Laboratory Angles Research Articles

Study of the 6Li + p $ \rightarrow$ 3He + 4He reaction in inverse kinematics

Angular distribution measurements were performed for the 6Li + p\( \rightarrow\)3He + 4He reaction in inverse kinematics at incident energies of 2.7, 3.3, 4.2 and 4.8MeV/u . The detection of both recoils ( 3He and 4He over the laboratory angle range \( \theta_{lab}=16^{\circ}\) to \( 34^{\circ}\) allowed the determination of the angular distribution over a wide angular range in the center-of-mass frame ( \( \theta_{c.m.}\sim 40^{\circ}\) to \( 140^{\circ}\). The results clarify inconsistencies between existing data sets and are consistent with compound nucleus model calculations.

Precision measurements ofg1of the proton and of the deuteron with 6 GeV electrons

The inclusive polarized structure functions of the proton and deuteron, g1p and g1d, were measured with high statistical precision using polarized 6 GeV electrons incident on a polarized ammonia target in Hall B at Jefferson Laboratory. Electrons scattered at lab angles between 18 and 45 degrees were detected using the CEBAF Large Acceptance Spectrometer (CLAS). For the usual DIS kinematics, Q^2>1 GeV^2 and the final-state invariant mass W>2 GeV, the ratio of polarized to unpolarized structure functions g1/F1 is found to be nearly independent of Q^2 at fixed x. Significant resonant structure is apparent at values of W up to 2.3 GeV. In the framework of perturbative QCD, the high-W results can be used to better constrain the polarization of quarks and gluons in the nucleon, as well as high-twist contributions.

Examination of the role of theO14(α,p)F17reaction rate in type-I x-ray bursts

The $^{14}\mathrm{O}(\ensuremath{\alpha},p)^{17}\mathrm{F}$ reaction is one of the key reactions involved in the breakout from the hot-CNO cycle to the rp-process in type-I x-ray bursts (XRBs). The resonant properties in the compound nucleus $^{18}\mathrm{Ne}$ have been investigated through resonant elastic scattering of $^{17}\mathrm{F}+p$. The radioactive $^{17}\mathrm{F}$ beam was separated by the Center for Nuclear Study radioactive ion beam separator (CRIB) and bombarded a thick ${\mathrm{H}}_{2}$ gas target at 3.6 MeV/nucleon. The recoiling light particles were measured by three $\ensuremath{\Delta}E\text{\ensuremath{-}}E$ silicon telescopes at laboratory angles of ${\ensuremath{\theta}}_{\mathrm{lab}}\ensuremath{\approx}3{}^{\ensuremath{\circ}},10{}^{\ensuremath{\circ}}$, and $18{}^{\ensuremath{\circ}}$. Five resonances at ${E}_{x}=6.15$, 6.28, 6.35, 6.85, and 7.05 MeV were observed in the excitation functions, and their spin-parities have been determined based on an $R$-matrix analysis. In particular, ${J}^{\ensuremath{\pi}}={1}^{\ensuremath{-}}$ was firmly assigned to the 6.15-MeV state which dominates the thermonuclear $^{14}\mathrm{O}(\ensuremath{\alpha},p)^{17}\mathrm{F}$ rate below 2 GK. As well, a possible new excited state in $^{18}\mathrm{Ne}$ was observed at ${E}_{x}=6.85\ifmmode\pm\else\textpm\fi{}0.11$ MeV with tentative $J=0$ assignment. This state could be the analog state of the 6.880 MeV $(0{}^{\ensuremath{-}})$ level in the mirror nucleus $^{18}\mathrm{O}$, or a bandhead state $(0{}^{+})$ of the six-particle four-hole (6p-4h) band. A new thermonuclear $^{14}\mathrm{O}(\ensuremath{\alpha},p)^{17}\mathrm{F}$ rate has been determined, and the astrophysical impact of multiple recent rates has been examined using an XRB model. Contrary to previous expectations, we find only a modest impact on predicted nuclear energy generation rates from using reaction rates differing by up to several orders of magnitude.

Elastic recoil cross section determination of 1H by 4He ions at 30° and energy range of 1.6–6.0 MeV

In this paper, the differential cross-section for forward recoiling 1H with 4He ions has been determined in the energy range of 1.6–6.0MeV at a laboratory angle of 30°. A film of ∼54nm TiHx on the Si substrate with an overlayer of ∼7nm Ta on the TiHx foil was used as the target, and hydrogen loss of the target due to ion bombardment can be fully ignored (<0.1%) through the whole measurement. A method of relative determination for the cross-section measurement was employed to be free from absolute determination of hydrogen content in the target as well as absolute measurements of beam dose and solid angles of the detectors. The uncertainty of the determination is less than 5.2%.

Compton scattering fromC12using tagged photons in the energy range 65–115 MeV

Elastic scattering of photons from 12C has been investigated using quasi-monoenergetic tagged photons with energies in the range 65 - 115 MeV at laboratory angles of 60 deg, 120 deg, and 150 deg at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the 12C(g,g)12C cross section to the bound-nucleon polarizabilities.

Spin-dependent cross sections from the three-body photodisintegration ofHe3at incident energies of 12.8 and 14.7 MeV

The first measurement of the three-body photodisintegration of polarized $^{3}\mathrm{He}$ using a circularly polarized photon beam has been performed at incident energies of 12.8 and 14.7 MeV. This measurement was carried out at the high-intensity $\ensuremath{\gamma}$-ray source located at Triangle Universities Nuclear Laboratory. A high-pressure $^{3}\mathrm{He}$ target, polarized via spin exchange optical pumping with alkali metals, was used in the experiment. The spin-dependent double- and single-differential cross sections from $\stackrel{P\vec}{{}^{3}\text{He}}(\stackrel{P\vec}{\ensuremath{\gamma}},n)pp$ for laboratory angles varying from ${30}^{\ensuremath{\circ}}$ to ${165}^{\ensuremath{\circ}}$ are presented and compared with state-of-the-art three-body calculations. The data reveal the importance of including the Coulomb interaction between protons in the three-body calculations.

Experimental study of nuclear fragmentation of 200 and 400 MeV/u 12C ions in water for applications in particle therapy

Carbon ion beams in the energy range of about 100–450 MeV/u offer excellent conditions for tumour therapy, in particular for the treatment of deep-seated radio-resistant tumours. Their depth-dose distribution is characterized by a low dose in the entrance channel, small lateral beam spread and an elevated biological effectiveness in the Bragg peak region. In comparison to protons the radiation field of heavier ions stopping in tissue is however more complex due to nuclear fragmentation reactions occurring along their stopping path. This results in an attenuation of the primary beam flux and a build-up of lower-Z fragments with longer ranges causing the characteristic dose tail beyond the Bragg peak. In the present work the characteristics of secondary charged particles at various depths of water were investigated experimentally using 12C ion beams of 200 and 400 MeV/u delivered by the heavy-ion synchrotron SIS-18 at GSI Darmstadt. The nuclear charge Zf of secondary fragments was identified by combining energy loss and time-of-flight (TOF) measurements. Energy spectra and yields were recorded at lab angles of 0° – 10° and at seven different water depths corresponding to the entrance channel, the Bragg peak region and the tail of the Bragg curve.

Measurement of the yields of positively charged particles at an angle of 35° in proton interactions with nuclear targets at an energy of 50 GeV

Momentum spectra of cumulative particles in the region of high transverse momenta (P T ) in pA → h + + X reactions were obtained for the first time. The experiment in which this was done was performed at the SPIN setup (Institute for High Energy Physics, Protvino) in a beam of 50-GeV protons interacting with C, Al, Cu, and W nuclei. Positively charged particles were detected at a laboratory angle of 35° and in the transverse-momentum range between 0.6 and 3.7 GeV/c. A strong dependence of the particle-production cross section on the atomic number was observed. A comparison with the results of calculations based on the HIJING and UrQMD models was performed in the subcumulative region.

Study of the 10B(p,α) reaction between 2.1 and 6.0 MeV

The differential cross section of the 10B(p,α)7Be reaction has been measured for bombarding proton energies between 2.1MeV and 6.0MeV, in 100keV steps, at seven laboratory angles from 30° to 150°. This reaction is of importance because it can be a source of radioactive waste in reactors which will use boron as a nuclear fuel. The total cross section was extracted at each proton energy. On average, the results of this experiment are ∼16% higher than previously reported measurements. The astrophysical S-factors were also extracted from the total cross sections.

Dynamics of the C/H and C/F exchanges in the reaction of 3P carbon atoms with vinyl fluoride

Two product channels C3H2F + H and C3H3 + F were identified in the reaction of C((3)P) atoms with vinyl fluoride (C2H3F) at collision energy 3.7 kcal mol(-1) in a crossed molecular-beam apparatus using selective photoionization. Time-of-flight (TOF) spectra of products C3H2F and C3H3 were measured at 12-16 laboratory angles as well as a TOF spectrum of atomic F, a counter part of C3H3, was recorded at single laboratory angle. From the best simulation of product TOF spectra, translational-energy distributions at seven scattering angles and a nearly isotropic (forward and backward peaked) angular distribution were derivable for exit channel C3H2F + H (C3H3 + F) that has average kinetic-energy release of 14.5 (4.9) kcal mol(-1). Products C3H2F + H and C3H3 + F were estimated to have a branching ratio of ~53:47. Furthermore, TOF spectra and photoionization spectra of products C3H2F and C3H3 were measured at laboratory angle 62° with photoionization energy ranging from 7 eV to 11.6 eV. The appearance of TOF spectra is insensitive to photon energy, implying that only single species overwhelmingly contributes to products C3H2F and C3H3. HCCCHF (H2CCCH) was identified as the dominant species based on the measured ionization threshold of 8.3 ± 0.2 (8.6 ± 0.2) eV and the maximal translational-energy release. The C/H and C/F exchange mechanisms are stated.

Finite Element Modeling of Parabolic Trough Mirror Shape in Different Mirror Angles

Deviations from the ideal shape of reflector panels for parabolic trough solar power plants can have relevant impact on field efficiency and thus on the performance of the whole power plant. Analyzing the gravity-induced deformation of mirror shape for different mirror angles is relevant for performance calculation of solar parabolic trough collectors and identifying optimization potential of the mirror panels. Two mirror model cases (stiff and elastic supports) are evaluated in four angles: in horizontal laboratory angle (mirrors facing upward with mounting points horizontally aligned), and in 0 deg, 45 deg, and 90 deg collector angle. The resulting slope maps are calculated in a separate postprocessing. In order to evaluate the effect of gravity load on mirror shape, the deformed mirror in each evaluated angle is compared to the nondeformed mirror shape, and to the shapes in 0 deg (zenith) collector angle, respectively. The resulting slope deviation maps show the mirror deformation in different mirror angles. Stiffness of the mounting to the support structure has a relevant impact. Mirror deformation on elastic brackets (SDx up to 1.6 mrad) is much more pronounced than on an ideal stiff support structure (SDx up to 1.0 mrad).

A survey of backward proton and pion production in p + C interactions at beam momenta from 1 to 400 GeV/c

Recent data on proton and pion production in p+C interactions from the CERN PS and SPS accelerators are used in conjunction with other available data sets to perform a comprehensive survey of backward hadronic cross sections. This survey covers the complete backward hemisphere in the range of lab angles from 10 to 180 degrees, from 0.2 to 1.4 GeV/c in lab momentum and from 1 to 400 GeV/c in projectile momentum. Using the constraints of continuity and smoothness of the angular, momentum and energy dependences a consistent description of the inclusive cross sections is established which allows the control of the internal consistency of the nineteen available data sets.

New results from the NA49 experiment on hadron production in p+p and p+C interactions and survey of backward hadrons in p+C collisions

Recent results on proton, anti-proton, neutron and charged kaon production in proton-proton and proton, anti-proton, neutron, deuteron and triton production in proton-carbon collisions at 158 GeV/c beam momentum are presented. Data samples of 4.8 million and 385 734 inelastic events in p+p and p+C, respectively, are obtained with the NA49 detector at the CERN SPS accelerator. The charged particles are identified by energy loss measurement in a system of four TPC chambers, while the neutrons are detected in a forward hadronic calorimeter. The data cover a major fraction of the phase space, ranging from 0 to 1.9 GeV in pT and in Feynman x variable from -0.8 to 0.95 for protons, from -0.2 to 0.3 for anti-protons, from 0.1 to 0.95 for neutrons and from 0 to 0.5 for kaons. The comparison of the results on proton and neutron production in p+p interactions and deep inelastic e+p collisions at HERA reveals an independence of target fragmentation on the projectile type. Using the charged kaon data in p+p collisions as a reference, a new evaluation of the energy dependence of kaon production, including neutral kaons, is conducted over a range from 3 GeV to p+p− collider energies. A survey of backward production of protons and pions in p+C collisions in the range of lab angles from 10 to 180 degrees, from 0.2 to 1.2 GeV/c in lab momentum and from 1 to 400 GeV/c in projectile momentum has been performed.

No evidence of an 11.16 MeV 2+state in12C

An experiment using the ${}^{11}$B(${}^{3}$He,$d$)${}^{12}$C reaction was performed at iThemba LABS at an incident energy of 44 MeV and analyzed with a high energy-resolution magnetic spectrometer, to reinvestigate states in ${}^{12}$C published in 1971. The original investigation reported the existence of an 11.16 MeV state in ${}^{12}$C that displays a 2${}^{+}$ nature. In the present experiment, data were acquired at laboratory angles of 25${}^{\ensuremath{\circ}}$, 30${}^{\ensuremath{\circ}}$, and 35${}^{\ensuremath{\circ}}$, which is part of the center-of-mass (c.m.) angle range in the original measurements where a clear signature of such a state was observed. These new low-background measurements revealed no evidence of the previously reported state at 11.16 MeV in ${}^{12}$C.

Enhancedα-particle emission in12C+232Th fission due to the transfer-breakup process

The $\ensuremath{\alpha}$-particle energy spectra have been measured in coincidence with fission fragments (FFs) in the ${}^{12}$C (69 MeV)+${}^{232}$Th reaction at various relative angles with respect to FF direction. The spectra were fitted with a moving-source model calculation to extract the multiplicities corresponding to different emission stages of the fusion-fission process. The fitted value for the near-scission emission component appears anomalously enhanced in comparison to the recently developed systematics for prescission and near-scission $\ensuremath{\alpha}$-particle multiplicities in heavy-ion reactions. A high-energy component corresponding to the summed energy of two $\ensuremath{\alpha}$ particles is observed, which suggests breakup of ${}^{8}$Be into two $\ensuremath{\alpha}$ particles in $\ensuremath{\alpha}$-transfer-induced fission coincidence events. The ${}^{8}$Be breakup fits the 2$\ensuremath{\alpha}$-particle multiplicity spectra very well at different laboratory angles. When ${}^{8}$Be breakup is included exclusively as a source of $\ensuremath{\alpha}$-particle emission in the moving-source analysis along with prescission, postscission, and near-scission emission, the results follow the systematics of heavy-ion data very well. The present results clearly indicate an extra source of $\ensuremath{\alpha}$-particle emission due to ${}^{8}$Be breakup in $\ensuremath{\alpha}$-transfer-induced fission reactions.

Exploring the Dynamics of Reaction C(3P) + C2H4 with Crossed Beam/Photoionization Experiments and Quantum Chemical Calculations

We investigated the title reaction at collision energy 3.5 kcal mol(-1) in a crossed molecular beam apparatus using undulator radiation as an ionization source. Time-of-flight (TOF) spectra of product C(3)H(3) were measured in laboratory angles from 20° to 100° using two photoionization energies 9.5 and 11.6 eV. These two sets of experimental data exhibit almost the same TOF distributions and laboratory angular distributions. From the best simulation, seven angle-specific kinetic-energy distributions and a nearly isotropic angular distribution are derived for product channel C(3)H(3) + H that has an average kinetic-energy release of 15.5 kcal mol(-1), corresponding to an average internal energy of 33.3 kcal mol(-1) in C(3)H(3). Furthermore, TOF spectra of product C(3)H(3) were measured at laboratory angle 52° with ionizing photon energies from 7 to 12 eV. The appearance of TOF spectra remains almost the same, indicating that a species exclusively contributes to product C(3)H(3); the species is identified as H(2)CCCH (propargyl) based on the ionization energy of 8.6 ± 0.2 eV and the maximal kinetic-energy release of 49 kcal mol(-1). Theoretical calculations indicate that the rapid inversion mechanism and rotation in intermediate H(2)CCCH(2) can result in a forward-backward symmetric angular distribution for product C(3)H(3) + H. The present work avoids the interference of reactions of C((1)D) and C(2) radicals with C(2)H(4) and rules out the probability of production of other isomers like c-C(3)H(3) and H(3)CCC proposed in the previous work at least at the investigated collision energy.

Gender differences in trunk, pelvis and lower limb kinematics during a single leg squat

The relationship between trunk and lower limb kinematics in healthy females versus males is unclear since trunk kinematics in the frontal and transverse planes have not been systematically examined with lower limb kinematics. The aim of this study was to investigate the existence of different multi-joints movement strategies between genders during a single leg squat. We expected that compared to males, females would have greater trunk and pelvis displacement due to less trunk control and display hip and knee movement consistent with medial-collapse (i.e. greater hip adduction, hip medial rotation, knee abduction, and knee lateral rotation) on the weight-bearing limb.Nine females and 10 males participated in the study. Kinematic data were collected using an 8-camera, 3D-motion-capture-system. Trunk relative to pelvis, pelvis relative to the laboratory, hip and knee angles in three planes (sagittal, frontal and transverse) were examined at two time events relevant to knee joint mechanics: 45° of knee flexion and peak knee flexion.Females flexed their trunk less than males and rotated their trunk and pelvis toward the weight-bearing limb more than males. Females also displayed greater hip adduction and knee abduction than males.Taken together these results suggest that females and males used different movement strategies during a single leg squat. Females displayed a trunk and pelvic movement pattern that may put them at risk of knee injury and pain.

Probing of compact baryonic configurations in nuclei inA(p,p¯)Xreactions and antiproton formation length in nuclear matter

Inclusive cross sections $\sigma^A=Ed^3{\sigma(X,P_t^2)/d^3p}$ of antiproton and negative pion production on Be, Al, Cu and Ta targets hit by 10 GeV protons were measured at the laboratory angles of 10.5$^{\circ}$ and 59$^{\circ}$. Antiproton cross sections were obtained in both kinematically allowed and kinematically forbidden regions for antiproton production on a free nucleon. The antiproton cross section ratio as a function of the longitudinal variable $X$ exhibits three separate plateaus which gives evidence for the existence of compact baryon configurations in nuclei-small-distance scaled objects of nuclear structure. Comparability of the measured cross section ratios with those obtained in the inclusive electron scattering off nuclei suggests a weak antiproton absorption in nuclei. Observed behavior of the cross section ratios is interpreted in the framework of a model considering the hadron production as a fragmentation of quarks (antiquarks) into hadrons. It has been established that the antiproton formation length in nuclear matter can reach the magnitude of 4.5 fm.

Deuteron-production double-differential cross sections for 300- and 392-MeV proton-induced reactions deduced from experiment and model calculation

Deuteron production from intermediate-energy proton-nucleus interactions was investigated through experiments and model calculations, mainly to develop a theoretical model by elucidating the mechanism of cluster production. Spectral double-differential cross sections were measured for inclusive $(p,dx)$ reactions on five targets in the periodic table, namely ${}^{12}$C, ${}^{27}\phantom{\rule{-0.16em}{0ex}}$Al, ${}^{51}\phantom{\rule{-0.16em}{0ex}}$V, ${}^{93}$Nb, and ${}^{197}$Au, at beam energies of 300 and 392 MeV. The cross sections were determined in almost the entire outgoing energy range from the highest down to 30 MeV and at laboratory angles from 20${}^{\ensuremath{\circ}}$ to 104${}^{\ensuremath{\circ}}$. To interpret the measured spectra, we proposed a new model that includes the nucleon correlations of the initial- and final-state interactions to describe cluster knockout and pickup within the intranuclear cascade model. The results of the model calculations showed reasonable agreements with those of the experiments. Moreover, the model indicated reasonable predictive power for the ($p{,}^{3}\phantom{\rule{-0.16em}{0ex}}\mathrm{He}x$), $(p,\ensuremath{\alpha}x)$, and $(d,{d}^{\ensuremath{'}}x)$ reactions measured elsewhere. The quantum molecular dynamics model underpredicts the results of the experiments by two to three orders except for low-energy portions of the $(p,dx)$ spectra.

Further evidence for the broad22+state at 9.6 MeV in12C

We measured the ${}^{12}\mathrm{C}{(p,{p}^{\ensuremath{'}})}^{12}{\mathrm{C}}^{*}$ reaction at 25 MeV at the three laboratory angles of20\ifmmode^\circ\else\textdegree\fi{}, 35\ifmmode^\circ\else\textdegree\fi{}, and 45\ifmmode^\circ\else\textdegree\fi{}. The measured spectra support recent evidence for a new broad${2}_{2}^{+}$ state at 9.6 MeV in ${}^{12}\mathrm{C}$, but do not support the claim for such a broad state at 11.1 MeV.