Measurement of gamma production in thin LiF targets at CMAM

The standard beamline at our 5MV coaxial Cockcroft-Walton tandem accelerator has been used to produce cross sections for the reaction channels ⁷Li(p,p^'γ)⁷Li (Eγ = 478 keV), ⁷Li(p,nγ)⁷Be (E_γ = 429 keV), ¹⁹F(p,p^'γ)¹⁹F (E_γ = 110 keV) and ¹⁹F(p,p^'γ)¹⁹F (E_γ = 197 keV). The target material was natural LiF; a few target assemblies were used including a carbon backing and a heavy element layer (either Ag or Au) to assure the possibility of normalization to purely Rutherford cross sections. The gamma rays have been detected by a REGe (Reverse Electron Germanium) detector, 61 mm ∅ X 60 mm, featuring a FWHM resolution of 2.0 keV at 1.33 MeV. The absolute efficiency has been measured with a calibrated set of radioactive sources (¹⁵²Eu, ¹³⁷Cs, ⁶⁰Co) with which we have covered the gamma energy range from 121.78 keV to 1408.01 keV, adequate to interpolating at the energy of the studied reactions gamma rays, with the exception of the 110 keV from ¹⁹F. The charge has been collected in the specifically designed target holder. There the target is electrically connected with a carbon FC, isolated from the ground and kept at +180 V to suppress secondary electrons. The charge is measured by means of an ORTEC 439 Digital Current Integrator. The accelerator energy calibration has been checked by repeatedly measuring the onset of the 991.9 keV resonance of the ²⁷Al(p,γ)²⁸Si. The maximum voltage difference between runs was 0.44 kV resulting in less than 1 keV energy difference. (author)