Background: The accuracy and the reproducibility of radiotherapy can be provided by using immobilization devices such as thermoplastic masks. In head and neck cancer radiotherapy, the patients are mostly immobilized by using thermoplastic masks. In this study, the effect of the thermoplastic mask to the surface and buildup region doses was investigated by using Markus parallel plate ion chamber...

The Advanced Photon Source (APS) is a 7-GeV, thirdgeneration synchrotron radiation source. To provide more stable beam for users, in September 1998 we began commissioning a new operating mode called “top-up.” In this mode, the beam current does not decay but is maintained at a high level using frequent injection, while photon shutters are open and photon beams are delivered to users. The hardwa...

Recent experimental results of the Crystal-Barrel/TAPS collaboration at ELSA are presented. The experiments used a tagged photon beam incident on proton and neutron targets. Multiple photon final states were detected in the hermetically closed Crystal Barrel/TAPS detector setup, enabling the reconstruction of various neutral meson production channels. In addition to cross sections also photon b...

In compliance with the RDR [2], the baseline configuration for the positron source is based on a helical undulator passed by an electron beam of 150GeV. About 500m downstream the resulting photon beam hits a thin target, creates electron-positron pairs; the emerging positrons are collected and accelerated. The photon beam is circularly polarized, the spectrum is shown in Fig. 1 (left plot). The...

Deterministic photon-photon interactions are a long-standing goal in optical science. Using an atomic ensemble inside a cavity, we demonstrate the mutual cross modulation of two continuous light beams at the level of individual photons. The originally uncorrelated beams derived from independent lasers become anticorrelated, as evidenced by an equal-time cross-correlation function g^{(2)}=0.89(1...

This paper reports on the investigation of the double K-shell ionization of metallic aluminum induced by photon and electron impact. The experimental method consisted to measure the K hypersatellite spectra resulting from the radiative decay of double 1s vacancy states by means of high-resolution x-ray spectroscopy using a Bragg-type von Hamos crystal spectrometer. Measurements of the photon-in...

Background: Skyshine describes the radiation scattered by the atmosphere above a LINAC facility to a point on the ground. The aim of this study was to measure the skyshine photon dose rates from two different (9 MV and 18 MV) medical linear accelerators. Materials and Methods: The photon beam was directed upward (180° gantry position), with a maximum photon field size (40 × 40 cm2) at the isoce...

External photon beam radiotherapy is usually carried out with more than one radiation beam in order to achieve a uniform dose distribution inside the target volume and an as low as possible a dose in healthy tissues surrounding the target. ICRU Report No. 50 recommends a target dose uniformity within +7% and –5% of the dose delivered to a well defined prescription point within the target. Moder...

A Monte Carlo model of an Elekta Precise linear accelerator has been built and verified by measured data for a 6 and 10 MV photon beam running with and without a flattening filter in the beam line. In this study the flattening filter was replaced with a 6 mm thick copper plate, provided by the linac vendor, in order to stabilize the beam. Several studies have shown that removal of the filter im...