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FIZIKA A 11 (2002) 2 , 81-90
 
MEASUREMENTS OF THE BREAKDOWN POTENTIALS FOR DIFFERENT CATHODE
MATERIALS IN THE TOWNSEND DISCHARGE
M. ALI HASSOUBAa, F. FAHMY ELAKSHARb and A.
ABUWALI GARAMOONb
aPhysics Department, Faculty of Science, Benha University,
Egypt
E-mail address: hassouba@yahoomail.com
bPhysics Department, Faculty of Science, Azhar University,
Egypt
Received 22 October 2001; Revised manuscript received 9 October 2002
Accepted 25 October 2002 Online 07 February 2002
The breakdown potentials have been measured for argon and helium discharges using three
different cathode materials: aluminium, silver and magnesium. The measurements show that
lower breakdown potentials are associated with lower work function of the cathode
material. For the three different cathodes, the secondary ionization coefficients have
been estimated using the measured values of the breakdown potentials and the first
ionization coefficient, in the range 0.60 to 2.25 V/[Pa cm] (80 to 300
V/[torr cm]) for Ar discharge and in the range of 0.15 to 1.80 V/[Pa cm] (20 to
240 V/[torr cm]) for He discharge. The minimum breakdown potential has been found at
(pd)min = 80 Pa cm (0.6 torr cm) in Ar discharge and at 530
Pa cm (4.0 torr cm) in He discharge.
PACS numbers: 51.50.+v, 52.80.Dy
UDC 537.525, 531.742.34
Keywords: discharge in gases, He, Ar, breakdown potentials, different cathode
materials, secondary ionization coefficients
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