The β spectrum from the fission products of 252Cf has been measured using a flat-field magnetic spectrometer. The active entrance aperture to the magnetic field region consisted of an annular plastic scintillator to veto slit scattering and a thin wire chamber to signal electrons on a good trajectory. The electrons exited the magnetic field through a position sensitive wire chamber capable of three dimensional track reconstruction. The energy calibration and relative efficiency of the spectrometer were determined using the β decays of 12B, 20F, and 90Sr. The shape of the β spectrum from 252Cf was measured at 5 field settings and the results combined to form a complete spectrum from 2.0 to 9.0 MeV (β total energy) with a total error of 3% at 3 MeV, rising to 6% at 5 MeV, 9% at 7 MeV, 15% at 8 MeV and 25% at 9 MeV. This experiment was motivated by the need to know the ν̅e spectrum from the β decays of fission products in order to interpret the results of reactor based neutrino oscillation experiments. The ν̅e spectrum can be calculated directly or converted from a measured β spectrum. This experiment is an additional check of these calculations and constitutes a complementary check of previous measurements of the β spectrum from other fissioning nuclei 235U, 239Pu, and 241Pu.We find a softer spectrum fewer β's at high momenta) than predicted by the calculations, in agreement with earlier measurements in other nuclei by Schreckenbach et al.. but in disagreement with earlier measurements by Borovoi et al. in 252Cf. Possible sources of the disagreement with the calculations and the earlier experiment and possible improvements to the experiment are discussed.
