Chemistry Reference
In-Depth Information
Gas in
Tip of the needle
Needle electrode
to PMT
Bubble
Gas bubble
Fiber-optic cable
Water
Pulsed
power
Water
Disk electrode
Disk electrode
+
(a)
(b)
FIGURE 8.58
(a) Schematic diagram of the experimental arrangement showing the bubble
around the needle electrode with the disk electrode immersed in water. Gas is fed through the
needle and a stationary bubble forms around the tip of the needle. (b) A photograph of the
bubble and the electrodes.
L
2
L
n
A current probe
L
1
HV probe
Switch
Water
system
C
1
C
2
C
3
C
n
+1
+ HV
(DC)
Scope
R
m
Matching
R
Charge
HV probe
FIGURE 8.59
Electricalsystem:DCpowersupply,thyratronswitch,Blumleinpulse-shaping
network with 35 W matching resistor (
R
m
), and voltage and current probes.
electrode is a stainless steel disk. The distance between the electrodes can be varied
between essentially 0 and 25 mm.
The electrical power delivery system consists of a dc high-voltage power supply
and a pulse-shaping network (Figure 8.59). A 60 kV, 10 mA power supply charges
the pulse generator. A thyratron switch delivers the voltage pulse. The thyratron is
triggered manually delivering single pulses at intervals from 30 s to several minutes.
The Blumlein pulse-shaping network delivers a 1 ms rectangular pulse in the 3-30 kV
range. Optical emissions of the OH band (309 nm) and the Ar lines (765 nm) from
inside the bubble are sent to a cooled photomultiplier tube (PMT) with a temporal
resolution of 2 ns. All current, voltage, and PMT data are recorded by a digital
oscilloscope. De-ionized water was used with a conductivity of 1.2-1.5 mS/cm, a
pH of 5.0, and a temperature of 21
◦
C. Experimental results reported here include
measurements of optical emissions and the discharge current for various sizes of Ar
and O
2
bubbles.
The second experimental setup shown in Figure 8.60 is a reactor that was devel-
oped for water disinfection applications. This system includes a gas flow controller
and water pump. The power supply employs two rotating spark-gap switches to
generate high-voltage pulses and a 40 kV DC power supply. This reactor employs
a set of mesh electrodes in a plane-to-plane configuration connected sequentially
either to high voltage or to ground. A forced oxygen bubble flow passes vertically
through the electrode system along with the flow of contaminated water from a
