1. A study of the effect of salinity on pulsed arc discharge in water
Seok-geun Lee, Sooseok Choi, Kyoung-Jae Chung and Y. S. Hwang
Oct , 2010 ICC Jeju, Jeju, Korea
NUPLEX, Dept. of Nuclear, Seoul National University, 599, Gwanak-ro, Gwanak-gu, Seoul , Korea
3rd Euro-Asian Pulsed Power Conference
18th International Conference on High-Power Particle Beams
LSG_NUPLEX-Oct. 2010

2. Outline Introduction Experimental setup Experimental results
- pulsed arc discharge system
- research motivation
Experimental setup
- pulsed arc discharge system with voltage, current probe
Experimental results
- relation of pressure peak and energy
- voltage, current characteristic in sea water
- voltage, current characteristic in experimental condition
- pressure to conductivity
Conclusion & future works

3. Pulsed arc discharge system
High voltage electrode
Pressure gauge
100 mm
Before discharge
At discharge
Tungsten electrode
Arc channel formation
Electrode gap
(5 mm)
Anode f8
Cathode

4. Arc discharge in sea water to generate pressure wave
Research motivation
Arc discharge in sea water to generate pressure wave
Pressure wave
generation and propagation
1. Energy transfer from the capacitor to arc channel
2. Expansion plasma-water interface
3. Pressure wave generation and propagation
What is effect on generating higher pressure wave in sea water

5. Research motivation Currents leak through the sea water
Sea Water Chamber
(Φ100 / L600, Tube)
Charging Switch
Discharging Switch
High Voltage
Power Supply
( ~ 20 kV)
Capacitor
( ~ 0.5 ㎌) V
I total
I load
I loss = I total – I load
Max. loss current
Currents leak through the sea water
Power loss by leakage current
Find out the relation of salinity, power transfer efficiency and pressure wave on pulsed arc discharge in water

6. Experimental setup Sea Water Chamber High Voltage electrode - Anode
Ground electrode
- Cathode
Viewport
Discharge
Channel
Camera
Pressure Gauge
Positively Charged
High Voltage Capacitor
Discharge Switch
Rogowski Coil 2
(Load Current)
Rogowski Coil 1
(Total Current) V
Voltmeter
(Load Voltage)
100 mm

7. Arc discharge in sea water
Camera Setting
Used camera & lens: Canon 50D, Pentax 200 mm
Exposure time: 1 second
Adjustment of radiation intensity:
F8, F8 with ND400 Filter
· At 16kV, arc channel does not develop
· At 18kV, arc channel does not always develop
- discharge irregular
· At 20kV, arc channel develop at all times
16kV
18kV
20kV F8
Arc channel formation
F8 with
ND400 Filter

8. Determinant parameter to generation pressure wave
Peak pressure wave is proportional to square voltage (P∝V2)
Peak pressure wave is proportional to stored energy in capacitor (E=½CV2)

9. Experimental condition table : conductivity
Goal conditions
Conductivity
(S/m)
Resistivity
(Ω∙m)
Salinity
(%)
0.0 S/m
232
0.00
0.5 S/m
0.494
2.02
0.3
1.0 S/m
1.03
0.97
0.63
1.5 S/m
1.507
0.663
0.94
2.0 S/m
1.935
0.516
~1①
(Over Range)
Sea water
~4.8
~0.2
3.5
In one condition, experiments were performed 10 times.
Charging voltage: 14kV (An arc channel is formed in pure water at 14kV.)
① conductivity measuring instrument(TOA, CM-14P) detection limit: 2.0 S/m, 1 % considered

10. Comparison of voltage, current characteristic in different condition
Charging voltage : 14kV
Pure water
conductivity: S/m
Sea water
conductivity: ~4.8 S/m
An arc channel is developed at 14kV in experiment condition.
An arc channel is not developed at 14kV in sea water.
A current is lower in pure water than in sea water.
A resistivity is relatively higher in pure water than in sea water.

11. Tendency of discharge voltage to salinity
Charging voltage : 14kV
The discharge voltage is decreasing steeply with increasing conductivity.
The current rising time is shorten with increasing conductivity.
Current rising time

12. Tendency of discharge current to salinity
Charging voltage : 14kV
0 S/m ( S/m)
2 S/m (1.935 S/m)
Current leakage in 2 S/m
Current leakage in 0 S/m
Before current peak is shown, current difference (I total- I load) is higher in salinity water(2 S/m) than in pure water(0 S/m).
It is considered that current leakage is high at high conductivity condition.

13. Plot of peak pressure to conductivity
Charging voltage : 14kV ①
A weak pressure wave is generated at high conductivity condition in the same stored energy(E=½CV2).
The higher a conductivity is reached,
the weaker a pressure wave is generated.
The result shows that weak pressure wave is generated by energy loss caused current leakage.
① The strong pressure wave is generated enough to damage electrode cover in pure water.
then, number of experiments is low

14. Conclusions Conclusion
The strength of pressure wave is proportional to discharge energy stored energy in capacitor.
The current leakage through the salty water is occurred out because of high conductivity.
Energy loss through the salty water can make a strength of pressure wave weak.
Future works
necessary circuit analysis of arc discharge under water
calculation of energy loss caused by current leakage