ENERGY CALIBRATION OF TANDEM ACCELERATORS

The beam energy homogeneity, stability and reproducibility of a model MP tandem Van de Graaff accelerator has been investigated. The 90° analyzing magnet system was calibrated using a number of (p,n) thresholds whose proton energies are known absolutely in the range from 4 to 10 MeV. The linearity of the beam momentum analysis system was then checked for higher magnetic rigidities by observing the 2H(16O, n)17F neutron threshold for several different 16O ionic charge states. The magnet calibration constant, obtained from a least-squares different reactions, was reapplied to the data to obtain a new set of self-consistent energies for the calibration reactions themselves. This procedure, which relies on the assumption that the data are all measures of the same calibration constant, results in smaller statistical errors for the calibration energies than those previously cited. Measurements were then extended using the linearity of the analysis system as established by the 2H(16O,n)17F measurements to include the 12C(p,n)12N, 24Mg(p,n)24Al, 28Si(p,n)28P, 32S(p,n)32Cl and 40Ca(p,n)40Sc neutron thresholds at energies of 19.658 ± 0.005 MeV, 15.286 ± 0.003 MeV, 15.669 ± 0.004 MeV, 13.899 ± 0.014 MeV, and 15.491 ± 0.003 MeV, respectively. With the exception of the 32S(p,n)32Cl reaction, for which there are target difficulties, these thresholds provide the first series of calibration points in the energy range from 10 to 20 MeV. © 1969.