# How ionized is the plasma in a Crookes tube

How ionized is the plasma in a Crookes tube, at $10^{−6}$ to $5 \times 10^{−8}$ atmosphere ($7 \times 10^{−4}$ – $4 \times 10^{−5}$ torr or 0.1–0.005 pascal). Under any of these circumstances is it fully ionized?

• To calculate that one would need to know the plasma density, but from my experience with gas discharges, the degree of ionization is likely to be below 1 % – Alf May 3 '17 at 6:28
• It is really hard to 'completely' ionize a plasma - the electrons and ions are attracted to each other and are occupying the same volume (I'll exclude the sheath here). If the plasma is glowing, there is recombination taking place, so it is not fully ionized. – Jon Custer May 3 '17 at 13:05
• But can't ions continuously gain and lose electrons while having lost their electrons and thus being ionized the entire time? Also is is it mostly ionized then? – Maxwell Baker May 5 '17 at 20:55