title: Megavoltage bremsstrahlung end point voltage diagnostic.
abstract: In a material, a beam of x rays is accompanied by various kinds of secondary radiation, including Compton electrons from collisions between the x rays and the material's electrons. For megavoltage bremsstrahlung in air, many of these Compton electrons are forward-directed and fast enough to be deflected outside the beam's edge by a magnetic field perpendicular to the beam. At the beam's edge, the dose from the deflected Compton electrons has a pattern that depends on the radiation's end point energy. Dose patterns measured with radiochromic film on a nominally 1 and 2 MV linear accelerator agree reasonably well with the corresponding Monte Carlo computations. With further development, the dose pattern produced outside the beam by such a sweeper magnet could become a noninvasive way to monitor megavoltage bremsstrahlung, when the end point energies are difficult to determine with other methods.
authors.affiliation: Army Research Laboratory, 2800 Powder Mill Rd., Adelphi, Maryland 20873, USA.
authors.forename: T
authors.initials: T
authors.lastname: Feroli
authors.forename: M S
authors.initials: MS
authors.lastname: Litz
authors.forename: G
authors.initials: G
authors.lastname: Merkel
authors.forename: T
authors.initials: T
authors.lastname: Smith
authors.forename: N R
authors.initials: NR
authors.lastname: Pereira
authors.forename: J J
authors.initials: JJ
authors.lastname: Carroll