  In this article, a detailed investigation has been done for the long lived
gamma activity due to neutron emitting experiments. These calculations mainly
focused on the experiments used for energy calibration purposes. Calibrated
energy is one of the most essential features of any accelerator facility.
Several experiments have been used for this purpose. Generally, experiments
having sharp curvature change in cross section of yield are used. Neutron
emitting experiments are one of such. Around the globe reactions like
$^7Li(p,n)$, $^{13}C(p,n)$, $^{19}F(p,n)$, $^{27}Al(p,n)$ etc. are used to
calibrate energy of the beam with accelerator terminal voltage. Neutrons coming
from these experiments can interact with surrounding elements. These
interactions with neutrons can create long lived gamma activity which may
interfere with future measurements. The present study has been done keeping in
mind the new Facility for Research in Experimental Nuclear Astrophysics (FRENA)
at Saha Institute of Nuclear Physics. It is a 3MV tandetron low energy high
current machine.
