High Recoil Velocity Research Articles

Performance Study of a Permanent-Magnet Eddy Current Damper for Guns Recoil Control

Eddy current damper (ECD) is a promising device for dissipating kinetic energy in dynamic systems, this study is conducted to analyze the dynamic characterization and structural optimization of linear ECD under guns launch load. The recoil resistance of ECD under guns launch load is highly nonlinear at high recoil velocity, and the recoil resistance curve shows an increase-decrease-increasing shape like a “saddle”, which is not conducive to the stability of ECD during operation. The effects of several structural parameters on the dynamic characterization of ECD were studied in details. Results show that the air-gap size, the thickness of the magnetic conduction tube and conductive tube all have a notable influence on the recoil resistance curve of ECD. Moreover, BP neural network and genetic algorithm were used for structural optimization and the optimal value was verified by FEM. The optimization results indicate that the “saddle” shape of optimized recoil resistance curve is basically invisible. The fullness of the recoil resistance curve is significantly improved from 84.93% to 92.1%, which guaranteeing a smooth recoil movement. Finally, an impact loading test system for eddy current damper was built and the experimental results were basically consistent with the simulation results.

Meet the Parents: The Progenitor Binary for the Supermassive Black Hole Candidate in E1821+643

The remnants of binary black hole mergers can be given recoil kick velocities up to 5000 km s−1 due to anisotropic emission of gravitational waves. E1821+643 is a recoiling supermassive black hole candidate with spectroscopically offset, broad emission lines, consistent with motion of the black hole at ∼2100 km s−1 along the line of sight relative to its host galaxy. This suggests a recoil kick of ∼2200 km s−1. Such a kick is powerful enough to eject E1821+643 from its M gal ∼ 2 × 1012 M ⊙ host galaxy. In this work, we address the question: assuming that E1821+643 is a recoiling black hole, what are the likely properties of the progenitor binary that formed E1821+643? Using astrophysically motivated priors, we infer that E1821+643 was likely formed from a binary black hole system with masses of , (90% credible intervals). Given our model, the black holes in this binary were likely to be spinning rapidly with dimensionless spin magnitudes of , . Such a high recoil velocity is impossible for spins aligned to the orbital angular momentum axis. This suggests that the progenitor for E1821+643 merged in hot gas, which is thought to provide an environment where spin alignment from accretion proceeds slowly relative to the merger timescale. We infer that E1821+643, if it is a recoiling black hole, is likely to be a rapidly rotating black hole with a dimensionless spin of χ = 0.92 ± 0.04. A 2.6 × 109 M ⊙ black hole, recoiling from a gas-rich environment at v ∼ 2200 km s−1, is likely to persist as an active galactic nucleus for ∼107 yr, in which time it traverses ∼25 kpc.

Confirming NGC 6231 as the parent cluster of the runaway high-mass X-ray binary HD 153919/4U 1700-37 withGaiaDR2

Context.A significant fraction (10–20%) of the most massive stars move through space with a high (v ≳ 30 km s−1) velocity. One of the possible physical explanations is that a supernova in a compact binary system results in a high recoil velocity of the system. If the system remains bound, it can be subsequently observed as a spectroscopic binary (SB1), a high-mass X-ray binary, a compact binary, and finally a gravitational-wave event.Aims.If such a system is traced back to its parent cluster, binary evolution models can be tested in great detail.Methods.TheGaiaproper motions and parallaxes are used to demonstrate that the high-mass X-ray binary HD 153919/4U 1700-37 originates from NGC 6231, the nucleus of the OB association Sco OB1.Results.The O supergiant and its compact companion, of which the physical nature (a neutron star or a black hole) is unknown, move with a space velocity of 63 ± 5 km s−1with respect to NGC 6231. The kinematical age of the system is 2.2 ± 0.1 Myr. The parallaxes and accurate proper motions inGaiaDR2 were used to perform a membership analysis of NGC 6231; 273 members are identified, of which 268 have good quality photometry. The distance to NGC 6231 is 1.63 ± 0.15 kpc. Isochrone fitting results in an age of 4.7 ± 0.4 Myr and an extinctionAVto the cluster of 1.7 ± 0.1. With the identification of NGC 6231 as the parent cluster, the upper limit on the age of the progenitor of 4U1700-37 at the moment of the supernova explosion is 3.0 ± 0.5 Myr.Conclusions.With these constraints, the evolutionary history of the system can be reconstructed with an initial mass of the progenitor of the compact object > 60M⊙. The high mass, the extreme mass ratio, and short orbital separation of the system make it difficult to produce possible progenitor systems through population synthesis. We propose that the system experienced a Case A mass transfer phase before the supernova, which typically widens a binary. In order to create a progenitor system that does not merge, a lot of angular momentum must be lost from the system during the phase of mass transfer and/or an asymmetry in the supernova explosion provides a kick resulting in the observed orbital parameters. Given its current high space velocity and the derived evolutionary history, the compact object in the system is more likely to have received a large natal kick, which suggests that it is more likely a neutron star than a black hole. HD 153919/4U1700-37 might be a prototype in the Milky Way for the progenitor of gravitational wave events such as GW190412.

Outflow Bubbles from Compact Binary Mergers Embedded in Active Galactic Nuclei: Cavity Formation and the Impact on Electromagnetic Counterparts

Abstract We propose a novel scenario for possible electromagnetic (EM) emission by compact binary mergers in the accretion disks of active galactic nuclei (AGNs). Nuclear star clusters in AGNs are a plausible formation site of compact-stellar binaries (CSBs) whose coalescences can be detected through gravitational waves (GWs). We investigate the accretion onto and outflows from CSBs embedded in AGN disks. We show that these outflows are likely to create outflow cavities in the AGN disks before the binaries merge, which makes EM or neutrino counterparts much less common than would otherwise be expected. We discuss the necessary conditions for detectable EM counterparts to mergers inside the outflow cavities. If the merger remnant black hole experiences a high recoil velocity and can enter the AGN disk, it can accrete gas with a super-Eddington rate, newly forming a cavity-like structure. This bubble can break out of the disk within a day to a week after the merger. Such breakout emission can be bright enough to be detectable by current soft X-ray instruments, such as Swift-XRT and Chandra.

Spin misalignment of black hole binaries from young star clusters: implications for the origin of gravitational waves events

ABSTRACT Recent studies indicate that the progenitors of merging black hole (BH) binaries from young star clusters can undergo a common envelope phase just like isolated binaries. If the stars emerge from the common envelope as naked cores, tidal interactions can efficiently synchronize their spins before they collapse into BHs. Contrary to the isolated case, these binary BHs can also undergo dynamical interactions with other BHs in the cluster before merging. The interactions can tilt the binary orbital plane, leading to spin-orbit misalignment. We estimate the spin properties of merging binary BHs undergoing this scenario by combining up-to-date binary population synthesis and accurate few-body simulations. We show that post-common envelope binary BHs are likely to undergo only a single encounter, due to the high binary recoil velocity and short coalescence times. Adopting conservative limits on the binary–single encounter rates, we obtain a local BH merger rate density of ${\sim } 6.6 {\, \rm yr}^{-1} \, \rm Gpc^{-3}$. Assuming low (≲0.2) natal BH spins, this scenario reproduces the trends in the distributions of effective spin χeff and precession parameters χp inferred from GWTC-2, including the peaks at (χeff, χp) ∼ (0.1, 0.2) and the tail at negative χeff values.

Magnetic moment and lifetime measurements of Coulomb-excited states inCd106

Background: The Cd isotopes are well studied, but experimental data for the rare isotopes are sparse. At energies above the Coulomb barrier, higher states become accessible.Purpose: Remeasure and supplement existing lifetimes and magnetic moments of low-lying states in $^{106}\mathrm{Cd}$.Methods: In an inverse kinematics reaction, a $^{106}\mathrm{Cd}$ beam impinging on a $^{12}\mathrm{C}$ target was used to Coulomb excite the projectiles. The high recoil velocities provide a unique opportunity to measure $g$ factors with the transient-field technique and to determine lifetimes from lineshapes by using the Doppler-shift-attenuation method. Large-scale shell-model calculations were carried out for $^{106}\mathrm{Cd}$.Results: The $g$ factors of the ${2}_{1}^{+}$ and ${4}_{1}^{+}$ states in $^{106}\mathrm{Cd}$ were measured to be $g({2}_{1}^{+})=+0.398(22)$ and $g({4}_{1}^{+})=+0.23(5)$. A lineshape analysis yielded lifetimes in disagreement with published values. The new results are $\ensuremath{\tau}(^{106}\mathrm{Cd};{2}_{1}^{+})=7.0(3)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$ and $\ensuremath{\tau}(^{106}\mathrm{Cd};{4}_{1}^{+})=2.5(2)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$. The mean life $\ensuremath{\tau}(^{106}\mathrm{Cd};{2}_{2}^{+})=0.28(2)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$ was determined from the fully-Doppler-shifted $\ensuremath{\gamma}$ line. Mean lives of $\ensuremath{\tau}(^{106}\mathrm{Cd};{4}_{3}^{+})=1.1(1)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$ and $\ensuremath{\tau}(^{106}\mathrm{Cd};{3}_{1}^{\ensuremath{-}})=0.16(1)\phantom{\rule{4.pt}{0ex}}\mathrm{ps}$ were determined for the first time.Conclusions: The newly measured $g({4}_{1}^{+})$ of $^{106}\mathrm{Cd}$ is found to be only 59% of the $g({2}_{1}^{+})$. This difference cannot be explained by either shell-model or collective-model calculations.

The performance of the Gamma-Ray Energy Tracking In-beam Nuclear Array GRETINA

The Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) is a new generation high-resolution γ-ray spectrometer consisting of electrically segmented high-purity germanium crystals. GRETINA is capable of reconstructing the energy and position of each γ-ray interaction point inside the crystal with high resolution. This enables γ-ray energy tracking which in turn provides an array with large photopeak efficiency, high resolution and good peak-to-total ratio. GRETINA is used for nuclear structure studies with demanding γ-ray detection requirements and it is suitable for experiments with radioactive-ion beams with high recoil velocities. The GRETINA array has a 1π solid angle coverage and constitutes the first stage towards the full 4π array GRETA. We present in this paper the main parts and the performance of the GRETINA system.

Simulations of Recoiling Massive Black Holes

AbstractThe coalescence of black hole binaries is a significant source of gravitational wave radiation. The typically asymmetric nature of this emission, which carries linear momentum, can result in the recoil of the black hole remnant with velocities in the range 100 < Vrecoil < 3750 km s−1. The detectability of recoiling massive black holes (MBH) as off-nuclear QSOs is tightly connected with the properties of the host galaxy, which determine the MBH's orbit and fuel reservoir. We present the results of N-body simulations of recoiling MBHs in high-resolution, non-axisymmetric potentials. We find that if the recoil velocities are high enough to reach regions of the galaxy dominated by the generally triaxial dark matter distribution, the return time is significantly extended when compared to a spherical distribution. We also perform simulations of recoiling MBHs traveling in gas merger remnants, where large amounts of gas have been funneled to the central regions, In this case, the MBHs remain within R<1 kpc from the center of the host even for high recoil velocities (Vrecoil = 1200 km s−1) due to the compactness of the remnant galaxy's nuclear disk. We discuss the implications of both scenarios for detectability.

The Dynamics of the O(1D) + HCl → OH + Cl Reaction at a 0.26 eV Collision Energy: A Comparison between Theory and Experiment

The dynamics of the O((1)D) + HCl(v = 0, j = 0) --> Cl + OH reaction at a 0.26 eV collision energy has been investigated by means of a quasiclassical trajectory (QCT) and statistical quantum and quasiclassical methods. State-resolved cross sections and Cl atom velocity distributions have been calculated on two different potential energy surfaces (PESs): the H2 surface (Martinez et al. Phys. Chem. Chem. Phys. 2000, 2, 589) and the latest surface by Peterson, Bowman, and co-workers (PSB2) (J. Chem. Phys. 2000, 113, 6186). The comparison with recent experimental results reveals that the PSB2 PES manages to describe correctly differential cross sections and the velocity distributions of the departing Cl atom. The calculations on the H2 PES seem to overestimate the OH scattering in the forward direction and the fraction of Cl at high recoil velocities. Although the comparison of the corresponding angular distributions is not bad, significant deviations with a statistical description are found, thus ruling out a complex-forming mechanism as the dominant reaction pathway. However, for the ClO + H product channel, the QCT and statistical predictions are found to be in good agreement.

Magnetic Moment Measurement of Short Lived States via the Doppler Shift Transient Field Method

Magnetic moment measurements of picosecond states generally make use of the huge transient magnetic fields which fast nuclei experience during their passage through a ferromagnetic foil. Based on the Recoil Distance Transient Field (RDTF) method previously pioneered by the Gottingen group, we propose the Doppler Shift Transient Field (DSTF) method to measure g-factors of short-lived high-spin states excited in a heavy ion fusion reaction at a high recoil velocity. This method can be used whenever the state is populated by fast discrete feeder transitions γ2. By measuring the Larmor precession of the decay γ-ray γ1 with a gate set on the Doppler shifted tail of γ2, one selects events of high recoil velocity (= high transient field) and avoids, to a large extent, the uncertainties of delayed side and cascade feedings inherent in heavy-ion fusion reactions. Estimates are given for the DSTF precessions in 102Cd and 74Br.

Fluorine Substitution Effects on the Photodissociation Dynamics of Iodobenzene at 304 nm

The photodissociation dynamics of pentafluoroiodobenzene are investigated by state-selective one-dimensional translation spectroscopy at 304 nm. We have determined the one-dimensional recoil distribution and the spatial distribution in the form of the anisotropy parameter, β, as well as the photodissociation relative yields of both ground-state I(3P3/2) and excited-state I*(2P1/2) iodine photofragments. The results are compared to those observed for iodobenzene at 304 nm. As in iodobenzene, two velocity distributions were observed for the dissociation channel which gives ground-state iodine: a sharp, high recoil velocity peak assigned previously to n,σ* excitation and a slow recoil velocity distribution peak assigned previously to π,π* excitation. Unlike in C6H5I, the I* distribution is relatively strong and its spatial anisotropy can be measured. The fluorine perturbation has led to a number of different observations that can be summarized as follows: (1) The high velocity distribution has a lower average value and much broader width, suggesting more rapid energy redistribution to the fluorinated phenyl ring prior to and during the dissociation process, resulting from stronger coupling between the n,σ* and π,π* states and/or a longer excited-state lifetime; (2) the slow distribution is weaker and has an almost isotropic spatial distribution (the anisotropy parameter β ≈ 1.0), while in the iodobenzene spectrum β is correlated with the recoil velocity; (3) the I* quantum yield for C6F5I is 14 times larger than that for iodobenzene; and (4) β is correlated with the velocity in the I* spectrum found for C6F5I which is not observed for iodobenzene. These observed fluorine perturbations are attributed to an increased mixing between the charge-transfer state (resulting from electron transfer from the iodine nonbonding electrons to the π* orbitals of the fluorinated benzene ring) and both the n,σ* and the ring π,π* states. This leads to two effects: (1) a decrease in the nonbonding electron density on the iodine, which decreases the spin-orbit interaction between the n,σ* states themselves, resulting in a decrease in the curve-crossing probability (thus increasing the I* yield) and (2) an increase in the coupling between the repulsive n,σ* states and the fluorinated phenyl π,π* states, leading to an increase in the rate of energy redistribution.

Fission study for the system84Kr+232Th at 25, 35 and 45 MeV/u

Recoil velocities of heavy residues produced in the bombardment of84Kr beams on a232Th target at energies about the Fermi velocity were determined using the method of correlations between fission fragments. The masses of both fragments were also measured. The data show events with high recoil velocity which are produced in incomplete fusion processes. Estimates of the energy transfer are given. Comparisons with incomplete fusion data obtained with other projectiles in the same incident velocity range show an increase of the energy transfer with the mass of the projectile.

High resolution study of the ν1 vibration of CH3 by coherent Raman photofragment spectroscopy

Coherent anti-Stokes Raman spectroscopy (CARS) was used to measure the vibrational–rotational Q-branch structure of the ν1 symmetric stretch of methyl radicals produced by 266 nm laser photolysis of methyl iodide. Spectra were recorded in both flow cells and free jet expansions at instrumental resolutions ranging from 0.25 to 0.005 cm−1. Due to the high recoil velocity of the CH3 fragment, Doppler and collisional broadening of the transitions is appreciable. Even at the highest resolution such broadening of the transitions leads to interference effects among the closely spaced Raman transitions that influence both the line positions and intensities in the observed CARS spectra. The molecular parameters (cm−1) obtained from the analysis are ν1=3004.42(4), αB1=0.0851(8), αC1=0.0475(7), DN1−DN0=−0.000 046(8), DNK1−DNK0=0.000 083(20), and, with assumptions, DK1−DK0=−0.000 039. These results and infrared data in the literature yield a CH bond length of 1.08378(5) Å for the (1000) state and, with some assumptions, an equilibrium bond length Re of 1.076 Å for this prototypic case of sp2 bonding.

The l-forbidden m1 decay of the 2522 keV level in 39K

The mean lifetime of the first excited 1 2 + level in 39K has been measured to be τ = 93 ± 13 fs by high recoil velocity DSAM. The level was excited by bombarding a 4He-implanted Ta target with a 100 MeV 39K beam. The lifetime was determined by fitting the Doppler-broadened lineshape of the 2522 keV gamma-ray transition to the 3 2 + ground state. Together with the measured B(E2), the B (M1; d 3 2 → S 1 2 ) for this l-forbidden M1 transition was determined to be 0.0100 ±0.0027 μ 2 N . A theoretical calculation, taking into account core polarization, delta excitation and mesonexchange current contributions, underestimates the B( M)1) by more than a factor of six. The experiment also measured the lifetimes of the 3019 keV and 3883 keV levels to be 20 ±4 fs and 11 ± 6 fs, respectively.

G factor of the (59/2(-) isomer in 147Gd.

The /ital g/ factor of the 10 995 keV,/ital J//sup ..pi../=59/2/sup /minus//, and/ital T//sub 1/2/=0.8 ns level in /sup 147/Gd has beendetermined by the transient field method for ions recoiling through amagnetized Gd foil at a temperature of 100 K. The/sup 76/Ge(/sup 76/Ge,5/ital n/)/sup 147/Gd reactionat /ital E/(/sup 76/Ge)=310 MeV was used to provide high recoil velocity. A 100 ps flight time in vacuum between the target and the ferromagnet of 100 ps ensured that the ..gamma..-ray cascades fed the 59/2 level before the recoil ions traversed the Gd foil. The /ital g/ factor was extracted from standard double ratios with the known parametrization of the transient field, yielding /ital g/=0.38(7). This value is in agreement with the predicted wave function and experimental single-particle moments in this mass region. Results for levels in /sup 146,148/Gd were also obtained.

An ion-guide technique for on-line isotope separation coupled with a recoil-type beam separator

The efficiency of an ion-guide isotope separator on-line has been shown to increase to a great extent when only nuclear reaction products of interest are guided into a gas region of the ion-guide system after separating them from beam particles using a gas-filled recoil beam separator. An effective volume to the present ion-guide system is larger than in usual, indicating that this method is very effective in heavy-ion reactions yielding high recoil velocities for reaction products.

Calibration of the transient magnetic field for rare-earth nuclei in iron: Application to g-factors of high spin states in 152, 154Sm

A calibration for the transient magnetic field interaction for rare-earth nuclei recoiling through thin iron has been obtained. Time integral spin rotations for states of known g-factors in 169Tm were measured for the range of velocities, 1.5 ≦ υ/ υ 0 ≦ 6.5. A recent measurement for 156Dy at a very high recoil velocity ( υ/ υ 0 = 10.5) has also been incorporated into the calibration. These data indicate that the field becomes nearly constant with velocity for υ/ υ 0 ≳ 7. For a fixed range of velocity ( υ/ υ 0) in; ( υ/ υ 0) out = 5.0; 2.0. measurements were made on the 4 + states of 156,158,160Gd, 160,162Dy and 174Yb. Arguments are presented to relate the 4 + g-factors to the previously measured 2 + values, so that these data provide an additional calibration of the field over the rare-earth region. By comparing the spin rotation for low- and high-spin states in 152,154Sm, the trend of their g-factors with spin has been derived. We find no strong reduction, at least to spin 10. The 154Sm results are in good agreement with theoretical predictions.

Time-of-flight measurement of the evaporation residues from fusion of 5.9 mev/u 84kr and 27al

Mass and Z-distributions of the evaporation residues from compound-nucleus formation in the reaction 5.9 MeV/u 84Kr on 27Al were measured using a time-of-flight ΔE − E telescope, which is described in detail. The high recoil velocity attained by choosing the heavy reaction partner as projectile made it possible to resolve the reaction products by mass and atomic number. Data were taken in the angular range from 1.5 to 6°. The residue distributions are compared to evaporation calculations assuming the statistical decay by fission and particle evaporation of the compound nucleus 111Mn formed at an excitation energy of 108 MeV with angular momenta up to L CN ≈ 69 h ̵ . The data are consistent with the assumption of statistical equilibrium. Details of the de-excitation process, in particular the fission competition and the influence of nuclear deformations at high angular momenta, are discussed.

Measurement of g-factors in 170Yb, 172Yb and 174Yb by transient field interaction at high recoil velocities

Abstract A beam of 40Ca ions at 168 MeV has been used to Coulomb excite high-spin states in 169Tm and 170, 172, 174Yb which recoiled through thin polarized iron at ν/c ≈ 3.5%. An enhanced transient field ≈ 6 times larger than the Lindhard-Winther prediction was observed and calibrated against the known g-factors in 169Tm. Individual g-factors could not be extracted because of strong feeding; nevertheless, deviations from rotational behaviour (constant g-factors) would be detectable. Empirical fits to microscopic calculations of the rotational g-factors below spin 12+ suggest that if deviations from the simple rotational formula occur, they should be of the form g(J) = g0(1 + αJ2). We find the following values in 170, 172, 174Yb: α × 103 = −0.5±1.5, +1.0±1.5. The uncertainties are the level at which deviations from rotational behaviour are expected to occur. The results are discussed in terms of Coriolis anti-pairing effects.

The g-factors of excited states in 205,203Tl measured by transient field interaction at high recoil velocities

Following Coulomb excitation with 120 MeV 40 Ca and 190 MeV 81 Br beams, fast Pt recoils were passed through thin, polarized Fe foils; the observed Larmor precession angles were used to calibrate the transient magnetic field against the known g -factor for the 2 + state in 194 Pt. Precession data obtained with the 40 Ca beam for the two lowest excited states in Tl isotopes yielded the following g -factors: g( 205 Tl , 5 2 + ) = 0.89±0.26 ; g( 205 Tl , 3 2 + ) = 0.01±0.08 ; g( 203 Tl , 5 2 + ) = 1.03±0.43 ; g( 203 Tl , 3 2 + ) = −0.01±0.11 . The observed g -factors are much smaller than expected for the equivalent states in the one-proton-hole nucleus 207 Tl, underscoring the importance of particle-core coupling effects.