Saclay Linac Research Articles

Photoexcitation of the quasi-bound isobar nuclear state of a nucleus in the (γ,πN) reaction

The data from three experiments performed on the Saclay linac, at the Tomsk synchrotron, and at the MAMI accelerator in Maintz, in which single pion photoproduction on light nuclei was accompanied by the emission of nucleons, are analyzed. The behavior of the experimental cross sections, which cannot be explained in the impulse approximation, is interpreted in a model where an intermediate quasi-bound isobar nuclear state is formed and decays with the emission of a pion and a nucleon.

Extraction of a parasitic electron beam and its use for a tagged photon facility at the 600 MeV Saclay linac

A device to extract a parasitic beam from the main electron beam of the Saclay 600 MeV linac is described. Such a facility is completely transparent to the other users and preserves the original duty cycle. However the intensity of this beam is very low but sufficient to test and run some particular photonuclear experiments associated with the tagged photon facility. The main characteristics and a few applications of this parasitic beam are also given.

The quasi-monochromatic photon beam used in photoneutron experiments from 20–120 MeV at the 600 MeV Saclay Linac

A beam of 20–130 MeV positrons, with average intensities between 10 nA and 50 nA, is used at the 600 MeV Saclay Linac to create a quasi-monochromatic photon beam with a continuously variable energy. This beam was used to measure photoneutron cross sections and the corresponding photonuclear facility is first described. The computer-controlled methods, implemented to measure the energy spectrum and the emittance of the positron beam are described. The quasi-monochromatic photon lines are produced by the annihilation in flight of monoenergetic positrons in two annihilation radiators with different Z successively. The photon beam emission angle θ is shown to be the most critical parameter in the search for an optimum overall signal to background ratio for a specific photoneutron experiment. The choice of an angle θ⋍4° is explained for absolute measurements of σ( γ, xn) cross-sections, for which th used average intensities of monochromatic photons were thus purposely reduced to ⋍5 x 10 3 s −1 ., with an energy resolution ⋍12%.

Cost of Saclay linac

Cost of Saclay linac

A Study of Some Transversal Motions of the Electron Beam of a Linac

It is well known that when the magnetic focusing field at the input of an electron linac increases the output accelerated current does not increase regularly. Such a behaviour is shown to be connected with rotations, in the output plane of the linac, of the center of charges of the beam. These rotations have been displayed experimentally by means of a beam position monitoring system and related to the transverse momentum transferred to the beam by the spurious TM11 mode existing in the mode converter which changes at the input of the Saclay linac, the TE01 mode from the rectangular waveguide into a TM01 mode on the accelerator circular waveguide.

The (γ, 3n) reaction in Pr 141

The isotope Pr 141 was irradiated with a bremsstrahlung beam of 33 MeV maximum energy in the Saclay Linac. Activity due to Pr 138 was detected and a lower limit of the integrated cross section from threshold to 33MeV was obtained as being 1 MeV · mb. Some features of the accepted decay scheme are confirmed.