Energy distributions from a racetrack microtron measured with a magnetic spectrometer

Energy spectra of accelerated electron beams from a racetrack microtron were measured using a magnetic spectrometer. The spectrometer utilized a 90 degrees dipole magnet. A ray-tracing program was developed to determine the slit positions of the spectrometer based on a detailed map of the magnetic field measured at field strengths corresponding to about 20 and 50 MeV. The total a priori uncertainty (previously often called systematic or class B uncertainty) of the measured most probable energy Ep is 0.22% (one approximate standard deviation) and the a posteriori uncertainty (previously often called random or class A uncertainty) is 0.04% (1 sigma). The estimated energy resolution (delta E/E) of the spectrometer is 4 x 10(-4). Spectral energy distributions of the electron beam were measured at a Ep = 21.1 and 51.6 MeV, and the obtained full width at half-maximum of the energy distributions were 53 and 34 keV, respectively. All the measurements were performed in vacuum to minimize the influence of electron energy loss and scatter.