UPGRADING PROGRAM FOR THE FN TANDEM AND AMS SYSTEM AT PRIME LAB

A coordinated upgrading program is underway at PRIME Lab with the goal of permitting isotopic ratio measurements throughout the periodic table with systematic errors below 1%, detection limits at or below 10(-15) and a capacity of over 3000 samples per year. The FN tandem upgrade will include spiral-inclined titanium electrode acceleration tubes, dual Pelletron chains, shielded column grading resistors, a longer and larger diameter stripper with both gas recirculation and active pumping, and a 300-foil stripper. The ion source system will provide for tandem injection at energies as great as 130 keV and includes a non-dispersive energy/momentum analysis pair having M/DELTAM above 300 together with 5 Hz mass switching. The 90-degrees electrostatic analyzer will have double-focusing spherical geometry. The 90-degrees magnetic analyzer will have two independent poles to provide four curved boundaries for correction of aberrations. An electrostatic quadrupole triplet will prepare the beam for injection into the tandem and correct any distortion. Following the tandem, an electrostatic quadrupole doublet will be substituted for the existing magnetic lens. This lens will be located close to the tank base for improved optical matching of the existing 90-degrees magnet. The pole width of the existing 90-degrees magnet is adequate for allowing masses 35, 36 and 37 to be directed into separate cups at constant field. Computer control will be added to all power supplies to permit polling of all parameters, unattended operation, and rapid conversion between isotopic systems. The upgrade will begin in the fall of 1993, starting with the tandem.