| Topic: |
Science > Physics |
| User: |
"Sam Wormley" |
| Date: |
02 Aug 2005 10:05:46 PM |
| Object: |
PLASMA JETS ON EARTH |
PLASMA JETS ON EARTH
From the surface of the sun to the violent cores of quasars, many astrophysical
objects shoot plasma in sharply defined streams, guided by magnetic fields. In
the 22 July PRL, researchers present a laboratory demonstration in which
magnetic forces squeeze hot plasma into a narrow tube without any
extraordinary arrangement of conditions. This mechanism, the scientists claim,
may help explain why tightly confined jets arise in many different astrophysical
circumstances, although some astrophysicists find the leap from lab to cosmos
premature.
(S. You et al., Phys. Rev. Lett. 95, 045002)
Link to the paper: http://link.aps.org/abstract/PRL/v95/e045002/
COMPLETE Focus story at http://focus.aps.org/story/v16/st4
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| User: "Jan Panteltje" |
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| Title: Re: PLASMA JETS ON EARTH |
03 Aug 2005 05:06:14 AM |
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On a sunny day (Wed, 03 Aug 2005 03:05:46 GMT) it happened Sam Wormley
<swormley1@mchsi.com> wrote in <ewWHe.214678$_o.83960@attbi_s71>:
PLASMA JETS ON EARTH
From the surface of the sun to the violent cores of quasars, many astrophysical
objects shoot plasma in sharply defined streams, guided by magnetic fields. In
the 22 July PRL, researchers present a laboratory demonstration in which
magnetic forces squeeze hot plasma into a narrow tube without any
extraordinary arrangement of conditions.
Now I may be wrong, but as a kid, in 1960 or so, I used an old
television picture tube, but this one was bad, and had some gas in it.
By applying the proper voltages you could see the PLASMA beam in the tube.
In those old tubes you had a big permanent magnet around it to FOCUS
the beam, you could see the beam focusing (glowing orange blue).
And ANY old TV experimenter must have been there.
One thing ... there is a LOT of current flowing, I had to switch of
after a minute or so.
So, am I wrong? Have these guys just repeated some old stuff?
Is my definition of plasma here correct: 'ionized gas'?
Some other memories come to mind... 'ion trap'.
That was a little magnet specially there top bend the electron beam
(so it went down to the deflection coils), the ions would normally
go straight (and hit the tube sides).
The electron gun was at an angle...
Maybe I misunderstood something in that 'news'.
Focusing ion beams has been done for ages?
So, what is 'plasma'?:
http://en.wikipedia.org/wiki/Plasma
Think I am right!
This mechanism, the scientists claim,
may help explain why tightly confined jets arise in many different astrophysical
circumstances, although some astrophysicists find the leap from lab to cosmos
premature.
(S. You et al., Phys. Rev. Lett. 95, 045002)
Link to the paper: http://link.aps.org/abstract/PRL/v95/e045002/
COMPLETE Focus story at http://focus.aps.org/story/v16/st4
.
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| User: "Evgenij Barsukov" |
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| Title: Re: PLASMA JETS ON EARTH |
03 Aug 2005 04:16:20 PM |
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Jan Panteltje wrote:
On a sunny day (Wed, 03 Aug 2005 03:05:46 GMT) it happened Sam Wormley
<swormley1@mchsi.com> wrote in <ewWHe.214678$_o.83960@attbi_s71>:
PLASMA JETS ON EARTH
From the surface of the sun to the violent cores of quasars, many astrophysical
objects shoot plasma in sharply defined streams, guided by magnetic fields. In
the 22 July PRL, researchers present a laboratory demonstration in which
magnetic forces squeeze hot plasma into a narrow tube without any
extraordinary arrangement of conditions.
Now I may be wrong, but as a kid, in 1960 or so, I used an old
television picture tube, but this one was bad, and had some gas in it.
By applying the proper voltages you could see the PLASMA beam in the tube.
The tube has ELECTRONS beam, not plasma. Plasma has both + and -
particles and is overal electricaly neutral. That is why I find it
strange that magnetic fiels are able to shape it in any way.
Regards,
Evgenij
In those old tubes you had a big permanent magnet around it to FOCUS
the beam, you could see the beam focusing (glowing orange blue).
And ANY old TV experimenter must have been there.
One thing ... there is a LOT of current flowing, I had to switch of
after a minute or so.
So, am I wrong? Have these guys just repeated some old stuff?
Is my definition of plasma here correct: 'ionized gas'?
Some other memories come to mind... 'ion trap'.
That was a little magnet specially there top bend the electron beam
(so it went down to the deflection coils), the ions would normally
go straight (and hit the tube sides).
The electron gun was at an angle...
Maybe I misunderstood something in that 'news'.
Focusing ion beams has been done for ages?
So, what is 'plasma'?:
http://en.wikipedia.org/wiki/Plasma
Think I am right!
This mechanism, the scientists claim,
may help explain why tightly confined jets arise in many different astrophysical
circumstances, although some astrophysicists find the leap from lab to cosmos
premature.
(S. You et al., Phys. Rev. Lett. 95, 045002)
Link to the paper: http://link.aps.org/abstract/PRL/v95/e045002/
COMPLETE Focus story at http://focus.aps.org/story/v16/st4
.
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| User: "Sam Wormley" |
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| Title: Re: PLASMA JETS ON EARTH |
03 Aug 2005 04:23:40 PM |
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Evgenij Barsukov wrote:
Jan Panteltje wrote:
On a sunny day (Wed, 03 Aug 2005 03:05:46 GMT) it happened Sam Wormley
<swormley1@mchsi.com> wrote in <ewWHe.214678$_o.83960@attbi_s71>:
PLASMA JETS ON EARTH
From the surface of the sun to the violent cores of quasars, many
astrophysical
objects shoot plasma in sharply defined streams, guided by magnetic
fields. In
the 22 July PRL, researchers present a laboratory demonstration in which
magnetic forces squeeze hot plasma into a narrow tube without any
extraordinary arrangement of conditions.
Now I may be wrong, but as a kid, in 1960 or so, I used an old
television picture tube, but this one was bad, and had some gas in it.
By applying the proper voltages you could see the PLASMA beam in the
tube.
The tube has ELECTRONS beam, not plasma. Plasma has both + and -
particles and is overal electricaly neutral. That is why I find it
strange that magnetic fiels are able to shape it in any way.
Regards,
Evgenij
In those old tubes you had a big permanent magnet around it to FOCUS
the beam, you could see the beam focusing (glowing orange blue).
And ANY old TV experimenter must have been there.
One thing ... there is a LOT of current flowing, I had to switch of
after a minute or so.
So, am I wrong? Have these guys just repeated some old stuff?
Is my definition of plasma here correct: 'ionized gas'?
Some other memories come to mind... 'ion trap'.
That was a little magnet specially there top bend the electron beam
(so it went down to the deflection coils), the ions would normally
go straight (and hit the tube sides).
The electron gun was at an angle...
Maybe I misunderstood something in that 'news'.
Focusing ion beams has been done for ages?
So, what is 'plasma'?:
http://en.wikipedia.org/wiki/Plasma
Think I am right!
This mechanism, the scientists claim,
may help explain why tightly confined jets arise in many different
astrophysical
circumstances, although some astrophysicists find the leap from lab
to cosmos
premature.
(S. You et al., Phys. Rev. Lett. 95, 045002)
Link to the paper: http://link.aps.org/abstract/PRL/v95/e045002/
COMPLETE Focus story at http://focus.aps.org/story/v16/st4
Would not a magnetic filed deflect moving positive charges in
the opposite direction of negative charges in a plasma?
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| User: "Bruce Scott TOK" |
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| Title: Re: PLASMA JETS ON EARTH |
04 Aug 2005 06:06:52 AM |
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Sam Wormley wrote:
Evgenij Barsukov wrote:
The tube has ELECTRONS beam, not plasma. Plasma has both + and -
particles and is overal electricaly neutral. That is why I find it
strange that magnetic fiels are able to shape it in any way.
Would not a magnetic filed deflect moving positive charges in
the opposite direction of negative charges in a plasma?
The experiment is done on a plasma in the MHD regime, in which the gyro
orbits of individual particles about magnetic field lines (which indeed
are oppositely sensed) are small. Furthermore, the plasma is neutral,
and its dynamics is quasineutral (finite E-cross-B vorticity implies
nonzero charge density but all direct space charge effects are small,
valid if the Debye length is small and the Alfven speed is
subrelativistic). Finally, the electric field is assumed to be larger
than any pressure gradient (in scaled units) and hence the drift
velocity implied by the electric current density is small compared to
the plasma velocity. Under these assumptions, single-fluid MHD is
valid. Most astrophysical plasma applications are deeply into this
regime.
The confining force is given by J cross B, which is the sum of all the
Lorentz forces on each individual species of charged particle.
http://www.rzg.mpg.de/~bds/
http://www.rzg.mpg.de/~bds/lectures/
http://www.rzg.mpg.de/~bds/lectures/mhd-lecture.html
--
cu,
Bruce
drift wave turbulence: http://www.rzg.mpg.de/~bds/
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| User: "Jan Panteltje" |
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| Title: Re: PLASMA JETS ON EARTH |
04 Aug 2005 11:30:38 AM |
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On a sunny day (Wed, 03 Aug 2005 16:16:20 -0500) it happened Evgenij Barsukov
<evgenij_b_no_spam@yahoo.com> wrote in <dcrc74$633$1@home.itg.ti.com>:
Jan Panteltje wrote:
On a sunny day (Wed, 03 Aug 2005 03:05:46 GMT) it happened Sam Wormley
<swormley1@mchsi.com> wrote in <ewWHe.214678$_o.83960@attbi_s71>:
PLASMA JETS ON EARTH
From the surface of the sun to the violent cores of quasars, many astrophysical
objects shoot plasma in sharply defined streams, guided by magnetic fields. In
the 22 July PRL, researchers present a laboratory demonstration in which
magnetic forces squeeze hot plasma into a narrow tube without any
extraordinary arrangement of conditions.
Now I may be wrong, but as a kid, in 1960 or so, I used an old
television picture tube, but this one was bad, and had some gas in it.
By applying the proper voltages you could see the PLASMA beam in the tube.
The tube has ELECTRONS beam, not plasma. Plasma has both + and -
particles and is overal electricaly neutral. That is why I find it
strange that magnetic fiels are able to shape it in any way.
The tube had an electon beam alright, except if it was full of gas.
To neutralize this gas there was some chemical 'getter' that reacted with it.
FYI:
http://repairfaq.ece.drexel.edu/sam/crtfaq.htm
<quote>
A side benefit is that it blocks negative ions from residual air molecules
from hitting the phosphors. These might result in an unsightly blemish in
the center of the screen since they are much heavier (many thousands of
times the mass) than electrons and are not deflected very much. (This was a
problem in the early days of CRT production but apparently not with present
high vacuums and getters to clean up whatever is left.)
</quote>
http://www.saesgetters.com/default.aspx?idPage=281
or google CRT getter
The gas comes from bad vacuum, and heating of the electron gun and heater of
cause.
A special magnet 'ion trap' was used to separate the electron beam.
As for plasma, a plasma of + ions (as here) is also a plasma.
Do you have hands on experience with CRT's?
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| User: "Sam Wormley" |
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| Title: Re: PLASMA JETS ON EARTH |
03 Aug 2005 08:11:45 AM |
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Jan Panteltje wrote:
On a sunny day (Wed, 03 Aug 2005 03:05:46 GMT) it happened Sam Wormley
<swormley1@mchsi.com> wrote in <ewWHe.214678$_o.83960@attbi_s71>:
PLASMA JETS ON EARTH
From the surface of the sun to the violent cores of quasars, many astrophysical
objects shoot plasma in sharply defined streams, guided by magnetic fields. In
the 22 July PRL, researchers present a laboratory demonstration in which
magnetic forces squeeze hot plasma into a narrow tube without any
extraordinary arrangement of conditions.
Now I may be wrong, but as a kid, in 1960 or so, I used an old
television picture tube, but this one was bad, and had some gas in it.
By applying the proper voltages you could see the PLASMA beam in the tube.
In those old tubes you had a big permanent magnet around it to FOCUS
the beam, you could see the beam focusing (glowing orange blue).
And ANY old TV experimenter must have been there.
One thing ... there is a LOT of current flowing, I had to switch of
after a minute or so.
So, am I wrong? Have these guys just repeated some old stuff?
Is my definition of plasma here correct: 'ionized gas'?
Some other memories come to mind... 'ion trap'.
That was a little magnet specially there top bend the electron beam
(so it went down to the deflection coils), the ions would normally
go straight (and hit the tube sides).
The electron gun was at an angle...
Maybe I misunderstood something in that 'news'.
Focusing ion beams has been done for ages?
So, what is 'plasma'?:
http://en.wikipedia.org/wiki/Plasma
Think I am right!
This mechanism, the scientists claim,
may help explain why tightly confined jets arise in many different astrophysical
circumstances, although some astrophysicists find the leap from lab to cosmos
premature.
(S. You et al., Phys. Rev. Lett. 95, 045002)
Link to the paper: http://link.aps.org/abstract/PRL/v95/e045002/
COMPLETE Focus story at http://focus.aps.org/story/v16/st4
I remember (as a kid) being scared I was generating x-rays... Now I
know that the voltages I was generating were too low.
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