Revision 1

Accepted · first revision · record

Title: Chamber response in treatment-strength magnetic fields
Plain: Machines that image with magnetic resonance while treating place the detector inside a strong magnet, which bends the electrons it is trying to count. The resulting response change is not fully predictable.
Precise: Determine the magnetic-field correction factor for ionization chambers and solid-state detectors in fields of 3.5 to 15 kG, as a function of chamber axis orientation relative to the magnetic field and beam, cavity dimensions and gas, to below 0.5 percent. Include the electron return effect at tissue and air interfaces. An answer is a validated correction factor set and a primary standard valid in field.
Settled by: Water calorimetry in a magnetic field compared with chamber readings over the orientation range.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: partially-resolved
Status note: Calorimetric primary standards in magnetic fields were demonstrated by the early 2020s; a complete formalism across detectors and orientations remains incomplete.
Posed since: 2009