RF Separator

Pions are discriminated from muons and electrons with the help of a radio frequency separator (RFS) placed about 10 m downstream of the RMC target and phase-locked with the cyclotron RF. The RF separator exploits the velocity and subsequent time-of-flight differences between the pions and both the muons and electrons traveling with identical momentum to deflect the latter in a DC magnetic field crossed with a RF electric field. The time of flight (TOF) structure of the unseparated beam particles consisting of the $\pi ^-$, $e^-$, and $\mu^-$ particles is shown in Figure 3.2. The phase of the separator is adjusted so that the peak of the RF voltage coincides approximately with the pion time of arrival; force of the electric field ($\vec{E}$) is compensated by the $\vec{v}\times\vec{B}$ force of a horizontal DC magnetic field, where $\vec{v}$ is the velocity of the pion. The muons and electrons arrive at a delayed phase when the electric field is reversed. Then electric and magnetic forces work in the same direction to deflect these particles (19).