Forward Angles Research Articles

Measurement of the U235(n,f) prompt fission neutron spectrum from 10 keV to 10 MeV induced by neutrons of energy from 1 MeV to 20 MeV

The characterization of fission-driven nuclear systems primarily relies on calculations of neutron-induced chain reactions, and these calculations require evaluated nuclear data as input. Calculation accuracy heavily depends on input nuclear data evaluation accuracy, and thus high precision on the experimental input to the nuclear data evaluation is essential for fundamental quantities like the energy spectrum of neutrons emitted from neutron-induced fission (i.e., the prompt fission neutron spectrum, PFNS). Despite decades of measurement efforts, prior to the measurements described in this work there were only three literature data sets for the $^{235}\mathrm{U}(n,f)$ PFNS at incident neutron energies above 1.0 MeV considered reliable for inclusion in nuclear data evaluations and no reliable data sets above 3.0 MeV incident neutron energy. In this work we report on new measurements of the $^{235}\mathrm{U}(n,f)$ PFNS spanning a grid of 1.0--20.0 MeV in incident neutron energy and 0.01--10.0 MeV in outgoing (PFNS) neutron energy. These measurements were carried out at the Weapons Neutron Research facility at the Los Alamos Neutron Science Center and used a multifoil parallel-plate avalanche counter target with both a Li-glass and a liquid scintillator detector array in separate experiments to span the quoted outgoing neutron energy ranges. The PFNS results are shown in terms of the energy spectra themselves as well as the average PFNS energy ($\ensuremath{\langle}E\ensuremath{\rangle}$) and ratios of $\ensuremath{\langle}E\ensuremath{\rangle}$ at forward and backward angles. The results are compared with literature data and selected nuclear data evaluations. Generally, the data agree with the ENDF/B-VIII.0 evaluation below 5.0-MeV incident neutron energy and more closely with the JEFF-3.3 evaluation above 5.0 MeV, though no evaluations considered for comparison in this work agree with the data across all of the incident and outgoing neutron energies shown, especially in regions where the third-chance fission process becomes available. Additionally, we show a ratio of the present PFNS results for $^{235}\mathrm{U}(n,f)$ with a recent and highly correlated experiment to measure the $^{239}\mathrm{Pu}(n,f)$ PFNS at the same experimental facility and with nearly identical equipment and analysis procedures. Many observations reported in this work are the first of their kind and represent significant advancements for knowledge of the $^{235}\mathrm{U}(n,f)$ PFNS.

New Measurements of the Beam-Normal Single Spin Asymmetry in Elastic Electron Scattering over a Range of Spin-0 Nuclei.

We report precision determinations of the beam-normal single spin asymmetries (A_{n}) in the elastic scattering of 0.95 and 2.18GeV electrons off ^{12}C, ^{40}Ca, ^{48}Ca, and ^{208}Pb at very forward angles where the most detailed theoretical calculations have been performed. The first measurements of A_{n} for ^{40}Ca and ^{48}Ca are found to be similar to that of ^{12}C, consistent with expectations and thus demonstrating the validity of theoretical calculations for nuclei with Z≤20. We also report A_{n} for ^{208}Pb at two new momentum transfers (Q^{2}) extending the previous measurement. Our new data confirm the surprising result previously reported, with all three data points showing significant disagreement with the results from the Z≤20 nuclei. These data confirm our basic understanding of the underlying dynamics that govern A_{n} for nuclei containing ≲50 nucleons, but point to the need for further investigation to understand the unusual A_{n} behavior discovered for scattering off ^{208}Pb.

Neutron elastic and inelastic scattering differential cross sections on carbon

Elastic and inelastic neutron scattering angular distributions were measured on natural carbon samples to confirm existing experimental data and evaluations in the fast neutron region and to guide improvements in resonance parameters, where needed. Sixty-four (n,n′) differential cross section measurements were performed at 45 incident neutron energies between 0.5 and 8.0 MeV.Experimental angle-integrated elastic scattering cross sections are consistent with ENDF/B-VIII.0 values with the exception of the region from 3.2 to 4.0 MeV where our results are ∼3% higher. In the 3.4 to 3.6 MeV region our differential cross sections are slightly lower at forward angles and somewhat higher at backward angles than the ENDF/B-VIII.0 calculations; however, our results are consistent with measured data from other research groups. The first- through fourth-order elastic scattering Legendre coefficients from fits to these experimental data are consistent with ENDF/B-VIII.0 values across this range of incident neutron energies.Inelastic scattering cross sections were measured at 12 incident neutron energies between 5.6 and 7.8 MeV. Angle-integrated cross sections agree well with the 1978 Perey and ENDF/B-VIII.0 values; however, the angular-distribution shapes deviate somewhat from the ENDF/B-VIII.0 calculations. These data will allow refinement of the resonance parameter description in this difficult energy region.

Multi-Objective Optimization Study on Ligament Characteristics of Neck Finite Element Model

<div class="section abstract"><div class="htmlview paragraph">This paper proposes a new method to improve the fit between the neck finite element calculation results and the experimental data through multi-objective optimization of cervical ligament parameters. By refining a previously established finite element model of the neck and improving the fineness of vertebrae and other structures, a new finite element model of the neck was established. The new model adopts the same material property parameters as the previous model. We performed many simulation calculations, each time only one ligament in the model was removed, leaving other structures unchanged. By observing the changes in the angle of the neck joints in the neck torsion experiment of the model before and after the ligament was removed, the influence of the ligament on the model was obtained. The six ligaments with the largest contribution are selected, and their laxity is optimized for multi-objective research, and the optimal solution for the laxity of the selected ligaments is obtained. The optimized ligament relaxation parameters are applied to the neck model to verify the effectiveness of the Panjabi’s experiment. The calculated joint angle is in good agreement with the experimental data. Furthermore, using the forward flexion and extension motion angles of Nightingale et al. 2007 model to simulate and verify the present model, the calculated value is basically consistent with the experimental value. In order to further verify the effectiveness of the established neck model, the head and neck drop experiment, the front collision and rear collision experiment of the volunteer trolley were used for simulation verification. The results show that the calculated values of head centroid displacement, acceleration, and head rotation angle fit well with the experimental values.</div></div>

K+Σ− photoproduction within an isobar model

We used an isobar model to study the K+Σ− photoproduction reaction on a neutron target with focus on the resonance region. In order to achieve a reasonable agreement with the data, we included spin-3/2 and spin-5/2 nucleon resonances in a consistent formalism together with a Δ resonance and two kaon resonances on top of the Born terms. The free parameters of the model were adjusted to the data from the CLAS and LEPS Collaborations on differential cross sections and photon beam asymmetry. The cornerstone of this analysis was an upgrade of the fitting method. Previously, we used only the plain χ2 minimization, which could not prevent us from overfitting the data. We, therefore, introduced a regularization method, the least absolute selection shrinkage operator (LASSO), which, together with information criteria, restricts the number of nonzero parameters and prevents us from overfitting the data. In our analysis, we arrived at two models, fit M, whose parameters were fitted with the MINUIT code only, and fit L, where we used the more advanced LASSO. Both models describe the data in a similar way and we observe only slight differences in the dσ/dΩ data description at very forward angles where the fit M is flat whereas the fit L produces two broad peaks, and in the photon beam asymmetries above 2 GeV at backward kaon angles where the fit M produces a bump. Surprisingly, no hyperon resonances are needed for the correct data description in these models. On the other hand, the N(1720)3/2+ nucleon resonance was found to be very important in both models.

Ageing studies of Multi-Strip Multi-Gap Resistive Plate Counters based on low resistivity glass electrodes in high irradiation dose

Detailed tests and analysis of ageing effects of high irradiation dose on Multi-Strip Multi-Gap Resistive Plate Counters (MSMGRPC) based on low resistivity glass electrodes, foreseen to be used for the most forward polar angles covered by the Time-of Flight (ToF) sub-detector of the Compressed Baryonic Matter (CBM) experiment at Facility for Antiprotons and Ion Research (FAIR) — Darmstadt are reported. The tests were performed at a multi-purpose irradiation facility of IFIN-HH based on 60Co source. MSMGRPC efficiency, cluster size, surface and volume resistivity of the glass electrodes after irradiation are measured and compared with their values before irradiation. The results of a comprehensive analysis of the composition and properties of the deposited layers on the glass electrodes, based on different methods, i.e. Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscopy (XPS), foil Elastic Recoil Detection Analysis (ERDA), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Terahertz Time Domain Spectroscopy (THz-TDS), are presented.

Building Out the Edges: Reading Racial Capitalism Into Jean Anyon’s Political Economy of Urban Education

Background/Context: For over three decades, Jean Anyon produced scholarship that revealed the deep-structural causes of educational inequality. Anyon’s work in political economy includes a racial analytic; she argues that access to education does not reduce economic disparities in urban communities of color, and that schools in poor and working-class communities of color in particular often serve to reproduce inequality across generations. It is common, however, for critical scholars analyzing educational inequality to be steeped in either Marxism or critical race theory, and less knowledgeable about the other. As a result, analyses rarely place equal emphasis on both theoretical frames or synthesize race and class. Using theories of racial capitalism to extend Anyon’s political economic analysis, we contend, brings forward conceptual tools and angles that capture the material and ideological work being done by current, highly racialized neoliberal restructuring in and beyond the school walls. Purpose/Objective/Research Question/Focus of Study: We focus on the ways race operates as a material force that is part and parcel of the capitalist dynamics that create and require inequality, and argue that racial violence structures capitalist development, making the systematic impoverishment of urban schools and neighborhoods possible and permissible. First, we provide an overview of two key theories of racial capitalism from Cedric Robinson and Jodi Melamed. We then revisit Anyon’s work on school knowledge and the hidden curriculum to consider how these operate as forms of epistemic and psychic racial violence that (re)produce racial capitalist conditions. Next, we consider Anyon’s work on political economy and public policy in light of the ways neoliberal racial capitalism links the production of differential human value to capitalist development in urban neighborhoods, deploying public policies that limit the life chances of working class and poor youth of color. Finally, we consider the implications of these dynamics for the “radical possibilities” that inhere in urban schools, arguing that opposition to racial capitalism stretches Anyon’s formulation of the “radical” and the “possible,” as youth oppose racial capitalism by resisting the school itself. Research Design: In this theoretical article, we use theories of racial capitalism to analyze Anyon’s major works in urban education. Putting core concepts from these theories into conversation with Anyon’s findings and her own theorizations, we offer an analytical synthesis that braids together race and class to unpack the production of urban educational inequality. Conclusions/Recommendations: We propose that reading racial capitalism into Anyon’s work can extend her political economic analysis, and through such extension, her findings, analyses, and arguments can be leveraged to help us better understand how race and racism interlock with the ideologies, social structures, and chaos of capitalist development and neoliberal reform. We contend that such an analysis can build out both the “radical” and the “possible” with implications for how we think about opposition and organizing not just within but against schools.

Measurement of the double charge exchange reaction for the 20Ne + 130Te system at 306 MeV

The 130Te(20Ne,20O)130Xe double charge exchange reaction was measured for the first time at very forward angles with the MAGNEX magnetic spectrometer at INFN-LNS. The study, performed at beam energy of 306 MeV, is part of a systematic exploration promoted by the NUMEN project. The last aims to measure specific reaction cross sections to provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double beta decay.

Measurement of deeply virtual Compton scattering off He4 with the CEBAF Large Acceptance Spectrometer at Jefferson Lab

We report on the measurement of the beam spin asymmetry in the deeply virtual Compton scattering off $^4$He using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 6 GeV longitudinally polarized electron beam incident on a pressurized $^4$He gaseous target. We detail the method used to ensure the exclusivity of the measured reactions, in particular the upgrade of CLAS with a radial time projection chamber to detect the low-energy recoiling $^4$He nuclei and an inner calorimeter to extend the photon detection acceptance at forward angles. Our results confirm the theoretically predicted enhancement of the coherent ($e^4$He$~\to~e'$$^4$He$'\gamma'$) beam spin asymmetries compared to those observed on the free proton, while the incoherent ($e^4$He$~\to~e'$p$'\gamma'$X$'$) asymmetries exhibit a 30$\%$ suppression. From the coherent data, we were able to extract, in a model-independent way, the real and imaginary parts of the only $^4$He Compton form factor, $\cal H_A$, leading the way toward 3D imaging of the partonic structure of nuclei.

Search for $\alpha$ condensed states in $^{13}$C using $\alpha$ inelastic scattering

AbstractWe searched for the $\alpha$ condensed state in $^{13}$C by measuring the $\alpha$ inelastic scattering at $E_\alpha = 388$ MeV at forward angles including 0$^\circ$. We performed a distorted-wave Born approximation calculation with the single-folding potential and multipole decomposition analysis to determine the isoscalar transition strengths in $^{13}$C. We found a bump structure around $E_x = 12.5$ MeV due to the isoscalar monopole ($IS0$) transition. A peak-fit analysis suggested that this bump consisted of several $1/2^-$ states. We propose that this bump is due to the mirror state of the 13.5 MeV state in $^{13}$N, which dominantly decays to the $\alpha$ condensed state in $^{12}$C. It was speculated that the $1/2^-$ states around $E_x = 12.5$ MeV were candidates for the $\alpha$ condensed state, but the $3\alpha + n$ orthogonality condition model suggests that the $\alpha$ condensed state is unlikely to emerge as the negative parity states. We also found two $1/2^+$ or $3/2^+$ states at $E_x = 14.5$ and 16.1 MeV excited with the isoscalar dipole ($IS1$) strengths. We suggest that the 16.1 MeV state is a possible candidate for the $\alpha$ condensed state predicted by the cluster model calculations on the basis of the good correspondence between the experimental and calculated level structures. However, the theoretical $IS1$ transition strength for this state is significantly smaller than the measured value. Further experimental information is strongly desired to establish the $\alpha$ condensed state in $^{13}$C.

Observation of a cusp-like structure in the γp → K+Σ0 cross section at forward angles and low momentum transfer

The γp→K+Σ0 differential cross section at extremely forward angles was measured at the BGOOD experiment. A three-quarter drop in strength over a narrow range in energy and a strong dependence on the polar angle of the K+ in the centre-of-mass of the reaction is observed at a centre-of-mass energy of 1900 MeV. Residing close to multiple open and hidden strangeness thresholds, the structure appears consistent with meson-baryon threshold effects which may contribute to the reaction mechanism.

Quenching of Isovector and Isoscalar Spin-M1 Excitation Strengths in N = Z Nuclei

Spin-M1 excitations of nuclei are important for describing neutrino reactions in supernovae or in neutrino detectors since they are allowed transitions mediated by neutral current neutrino interactions. The spin-M1 excitation strength distributions in self-conjugate N=Z nuclei were studied by proton inelastic scattering at forward angles for each of isovector and isoscalar excitations as reported in H. Matsubara et al., Phys. Rev. Lett. 115, 102501 (2015). The experiment was carried out at the Research Center for Nuclear Physics, Osaka University, employing a proton beam at 295 MeV and the high-resolution spectrometer Grand Raiden. The measured cross-section of each excited state was converted to the squared nuclear matrix elements of spin-M1 transitions by applying a unit cross-section method. Comparison with predictions by a shell-model has revealed that isoscalar spin-M1 strengths are not quenched from the prediction although isovector spin-M1 strengths are quenched similarly with Gamow-Teller strengths in charged-current reactions. This finding hints at an important origin of the quenching of the strength relevant to neutrino scattering, that is, the proton-neutron spin-spin correlation in the ground state of the target nucleus. In this manuscript we present the details of the unit cross-section method used in the data analysis and discuss the consistency between the quenching of the isoscalar magnetic moments and that of the isoscalar spin-M1 strengths.

Analysis of effect of bentleg opener geometry on performance in cohesive soil using the discrete element method

Bentleg furrow openers can significantly reduce soil disturbance and reaction forces relative to conventional narrow point openers used in no-tillage farming. The effect of bentleg opener geometry on soil disturbance and reaction forces in a cohesive soil was assessed in a virtual soil bin using the discrete element method. Soil disturbance and reaction forces at an operating depth and a speed of 100 mm and 8 km h −1 , were shown to be minimised by using (1) a shank lateral offset of 70 mm, (2) a side leg bend angle that ensures the elbow, which is the transition between the side leg and vertical shank, is not located below the soil surface, (3) an arched instead of angled elbow, (4) a cutting edge chamfer angle as low as practical, and (5) tine thickness as small as practical. Furrow size was found to be more dependent on shank lateral offset and side leg bend angle than side leg forward angle. Though side leg forward angles >90° reduce particle displacement and will work better in fields with stones and roots, they also considerably increase draught and penetration resistance. A low rake angled foot minimises soil reaction forces and drives soil loosening. Reducing foot height and interaction of the vertical shank with soil particles minimises surface soil displacement. These results have expanded the understanding of bentleg opener mechanics and are in close agreement with those reported for sandy soils. Therefore, similar criteria can be followed to optimise bentleg opener design for different soil types. • Discrete element method predicted bentleg opener geometry effects in Black Vertosol. • Geometries that cause minimum soil disturbance and reaction forces were identified. • Shank lateral offset should be large and arched elbow protrude above soil surface. • Cutting edge chamfer angle and thickness as small as practical are recommended. • Low foot rake angle and foot height reduce soil forces and soil throw, respectively.

Contribution to inclusive (p,α) reactions from (p,pα) knockout at incident energies near 100 MeV

Background: The extent to which knockout, as opposed to a pickup reaction mechanism, contributes in pre-equilibrium $(p,\ensuremath{\alpha})$ reactions is still not clear. Even with exclusive $(p,\ensuremath{\alpha})$ reactions at conveniently low incident energies to well-defined final states, the issue often appears to be ambiguous. Recently Uozumi et al. [Y. Uozumi, Y. Fukuda, Y. Yamaguchi, G. Watanabe, and M. Nakano, Phys. Rev. C 102, 014604 (2020)] used the intranuclear cascade (INC) theory to study pre-equilibrium $(p,\ensuremath{\alpha})$ reactions in a range of incident energies from 42 to 300 MeV. They conclude that, below a projectile energy of about 120 MeV, knockout contributes almost nothing to the upper half of the pre-equilibrium $(p,\ensuremath{\alpha})$ yield. This result is in disagreement with several other studies.Purpose: We investigate whether existing $(p,p\ensuremath{\alpha})$ quasifree knockout results support the conclusion from the INC study.Method: The distorted-wave impulse approximation (DWIA) is used. The theory is known to give a good reproduction of experimental energy distributions and angular distributions, as well as absolute cross sections of $(p,p\ensuremath{\alpha})$ reactions at incident energies at and above 100 MeV. The DWIA is simply exploited as a convenient way of interpolation and extrapolation of the available experimental distributions.Results: The experimental cross-section distributions of the coincidence knockout reactions predict contributions to the pre-equilibrium yield much higher than those estimated by the INC study. At small scattering angles of only ${30}^{\ensuremath{\circ}}$ to ${40}^{\ensuremath{\circ}}$ the knockout yield is already quite substantial. At ${60}^{\ensuremath{\circ}}$ it accounts for approximately all of the pre-equilibrium yield.Conclusions: Even a lower-limit estimate of the coincident contribution at forward angles to the cross section of pre-equilibrium reactions is already sizable at low excitation. The cross section is expected to increase very rapidly at higher excitation energies (equivalently, lower $\ensuremath{\alpha}$-particle energy).

Velocity and concentration field measurements and large eddy simulation of a shaped film cooling hole

The 3D velocity and scalar concentration fields from a laidback fan-shaped film cooling hole are measured using Magnetic Resonance Velocimetry (MRV) and Magnetic Resonance Concentration (MRC). The velocity and scalar concentration fields of the same geometry are also obtained using Large Eddy Simulation (LES). The geometry under consideration features a single film cooling hole with a 30° inclination angle and 7° forward and lateral expansion angles. The results are compared to an existing adiabatic effectiveness experiment using infrared imaging of an identical geometry (Schroeder and Thole, 2014). Flow separation is observed inside the hole in the LES and MRV. The separated region in the LES is symmetrically located, but it is offset to a lateral side in the MRV which slightly skews the scalar concentration field to one side. Comparisons of the LES with the MRV and MRC experiments show good agreement in the velocity and scalar concentration field elsewhere throughout the 3D domain. Despite some disagreement in the adiabatic effectiveness values with the IR experiment immediately after injection, there is good agreement downstream of injection between the IR experiment and the LES and MRC. Differences in the concentration field can be attributed to differences in the in–hole velocity field. The results suggest that the mean position of the region of separation inside the hole is geometrically sensitive.

Clinical Study of Qingpeng Ointment Treating Shoulder-hand Syndrome After Cerebral Hemorrhage During the Rehabilitation Period.

Shoulder-hand syndrome (SHS) refers to a syndrome causing sudden edema, shoulder pain and limited hand function. Qingpeng ointment, a kind of Tibetan medicine, can reduce swelling, relieve pain, tonify stagnation and clear the meridians, which is consistent with the pathological mechanism of SHS after stroke. Therefore, if clinical trials can be used to explore the effectiveness of Qingpeng ointment for the treatment of poststroke SHS and promote its application in clinical medicine, it may prove the specific significance for the treatment of poststroke SHS poststroke SHS. The aim of the study was to investigate the clinical efficacy and safety of Qingpeng ointment in the treatment of poststroke SHS and to provide an objective basis for a better therapeutic treatment for poststroke SHS. A prospective, randomized, controlled study was conducted. This study recruited 120 patients with poststroke SHS who met the inclusion criteria. They were randomized into the treatment group and the control group, with 60 patients allocated to each group. The treatment group received routine medical treatment and rehabilitative care after using the Qingpeng ointment, while the patients in the control group received only routine treatment without the ointment. All patients received clinical assessment with the Visual Analogue Scale (VAS), measurement of the range of motion (ROM) of the upper-limb joints, the Fugl-Meyer Assessment of Upper Extremity (FMA-U) and the Modified Barthel Index Score (MBI) before and after the whole treatment. After 4 weeks of treatment, the VAS scores of both the groups decreased significantly (P ＜0.05), and the difference between the two groups was statistically significant (P < 0.05). No statistical significance was observed for the difference between the treatment group and control group in terms of the FMA-U and MBI scores and the forward bend, backward, outstretch, external rotation and pronation angles after treatment. The increases in the values of VAS, FMA-M and MBI in the treatment group were greater than those in the control group, and the difference was statistically significant (P < 0.05). The increases in the values of the forward bend, outreach and external rotation angles in the treatment group were greater than those in the control group, and the difference was statistically significant (P < 0.05). The treatment group showed better results than the control group in terms of the relief of pain symptoms, the improvement of motor function and the improvement of the activities of daily living for patients with shoulder-hand syndrome after cerebral hemorrhage. Qingpeng ointment was found to be effective and safe for treating poststroke SHS.

New insights into sub-barrier fusion of 28Si + 100Mo

Fusion cross sections of the 28Si + 100Mo system have been measured near and below the Coulomb barrier by detecting the evaporation residues at forward angles. The excitation function has an overall smoother trend than what obtained in a previous experiment, and a large discrepancy is found for the lowest-energy region, where we observe a tendency of the S factor to develop a maximum, which would be a clear indication of hindrance. The results have been compared with the theoretical prediction of coupled-channels calculations using a Woods–Saxon nuclear potential, and including the low-energy excitation modes of both nuclei. Good agreement with data is found by including, in the coupling scheme, the three lowest members of the ground state rotational band of the oblate deformed 28Si, and two-phonons of the strong quadrupole vibration of 100Mo. The additional coupling, in a schematic way, of the two-neutron pick-up between ground states (Q-value = +4.86 MeV) has a minor effect on calculated cross sections, and does not essentially improve the data fit. The excitation function of 28Si + 100Mo has been compared with that of (1) the heavier system 60Ni + 100Mo having analogous features, and (2) several near-by 28Si, 32S + Zr, Mo systems with various nuclear structures and transfer Q-values. The role of quadrupole and octupole excitation modes, as well as of transfer channels, in affecting the fusion dynamics, are clarified to some extent. Systematic measurements of fusion barrier distributions and CC calculations properly including transfer couplings, are necessary, in order to shed full light on the influence of the various coupled channels on the fusion cross sections.

Shape Optimization of Labyrinth Seals to Improve Sealing Performance

To reduce gas leakage, shape optimization of a straight labyrinth seal was carried out. The six design parameters included seal clearance, fin width, fin height, fin pitch, fin backward, and forward expansion angle. The CFD (Computational Fluid Dynamics) model was solved to generate the training and testing samples for the surrogate model, which was established by the least square support vector machine. A kind of chaotic optimization algorithm was used to determine the optimal design parameters of the labyrinth seal. As seal clearance, fin width, fin height, fin pitch, fin backward and forward expansion angles are 0.2 mm, 0.1 mm, 7 mm, 9 mm, 0°, and 15°, the discharge coefficient can reach its minimum value in the design space. The chaotic optimization algorithm coupled with least square support vector machine is a promising scheme for labyrinth seal optimization.

Enhanced α-particle production from fusion evaporation reactions leading to 46Ti

In this paper, we report a detailed study on the de-excitation of the 46Ti compound nucleus populated by means of four different reactions: 16O + 30Si at 7 and 8 AMeV, 18O + 28Si at 7 AMeV and 19F + 27Al at 7 AMeV. The GARFIELD detection array was used to measure the light charged particles and the heavy fragments emitted. This setup covers a large fraction of the solid angle with high-granularity. Complete events are chosen through total charge (Z TOT = 22) detection. Fusion-evaporation events are selected based on the condition that only one heavy fragment is detected in coincidence with the light charged particles. The analysis of global observables, such as charge distribution and light charged particle multiplicities, is compatible with the formation of a thermalized compound nucleus for all the four reactions. Nevertheless, an enhanced emission of α-particles with respect to a pure statistical picture is observed at very forward angles (<20°). This enhancement is mainly visible in the even-Z residue exit channels populated through the emission of only α-particles.

K^{+}Lambda photoproduction at forward angles and low momentum transfer

gamma p rightarrow K^{+} Lambda differential cross sections and recoil polarisation data from threshold for extremely forward angles are presented. The measurements were performed at the BGOOD experiment at ELSA, utilising the high angular and momentum resolution forward spectrometer for charged particle identification. The high statistics and forward angle acceptance enables the extraction of the cross section as the minimum momentum transfer to the recoiling hyperon is approached.