Caolionn O'Connell

First.

Tomorrow is my first day on the job. And I think I can safely say, I am scared s**tless. I feel like a little bit of a poser. Yeah, sure, I have a Ph.D., but do I really know what the hell I'm doing? Does a thesis in an über-specialized field make me more qualified as a physicist? It is not totally obvious to me that it should, hence the semi-permanent feeling of dread. I am hoping the worry will start to dissipate once I start; if not, there will certainly be an ulcer in my future.

Also I am a little bummed that I am now entering "adulthood". I am planning. Long-term planning. I am thinking about things like publications, how those publications will effect my career, whether I want a government job or a university job. Like the fact that I even have a career – what's up with that, when did that happen? Adulthood was so much better when it was limited to major appliances.

One good thing: the new boss already knows about QD. It seems I was outed by someone who recognized my name when it was mentioned as a new hire. I was kinda dreading the whole, "well, um, I have a, um, blog-thing. I hope that's cool." conversation, so I'm happy someone else took care of it for me. Thankfully, he seemed a bit vague about it when he brought it up, so I'm going to assume he doesn't actually read it.

Beautiful

Three of the most beautiful signatures I have ever seen.

If you are looking for a little night-time reading – I can assure you will be sleeping like a baby within the first 20 pages – I will either post my thesis here or add a link to it within the next couple days.

The end is nigh

... for good or bad. My last day at SLAC is Tuesday and there is still so much to be done.

* PAPERWORK: I think the true test of the graduate student is not the defense, but the paperwork. As it stands, I am not faring too well. Perhaps it is a bad sign, I am so incompetent that I should be foiled by the "Doctoral Dissertation Agreement Form" or the "Survey of Earned Doctorates". Or maybe it is a sign that I am now truly a physicist who has exchanged the company of society for the machinery of a laboratory. Machinery doesn't require you to make two appointments – one to verify that you have crossed your t's and dotted your i's, the other to actually hand the damn thing in. Machinery doesn't even require you to read the instruction manual. I have always been a misanthrope in the making, I think I have just come over to the other side. It is official: machinery makes sense, people do not.

* THE SEMBLANCE OF A PAPER: Wouldn't life be so much easier if we could just hand in the thesis to the peer-review journal of our choice? I am tired of this thing, but it just won't go away. Every time I read a chapter, I keep finding sentences I would like to rework and now that I am writing a paper, I am forced to read it over and over again. Cutting down the entire topic into something that can maintain the interest of the reader seems completely unreasonable. As it stands, my own eyes glaze over when I try reading what I wrote.

Naming Convention

I am usually not one for bawdy humor on this blog, but this was way too funny not to share. I am wondering if Spankme is someone's last name – they must have had a very difficult time in high school – or is someone just being really juvenile for our amusement. Either way, you can keep your comments to yourself on this one.

p.s. Very rarely has a friend requested to be mentioned on my blog by name, mostly they prefer to be left anonymous. Occasionally, conversations have even been prefaced, "You include this on your blog and I will kill you" (...P.B...). But David wanted a shout out. Since he and T.J. lent me their couch, he gets his shout-out. He also wanted to be described as Bogart-esque, but, really, he is more Jimmy Stewart. Sorry, man, I am in the business of truth here.

A Pod Person

I have been very vocal about my love for the iPod mini. Well, I didn't think it was possible, but my love and admiration just grew deeper with the latest update for my mini. I have discovered the Podcast and spent 4 out of the 6 hours driving here listening to articles from Slate. I think the next question is whether I will ever be productive again or just find more shows to download. For God's sake, there are two Potter-based podcasts in the top ten downloads alone!!

Outlook remains hazy.

By the way, should you have any favorites to recommend, please share.

Baby steps.

I realize this may come as a shock to some of you, but it seems that Caltech ranks athletics pretty low on the totem pole of importance. To wit, they do not have a stadium or even any bleachers that could possibly constitute stadium seating. Nothing. I know, I know, sooo surprising.

Since my ass got kicked trying to climb a mountain this past weekend, I have decided to return to exercise after my long hiatus. In my humble opinion, travel and sickness don't mix well with exercise, especially if you are a big fan of the deep-fried bananas. In my efforts to forestall the onset of (even more) love handles, I have become a stadium squatter. Thankfully, Pasadena City College believes in the benefits of exercise and installed a stadium about 5 years ago; also they don't seem to mind outsiders using it. Granted, it is a baby stadium, but it's something.

Tomorrow I head back up to SLAC to finish the thesis edits, get signatures and write a paper. I think I will fit in a couple days to run proper stadiums at Stanford, the kind that make you want to hurl after the second set.

Warning! Warning!

My brother and I used to play a game trying to find the most ridiculous warning signs featuring stick figures. Our favorite was always the man getting squashed by the Coke machine because he rocked it. Not only is it an absurd image, but I like to think of it as a parable for being too cheap. Well, move over Coke man, I think I just found a new favorite:

Cosmic

By the way, if you actually looking for physics on a more regular basis, there is a (relatively) new blog in town, with 5 different smarty-pants contributors (all physicists):

Cosmic Variance

I am sure most of you found the site already on your own, but in case you live under a rock, I thought I would give you a little heads-up.

Energy, Baby!

Just to be different, today we will talk about physics. Mostly because I have done nothing of interest in the past few days, so I have nothing else to talk about. I previously mentioned the PRL cover we just got, so I thought I would explain the results a little better. It is, after all, a cover, so I feel it is well within my rights as the lowly graduate student to brag.

This explanation builds on some of the other previous entries. Specifically, the general introduction to acceleration and the specific introduction to plasma-based acceleration.

Okay, back to the basics. Sorry, I am using a slide from defense's powerpoint presentation. I am lazy. You gotta problem with it? Tough.

The top image is the schematic of what happens when the beam enters the plasma. The bottom image is the charge distribution of the incoming beam in maroon, as well as, the energy distribution of the beam before and after the plasma. The incoming beam (green) already has an energy chirp (i.e. the head particles are more energetic that the tail particles). When the beam goes through the plasma, the bulk of the particles lose energy to drive the plasma wake and then the tail particles gain energy when the plasma electrons land behind the beam – the green shaded region in the picture above.

Our diagnostic looks at the energy axis. Imagine that you take the blue and green lines and look at their energy profiles. In other words, you take a time integrated picture of the energy profiles with and without the plasma. This picture might help with that visualization (the green is profiled on the left and the blue is profiled on the right). It is a crappy picture, but you get the idea (hopefully).

Now to look at the data:

The image on the left is like the green profile, whereas the image on the right is the blue profile. Note that the particles that have been accelerated are all the particles above the top line. This means a peak energy gain of about 2.5 GeV over a 10 cm plasma or 25 GeV/m (presently, SLAC acceleration is about 20 MeV/m). The particles accelerated in the plasma are not helpful in a real particle physics experiment because there is a huge smear in the energy. This smear is because of the way we do our experiment – we should be able to improve this by beam shaping, but that will be in the future. Also, for the skeptics, about 8% of the beam's electrons are accelerated. There could be (really, should be) more particles accelerated, but since we cannot resolve the beam in time we can't actually measure it. In the future we hope to improve that number too.

Okay, I think that's enough physics. This should make up for my month traveling and doing strictly non-physics related things.

An idea

I had thought that 5 weeks away from my thesis would reinvigorate me. The topic would return to the fascinating physics I thought it was when I first started working on it rather than painful task it became towards the end.

I was wrong.

I have finally started going through my reader comments and I noticed that I got a very good grammar lesson from one of my committee members:

"which" vs. "that" – only use "which" to start parenthetical phrases (as opposed to restrictive phrases). A phrase beginning with "which" should always start with a comma. Use "that" to begin restrictive phrases.

Here is an example:
i. Give me the cup, which is red.
ii. Give me the cup that is red.

In the first sentence, we can assume that there is only one cup, which happens to be red. Parenthetical phrases have the property that they can be dropped without fundamentally changing the meaning of the sentence. In the second sentence, we can assume that there is more than one cup, and I want the one that is red.

I didn't know that. Based on the cost of educating it, I think my brain is worth a kagillion dollars at this point and I didn't know that. If you went to public school and know the difference between "which" and "that," congratulate yourself on having saved s**t-ton of money.