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February 22, 2005


little miss demosthenes

just making sure - rms == root mean square?


Yes. rms == root mean square. I can't figure out how to do symbols on this blog, otherwise I would have used a sigma. Sorry.

little miss demosthenes

http://www.chaos.org.uk/~eddy/bits/chars.html should do the trick


Excellent!! Thanks.


I'm not sure that I'm reading the graphs correctly. Do they show that the energy of the electrons after field ionization has a larger spread (including a lower minimum) but with a higher average?



At threshold the plasma isn't ionized until the middle of the bunch (peak of the Gaussian). Once ionized, the beam then expels the plasma electrons to generate the plasma wake. The problem is, at threshold, the wake starts too late so no particle get accelerated since the wake crashes too far in back of the bunch. After we are way past threshold, ionization occurs earlier and earlier, until the wake is recovered and particles accelerated.

So in the picture I have shown, it is just energy loss no energy gain. Although you are correct that when the wake is recovered, there is a large energy spread. Later I will show the energy gain. But excellent point which I should have made clearer.

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