| Topic: |
Science > Physics |
| User: |
"James Stokes" |
| Date: |
13 Aug 2005 09:06:09 PM |
| Object: |
Potential difference in a capacitive rf discharge |
A capacitively coupled radio frequency discharge consists of two electrodes
with one electrode capacitively coupled to a radio-frequency power source
and the other electrode grounded, with a quasi-neutral plasma formed
between. Since the discharge chamber is also grounded, the grounded probe
has much larger surface area than the powered probe. I'm trying to
understand why this difference in surface area results in the establishment
of a net potential difference between the electrodes, allowing negatively
charged microparticles to levitate against gravity above the lower (powered)
electrode.
Thanks.
James
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| User: "night soil dalits" |
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| Title: Re: Potential difference in a capacitive rf discharge |
13 Aug 2005 09:49:42 PM |
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"James Stokes" <someone@microsoft.com> wrote in message
news:lGxLe.83170$oJ.13787@news-server.bigpond.net.au...
A capacitively coupled radio frequency discharge consists of two
electrodes
with one electrode capacitively coupled to a radio-frequency power source
and the other electrode grounded, with a quasi-neutral plasma formed
between. Since the discharge chamber is also grounded, the grounded probe
has much larger surface area than the powered probe. I'm trying to
understand why this difference in surface area results in the
establishment
of a net potential difference between the electrodes, allowing negatively
charged microparticles to levitate against gravity above the lower
(powered)
electrode.
Thanks.
James
RF is Alternating, a static field will not be established, nothing will
levitate.
.
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| User: "James Stokes" |
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| Title: Re: Potential difference in a capacitive rf discharge |
13 Aug 2005 09:57:17 PM |
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"night soil dalits" <invalids@invalid.com> wrote in message
news:42feb144$0$16783$892e7fe2@authen.white.readfreenews.net...
"James Stokes" <someone@microsoft.com> wrote in message
news:lGxLe.83170$oJ.13787@news-server.bigpond.net.au...
A capacitively coupled radio frequency discharge consists of two
electrodes
with one electrode capacitively coupled to a radio-frequency power source
and the other electrode grounded, with a quasi-neutral plasma formed
between. Since the discharge chamber is also grounded, the grounded probe
has much larger surface area than the powered probe. I'm trying to
understand why this difference in surface area results in the
establishment
of a net potential difference between the electrodes, allowing negatively
charged microparticles to levitate against gravity above the lower
(powered)
electrode.
Thanks.
James
RF is Alternating, a static field will not be established, nothing will
levitate.
Interestingly, this is not the case. Negatively charged dust particles are
routinely observed to levitate in the sheath region between the plasma bulk
and the powered electrode.
.
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| User: "night soil dalits" |
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| Title: Re: Potential difference in a capacitive rf discharge |
13 Aug 2005 10:18:45 PM |
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"James Stokes" <someone@microsoft.com> wrote in message
news:hqyLe.83580$oJ.33682@news-server.bigpond.net.au...
"night soil dalits" <invalids@invalid.com> wrote in message
news:42feb144$0$16783$892e7fe2@authen.white.readfreenews.net...
"James Stokes" <someone@microsoft.com> wrote in message
news:lGxLe.83170$oJ.13787@news-server.bigpond.net.au...
A capacitively coupled radio frequency discharge consists of two
electrodes
with one electrode capacitively coupled to a radio-frequency power
source
and the other electrode grounded, with a quasi-neutral plasma formed
between. Since the discharge chamber is also grounded, the grounded
probe
has much larger surface area than the powered probe. I'm trying to
understand why this difference in surface area results in the
establishment
of a net potential difference between the electrodes, allowing
negatively
charged microparticles to levitate against gravity above the lower
(powered)
electrode.
Thanks.
James
RF is Alternating, a static field will not be established, nothing will
levitate.
Interestingly, this is not the case. Negatively charged dust particles are
routinely observed to levitate in the sheath region between the plasma
bulk
and the powered electrode.
If the electrodes are of different materials, or they are of different
shapes, you can get various effects.
It is dependent upon what frequency the RF is at also.
Just static fields will easily be stronger than gravity on a dust particle,
that is how electrostatic filters work.
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| User: "James Stokes" |
|
| Title: Re: Potential difference in a capacitive rf discharge |
13 Aug 2005 11:38:16 PM |
|
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"night soil dalits" <invalids@invalid.com> wrote in message
news:42feb813$0$83478$892e7fe2@authen.white.readfreenews.net...
"James Stokes" <someone@microsoft.com> wrote in message
news:hqyLe.83580$oJ.33682@news-server.bigpond.net.au...
"night soil dalits" <invalids@invalid.com> wrote in message
news:42feb144$0$16783$892e7fe2@authen.white.readfreenews.net...
"James Stokes" <someone@microsoft.com> wrote in message
news:lGxLe.83170$oJ.13787@news-server.bigpond.net.au...
A capacitively coupled radio frequency discharge consists of two
electrodes
with one electrode capacitively coupled to a radio-frequency power
source
and the other electrode grounded, with a quasi-neutral plasma formed
between. Since the discharge chamber is also grounded, the grounded
probe
has much larger surface area than the powered probe. I'm trying to
understand why this difference in surface area results in the
establishment
of a net potential difference between the electrodes, allowing
negatively
charged microparticles to levitate against gravity above the lower
(powered)
electrode.
Thanks.
James
RF is Alternating, a static field will not be established, nothing will
levitate.
Interestingly, this is not the case. Negatively charged dust particles
are
routinely observed to levitate in the sheath region between the plasma
bulk
and the powered electrode.
If the electrodes are of different materials, or they are of different
shapes, you can get various effects.
It is dependent upon what frequency the RF is at also.
Just static fields will easily be stronger than gravity on a dust
particle,
that is how electrostatic filters work.
Yes, but why does the difference in surface area give rise to a net electric
field?
James
.
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| User: "night soil dalits" |
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| Title: Re: Potential difference in a capacitive rf discharge |
14 Aug 2005 04:54:04 PM |
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"James Stokes" <someone@microsoft.com> wrote in message
news:YUzLe.84347$oJ.17573@news-server.bigpond.net.au...
"night soil dalits" <invalids@invalid.com> wrote in message
news:42feb813$0$83478$892e7fe2@authen.white.readfreenews.net...
"James Stokes" <someone@microsoft.com> wrote in message
news:hqyLe.83580$oJ.33682@news-server.bigpond.net.au...
"night soil dalits" <invalids@invalid.com> wrote in message
news:42feb144$0$16783$892e7fe2@authen.white.readfreenews.net...
"James Stokes" <someone@microsoft.com> wrote in message
news:lGxLe.83170$oJ.13787@news-server.bigpond.net.au...
A capacitively coupled radio frequency discharge consists of two
electrodes
with one electrode capacitively coupled to a radio-frequency power
source
and the other electrode grounded, with a quasi-neutral plasma formed
between. Since the discharge chamber is also grounded, the grounded
probe
has much larger surface area than the powered probe. I'm trying to
understand why this difference in surface area results in the
establishment
of a net potential difference between the electrodes, allowing
negatively
charged microparticles to levitate against gravity above the lower
(powered)
electrode.
Thanks.
James
RF is Alternating, a static field will not be established, nothing
will
levitate.
Interestingly, this is not the case. Negatively charged dust particles
are
routinely observed to levitate in the sheath region between the plasma
bulk
and the powered electrode.
If the electrodes are of different materials, or they are of different
shapes, you can get various effects.
It is dependent upon what frequency the RF is at also.
Just static fields will easily be stronger than gravity on a dust
particle,
that is how electrostatic filters work.
Yes, but why does the difference in surface area give rise to a net
electric
field?
The E field is applied.
The surface area/shape distort the E field.
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| User: "CWatters" |
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| Title: Re: Potential difference in a capacitive rf discharge |
14 Aug 2005 02:46:58 AM |
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"James Stokes" <someone@microsoft.com> wrote in message
news:YUzLe.84347$oJ.17573@news-server.bigpond.net.au...
Yes, but why does the difference in surface area give rise to a net
electric
field?
I might be way off beam here but I remember someone telling me that an arc
acts like a diode. Perhaps there is some rectification of the RF field going
on.
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| User: "night soil dalits" |
|
| Title: Re: Potential difference in a capacitive rf discharge |
14 Aug 2005 04:52:43 PM |
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"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:SFCLe.168964$rv2.9600030@phobos.telenet-ops.be...
"James Stokes" <someone@microsoft.com> wrote in message
news:YUzLe.84347$oJ.17573@news-server.bigpond.net.au...
Yes, but why does the difference in surface area give rise to a net
electric
field?
I might be way off beam here but I remember someone telling me that an arc
acts like a diode. Perhaps there is some rectification of the RF field
going
on.
If the materials are slightly different or shaped different,
Plenty of data from Arc Lamp design, with carbon electrodes
But that was 60 Hz.
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| User: "Ron Baker, Pluralitas!" |
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| Title: Re: Potential difference in a capacitive rf discharge |
14 Aug 2005 09:19:42 AM |
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"James Stokes" <someone@microsoft.com> wrote in message
news:lGxLe.83170$oJ.13787@news-server.bigpond.net.au...
A capacitively coupled radio frequency discharge consists of two electrodes
with one electrode capacitively coupled to a radio-frequency power source
and the other electrode grounded, with a quasi-neutral plasma formed
between. Since the discharge chamber is also grounded, the grounded probe
has much larger surface area than the powered probe. I'm trying to
understand why this difference in surface area results in the establishment
of a net potential difference between the electrodes, allowing negatively
charged microparticles to levitate against gravity above the lower
(powered) electrode.
This doesn't make sense. Where do you think
you saw such a thing?
--
rb
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