A wide band photon beam at the Fermilab Tevatron to study heavy flavors

For many years, the use of high energy photon beams has been recognized as a good technique for the investigation of charmed particles [1]. The cross section is a relatively large fraction (approximately 1%) of the total hadronic cross section at high energies. The challenge was to develop a high energy and high intensity beam that produces enough charmed particles to obtain very high statistics so that one can answer detailed questions about charm production and decays. The Fermilab wide band photon beam is an attempt to meet that challenge. The beamline configuration and capabilities have evolved since the test run in 1985 and the first physics run in 1987-88. For the 1990-91 data run, improvements were made to increase the photon yield and to improve the photon energy tagging resolution. Althought the main emphasis of this report is on the original 1985-88 beam configuration, two fully operational upgrades for the 1990-91 run, namely the incident electron beam momentum tagging spectrometer and the LD2 primary beam target, are described. The beam was also given the capability of transporting simultaneously e+ and e- beams. The performance of this ''double-band'' configuration was studied briefly duing the 1990-91 running period and will be described in a future publication. A description of the Fermilab E687 spectrometer utilizing this photon beam facility has recently been published [2].