Rotating-wheel detector system for measuring millisecond half-life high-energy β emitters

In order to detect the 11 ms ¹²N activity produced in the pion single charge exchange reaction ¹²C(π⁺, π⁰)¹²N, a high-energy β-particle telescope was designed, constructed, and used successfully in the high-background field of γ rays, neutrons, and high-energy charged particles at LAMPF. A high-speed rotating wheel served both as a target and as a means of transporting the short-lived activity to an array of telescopes for counting. Monte Carlo calculations were carried out to optimize the design parameters of the telescope and to estimate counting efficiencies.