400 MeV upgrade for the Fermilab linac

Fermilab has plans for a comprehensive accelerator upgrade to open new possibilities for both the fixed target and collider experimental programs. An early step in this program is to increase the energy of the linac from 200 to 400 MeV by replacing the last four of its nine 201-MHz Alvarez tanks with 28 805-MHz side-coupled cavity chains operating at about 8-MV/m average axial field. The principal purpose is to reduce the incoherent space-charge tuneshift at injection into the booster which currently limits both the brightness of the beam, an important determinant of collider luminosity, and total intensity to produce both the antiprotons for the collider and the beams to fixed-target experimental areas. Other consequences of higher booster injection energy expected to contribute to some degree to higher intensity limits and improved operational characteristics included improved quality of the guide field at injection, reduced frequency swing for the RF systems, and smaller emittance for the injected beam.<>