|Scientific news from division 6|
|Completion of the world’s largest accelerator facility for dosimetry in radiation therapy
For the success of a radiation therapy it is also decisive that the radiation dose is applied with sufficient accuracy. This dose is measured as absorbed dose to water in the unit gray
The realization and dissemination of the gray is one of PTB’s main tasks. The primary standard measuring device of Germany is a water calorimeter which measures the temperature rise of the water under
To realize the gray for irradiation conditions which are as practice-related as possible, PTB now has two clinical electron accelerators of the type "Elekta Precise Treatment SystemTM" at its disposal. With these accelerators, six reference fields for photon radiation and ten reference fields for electron radiation are available. The energy range extends from
In its fight against cancer, medicine is constantly developing new irradiation techniques. They generate irregularly shaped irradiation volumes which adapt the irradiated volume with an ever increasing exactness to the form of the tumour in order to treat sensitive organs and healthy tissue with maximum care. Examples are tomotherapy or "
An electron linear acclerator -
Accordingly, the research accelerator serves two irradiation
By means of deflection magnets and diaphragms, quasi monoenergetic electron beams can be generated, with spectral widths down to
The electron current is measured contact-free with toroidal beam current transformers which have been developed at CERN. At present, they are regarded as the most exact measuring instruments for this application. For energy determination, the electron beam is deflected by 180° through a homogeneous magnetic field in spectrometers which have been especially designed for this purpose. The electron energy is obtained from the path diameter and the value of the magnetic field strength.
Now, the intended scientific operation has been started on all three accelerators. Although work is focussed on clinical dosimetry, other subjects are not excluded. Hamburg University, for example, studies at the research accelerator radiation damages in silicon diodes which are used at CERN in