Physics? Really?

So I just finished a terrible midterm on Electricity & Magnetism taught by a nice guy but... bad teacher. Awful teacher. I'm so sick of being taught physics by theorists. I get the feeling that if I wanted to be an experimental physicist I should have just gone into engineering.

Along those lines, looking on courses to take for next semester, the options are bleak in physics. Solid State, and Advanced Quantum Mechanics. Solid State would be nice because it can help me get a job, but that's about it. Engineering courses on the other hand, are awesome. Vehicle Design, Photonics, Feedback Controllers, etc. What the hell? Rather than learning really cool things that are real, I'll be learning about Group Theory and the Theory of Representations, which is an entire course dedicated to what happens when you, get this, turn something slightly. Ack.

more of the same. waaaay too much of the same.

Hi, I'm back, it's been awhile, I know. I've been putting in a lot of loooong hours at work, and just got back from a week at Case Western Reserve University, where the first stage of LUX is being built (dubbed LUX 0.1). We got a lot of work done, learned a lot, but glad to be home now. Missed the misses quite a lot, so I'm staying put for awhile. I'm technically on vacation now for spring break, but instead of being lazy, I have to make up work for my classes and study a lot so that I don't fail. Failing would be bad. However, the semester is flying by in a good way, pretty soon it'll be summer and I'll be able to spend all my time on research. Also, working at the camp as 'Mr. Physics' in which I will run 1 hour physics experiments/demos for kids in Michael's camp. I'm nervous because I'm notoriously bad with kids, but the money is very attractive, especially since I get paid so little for summer work.

Anyway, before then we have some vacations to look forward to. One will be a trip to Arizona to visit my Dad, and another will be a trip to Seattle to visit Erin's Dad. We're also hoping to be able to afford a trip in June to my cousin's wedding in Long Beach, but we may not come up with the money for it. Oh well, such is life when first starting out.

Speaking of which, Erin is taking more classes, this time for photography! Also, Erin's sister Meghan got into Harvard for mind, brain and education, and her mother is going to finish her dissertation (finally) on music stuff (Franz Liszt). So everybody is back to school!

Now if you were reading this blog for the science, then here, some pictures of my trip to Case.

Sorry this is sideways. This is the top two flanges for the detector can. The bottom flange has a smaller can that bolts to it, and that's where the liquid xenon, pmts, etc. go. The top flang has a larger can that bolts onto it over the smaller one and that's the vacuum and cryostat for cooling. The cans are shown...


... in this picture


This is Dave and I working in the clean room... We broke something, now we're trying to fix it...


Here is more of the detector constructed. The aluminum blocks are to take up space so that we don't use a lot of liquid xenon. The idea is that this is a smaller version of the larger, full LUX, so we use the same detector system, just use a tinier amount of PMTs and xenon. The big hole in the back is where the instrumented xenon will be, with the four PMTs observing it. Ask questions if you don't know what I'm talking about.


This should give you a better idea of what everything should look like, only this will have an even larger can over it, and then the whole contraption will go in a large bucket of water, because water is good at shielding against neutrons that can create noise in the detector.


That's it for now! Bye!

still married, still in graduate school.

Hi there, it's been awhile. So far, nothing really new. Still married, Erin is still in school for graphic and web design, and I'm still in school for physics. This last one was (and still is sometimes) on the edge. I am finding things about graduate school that may not be what I want. That is, what I want may not be worth the work to get there, and I can get some job doing what I want (engineering and physics R&D) with only a master's degree, and not the whole Ph.D. So, the plan is to go ahead and get my master's in physics (which should be complete by January of next year) and then take another look and see if I can stay on for another 4 years, or if I will put it off and get a job. Of course if that happens I can always go back and finish a Ph.D, or get a master's in engineering (two master's equals a Ph.D, everyone knows that). In any event, I enjoy the research, the classes kind of suck, but I have to do them. Maybe by the time classes are over I'll be content to help discover dark matter. Anyway, that being said, back to work. Weekends are for homework.

By the way, still working on the data acquisition system for the LUX dark matter experiment, and now also working on research on avalanche photodiodes as an application for dark matter detection. Fun stuff.

Stay savvy.

Married.

So there, I did it. We did it. Erin and I got married. That's right, I'm now Mr. Jeremy Chapman!

Of course, most of you who read this were probably there, and those who weren't... either it's your fault, or .... haha. Sorry.

Anyway, here's a sample picture from the wedding...


Compliments of Grazier Photography. I think it exemplifies what our marriage will be like: classy, artsy, fun, and really, really goofy.

Fantastic 5th

I'm watching the latest Fantastic 4 movie with Gwerin, and the defense department asked Reid Richards to do a science thingy for national security. Instead, he refers the good General to Dr. So and So, head of the physics department at Brown. That's right, Brown!! Now I know I made the right decision to come here! I mean, basically, the Fantastic 4 refer to, in some way or another, ME. I'm practically the Fantastic 5th! Now what powers do/could I have...

In the interest of blog participation, please, tell me what power you think I should have, and/or what power you would have, had Reid Richards referred the welfare of the world to you...

Spam 4 cheap $$!!

Spam filters, I imagine, use some sort of algorithm to detect what it should consider spam or not. Subject lines and email content that include references to Viagara, Penis Enlargement, Cialis, Erections, and any number of symbols used to spell out those and other 'buzz' words. The Brown spam filter works much this way. However, that leads me to wonder what people in the Medical school do, and what about people who study anatomy or biology or sexual psychology or whatever do? I imagine a lot of their emails get marked as spam. Do they have to disguise their emails by changing words like 'penis' to say... 'puppy'? Do they send emails regarding the psychological effects of puppy size, so that their messages get through? A spam filter can't tell the difference between 'Viagara 4 low cost! Huge, fast effects now!' and 'regarding paper on effects of cost of Viagara on low income men in their 40's' or whatever.

It's probably not fair.

I'm just saying.

Dark Matter really is dark!

Hi, it's been awhile, but I've been busy. Hm. Understatement of the year I think. 14 hour days start to get to you.. In fact, I've noticed that all this fancy learnin' has actually begun to push other information out of my head. When I was a kid I was able to remember license plates of all my friends and their parents. I remembered telephone numbers from when I was a kid... Now all that is gone (though not really missed). Now I forget conversations and events, I forget when they happened, something that happened two days ago I claim happened weeks ago... I'm actually becoming an absent minded graduate student. Anyway, hopefully it's not all for naught. I've come to the conclusion that graduate school, so far anyway, would be very satisfying if it weren't for the classes. On that note, I'll segue to a discussion of my research....

Dark matter. I'm working on an experiment called LUX, which I think stands for some amalgamation of liquid, underground, and xenon. Of course, the underground isn't liquid, the xenon is.... Anyway, this is an experiment to detect dark matter directly. Dark matter has been detected indirectly, which is why it was postulated to begin with. Dark matter was theorized to account for the rotation of galaxies among other things. Gravity (Newton's, as well as Einstein's General Relativity) tell us how galaxies should rotate given a certain amount of mass at their centers. However, galaxies rotate differently than these theories predict for the amount of mass that we can see. The key here is 'see'. We look at a galaxy with visible light telescopes, as well as X-Ray telescopes (among others) and can see how much regular matter is there, because it glows (because it has some non-zero temperature). When it glows, it is releasing radiation, some of which we can see (stars), and some of which is in the non-visible part of the spectrum, which we 'see' with X-Ray telescopes. Anyway, the point is, we can tell how much regular matter is in a galaxy, but it behaves as if there is more matter there. This cannot necessarily be described with just a black hole, which can be very massive, and as light doesn't not escape it, very dark. However, we can tell the size of the black hole at the center of galaxies by the Hawking radiation emanating from it's event horizon (this is radiation emitted from matter that is accelerated towards the black hole). Also, the galaxy appears to rotate not as if there is some extra matter can't see at the middle, but as if it is distributed in a sphere extending in a 'halo' around the galaxy! Since we can't see what matter could be doing this, we postulate that it is dark. This means that it doesn't give off radiation like the normal matter that we're made of, as well as the stars and all the other glowing matter that I mentioned earlier (known as baryonic matter). This implies that it doesn't interact with regular matter via the electromagnetic force, which causes the radiation that we see. So we think that it must be weakly interacting, yet still very massive. This gives rise to the particle known as a WIMP (Weakly Interacting Massive Particle), which we believe is dark matter!

So, LUX is an experiment to detect WIMPs. Remember, they're weakly interacting, not non-interacting. So we try to detect how they interact with regular matter by bumping into the nucleus, rather than the electrons around the nucleus, which is predominantly how baryonic matter interacts. The basic setup for the experiment is a bucket of liquied xenon (very large nucleus, good for WIMPS to bump into) that is very cold, and quiet. When a WIMP streams through the detector (they're streaming through all of us right now, without interacting, or barely interacting with us) it may bump into the xenon nucleus, which gets heated up slightly from the interaction, and emits radiation (light) that we detect. That's it, pretty simple huh? Yes and no. There is a lot of other stuff streaming through us right now, besides WIMPs, which is more strongly interacting. So if we were to turn our detector on right now, on the surface, without any shielding, it would light up like a Christmas tree. This is because all the other particles (cosmogenic muons from the sun, radiation from normal matter that decays in and around us, etc.) interact in the detector too, causing a lot of background noise (signals we don't care about, that are not WIMPS). So we put massive water shields around the detector and go deep underground where most of the radiation from the sun cannot reach. The water shield absorbs most of the radiation from the cavern rock and all the other stuff in the room. Then we use very clever veto techniques to rule out interactions as being WIMPs. For example, a neutron that decayed from the cavern wall might enter the detector, but it when it hits the xenon nucleus it will impart a lot more energy than a WIMP, so we call it a high energy veto, which means anything depositing energy over a certain threshold, is not a WIMP, so we ignore it. Also, WIMPs are so weakly interacting, they are sure to interact only once in the detector, if at all. Other particles like neutrons may interact more than once. So we use a multiple scatter veto to rule them out. Many other techniques like this are used to sift out signals that we know aren't WIMPs, to look for ones that might be.

So far, experiments like this one haven't turned up any verifiable detection of dark matter WIMPs, but LUX will be the most sensitive dark matter detector in the world when it is turned on. Even if it doesn't see anything, we'll be able to rule out a lot of theories for dark matter, which is just as exciting, because it opens up new physics. The great thing about experimental physics is that whether your see what your were looking for or not, you have revealed some great truth about nature that will keep theorists busy for years.

Anyway, that should be enough to keep you busy for awhile, please post any questions, as I'm sure you will have some, unless this is completely uninteresting to you, in which case, thanks for reading anyway.