Proton Angles Research Articles

A New Fast Neutron Spectrometer Made of Epitaxial Integrated dE-E Si Detector

A fast neutron spectrometer by recoil proton detection method was developed. The spectrometer is consisted of a radiator and an integrated dE-E Si detector, in which an epitaxial dE counter of less than 10 ?m and an E counter are incorporated. Recoil protons from the radiator can easily be identified from ? ray background; and besides each recoil proton angle can be determined by the dE and E counter outputs. and thus an unfolded neutron spectrum can be attained. Neutron detection efficiency is high, compared with conventional dE-E telescope spectrometers, owing to the wide solid angle coverage of recoil protons. The basic characterestics and measured neutron spectra are described.

Measurement of the differential cross section for the reaction π+ + d → p + p at momenta between 0.48 and 1.16 [formula omitted

The differential cross section for the reaction π + + d → p + p has been measured at pion momenta between 0.48 and 1.16 GeV c with steps of 20 and 40 GeV c for seven CM proton angles between 6° and 61°. At smaller angles, the measured cross sections show a dip at around 0.7 GeV c , while at larger angles the cross sections vary monotonically as a function of incident momentum. The angular distribution shows a considerably rapid variation with increasing momentum. Legendre polynomial fits of the data are presented.

Isospin dependence of pion absorption on nucleon pairs in 3He

The ratio of quasifree pion absorption on nucleon pairs with isospin I = 0 and I = 1 has been measured in 3He. The ratios R(T π, θ lab ) = σ[ 3 He(π +, pp)]/σ[ 3 He(π −, np)] were determined for 120 MeV pions at proton angles of 77° and 54° relative to the incident beam and for 165 MeV pions at 54°. The corresponding results are: R(120, 77) = 22.2 ± 7.5, R(120, 54) = 17.0 ± 5 and R(165, 54) = 25.0 ± 7, respectively. Together with our previous results on pions at rest the data provide for the first time a homogeneous set of R values from kinematically complete experiments over a wide energy range.

Two-body photodisintegration ofHe3between 150 and 350 MeV

Differential cross sections for /sup 3/He(..gamma..,d)/sup 1/H for incident energies between 150 and 350 MeV at center-of-mass proton angles near 60/sup 0/ and 90/sup 0/ have been measured with an absolute uncertainty of less than 6%. The experiment used a single-arm spectrometer, a gas target, and an uncollimated bremsstrahlung beam. The results are in good agreement with new measurements of the time-reversed reaction, /sup 2/H(p,/sup 3/He)..gamma.., giving no evidence for a violation of time-reversal invariance. The differential cross sections decrease smoothly with energy and show only a small contribution from the ..delta..(1232) resonance.

Nucleon multiplicity associated with energetic protons from theC12+Ni60reaction

Z = 1--7 particles were observed in coincidence with energetic protons that resulted from bombardment of /sup 60/Ni with 191-MeV /sup 12/C ions. The multiplicities of the coincident particles and their dependence on the angle of the gating energetic protons are consistent with the existence of two principal reaction processes of comparable magnitude yielding energetic protons: (1) disintegration of the projectile and (2) preequilibrium emission with the remaining projectile mass fusing with the target usually at low excitation energy.

(π±,π±p) reaction at 245 MeV

The inclusive (..pi../sup + -/,..pi../sup + -/p) reactions on C, Fe, and Bi were studied at 245 MeV in a broad kinematic range by means of coincidence measurement of the outgoing particles. The ..pi..-p angular correlations and proton-energy spectra show features consistent with those expected from quasifree scattering. It is observed that about 80% of the inclusive inelastic scattering cross section at backward pion angles may be attributed to nucleon knockout mechanisms. The results allow identification of the direct quasifree process, unperturbed by higher order effects, which accounts for 30, 20, and 15% of the C, Fe, and Bi inclusive (..pi../sup +/,..pi../sup +/) differential cross sections, respectively. The ratio of positive to negative pion cross sections for quasifree scattering, integrated over the proton energy and angle, are in agreement with the ratio for free ..pi..-p scattering. Such is not the case for various proton angles. The deviation of the positive to negative ratio at the peak of the proton angular correlation from the free scattering ratio is most pronounced for more forward pion angles.

Quasielastic Omega Photoproduction at 50-130 GeV

A study of quasielastic $\ensuremath{\omega}$ photoproduction where the $\ensuremath{\omega}$ was detected in its ${\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ decay mode is reported. The recoil proton's angle was detected with a nonmagnetic spectrometer allowing a full reconstruction of the final state. Differential cross sections for $0.1<|t|<1.2$ ${\mathrm{GeV}}^{2}$ are presented, providing a test of the vector-meson dominance model over an extensive energy and momentum transfer range. The shape of the differential cross section agrees with that seen in both elastic $\ensuremath{\gamma}p$ and $\ensuremath{\pi}p$ scattering as expected from this model.

P + 3He elastic backward scattering at intermediate energies

The p 3He elastic backward scattering cross sections have been measured in the laboratory kinetic energy range 700 ⩽ T p ⩽ 1700 MeV for backscattered proton angle 160° < θ p < 180° in the c.m. A change in the slope of the cross sections and a bump in the 180° excitation function are observed around T p = 1300 MeV. These features are explained are explained as due to baryonic excitation in intermediate states.

Field line topology in the dayside cusp region inferred from low altitude particle observations

Dayside low altitude satellite observations of the pitch angle and energy distribution of electrons and protons in the energy range 1 eV to 100 eV during quite geomagnetic conditions reveal that at times there is a clear latitudinal separation between the precipitating low energy (keV) electrons and protons, with the protons precipitating poleward of the electrons. The high energy (100 keV) proton precipitation overlaps both the low energy (keV) electron and proton precipitation. These observations are consistent with a model where magnetosheath particles stream in along the cusp field lines and are at the same time convected poleward by an electric field. The electrons with energies of a few keV move fast and give the “ionospheric footprint” of the distant cusp. The protons are partly convected poleward of the cusp and into the polar cap. Here the mirroring protons populate the plasma mantle. Equatorward of the cusp the pitch angle distribution of both electrons and protons with energies above a few keV is pancake shaped indicating closed geomagnetic field lines. The 1 keV electrons, penetrate, however, into this region of closed field line structure maintaining an isotropic pitch angle distribution. The intensity is, however, reduced with respect to what it was in the cusp region. It is suggested that these electrons, the lowest energies measured on the satellite, are associated with the entry layer.

Analysis and depth profiling of deuterium with the D( 3He, p) 4He reaction by detecting the protons at backward angles

Detection at backward angles of protons from D( 3He, p) 4He presents distinct advantages with respect to the associated α particle detection used until now for depth profiling deuterium. This geometry does not require glancing incidence for good depth resolution so that rough samples may be analyzed, while the flux and energy of the elastically scattered beam particles is reduced, their pile-up problems minimized, their filtering, when necessary, with mylar absorbers or electrostatic deflectors more favourable, etc. The various contributions to the depth resolution have been calculated taking into account detector acceptance angle, size of the probing beam, energy straggling, multiple scattering and lateral spread contributions and the way to combine them discussed in detail. The 13 MeV protons emitted at 165° for E 3He=700 keV were detected using a 1500 μ deep silicon surface barrier detector with a measured overall resolution of 17 keV (fwhm). The probing beam was produced with a 350 kV HVEE accelerator using 3He 2+ ions thus demonstrating the feasibility of such measurements with low energy ion implantation machines. Depth resolutions were measured and found to be in good agreement with theory. Typically, surface resolutions of 500 Å were reached for incident beams normal to the target surface. This resolution could be reduced below 200 Å by tilting the target with respect to the beam. The method has been applied to deuterium depth profiling in amorphous silicon hydrogenated by implantation or plasma diffusion of deuterium. A comparison with SIMS measurements is reported.

Angular correlation measurements of the reaction 9Be(d, p1γ)10Be at 1.5 MeV

Abstract The proton-gamma angular correlation functions of the 9Be(d, p1γ)10Be reaction have been measured at a lab bombarding energy of 1.5 MeV for different proton angles between 40° and 150°. The experimental results are consistent with considerable contributions from the compound nucleus reaction mechanism. Population numbers for the different magnetic substates are deduced from the experimental results.

Ion-cyclotron noise excitation in the topside ionosphere according to observations at the Intercosmos-14 satellite

A band-limited ELF emission having very distinct upper as well as lower cutoff frequencies, most probably determined by local parameters of the plasma, were discovered by the VLF experiment on board the Intercosmos-14 satellite (apogee height 1707 km, perigee 345 km; inclination 74°). This type of noise was observed in the day-time, at middle and low latitudes, at altitudes 600 km< h < 1400 km. The very clear case observed on March 5, 1976 is discussed in detail and arguments are listed that this ELF emission is locally generated ion-cyclotron noise. Calculations of the growth of the proton cyclotron resonance instability show that the growth may be positive if the loss cone angle of the energetic protons is sufficiently great. This condition is fulfilled at low altitudes near the mirror points. Depending on the width of the distribution function of energetic protons the growth of the Instability may be positive in the whole frequency band of the proton branch of ion-cyclotron waves or only in certain parts of that frequency band.

Elastic scattering at small angles of protons

Abstract Differential cross sections and asymmetries are obtained from elastic scattering, between 0° and 7°, of 36.2 MeV polarized protons by C, Al, Fe and Ni natural targets.

Elastic scattering of polarized protons fromC13for9.1&lt;Ep&lt;18.4MeV

The proton elastic scattering cross sections for $^{13}\mathrm{C}$ have been measure at eight angles for proton energies from 9.1 to 18.4 MeV. Angular distributions of cross sections and analyzing powers were measured at 20 angles in 7.5\ifmmode^\circ\else\textdegree\fi{} steps over the range of 30\ifmmode^\circ\else\textdegree\fi{} to 155\ifmmode^\circ\else\textdegree\fi{} at ten energies between 10 and 17.5 MeV. A spin-\textonehalf{} on spin-\textonehalf{} phase-shift analysis was performed starting with spin-\textonehalf{} on spin-0 phase shifts obtained from an optical model analysis. The transformation from the \textonehalf{} on 0 case to the \textonehalf{} on \textonehalf{} case, when the second \textonehalf{} spin is totally ineffective, is presented and utilized. The results suggest that broad resonances are present near ${E}_{x}=21.5$ MeV in $^{14}\mathrm{N}$.NUCLEAR REACTIONS $^{13}\mathrm{C}(\stackrel{\ensuremath{\rightarrow}}{p}, p)$; measured $\ensuremath{\sigma}(E, \ensuremath{\theta})$, $E=9.1\ensuremath{-}18.4$ MeV; measured $A(E, \ensuremath{\theta})$, $E=10\ensuremath{-}17.5$ MeV. Phase-shift analyzed. Examined for effects of broad resonances. Enriched targets.

Final-state interactions in the high-energy proton-deuteron charge exchange reaction

The charge exchange channel of the proton-deuteron break-up reaction pd to npp at 1 GeV is studied in impulse approximation. The final-state interaction in the 1S0 state of the pp subsystem induces a slight asymmetry in the spectator proton angle and a threshold enhancement in the pp effective mass. The 20% of the observed events which have large effective mass may be explained quantitatively by the production of a Delta resonance which is de-excited through a final-state interaction with the spectator nucleon. It is concluded that almost all of the small-angle np charge exchange cross section at this energy involves nucleon spin-flip.

Short-Range, High-Momentum Effects in the ReactionO16(γ, p0)forEγ=100−300MeV

The $^{16}\mathrm{O}(\ensuremath{\gamma}, {p}_{0})$ cross section has been measured for a series of photon energies between 100 and 300 MeV at proton angles of 45\ifmmode^\circ\else\textdegree\fi{}, 90\ifmmode^\circ\else\textdegree\fi{}, and 135\ifmmode^\circ\else\textdegree\fi{}. Above 250 MeV, the results exceed simple shell-model predictions by several orders of magnitude. The data are compared with a calculation which involves $\ensuremath{\Delta}$ excitation in an intermediate state.

The π −d breakup reaction and Δ's in the deuteron

The cross section for forward protons in the reaction π −d→pX has been measured at 1.046, 1.113 and 1.180 GeV/ c. The observed cross section decreases with proton angle, in contrast with an impulse approximation calculation of π −p(n)→ π −p(n), but in agreement with a description of the reaction in terms of a ΔΔ-component. Using the cross section estimate by Nath et al., an upper limit for the ΔΔ-probability of 0.4% is deduced from the present data.

Pitch angle and radial diffusion of MeV protons in the outer magnetosphere

The latitude dependence of the field line-averaged pitch angle diffusion coefficient of 1-MeV protons in the magnetosphere has been calculated under the following assumptions: Scattering is due to gyroresonant interaction with a broad band spectrum of ion cyclotron waves, and the magnetospheric magnetic field model includes the internal dipole and the external solar wind compression as well as night side current sheet effects. In addition, calculations were performed in a model which simulates geomagnetic storm time ring currents. It could be shown that the power levels of normal quiet time magnetospheric wave activity are not sufficient to cause strong pitch angle scattering but that this situation may change during geomagnetic storms, as has indeed been observed. By using the field line-averaged pitch angle diffusion coefficient the associated radial diffusion coefficent kappa/sub perpendicular/ (either through gyroresonant interaction or through shell splitting) was calculated. It was shown that kappa/sub perpendicular/ was too small in the pseudotrapping region to compete with direct particle access and that it yielded values comparable with previous estimates due to other processes in the high-latitude closed drift shell region. In contrast to these other estimates, which involved sudden impluses and sudden commencements to provide the magnetic fluctuations, themore » wave-particle interaction picture developed here implies a steady radial diffusion at all times, temporal enhancements occurring during geomagnetically disturbed times. (AIP)« less

High-resolution measurements of analogue states in 59,61,63Cu

Differential cross sections were measured at four angles for proton scattering on 58,60,62Ni at energies from 3.0 to 4.0 MeV by means of a high-resolution beam from the Tokyo Institute of Technology 4 MV Van de Graaff. An overall resolution of 400 eV was realized using thin solid targets. Five fragmented p-wave analogue states and two fragmented g-wave analogue states were identified in the elastic scattering data. Spectroscopic factors and Coulomb energy differences were extracted for the analogue states. Spins, parities, total and partial widths were obtained for all resonances observed. The s-wave width and spacing distributions were also analyzed.

An unassociated particle method for producing a standard neutron flux from the D-D reaction

In the associated particle method for producing a standard monoenergetic neutron flux from the D(d, n) 3He reaction, the neutron flux is deduced from the associated 3He flux, but a number of difficulties arise when using solid targets, especially those caused by the slowing down of the deuteron beam in the target. A method is described for the establishment of a standard neutron flux by measuring the uncorrelated proton flux from the competing D(d, p)T reaction. It is shown that, for a neutron angle of about 92° and a proton angle of about 108°, the ratio of neutrons to protons is constant to within 1% for all deuteron energies between 0 and 140 keV. This implies that the standard neutron flux so defined is almost independent of the properties of the solid target being used.