At MIT, development of electron accelerators for research in nuclear physics goes back to 1951 when a 17 MeV linac was constructed by the Laboratory for Nuclear Science and Engineering and the Research Laboratory for Electronics. As a research tool, this machine was used for over a decade, primarily for a long and productive series of photofission and photoneutron experiments. By the early 1960's, however, it was clear that further experimental progress required electron beams of higher energy, current and precision. A formal proposal was submitted in 1964 to the U. S. Atomic Energy Commission and Congressional authorization for construction funding was granted in 1966.
In 1967, with the assistance of Massachusetts Congressman William H. Bates, then on the Joint Committee on Atomic Energy, MIT acquired the present site in Middleton permission to proceed with actual construction was obtained in the same year. A comprehensive review of scientific priorities was undertaken in the 1967 Summer Study at MIT and a decision was made to devote available funds to the development of a high resolution electron scattering facility with a single spectrometer. From the outset, the Energy Loss (dispersion matching) Spectrometer System (ELSSY) produced data of unprecedented resolution. Although the facilities for the purpose were far from ideal, in addition to high-resolution electron scattering, there was from the earliest days a small program for photoreactions. Indeed, the first experiment conducted at Bates was on the 12C(gamma, pi-minus) reaction using an assembly of improvised equipment in the 14° experimental area. This work began with a series of table-top experiments involving the threshold production of charged and neutral pions, and was followed by the development and use of prototype spectrometers for neutral and charged pion measurements in the 14° area. These in turn served as the basis for construction of an opening-angle pi zero spectrometer and the Medium Energy Pion Spectrometer (MEPS) in the South Experimental Hall. A similar evolution of photoproton spectroscopy occurred, which began with the early use of ELSSY, and included work with the One Hundred Inch Proton Spectrometer (OHIPS). Another addition to the facility was the BigBite spectrometer, so named because of its very large momentum acceptance (~ 50%). It was used extensively in deep inelastic electron scattering experiments, as well as the principal part of the deuteron channel for the tensor polarization measurement.
The Laboratory was made available as broadly as possible to experimentalists throughout the nation and the world. Toward this end, a Program Advisory Committee and the Bates Linear Accelerator Users Group were established in 1972. The contributions of the users to the Laboratory's development were continuous and essential. The Boston University group carried a major burden in the development of the pi zero spectrometer in collaboration with Catholic University and MIT. The Rensselaer Polytechnic Institute group participated in all phases of the charged-pion spectroscopy work, including provision under a subcontract to Bates of the quadrupoles and parts of the focal plane detector for MEPS. The Glasgow University Group made important contributions to development of the photoproton program. A group from the University of Massachusetts developed the 180° scattering system, and construction of the polarized electron source was started by a group from Yale, CUNY and Syracuse. Contributions included a gas Cherenkov counter for OHIPS, built by a group from Argonne National Laboratory and a major detector upgrade for ELSSY led by a University of Massachusetts group, with contributions from CEBAF and Saclay, an Out-of-Plane Spectrometer System , initiated by a group from the University of Illinois, and a Focal Plane Polarimeter for OHIPS, built by a University of Virginia and William & Mary collaboration. A major capability was added in the South Experimental Hall. This device, the Bates Large Acceptance Spectrometer Toroid (BLAST), was a large acceptance detector tailored for the full exploitation of spin observances in electromagnetic processes.