To generate energy-efficient

reactive

homogeneous

and stable atmospheric pressure plasma sources

Ar dielectric barrier discharge（DBD） was excited by nanosecond pulsed power supply

and H2 O was added to enhance plasma reactivity. The discharge characteristics of the nanosecond pulsed Ar DBD with H2 O addition were investigated by electrical and optical diagnoses. The discharge uniformity was quantitatively calculated by the Gray Value Standard Deviation method

and the electrical parameters were studied by an equivalent electrical model. The results show that the ns-pulsed Ar DBD with 0%～0.2% H2 O content is in a uniform state. When the H2 O content is increased further

the added H2 O absorbs electrons and distorts the space electric field

resulting in bright filaments in space and the decrease of discharge uniformity. And the excessive H2 O will render the discharge to be extinguished. Since the addition of a small amount of H2 O can promote the Penning ionization process in the plasma

the transported charges

average discharge power and energy efficiency increase with the increase of H2 O content first

reach a maximum value at 0.1% H2 O content

and finally decrease with the increase of H2 O content. The plasma reactivity is characterized by the emission spectrum intensities of OH and Ar lines. It is found that

at 0.1% H2 O content

the intensities of OH and Ar lines reach the maximum values. The ratio of emission intensities of Ar lines indicates that the electron energy increases with the increase of H2 O content

reaches a maximum value at 0.1% H2 O content

and then drops.