A new viewing chamber (figure 1) was used extensively on CTIX to study the interaction between the CT and various gas and mechanical targets. The optical imaging measurement is accomplished using a high sensitivity fast CCD camera. The imaging was accomplished using helium puffing in the viewing chamber (figure 2).
With helium gas puffing, a cloud of neutral helium is injected into the vessel moments before the primarily hydrogen compact toroid plasma collides with the helium target. The cloud of neutral helium becomes collisionally excited by plasma electrons, causing it to emit very brightly in the optical range and thereby become detectable to a variety of optical diagnostics, especially fast-imaging cameras. Without the helium gas puffing it is difficult to make a good image of the fully ionized pure hydrogen plasma, which emits only very dimly. With helium gas puffing, plasma density waves, current filaments and turbulent fluctuations have been detected using high sensitivity fast CCD cameras.