Measurements of the pair production cross section close to the threshold energy

Jentschel, M.; Urban, W.; Mutti, P.; Courtois, P.; Simpson, G. S.; Frahm, R.

doi:10.1103/physrevc.84.052501

Cited by 3 publications

(1 citation statement)

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“…The 155 Gd(n th , γ) 156 Gd reaction on a target placed inside the high-flux reactor of ILL, has been used to produce very intensive beams of well collimated γ rays. These γ rays scattered off Cu mosaic crystal mounted at GAMS4 and GAMS5 provided beams of monoenergetic γ quanta used to measure the e + e − pair-production cross section close to the 1022-keV threshold [9,10], which offers a unique possibility for progress in this field [11]. Another promising application is the tunable γ-ray source using the Compton scattering of strong discrete γ rays from various (n th , γ) reactions, constructed at ILL [12], which can be used to investigate photoexcitations in nuclei.…”

Section: Jinst 8 P03014mentioning

confidence: 99%

New instrumentation for precise (n,γ) measurements at ILL Grenoble

Urban¹,

Jentschel²,

Märkisch³

et al. 2013

J. Inst.

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An array of eight Ge detectors for coincidence measurements of γ rays from neutroncapture reactions has been constructed at the PF1B cold-neutron facility of the Institut Laue-Langevin. The detectors arranged in one plane every 45 • can be used for angular correlation measurements. The neutron collimation line of the setup provides a neutron beam of 12 mm in diameter and the capture flux of about 10 8 /(s×cm 2 ) at the target position, with a negligible neutron halo. With the setup up to 10 9 γγ and up to 10 8 triple-γ coincidence events have been collected in a day measurement. Precise energy and efficiency calibrations up to 10 MeV are easily performed with 27 Al(n, γ) 28 Al and 35 Cl(n, γ) 36 Cl reactions. Test measurements have shown that neutron binding energies can be determined with an accuracy down to a few eV and angular correlation coefficients measured with a precision down to a percent level. The triggerless data collected with a digital electronics and acquisition allows to determine half-lives of excited levels in the nano-to microsecond range. The high resolving power of double-and triple-γ time coincidences allows significant improvements of excitation schemes reported in previous (n, γ) works and complements high-resolution γ-energy measurements at the double-crystal Bragg spectrometer GAMS of ILL.

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Section: Jinst 8 P03014mentioning

confidence: 99%

New instrumentation for precise (n,γ) measurements at ILL Grenoble

Urban¹,

Jentschel²,

Märkisch³

et al. 2013

J. Inst.

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Refractive Index of Silicon atγRay Energies

et al. 2012

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For X-rays the real part of the refractive index, dominated by Rayleigh scattering, is negative and converges to zero for higher energies. For γ rays a positive component, related to Delbrück scattering, increases with energy and becomes dominating. The deflection of a monochromatic γ beam due to refraction was measured by placing a Si wedge into a flat double crystal spectrometer. Data were obtained in an energy range from 0.18 -2 MeV. The data are compared to theory, taking into account elastic and inelastic Delbrück scattering as well as recent results on the energy dependence of the pair creation cross section. Probably a new field of γ optics with many new applications opens up.

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