Efficient proton ring trapping in an ion ring experiment

In an 8 kG magnetic mirror, 400 keV proton rings, containing up to 3 x 1015 protons and 0.2 kJ energy, have been trapped. The trapping is accomplished by injecting a rotating proton ring through a 1 μsec rise-time, 1.4:1 pulsed mirror coil. Negligible loss occurs through the 1.45:1 static downstream mirror after the first bounce, when > or approx. =90% of the injected beam is reflected. The pulsed upstream mirror traps > or approx. =70% of the returning protons, after which there is very little particle loss for the first four ring bounces in the mirror well. Ring decay then increases as a result of slowing down and charge exchange in the >50 mTorr H2 background, and the ring is observable for >10 bounces, or > or approx. =5 μsec