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3. Paschen Law
FB242 Gas discharges: physical mechanisms and applications




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https://www.tf.uni-kiel.de/matwis/amat/elmat_en/kap_2/backbone/r2_3_2.html
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Paschen´s curves for different gases



Paschen´s curves for different cathode materials



disch5



Paschen´s curve for air
Brekdown voltage for ambient air is approximately 25 kV/cm


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     High voltage el. insulation
Paschen





Vacuum breakdown



Short ~μm electrode distances
Plot of the breakdown voltage as a function of the electrode gap spacing d for ambient air at
atmospheric pressure using different cathode materials
D B Go and A Venkattraman 2014 J. Phys. D: Appl. Phys. 47

In (multivire) proportional chembers argon-methane gas mixture is used to prevent photoionization
(fast deexcitation of Ar*) –
Problem with „plasmachemical“ polymer deposition at the cathodes

Malterov´s  emissin – field emission from oxide coated surfaces autoemisia occuring at relatively
low fields


Paschen law – effect of magnetic field
a28fig03


Magnetron sputtering



           Penning source of ions
Synergic effect of mag. field and „hollow cathode“


Ion plasma engine (ion thruster) for spacecrafts
https://en.wikipedia.org/wiki/Ion_thruster
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Penningova ionizácia
nIonizačné energie:
nHe (24,59 eV)
nAr (15,4 eV)
nSF6 (15,3)
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Lieberman and Lichtenberg, Principles of Plasma Discharges, Wiley 2005.
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He +  e  →  He*
He* +  2 He → He*2 + He
He*2 + X → 2He + X
He* +  N2 → N+2 + He + e
He*2 +  N2 → N+2 + 2 He + e
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„Pseudospark“ HV switchers



Paschen's Curve, breakdown voltage vs. pressure-distance product.



Pseudospark - sourced electron beam for the generation of X-rays & THz radiation A.W. Cross 1, H.
Yin 1, D. Bowes 1, W He 1, K. Ronald 1, A.D.R. Phelps. - ppt download


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