ARGH!

[danaeris]

I am italicized. He is bolded.

How can I describe the vertical beam size to an audience that doesn't know what a gaussian sigma is? Looking at the following thing you said in a previous email:

1) The vertical beam size at the collision point is the Gaussian sigma (=FWHM/2.3)of the bunches that collide. The luminosity equation I showed you assumes Gaussian beams so it's the same dimensional size. The beams we use are Gaussian out to about 6 sigma (pretty good).

Then, is vertical beam size a statistical approximation of the actual beam size? If I just leave it at 'vertical beam size', readers will think it is the physical cross section of the beam. I need to either put a disclaimer on it or, preferably, explain it properly in non technical terms. What is the vertical beam size a _measure_ of?


The readers already know that our beams have a vertical beam size (physical size) and that the quadrupole magnets can be used to focus the beams and make the beam sizes smaller. We will be making the beam sizes smaller this fall with the optical lattice changes we are making to PEP-II.

Am I to understand that it is acceptable for this article to let the readers think that
the vertical beam size is indeed the diameter or cross-section of the beam (and if so,
which is it), either because it is or because it is very similar to the physical size?

The vertical beam size is indeed one half the diameter and the physical cross section of the beam. Same as the physical size.

Previously, there was no mention of these optical lattice changes being made to PEP-II. What do optical lattices do and how will they make the beam smaller?

The optical lattice functions at the collision point can be adjusted using the quadrupole magnets around the ring. These lattice changes the "beta" values in the equation I showed you for the beam size. [size =sqrt(beta*emittance)].



*sharpening her knives with an insane grin on her face*

Comments

[londo.livejournal.com]

Don't confuse an academic with his head up his ass with a physicist.

[zunger.livejournal.com]

Sheesh... that's pretty bad, even as far as the physics department go.

And BTW, 2*the vertical beam size actually is pretty much the size of the beam. (The number quoted is a radius, not a diameter :)

Small(ish) world.

[sirreality.livejournal.com]

So I saw your post here, thought the name looked really familiar, read a bit of your journal then remembered that I picked up your name in undergraduate days. Being older than I, I'm sure you've never heard of me, but I subscribed to the SPS list before I became active.

In any case, I thought your journal was interesting, so I added you as a friend.

Hi.