Reaction K − p → 0 0 ⌺ 0 was measured with the Crystal Ball multiphoton spectrometer at eight K − momenta from 514 to 750 MeV/ c. Dynamics and the energy dependence of the reaction are shown by Dalitz plots, invariant mass spectra, production angular distributions, and total cross sections. The dipion invariant-mass spectra for K − p → 0 0 ⌺ 0 show an enhancement in the low mass region; the opposite is the case for the K − p → 0 0 ⌳ and − p → 0 0 n reactions. There is no direct evidence for a f 0 ͑600͒-meson contribution to 0 0 production. Everywhere t ͑K − p → 0 0 ⌺ 0 ͒ Ӷ t ͑K − p → 0 0 ⌳͒.
The percentage depth dose in the build-up region and the surface dose for the 6-MV photon beam from a Varian Clinac 23EX medical linear accelerator was investigated for square field sizes of 5 × 5, 10 × 10, 15 × 15 and 20 × 20 cm2using the EGS4nrc Monte Carlo (MC) simulation package. The depth dose was found to change rapidly in the build-up region, and the percentage surface dose increased proportionally with the field size from approximately 10% to 30%. The measurements were also taken using four common detectors: TLD chips, PFD dosimeter, parallel-plate and cylindrical ionization chamber, and compared with MC simulated data, which served as the gold standard in our study. The surface doses obtained from each detector were derived from the extrapolation of the measured depth doses near the surface and were all found to be higher than that of the MC simulation. The lowest and highest over-responses in the surface dose measurement were found with the TLD chip and the CC13 cylindrical ionization chamber, respectively. Increasing the field size increased the percentage surface dose almost linearly in the various dosimeters and also in the MC simulation. Interestingly, the use of the CC13 ionization chamber eliminates the high gradient feature of the depth dose near the surface. The correction factors for the measured surface dose from each dosimeter for square field sizes of between 5 × 5 and 20 × 20 cm2are introduced.
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