Search results for "Helium-3"
showing 10 items of 32 documents
A polarized 3He target for the photon beam at MAMI
2011
Abstract A polarized 3 He target has been installed for the first time inside the 4 π Crystal Ball detector at the tagged photon beam of the MAinz MIcrotron (MAMI). It has been demonstrated that the system works reliably and that the polarization losses during handling of the polarized gas are under control. Initial polarization values up to 70% and total relaxation times up to 20 h could be obtained during a first test beam time devoted to the measurement of the double polarized photoabsorption cross-section in the Δ ( 1232 ) baryon resonance region.
Spectroscopy ofB13via theC13(t,He3)reaction at115AMeV
2009
Gamow-Teller and dipole transitions to final states in $^{13}\mathrm{B}$ were studied via the $^{13}\mathrm{C}(t,^{3}\mathrm{He})$ reaction at ${E}_{t}=115A$ MeV. In addition to the strong Gamow-Teller transition to the $^{13}\mathrm{B}$ ground state, a weaker Gamow-Teller transition to a state at 3.6 MeV was found. This state was assigned a spin-parity of $3/{2}^{\ensuremath{-}}$ by comparison with shell-model calculations using the WBP and WBT interactions which were modified to allow for mixing between $n\ensuremath{\hbar}\ensuremath{\omega}$ and $(n+2)\ensuremath{\hbar}\ensuremath{\omega}$ configurations. This assignment agrees with a recent result from a lifetime measurement of excited…
A high power liquid hydrogen target for the Mainz A4 parity violation experiment
2005
We present a new powerful liquid hydrogen target developed for the precise study of parity violating electron scattering on hydrogen and deuterium. This target has been designed to have minimal target density fluctuations under the heat load of a 20$\mu$A CW 854.3 MeV electron beam without rastering the electron beam. The target cell has a wide aperture for scattered electrons and is axially symmetric around the beam axis. The construction is optimized to intensify heat exchange by a transverse turbulent mixing in the hydrogen stream, which is directed along the electron beam. The target is constructed as a closed loop circulating system cooled by a helium refrigerator. It is operated by a …
On total muon capture rates and the average neutrino energy
1973
A method of avoiding the uncertainty associated with the average neutrino energy nu in the usual closure approach to muon capture rates is discussed. Instead of neglecting the kinematic dependence on each particular channel, the partial capture rate is approximated by a first-order expansion around nu . After the sum over the final states is performed, the result is quite independent of the specific value of nu . Application to /sup 3/He, /sup 6/Li and closed-shell nuclei is given, as an effective test of the nuclear models used. (17 refs).
Photoproduction of pions on 3He and 3H
1969
Abstract In this paper the photoproduction of pions on nuclei with three nucleons is considered in the “elastic” channels. The calculation is done using the impulse approximation and neglecting rescattering effects.
Photon absorption on a proton-proton pair inHe3
1995
We calculate the total cross sections for different multiple transitions in photon absorption in a {sup 1}{ital S}{sub 0} {ital pp} pair embedded in a {sup 3}He nucleus. Employing two models, one involving only nucleon degrees of freedom, the other in addition the {Delta}(1232) isobar, we show that the {Delta} gives important effects even in transitions where the photon cannot couple directly to the isobar.
Large solid-angle polarisation analysis at thermal neutron wavelengths using a 3He spin filter
2002
Abstract The strongly spin-dependent absorption of neutrons in nuclear spin-polarised 3 He opens up the possibility of polarising neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. In this paper we describe the first large solid-angle polarisation analysis measurement using a 3 He neutron spin filter at thermal neutron wavelengths ( λ =2.5 A). This experiment was performed on the two-axis diffractometer D1B at the Institut Laue-Langevin using a banana-shaped filter cell (530 cm 3 ) filled with 3 He gas with a polarisation of P =52% at a pressure of 2.7 bar. A comparison is made with a previous measurement on D7 using a cold neutr…
Nuclear transition rates in μ-catalyzedp-dfusion
1991
Nuclear transition rates in \ensuremath{\mu}-catalyzed p-d fusion have been calculated using numerically converged $^{3}\mathrm{He}$ bound-state and p-d scattering wave functions for the first time. The transition rates for M1 radiative capture in both quartet and doublet initial states have been computed using a model of meson-exchange currents which reproduces the thermal n-d capture cross section, and are in excellent agreement with experiment. The muon internal-conversion rate is in very good agreement with a recent reanalysis of old bubble-chamber measurements. Furthermore, our nonvanishing quartet capture rate resolves the anomaly in the Wolfenstein-Gerstein effect.
Properties ofNe22(α,n)25Mg resonances
1991
The $^{22}\mathrm{Ne}$(\ensuremath{\alpha},n${)}^{25}$Mg reaction has been investigated in the energy range ${\mathit{E}}_{\mathrm{\ensuremath{\alpha}}}^{\mathrm{lab}}$=0.73--2.10 MeV using high-resolution $^{3}\mathrm{He}$ ionization chambers. Sixteen resonances have been observed in the three neutron channels to the ground state and the first two excited levels of $^{25}\mathrm{Mg}$. From the analysis of neutron angular distributions, spin and parity assignments could be made for eight resonances. Furthermore, partial widths as well as absolute cross sections have been obtained yielding resonance strengths for the observed levels. The role of the $^{22}\mathrm{Ne}$(\ensuremath{\alpha},n) …
Measurement of the (anti-)3He elliptic flow in Pb–Pb collisions at sNN=5.02TeV
2020
The elliptic flow ( v 2 ) of (anti-) 3He is measured in Pb–Pb collisions at s NN = 5.02 TeV in the transverse-momentum ( p T ) range of 2–6 GeV/c for the centrality classes 0–20%, 20–40%, and 40–60% using the event-plane method. This measurement is compared to that of pions, kaons, and protons at the same center-of-mass energy. A clear mass ordering is observed at low p T , as expected from relativistic hydrodynamics. The violation of the scaling of v 2 with the number of constituent quarks at low p T , already observed for identified hadrons and deuterons at LHC energies, is confirmed also for (anti-) 3He. The elliptic flow of (anti-) 3He is underestimated by the Blast-Wave model and overe…