZP) . The total cross sections for capture summed over all the quantum numbers { n , l , m } are also tabulated. The overall goal of this study is to fill in lacunae in the existing databases of charge exchange cross sections that are needed in several inter-disciplinary fields. For example, in particle transport physics, which is of utmost importance in such emerging branches as hadron therapy, these cross sections constitute a part of the multifaceted input data for stochastic simulations of energy losses of multiply charged ions in matter, including tissue. Other significant uses of the present data are anticipated in charge exchange diagnostics within thermonuclear research project as well as in applications covering the relevant parts of plasma physics and astrophysics.

  5. Spatial profiles of electron and metastable atom densities in positive polarity fast ionization waves sustained in helium

    International Nuclear Information System (INIS)

    Fast ionization waves (FIWs), often generated with high voltage pulses over nanosecond timescales, are able to produce large volumes of ions and excited states at moderate pressures. The mechanisms of FIW propagation were experimentally and computationally investigated to provide insights into the manner in which these large volumes are excited. The two-dimensional structure of electron and metastable densities produced by short-pulse FIWs sustained in helium were measured using laser-induced fluorescence and laser collision-induced fluorescence diagnostics for times of 100–120 ns after the pulse, as the pressure was varied from 1 to 20 Torr. A trend of center-peaked to volume-filling to wall-peaked electron density profiles was observed as the pressure was increased. Instantaneous FIW velocities, obtained from plasma-induced emission, ranged from 0.1 to 3 × 109 cm s−1, depending on distance from the high voltage electrode and pressure. Predictions from two-dimensional modeling of the propagation of a single FIW correlated well with the experimental trends in electron density profiles and wave velocity. Results from the model show that the maximum ionization rate occurs in the wavefront, and the discharge continues to propagate forward after the removal of high voltage from the powered electrode due to the potential energy stored in the space charge. As the pressure is varied, the radial distribution of the ionization rate is shaped by changes in the electron mean free path, and subsequent localized electric field enhancement at the walls or on the centerline of the discharge.

  6. Spatial profiles of electron and metastable atom densities in positive polarity fast ionization waves sustained in helium

    Science.gov (United States)

    Weatherford, Brandon R.; Xiong, Zhongmin; Barnat, E. V.; Kushner, Mark J.

    2014-09-01

    Fast ionization waves (FIWs), often generated with high voltage pulses over nanosecond timescales, are able to produce large volumes of ions and excited states at moderate pressures. The mechanisms of FIW propagation were experimentally and computationally investigated to provide insights into the manner in which these large volumes are excited. The two-dimensional structure of electron and metastable densities produced by short-pulse FIWs sustained in helium were measured using laser-induced fluorescence and laser collision-induced fluorescence diagnostics for times of 100-120 ns after the pulse, as the pressure was varied from 1 to 20 Torr. A trend of center-peaked to volume-filling to wall-peaked electron density profiles was observed as the pressure was increased. Instantaneous FIW velocities, obtained from plasma-induced emission, ranged from 0.1 to 3 × 109 cm s-1, depending on distance from the high voltage electrode and pressure. Predictions from two-dimensional modeling of the propagation of a single FIW correlated well with the experimental trends in electron density profiles and wave velocity. Results from the model show that the maximum ionization rate occurs in the wavefront, and the discharge continues to propagate forward after the removal of high voltage from the powered electrode due to the potential energy stored in the space charge. As the pressure is varied, the radial distribution of the ionization rate is shaped by changes in the electron mean free path, and subsequent localized electric field enhancement at the walls or on the centerline of the discharge.

  7. Pumped helium system for cooling positron and electron traps to 1.2 K

    Science.gov (United States)

    Wrubel, J.; Gabrielse, G.; Kolthammer, W. S.; Larochelle, P.; McConnell, R.; Richerme, P.; Grzonka, D.; Oelert, W.; Sefzick, T.; Zielinski, M.; Borbely, J. S.; George, M. C.; Hessels, E. A.; Storry, C. H.; Weel, M.; Müllers, A.; Walz, J.; Speck, A.

    2011-06-01

    Extremely precise tests of fundamental particle symmetries should be possible via laser spectroscopy of trapped antihydrogen ( H¯) atoms. H¯ atoms that can be trapped must have an energy in temperature units that is below 0.5 K—the energy depth of the deepest magnetic traps that can currently be constructed with high currents and superconducting technology. The number of atoms in a Boltzmann distribution with energies lower than this trap depth depends sharply upon the temperature of the thermal distribution. For example, ten times more atoms with energies low enough to be trapped are in a thermal distribution at a temperature of 1.2 K than for a temperature of 4.2 K. To date, H¯ atoms have only been produced within traps whose electrode temperature is 4.2 K or higher. A lower temperature apparatus is desirable if usable numbers of atoms that can be trapped are to eventually be produced. This report is about the pumped helium apparatus that cooled the trap electrodes of an H¯ apparatus to 1.2 K for the first time. Significant apparatus challenges include the need to cool a 0.8 m stack of 37 trap electrodes separated by only a mm from the substantial mass of a 4.2 K Ioffe trap and the substantial mass of a 4.2 K solenoid. Access to the interior of the cold electrodes must be maintained for antiprotons, positrons, electrons and lasers.

  8. Measurement of OH, NO, O and N atoms in helium plasma jet for ROS/RNS controlled biomedical processes

    Science.gov (United States)

    Yonemori, Seiya; Kamakura, Taku; Ono, Ryo

    2014-10-01

    Atmospheric-pressure plasmas are of emerging interest for new plasma applications such as cancer treatment, cell activation and sterilization. In those biomedical processes, reactive oxygen/nitrogen species (ROS/RNS) are said that they play significant role. It is though that active species give oxidative stress and induce biomedical reactions. In this study, we measured OH, NO, O and N atoms using laser induced fluorescence (LIF) measurement and found that voltage polarity affect particular ROS. When negative high voltage was applied to the plasma jet, O atom density was tripled compared to the case of positive applied voltage. In that case, O atom density was around 3 × 1015 [cm-3] at maximum. In contrast, OH and NO density did not change their density depending on the polarity of applied voltage, measured as in order of 1013 and 1014 [cm-3] at maximum, respectively. From ICCD imaging measurement, it could be seen that negative high voltage enhanced secondary emission in plasma bullet propagation and it can affect the effective production of particular ROS. Since ROS/RNS dose can be a quantitative criterion to control plasma biomedical application, those measurement results is able to be applied for in vivo and in vitro plasma biomedical experiments. This study is supported by the Grant-in-Aid for Science Research by the Ministry of Education, Culture, Sport, Science and Technology.

  9. Design study of an Antiproton Collector for the Antiproton Accumulator (ACOL)

    International Nuclear Information System (INIS)

    The Report gives a full description of an Antiproton Collector Ring which, placed around the existing Antiproton Accumulator at CERN, would enhance the antiproton flux available to both the SPS and LEAR by a factor of ten. The new ring and the focusing devices which precede it are designed to accept a much larger fraction of the antiproton production cone from the target. Each pulse of particles will be pre-cooled before being fed to the Antiproton Accumulator, where improved stochastic cooling systems will build up the stack. A full list of parameters is included. (orig.)

  10. Helium cryogenics

    CERN Document Server

    Van Sciver, Steven W

    2012-01-01

    Twenty five years have elapsed since the original publication of Helium Cryogenics. During this time, a considerable amount of research and development involving helium fluids has been carried out culminating in several large-scale projects. Furthermore, the field has matured through these efforts so that there is now a broad engineering base to assist the development of future projects. Helium Cryogenics, 2nd edition brings these advances in helium cryogenics together in an updated form. As in the original edition, the author's approach is to survey the field of cryogenics with emphasis on helium fluids. This approach is more specialized and fundamental than that contained in other cryogenics books, which treat the associated range of cryogenic fluids. As a result, the level of treatment is more advanced and assumes a certain knowledge of fundamental engineering and physics principles, including some quantum mechanics. The goal throughout the work is to bridge the gap between the physics and engineering aspe...

  11. Critical Landau Velocity in Helium Nanodroplets

    OpenAIRE

    Brauer, N. B.; Smolarek, S.; Loginov, E.; Mateo, D; A. Hernando; Pi, M.; Barranco, M.; Buma, W. J.; M. Drabbels

    2013-01-01

    The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective excitations of the helium atoms in the liquid. In the present work we determine to what extent this concept can still be applied to nanometer-scale, finite size helium systems. To this end, atoms and molecu...

  12. Observation of the antimatter helium-4 nucleus

    Czech Academy of Sciences Publication Activity Database

    Agakishiev, C.; Aggarwal, M. M.; Ahammed, Z.; Bielčík, J.; Bielčíková, Jana; Chaloupka, Petr; Chung, P.; Kapitán, Jan; Kouchpil, V.; Rusnak, J.; Šumbera, Michal; Tlustý, David

    2011-01-01

    Roč. 473, č. 7347 (2011), s. 353-356. ISSN 0028-0836 R&D Projects: GA MŠk LA09035 Institutional research plan: CEZ:AV0Z10480505 Keywords : QUARK-GLUON PLASMA * ANTIPROTONS * COLLISIONS * ELECTRON Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 36.280, year: 2011

  13. The Fermilab proton-antiproton collider upgrades

    International Nuclear Information System (INIS)

    The plans for increases in the Tevatron proton-antiproton collider luminosity in the near future (Run II) and the more distant future (TeV33) are described. While there are many important issues, the fundamental requirement is to produce more antiprotons and to use them more efficiently

  14. Antiproton radiation found effective in cancer research

    CERN Multimedia

    2003-01-01

    "An international collaboration of scientists has completed the first ever antiproton beam experiments designed to reveal the biological effectiveness of antiproton radiation in terminating cells used for cancer research...PBar Labs assembled the collaboration at CERN (European Organization for Nuclear Research in Geneva) to perform the measurements" (1 page).

  15. Electron transfer processes in collisions of highly charged energetic (0. 1 to 1. 0 MeV/nucleon) ions with helium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Datz, S.; Hippler, R.; Andersen, L.H.; Dittner, P.F.; Knudsen, H.; Krause, H.F.; Miller, P.D.; Pepmiller, P.L.; Rosseel, T.; Stolterfoht, N.

    1987-01-01

    We have investigated charge transfer in collisions of energetic (0.1 - 1 MeV/nucleon) highly charged ions with helium atoms with the principal aim clarifying the nature of two-electron processes. The sensitivity of partial charge-changing cross sections (i.e., single- and double-charge transfer, transfer ionization (TI), and single and double ionization) to core configuration and scaling rules for one- and two-electron processes were investigated with iodine ions (q = 5+ ..-->.. 26+) and uranium ions (q = 17+ ..-->.. 44+) using an ion-charge state, recoil-ion coincidence method. Using zero-degree electron spectroscopy in coincidence with charge transfer, we found that at the higher energies, as in the case of 0.1 MeV/nucleon ions previously reported, TI involves the transfer of two electrons to a higher correlated state followed by loss of one electron to the continuum. In addition, we observe very high Rydberg electrons in coincidence with TI, implying a possible up-down correlation in the pair transfer. In addition, we made measurements of VUV photons emitted at the collision in coincidence with He/sup +/ and He/sup 2 +/ recoils. The results show that TI leads to capture into lower n states than single-charge transfer. 15 refs., 10 figs.

  16. Antihydrogen formation by autoresonant excitation of antiproton plasmas

    International Nuclear Information System (INIS)

    In efforts to trap antihydrogen, a key problem is the vast disparity between the neutral trap energy scale (∼ 50 μeV), and the energy scales associated with plasma confinement and space charge (∼1 eV). In order to merge charged particle species for direct recombination, the larger energy scale must be overcome in a manner that minimizes the initial antihydrogen kinetic energy. This issue motivated the development of a novel injection technique utilizing the inherent nonlinear nature of particle oscillations in our traps. We demonstrated controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm or tenuous plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination. The nature of this injection overcomes some of the difficulties associated with matching the energies of the charged species used to produce antihydrogen.

  17. The stereo-dynamics of collisional autoionization of ammonia by helium and neon metastable excited atoms through molecular beam experiments

    Energy Technology Data Exchange (ETDEWEB)

    Falcinelli, Stefano, E-mail: stefano.falcinelli@unipg.it; Vecchiocattivi, Franco [Department of Civil and Environmental Engineering, University of Perugia, Via G. Duranti 93, 06125 Perugia (Italy); Bartocci, Alessio; Cavalli, Simonetta; Pirani, Fernando [Department of Chemistry, Biology, and Biotechnology, University of Perugia, Via Elce di sotto 8, 06123 Perugia (Italy)

    2015-10-28

    A combined analysis of both new (energy spectra of emitted electrons) and previously published (ionization cross sections) experimental data, measured under the same conditions and concerning electronically excited lighter noble gas –NH{sub 3} collisional autoionization processes, is carried out. Such an analysis, performed by exploiting a formulation of the full potential energy surface both in the real and imaginary parts, provides direct information on energetics, structure, and lifetime of the intermediate collision complex over all the configuration space. The marked anisotropy in the attraction of the real part, driving the approach of reagents, and the selective role of the imaginary component, associated to the charge transfer coupling between entrance and exit channels, suggests that reactive events occur almost exclusively in the molecular hemisphere containing the nitrogen lone pair. Crucial details on the stereo-dynamics of elementary collisional autoionization processes are then obtained, in which the open shell nature of the disclosed ionic core of metastable atom plays a crucial role. The same analysis also suggests that the strength of the attraction and the anisotropy of the interaction increases regularly along the series Ne{sup *}({sup 3}P), He{sup *}({sup 3}S), He{sup *}({sup 1}S)–NH{sub 3}. These findings can be ascribed to the strong rise of the metastable atom electronic polarizability (deformability) along the series. The obtained results can stimulate state of the art ab initio calculations focused on specific features of the transition state (energetics, structure, lifetime, etc.) which can be crucial for a further improvement of the adopted treatment and to better understand the nature of the leading interaction components which are the same responsible for the formation of the intermolecular halogen and hydrogen bond.

  18. Physics with antiprotons at LEAR

    International Nuclear Information System (INIS)

    The low energy antiproton ring LEAR started to work at CERN in 1983. It provides clean anti p beams of much higher intensity and much better quality than available so far in the range from 0.1 to 2 GeV/c momentum. 16 of the 17 accepted experiments are installed and 14 of them took first data in 1983. After approx.= 240 hours of LEAR operation very first results are available. One can expect that exciting physics results be produced in many different domains provided LEAR gets enough anti p in the future. (orig.)

  19. Characterization of the Plasma Edge for Technique of Atomic Helium Beam in the CIEMAT Fusion Device; Caracterizacion del Borde del Plasma del Dispositivo de Fusion TJ-II del CIEMAT mediante el Diagnostico del Haz Supersonico de Helio

    Energy Technology Data Exchange (ETDEWEB)

    Hidalgo, A.

    2003-07-01

    In this report, the measurement of Electron Temperature and Density in the Boundary Plasma of TJ-II with a Supersonic Helium Beam Diagnostic and work devoted to the upgrading of this technique are described. Also, simulations of Laser Induced Fluorescence (LIF) studies of level populations of electronically excited He atoms are shown. This last technique is now being installed in the CIEMAT fusion device. (Author ) 36 refs.

  20. Characterization of helium/argon working gas systems in a radiofrequency glow discharge atomic emission source. Part I: Optical emission, sputtering and electrical characteristics

    Science.gov (United States)

    Christopher, Steven J.; Hartenstein, Matthew L.; Marcus, R. Kenneth; Belkin, Mikhail; Caruso, Joseph A.

    1998-08-01

    Studies are performed to determine the influence of discharge gas composition (helium/argon working gas mixtures) on the analyte emission signal intensities, sputtering rates, and DC-bias characteristics of an analytical radiofrequency glow discharge atomic emission spectroscopy (RF-GD-AES) source. As the partial pressure of He is increased from 0 to 15 torr, increased emission intensity is observed for a range of bulk and trace elements in NIST 1250 SRM (low alloy steel), regardless of the base pressure of Ar in the source (5 and 9 torr). In contrast to increases in analyte emission intensity of up to 300%, counterindicative decreases in the sputtering rates on the order of about 30-50% are observed. The magnitude of these effects depends on both the partial pressure of helium introduced to the source and the total pressure of the He and Ar gases. Use of relative emission yield (REY) to normalize changes in emission intensity to sputtering rates indicates that excitation efficiencies increase under these conditions. Increases in average electron energy and temperature appear to control this response. Decreases in both analyte emission intensities and sputter rates occur with increasing He partial pressure when the total pressure in the cell remains fixed (11 torr in these studies). Emission yields for the fixed pressure, mixed gas plasmas decrease as the partial pressure of He (He/Ar ratio) in the RF-GD source increases. In this case, decreases in electron number densities appear to dictate the lower REYs. Measurement of DC-bias values at the sample surface provide understanding with respect to the observed changes in sputtering rates as well as suggest the origins of changes in plasma electron energetics. Use of a diamond stylus profilometer provides both the quantitative sputter rate information as well as qualitative insights into the use of mixed gas plasmas for enhanced depth profiling capabilities. The analyte emission characteristics of these mixed gas

  1. Assessment of General Atomics accelerator transmutation of waste concept based on gas-turbine-modular helium cooled reactor technology

    International Nuclear Information System (INIS)

    An assessment has been performed for an Accelerator Transmutation of Waste (ATW) concept based on the use of the high temperature gas reactor technology. The concept has been proposed by General Atomics for the ATW system. The assessment was jointly conducted at Argonne National Laboratory (ANL) and Los Alamos national laboratory to assess and to define the potential candidates for the ATW system. This report represents the assessment work performed at ANL. The concept uses recycled light water reactor (LWR)-discharge-transuranic extracted from irradiated oxide fuel in a critical and sub-critical accelerator driven gas-cooled transmuter. In this concept, the transmuter operates at 600 MWt first in the critical mode for three cycles and then operates in a subcritical accelerator-driven mode for a single cycle. The transmuter contains both thermal and fast spectrum transmutation zones. The thermal zone is fueled with the TRU oxide material in the form of coated particles, which are mixed with graphite powder, packed into cylindrical compacts, and loaded in hexagonal graphite blocks with cylindrical channels; the fast zone is fueled with TRU-oxide material in the form of coated particles without the graphite powder and the graphite blocks that has been burned in the thermal region for three critical cycles and one additional accelerator-driven cycle. The fuel loaded into the fast zone is irradiated for four additional cycles. This fuel management scheme is intended to achieve a high Pu isotopes consumption in the thermal spectrum zone, and to consume the minor actinides in the fast-spectrum zone. Monte Carlo and deterministic codes have been used to assess the system performance and to determine the feasibility of achieving high TRU consumption levels. The studies revealed the potential for high consumption of Pu-239 (97%), total Pu (71%) and total TRU (64%) in the system. The analyses confirmed the need for burnable absorber for both suppressing the initial excess

  2. Neutral muonic helium(3)

    International Nuclear Information System (INIS)

    Neutral muonic helium, He++μ-e-, can be considered in two pieces. The (He++μ-)+-system is a hydrogenic ion halfway in size between an atom and a nucleus. It acts like a singly charged pseudo-nucleus to the electron surrounding it. The whole system appears like one hydrogen inside another. Neutral muonic helium can be formed in the ground state in which the coupling of the magnetic moments gives rise to a hyperfine structure (hfs). 3He++μ-e- has three spin one half particles interact without any restrictions by the Pauli exclusion principle. The level diagram of the ground state is shown. There is a large muonic hfs splitting corresponding to the He++μ- ion to be in one of the two spin states with total spin quantum number G = 0 and G = 1. To measure the atomic hfs superimposed on the G = 1 triplet state is the aim of this experiment. (Auth.)

  3. Antiproton fast ignition for inertial confinement fusion

    International Nuclear Information System (INIS)

    With 180 MJ/microg, antiprotons offer the highest stored energy per unit mass of any known entity. The use of antiprotons to promote fast ignition in an inertial confinement fusion (ICF) capsule and produce high target gains with only modest compression of the main fuel is investigated. Unlike standard fast ignition where the ignition energy is supplied by energetic, short pulse laser, the energy here is supplied through the ionization energy deposited when antiprotons annihilate at the center of a compressed fuel capsule. This can be considered in-situ fast ignition as it obviates the need for the external injection of the ignition energy. In the first of two candidate schemes, the antiproton package is delivered by a low-energy ion beam. In the second, autocatalytic scheme, the antiprotons are preemplaced at the center of the capsule prior to compression. In both schemes, the author estimates that ∼1012 antiprotons are required to initiate fast ignition in a typical ICF capsule and show that incorporation of a thin, heavy metal shell is desirable to enhance energy deposition within the ignitor zone. In addition to eliminating the need for a second, energetic fast laser and vulnerable final optics, this scheme would achieve central ignition without reliance on laser channeling through halo plasma or Hohlraum debris. However, in addition to the practical difficulties of storage and manipulation of antiprotons at low energy, the other large uncertainty for the practicality of such a speculative scheme is the ultimate efficiency of antiproton production in an external, optimized facility. Estimates suggest that the electrical wall plug energy per pulse required for the separate production of the antiprotons is of the same order as that required for the conventional slow compression driver

  4. Elastic and inelastic scattering of antiprotons

    International Nuclear Information System (INIS)

    During the last two years very interesting results have been collected at LEAR on both the elementary pantip and the antip nucleus interactions. A review of all the interesting experimental results already available is far beyond the scope of the present talk. Its topic will be essentially limited to report on the new experimental informations dealing with the knowledge of the fundamental properties of the antip p elementary interaction and the determination of the characteristics of the antip nucleus interaction. The results of the antip p cross sections measured at low momenta by the PS173 and PS172 experiments are discussed. The antip nucleus elastic scattering angular distributions collected by the PS184 experiment have significantly contributed to define the properties of the p nucleus optical potential and stimulated a lot of microscopic calculations. The results are reviewed. A comparison to the informations obtained from the measurements of X-rays in antiprotonic atoms done by the PS176 and PS186 experiments is given. The interpretation of the inelastic scattering data measured for the 12C(antip, antip)12C* system at 47 and 180 MeV for various discrete states is presented: special emphasis will be given to the study of spin-flip transitions to unnatural parity states which would provide significant constant on the isovector tensor component of the NantiN interaction. Status on the experimental study of the (antip, p) reaction is discussed

  5. Observation of antiproton annihilation in heavy nuclei at 100 GeV/c

    International Nuclear Information System (INIS)

    We report on the observation of antiproton annihilation in Mg, Ag, and Au nuclei at 100 GeV/c. The experiment was performed with the Fermilab 30'' bubble chamber spectrometer and associated Downstream Particle Identifiers. By identifying events without a leading anti p or anti n we have determined that (39+-6)% of the antiprotons annihilate in a heavy nucleus. We present this fraction as a function of atomic mass number and discuss the associated charged particle multiplicity. 5 refs., 3 figs

  6. The anti-proton charge radius

    CERN Document Server

    Crivelli, P; Heiss, M W

    2016-01-01

    The upcoming operation of the Extra Low ENergy Antiprotons (ELENA) ring at CERN, the upgrade of the anti-proton decelerator (AD), and the installation in the AD hall of an intense slow positron beam with an expected flux of $10^{8}$ e$^+$/s will open the possibility for new experiments with anti-hydrogen ($\\bar{\\text{H}}$). Here we propose a scheme to measure the Lamb shift of $\\bar{\\text{H}}$. For a month of data taking, we anticipate an uncertainty of 100 ppm. This will provide a test of CPT and the first determination of the anti-proton charge radius at the level of 10%.

  7. Gold fragmentation induced by stopped antiprotons

    OpenAIRE

    Lubinski, P.; Grochulska, A.; von Egidy, T.; Gulda, K.; Hartmann, F. J.; Jastrzebski, J.; Kurcewicz, W.; Pienkowski, L.; Stolarz, A.; Trzcinska, A.

    2002-01-01

    A natural gold target was irradiated with the antiproton beam from the Low Energy Antiproton Ring at CERN. Antiprotons of 200 MeV/c momentum were stopped in a thick target, products of their annihilations on Au nuclei were detected using the off-line gamma-ray spectroscopy method. In total, yields for 114 residual nuclei were determined, providing a data set to deduce the complete mass and charge distribution of all products with A > 20 from a fitting procedure. The contribution of evaporatio...

  8. ELENA: the extra low energy anti-proton facility at CERN

    CERN Document Server

    Maury, Stephan; Bartmann, Wolfgang; Belochitskii, Pavel; Breuker, Horst; Butin, Francois; Carli, Christian; Eriksson, Tommy; Pasinelli, Sergio; Tranquille, Gerard

    2014-01-01

    At the last LEAP conference in Vancouver 2011 the authors stated that a project ”ELENA”, as an abbreviation for Extra Low ENergy Antiproton ring and as first discussed in 1982 for LEAR by H. Herr et al., was freshly proposed with a substantial new design and revised layout and that it was under consideration to be built at CERN. ELENA is an upgrade of the Anti-proton Decelerator (AD) at CERN and is devoted to special experiments with physics using low energy anti-protons. The main topics are the anti-hydrogen production and consecutive studies of the features of this anti-matter atom as well as the anti-proton nucleon interaction by testing the QED to high precision. During the last years the project underwent several steps in presentations at different committees at CERN and was finally approved such that the construction has started. ELENA will increase the number of useful anti-protons by about two orders of magnitude and will allow to serve up to four experiments simultaneously. Very first and convinc...

  9. Cryogenic design of the stochastic cooling pick-ups for the CERN antiproton collector (ACOL)

    International Nuclear Information System (INIS)

    Stochastic cooling, a technique of prime importance for obtaining antiproton beams usable at high-energy colliders, requires wide-band and low-noise signal acquisition and processing. For this purpose, the CERN Antiproton Collector (ACOL), presently under construction, is equipped with six beam pick-up stations operating at cryogenic temperatures. Each station consists of a high-vacuum vessel housing two mobile arrays of pick-up electrodes, cooled to about 100 K by radiation to a surrounding thermal shield, and two preamplifiers kept below 20 K. Refrigeration is provided by a pair of two-stage Gifford-McMahon helium cryogenerators, thermally linked to the preamplifiers and to the thermal shield. The cryogenerators also cool activated charcoal cryopanels, in order to maintain a residual pressure in the vessel below 10-8 mbar. The choice of such cryogenic options is dictated by performance (steady-state and cool-down), simplicity of operation and maintenance, and high reliability

  10. Atomic Physics 15: Proceedings of the Fifteenth International Conference on Atomic Physics.

    Science.gov (United States)

    van Linden van den Heuvell, H. B.; Walraven, J. T. M.; Reynolds, M. W.

    1997-07-01

    The Table of Contents for the full book PDF is as follows: * Preface * Generation of a "Schrödinger cat" of radiation and observation of its decoherence * Synthesis of entangled states and quantum computing * Entangled states of atomic ions for quantum metrology and computation * Entanglement and indistinguishability: Coherence experiments with photon pairs and triplets * Atom optics as a testing ground for quantum chaos * Coherent ultra-bright XUV lasers and harmonics * Hollow atoms * Interdisciplinary experiments with polarized noble gases * The creation and study of Bose-Einstein condensation in a cold alkali vapor * oscopic quantum phenomena in trapped Bose-condensed gases * Doppler-free spectroscopy of trapped atomic hydrogen * QED and the ground state of helium * Towards coherent atomic samples using laser cooling * Bose-Einstein condensation of a weakly-interacting gas * Zeeman and his contemporaries: Dutch physics around 1900 * Zeeman's great discovery * The Zeeman effect: A tool for atom manipulation * The Zeeman effect a century later: New insights into classical physics * QED effects in few-electron high-Z systems * Lamb shift experiments on high-Z one- and two-electron systems * Fundamental constants of nature * Response of atoms in photonic lattices * Hydrogen-like systems and quantum electrodynamics * New experiments with atomic lattices bound by light * Bloch oscillations of atoms in an optical potential * Quantum decoherence and inertial sensing with atom interferometers * Quantum effects in He clusters * Atoms in super-intense radiation fields * Wave packet dynamics of excited atomic electrons in intense laser fields * Nonlinear laser-electron scattering * Comparing the antiproton and proton and progress toward cold antihydrogen * Author Index

  11. Antiproton Induced Fission and Fragmentation of Nuclei

    CERN Multimedia

    2002-01-01

    The annihilation of slow antiprotons with nuclei results in a large highly localized energy deposition primarily on the nuclear surface. \\\\ \\\\ The study of antiproton induced fission and fragmentation processes is expected to yield new information on special nuclear matter states, unexplored fission modes, multifragmentation of nuclei, and intranuclear cascades.\\\\ \\\\ In order to investigate the antiproton-nucleus interaction and the processes following the antiproton annihilation at the nucleus, we propose the following experiments: \\item A)~Measurement of several fragments from fission and from multifragmentation in coincidence with particle spectra, especially neutrons and kaons. \\item B)~Precise spectra of $\\pi$, K, n, p, d and t with time-of-flight techniques. \\item C)~Installation of the Berlin 4$\\pi$ neutron detector with a 4$\\pi$ Si detector placed inside for fragments and charged particles. This yields neutron multiplicity distributions and consequently distributions of thermal excitation energies and...

  12. The biological effectiveness of antiproton irradiation

    DEFF Research Database (Denmark)

    Holzscheiter, Michael H.; Bassler, Niels; Agazaryan, Nzhde;

    2006-01-01

    Background and purpose: Antiprotons travel through tissue in a manner similar to that for protons until they reach the end of their range where they annihilate and deposit additional energy. This makes them potentially interesting for radiotherapy. The aim of this study was to conduct the first...... ever measurements of the biological effectiveness of antiprotons. Materials and methods: V79 cells were suspended in a semi-solid matrix and irradiated with 46.7 MeV antiprotons, 48 MeV protons, or 60Co c-rays. Clonogenic survival was determined as a function of depth along the particle beams. Dose and...... particle fluence response relationships were constructed from data in the plateau and Bragg peak regions of the beams and used to assess the biological effectiveness. Results: Due to uncertainties in antiproton dosimetry we defined a new term, called the biologically effective dose ratio (BEDR), which...

  13. Atoms

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2007-01-01

    Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what

  14. Helium solubility in imperfect ionic crystals

    International Nuclear Information System (INIS)

    In the context of the intended use of helium as a coolant in high temperature gas cooled reactors a study is undertaken into helium interaction with crystals at the stage preceding the process of helium clusters formation. Experimental and theoretical investigations of helium solubility in imperfect ionic crystals CaF2, SrF2, KBr are carried out along with the degassing kinetics in the temperature range of 500-1200 K. An analysis is made for possible mechanisms of the occurrence of observed oscillations in helium solubility at temperature variations. The solution heat for helium atoms in cation vacancies and the energy of impurity-vacancy cluster dissociation are calculated. The reason for a catastrophic increase of dissolved helium concentration with saturation pressure is discussed

  15. Pair Correlations in Superfluid Helium 3

    OpenAIRE

    Vollhardt, D.

    1997-01-01

    In 1996 Lee, Osheroff and Richardson received the Nobel Prize for their 1971 discovery of superfluid helium 3 -- a discovery which opened the door to the most fascinating system known in condensed matter physics. The superfluid phases of helium 3, originating from pair condensation of helium 3 atoms, turned out to be the ideal test-system for many fundamental concepts of modern physics, such as macroscopic quantum phenomena, (gauge-)symmetries and their spontaneous breakdown, topological defe...

  16. Helium behaviour in nuclear glasses

    International Nuclear Information System (INIS)

    The present thesis focuses on the study of helium behavior in R7T7 nuclear waste glass. Helium is generated by the minor actinides alpha decays incorporated in the glass matrix. Therefore, four types of materials were used in this work. These are non radioactive R7T7 glasses saturated with helium under pressure, glasses implanted with 3He+ ions, glasses doped with curium and glasses irradiated in nuclear reactor. The study of helium solubility in saturated R7T7 glass has shown that helium atoms are inserted in the glass free volume. The results yielded a solubility of about 1016 at. cm-3 atm.-1. The incorporation limit of helium in this type of glass has been determined; its value amounted to about 2*1021 at. cm-3, corresponding to 2.5 at.%. Diffusion studies have shown that the helium migration is controlled by the single population dissolved in the glass free volume. An ideal diffusion model was used to simulate the helium release data which allowed to determine diffusion coefficients obeying to the following Arrhenius law: D = D0exp(-Ea/kBT), where D0 = 2.2*10-2 and 5.4*10-3 cm2 s-1 and Ea = 0.61 eV for the helium saturated and the curium doped glass respectively. These results reflect a thermally activated diffusion mechanism which seems to be not influenced by the glass radiation damage and helium concentrations studied in the present work (up to 8*1019 at. g-1, corresponding to 0.1 at.%). Characterizations of the macroscopic, structural and microstructural properties of glasses irradiated in nuclear reactor did not reveal any impact associated with the presence of helium at high concentrations. The observed modifications i.e. a swelling of 0.7 %, a decrease in hardness by 38 %, an increase between 8 and 34 % of the fracture toughness and a stabilization of the glass structure under irradiation, were attributed to the glass nuclear damage induced by the irradiation in reactor. Characterizations by SEM and TEM of R7T7 glasses implanted with helium at high

  17. Atoms

    International Nuclear Information System (INIS)

    Completed by recent contributions on various topics (atoms and the Brownian motion, the career of Jean Perrin, the evolution of atomic physics since Jean Perrin, relationship between scientific atomism and philosophical atomism), this book is a reprint of a book published at the beginning of the twentieth century in which the author addressed the relationship between atomic theory and chemistry (molecules, atoms, the Avogadro hypothesis, molecule structures, solutes, upper limits of molecular quantities), molecular agitation (molecule velocity, molecule rotation or vibration, molecular free range), the Brownian motion and emulsions (history and general features, statistical equilibrium of emulsions), the laws of the Brownian motion (Einstein's theory, experimental control), fluctuations (the theory of Smoluchowski), light and quanta (black body, extension of quantum theory), the electricity atom, the atom genesis and destruction (transmutations, atom counting)

  18. The antiproton depth–dose curve in water

    CERN Document Server

    Bassler, N; Jäkel, O; Knudsen, H V; Kovacevic, S

    2008-01-01

    We have measured the depth–dose curve of 126 MeV antiprotons in a water phantom using ionization chambers. Since the antiproton beam provided by CERN has a pulsed structure and possibly carries a high-LET component from the antiproton annihilation, it is necessary to correct the acquired charge for ion recombination effects. The results are compared with Monte Carlo calculations and were found to be in good agreement. Based on this agreement we calculate the antiproton depth–dose curve for antiprotons and compare it with that for protons and find a doubling of the physical dose in the peak region for antiprotons.

  19. Polarized antiproton beam at U-70 accelerator of IHEP

    Science.gov (United States)

    Nurushev, S. B.; Chetvertkov, M. A.; Chetvertkova, V. A.; Garkusha, V. I.; Meschanin, A. P.; Mochalov, V. V.; Nurusheva, M. B.; Rykov, V. L.; Semenov, P. A.; Strikhanov, M. N.; Vasiliev, A. N.; Zapolsky, V. N.

    2016-02-01

    The polarized proton and antiproton beam channel is currently under development at the U-70 accelerator of IHEP, Protvino, Russia. An availability of the both, polarized protons and antiprotons provides an exciting opportunity for the comparative studies of spin effects induced by polarized protons and antiprotons in a variety of hadronic reactions. While the proton and antiproton beams are formed by essentially the same method, there is the specific in the antiproton beam shaping and properties compared to protons. In this report, we address some technical details of forming the polarized antiproton beam and describe its main properties.

  20. Antiproton-nucleus potentials from global fits to antiprotonic X-rays and radiochemical data

    Czech Academy of Sciences Publication Activity Database

    Friedman, E.; Gal, A.; Mareš, Jiří

    2005-01-01

    Roč. 761, 3/4 (2005), s. 283-295. ISSN 0375-9474 R&D Projects: GA AV ČR IAA1048305 Institutional research plan: CEZ:AV0Z10480505 Keywords : antiproton-nuclear interaction * RMF calculations * antiproton X-rays Subject RIV: BE - Theoretical Physics Impact factor: 1.950, year: 2005

  1. Atomic physics

    International Nuclear Information System (INIS)

    Research activities in atomic physics at Lawrence Berkeley Laboratory during 1976 are described. Topics covered include: experiments on stored ions; test for parity violation in neutral weak currents; energy conservation and astrophysics; atomic absorption spectroscopy, atomic and molecular detectors; theoretical studies of quantum electrodynamics and high-z ions; atomic beam magnetic resonance; radiative decay from the 23Po,2 levels of helium-like argon; quenching of the metastable 2S/sub 1/2/ state of hydrogen-like argon in an external electric field; and lifetime of the 23Po level of helium-like krypton

  2. Atomic processes in matter-antimatter interactions

    International Nuclear Information System (INIS)

    Atomic processes dominate antiproton stopping in matter at nearly all energies of interest. They significantly influence or determine the antiproton annihilation rate at all energies around or below several MeV. This article reviews what is known about these atomic processes. For stopping above about 10 eV the processes are antiproton-electron collisions, effective at medium keV through high MeV energies, and elastic collisions with atoms and adiabatic ionization of atoms, effective from medium eV through low keB energies. For annihilation above about 10 eV is the enhancement of the antiproton annihilation rate due to the antiproton-nucleus coulomb attraction, effective around and below a few tens of MeV. At about 10 eV and below, the atomic rearrangement/annihilation process determines both the stopping and annihilation rates. Although a fair amount of theoretical and some experimental work relevant to these processes exist, there are a number of energy ranges and material types for which experimental data does not exist and for which the theoretical information is not as well grounded or as accurate as desired. Additional experimental and theoretical work is required for accurate prediction of antiproton stopping and annihilation for energies and material relevant to antiproton experimentation and application

  3. Excitation and ionization of hydrogen and helium atoms by femtosecond laser pulses: theoretical approach by Coulomb-Volkov states; Excitation et ionisation des atomes d'hydrogene et d'helium par des impulsions laser femtosecondes: approche theorique par des etats de Coulomb-Volkov

    Energy Technology Data Exchange (ETDEWEB)

    Guichard, R

    2007-12-15

    We present a theoretical approach using Coulomb-Volkov states that appears useful for the study of atomic multi-photonic processes induced by intense XUV femtosecond laser pulses. It predicts hydrogen ionization spectra when it is irradiated by laser pulses in perturbations conditions. Three ways have been investigated. Extension to strong fields when {Dirac_h}{omega} > I{sub p}: it requires to include the hydrogen ground state population, introducing it in standard Coulomb-Volkov amplitude leads to saturated multi-photonic ionization. Extension to multi-photonic transitions with {Dirac_h}{omega} < I{sub p}: new quantum paths are open by the possibility to excite the lower hydrogen bound states. Multiphoton excitation of these states is investigated using a Coulomb-Volkov approach. Extension to helium: two-photon double ionization study shows the influence of electronic correlations in both ground and final state. Huge quantity of information such as angular and energetic distributions as well as total cross sections is available. (author)

  4. Multiple ionization of atoms with xuv attosecond pulses: Two-photon double ionization of helium with 50 eV photons

    Energy Technology Data Exchange (ETDEWEB)

    Bachau, H [Centre Lasers Intenses et Applications, Universite Bordeaux I-CNRS-CEA, 33405 Talence Cedex (France); Foumouo, E; Antoine, Ph; Piraux, B [Laboratoire de Physique Atomique, Moleculaire et Optique, unite PAMO, Universite Catholique de Louvain, 2 chemin du cyclotron, B-1348 Louvain-la-Neuve (Belgium); Chuluunbaatar, O [Joint Institute for Nuclear Research, Dubna, Moscow region, 141980 (Russian Federation); Popov, Y [Nuclear Physics Institute, Moscow State University, Moscow, 119991 (Russian Federation); Shakeshaft, R, E-mail: bachau@celia.u-bordeaux1.f [Physics Department, University of Southern California, Los Angeles, CA 90089-0484 (United States)

    2010-02-01

    We consider two-photon double ionization of helium by two xuv photons in the region around the sequential ionization threshold. We show that, on the attosecond timescale, the mechanism for double ionization is dominated by the absorption of one photon by each electron in the fundamental state He(1s{sup 2}). We examine the dynamics of two-photon double ionization of helium for an averaged photon energy {omega} = 50 eV, with a pulse duration of two optical cycles. The double ionization rate, energy and angular distributions are calculated by solving the time-dependent Schroedinger equation. Results are discussed on the basis of a model.

  5. Multiple ionization of atoms with xuv attosecond pulses: Two-photon double ionization of helium with 50 eV photons

    International Nuclear Information System (INIS)

    We consider two-photon double ionization of helium by two xuv photons in the region around the sequential ionization threshold. We show that, on the attosecond timescale, the mechanism for double ionization is dominated by the absorption of one photon by each electron in the fundamental state He(1s2). We examine the dynamics of two-photon double ionization of helium for an averaged photon energy ω = 50 eV, with a pulse duration of two optical cycles. The double ionization rate, energy and angular distributions are calculated by solving the time-dependent Schroedinger equation. Results are discussed on the basis of a model.

  6. Antiprotons four times more effective than protons for cell irradiation

    CERN Multimedia

    2006-01-01

    "A pioneering experiment at CERN with potential future application in cancer therapy has produced its first results. Started in 2003, ACE (Antiproton Cell Experiment) is the first investigation of the biological effects of antiprotons." (1,5 page)

  7. Antiprotons four times more effective than protons for cell irradiation

    CERN Multimedia

    2007-01-01

    "A pioneering experiment at CERN with potential future application in cancer therapy has produced its first results. Started in 2003, ACE (Antiproton Cell Experiment) is the first investigation of the biological effects of antiprotons." (1,5 page)

  8. Ultralow-energy antiprotons for antihydrogen spectroscopy and antimatter gravity

    International Nuclear Information System (INIS)

    Approximately one million antiprotons have been captured in a large-scale Penning trap at the Low Energy Antiproton Ring (LEAR) at CERN. Up to 65% of the captured antiprotons have subsequently been electron cooled to energies below 1 eV and have been stored up to one hour. This has opened new discussions of the possible use of ultralow-energy antiprotons for gravitational physics, as well as for precision spectroscopy of antihydrogen for CPT tests

  9. Calculation of the spectral line intensity in a nuclear-excited helium plasma

    International Nuclear Information System (INIS)

    Results of theoretical investigations in the helium plasma excited by the fission fragments are considered. The creation of helium atom excited states is investigated. Experimental dta on electrical discharge in helium is taken into account too. The similarity in the process of helium atom exciting in the electrical discharge and in the nuclear type plasma is established on the base of spectral lines comparison in the one medium and another. The role of helium atom exciting by the fast electrons and de-exciting by the counters with helium atoms is analyzed

  10. Exotic helium molecules

    International Nuclear Information System (INIS)

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range 4He2(23S1-23P0) molecule, or a 4He2(23S1-23S1) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 ± 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range 4He2(23S1-23S1) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime τ = (1.4 ± 0.3) μs is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  11. Double electron excitation of helium by charged particle impact

    International Nuclear Information System (INIS)

    Complete text of publication follows. A four-body classical trajectory Monte Carlo method is applied in the study of double electron excitation of helium by charged particle impact. The calculations are based on the independent particle model. As projectiles we consider protons and antiprotons with energies between 0.25 and 5 MeV. The state selective total cross sections as a function of the impact energy are calculated and compared with experimental and theoretical data. Fig. 1. shows the double excitation cross sections of helium to the (2s2)1S (Fig. 1a), (2s2p)1P (Fig. 1b) and (2p2)1D (Fig. 1c) states as a function of the impact energy. The errors of our calculated data are smaller or comparable with the size of the symbols. Our recent cross sections are compared with the experimental data of Giese et al. and Moretto-Capelle et al. and with the previous calculations of Bodea et al. Instead of the antiproton impact, the experiments in ref. were carried out with electron impact. These cross sections are shown at the energy where the electron velocity is equal that of the antiproton velocity. In all cases the cross sections for antiprotons exceeds the cross section for protons. The largest difference is obtained for the excitation of the (2s2)1S state (Fig. 1a). According to our expectation, with increasing projectile energies the cross sections for proton and antiproton impact approaching each other. This tendency is valid for the previous calculations of Bodea et al. except for the (2p2)1D (Fig. 1c). The calculated cross sections generally agree with the experimental values. (author)

  12. The Antiproton Depth-Dose Curve in Water

    DEFF Research Database (Denmark)

    Bassler, Niels; Holzscheiter, Michael; Jäkel, Oliver; Knudsen, Helge; Kovacevic, Sandra; AD-4/ACE Collaboration

    2008-01-01

    We have measured the depth-dose curve of 126 MeV antiprotons in a water phantom using ionization chambers. Since the antiproton beam provided by CERN has a pulsed structure and possibly carries a high-LET component from the antiproton annihilation, it is necessary to correct the acquired charge for...

  13. Antiproton beam polarizer using a dense polarized target

    Energy Technology Data Exchange (ETDEWEB)

    Wojtsekhowski, Bogdan

    2011-05-01

    We describe considerations regarding the spin filtering method for the antiproton beam. The proposed investigation of the double polarization cross section for antiproton to nucleon interaction is outlined. It will use a single path of the antiproton beam through a dense polarized target, e.g. 3He or CH2, followed by a polarimeter.

  14. The HEAT Cosmic Ray Antiproton Experiment

    Science.gov (United States)

    Nutter, Scott

    1998-10-01

    The HEAT (High Energy Antimatter Telescope) collaboration is constructing a balloon-borne instrument to measure the relative abundance of antiprotons and protons in the cosmic rays to kinetic energies of 30 GeV. The instrument uses a multiple energy loss technique to measure the Lorentz factor of through-going cosmic rays, a magnet spectrometer to measure momentum, and several scintillation counters to determine particle charge and direction (up or down in the atmosphere). The antiproton to proton abundance ratio as a function of energy is a probe of the propagation environment of protons through the galaxy. Existing measurements indicate a higher than expected value at both high and low energies. A confirming measurement could indicate peculiar antiproton sources, such as WIMPs or supersymmetric darkmatter candidates.

  15. Cosmic ray antiprotons from nearby cosmic accelerators

    Science.gov (United States)

    Joshi, Jagdish C.; Gupta, Nayantara

    2015-05-01

    The antiproton flux measured by PAMELA experiment might have originated from Galactic sources of cosmic rays. These antiprotons are expected to be produced in the interactions of cosmic ray protons and nuclei with cold protons. Gamma rays are also produced in similar interactions inside some of the cosmic accelerators. We consider a few nearby supernova remnants observed by Fermi LAT. Many of them are associated with molecular clouds. Gamma rays have been detected from these sources which most likely originate in decay of neutral pions produced in hadronic interactions. The observed gamma ray fluxes from these SNRs are used to find out their contributions to the observed diffuse cosmic ray antiproton flux near the earth.

  16. Low energy antiproton possibilities at the AGS

    International Nuclear Information System (INIS)

    The technical feasibility of creating a pure antiproton beam at the AGS has been studied. The scheme involves an antiproton target station and transport back to the Booster synchrotron, which acts as both a purifier and accelerator/decelerator. This proposal would be very attractive to the user community since this operation could run parasitically (transparently) to the AGS operating modes. The energy range of antiprotons can be as low as 2 MeV to as high as 5 GeV. The intensity of the beam is estimated to be 7 x 107/sec above 2.5 GeV/c and 4 x 104/sec at 200 MeV/c

  17. On charged impurity structures in liquid helium

    International Nuclear Information System (INIS)

    The thermoluminescence spectra of impurity-helium condensates (IHC) submerged in superfluid helium have been observed for the first time. Thermoluminescence of impurity-helium condensates submerged in superfluid helium is explained by neutralization reactions occurring in impurity nanoclusters. Optical spectra of excited products of neutralization reactions between nitrogen cations and thermoactivated electrons were rather different from the spectra observed at higher temperatures, when the luminescence due to nitrogen atom recombination dominates. New results on current detection during the IHC destruction are presented. Two different mechanisms of nanocluster charging are proposed to describe the phenomena observed during preparation and warm-up of IHC samples in bulk superfluid helium, and destruction of IHC samples out of liquid helium.

  18. Observation of visible emission from the molecular helium ion in the afterglow of a dense helium Z-pinch plasma

    International Nuclear Information System (INIS)

    The authors present the results of axial and radial time resolved visible emission spectroscopy from the afterglow of a dense helium Z-pinch. These results show that the visible emissions in the pinch afterglow are dominated by line emissions from molecular helium and He II. Axial spectroscopy measurements show the occurrence of several absorption bands which cannot be identified as molecular or atomic helium nor impurities from the discharge chamber materials. The authors believe that these absorption bands are attributable to the molecular helium ion which is present in the discharge. The molecular ion has been observed by others in low pressure and temperature helium discharges directly by means of mass spectrometry and indirectly by the presence of helium atoms in the 2/sup 3/S state, (the He 2/sup 3/S state is believed to result from molecular helium ion recombination). However, the molecular helium ion has not previously been observed spectroscopically

  19. Thermal evolution of helium in magnetron sputtered titanium films

    International Nuclear Information System (INIS)

    Helium-containing titanium films synthesized by magnetron sputtering method were investigated using thermal desorption spectrometry (TDS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Helium evolution behaviors under thermal treatment from room temperature to 1500 °C were characterized. Four peaks appeared in TDS at around 100, 420, 700, and 1250 °C were identified and attributed to helium desorption from the specimen surface, substitutional helium (helium atom in a vacancy), small HemVn clusters with different helium-to-vacancy ratios, and helium bubbles or voids, respectively. The helium evolution under thermal treatment composed of two coexisting and competing processes, where the faster process dominated in relevant temperature range, i.e. helium diffusion and release at low temperatures, and bubble or void formation at high temperatures. Three characteristic temperatures in TDS were identified in description of the phenomenon

  20. K-shell ionization by antiprotons

    International Nuclear Information System (INIS)

    We present first calculations for the impact parameter dependence of K-shell ionization rates in anti pCu and in anti pAg collisions at various projectile energies. We show that the effect of the attractive Coulomb potential on the Rutherford trajectory and the anti-binding effect caused by the negative charge of the antiproton result in a considerable increase of the ionization probability. Total ionization cross-sections for proton and antiproton projectiles are compared with each other and with experimental ionization cross-sections for protons. (orig.)

  1. Calculated LET-Spectrum of Antiprotons

    DEFF Research Database (Denmark)

    Bassler, Niels

    Introduction Antiprotons as a new beam modality in radiotherapy are being investigated by the AD-4/ACE collaboration since 2002. A beam of antiprotons hitting a water phantom exhibit a similar depth-dose curve as that known from protons, except that the Bragg-peak is significantly pronounced due...... primary particles, the increased stopping power of the secondary causes an increase in the dose averaged LET. The maximum LET is recorded in the peak as 19 keV/µm. Discussion The dose-average LET in the plateau region may result in a RBE different from unity in the plateau region. RBE measurements of...

  2. Thermal stability of helium-vacancy clusters in iron

    International Nuclear Information System (INIS)

    Molecular dynamics calculations were performed to evaluate the thermal stability of helium-vacancy clusters (HenVm) in Fe using the Ackland Finnis-Sinclair potential, the Wilson-Johnson potential and the Ziegler-Biersack-Littmark-Beck potential for describing the interactions of Fe-Fe, Fe-He and He-He, respectively. Both the calculated numbers of helium atoms, n, and vacancies, m, in clusters ranged from 0 to 20. The binding energies of an interstitial helium atom, an isolated vacancy and a self-interstitial iron atom to a helium-vacancy cluster were obtained from the calculated formation energies of clusters. All the binding energies do not depend much on cluster size, but they primarily depend on the helium-to-vacancy ratio (n/m) of clusters. The binding energy of a vacancy to a helium-vacancy cluster increases with the ratio, showing that helium increases cluster lifetime by dramatically reducing thermal vacancy emission. On the other hand, both the binding energies of a helium atom and an iron atom to a helium-vacancy cluster decrease with increasing the ratio, indicating that thermal emission of self-interstitial atoms (SIAs) (i.e. Frenkel-pair production), as well as thermal helium emission, may take place from the cluster of higher helium-to-vacancy ratios. The thermal stability of clusters is decided by the competitive processes among thermal emission of vacancies, SIAs and helium, depending on the helium-to-vacancy ratio of clusters. The calculated thermal stability of clusters is consistent with the experimental observations of thermal helium desorption from α-Fe during post-He-implantation annealing

  3. Antiproton-proton resonant like channels in J/Psi decays into photon, proton and antiproton

    CERN Document Server

    Loiseau, B

    2005-01-01

    The BES collaboration has recently observed a strong enhancement close to the proton-antiproton threshold in the J/Psi decays into photon, proton and antiproton. Such a structure can be explained by a traditional nucleon-antinucleon model. The near threshold 1S0 bound state and/or the well-established 3P0 resonant state found in this nucleon-antinucleon interaction can adequately describe the BES data.

  4. Nucleon density in the nuclear periphery determined with antiprotonic x-rays: cadmium and tin isotopes

    OpenAIRE

    Schmidt, R.; Trzcinska, A.; Czosnyka, T.; von Egidy, T.; Gulda, K.; Hartmann, F. J.; Jastrzebski, J.; Ketzer, B.; Kisielinski, M.; Klos, B.; Kurcewicz, W.; Lubinski, P.; Napiorkowski, P.; Pienkowski, L.; Smolanczuk, R.

    2002-01-01

    The x-ray cascade from antiprotonic atoms was studied for 106Cd, 116Cd, 112Sn, 116Sn, 120Sn, and 124Sn. Widths and shifts of the levels due to strong interaction were deduced. Isotopic effects in the Cd and Sn isotopes are clearly seen. The results are used to investigate the nucleon density in the nuclear periphery. The deduced neutron distributions are compared with the results of the previously introduced radiochemical method and with HFB calculations.

  5. Molecular dynamics simulations of cumulative helium bombardments on tungsten surfaces

    International Nuclear Information System (INIS)

    Molecular dynamics simulations were performed to study the cumulative bombardments of low-energy (60–200 eV) helium atoms on tungsten surfaces. The behaviour of helium and the response of tungsten surface were investigated. The helium incident energy and tungsten temperature play important roles on the formation and growth of helium clusters. The temperature can promote the coalescence of helium clusters and increase the size of the helium clusters. The rupture of the helium clusters has also been observed. During the formation of helium clusters, the interstitial tungsten atoms are produced and evolve into bundles of <1 1 1> crowdions, which would be constrained around the helium clusters for a long time. However, they will finally move onto the top surface along the <1 1 1> direction, which results in stacking the tungsten atoms on the surface. The complex combination effects of the helium clusters and the interstitial atoms result in the growth of the surfaces. Besides, several tungsten atoms were ejected from tungsten surfaces

  6. Ionization in antiproton-hydrogen collisions

    International Nuclear Information System (INIS)

    Employing the semiclassical approximation we calculate within the coupled-state formalism the ionization probability in antiproton-hydrogen (anti p+H) collisions. In particular we investigate the adiabatic ionization at the distance of closest approach in almost central collisions. Striking differences in the electron excitation probability compared with proton-hydrogen (p+H) collisions are predicted. (orig.)

  7. First observation of two hyperfine transitions in antiprotonic 3He

    International Nuclear Information System (INIS)

    We report on the first experimental results for microwave spectroscopy of the hyperfine structure of p-bar3He+. Due to the helium nuclear spin, p-bar3He+ has a more complex hyperfine structure than p-bar4He+, which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the three-body quantum electrodynamics (QED) theory. Two out of four super-super-hyperfine (SSHF) transition lines of the (n,L)=(36,34) state were observed. The measured frequencies of the individual transitions are 11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current theoretical values, but still within their estimated errors. Although the experimental uncertainty for the difference of these frequencies is still very large as compared to that of theory, its measured value agrees with theoretical calculations. This difference is crucial to be determined because it is proportional to the magnetic moment of the antiproton.

  8. The Angular Distribution Of Electron-positron Pairs From Exclusive Charmonium Decays In Antiproton-proton Annihilations

    CERN Document Server

    McTaggart, R J

    1998-01-01

    The angular distributions of the charmonium resonances J/ Y (3097) and Y (3686) in their exclusive decay to an electron-positron pair are studied. Experiment 835 at the Fermi National Accelerator Laboratory produced charmonium resonances by annihilating protons with antiprotons in the Fixed Target Mode of the Antiproton Accumulator: A stochastically cooled antiproton beam collides with a hydrogen gas jet, which forms clusters under the right pressure and low temperature. The charmonium decay products are detected out of a large hadronic background with the help of a segmented lead glass sampling calorimeter, which is sensitive to the high mass electron-positron charmonium decay, and a set of Cerenkov threshold detectors that provide good electron/pion separation. Several factors influence the angular distribution parameter l taken from the angular distribution, including the energy scale of the resonance, the coupling strength of the charmonium atom, and how quarks and gluons interact in the dissolution...

  9. The spatio-temporal distribution of He (23S1) metastable atoms in a MHz-driven helium plasma jet is influenced by the oxygen/nitrogen ratio of the surrounding atmosphere

    Science.gov (United States)

    Winter, J.; Santos Sousa, J.; Sadeghi, N.; Schmidt-Bleker, A.; Reuter, S.; Puech, V.

    2015-04-01

    The density of helium He (23S1) metastable atoms is measured in a 1.6 mm diameter MHz-driven atmospheric pressure helium plasma jet by laser absorption spectroscopy with spatial and temporal resolution. The surrounding atmosphere of the jet is varied from pure oxygen to pure nitrogen with a gas shielding device. The highest metastable density of 1.3 × 1013 cm-3 is obtained in the center of the jet close to the nozzle exit at normal atmospheric air conditions. Within 0.3 mm in the radial direction and 2 mm in the axial direction, the He metastable density drops below the detection limit. The obtained He metastable lifetime is almost independent of the shielding gas composition. By analyzing the diffusion of shielding gas species into the effluent it is concluded that their density is too low to explain the observed He metastable lifetime. Instead, impurities from the feed gas, especially water molecules, are more likely to be responsible. However, a drastic change in metastable He density is observed when decreasing the amount of oxygen in the shielding gas. The lower the oxygen amount, the lower the metastable He density. For pure nitrogen, no He metastables are detected at all. By exchanging nitrogen with argon, a similar behavior is observed. Thus, it is concluded that it is the absence of ambient oxygen rather than the elevated presence of nitrogen, which is responsible for the observed decrease in the He (23S1) density.

  10. Conceptual Design of an Antiproton Generation and Storage Facility

    International Nuclear Information System (INIS)

    The Antiproton Generation and Storage Facility (AGSF) creates copious quantities of antiprotons, for bottling and transportation to remote cancer therapy centers. The first step in the generation and storage process is to accelerate an intense proton beam down the Main Linac for injection into the Main Ring, which is a Rapid Cycling Synchrotron that accelerates the protons to high energy. The beam is then extracted from the ring into a transfer line and into a Proton Target. Immediately downstream of the target is an Antiproton Collector that captures some of the antiprotons and focuses them into a beam that is transported sequentially into two antiproton rings. The Precooler ring rapidly manipulates antiproton bunches from short and broad (in momentum) to long and thin. It then performs some preliminary beam cooling, in the fraction of a second before the next proton bunch is extracted from the Main Ring. Pre-cooled antiprotons are passed on to the Accumulator ring before the next antiprotons arrive from the target. The Accumulator ring cools the antiprotons, compressing them into a dense state that is convenient for mass storage over many hours. Occasionally the Accumulator ring decelerates a large number of antiprotons, injecting them into a Deceleration Linac that passes them into a waiting Penning trap

  11. Conceptual Design of an Antiproton Generation and Storage Facility

    Energy Technology Data Exchange (ETDEWEB)

    Peggs, Stephen

    2006-10-24

    The Antiproton Generation and Storage Facility (AGSF) creates copious quantities of antiprotons, for bottling and transportation to remote cancer therapy centers. The first step in the generation and storage process is to accelerate an intense proton beam down the Main Linac for injection into the Main Ring, which is a Rapid Cycling Synchrotron that accelerates the protons to high energy. The beam is then extracted from the ring into a transfer line and into a Proton Target. Immediately downstream of the target is an Antiproton Collector that captures some of the antiprotons and focuses them into a beam that is transported sequentially into two antiproton rings. The Precooler ring rapidly manipulates antiproton bunches from short and broad (in momentum) to long and thin. It then performs some preliminary beam cooling, in the fraction of a second before the next proton bunch is extracted from the Main Ring. Pre-cooled antiprotons are passed on to the Accumulator ring before the next antiprotons arrive from the target. The Accumulator ring cools the antiprotons, compressing them into a dense state that is convenient for mass storage over many hours. Occasionally the Accumulator ring decelerates a large number of antiprotons, injecting them into a Deceleration Linac that passes them into a waiting Penning trap.

  12. Preliminary measurements of doubly differential cross sections for ejection of electrons from atomic and molecular hydrogen by 70-keV helium ions

    International Nuclear Information System (INIS)

    A mixture of atomic and molecular hydrogen, generated by a Slevin hydrogen atom source, was used as the target for 70-keV He+ ions. Procedures were devised to extract the ratio of the cross sections for hydrogen atoms to hydrogen molecules. The cross sections for hydrogen molecules were then measured separately and the cross sections for hydrogen atoms obtained. The cross sections for ejection of electrons, differential in the angle and energy of ejection, were measured over the 15 degrees-160 degrees range of angles and at electron energies from 1.5 to 130 eV

  13. Preliminary measurements of doubly differential cross sections for ejection of electrons from atomic and molecular hydrogen by 70-keV helium ions

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Y.Y.; Gealy, M.W.; Kerby, G.W.; Rudd, M.E. [Univ. of Nebraska, Lincoln, NB (United States)

    1993-05-01

    A mixture of atomic and molecular hydrogen, generated by a Slevin hydrogen atom source, was used as the target for 70-keV He{sup +} ions. Procedures were devised to extract the ratio of the cross sections for hydrogen atoms to hydrogen molecules. The cross sections for hydrogen molecules were then measured separately and the cross sections for hydrogen atoms obtained. The cross sections for ejection of electrons, differential in the angle and energy of ejection, were measured over the 15{degrees}-160{degrees} range of angles and at electron energies from 1.5 to 130 eV.

  14. Behavior of helium bubble in helium-doped stainless steel weldment for nuclear power plant

    International Nuclear Information System (INIS)

    The behavior of helium bubble in helium-doped austenitic stainless steel weldment was investigated using scanning electron microscopy, transmission electron microscopy and numerical calculation technique. The stainless steel was helium ion-implanted and welded by YAG laser apparatus. Helium ion implanting to the sample was carried out using 8 MeV implantation apparatus. The sample was doped 1.0x1019 atoms/m2 at 5 MeV and then doped 2.45x1019 atoms/m2 at 6 MeV. The region where helium bubbles formed in the heat-affected zone increased with increasing laser power. For low laser power, the helium concentration was above 10 appm in the weld metal and many large helium bubbles larger than 3 μm in diameter were observed at the bond region. The volume of weld metal increased and the size of helium bubble decreased with increasing laser power respectively. Number of fine helium bubbles below 0.1 μm in diameter were observed along the dendrite cell boundary in the weld metal. The increases of laser power and travel speed led to the initiation of cracking at the dendrite cell boundary in the weld metal, even at 2.9 appmHe. (author)

  15. On the energy of electric field in hydrogen atom

    OpenAIRE

    Kornyushin, Yuri

    2009-01-01

    It is shown that hydrogen atom is a unique object in physics having negative energy of electric field, which is present in the atom. This refers also to some hydrogen-type atoms: hydrogen anti-atom, atom composed of proton and antiproton, and positronium.

  16. Cross section measurements of the processes occurring in the fragmentation of Hn+ (3 ≤ n ≤ 35) hydrogen clusters induced by high speed (60 keV/u) collisions on helium atoms

    International Nuclear Information System (INIS)

    Different processes involved in the fragmentation of ionised hydrogen clusters H3 + (H2)(n-3)/2 (n = 5-35) have been studied in the same experiment: the fragmentation of the cluster is induced by the collision with an helium atom at high velocity (≅ c/100). The collision is realised in reversed kinematic - clusters are accelerated - which allows the detection of neutral and charged fragments. The different channels of fragmentation are identified by using coincidence techniques. For all the cluster sizes studied the capture cross sections of one electron of the target by the cluster is equal to the capture cross section of the H3+ ion. In the same way, the dissociation cross section of the H3+ core of the cluster does not depend on cluster size. These fragmentation processes are due to the interaction of H3+ core of the cluster and the helium atom without ionization of another component of the cluster. On the contrary, the cross sections of loss of one, two and three molecules by the cluster and the dissociation cross section of the cluster in all its molecular components depends strongly on the cluster size. This dependence is different from the one measured for the metastable decay of the cluster. Thus, the process of loss of molecules induced by a collision should correspond to a different dissociation mechanism. In regard of the singularities observed for the size dependence, the H9+, H15+, H19+ and H29+ clusters could be the 'core' of the biggest clusters. These observation are in agreement with the size effects of smaller magnitude observed for the dissociation cross section (all the processes). The values of the cross section for the process of at least one ionization of the cluster indicate that about 80% of the fragmentation events result from this process. (author)

  17. The discovery of geomagnetically trapped cosmic ray antiprotons

    CERN Document Server

    Adriani, O; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Borisov, S; Bottai, S; Bruno, A; Cafagna, F; Campana, D; Carbone, R; Carlson, P; Casolino, M; Castellini, G; Consiglio, L; De Pascale, M P; De Santis, C; De Simone, N; Di Felice, V; Galper, A M; Gillard, W; Grishantseva, L; Jerse, G; Karelin, A V; Kheymits, M D; Koldashov, S V; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Mayorov, A G; Menn, W; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Nikonov, N; Osteria, G; Palma, F; Papini, P; Pearce, M; Picozza, P; Pizzolotto, C; Ricci, M; Ricciarini, S B; Rossetto, L; Sarkar, R; Simon, M; Sparvoli, R; Spillantini, P; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G; Voronov, S A; Yurkin, Y T; Wu, J; Zampa, G; Zampa, N; Zverev, V G; 10.1088/2041-8205/736/1/L1

    2011-01-01

    The existence of a significant flux of antiprotons confined to Earth's magnetosphere has been considered in several theoretical works. These antiparticles are produced in nuclear interactions of energetic cosmic rays with the terrestrial atmosphere and accumulate in the geomagnetic field at altitudes of several hundred kilometers. A contribution from the decay of albedo antineutrons has been hypothesized in analogy to proton production by neutron decay, which constitutes the main source of trapped protons at energies above some tens of MeV. This Letter reports the discovery of an antiproton radiation belt around the Earth. The trapped antiproton energy spectrum in the South Atlantic Anomaly (SAA) region has been measured by the PAMELA experiment for the kinetic energy range 60--750 MeV. A measurement of the atmospheric sub-cutoff antiproton spectrum outside the radiation belts is also reported. PAMELA data show that the magnetospheric antiproton flux in the SAA exceeds the cosmic-ray antiproton flux by three ...

  18. X-ray transitions from antiprotonic noble gases

    International Nuclear Information System (INIS)

    The onset of antiprotonic X-ray transitions at high principal quantum numbers and the occurrence of electronic X-ray in antiprotonic argon krypton, and xenon is analysed with Multiconfiguration Dirac-Fock calculations. The shell by shell ionisation by Auger electron emission, characterised by appearance and disappearance of X-ray lines, is followed through the antiprotonic cascade by considering transition and binding energies of both the antiproton and remaining electrons. A number of additional lines in the X-ray spectra have been tentatively assigned to electronic transitions caused by electronic de-excitation after Auger emission during the antiprotonic cascade. A few lines remain unexplained so far or are not unambiguously assigned. The complexity of the electronic states cannot be resolved with semiconductor detectors. Hopefully, in future high resolution devices like crystal spectrometers and Auger electron spectroscopy at antiproton at GSI will resolve this complexity

  19. CERN accelerator school: Antiprotons for colliding beam facilities

    International Nuclear Information System (INIS)

    This is a specialized course which addresses a wide spectrum of theoretical and technological problems confronting the designer of an antiproton facility for high-energy-physics research. A broad and profound basis is provided by the lecturers' substantial experience gained over many years with CERN's unique equipment. Topics include beam optics, special lattices for antiproton accumulation and storage rings, antiproton production, stochastic cooling, acceleration and storage, r.f. noise, r.f. beam manipulations, beam-beam interaction, beam stability due to ion accumulation, and diagnostics. The SPS (Super Proton Synchrotron) panti p collider, LEAR (the Low Energy Antiproton Ring at CERN), antiprotons in the ISR (Intersecting Storage Rings), the new antiproton collector (ACOL) and gas jet targets are also discussed. A table is included listing the parameters of all CERN's accelerators and storage rings. See hints under the relevant topics. (orig./HSI)

  20. The cosmic ray antiproton background for AMS-02

    International Nuclear Information System (INIS)

    The AMS-02 experiment is measuring the cosmic ray antiproton flux with high precision. The interpretation of the upcoming data requires a thorough understanding of the secondary antiproton background. In this work, we employ newly available data of the NA49 experiment at CERN, in order to recalculate the antiproton source term arising from cosmic ray spallations on the interstellar matter. We systematically account for the production of antiprotons via hyperon decay and discuss the possible impact of isospin effects on antineutron production. A detailed comparison of our calculation with the existing literature as well as with Monte Carlo based evaluations of the antiproton source term is provided. Our most important result is an updated prediction for the secondary antiproton flux which includes a realistic assessment of the particle physics uncertainties at all energies

  1. Beam position pickup for antiprotons to the ISR

    CERN Multimedia

    CERN PhotoLab

    1981-01-01

    The Antiproton Project, launched for proton-antiproton collisions in the SPS (SPS collider), had a side-line for p-pbar collisions in the ISR. A new transfer line, TT6, was constructed to transport antiprotons from the 26 GeV PS to the injection line TT1 of ISR ring 2. Antiprotons were a scarce commodity. For setting up the lines, beam diagnostic devices in the antiproton path had to work reliably and precisely with just a few low-intensity pilot pules: single bunches of about 2x10**9 antiprotons every few hours. Electrostatic pickup electrodes were used to measure beam position. They could be mounted for measurement in the horizontal plane, as in this picture, or at 90 deg, for the vertical plane.

  2. Collisions of antiprotons with hydrogen molecular ions

    DEFF Research Database (Denmark)

    Lühr, Armin Christian; Saenz, Alejandro

    2009-01-01

    method are applied in order to describe the target molecule and the collision process. It is shown that three perpendicular orientations of the molecular axis with respect to the trajectory are sufficient to accurately reproduce the ionization cross section calculated by Sakimoto [Phys. Rev. A 71, 062704......Time-dependent close-coupling calculations of the ionization and excitation cross section for antiproton collisions with molecular hydrogen ions are performed in an impact energy range from 0.5 keV to 10 MeV. The Born-Oppenheimer and Franck-Condon approximations as well as the impact parameter...... (2005)] reducing the numerical effort drastically. The independent-event model is employed to approximate the cross section for double ionization and H+ production in antiproton collisions with H2....

  3. Confined helium on Lagrange meshes

    CERN Document Server

    Baye, Daniel

    2015-01-01

    The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than $10^{-10}$. For larger radii up to 10, they progressively decrease to $10^{-3}$, still improving the best literature results.

  4. A new approach to experiments with non-relativistic antiprotons

    International Nuclear Information System (INIS)

    Is low-energy antiproton physics phasing out with the present round of experiments or are there good reasons to continue at an improved slow antiproton facility which could be located at a high intensity hadron accelerator? We point out, that there are four frontiers where substantial advances could be made. In particular, we discuss the low-energy frontier and emphasize that experiments with no-relativistic antiprotons would increase drastically the sensitivity and would reveal new effects. (orig.)

  5. Antiproton production in relativistic Si-nucleus collisions

    International Nuclear Information System (INIS)

    We have measured antiproton production cross sections as functions of centrality in collisions of 14.6 GeV/c per nucleon 28Si ions with targets of Al, Cu, and Pb. For all targets, the antiproton yields increase linearly with the number of projectile nucleons that have interacted, and show little target dependence. We discuss the implications of this result on the production and absorption of antiprotons within the nuclear medium

  6. An antiproton catalyst for inertial confinement fusion propulsion

    Science.gov (United States)

    Lewis, Raymond A.; Newton, Richard; Smith, Gerald A.; Toothacker, William S.; Kanzleiter, Randall J.

    1990-01-01

    This paper discusses the concept of an inertial confinement fusion propulsion system involving an antiproton catalyst (for antiproton-induced fission). It is argued that, when the two processes, fusion and antimatter annihilation, are combined into one system, a viable candidate propulsion system for planetary exploration emerges. It is shown that as much as 7.6 GW of power, well within the requrements for interplanetary travel, can be achieved using existing driver technologies and available quantities of antiprotons.

  7. Kaons and antiproton-nucleus scattering

    CERN Document Server

    Haque, S; Rahman, S N

    2003-01-01

    The elastic scattering of Kaons and antiprotons from several nuclei is studied in the framework of the generalized diffraction model due to Frahn and Venter. The systematics of reaction cross section and the standard nuclear radius, as given by the model, are discussed. The parameters obtained from the elastic scattering analyses are used, without any adjustment, to reproduce some inelastic scattering angular distributions and the corresponding deformation parameters are determined.

  8. Magnetic horn of the Antiproton Accumulator (AA)

    CERN Multimedia

    Photographic Service

    1988-01-01

    In the 1960s, the invention of this "current sheet lens" has helped to greatly improve the flux of neutrino beams. It was used again at the AA, collecting antiprotons from the production target at angles too large to fit into the acceptance of the AA. It was machined from aluminium to a thickness of 1.4 mm and pulsed at 400 kA for 15 microseconds (half-sine).

  9. Shielding calculations for the antiproton target area

    International Nuclear Information System (INIS)

    Shielding calculations performed in conjunction with the design of the Fermilab antiproton target hall are summarized. The following radiological considerations were examined: soil activation, residual activity of components, and beam-on radiation. In addition, at the request of the designers, the energy deposition in the proposed graphite beam dump was examined for several targeting conditions in order to qualitatively determine its ability to survive

  10. Measurements of Cosmic Ray Antiprotons with PAMELA

    OpenAIRE

    Wu, Juan

    2010-01-01

    The PAMELA experiment is a satellite-borne apparatus designed to study charged particles, and especially antiparticles, in the cosmic radiation. The apparatus is mounted on the Resurs DK1 satellite which was launched on 15 June 2006. PAMELA has been traveling around the earth along an elliptical and semi-polar orbit for almost five years. It mainly consists of a permanent magnetic spectrometer, a time of flight system and an electromagnetic imaging calorimeter, which allows antiprotons to be ...

  11. Looking for new gravitational forces with antiprotons

    International Nuclear Information System (INIS)

    Quite general arguments based on the principle of equivalence and modern field theory show that it is possible for the gravitational acceleration of antimatter to be different than that for matter. Further, there is no experimental evidence to rule out the possibility. In fact, some evidence indicates there may be unexpected effects. Thus, the planned experiment to measure the gravitational acceleration of antiprotons is of fundamental importance. 20 refs., 3 figs

  12. Kaons and antiproton-nucleus scattering

    International Nuclear Information System (INIS)

    The elastic scattering of Kaons and antiprotons from several nuclei is studied in the framework of the generalized diffraction model due to Frahn and Venter. The systematics of reaction cross section and the standard nuclear radius, as given by the model, are discussed. The parameters obtained from the elastic scattering analyses are used, without any adjustment, to reproduce some inelastic scattering angular distributions and the corresponding deformation parameters are determined. (author)

  13. Double excitation of He and H- by fast proton and anti-proton impact

    International Nuclear Information System (INIS)

    Theoretical investigation has been made on double excitation processes of He and H- by fast proton and anti-proton impact in the MeV/u-energy region. The cross sections are calculated by use of both the close-coupling and the perturbation expansion methods, and the wave functions of target atoms are generated based on the hyperspherical coordinate method. The excitation to the 2p21De state of H- by anti-proton impact is dominant by about three times in comparison with that by proton impact at the incident energy of 0.1 MeV/u. The spectral shape of an ejected electron from the 2s2p 1po state of H- at the incident energy of 1.5 MeV/u is consistent with the line profile of the H- photodetachment observed by Bryant et al

  14. Anti- and Hypermatter Research at the Facility for Antiproton and Ion Research FAIR

    Science.gov (United States)

    Steinheimer, J.; Xu, Z.; Rau, P.; Sturm, C.; Stöcker, H.

    2013-07-01

    Within the next six years, the Facility for Antiproton and Ion Research (FAIR) is built adjacent to the existing accelerator complex of the GSI Helmholtz Center for Heavy Ion Research at Darmstadt, Germany. Thus, the current research goals and the technical possibilities are substantially expanded. With its worldwide unique accelerator and experimental facilities, FAIR will provide a wide range of unprecedented fore-front research in the fields of hadron, nuclear, atomic, plasma physics and applied sciences which are summarized in this article. As an example this article presents research efforts on strangeness at FAIR using heavy ion collisions, exotic nuclei from fragmentation and antiprotons to tackle various topics in this area. In particular, the creation of hypernuclei, metastable exotic multi-hypernuclear objects (MEMOs) and antimatter is investigated.

  15. Kilohertz laser ablation for doping helium nanodroplets

    CERN Document Server

    Mudrich, M; Müller, S; Dvorak, M; Buenermann, O; Stienkemeier, F

    2007-01-01

    A new setup for doping helium nanodroplets by means of laser ablation at kilohertz repetition rate is presented. The doping process is characterized and two distinct regimes of laser ablation are identified. The setup is shown to be efficient and stable enough to be used for spectroscopy, as demonstrated on beam-depletion spectra of lithium atoms attached to helium nanodroplets. For the first time, helium droplets are doped with high temperature refractory materials such as titanium and tantalum. Doping with the non-volatile DNA basis Guanine is found to be efficient and a number of oligomers are detected.

  16. Calculation of the resonant ionization of helium

    International Nuclear Information System (INIS)

    Autoionizing resonances in the compound system of an electron and a helium ion are observed in kinematically-complete ionization experiments for electrons on helium atoms. The differential cross section is calculated for comparison with these experiments in an equivalent-local form of the distorted-wave impulse approximation. Resonant scattering amplitudes are calculated by a six-state momentum-space coupled-channels method. 10 refs., 1 tab., 2 figs

  17. Antiproton-nucleus interaction: review of the experimental situation

    International Nuclear Information System (INIS)

    This paper will review the experimental situation of a few well-defined channels of the anti-p-nucleus interaction where the antiproton does not annihilate. It will not mention any experiment which studies annihilation of antiporotons in nuclei. The anti-p-nucleus reactions that will be reviewed are the following: 1. A(anti-p,anti-p)A elastic scattering which deals with the anti-p-nucleus system in a positive energy state. 2. Anti-p-nucleus atoms where the anti-p-nucleus system is almost at zero energy and interacts mostly through the Coulomb interaction, the strong interaction being only a perturbation. 3. A(anti-p,p)X proton knock-out reaction used to produce possible bound states or resonances of the anti-p-nucleus system via strong interaction. The main reasons for studying these three channels are to provide information about the anti-p-nucleus optical potential and also, through microscopic calculations which use the elementary anti-NN amplitudes and the nuclear matter densities as inputs, to get information about these quantities. 4. A(anti-p,anti-p')A* inelastic scattering - inelastic in the sense that the nucleus is left in an excited state but the antiproton does not annihilate, that is it deals only with the elastic part of the elementary anti-NN amplitude. Inelastic scattering from collective states also sets constraints on the anti-p-nucleus potential when analysed in terms of coupled-channel calculations. When unnatural parity states are concerned, it provides a sensitive test of the spin and isospin components of these amplitudes. In addition, this paper will focus essentially on the recent experiments performed at LEAR

  18. Molecular-orbital theory for the stopping power of atoms in the low velocity regime:the case of helium in alkali metals

    OpenAIRE

    Dorado, Jose J.; Flores, F.

    1993-01-01

    A free-parameter linear-combination-of-atomic-orbitals approach is presented for analyzing the stopping power of slow ions moving in a metal. The method is applied to the case of He moving in alkali metals. Mean stopping powers for He present a good agreement with local-density-approximation calculations. Our results show important variations in the stopping power of channeled atoms with respect to their mean values.

  19. Molecular dynamics study of helium bubble pressure in tungsten

    International Nuclear Information System (INIS)

    Molecular dynamics simulations were performed to calculate the stress field in a tungsten matrix containing a nano-scale helium bubble. A helium bubble in tungsten is found to consist of a core and an interface of finite thickness of approximately 0.6 nm. The core contains only helium atoms that are uniformly distributed. The interface is composed of both helium and tungsten atoms. In the periphery region of the helium bubble, the stress filed is found to follow the stress formula based on the elasticity theory of solid. The pressure difference between both sides of the interface can be well described by the Young–Laplace equation for the core size of a helium bubble as small as 0.48 nm. A comparison was performed between the pressure in the helium bubble core and the pressure in pure helium. For a core size larger than 0.3 nm, the pressure in the core of a helium bubble is in good agreement with the pressure in pure helium of the same helium density. These results provide guidance to larger scale simulation methods, such as in kinetic Monte Carlo methods and rate theory

  20. Photoionization of helium dimers

    International Nuclear Information System (INIS)

    The helium dimer is one of the most weakly bound systems in the universe. This makes it an interesting quantum mechanical object for investigation. These Van der Waals Clusters can be produced in an expansion of a cryogenic gas jet through a small nozzle into vacuum. In the present experiment we examine the interaction of He dimers with synchrotron radiation at an energy range from 64 to 78 eV. We observed different pathways leading to single ionization of both He atoms of the dimer compound. This two close standing ions begin now to dissociate in cause of their coulomb potential. All charged fragments were detected in coincidence with a COLTRIMS system. Especially Interatomic Coulombic Decay (ICD) and the two step process (TS1) were clearly identified. Furthermore a distribution of the internuclear distance was obtained from the measured Kinetic Energy Release (KER). (orig.)

  1. Superfluidity within a small helium-4 cluster: the microscopic andronikashvili experiment

    Science.gov (United States)

    Grebenev; Toennies; Vilesov

    1998-03-27

    The infrared spectrum of single oxygen carbon sulfide (OCS) molecules was measured inside large superfluid pure helium-4 droplets and nonsuperfluid pure helium-3 droplets, both consisting of about 10(4) atoms. In the helium-4 droplets, sharp rotational lines were observed, whereas in helium-3 only a broad peak was found. This difference is interpreted as evidence that the narrow rotational lines, which imply free rotations, are a microscopic manifestation of superfluidity. Upon addition of 60 helium-4 atoms to the pure helium-3 droplets, the same sharp rotational lines were found; it appears that 60 is the minimum number needed for superfluidity. PMID:9516103

  2. Torsional Alfv\\'en waves in solar partially ionized plasma: effects of neutral helium and stratification

    OpenAIRE

    Zaqarashvili, T. V.; Khodachenko, M. L.; Soler, R.

    2012-01-01

    Ion-neutral collisions may lead to the damping of Alfven waves in chromospheric and prominence plasmas. Neutral helium atoms enhance the damping in certain temperature interval, where the ratio of neutral helium and neutral hydrogen atoms is increased. Therefore, the height-dependence of ionization degrees of hydrogen and helium may influence the damping rate of Alfven waves. We aim to study the effect of neutral helium in the damping of Alfven waves in stratified partially ionized plasma of ...

  3. Effect of cumulative helium bombardments on the surface and structural properties of tungsten

    International Nuclear Information System (INIS)

    The surface and structural properties of tungsten after cumulative helium bombardments have been investigated using molecular dynamics simulations. Helium atoms at 80 eV were injected into tungsten (0 0 1), (1 1 0) and (1 1 1) surfaces. The retention and distribution of helium atoms, the formation and growth of helium clusters and the surface evolution of tungsten substrates are found to be influenced by surface orientations and temperatures

  4. Doubly Differential Cross Sections for Ejection of Electrons from Atomic and Molecular Hydrogen by 30-120 KEV HELIUM(+) Ion Impact

    Science.gov (United States)

    Hsu, Ying-Yuan

    Electrons ejected from atomic and molecular hydrogen in He^+ ion impacts were observed with projectile energies ranging from 30 to 120 keV. The ejection angles observed were 15^circ, 30^circ, 50^circ, 70^ circ, 90^circ, 110^circ, 130^circ and 160^circ with electron energies ranging from 1.5 to 130 eV. Ejected electrons were energy analyzed by an electrostatic analyzer with 5% resolution and were detected by a channel electron multiplier. A Slevin-type RF hydrogen atom source was used to generate a mixed target of atomic and molecular hydrogen. The dissociation fraction of the target was determined from the measurement of 9-eV H^+ ions coming from the break-up of the 2psigma_ {u} state of the H_2 ^+ molecular ion. Methods were devised to extract the electron ejection cross section ratio between hydrogen atoms and molecules. Cross sections for the hydrogen atom were then calculated from additional measurements on pure H_2.. The results are compared to plane-wave-Born approximation (PWBA) calculations, classical-trajectory-Monte-Carlo (CTMC) calculations, and continuum-distorted-wave-eikonal-initial -state (CDW-EIS) calculations for proton impact. Electron loss cross sections are calculated with PWBA and used as a correction to the above calculations.

  5. The muonic helium lamb shift experiment

    Energy Technology Data Exchange (ETDEWEB)

    Goetzfried, Johannes; Krauth, Julian [Max-Planck-Institute of Quantum Optics, Garching (Germany); Collaboration: CREMA collaboration

    2014-07-01

    Because of its high sensitivity on finite size effects of the nucleus, the measurement of the Lamb shift in exotic atoms has been on the wish-list of atomic and nuclear physics for a long time. Our previous experiment allowed to determine the proton radius with an order of magnitude higher precision compared to spectroscopic measurements of ordinary hydrogen. The successor experiment in muonic helium is currently performed at the Paul-Scherrer-Institute in Switzerland. Using a low energy muon beam line muons are stopped within low pressure helium gas, where exotic atoms are created. Here we measure the 2S-2P transition frequency of muonic helium illuminated by a pulsed TiSa-laser system pumped with a newly developed Yb-YAG thin disk laser. This measurement will ultimately improve the values of the charge radii of {sup 3}He{sup +} and {sup 4}He{sup +} by an order of magnitude.

  6. The muonic helium lamb shift experiment

    International Nuclear Information System (INIS)

    Because of its high sensitivity on finite size effects of the nucleus, the measurement of the Lamb shift in exotic atoms has been on the wish-list of atomic and nuclear physics for a long time. Our previous experiment allowed to determine the proton radius with an order of magnitude higher precision compared to spectroscopic measurements of ordinary hydrogen. The successor experiment in muonic helium is currently performed at the Paul-Scherrer-Institute in Switzerland. Using a low energy muon beam line muons are stopped within low pressure helium gas, where exotic atoms are created. Here we measure the 2S-2P transition frequency of muonic helium illuminated by a pulsed TiSa-laser system pumped with a newly developed Yb-YAG thin disk laser. This measurement will ultimately improve the values of the charge radii of 3He+ and 4He+ by an order of magnitude.

  7. Interaction of vacancies with implanted metal atoms in tungsten observed by means of thermal helium desorption spectrometry and perturbed angular correlation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Kolk, G.J. van der; Veen, A. van; Post, K.; Pleiter, F.; Hosson, J.T.M. de

    1985-01-01

    With two techniques the defect complexes are studied when formed after implantation of 5 to 100 keV metal ions into tungsten. Perturbed Angular Correlation (PAC) studies clearly indicate the presence of substitutional impurities in samples implanted with Ag or In. With Thermal Helium Desorption Spectrometry (THDS), however, virtually no substitutional implants (Ag, Cu, Mn, Cr, In) could be seen after implantation due to the nearby vacancies. Migration of vacancies towards the implants during annealing at stage III temperature was observed by means of PAC measurements. At upper stage III vacancy-implant complexes disintegrate, while the substitutional fraction increases. According to THDS, no vacancy-implant complexes are left in the case of 5 keV implantation after annealing to temperatures slightly beyond stage III temperature. In the case of 20 keV implantation a vacancy-type defect is formed which is stable up to 1350 K. The results of both techniques are compared with each other and with model calculations.

  8. Electrons at helium interfaces

    OpenAIRE

    Leiderer, Paul

    1984-01-01

    Two-dimensional layers of charges trapped at the boundaries between the various helium phases strongly interact with these interfaces at high electric fields. The coupling, which leads to an electrohydrodynamic instability, provides new methods for studying helium properties.

  9. Anti-protons in the primary cosmic radiation

    International Nuclear Information System (INIS)

    A knowledge of the flux of antiprotons is of value in examining the manner in which cosmic rays propagate, assuming, as is conventional, that the antiprotons arise from interactions in the I.S.M. A comparison of observed and expected anti p/p ratios is made. (Auth.)

  10. Experiment to measure the gravitational force on the antiproton

    International Nuclear Information System (INIS)

    A collaboration has been formed to measure the acceleration of antiprotons in the earth's gravitational field. The technique is to produce, decelerate, and trap quantities of antiprotons, to cool them to untralow energy, and to measure their acceleration in a time-of-flight experiment. Present plans and the results of initial efforts toward this end are presented

  11. A study of the reactions antiproton-d→antiproton-dπ+π- and antiproton-d→psub(s)antiproton-pπ- at 14.6 GeV/c and a study of charged multiplicity distributions

    International Nuclear Information System (INIS)

    An analysis of two reactions on deuterium has been performed with incident antiprotons of 14.6 GeV/c: antiproton-d→antiproton-dπ+π- and antiproton-d→psub(s)antiproton-pπ-. The final states are dominated by Δ(1236) resonance production and in the coherent reaction the d* effect is observed as at lower incident momenta. At 14.6 GeV/c, it seems that the diffraction dissociation process as well for the incident particle as for the target takes a large part of the production mechanism for the two reactions. A study of charged multiplicity distributions in antiproton-neutron interactions is presented at 5.5, 9.3 and 14.6 GeV/c. The topological cross sections as well as various statistical moments obtained from the charged multiplicities are studied as functions of the incident momentum. A comparison between our results and antiproton-proton and pp data shows, that in the range of incident momenta used, a scaling function which describes antiproton-N and proton-proton interactions does not exist as expected from the KNO model (Koba-Nielsen-Olesen model)

  12. Physics overview of the Fermilab Low Energy Antiproton Facility Workshop

    International Nuclear Information System (INIS)

    A physics overview is presented of the Fermilab workshop to consider a possible high flux, low energy antiproton facility that would use cooled antiprotons from the accumulator ring of the Tevatron collider. Two examples illustrate the power of each a facility to produce narrow states at high rates. Physics topics to which such a facility may be applied are reviewed

  13. Wave Packet Simulations of Antiproton Scattering on Molecular Hydrogen

    OpenAIRE

    Stegeby, Henrik; Kowalewski, Markus; Piszczatowski, Konrad; Karlsson, Hans O.

    2015-01-01

    The problem of antiproton scattering on the molecular Hydrogen is investigated by means of wave packet dynamics. The electronically potential energy surfaces of the antiproton H2 system are presented within this work. Excitation and dissociation probabilities of the molecular Hydrogen for collision energies in the ultra low energy regime below 10 eV are computed.

  14. Calculated LET Spectrum from Antiproton Beams Stopping in Water

    DEFF Research Database (Denmark)

    Bassler, Niels; Holzscheiter, Michael

    2009-01-01

    Antiprotons have been proposed as a potential modality for radiotherapy because the annihilation at the end of range leads to roughly a doubling of physical dose in the Bragg peak region. So far it has been anticipated that the radiobiology of antiproton beams is similar to that of protons in the...

  15. Serach for polarization effects in the antiproton production process

    CERN Multimedia

    It is proposed to study polarization effects in the production of antiprotons at the PS test beam line T11 at 3.5 GeV/c momentum. A polarization in the production process has never been studied but if existing it would allow for a rather simple and cheap way to generate a polarized antiproton beam with the existing facilities at CERN.

  16. Antiproton cloud compression in the ALPHA apparatus at CERN

    International Nuclear Information System (INIS)

    We have observed a new mechanism for compression of a non-neutral plasma, where antiprotons embedded in an electron plasma are compressed by a rotating wall drive at a frequency close to the sum of the axial bounce and rotation frequencies. The radius of the antiproton cloud is reduced by up to a factor of 20 and the smallest radius measured is ∼ 0.2 mm. When the rotating wall drive is applied to either a pure electron or pure antiproton plasma, no compression is observed in the frequency range of interest. The frequency range over which compression is evident is compared to the sum of the antiproton bounce frequency and the system’s rotation frequency. It is suggested that bounce resonant transport is a likely explanation for the compression of antiproton clouds in this regime

  17. Detailed analysis of observed antiprotons in cosmic rays

    Directory of Open Access Journals (Sweden)

    P Davoudifar

    2009-12-01

    Full Text Available In the present work, the origin of antiprotons observed in cosmic rays (above the atmosphere is analyzed in details. We have considered the origin of the primaries, (which their interactions with the interstellar medium is one of the most important sources of antiprotons is a supernova type II then used a diffusion model for their propagation. We have used the latest parameterization for antiproton production cross section in pp collisions (instead of well known parameterization introduced by Tan et al. as well as our calculated residence time for primaries. The resulted intensity shows the secondary antiprotons produced in pp collisions in the galaxy, have a high population as one can not consider an excess for extragalactic antiprotons. Also there is a high degree of uncertainty in different parameters.

  18. Antiproton cloud compression in the ALPHA apparatus at CERN

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, A., E-mail: andrea.gutierrez@triumf.ca [University of British Columbia, Department of Physics and Astronomy (Canada); Ashkezari, M. D. [Simon Fraser University, Department of Physics (Canada); Baquero-Ruiz, M. [University of California at Berkeley, Department of Physics (United States); Bertsche, W. [University of Manchester, School of Physics and Astronomy (United Kingdom); Burrows, C. [Swansea University, Department of Physics, College of Science (United Kingdom); Butler, E. [Centre for Cold Matter, Imperial College (United Kingdom); Capra, A. [York University, Department of Physics and Astronomy (Canada); Cesar, C. L. [Universidade Federal do Rio de Janeiro, Instituto de Física (Brazil); Charlton, M. [Swansea University, Department of Physics, College of Science (United Kingdom); Dunlop, R. [Simon Fraser University, Department of Physics (Canada); Eriksson, S. [Swansea University, Department of Physics, College of Science (United Kingdom); Evetts, N. [University of British Columbia, Department of Physics and Astronomy (Canada); Fajans, J. [University of California at Berkeley, Department of Physics (United States); Friesen, T. [Aarhus University, Department of Physics and Astronomy (Denmark); Fujiwara, M. C.; Gill, D. R. [TRIUMF (Canada); Hangst, J. S. [Aarhus University, Department of Physics and Astronomy (Denmark); Hardy, W. N. [University of British Columbia, Department of Physics and Astronomy (Canada); Hayden, M. E. [Simon Fraser University, Department of Physics (Canada); Isaac, C. A. [Swansea University, Department of Physics, College of Science (United Kingdom); and others

    2015-11-15

    We have observed a new mechanism for compression of a non-neutral plasma, where antiprotons embedded in an electron plasma are compressed by a rotating wall drive at a frequency close to the sum of the axial bounce and rotation frequencies. The radius of the antiproton cloud is reduced by up to a factor of 20 and the smallest radius measured is ∼ 0.2 mm. When the rotating wall drive is applied to either a pure electron or pure antiproton plasma, no compression is observed in the frequency range of interest. The frequency range over which compression is evident is compared to the sum of the antiproton bounce frequency and the system’s rotation frequency. It is suggested that bounce resonant transport is a likely explanation for the compression of antiproton clouds in this regime.

  19. Intensity-Frontier Antiproton Physics with The Antiproton Annihilation Spectrometer (TAPAS) at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Apollinari, Giorgio; /Fermilab; Asner, David M.; /PNL, Richland; Baldini, Wander; /INFN, Ferrara; Bartoszek, Larry; Broemmelsiek, Daniel R.; Brown, Charles N.; /Fermilab; Chakravorty, Alak; /St. Xavier U., Chicago; Colas, Paul; /Saclay; Derwent, Paul; /Fermilab; Drutskoy, Alexey; /Moscow, ITEP; Fortner, Michael; /Northern Illinois U. /Saclay /Indian Inst. Tech., Hyderabad

    2011-11-01

    The Fermilab Antiproton Source is the world's most intense source of antimatter. With the Tevatron program now behind us, this unique facility can help make the case for Fermilab's continued accelerator operations. The Antiproton Source can be used for unique, dedicated antimatter studies, including medium-energy {bar p}-annihilation experiments. We propose to assemble a powerful, yet cost-effective, solenoidal magnetic spectrometer for antiproton-annihilation events, and to use it at the Fermilab Antiproton Accumulator to measure the charm production cross section, study rare hyperon decays, search for hyperon CP asymmetry, precisely measure the properties of several charmonium and nearby states, and make the first measurements of the Drell-Yan continuum in medium-energy antiproton annihilation. Should the charm production cross section be as large as some have proposed, we will also be able to measure D{sup 0}-{bar D}{sup 0} mixing with high precision and discover (or sensitively limit) charm CP violation. The observation of charm or hyperon CP violation would be evidence for physics beyond the Standard Model, with possible implications for the origin of the baryon asymmetry of the universe - the question of what happened to all the antimatter that must have been produced in the Big Bang. The experiment will be carried out by an international collaboration and will require some four years of running time. As possibly the sole hadron experiment in progress at Fermilab during that time, it will play an important role in maintaining a broad particle physics program at Fermilab and in the U.S. It will thus help us to continue attracting creative and capable young people into science and technology, and introducing them to the important technologies of accelerators, detectors, and data acquisition and analysis - key roles in society that accelerator-based particle physics has historically played.

  20. Protonium formation in slow collisions of antiprotons with hydrogen atoms

    Energy Technology Data Exchange (ETDEWEB)

    Sakimoto, Kazuhiro [Institute of Space and Astronautical Science, Yoshinodai, Sagamihara (Japan)]. E-mail: sakimoto@pub.isas.ac.jp

    2001-05-14

    Protonium formation p-bar+H{yields}p-barp+e is investigated theoretically at centre-of-mass collision energies less than E=10 eV. In previous studies on the break-up ionization p-bar+H{yields}p-bar+p+e, the present author introduced the direct numerical method using a discrete-variable-representation technique to solve the time-dependent (semiclassical) Schroedinger equation. The same method is applied to protonium formation. The reliability of the adiabatic molecular picture is examined for the calculation of the formation cross section. At very low energies, the centrifugal barrier plays an important role in the protonium formation as found in a variety of ion-molecule chemical reactions. (author)

  1. Protonium formation in slow collisions of antiprotons with hydrogen atoms

    International Nuclear Information System (INIS)

    Protonium formation p-bar+H→p-barp+e is investigated theoretically at centre-of-mass collision energies less than E=10 eV. In previous studies on the break-up ionization p-bar+H→p-bar+p+e, the present author introduced the direct numerical method using a discrete-variable-representation technique to solve the time-dependent (semiclassical) Schroedinger equation. The same method is applied to protonium formation. The reliability of the adiabatic molecular picture is examined for the calculation of the formation cross section. At very low energies, the centrifugal barrier plays an important role in the protonium formation as found in a variety of ion-molecule chemical reactions. (author)

  2. Helium on Venus - Implications for uranium and thorium

    Science.gov (United States)

    Prather, M. J.; Mcelroy, M. B.

    1983-01-01

    Helium is removed at an average rate of 10 to the 6th atoms per square centimeter per second from Venus's atmosphere by the solar wind following ionization above the plasmapause. The surface source of helium-4 on Venus is similar to that on earth, suggesting comparable abundances of crustal uranium and thorium.

  3. Thermal stability of helium-vacancy clusters in iron

    CERN Document Server

    Morishita, K; Wirth, B D; Díaz de la Rubia, T

    2003-01-01

    Molecular dynamics calculations were performed to evaluate the thermal stability of helium-vacancy clusters (He sub n V sub m) in Fe using the Ackland Finnis-Sinclair potential, the Wilson-Johnson potential and the Ziegler-Biersack-Littmark-Beck potential for describing the interactions of Fe-Fe, Fe-He and He-He, respectively. Both the calculated numbers of helium atoms, n, and vacancies, m, in clusters ranged from 0 to 20. The binding energies of an interstitial helium atom, an isolated vacancy and a self-interstitial iron atom to a helium-vacancy cluster were obtained from the calculated formation energies of clusters. All the binding energies do not depend much on cluster size, but they primarily depend on the helium-to-vacancy ratio (n/m) of clusters. The binding energy of a vacancy to a helium-vacancy cluster increases with the ratio, showing that helium increases cluster lifetime by dramatically reducing thermal vacancy emission. On the other hand, both the binding energies of a helium atom and an iron ...

  4. Helium on Venus: Implications for uranium and thorium

    OpenAIRE

    Prather, MJ; McElroy, MB

    1983-01-01

    Helium is removed at an average rate of 106 atoms per square centimeter per second from Venus's atmosphere by the solar wind following ionization above the plasmapause. The surface source of helium-4 on Venus is similar to that on Earth, suggesting comparable abundances of crustal uranium and thorium.

  5. Rapidly pulsed helium droplet source

    Energy Technology Data Exchange (ETDEWEB)

    Pentlehner, Dominik; Riechers, Ricarda; Dick, Bernhard; Slenczka, Alkwin [Institute for Physical and Theoretical Chemistry, University of Regensburg, 93053 Regensburg (Germany); Even, Uzi; Lavie, Nachum; Brown, Raviv; Luria, Kfir [Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv (Israel)

    2009-04-15

    A pulsed valve connected to a closed-cycle cryostat was optimized for producing helium droplets. The pulsed droplet beam appeared with a bimodal size distribution. The leading part of the pulse consists of droplets suitable for doping with molecules. The average size of this part can be varied between 10{sup 4} and 10{sup 6} helium atoms, and the width of the distribution is smaller as compared to a continuous-flow droplet source. The system has been tested in a single pulse mode and at repetition rates of up to 500 Hz with almost constant intensity. The droplet density was found to be increased by more than an order of magnitude as compared to a continuous-flow droplet source.

  6. Helium precipitation in. cap alpha. -Fe

    Energy Technology Data Exchange (ETDEWEB)

    Caspers, L.M.; van Veen, A.; Ypma, M.R.; van der Kolk, G.J. (Interuniversitair Reactor Inst., Delft (Netherlands))

    1982-03-16

    The filling of a vacancy with helium atoms is studied with a programme simulating the relaxation of lattice atoms around the complex. Three filling modes are described. Helium filled V/sub 2/, V/sub 3/, and V/sub 4/ complexes are also considered and the energetics of the mutation reactions of He/sub n/V ..-->.. He/sub m>n/V/sub 2/ ..-->.. He/sub p>m/V/sub 3/ ..-->.. He/sub q>p/V/sub 4/ is studied. It is shown that these mutation reactions are more probable when the emitted interstitials remain bound to the mutation products. The He/sub n/V/sub m/I/sub p/ complexes thus formed are stable against reduction, in agreement with experiments. Also the formation of these complexes could explain why helium precipitation proceeds in a two-dimensional way as observed by TEM. The general trend found in helium desorption measurements viz. a decrease in helium binding energy until some 6 to 10 He atoms are trapped and thereafter an increase in binding energy is also found in this computer simulation study.

  7. LEAP [Low-Energy Antiproton]: A balloon-borne search for low-energy cosmic-ray antiprotons

    International Nuclear Information System (INIS)

    The LEAP (Low-Energy Antiproton) experiment is a search for cosmic-ray antiprotons in the 120 MeV to 1.2 GeV kinetic energy range. The motivation for this project was the result announced by Buffington et. al. (1981) that indicated an anomalously high antiproton flux below 300 MeV; this result has compelled theorists to propose sources of primary antiprotons above the small secondary antiproton flux produced by high energy cosmic-ray collisions with nuclei in the interstellar medium. LEAP consisted of the NMSU magnetic spectrometer, a time-of-flight system designed at Goddard Space Flight Center, two scintillation detectors, and a Cherenkov counter designed and built at the University of Arizona. Analysis of flight data performed by the high-energy astrophysics group at Goddard Space Flight Center revealed no antiproton candidates found in the 120 MeV to 360 MeV range; 3 possible antiproton candidate events were found in the 500 MeV to 1.2 GeV range in an analysis done here at the University of Arizona. However, since it will be necessary to sharpen the calibration on all of the LEAP systems in order to positively identify these events as antiprotons, only an upper limit has been determined at present. Thus, combining the analyses performed at the University of Arizona and Goddard Space Flight Center, 90% confidence upper limits of 3.5 x 10-5 in the 120 MeV to 360 MeV range and 2.3 x 10-4 in the 500 MeV to 1.2 GeV range for the antiproton/proton ratio is indicated by the LEAP results. LEAP disagrees sharply with the results of the Buffington group, indicating a low antiproton flux at these energies

  8. Cross section measurements of the processes occurring in the fragmentation of H{sub n}{sup +} (3 {<=} n {<=} 35) hydrogen clusters induced by high speed (60 keV/u) collisions on helium atoms; Mesure des sections efficaces des differents processus intervenant dans la fragmentation d`agregats d`hydrogene H{sub n}{sup +} (3 {<=} n {<=} 35) induite par collision a haute vitesse (60 keV/u) sur un atome d`helium

    Energy Technology Data Exchange (ETDEWEB)

    Louc, Sandrine [Inst. de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

    1997-09-15

    Different processes involved in the fragmentation of ionised hydrogen clusters H{sub 3} + (H{sub 2}){sub (n-3)/2} (n = 5-35) have been studied in the same experiment: the fragmentation of the cluster is induced by the collision with an helium atom at high velocity ({approx_equal} c/100). The collision is realised in reversed kinematic - clusters are accelerated - which allows the detection of neutral and charged fragments. The different channels of fragmentation are identified by using coincidence techniques. For all the cluster sizes studied the capture cross sections of one electron of the target by the cluster is equal to the capture cross section of the H{sub 3}{sup +} ion. In the same way, the dissociation cross section of the H{sub 3}{sup +} core of the cluster does not depend on cluster size. These fragmentation processes are due to the interaction of H{sub 3}{sup +} core of the cluster and the helium atom without ionization of another component of the cluster. On the contrary, the cross sections of loss of one, two and three molecules by the cluster and the dissociation cross section of the cluster in all its molecular components depends strongly on the cluster size. This dependence is different from the one measured for the metastable decay of the cluster. Thus, the process of loss of molecules induced by a collision should correspond to a different dissociation mechanism. In regard of the singularities observed for the size dependence, the H{sub 9}{sup +}, H{sub 15}{sup +}, H{sub 19}{sup +} and H{sub 29}{sup +} clusters could be the `core` of the biggest clusters. These observation are in agreement with the size effects of smaller magnitude observed for the dissociation cross section (all the processes). The values of the cross section for the process of at least one ionization of the cluster indicate that about 80% of the fragmentation events result from this process. (author) 114 refs., 74 figs., 9 tabs.

  9. Annihilation of low energy antiprotons in silicon

    CERN Document Server

    Aghion, S; Belov, A S; Bonomi, G; Bräunig, P; Bremer, J; Brusa, R S; Burghart, G; Cabaret, L; Caccia, M; Canali, C; Caravita, R; Castelli, F; Cerchiari, G; Cialdi, S; Comparat, D; Consolati, G; Derking, J H; Di Domizio, S; Di Noto, L; Doser, M; Dudarev, A; Ferragut, R; Fontana, A; Genova, P; Giammarchi, M; Gligorova, A; Gninenko, S N; Haider, S; Harasimovic, J; Huse, T; Jordan, E; Jørgensen, L V; Kaltenbacher, T; Kellerbauer, A; Knecht, A; Krasnický, D; Lagomarsino, V; Magnani, A; Mariazzi, S; Matveev, V A; Moia, F; Nebbia, G; Nédélec, P; Pacifico, N; Petrácek, V; Prelz, F; Prevedelli, M; Regenfus, C; Riccardi, C; Røhne, O; Rotondi, A; Sandaker, H; Susa, A; Vasquez, M A Subieta; Špacek, M; Testera, G; Welsch, C P; Zavatarelli, S

    2013-01-01

    The goal of the AE$\\mathrm{\\bar{g}}$IS experiment at the Antiproton Decelerator (AD) at CERN, is to measure directly the Earth's gravitational acceleration on antimatter. To achieve this goal, the AE$\\mathrm{\\bar{g}}$IS collaboration will produce a pulsed, cold (100 mK) antihydrogen beam with a velocity of a few 100 m/s and measure the magnitude of the vertical deflection of the beam from a straight path. The final position of the falling antihydrogen will be detected by a position sensitive detector. This detector will consist of an active silicon part, where the annihilations take place, followed by an emulsion part. Together, they allow to achieve 1$%$ precision on the measurement of $\\bar{g}$ with about 600 reconstructed and time tagged annihilations. We present here, to the best of our knowledge, the first direct measurement of antiproton annihilation in a segmented silicon sensor, the first step towards designing a position sensitive silicon detector for the AE$\\mathrm{\\bar{g}}$IS experiment. We also pr...

  10. Efficient magneto-optical trapping of a metastable helium gas

    Science.gov (United States)

    Pereira Dos Santos, F.; Perales, F.; Léonard, J.; Sinatra, A.; Wang, J.; Pavone, F. S.; Rasel, E.; Unnikrishnan, C. S.; Leduc, M.

    2001-04-01

    This article presents a new experiment aiming at BEC of metastable helium atoms. It describes the design of a high flux discharge source of atoms and a robust laser system using a DBR diode coupled with a high power Yb doped fiber amplifier for manipulating the beam of metastable atoms. The atoms are trapped in a small quartz cell in an extreme high vacuum. The trapping design uses an additional laser (repumper) and allows the capture of a large number of metastable helium atoms (approximately 10^9) in a geometry favorable for loading a tight magnetostatic trap.

  11. Exotic helium molecules; Molecules exotiques d'helium

    Energy Technology Data Exchange (ETDEWEB)

    Portier, M

    2007-12-15

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  12. Basic physics program for a low energy antiproton source in North America

    International Nuclear Information System (INIS)

    We summarize much of the important science that could be learned at a North American low energy antiproton source. It is striking that there is such a diverse and multidisciplinary program that would be amenable to exploration. Spanning the range from high energy particle physics to nuclear physics, atomic physics, and condensed matter physics, the program promises to offer many new insights into these disparate branches of science. It is abundantly clear that the scientific case for rapidly proceeding towards such a capability in North America is both alluring and strong. 38 refs., 2 tabs

  13. Helium vs. Proton Induced Displacement Damage in Electronic Materials

    Science.gov (United States)

    Ringo, Sawnese; Barghouty, A. F.

    2010-01-01

    In this project, the specific effects of displacement damage due to the passage of protons and helium nuclei on some typical electronic materials will be evaluated and contrasted. As the electronic material absorbs the energetic proton and helium momentum, degradation of performance occurs, eventually leading to overall failure. Helium nuclei traveling at the same speed as protons are expected to impart more to the material displacement damage; due to the larger mass, and thus momentum, of helium nuclei compared to protons. Damage due to displacement of atoms in their crystalline structure can change the physical properties and hence performance of the electronic materials.

  14. Nonlinear density dependence of the positron decay rate in helium

    International Nuclear Information System (INIS)

    The decay rate of thermalized positrons in helium is calculated as a function of the fluid density, incorporating the multiple scattering of the positron off the atoms. The obtained nonlinearity agrees with experimental data outside the self-trapping region

  15. Non-dissociative and dissociative ionization of N2, CO, CO2, and CH4 by impact of 50-6000 keV protons and antiprotons

    International Nuclear Information System (INIS)

    Measurements of the cross section for non-dissociative single ionization and the cross sections for the creation of charged fragments have been performed for 50-6000 keV antiproton and proton impact on N2, CO, CO2, and CH4. The results support the understanding of the ionization phenomenon that has been achieved via measurements with fundamental charged particles on atoms. The present high-energy antiproton fragmentation data supply a stringent test of the validity of the published electron-impact fragmentation data which, unfortunately, most of them fail. (Author)

  16. Retention of hydrogen isotopes and helium in nickel

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Mitsumasa; Sato, Rikiya; Yamaguchi, Kenji; Yamawaki, Michio [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab.

    1996-10-01

    In the present study, a thin foil of nickel was irradiated by H{sub 2}{sup +}, D{sub 2}{sup +} and He{sup +} to a fluence of 1.2-6.0x10{sup 20}/m{sup 2} using the TBTS (Tritium Beam Test System) apparatus. The thermal desorption spectroscopy (TDS) technique was employed to evaluate the total amount of retained hydrogen isotope and helium atoms in nickel. In the spectra, two peaks appeared at 440-585K and 720-735K for helium. Hydrogen isotopes irradiation after helium preirradiation were found to enhance the helium release and to decrease the peak temperatures. Helium irradiation after hydrogen isotopes preirradiation were found to enhance the helium release, but the peak temperature showed little difference from that without preirradiation. (author)

  17. Full Scale Thermo-hydraulic Simulation of a Helium-Helium Printed Circuit Heat Exchanger

    International Nuclear Information System (INIS)

    In this paper, the thermo-hydraulic full scale simulation is performed to study the temperature distributions, thermal stress, pressure drop and outlet temperature in a Helium-Helium printed circuit heat exchanger (PCHE) in a VHTR simulate helium loop. The entire PCHE is composed of 40 stacks of rectangular shaped micro-channels for helium gas [type A] (inlet temperature, 400 .deg. C) and 40 stacks of semi-ellipse shaped micro-channels for helium [type B] (inlet temperature, 300 .deg. C). The experimental result is compared to that of computer simulation, COMSOL multi-physics software. The Helium-Helium PCHE is considered a prototype of the newly developed PCHE by Korea Atomic Energy Research Institute (KAERI). The full scale thermo-hydraulic simulation was successfully performed to obtain temperature distribution, pressure drop and thermal stress in 40 sets of flow channel stacks in a helium-helium printed circuit heat exchanger in a VHTR simulate helium loop. We obtained a quite similar temperature distribution with the 3D measured infrared temperature distribution. To our knowledge, this is the first full scale numerical study on the PCHE, which considers all microchannels, that the convection effect on the outside surfaces of the PCHE is applied. The very high-temperature reactor (VHTR) or high-temperature gas-cooled reactor(HTGR) is a fourth-generation nuclear power reactor that uses the ceramic coated fuel, TRISO, in which the fission gas does not leak even at temperatures higher than 1600 .deg. C. The VHTR necessarily requires an intermediate loop composed of a hot gas duct (HGD), an intermediate heat exchanger (IHX) and a process heat exchanger (PHE). The IHX is one of the important components of VHTR system because the IHX transfers the 950 .deg. C of high temperature massive heat to a hydrogen production plant or power conversion unit at high system pressure

  18. Cooling with Superfluid Helium

    CERN Document Server

    Lebrun, P

    2014-01-01

    The technical properties of helium II (‘superfluid’ helium) are presented in view of its applications to the cooling of superconducting devices, particularly in particle accelerators. Cooling schemes are discussed in terms of heat transfer performance and limitations. Large-capacity refrigeration techniques below 2 K are reviewed, with regard to thermodynamic cycles as well as process machinery. Examples drawn from existing or planned projects illustrate the presentation. Keywords: superfluid helium, cryogenics

  19. Superfluid Helium 3: Link between Condensed Matter Physics and Particle Physics

    OpenAIRE

    Vollhardt, D.; Woelfle, P.

    2000-01-01

    The discovery of the superfluid phases of Helium 3 in 1971 opened the door to one of the most fascinating systems known in condensed matter physics. Superfluidity of Helium 3, originating from pair condensation of Helium 3 atoms, turned out to be the ideal testground for many fundamental concepts of modern physics, such as macroscopic quantum phenomena, (gauge-)symmetries and their spontaneous breakdown, topological defects, etc. Thereby the superfluid phases of Helium 3 enriched condensed ma...

  20. A new antiproton beam transfer scheme without coalescing

    Energy Technology Data Exchange (ETDEWEB)

    Weiren Chou et al.

    2003-06-04

    An effective way to increase the luminosity in the Fermilab Tevatron collider program Run2 is to improve the overall antiproton transfer efficiency. During antiproton coalescing in the Main Injector (MI), about 10-15% particles get lost. This loss could be avoided in a new antiproton transfer scheme that removes coalescing from the process. Moreover, this scheme would also eliminate emittance dilution due to coalescing. This scheme uses a 2.5 MHz RF system to transfer antiprotons from the Accumulator to the Main Injector. It is then followed by a bunch rotation in the MI to shorten the bunch length so that it can be captured by a 53 MHz RF bucket. Calculations and ESME simulations show that this scheme works. No new hardware is needed to implement this scheme.

  1. Antiproton cell experiment: antimatter is a better killer

    CERN Document Server

    2006-01-01

    "European Organization for Nuclear Research is reporting that results from a three year study of antiprotons for neoplasm irrdiation showed a better cellular killer with a smaller lethal dose." (1,5 page)

  2. Do positrons and antiprotons respect the weak equivalence principle?

    International Nuclear Information System (INIS)

    We resolve the difficulties which Morrison identified with energy conservation and the gravitational red-shift when particles of antimatter, such as the positron and antiproton, do not respect the weak equivalence principle. 13 refs

  3. Antiprotons from dark matter annihilation in the Galaxy: astrophysical uncertainties

    CERN Document Server

    Evoli, Carmelo; Grasso, Dario; Maccione, Luca; Ullio, Piero

    2011-01-01

    The latest years have seen steady progresses in WIMP dark matter (DM) searches, with hints of possible signals suggested by both direct and indirect detection experiments. Antiprotons can play a key role validating those interpretations since they are copiously produced by WIMP annihilations in the Galactic halo, and the secondary antiproton background produced by Cosmic Ray (CR) interactions is predicted with fair accuracy and matches the observed spectrum very well. Using the publicly available numerical DRAGON code, we reconsider antiprotons as a tool to constrain DM models discussing its power and limitations. We provide updated constraints on a wide class of annihilating DM models by comparing our predictions against the most up-to-date ap measurements, taking also into account the latest spectral information on the p, He and other CR nuclei fluxes. Doing that, we probe carefully the uncertainties associated to both secondary and DM originated antiprotons, by using a variety of distinctively different as...

  4. Helium behaviour in implanted boron carbide

    Directory of Open Access Journals (Sweden)

    Motte Vianney

    2015-01-01

    Full Text Available When boron carbide is used as a neutron absorber in nuclear power plants, large quantities of helium are produced. To simulate the gas behaviour, helium implantations were carried out in boron carbide. The samples were then annealed up to 1500 °C in order to observe the influence of temperature and duration of annealing. The determination of the helium diffusion coefficient was carried out using the 3He(d,p4He nuclear reaction (NRA method. From the evolution of the width of implanted 3He helium profiles (fluence 1 × 1015/cm2, 3 MeV corresponding to a maximum helium concentration of about 1020/cm3 as a function of annealing temperatures, an Arrhenius diagram was plotted and an apparent diffusion coefficient was deduced (Ea = 0.52 ± 0.11 eV/atom. The dynamic of helium clusters was observed by transmission electron microscopy (TEM of samples implanted with 1.5 × 1016/cm2, 2.8 to 3 MeV 4He ions, leading to an implanted slab about 1 μm wide with a maximum helium concentration of about 1021/cm3. After annealing at 900 °C and 1100 °C, small (5–20 nm flat oriented bubbles appeared in the grain, then at the grain boundaries. At 1500 °C, due to long-range diffusion, intra-granular bubbles were no longer observed; helium segregates at the grain boundaries, either as bubbles or inducing grain boundaries opening.

  5. Rescattering effects in antiproton deuteron annihilation at intermediate energies

    International Nuclear Information System (INIS)

    In this paper higher order corrections to the single scattering term for antiproton deuteron annihilation are evaluated. As dominant corrections the initial state interaction of the antiprotons and the rescattering of pions are considered. For low spectator momenta, these corrections cause a strong modulation of the distribution in the invariant mass of the annihilation pions, which could modify the parameters of the resonant baryonium states

  6. Antiproton-proton annihilation at rest into two mesons

    International Nuclear Information System (INIS)

    Branching ratios for antiproton-proton annihilations at rest into two mesons are given. The data were obtained at LEAR by stopping antiprotons in a liquid hydrogen target. Both charged and neutral annihilation products were detected in the Crystal Barrel detector. Representative data are presented, and their bearing on the general picture of annihilation dynamics is discussed. In addition, preliminary branching ratios for two-body radiative annihilations are given. (orig.)

  7. Cosmic Antiproton Constraints on Effective Interactions of the Dark Matter

    CERN Document Server

    Cheung, Kingman; Yuan, Tzu-Chiang

    2010-01-01

    Using an effective interaction approach to describe the interactions between the dark matter particle and the light degrees of freedom of the standard model, we calculate the antiproton flux due to the annihilation of the dark matter in the Galactic Halo and compare to the most recent antiproton spectrum of the PAMELA experiment. We obtain useful constraints on the size of the effective interactions that are comparable to those deduced from collider and gamma-ray experiments.

  8. Cosmic antiproton constraints on effective interactions of the dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, Kingman [Division of Quantum Phases and Devices, School of Physics, Konkuk university, Seoul 143-701 (Korea, Republic of); Tseng, Po-Yan [Department of Physics, National Tsing Hua University, Hsinchu 300, Taiwan (China); Yuan, Tzu-Chiang, E-mail: cheung@phys.nthu.edu.tw, E-mail: tcyuan@phys.sinica.edu.tw, E-mail: d9722809@oz.nthu.edu.tw [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China)

    2011-01-01

    Using an effective interaction approach to describe the interactions between the dark matter particle and the light degrees of freedom of the standard model, we calculate the antiproton flux due to the annihilation of the dark matter in the Galactic Halo and compare to the most recent antiproton spectrum of the PAMELA experiment. We obtain useful constraints on the size of the effective interactions that are comparable to those deduced from collider and gamma-ray experiments.

  9. Cosmic antiproton constraints on effective interactions of the dark matter

    International Nuclear Information System (INIS)

    Using an effective interaction approach to describe the interactions between the dark matter particle and the light degrees of freedom of the standard model, we calculate the antiproton flux due to the annihilation of the dark matter in the Galactic Halo and compare to the most recent antiproton spectrum of the PAMELA experiment. We obtain useful constraints on the size of the effective interactions that are comparable to those deduced from collider and gamma-ray experiments

  10. Thermal Annealing Behavior of Helium in Ti Films Deposited by Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lei; HE Zhi-Jiang; LIU Chao-Zhuo; WANG Xu-Fei; SHI Li-Qun

    2012-01-01

    Helium contents of up to 30at.% are prepared in sputter-deposited Ti Silms. Isochronal annealing behaviors of helium including the depth profiles and the evolution of helium bubbles in the fi1ms at different temperatures are examined by ion beam analysis including Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA), as well as thermal helium desorption spectroscopy (THDS). It is found that the energy spreading induced by structural inhomogeneities in the spectra of RBS and ERDA as well as the increment in the width of spectra occurs, which corresponds to the change of stopping cross-section of helium atoms in the Ti 61m due to the change of physical-state of helium in the evolution of helium bubble. The ion beam analysis on the helium evolution is consistent with the THDS measurement. Ion beam technique opens interesting possibilities in the characterizing on the growth of helium bubbles.%Helium contents of up to 30at.% are prepared in sputter-deposited Ti films.Isochronal annealing behaviors of helium including the depth profiles and the evolution of helium bubbles in the films at different temperatures are examined by ion beam analysis including Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA),as well as thermal helium desorption spectroscopy (THDS).It is found that the energy spreading induced by structural inhomogeneities in the spectra of RBS and ERDA as well as the increment in the width of spectra occurs,which corresponds to the change of stopping cross-section of helium atoms in the Ti film due to the change of physical-state of helium in the evolution of helium bubble.The ion beam analysis on the helium evolution is consistent with the THDS measurement.Ion beam technique opens interesting possibilities in the characterizing on the growth of helium bubbles.

  11. Helium the disappearing element

    CERN Document Server

    Sears, Wheeler M

    2015-01-01

    The subject of the book is helium, the element, and its use in myriad applications including MRI machines, particle accelerators, space telescopes, and of course balloons and blimps. It was at the birth of our Universe, or the Big Bang, where the majority of cosmic helium was created; and stellar helium production continues. Although helium is the second most abundant element in the Universe, it is actually quite rare here on Earth and only exists because of radioactive elements deep within the Earth. This book includes a detailed history of the discovery of helium, of the commercial industry built around it, how the helium we actually encounter is produced within the Earth, and the state of the helium industry today. The gas that most people associate with birthday party balloons is running out. “Who cares?” you might ask. Well, without helium, MRI machines could not function, rockets could not go into space, particle accelerators such as those used by CERN could not operate, fiber optic cables would not...

  12. Calculations of line absorption for the Voigt profile and some specific lines of helium

    Energy Technology Data Exchange (ETDEWEB)

    Kato, I.; Yonehara, A.

    1980-07-01

    Calculations of the line absorption for the 396.5- , 361.4- , 318.7- , 492.2- , 587.6- , and 447.1-nm lines of helium have been performed for the Voigt profile. These results can be used to measure the absolute concentration of helium metastable atoms and several other excited atoms by the reabsorption method.

  13. Laser Spectroscopic Measurement of Helium Isotope Ratios

    CERN Document Server

    Wang, L B; Holt, R J; Lu, Z T; O'Connor, T P; Sano, Y; Sturchio, N C

    2003-01-01

    A sensitive laser spectroscopic method has been applied to the quantitative determination of the isotope ratio of helium at the level of 3He/4He = 10^-7 - 10^-5. The resonant absorption of 1083 nm laser light by the metastable 3He atoms in a discharge cell was measured with the frequency modulation saturation spectroscopy technique while the abundance of 4He was measured by a direct absorption technique. The results on three different samples extracted from the atmosphere and commercial helium gas were in good agreement with values obtained with mass spectrometry. The achieved 3-sigma detection limit of 3He in helium is 4 x 10^-9. This demonstration required a 200 micro-L STP sample of He. The sensitivity can be further improved, and the required sample size reduced, by several orders of magnitude with the addition of cavity enhanced spectroscopy.

  14. Laser spectroscopic measurement of helium isotope ratios

    International Nuclear Information System (INIS)

    A sensitive laser spectroscopic method has been applied to the quantitative determination of the isotope ratio of helium at the level of 3He/4He = 10-7--10-5. The resonant absorption of 1083 nm laser light by the metastable 3He atoms in a discharge cell was measured with the frequency modulation saturation spectroscopy technique while the abundance of 4He was measured by a direct absorption technique. The results on three different samples extracted from the atmosphere and commercial helium gas were in good agreement with values obtained with mass spectrometry. The achieved 3σ detection limit of 3He in helium is 4 x 10-9. This demonstration required a 200 μL STP sample of He. The sensitivity can be further improved, and the required sample size reduced, by several orders of magnitude with the addition of cavity enhanced spectroscopy.

  15. Electron cooling for low-energy antiprotons

    International Nuclear Information System (INIS)

    Divergence and size of stored ion beams can be reduced superimposing on them an intense, monoenergetic electron beam with little transverse motion ('electron cooling'). The present work first considers the theoretical foundations of the method and then describes the planning and construction of an electron beam device for cooling antiprotons with MeV energies in the storage ring LEAR and CERN. With respect to the quantitative description of the method, the microscopic processes during the damping of the ion motion, the effect of the damping on an ion in a storage ring, and the properties of the intense, magnetically guided electron beam are discussed. Special attention is paid to the improvement of ion beam cooling due to the magnetic field guiding the electron beam. The electron beam device, operated in ultra-high vacuum, and the experience gained during its construction are described; experiments performed during the test period are presented. The work further develops a numerical simulation of electron cooling on the basis of the theory discussed. Given realistic external parameters, the simulation yields cooling times and equilibrium states of the ion beam during electron cooling in a storage ring. Finally, non-destructive methods for measuring the velocity distribution in the electron beam are described, which may prove helpful for optimizing the beam cooling. (orig.)

  16. Antiproton-impact ionization of H2

    International Nuclear Information System (INIS)

    Ionization processes in antiproton collisions with H2 are studied by direct solution of the time-dependent Schroedinger equation. A time-dependent close-coupling method based on an expansion of a one-electron 3D wavefunction in the field of H+2 is used to calculate single-ionization cross sections at incident energies ranging from 50 keV to 1.5 MeV. Averaging over the molecular orientations, the single-ionization cross sections are in reasonable agreement with time-dependent basis set calculations and experiment. A time-dependent close-coupling method based on an expansion of a two-electron 6D wavefunction in the field of H2+2 is used to calculate single- and double-ionization cross sections at an incident energy of 100 keV. Initiatory 6D results for the H+2 production cross section range are somewhat lower than experiment, while the H+ production cross section range brackets experiment.

  17. Charm production in antiproton-proton annihilation

    CERN Document Server

    Haidenbauer, J

    2010-01-01

    We study the production of charmed mesons (D) and baryons (Lambda_c) in antiproton-proton (app) annihilation close to their respective production thresholds. The elementary charm production process is described by either baryon/meson exchange or by quark/gluon dynamics. Effects of the interactions in the initial and final states are taken into account rigorously. The calculations are performed in close analogy to our earlier study on app -> antiLambda-Lambda and app -> antiK-K by connecting the processes via SU(4) flavor symmetry. Our predictions for the antiLambda_c-Lambda_c production cross section are in the order of 1 to 7 mb, i.e. a factor of around 10-70 smaller than the corresponding cross sections for antiLambda-Lambda However, they are 100 to 1000 times larger than predictions of other model calculations in the literature. On the other hand, the resulting cross sections for antiD-D production are found to be in the order of 10^{-2} -- 10^{-1} microbarn and they turned out to be comparable to those ob...

  18. Helium mobility in advanced nuclear ceramics

    International Nuclear Information System (INIS)

    The main goal of this work is to improve our knowledge on the mechanisms able to drive the helium behaviour in transition metal carbides and nitrides submitted to thermal annealing or ion irradiation. TiC, TiN and ZrC polycrystals were implanted with 3 MeV 3He ions at room temperature in the fluence range 2 * 1015 et 6 * 1016 cm-2. Some of them have been pre-irradiated with self-ions (14 MeV Ti or Zr). Fully controlled thermal annealing tests were subsequently carried out in the temperature range 1000 - 1600 C for two hours. The evolution of the helium depth distribution in function of implantation dose, temperature and pre-irradiation dose was measured thanks to the deuteron-induced nuclear reaction 3He(d, p0)4He between 900 keV and 1.8 MeV. The microstructure of implanted and annealed samples was investigated by transmission electron microscopy on thin foils prepared using the FIB technique. Additional characterization tools, as X-ray diffraction and Raman microspectrometry, have been also applied in order to obtain complementary information. Among the most relevant results obtained, the following have to be outlined: - double-peak helium depth profile was measured on as implanted sample for the three compounds. The first peak is located near the end of range and includes the major part of helium, a second peak located close to the surface corresponds to the helium atoms trapped by the native vacancies; - the helium retention capacity in transition metal carbides and nitrides submitted to fully controlled thermal treatments varies according to ZrC0.92 ≤ TiC0.96 ≤ TiN0.96; - whatever the investigated material, a self-ion-induced pre-damaging does not modify the initial helium profile extent. The influence of the post-implantation thermal treatment remains preponderant in any case; - the apparent diffusion coefficient of helium is in the range 4 * 10-18 - 2 * 10-17 m2 s-1 in TiC0.96 and 3.5 * 10-19 - 5.3 * 10-18 m2 s-1 in TiN0.96 between 1100 and 1600 C. The

  19. Spin Filtering of Stored (Anti)Protons: from FILTEX to COSY to AD to FAIR

    International Nuclear Information System (INIS)

    We review the theory of spin filtering of stored (anti)protons by multiple passage through the polarized internal target (PIT). Implications for the antiproton polarization buildup in the proposed PAX experiment at FAIR GSI are discussed

  20. Medium-Energy Antiproton Physics with the Antiproton Annihilation Spectrometer (TApAS*) at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Bartoszek, Larry; /Bartoszek Engineering, Aurora; Piacentino, Giovanni M.; /Cassino U.; Phillips, Thomas J.; /Duke U.; Apollinari, Giorgio; Broemmelsiek, Daniel R.; Brown, Charles N.; Christian, David C.; Derwent, Paul; Gollwitzer, Keith; Hahn, Alan; Papadimitriou, Vaia; /Fermilab /INFN, Pisa /Hbar Technologies, West Chicago /Houston U. /IIT, Chicago /IIT, Hyderabad /ITEP /KyungPook National U. /LPI

    2008-01-01

    We propose to assemble a cost-effective, yet powerful, solenoidal magnetic spectrometer for antiproton-annihilation events and use it at the Fermilab Antiproton Accumulator to measure the charm production cross section, study rare hyperon decays, search for hyperon CP asymmetry, and precisely measure the properties of several charmonium and nearby states. Should the charm production cross section be as large as some have proposed, we will also be able to measure D{sup 0}-{bar D}{sup 0} mixing with high precision and discover (or sensitively limit) charm CP violation. The experiment will be carried out by an international collaboration, with installation occurring during the accelerator downtime following the completion of the Tevatron run, and with funding largely from university research grants. The experiment will require some four years of running time. As possibly the sole hadron experiment in progress at Fermilab during that time, it will play an important role in maintaining a broad particle-physics program at Fermilab and in the U.S.

  1. Measurements of the Ratio Between Double and Single Ionization of Helium for Antiprotons

    CERN Multimedia

    2002-01-01

    The inclusive spectra of @p|0's and @h's associated with @*p annihilation at rest are measured. Peaks in these spectra can be identified either with so far not explicitly observed two mesonic final states such as @p|0@w, @p|0@h, @h@h or @p|0@g, or with production of exotic mesonlike states such as baryonium. The apparatus is also suitable for searching for baryonium through some of its particular decay channels. As a by-product we expect information on direct @g production in @*p annihilations at rest.\\\\ \\\\ The apparatus consists of two modular BGO spectrometers and one array of leadglas detectors. The BGO spectrometers are adjustable in angle relative to each other and to the leadglas matrix, thus allowing to cover an angular range from 9|0 to 180|0, corresponding to momenta of zero to more than 1~GeV/c. The apparatus is designed such as to utilize the full potential of LEAR.

  2. 3He NMR studies on helium-pyrrole, helium-indole, and helium-carbazole systems: a new tool for following chemistry of heterocyclic compounds.

    Science.gov (United States)

    Radula-Janik, Klaudia; Kupka, Teobald

    2015-02-01

    The (3)He nuclear magnetic shieldings were calculated for free helium atom and He-pyrrole, He-indole, and He-carbazole complexes. Several levels of theory, including Hartree-Fock (HF), Second-order Møller-Plesset Perturbation Theory (MP2), and Density Functional Theory (DFT) (VSXC, M062X, APFD, BHandHLYP, and mPW1PW91), combined with polarization-consistent pcS-2 and aug-pcS-2 basis sets were employed. Gauge-including atomic orbital (GIAO) calculated (3)He nuclear magnetic shieldings reproduced accurately previously reported theoretical values for helium gas. (3)He nuclear magnetic shieldings and energy changes as result of single helium atom approaching to the five-membered ring of pyrrole, indole, and carbazole were tested. It was observed that (3)He NMR parameters of single helium atom, calculated at various levels of theory (HF, MP2, and DFT) are sensitive to the presence of heteroatomic rings. The helium atom was insensitive to the studied molecules at distances above 5 Å. Our results, obtained with BHandHLYP method, predicted fairly accurately the He-pyrrole plane separation of 3.15 Å (close to 3.24 Å, calculated by MP2) and yielded a sizable (3)He NMR chemical shift (about -1.5 ppm). The changes of calculated nucleus-independent chemical shifts (NICS) with the distance above the rings showed a very similar pattern to helium-3 NMR chemical shift. The ring currents above the five-membered rings were seen by helium magnetic probe to about 5 Å above the ring planes verified by the calculated NICS index. PMID:25228253

  3. Feasibility of an antiproton catalyzed fission fragment rocket

    Science.gov (United States)

    Hidinger, David S.

    1992-03-01

    The purpose of this project was to investigate the feasibility of an antiproton catalyzed fission fragment rocket (FFR). The FFR is characterized by the extraction of fission fragments from the fuel, and the utilization of their kinetic energy for thrust generation. A significant drawback to previous FFR designs was the required critical nuclear pile as the fission fragment source. The author examined the possibility of replacing the critical pile with a sub-critical pile driven by antiprotons. Recent experiments have revealed that antiprotons stimulate highly energetic fissions in 238U, with a neutron multiplicity of 13.7 neutrons per fissions. This interaction was used as a throttled neutron source. The pile consisted of layers of fissile coated fibers which are designed to allow fission fragments to escape them, where the fragments collide with a fluid. The heated fluid is then ejected from the rocket to provide thrust. The calculations performed indicate that each antiproton injected into the pile can stimulate 8 or more fissions while maintaining a neutron multiplication of less than 0.4. Based on the results, the specific design presented was inadequate. Despite this, the concept of using the antiproton-U interaction as a source of thrust warrants further study.

  4. Large amounts of antiproton production by heavy ion collision

    International Nuclear Information System (INIS)

    To produce large amounts of antiprotons, on the order of several grams/year, use of machines to produce nuclear collisions are studied. These can be of either proton-proton, proton-nucleus and nucleus-nucleus in nature. To achieve high luminosity colliding beams, on the order of 1041 m/cm2, a self-colliding machine is required, rather than a conventional circular colliding type. The self-colliding machine can produce additional antiprotons through successive collisions of secondary particles, such as spectator nucleons. A key problem is how to collect the produced antiprotons without capture by beam nuclei in the collision zone. Production costs for anti-matter are projected for various energy source options and technology levels. Dedicated facilities using heavy ion collisions could produce antiproton at substantially less than 1 million $/milligram. With co-production of other valuable products, e.g., nuclear fuel for power reactors, antiproton costs could be reduced to even lower values

  5. Calculated LET spectrum from antiproton beams stopping in water

    CERN Document Server

    Bassler, Niels

    2009-01-01

    Antiprotons have been proposed as a potential modality for radiotherapy because the annihilation at the end of range leads to roughly a doubling of physical dose in the Bragg peak region. So far it has been anticipated that the radiobiology of antiproton beams is similar to that of protons in the entry region of the beam, but very different in the annihilation region, due to the expected high-LET components resulting from the annihilation. On closer inspection we find that calculations of dose averaged LET in the entry region may suggest that the RBE of antiprotons in the plateau region could significantly differ from unity, which seems to warrant closer inspection of the radiobiology in this region. Materials and Methods. Monte Carlo simulations using FLUKA were performed for calculating the entire particle spectrum of a beam of 126 MeV antiprotons hitting a water phantom. Results and Discussion. In the plateau region of the simulated antiproton beam we observe a dose-averaged unrestrict...

  6. A low-energy antiproton detector prototype for AFIS

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Lingxin; Greenwald, Daniel; Hahn, Alexander; Hauptmann, Philipp; Konorov, Igor; Losekamm, Martin; Paul, Stephan; Poeschl, Thomas; Renker, Dieter [Technische Universitaet Muenchen (Germany)

    2014-07-01

    Antiprotons are produced in interactions of primary cosmic rays with earth's exosphere, where a fraction of them will be confined in the geomagnetic field in the inner van Allen Belt. The antiproton-to-proton flux ratio predicted by theory is in good agreement with recent results from the South Atlantic Anomaly (SAA) published by the PAMELA collaboration. We have designed the AFIS (Antiproton Flux in Space) project in order to extend the measurable range of antiprotons towards the low-energy region. In scope of this project a small antiproton detector consisting of scintillating fibers and silicon photomultipliers is being developed as payload for a CubeSat traversing the SAA in Low Earth Orbit. For the proof of concept we have built a prototype called ''CubeZero'' which completed its first test using pion and proton beams at PSI, Switzerland. Our primary goal was to investigate on the performance of tracking and Bragg peak identification in hardware and software. Analysis of detector performance based on data taken during this beam test is presented in this talk.

  7. The Floor's the Limit (Antiproton energies to hit new low)

    CERN Multimedia

    2000-01-01

    Celebrating the success of the RFQ in Aarhus. Left to right: Alessanda Lombardi (CERN), Iouri Bylinskii (CERN), Alex Csete (Aarhus), Ulrik Uggerhøj (Aarhus), Ryu Hayano (Tokyo, spokesman ASACUSA), Helge Knudsen (Aarhus), Werner Pirkl (CERN), Ryan Thompson (Aarhus), Søren P. Møller (Aarhus). Although in particle physics we are accustomed to strive for higher and higher energies, this is not always the most interesting thing to do with antiprotons. Indeed, as recent issues of the Bulletin have suggested, the signpost on the road to a closer look at the antiproton points towards ever-lower energies. The CERN Antiproton Decelerator decelerates antipro-tons emerging from a target placed in the path of a 26 GeV/c proton beam from 90 % of to about 10 % of the speed of light. However, even this is far too fast for many of the most interesting experiments on antiprotons planned by Danish and Japanese members of the ASACUSA collaboration. Tokyo University has therefore financed the con...

  8. Double photoionization of helium with synchrotron x-rays: Proceedings

    International Nuclear Information System (INIS)

    This report contains papers on the following topics: Overview and comparison of photoionization with charged particle impact; The ratio of double to single ionization of helium: the relationship of photon and bare charged particle impact ionization; Double photoionization of helium at high energies; Compton scattering of photons from electrons bound in light elements; Electron ionization and the Compton effect in double ionization of helium; Elimination of two atomic electrons by a single energy photon; Double photoionization of helium at intermediate energies; Double Photoionization: Gauge Dependence, Coulomb Explosion; Single and Double Ionization by high energy photon impact; The effect of Compton Scattering on the double to single ionization ratio in helium; and Double ionization of He by photoionization and Compton scattering. These papers have been cataloged separately for the database

  9. Electron scattering in a helium Debye plasma

    International Nuclear Information System (INIS)

    Graphical abstract: We present our results of the total ionization cross sections for the helium ground state. We see agreement between experiment and the no screening calculations for all projectile energies considered. To date there is no other ab initio theory that is able to achieve such agreement over the entire energy range. The D = 100 results are barely distinguishable from the no screening ones. The D = 10 results are visibly different at the lower energies, but still converge to the other two calculations at the higher energies. Highlights: ► Cross sections for electron scattering off helium in a Debye plasma are presented for excitation and ionization from the ground state. ► The Debye–Huckel potential substantially effects all levels of the helium atom except the ground state. ► Generally, a rather weak dependence of the presented cross sections was found for D = 10. - Abstract: The immense progress in the field of electron–atom scattering, where pure Coulomb potentials are involved, has been translated to collision processes in Debye plasmas. The Debye–Hückel potential is used to describe plasma Coulomb screening effects depending on the temperature and density of the plasma. We provide benchmark results of electron–helium scattering for momentum transfer cross sections, discrete excitation and ionization over a broad range of incident energies and Debye radii.

  10. From LEAR to HESR: past, present and future of meson spectroscopy with antiprotons

    International Nuclear Information System (INIS)

    Meson spectroscopy experiments performed using antiproton beams have carried out a deep and systematic study of all the main open problems of strong interaction in the non-perturbative regime. In this review, I will sketch the major achievements obtained by experiments studying antiproton annihilations at the CERN LEAR machine and at the Fermilab antiproton accumulator. Finally I will illustrate which topics might be addressed, in the next future, by the new antiproton machine (HESR) that will be available at GSI

  11. Antiproton induced DNA damage: proton like in flight, carbon-ion like near rest

    OpenAIRE

    Kavanagh, J. N.; Currell, F. J.; Timson, D.J.; Savage, K. I.; Richard, D J; S.J. McMahon(Particle Physics Department, Rutherford Appleton Laboratory, Didcot, United Kingdom); Hartley, Oliver; Cirrone, G. A. P.; Romano, F.; Prise, K M; Bassler, N.; Holzscheiter, M. H.; Schettino, G

    2013-01-01

    Biological validation of new radiotherapy modalities is essential to understand their therapeutic potential. Antiprotons have been proposed for cancer therapy due to enhanced dose deposition provided by antiproton-nucleon annihilation. We assessed cellular DNA damage and relative biological effectiveness (RBE) of a clinically relevant antiproton beam. Despite a modest LET (,19 keV/mm), antiproton spread out Bragg peak (SOBP) irradiation caused significant residual c-H2AX foci compared to X-ra...

  12. The Descending Helium Balloon

    Science.gov (United States)

    Helseth, Lars Egil

    2014-01-01

    I describe a simple and fascinating experiment wherein helium leaks out of a rubber balloon, thereby causing it to descend. An estimate of the volumetric leakage rate is made by measuring its rate of descent.

  13. Ultra-low energy antiprotons for anti hydrogen spectroscopy and antimatter gravity

    International Nuclear Information System (INIS)

    Approximately one million antiprotons have been captured in a large scale Penning trap at the Low Antiproton Ring (LEAR) at CERN. This has opened new discussions of the possible use of ultra-low energy antiprotons for gravitational physics as well as for precision spectroscopy of anti hydrogen for CPT tests

  14. Helium-Charged Titanium Films Deposited by Pulsed Laser Deposition in an Electron-Cyclotron-Resonance Helium Plasma Environment

    Institute of Scientific and Technical Information of China (English)

    金钦华; 胡佩钢; 凌浩; 吴嘉达; 施立群; 周筑颖

    2003-01-01

    Titanium thin films incorporated with helium are produced by pulsed laser deposition in an electron cyclotron resonance helium plasma environment. Helium is distributed evenly in the film and a relatively high He/Ti atomic ratio (~ 20%) is obtained from the proton backscattering spectroscopy. This high concentration ofhelium leads to a surface blistering which is observed by scanning electron microscopy. Laser repetition rate has little influence on film characters. Substrate bias voltage is also changed for the helium incorporating mechanism study, and this is a helium ion implantation process during the film growth. Choosing suitable substrate bias voltage, one can avoid the damage produced by ion implantation, which is always present in general implantation case.

  15. Status of antiproton accumulation and cooling at Fermilab's Recycler

    International Nuclear Information System (INIS)

    The Recycler ring is an 8 GeV permanent magnet storage ring where antiprotons are accumulated and prepared for Fermilab's Tevatron Collider program. With the goal of maximizing the integrated luminosity delivered to the experiments, storing, cooling and extracting antiprotons with high efficiency has been pursued. Over the past two years, while the average accumulation rate doubled, the Recycler continued to operate at a constant level of performance thanks to changes made to the Recycler Electron Cooler (energy stability and regulation, electron beam optics), RF manipulations and operating procedures. In particular, we discuss the current accumulation cycle in which ∼ 400 x 1010 antiprotons are accumulated and extracted to the Tevatron every ∼15 hours

  16. Strangeness production and hypernucleus formation in antiproton induced reactions

    CERN Document Server

    Feng, Zhao-Qing

    2015-01-01

    Formation mechanism of fragments with strangeness in collisions of antiprotons on nuclei has been investigated within the Lanzhou quantum molecular dynamics (LQMD) transport approach combined with a statistical model (GEMINI) for describing the decays of excited fragments. Production of strange particles in the antiproton induced nuclear reactions is modeled within the LQMD model, in which all possible reaction channels such as elastic scattering, annihilation, charge exchange and inelastic scattering in antibaryon-baryon, baryon-baryon and meson-baryon collisions have been included. A coalescence approach is developed for constructing hyperfragments in phase space after de-excitation of nucleonic fragments. The combined approach could describe the production of fragments in low-energy antiproton induced reactions. Hyperfragments are formed within the narrower rapidities and lower kinetic energies. It has advantage to produce heavier hyperfragments and hypernuclides with strangeness s=-2 (double-$\\Lambda$ fra...

  17. Antiproton-Nucleus Interaction and Coulomb Effect at High Energies

    Institute of Scientific and Technical Information of China (English)

    ZHOU Li-Juan; WU Qing; GU Yun-Ting; MA Wei-Xing; TAN Zhen-Qiang; HU Zhao-Hui

    2005-01-01

    The Coulomb effect in high energy antiproton-nucleus elastic and inelastic scattering from 12C and 16O is studied in the framework of Glauber multiple scattering theory for five kinetic energies ranged from 0.23 to 1.83 GeV.A microscopic shell-model nuclear wave functions, Woods-Saxon single-particle wave functions, and experimental pN amplitudes are used in the calculations. The results show that the Coulomb effect is of paramount importance for filling up the dips of differential cross sections. We claim that the present result for inelastic scattering of antiproton-12C is sufficiently reliable to be a guide for measurements in the very near future. We also believe that antiproton nucleus elastic and inelastic scattering may produce new information on both the nuclear structure and the antinucleon-nucleon interaction, in particular the p-neutron interaction.

  18. Energy and energy width measurement in the FNAL antiproton accumulator

    Energy Technology Data Exchange (ETDEWEB)

    Church, M.; Hsueh, S.; Rapidis, P.; Werkema, S.

    1991-10-01

    The Fermilab Antiproton Accumulator has recently been used to produce Charmonium resonances (charm quark, anti-charm quark bound states) in proton-antiproton annihilations using an internal H{sub 2} gas jet target. A measurement of the resonance mass and width may be obtained from a precise knowledge of the antiproton beam energy and energy spread. The beam energy is measured to an accuracy of 1 part in 10{sup 4} in the range 6.3 Gev to 4.1 Gev by measuring the orbit length and revolution frequency of the beam. The beam momentum spread is measured to an accuracy of 10% by measuring the beam frequency spread and the parameter {eta} = (P{sub beam}/F{sub rev}){center dot}(dF{sub rev}/dP{sub beam}). These two measurement techniques are described in this report.

  19. Investigation of the antiprotonic X-ray spectrum of the lithium isotopes 6Li and 7Li

    International Nuclear Information System (INIS)

    Antiprotons of the low-energy separated anti p-beam K23 at CERN in Geneva have been stopped in thin (0.6 g/cm2) targets of the Lithium isotopes 6Li and 7Li. The characteristic X-rays of the formed antiprotonic atoms were measured with four identical high-resolution Si (Li) detectors. Three lines of the N- series, four lines of the M-series and the 3d-2p transition of the Balmer series were observed. The measured relative intensities of the M- and N-series transitions are well described by the simple cascade model of Eisenberg and Kessler. The 3d-2p transition is considerably influenced by the strong interaction between antiproton and nucleus and thus drastically reduced in intensity. The analysis of this transition yields the shift and width of the 2p level, whereas the width of the 3d level is deduced from intensity considerations. (orig./HSI)

  20. Antiproton-induced fission for space power and propulsion applications

    International Nuclear Information System (INIS)

    The Gasdynamic Mirror[GDM] fusion reactor is investigated for use as a bi-modal propulsion device when driven by antiprotons.The deuterium-tritium[DT] fusion reactions in the device will be initiated by the heating provided by the fission fragments and annihilation products resulting from the 'at rest' annihilation of antiprotons in U-238 target nuclei.The energetic pions and muons of the proton-antiproton[or neutron]annihilation in the U-238 nucleus can heat a DT plasma to several keV during their relatively short lifetimes.The remaining heating to about 10 keV is provided by the fission fragments.Fissioning of U-238 by 'at rest' annihilation of antiprotons has been shown to be 100% efficient,and the process can thus be effectively used in heating a suitable plasma to thermonuclear temperatures.With GDM as a steady state fusion reactor,and assuming certain efficiencies for the various components of the system,we calculate the energy multiplication factor 'Q' needed to sustain the steady-state operation for either the 'propulsive' mode or the 'power-producing' mode.With the aid of a system and mission analyses,we find that approximately 3.5 micrograms of antiprotons are required to accomplish a round mission to Mars in about 59 days.A similar amount is required to initiate and sustain the power-producing mode where gigawatts of electric power may be generated.Although roughly nanograms of antiprotons are currently produced annually,it is expected that hundreds of milligrams or even several grams will be produced annually in the next decade or so when Mars missions may be contemplated

  1. Efficiency of Dopant-Induced Ignition of Helium Nanoplasmas

    CERN Document Server

    Heidenreich, A; Rometsch, M; Krishnan, S R; Stienkemeier, F; Mudrich, M

    2016-01-01

    Helium nanodroplets irradiated by intense near-infrared laser pulses ignite and form highly ionized nanoplasmas even at laser intensities where helium is not directly ionized by the optical field, provided the droplets contain a few dopant atoms. We present a combined theoretical and experimental study of the He nanoplasma ignition dynamics for various dopant species. We find that the efficiency of dopants to ignite a nanoplasma in helium droplets strongly varies and mostly depends on (i) the pick-up process, (ii) the number of free electrons each dopant donates upon ionization, and remarkably, (iii) by the hitherto unexplored effect of the dopant location in or on the droplet.

  2. Studies of helium distribution in metal tritides

    International Nuclear Information System (INIS)

    The distribution of helium (3He) in LiT, TiT2, and UT3, which are regarded as representative metal tritides, was investigated using pulse nuclear magnetic resonance (NMR) techniques. Analyses of the NMR lineshapes and nuclear relaxation times indicate the 3He atoms are trapped in microscopic gas bubbles for each tritide. The effects of concentration and temperature on the 3He distributions were investigated as well

  3. High-energy antiprotons from old supernova remnants

    CERN Document Server

    Blasi, Pasquale

    2009-01-01

    A recently proposed model (arXiv:0903.2794) explains the rise in energy of the positron fraction measured by the PAMELA satellite in terms of hadronic production of positrons in aged supernova remnants, and acceleration therein. Here we present a preliminary calculation of the anti-proton flux produced by the same mechanism. While the model is consistent with present data, a rise of the antiproton to proton ratio is predicted at high energy, which strikingly distinguishes this scenario from other astrophysical explanations of the positron fraction (like pulsars). We briefly discuss important implications for Dark Matter searches via antimatter.

  4. Transverse instability of the antiproton beam in the Recycler Ring

    CERN Document Server

    Prost, L R; Burov, A; Crisp, J; Eddy, N; Hu, M; Shemyakin, A

    2012-01-01

    The brightness of the antiproton beam in Fermilab's 8 GeV Recycler ring is limited by a transverse instability. This instability has occurred during the extraction process to the Tevatron for large stacks of antiprotons even with dampers in operation. This paper describes observed features of the instability, introduces the threshold phase density to characterize the beam stability, and finds the results to be in agreement with a resistive wall instability model. Effective exclusion of the longitudinal tails from Landau damping by decreasing the depth of the RF potential well is observed to lower the threshold density by up to a factor of two.

  5. Transverse instability of the antiproton beam in the Recycler Ring

    Energy Technology Data Exchange (ETDEWEB)

    Prost, L.R.; Bhat, C.M.; Burov, A.; Crisp, J.; Eddy, N.; Hu, M.; Shemyakin, A.; /Fermilab

    2011-03-01

    The brightness of the antiproton beam in Fermilab's 8 GeV Recycler ring is limited by a transverse instability. This instability has occurred during the extraction process to the Tevatron for large stacks of antiprotons even with dampers in operation. This paper describes observed features of the instability, introduces the threshold phase density to characterize the beam stability, and finds the results to be in agreement with a resistive wall instability model. Effective exclusion of the longitudinal tails from Landau damping by decreasing the depth of the RF potential well is observed to lower the threshold density by up to a factor of two.

  6. Relativistic hydrodynamics, heavy ion reactions and antiproton annihilation

    International Nuclear Information System (INIS)

    The application of relativistic hydrodynamics to relativistic heavy ions and antiproton annihilation is summarized. Conditions for validity of hydrodynamics are presented. Theoretical results for inclusive particle spectra, pion production and flow analysis are given for medium energy heavy ions. The two-fluid model is introduced and results presented for reactions from 800 MeV per nucleon to 15 GeV on 15 GeV per nucleon. Temperatures and densities attained in antiproton annihilation are given. Finally, signals which might indicate the presence of a quark-gluon plasma are briefly surveyed

  7. Helium leak and chemical impurities control technology in HTTR

    International Nuclear Information System (INIS)

    Japan Atomic Energy Agency (JAEA) has designed and developed high-temperature gas-cooled reactor (HTGR) hydrogen cogeneration system named gas turbine high-temperature reactor (GTHTR300C) as a commercial HTGR. Helium gas is used as the primary coolant in HTGR. Helium gas is easy to leak, and the primary helium leakage should be controlled tightly from the viewpoint of preventing the release of radioactive materials to the environment. Moreover from the viewpoint of preventing the oxidization of graphite and metallic material, the helium coolant chemistry should be controlled tightly. The primary helium leakage and the helium coolant chemistry during the operation is the major factor in the HTGR for commercialization of HTGR system. This paper shows the design concept and the obtained operational experience on the primary helium leakage control and primary helium impurity control in the high-temperature engineering test reactor (HTTR) of JAEA. Moreover, the future plan to obtain operational experience of these controls for commercialization of HTGR system is shown. (author)

  8. Helium bubbles in UO2

    International Nuclear Information System (INIS)

    A certain part of helium generated in MOX fuel could form additional bubbles in fuel pellets as a result of the combination of radiation defects and high temperature. In the present study, the helium infusion treatments were conducted at high temperature with highly pressurized helium for both polycrystalline UO2 fragments and hyperstoichiometric single crystal UO2+x particles. Annealing tests for polycrystalline UO2 were followed by the helium infusion treatment to evaluate formation of helium bubble. In case of as helium-infused polycrystalline sample, it was confirmed that helium bubbles were formed after slight oxidative annealing at more than 1573K. On the other hand, the cavity observed in as-helium-infused single crystal sample grew up to form a negative crystal. Formation mechanism of helium bubble and negative crystal were discussed. (author)

  9. How to make Raman-inactive helium visible in Raman spectra of tritium-helium gas mixtures

    International Nuclear Information System (INIS)

    Raman spectroscopy, a powerful method for the quantitative compositional analysis of molecular gases, e.g. mixtures of hydrogen isotopologues, is not able to detect monoatomic species like helium. This deficit can be overcome by using radioluminescence emission from helium atoms induced by β-electrons from tritium decay. We present theoretical considerations and combined Raman/radioluminescence spectra. Furthermore, we discuss the linearity of the method together with validation measurements for determining the pressure dependence. Finally, we conclude how this technique can be used for samples of helium with traces of tritium, and vice versa. (authors)

  10. Detection of Negative Charge Carriers in Superfluid Helium Droplets: The Metastable Anions He*– and He2 *–

    OpenAIRE

    Mauracher, Andreas; Daxner, Matthias; Postler, Johannes; Huber, Stefan E.; Denifl, Stephan; Scheier, Paul; Toennies, J. Peter

    2014-01-01

    Helium droplets provide the possibility to study phenomena at the very low temperatures at which quantum mechanical effects are more pronounced and fewer quantum states have significant occupation probabilities. Understanding the migration of either positive or negative charges in liquid helium is essential to comprehend charge-induced processes in molecular systems embedded in helium droplets. Here, we report the resonant formation of excited metastable atomic and molecular helium anions in ...

  11. Helium chemistry in high temperature gas cooled reactors - chemical impurity behaviour in the secondary helium coolant of the HTTR

    International Nuclear Information System (INIS)

    Japan Atomic Energy Agency (JAEA) constructed High Temperature Engineering Test Reactor (HTTR) in order to establish and upgrade the technology basis for the high-temperature gas-cooled reactors (HTGRs) and to develop the technology for high-temperature heat applications. The HTTR attained its maximum reactor-outlet coolant temperature of 950 Degrees C in 2004. The intermediate heat exchanger (IHX), which is a helium-helium heat exchanger and installed to the HTTR primary cooling system, is planned to be utilized for the hydrogen production system in the near future. Secondary coolant helium receives heat from primary helium at the heat exchanger pipes made by high-temperature super alloy Hastelloy XR. The secondary pressurized water cooler, which is a helium-water heat exchanger and installed to the secondary cooling system, will replace to the hydrogen production system. The thermochemical water-splitting IS process is a progressive candidate for the hydrogen production system. Chemistry control is necessary in order to avoid oxidation of core graphite and corrosions of high-temperature material of Hastelloy XR, e.g. carbon deposits, carburising and decarburising. The chemical impurity is reduced and monitored by helium purification system and helium sampling system installed primary and secondary helium cooling system, respectively. This report describes impurity behaviour of secondary coolant during the initial 950 operation of the HTTR

  12. Measurement of cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight in Antarctica

    CERN Document Server

    Abe, K; Haino, S; Hams, T; Hasegawa, M; Horikoshi, A; Kim, K C; Kusumoto, A; Lee, M H; Makida, Y; Matsuda, S; Matsukawa, Y; Mitchell, J W; Nishimura, J; Nozaki, M; Orito, R; Ormes, J F; Sakai, K; Sasaki, M; Seo, E S; Shinoda, R; Streitmatter, R E; Suzuki, J; Tanaka, K; Thakur, N; Yamagami, T; Yamamoto, A; Yoshida, T; Yoshimura, K

    2011-01-01

    The energy spectrum of cosmic-ray antiprotons has been measured in the range 0.17 to 3.5 GeV, based on 7886 antiprotons collected by the BESS-Polar II instrument during a long-duration flight over Antarctica in the solar minimum period of December 2007 through January 2008. The antiproton spectrum measured by BESS-Polar II shows good consistency with secondary antiproton calculations. Cosmologically primary antiprotons have been searched for by comparing the observed and calculated antiproton spectra. The BESS-Polar II result shows no evidence of primary antiprotons originating from the evaporation of PBH.

  13. In situ controlled modification of the helium density in single helium-filled nanobubbles

    International Nuclear Information System (INIS)

    We demonstrate that the helium density and corresponding pressure can be modified in single nano-scale bubbles embedded in semiconductors by using the electron beam of a scanning transmission electron microscope as a multifunctional probe: the measurement probe for imaging and chemical analysis and the irradiation source to modify concomitantly the pressure in a controllable way by fine tuning of the electron beam parameters. The control of the detrapping rate is achieved by varying the experimental conditions. The underlying physical mechanisms are discussed; our experimental observations suggest that the helium detrapping from bubbles could be interpreted in terms of direct ballistic collisions, leading to the ejection of the helium atoms from the bubble

  14. In situ controlled modification of the helium density in single helium-filled nanobubbles

    Energy Technology Data Exchange (ETDEWEB)

    David, M.-L., E-mail: marie-laure.david@univ-poitiers.fr; Pailloux, F. [Institut Pprime, UPR 3346 CNRS-Université de Poitiers, SP2MI, 86962 Futuroscope-Chasseneuil cedex (France); Canadian Centre for Electron Microscopy, Mc Master University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada); Alix, K.; Mauchamp, V.; Pizzagalli, L. [Institut Pprime, UPR 3346 CNRS-Université de Poitiers, SP2MI, 86962 Futuroscope-Chasseneuil cedex (France); Couillard, M.; Botton, G. A. [Canadian Centre for Electron Microscopy, Mc Master University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada); Department of Materials Science and Engineering, Mc Master University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada)

    2014-03-28

    We demonstrate that the helium density and corresponding pressure can be modified in single nano-scale bubbles embedded in semiconductors by using the electron beam of a scanning transmission electron microscope as a multifunctional probe: the measurement probe for imaging and chemical analysis and the irradiation source to modify concomitantly the pressure in a controllable way by fine tuning of the electron beam parameters. The control of the detrapping rate is achieved by varying the experimental conditions. The underlying physical mechanisms are discussed; our experimental observations suggest that the helium detrapping from bubbles could be interpreted in terms of direct ballistic collisions, leading to the ejection of the helium atoms from the bubble.

  15. Thermohydraulics of a horizontal diphasic flow of superfluid helium

    International Nuclear Information System (INIS)

    This study aims at characterizing helium two phase flows, and to identify the dependence of their characteristics on various thermo-hydraulic parameters: vapour velocity, liquid height, vapour density, specificities of superfluidity. Both the engineer and the physicist's points of view are taken into consideration: the first one in terms of optimization of a particular cooling scheme based on a two-phase flow, and these second one in terms of more fundamental atomization-related questions. It has been shown that for velocities around 3 to 4 m/s, the liquid phase that was initially stratified undergoes an atomization through the presence of a drop haze carried by the vapor phase.This happens for superfluid helium as well as for normal helium without main differences on atomization

  16. Relative Biological Effectiveness and Peripheral Damage of Antiproton Annihilation

    CERN Multimedia

    Kavanagh, J N; Kaiser, F; Tegami, S; Schettino, G; Kovacevic, S; Hajdukovic, D; Welsch, C P; Currell, F J; Toelli, H T; Doser, M; Holzscheiter, M; Herrmann, R; Timson, D J; Alsner, J; Landua, R; Knudsen, H; Comor, J; Moller, S P; Beyer, G

    2002-01-01

    The use of ions to deliver radiation to a body for therapeutic purposes has the potential to be significant improvement over the use of low linear energy transfer (LET) radiation because of the improved energy deposition profile and the enhanced biological effects of ions relative to photons. Proton therapy centers exist and are being used to treat patients. In addition, the initial use of heavy ions such as carbon is promising to the point that new treatment facilities are planned. Just as with protons or heavy ions, antiprotons can be used to deliver radiation to the body in a controlled way; however antiprotons will exhibit additional energy deposition due to annihilation of the antiprotons within the body. The slowing down of antiprotons in matter is similar to that of protons except at the very end of the range beyond the Bragg peak. Gray and Kalogeropoulos estimated the additional energy deposited by heavy nuclear fragments within a few millimeters of the annihilation vertex to be approximately 30 MeV (...

  17. Enhancing trappable antiproton populations through deceleration and frictional cooling

    Energy Technology Data Exchange (ETDEWEB)

    Zolotorev, Max; Sessler, Andrew; Penn, Gregory; Wurtele, Jonathan S.; Charman, Andrew E.

    2012-03-20

    CERN currently delivers antiprotons for trapping experiments with the Antiproton Decelerator (AD), which slows the antiprotons down to about 5 MeV.This energy is currently too high for direct trapping, and thick foils are used to slow down the beam to energies which can be trapped.To allow further deceleration to $\\sim 100 \\;\\mbox{keV}$, CERN is initiating the construction of ELENA,consisting of a ring which will combine RF deceleration and electron cooling capabilities. We describe a simple frictionalcooling scheme that can serve to provide significantly improved trapping efficiency, either directly from the AD or first usinga standard deceleration mechanism (induction linac or RFQ). This scheme could be implemented in a short time.The device itself is short in length, uses accessible voltages, and at reasonable cost could serve in the interim beforeELENA becomes operational, or possibly in lieu of ELENA for some experiments. Simple theory and simulations provide a preliminary assessment of theconcept and its strengths and limitations, and highlight important areas for experimental studies, in particular to pin down the level of multiplescattering for low-energy antiprotons. We show that the frictional cooling scheme can provide a similar energy spectrum to that of ELENA,but with higher transverse emittances.

  18. An Advanced Hadron Facility: Prospects and applicability to antiproton production

    International Nuclear Information System (INIS)

    An Advanced Hadron Facility is designed to address physics problems within and beyond the Standard Model. High fluxes of secondary beams are needed for the requisite precision tests and searches for very rare decay modes of mesons and baryons. Such high fluxes at useful secondary energies are readily obtained from high intensity, intermediate energy proton beams, which are also well suited to antiproton production. If the AHF primary proton beam were merely dumped into a beam stop, it would produce on the order of 1019 to 1020 antiprotons per operating year. Current collection techniques are not likely to be capable of absorbing more than one part in 103 of this production. Thus, an AHF provides both the immediate possibility of collecting quantities of antiprotons substantially beyond those available from the LEF discussed at this meeting, and for significant increases in the available antiproton supply upon the development (at an AHF) of more efficient collection methods. The prospects are presently good for the completion of an AHF in the late 1990's

  19. ACOL, CERN'S upgrade of the antiproton accelerator complex

    International Nuclear Information System (INIS)

    At its present best the Antiproton Accumulator (AA) produces 6 x 10/sup 9/ p-bar's/hour. In routine operation this amounts to around 10/sup 11/ p-bar's/day including anadvertent stops of all the systems involved. Post ACOL performance aims at increasing these rates tenfold

  20. Outer casing of the AA antiproton production target

    CERN Multimedia

    1979-01-01

    The first version of the antiproton production target was a tungsten rod, 11 cm long (actually a row of 11 rods, each 1 cm long) and 3 mm in diameter. The rod was embedded in graphite, pressure-seated into an outer casing made of stainless steel. The casing had fins for forced-air cooling.