ZonkerWilliam writes "Plasma wake particle accelerators are making surprisingly quick advances. It was a just a little while ago we had GeV acceleration in 3cm. Now they are capable of doubling the energy of electrons. 'Imagine a car that accelerates from zero to sixty in 250 feet, and then rockets to 120 miles per hour in just one more inch. That's essentially what a collaboration of accelerator physicists has accomplished, using electrons for their race cars and plasma for the afterburners. Because electrons already travel at near light's speed in an accelerator, the physicists actually doubled the energy of the electrons, not their speed.'"
There's talk about creating mini black holes with the upcoming particle accelerator coming online in a few years (I don't remember what it's called). But apparently, these mini black holes will evaporate very quickly, so there's no danger in creating a black hole that will go out of control. I hope they're right.
I assume you are referencing Dimopoulos and Landsberg's paper http://prola.aps.org/abstract/PRL/v87/i16/e161602 [aps.org] . There is nothing to worry about. These physicists proposed that if certain theories were true (M theory, quantum loop gravity, super symmetry) then the energy densities seen in the RHIC or LHC experiments could produce something "mathematically analogous" to a black hole. There is no possibility under any current theory that an event horizon could form and attract matter.
Black holes "suck" only as much as the mass that they contain does.
Any black hole created in a lab on earth is going to have negligable sucking power, since the mass in them will be tiny. The vision of a black hole forming and swallowing the earth is great sci-fi, but (happily) poor science. At worst, it will hang around, swallowing the odd electron at very rare intervals.
Hows the old saying go? "With the bomb squad, you can usually stop running after the first couple of blocks. If it involves the physics department, keep going."
or perhaps
"We're pleased to announce we are still here to report the results."
Forget portable cancer treatments, I want to bust some ghosts. Or at least get paid to blow the crap out of a fancy hotel. Never mind the part about it still needing two miles of pre-acceleration before the plasma wakefield thingamabobby kicks in, that's just a minor hiccup. Proton packs [wikipedia.org] are just around the corner.
Ahhhh, I love the smell of burning ectoplasm in the morning! It smells like victory.
Cue people who pretend they understand the science...
As mentioned, there are some of us around here who are actual scientists. However, there are no details in the article, thus no science to understand. All I found were crappy analogies with afterburners and some hand-wavey crap about plasma. I'm pretty sure that if it were as easy as running some crap through a plasma to accelerate it, it would have been done some time ago. And there are a number of pertinent questions:
Why do they have to use a 2-mile accelerator if the plasma can do in a foot what it takes the 2 miles to do?
Why can't it be longer?
How is the plasma chamber set up? I'm guessing it's probably an coupled with an RF field, which can accelerate a plasma, but details, come on!
The kinetic energy is proportional to speed^2 (E=1/2 m v^2), so a car at 120mph has 4 times the energy of a car at 60mph. Thus, doubling in energy is not like doubling in speed.
I didn't know 60 mph was close to c. Maybe for large values of 60?
Or relativistic hours? I mean 'miles per hour' for a person travelling at relativistic speeds would be different from 'miles per hour' for a non-relativistic observer wouldn't it, since time dilation would mess with the hours? Or something like that?
Unfortunately, these concepts will not be applied to the next generation of high energy accelerators. The International Linear Collider will supplant the Large Hadron Collider some time after 2015, but relies on superconducting static-gap technology and will be 30-40 kilometers long. Perhaps the next generation of experiemnts will employ plasma accelerators?
Yes, it'd be great if we could accelerate particles like this for the "next next big thing" after the ILC. Unfortunately, the energy levels using these and other exotic techniques are not yet all that high. Notice that the electrons are spun at SLAC for about 2 miles up to 43 GeV, then this technique about doubles the energy to 85 GeV in 33 inches.
However, they still need to show that this can be done again and again; the ILC will be in the range of 500-1000 GeV. I only work with particle physicists (mathe
As I understand it, luminosity is one major reason why this technology is not yet ready for prime time (i.e. not in time for the proposed ILC). You can't just accelerate a few particles to high energies and say you are done. You're looking for rare processes, so you need to create many consistent particle collisions per second in a tiny area. This means you need to have a tight, "bright" beam. The Tevatron has a luminosity of ~2e+32 interactions/cm^2/s now, the LHC may eventually reach 1e+34, and the goal for the ILC is more like 2e+34. Plasma wakefield systems are now demonstrating large increases in energy over short distances, but it's very difficult to daisy-chain them together to reach high total energies with any significant luminosity.
Unless you are just looking to punch great smoking holes in tanks or something?
This should work fine, as long as you don't mind having to carefully sneak up to within millimeters from the enemy tank while lugging a two-mile accelerator.
That's essentially what a collaboration of accelerator physicists has accomplished, using electrons for their race cars and plasma for the afterburners.
From the article description: 'Imagine a car that accelerates from zero to sixty in 250 feet, and then rockets to 120 miles per hour in just one more inch.
1/2 mv^2 is the non-relativistic kinetic energy. The mass correction will change the energy rapidly as v approaches c. The mass correction [wikipedia.org] with the Lorentz factor [wikipedia.org]in that expression are needed to get the correct relativistic energy.
The lorentz factor is 1/sqrt(1-(v/c)^2); at 0.99c it will multiply the mass (and energy) by a factor of 7; at 0.999c it will multiply everything by a factor of 22.3.
They increased the mass of the electrons by 1.65064935 × 10-27 hundredweight in 0.00032808399 football fields. Sorry, I don't know how much that is in SUVs.
Seriously, though, this is a neat trick. (Yes, IAAP)
Unless you can explain that to me in terms of volkswagens, elephants, and libraries of congress, I'm afraid you've lost me there. P.S. Giving scientific notation to the average American is like giving a speak and spell to the average ant. They can't even press the buttons. Besides, only engineers use decimal measurements, everyone else uses fractions.
'Imagine a car that accelerates from zero to sixty in 250 feet, and then rockets to 120 miles per hour in just one more inch.
First of all at non relativisitc speeds, doubling the speed results in a four fold increase in kinetic energy and not a doubling. Why give a bad classical mechanics analogy and then tell us that the speed didn't actually double because of relativistic effects.
Imagine a bunch of cars that accelerate from zero to sixty in 250 feet, then slam into a barrier, causing a multi-car pileup from which, starting just one inch further down the road, one of them rockets out at 85 miles per hour.
(Obviously they were inspired by the traffic on Interstate 280 on their way to SLAC. B-) )
I actually do some work on this with the PWFA group at USC (i'm an undergrad research assistant). It really is amazing! We can reach acceleration gradients of around 60 GeV/m, compared to something like 40 MeV/m for a normal accelerator. It works like this: 1. The electrons travel down the main linac in carefully spaced "bunches", and get accelerated to around 43 GeV over a course of ~3KM (this is at the main beam at SLAC). 2. A (in the last experiment) 1.2m long Lithium plasma "oven" is at the end of the beam, which the electrons are directed into. 3. The first, or "driving," bunch goes through the plasma, and repels all of the electrons it gets near, leaving an "empty" wake behind it, where only the positively charged ions are. 4. The positive charge behind the driving beam pulls it backwards, causing it to lose energy. At the same time, a "witness" bunch placed strategically within the wakefield gets pulled forward by the positively charged ions. The witness gains energy while the driver loses energy. 5. Voila! One bunch now has twice the energy, and one bunch now has none . ..or at least something close to that!
The main caveat is that you're upward-limited by your entering energy, so you still need a huge Linac to accelerate the bunches to begin with. This will likely get tacked on in the form of a "plasma afterburner" to a normal linac, such as in the setup at SLAC.
I've not read any of the technical papers on this yet but off hand I wonder if a) you can ever get the same luminosity as more traditional methods and b) how well can this be used for heavier particles? I suppose the first real world use would be as an injector?
As far as I understand it, it doesn't work nearly as well for heavier particles (I assume you are thinking protons?). Especially ones with a positive charge. The heavy mass of the protons compared to the electrons in the plasma cloud are what allows the "wakefield" to be created in the first place. When we model this stuff, the ions move so slowly compared to the electrons that we generally just assume that they are static for the duration of the beam passing through the oven (pico-femto second range). As I mentioned earlier, this will most likely always show up as an "afterburner" that goes at the end of a traditional linac.
4. The positive charge behind the driving beam pulls it backwards, causing it to lose energy. At the same time, a "witness" bunch placed strategically within the wakefield gets pulled forward by the positively charged ions. The witness gains energy while the driver loses energy.
sounds like a slingshot pass in NASCAR. Shake-n-Bake, baby
Understandably, one wants the bunches to be small. Wouldn't this mechanism tear the bunches apart, and give them much higher temperature (i.e. spread out energy distribution)?
I attended a talk from one of the primary investigators on this project a few months back. The system does indeed spread out the distribution, which can be bad for some circumstances. When all you care about is the peak energy, however, it's great. They call it a plasma afterburner.
One thing that isn't obvious is that you can't use two of these devices to double the energy twice. One doubling is all you got. Apparently there's some theorem in plasma physics that a Gaussian distributed pulse (as SLAC is) can only be energy-doubled by any method or methods once. I don't know the details of this, and I might be misrepresenting it, but there you go.
By the way, I think you have a misconception about temperature. It's true that a higher temperature gas has a wider energy spectrum, but the primary piece of information you're interested in is the average velocity. The statistical distribution is a function of only one variable -- you can't "spread out" the distribution to increase the temperature without simply dumping energy into the system. If you somehow separated the particles into low average energy and high average energy, you'd just have two classes of particles with two temperatures, not one cumulatively higher one.
In terms of solving the relevent math covered in the study of Quantum Mechanics and Molecular Spectroscopy [google.com] (senior Inorganic Chem II [rose-hulman.edu] at my alma mater), pumping energy into an electron [slashdot.org] is computationally similar to accelerating an object of 1000 kg mass to 60 mph over the span of time required to travel 250 feet and then nearly instantaneously pumping enough energy to double the velocity in the span of time represented by the distance travelled in one more inch.
Well sure, it's a lot more like taking a car that accelerates from zero to whatever in however many feet, and then doubling its mass in an inch. While more accurate, studies have shown that most people have no fucking idea what mass really means, so the stupid race car simile was utilized even though it was, well, stupid.
A simile depends on having a kind of mapping between one domain and another. These allow you to use reasoning from one domain to reason in another. That's why they're so useful - by using such a mapping, people inexperienced in one domain can still reason in it by leveraging their experience in another. For example, when Shakespeare says "Shall I compare thee to a summer's day" he points out that some of our reasoning about summer's days can be applied to people too. Fo
The other formula for E, you might have heard of, is E=mc^2. m = \gamma m_0, where m_0 is the rest mass, \gamma = 1 / sqrt(1 - \beta^2), and beta = v/c. I.e.,
E=m_0 c^2/sqrt(1 - v^2/c^2)
For very small values of v (relative to c), 1/sqrt(1-v^2/c^2) \approx = (1/2)v^2/c^2, which leads back to your formula - but the approximation is only valid for v
Your point is right, but your math at the end there is a little flaky. What it actually works out to is: E = mc^2 = \gamma m_0 * c^2 ~~ m_0*c^2 + (1/2)m_0*v^2 and if we subtract out the rest energy we get the classic "1/2 mv^2" for v near zero.
What the.... sigh. Something that ought to be pointed out here is that E=mc^2 is generally understood to be E=m0c^2, where m0 is rest mass. Very rarely is this equation used for total energy (Kinetic + rest energy). See good ol Wikipedia for more info.
Also, for v much smaller than c, 1/sqrt(1-v^2/c^2) approaches 1, as v^2/c^2 approaches 0.
We're all going to die! (Score:4, Funny)
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Misunderstanding (Score:5, Informative)
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Old Chestnut (Score:3, Informative)
Any black hole created in a lab on earth is going to have negligable sucking power, since the mass in them will be tiny. The vision of a black hole forming and swallowing the earth is great sci-fi, but (happily) poor science. At worst, it will hang around, swallowing the odd electron at very rare intervals.
Don't Knock It! (Score:5, Funny)
Other than a morbid fear of lightning rods and antistatic wrist-straps, it pretty much rocks.
Parent
Re:We're all going to die! (Score:5, Funny)
"With the bomb squad, you can usually stop running after the first couple of blocks. If it involves the physics department, keep going."
or perhaps
"We're pleased to announce we are still here to report the results."
Parent
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Don't worry, there's always an alternate universe where the experiment fails.
Cue people who pretend they understand the science (Score:5, Funny)
Re:Cue people who pretend they understand the scie (Score:3, Interesting)
Never mind the science, give me my proton pack! (Score:2)
Ahhhh, I love the smell of burning ectoplasm in the morning! It smells like victory.
Re:Cue people who pretend they understand the scie (Score:2, Funny)
Re:Cue people who pretend they understand the scie (Score:5, Insightful)
Cue people who pretend they understand the science...
As mentioned, there are some of us around here who are actual scientists. However, there are no details in the article, thus no science to understand. All I found were crappy analogies with afterburners and some hand-wavey crap about plasma. I'm pretty sure that if it were as easy as running some crap through a plasma to accelerate it, it would have been done some time ago. And there are a number of pertinent questions:
Why do they have to use a 2-mile accelerator if the plasma can do in a foot what it takes the 2 miles to do?
Why can't it be longer?
How is the plasma chamber set up? I'm guessing it's probably an coupled with an RF field, which can accelerate a plasma, but details, come on!
Parent
E=1/2 m v^2 (Score:5, Informative)
Re:E=1/2 m v^2 (Score:5, Insightful)
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Re:E=1/2 m v^2 (Score:5, Funny)
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Or relativistic hours? I mean 'miles per hour' for a person travelling at relativistic speeds would be different from 'miles per hour' for a non-relativistic observer wouldn't it, since time dilation would mess with the hours? Or something like that?
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International Linear Collider (Score:2, Informative)
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Notice that the electrons are spun at SLAC for about 2 miles up to 43 GeV, then this technique about doubles the energy to 85 GeV in 33 inches.
However, they still need to show that this can be done again and again; the ILC will be in the range of 500-1000 GeV. I only work with particle physicists (mathe
Luminosity (Score:5, Informative)
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Unless you are just looking to punch great smoking holes in tanks or something?
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innerspace (Score:5, Funny)
Those sound like really small physicists.
Re:innerspace (Score:5, Funny)
And their wives still say they're compensating.
Parent
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At least we know what happened to the Indonesian Hobbits. They didn't die out the evloved into physicists.
Good way to die of acceleration (Score:2)
Say hellow to jello bones.
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Bah! (Score:2, Offtopic)
-jcr
how energy changes as v -- c (Score:2, Informative)
The lorentz factor is 1/sqrt(1-(v/c)^2); at 0.99c it will multiply the mass (and energy) by a factor of 7; at 0.999c it will multiply everything by a factor of 22.3.
For the Americans here (Score:5, Funny)
Seriously, though, this is a neat trick. (Yes, IAAP)
Obligatory Response (Score:2)
Re:Obligatory Response (Score:5, Funny)
Unless you're irrational, that is.
Parent
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The example is stupid... (Score:3, Insightful)
So let's try this: (Score:2)
(Obviously they were inspired by the traffic on Interstate 280 on their way to SLAC. B-) )
I actually work on this at USC!!! (Score:5, Informative)
1. The electrons travel down the main linac in carefully spaced "bunches", and get accelerated to around 43 GeV over a course of ~3KM (this is at the main beam at SLAC).
2. A (in the last experiment) 1.2m long Lithium plasma "oven" is at the end of the beam, which the electrons are directed into.
3. The first, or "driving," bunch goes through the plasma, and repels all of the electrons it gets near, leaving an "empty" wake behind it, where only the positively charged ions are.
4. The positive charge behind the driving beam pulls it backwards, causing it to lose energy. At the same time, a "witness" bunch placed strategically within the wakefield gets pulled forward by the positively charged ions. The witness gains energy while the driver loses energy.
5. Voila! One bunch now has twice the energy, and one bunch now has none . .
The main caveat is that you're upward-limited by your entering energy, so you still need a huge Linac to accelerate the bunches to begin with. This will likely get tacked on in the form of a "plasma afterburner" to a normal linac, such as in the setup at SLAC.
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would be as an injector?
Re:I actually work on this at USC!!! (Score:4, Informative)
Parent
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Re:I actually work on this at USC!!! (Score:5, Informative)
One thing that isn't obvious is that you can't use two of these devices to double the energy twice. One doubling is all you got. Apparently there's some theorem in plasma physics that a Gaussian distributed pulse (as SLAC is) can only be energy-doubled by any method or methods once. I don't know the details of this, and I might be misrepresenting it, but there you go.
By the way, I think you have a misconception about temperature. It's true that a higher temperature gas has a wider energy spectrum, but the primary piece of information you're interested in is the average velocity. The statistical distribution is a function of only one variable -- you can't "spread out" the distribution to increase the temperature without simply dumping energy into the system. If you somehow separated the particles into low average energy and high average energy, you'd just have two classes of particles with two temperatures, not one cumulatively higher one.
Parent
Another particle in a box (Score:4, Informative)
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A simile depends on having a kind of mapping between one domain and another. These allow you to use reasoning from one domain to reason in another. That's why they're so useful - by using such a mapping, people inexperienced in one domain can still reason in it by leveraging their experience in another. For example, when Shakespeare says "Shall I compare thee to a summer's day" he points out that some of our reasoning about summer's days can be applied to people too. Fo
Only for small values of v (Score:5, Informative)
E=mv^2/2 only for small values of v.
The other formula for E, you might have heard of, is E=mc^2. m = \gamma m_0, where m_0 is the rest mass, \gamma = 1 / sqrt(1 - \beta^2), and beta = v/c. I.e.,
E=m_0 c^2/sqrt(1 - v^2/c^2)
For very small values of v (relative to c), 1/sqrt(1-v^2/c^2) \approx = (1/2)v^2/c^2, which leads back to your formula - but the approximation is only valid for v
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Guilty as charged (Score:2)
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