Answer: quadrupoles

AnswerCrossword Clue
quadrupolesQUADRUPOLE, a system composed of two dipoles of equal but oppositely directed moment
quadrupolesA device using such an arrangement directed at one point to focus beams of subatomic particles
quadrupolesA distribution of electric charge or magnetization consisting of four equal monopoles, or two equal dipoles, arranged close together with alternating polarity and operating as a unit