High resolution spectrometers for electron scattering

In this article we discuss high-precision, high-resolution magnetic spectrometry as applied to electron scattering at intermediate energies (⩽1 GeV). Beginning with a brief summary of some aspects of the electron-scattering process, we develop the specifications for systems capable of achieving precision of about 1% in cross-section and 10 −4 in momentum resolution. Following a brief outline of the general formalism of magnetic optics, we describe in considerable detail the MIT DD electron energy-loss spectrometer including: (1) general optical specifications, (2) mechanical construction methods and special features, (3) focal plane instrumentation, and (4) examples of performance to date. In a concluding section we make some comparisons with more recent systems and indicate where further improvements in the MIT system may possibly be achieved.