Related Experiment Video
Updated: Mar 19, 2026

X-ray Beam Induced Current Measurements for Multi-Modal X-ray Microscopy of Solar Cells
Published on: August 20, 2019
The phenomenon of drop in output at larger field sizes for telecobalt units
Sukhvir Singh1, Ajay K Singh1, Manoj K Semwal2
1Department of Radiation Oncology, Army Hospital (R&R), Delhi Cantonment, New Delhi, 110010, India.
Abstract:
It is known that the output factors (OPFs) for external-beam radiotherapy units increase with field size due to increased scattered radiation from the collimator system. Saturation in the OPF value is generally reported beyond approximately 30 × 30 cm(2). For the first time, to the best of our knowledge, we report on a drop in OPF values, although marginal, measured for a telecobalt machine beyond the 38 × 38 cm(2) field size. We believe that reporting and explaining the results will lead to a better understanding of the scatter composition of the radiation from telecobalt machines. This also has the potential to impact the estimation of low dose regions in patients, in addition to being a purely scientific inquiry. We used Monte Carlo (MC) simulations to validate the measured values. The MC data showed that the decrease in OPF was due to decreased scatter from the machine head.
Related Concept Videos
Instrument Transformers
Field Effect Transistor
Lossy Lines and Overvoltages
Attenuation
When constant series resistance and shunt conductance are present, voltage and current equations are modified. The propagation constant indicates that voltage and current waves consist of both forward and backward traveling components. These waves attenuate as they propagate, with the attenuation factor related to the resistance and conductance. In a...
Induced Electric Fields
Induced Electric Fields: Applications
Boundary Conditions: Lossless Lines
At the receiving end, the boundary condition states that the voltage equals the product of the receiving-end impedance and current. This relationship is expressed as a function of the incident and...

