Studies of quadrupole lenses.

摘要

Electrostatic or magnetic quadrupole lenses are used for focusing beams of accelerated charged particles. At the Van de Graaff accelerator of the University of Massachusetts Lowell a magnetic quadrupole doublet requiring a vacuum-tube-based high voltage power supply was installed along the beam line. A drawback of this quadrupole system is the inconvenience of the high-voltage power supply (350 V). This doublet was redesigned for use with a low-voltage power supply (20 V) by replacing the coils of the lenses. A technique was developed to measure the magnetic flux of the new coils to ensure that each coil produced the same magnetic field for the same current. Also, geometrical measurements of an electrostatic quadrupole doublet that is currently available at this accelerator were taken. From these measurements the focal points for charged particle beams of different energies, charges, and masses and for different potentials applied at the electrodes were calculated.