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plasma is still not known exactly. Experiments per-
formed by our group has shown that the mm wave ra-
diation is detected by a change in the plasma current
for commercially available discharge lamps, however
the same experiments when performed with a home-
built discharge chamber were inconclusive suggesting
that gas composition, pressure as well as electrode
composition all play an important role in the detec-
tion of the radiation (Alasgarzade et al., 2016). To
better understand the role these parameters play the
GDD simulated using the parallel 1d3v PIC / MCC
code previously developed (Kusoglu-Sarikaya et al.,
2016) and the results compared with controlled ex-
periments performed in the laboratory. These results
will aid in understanding the plasma parameters that
dominate the detection observed with commercial de-
tectors. This will be done later by adding the energy
associated with the radiation to the plasma allowing
to better understand the physical reactions of the par-
ticles inside.
2 GLOW DISCHARGE CHAMBER
Commercially available neon indicator lamps, namely
glow discharge detectors (GDDs) have been our
primary research interest since they are proven to
be cost-effective, low noise, fast response mm-
wave/Terahertz (THz) detectors (Rozban et al., 2008;
Abramovich et al., 2007). Previously, we have in-
vestigated various GDDs in terms of their speed, fre-
quency response and polarization dependence based
on their orientation with respect to the incident light
(Alasgarzade et al., 2016). In order to investigate con-
tributing effects to mm-wave/THz detection mecha-
nism such as the effects of discharge breakdown and
glow scenarios for various inert gasses as well as var-
ious Penning mixtures, a small plasma vacuum cham-
ber is designed and built, shown in Fig. 1 and Fig. 2.
A breakdown is achieved in gas mixture by apply-
ing a bias DC voltage to the electrodes. Under suf-
ficient conditions the electric field of the modulated
incident radiation increases the total electric field and
can generate variations in the plasma current. The ef-
fect of incident radiation on the plasma current de-
pends on several parameters such as plasma region,
type of the gas mixture, electrode geometry and po-
larization of radiation. Based on the measured dis-
charge current values, we expect to operate within the
abnormal regime of the glow, before the arc region
(Braithwaite, 2000). In this region the electric field of
the incoming mm wave radiation, when aligned with
the applied DC field is expected to increase the rate of
excitation collision (Rozban et al., 2008).
Figure 1: The gas mixer system designed and built to mix
the inert gases inside the home-built chamber allows up to 3
different gases to mixed under normal (partial atmosphere)
to low vacuum (0.01 Torr) conditions. The gases are mixed
inside a housing before being sent into the chamber.
Figure 2: Plasma Discharge Chamber. The electrode sepa-
ration is controlled using a micrometer.
The vacuum chamber having a dimension of
roughly 10x10x10 cm
3
, has two quartz windows with
40 mm diameter that allow the transmission of inci-
dent THz radiation through the DC glow discharge
between the electrodes. Electrodes with different ge-
ometries can be used. The electrode separation can be
controlled with 10 µm resolution and can be extended
up to 2 cm. Also the chamber admits a floating probe
allowing the measurement of changes in plasma cur-
rent and plasma voltage. There are two feedthroughs
on the top of plasma chamber. One of them is con-
nected to the gas distribution system and the other is
connected to the Multi-Gauge Controller (Varian) for
measuring pressure inside chamber instantaneously.
With the rotary vane pump system, the pressure in-
side chamber can be reduced to 10
−2
torr.
After sealing the pump line, routine operations of
plasma glow are achieved with a backfill pressure of
25 torr for pure Neon Gas (99.999%). The breakdown
is achieved at around 350 V for a 1 mm separation be-
tween anode and cathode. Compared to commercially
available Neon lamps these values are thought to be
much higher. In commercially available Neon lamps
typically discharges are obtained for breakdown volt-
ages 80-150 V for similar electrode spacing and pres-
sure. Thus the commercially available Neon lamps
Parallel 1d3v Particle in Cell/Monte Carlo Collision (PIC/MCC) Simulation of a Glow Discharge Millimeter Wave Detector
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