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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Achieving a large transverse emittance ratio in the Relativistic Heavy Ion Collider: Beam experiments, analytical estimates, and implications for the Electron-Ion Collider

The Electron-Ion Collider (EIC), to be built at Brookhaven National Laboratory, will collide a polarized high-energy electron beam with polarized proton and light ion beams in the center-of-mass energy range of 20–140 GeV, achieving a maximum peak luminosity of up to 1 × 10 34 cm − 2 s − 1 for the proton and electron collisions. To achieve such a high luminosity, the EIC will employ small, flat beams at the interaction point, which requires a transverse emittance ratio of about 11:1. Since 2017, we have carried out a series of beam experiments to test the feasibility of achieving such a large emittance ratio in the Relativistic Heavy Ion Collider (RHIC). Thanks to the existing stochastic cooling and decoupling feedback system in RHIC, we successfully demonstrated a large transverse emittance ratio of 11:1 with gold ion beams in 2023. In this article, we will present more details and data analysis for these experiments, along with analytical estimates and numerical multiparticle simulations, and provide an outlook for future EIC coupling compensation. Published by the American Physical Society 2025

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1973

Ion time-of-flight determinations of doubly to singly ionized mercury ion ratios from a mercury electron bombardment discharge

Doubly to singly charged mercury ion ratios in electron bombardment ion thruster exhaust beams have been determined as functions of bombardment discharge potential, thrust beam current, thrust beam radial position, acceleration-deceleration voltage ratio, and propellant utilization fraction. A mathematical model for two-step ionization processes has been derived, and calculated ion ratios are compared to observed ratios. Production of Hg(++) appears to result primarily from sequential ionization of Hg(+) in the discharge. Experimental and analytical results are presented, and design, construction, and operation features of an electrostatic deflection ion time-of-flight analyzer for the determination of the above-mentioned ratios are reviewed.

Sellen, J. M., Jr.↗
NASA NTRS1974

Ion-molecule reactions and vibrational deactivation of H2/+/ ions in mixtures of hydrogen and helium

Use of ion cyclotron resonance methods to measure the thermal energy rate constants for a number of ion-molecule reactions involving hydrogen and hydrogen-helium mixtures. Assuming that the distribution of initial vibrational states in the H2(+) ion is a near-Franck-Condon distribution, the occurrence of collisional deactivation of vibrationally excited H2(+) ions by He atoms is identified, and an approximate rate constant for the deactivation process and its dependence on vibrational energy are given.

Theard, L. P.↗
NASA NTRS1977

Double-peaked ion spectra in the lobe plasma - Evidence for massive ions

Suprathermal Ion Detector Experiments (SIDE) have suggested the presence of a significant secondary peak in the ion distribution function during geomagnetic active periods when the moon is within the lobe plasma. It is observed that: (1) an increase in the primary peak bulk velocity is reflected in an increase in secondary peak bulk velocity, (2) both spectra are narrow in the instrument-look direction (assumed parallel to the flow) and peak temperatures are usually less than about 10 eV, (3) periods for double peak observations comprise about 10% of the total lobe plasma observation time, (4) assuming that peaks are caused by protons, and without correcting for lunar surface potential, primary peak bulk velocity is between about 70 and 160 km/s, and secondary peak bulk velocity is between about 360 and 840 km/s, and (5) assuming equal flow velocities outside the influence of the lunar surface potential are equal for the ions of the two peaks, and making corrections for this potential, secondary peak ions are consistent with N(+) or O(+), and the ratio of O(+) to proton number densities is usually less than about 2 x 10 to the -3rd.

Hardy, D. A.↗
NASA NTRS1975

Ion-probe studies of artificially implanted ions in lunar samples

The ion microprobe at the Johnson Space Center was used to study depth profiles of artificially implanted ions in lunar samples. Five polished sections of typical mare basalts (12040 and 12018) were irradiated with nine different elements at two energies and the resulting concentrations were measured as a function of depth in the minerals plagioclase, pyroxene, and ilmenite. These preliminary simulation experiments were undertaken to determine whether the ion probe can be used to measure solar-wind-implanted elements on the surface of lunar rock crystals and soil grains and to study mechanisms for the redistribution. The results obtained so far demonstrate that depth profiles can indeed be measured with the ion probe. From estimated exposure times of mature soil grains and selected vug crystals, it appears possible (if difficult) to detect several solar-wind-implanted elements.

Zinner, E.↗
NASA NTRS1979

Heating of ions to superthermal energies in the topside ionosphere by electrostatic ion cyclotron waves

The soft particle spectrometer on the Isis 2 spacecraft occasionally observes fluxes of ions moving upward out of the ionosphere in the vicinity of the auroral oval. These ion fluxes are characterized by a sharp pitch angle distribution usually peaked at an angle somewhat greater than 90 deg, indicative of particles heated to a large transverse temperature in a narrow range below the spacecraft. The observations are interpreted in terms of electrostatic ion cyclotron waves, which heat the ions to superthermal energies transverse to the earth's magnetic field. When the transverse energy increases, the repulsive force of the earth's magnetic field, proportional to the particle magnetic moment, repels the particles away from the earth.

Ungstrup, E.↗
NASA NTRS1981

Diagnostic system design for the Ion Auxiliary Propulsion System /IAPS/ - Flight test of two 8 cm mercury ion thrusters

The experimental design of a Diagnostic Subsystem (DSS) as part of an Ion Auxiliary Propulsion System (IAPS) to be flown on P80-1 spacecraft in May 1983, is discussed. The DSS is composed of several detectors measuring thruster efflux, material deposition and spacecraft potential relative to the local space plasma in the vicinity of two 8 cm mercury ion thrusters. The detectors consist of two QCM units measuring frequency in the range of two to 65 KHz. Nine solar cell arrays have the capability of measuring current and voltage from 0-600 mA and 0-0.9 V. Seven ion collectors can measure ion currents with bias voltages of 0, 25, 55 and 96 V. The potential probe can measure current at 16 different commandible levels varying from one to 5 K microamperes within a voltage range of -25 to 175 V. The analysis of the ground-based data indicates that the hardware is qualified for flight, with the detectors and electronic units having passed all functional and environmental tests. Block diagrams are given and the functional parameters of the different design configurations are described.

Hurst, E. B.↗
NASA NTRS1982

Calculation of composition distribution of ultrafine ion-H2O-H2SO4 clusters using a modified binary ion nucleation theory

Thomson's ion nucleation theory was modified to include the effects of curvature dependence of the microscopic surface tension of field dependent, nonlinear, dielectric properties of the liquid; and of sulfuric acid hydrate formation in binary mixtures of water and sulfuric acid vapors. The modified theory leads to a broadening of the ion cluster spectrum, and shifts it towards larger numbers of H2O and H2SO4 molecules. Whether there is more shifting towards larger numbers of H2O or H2SO4 molecules depends on the relative humidity and relative acidity of the mixture. Usually, a broadening of the spectrum is accompanied by a lowering of the mean cluster intensity. For fixed values of relative humidity and relative acidity, a similar broadening pattern is observed when the temperature is lowered. These features of the modified theory illustrate that a trace of sulfuric acid can facilitate the formation of ultrafine, stable, prenucleation ion clusters as well as the growth of the prenucleation ion clusters towards the critical saddle point conditions, even with low values of relative humidity and relative acidity.

Singh, J. J.↗
NASA NTRS1983

Beam-plasma interactions in a positive ion-negative ion plasma

An electron-free plasma consisting of negative ions /SF6(-)/ and positive ions /Ar(+)/, and negligible neutral-ion collision frequencies has been created in the laboratory. This plasma has a mass ratio of approximately 3.5-similar to many computer particle-in-cell simulated systems. A fluid description of this positive and negative ion confinement (PANIC) plasma is given and compared to experimental measurements of a beam-plasma instability for both beam species and a wide range of beam energies. The fluid dispersion relation and most growing modes are predicted to be insensitive to many parameters of the PANIC beam-plasma system, and found to the consistent with the data.

Intrator, T.↗
NASA NTRS1985

Reversal ion source - A new source of negative ion beams

A new type of ion source utilizing beams of electrons and target molecules, rather than a diffuse, volume plasma, is described. The source utilizes an electrostatic electron 'mirror' which reverses trajectories in an electron beam, producing electrons at their turning point having a distribution of velocities centered at zero velocity. A gas which attaches zero-velocity electrons is introduced at this turning point. Negative ions are produced by an attachment or dissociative attachment process. For many of the thermal electron-attaching molecules the cross sections can be quite large, varying as the inverse square root of the electron energy or just the s-wave threshold law. The efficiency and current density of the ion source for production of Cl(-) through the large, thermal energy attachment process is estimated. It is argued that the source can be used for the production of negative ions through attachment resonances located at higher energies as well.

Orient, O. J.↗
NASA NTRS1985

Thermal ion temperatures from the retarding ion mass spectrometer on DE 1

Data from the retarding ion mass spectrometer (RIMS) on Dynamics Explorer 1 are analyzed by means of a thin sheath model to determine ion temperatures. A number of characteristic features of ion temperatures in and near the plasmasphere are presented. Typical H(+) temperatures in the plasmasphere are found to be 4000 K to 6000 K on the morningside and 2000 K to 4000 K on the eveningside, increasing with L throughout. In the plasma trough, typical temperatures observed are a few times 10,000 K. In the outer plasmasphere, multiple temperature components are frequently observed. H(+) and He(+) ions are found to be very close to thermal equilibrium with each other in all but perhaps the outer part of the plasmasphere. Within the plasmasphere, temperature profiles observed by DE 1/RIMS rarely show small-scale variation. During geomagnetically active times, high-altitude temperatures between L = 2 and 3 appear to be depressed over quiet time values, to the extent that they may be cooler than temperatures at low altitudes along approximately the same field line.

Comfort, R. H.↗
NASA NTRS1984

Effect of metal ions on positron annihilation characteristics in metal ion containing epoxies

In the course of developing improved moisture-resistant epoxy resins, two different types of epoxy resins containing variable mole ratios of chromium ions per polymer repeat unit were developed. Positron annihilation characteristics have been investigated in these resins as a function of their metal ion content. In both cases, the presence of metal ions reduces the lifetime as well as the intensity of the long life component. The long life component intensity reduction is considerably more pronounced than the lifetime reduction. These results have been discussed in terms of increased unpaired electron density at Ps formation sites due to the presence of chromium ions in the matrix.

Singh, J. J.↗
NASA NTRS1985

Evidence for ion heat flux in the light ion polar wind

Cold flowing hydrogen and helium ions have been observed using the retarding ion mass spectrometer on board the Dynamics Explorer 1 spacecraft in the dayside magnetosphere at subauroral latitudes. The ions show a marked flux asymmetry with respect to the relative wind direction. The observed data are fitted by a model of drifting Maxwellian distributions perturbed by a first order-Spritzer-Haerm heat flux distribution function. It is shown that both ion species are supersonic just equatorward of the auroral zone at L = 14, and the shape of asymmetry and direction of the asymmetry are consistent with the presence of an upward heat flux. At L = 6, both species evolve smoothly into warmer subsonic upward flows with downward heat fluxes. In the case of subsonic flows the downward heat flux implies a significant heat source at higher altitudes. Spin curves of the spectrometer count rate versus the spin phase angle are provided.

Biddle, A. P.↗
NASA NTRS1985

Nonresonant interaction of heavy ions with electromagnetic ion cyclotron waves

The motion of a heavy ion in the presence of an intense ultralow-frequency electromagnetic wave propagating along the dc magnetic field is analyzed. Starting from the basic equations of motion and from their associated two invariants, the heavy ion velocity-space trajectories are drawn. It is shown that after a certain time, particles whose initial phase angles are randomly distributed tend to bunch together, provided that the wave intensity b-sub-1 is sufficiently large. The importance of these results for the interpretation of the recently observed acceleration of singly charged He ions in conjunction with the occurrence of large-amplitude ion cyclotron waves in the equatorial magnetosphere is discussed.

Berchem, J.↗
NASA NTRS1985

Electrostatic ion cyclotron waves in a plasma with an ion beam and counterstreaming bulk electrons - Waves in the zero-frequency band

A common feature of the auroral plasma in the region above field-aligned (parallel) potential drops are electrostatic hydrogen cyclotron (EHC) waves. The present paper has the objective to show that wave excitation in the zero-frequency band can occur when the ion beams and the current-carrying bulk electrons counterstream. The instability mechanism involves the Landau interaction of the slow (negative energy) ion-beam-cyclotron waves with the drifting electrons and also with the target (background) ions. Only the latter resonant interaction between the beam and the target ions was considered by Okuda and Nishikawa (1984). In this study, it is shown that an electron drift makes an additional unstable contribution to the waves in the zero-frequency band, including those discussed by Okuda and Nishikawa.

Singh, N.↗
NASA NTRS1985

Ion-acoustic instabilities driven by an ion velocity ring

A ring distribution of ions in velocity space can generate electrostatic waves which propagate predominantly along an ambient magnetic field at frequencies comparable with the ion plasma frequency. A dispersion equation which accounts for these waves is presented, and solved analytically and numerically. It was found that ion-acoustic-like waves are excited in a plasma even if the electron temperature is comparable with the in temperature under the assumption of an anisotropic ion distribution.

Akimoto, K.↗
NASA NTRS1986

Ion-molecule reactions of hydrocarbon ions in C2H2 and HCN

Rate coefficients and product distributions have been determined for reaction of the ions C(x)H(y)+ (x ranging from 1 to 4, and y ranging from 0 to 4) with C2H2 and HCN. The measurements were obtained using the ion cyclotron resonance technique at 298 K. In several reactions an association product was observed at pressures as low as 0.000001 torr, and in these cases stabilization of the intermediate was assumed to be by photon emission. Most of the reaction studied yield ions having a larger carbon skeleton than the reactant ion. These reactions provide routes for building large organic and organonitrogen molecules in combustion zones of unsaturated hydrocarbon flames and in astrochemical environments.

Anicich, V. G.↗