Arc cathode spots: Their mechanism and motion

Arc spots are usually highly unstable and jump statistically over the cathode surface. In a magnetic field parallel to the surface, they preferably move in the retrograde direction, i.e., opposite to the Lorentzian rule. If the field is inclined with respect to the surface, the spots drift away at a certain angle with respect to the proper retrograde direction (Robson drift motion). The phenomenon are explained by a unique stability theory.<
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