No abstract available

[en] Use of multileaf collimator (MLC) for shaping the treatment fields in external beam therapy is now a common practice. Tongue and groove arrangement is used in all commercially available multileaf collimators to limit interleaf leakage. The tongue and groove effect (TGE) is an under-dosing effect in the region of overlap between two adjacent leaves of a multileaf collimator. Mean dose reduction (MDR) and its spatial extent (in terms of FWHM) at the field junctions defined by Varian Standard 80 leaves MLC for 6 and 18 MV photon beams were measured using radiographic and radiochromic films. Measured values of MDR and mean FWHM are presented for three different field geometries, namely, a narrow field, a medium size rectangular field and an irregular field at the depth of dose maximum (dm) as well as at 10 cm depth. These three fields correspond to the treatment fields used in intensity modulated radiotherapy (IMRT) and conformal/conventional radiotherapy. FWHMs are found to be independent of beam energy, depth of measurement and field geometry. However, MDA depends on beam energy, depth of measurement and field geometry. Maximum dose reduction of 17.6% with spatial extent of 2.8 mm was observed at the dm of 6 MV photon beam for the narrow field. (author)

[en] In the energy region 10 - 100 TeV both the c.r. composition from direct measurements and the cross section for high energy secondary production in the very forward region for p-air interactions are rather uncertain. Contemporaneous measurements of the total energy and of the threshold energy/nucleon of the primary particle can be provided by the atmospheric Cherenkov light and high energy muons. These measurements are performed by the combined operation of the Cherenkov array of the EAS-TOP experiment on the surface (810 gcm² atmospheric depth) and of the LVD experiment in the underground Gran Sasso Laboratories (3300 m w.e.; E^th_μ = 1.3 TeV) leading to the measurement of < N_μ > (E_μ > 1.3 TeV, E₀) in the given energy range. The combined operation of the experiments and preliminary results are reported