Friday Physics Photos: ???

fragile_lasers

 

Ok you guys, I’m doing that thing where as I write my next post, I discover that I have more and more things I want to talk about and the post gets longer and longer … Right now it’s an unreadable mess. While you wait for me to carve that mess up into several smaller messes, here’s a little bit of fun.

On my bike ride into work, I passed by another department’s lab. In their parking lot was this totally inexplicable vignette. I have absolutely no idea what’s going on here and I love it. Somebody write me a short story about this.

Friday Physics Photos: A Scientific Conference

One of the most important things a scientist can do is to share her work with other scientists.  It gives experts the opportunity to ask critical, helpful questions; it lets scientists find areas of common interest; it gives us new perspectives on our work; and it help us to avoid stepping on each others’ toes.  You can publish your work in a scholarly journal or, if you want a more face-to-face interaction with your colleagues, you can present your work at a scientific conference.

Most areas of research have a yearly conference or two, where everybody meets to compare notes and share their most recent results.  Maybe you noticed that I wasn’t posting for a few weeks?  That’s partly because I was at the International Particle Accelerator Conference, hosted this year in New Orleans, LA.

The conferences I go to usually have two parts.  In the morning, we have a bunch of talks.

And in the afternoon, we have a poster session.

The poster session is a bit like your high school science fair.  (Yes, there really is a reason for those things!)  Everybody goes into a big room, you put up posters about your work, and then you stand around answering questions about your work.  Or, you walk around and check out everybody else’s poster.  Also, coffee.

Here's my buddy Ryan in front of his poster. Q: What's with the t-shirt? A: Scientists don't tend to wear suits. Even at conferences.

I’ve given talks and I’ve presented posters.  I actually feel like the poster session is more fun.  The people who are most interested in your research have a chance to speak with you face-to-face.  You end up having some very interesting conversations with some very interesting people.  Giving a talk is considered more high-profile, but it’s hard to have a stimulating dialogue with a dark room full of sleepy people.

I bet you’re wondering what else I got up to in New Orleans.  Well, in addition to talks and posters, the third thing to do at conferences is to have conversations.  For a week, you’re staying within a mile radius of all your field’s experts.  It’s the perfect opportunity to knock around your ideas with some smart people, to start new collaborations, and to brainstorm about the future.  I’d say I was working after hours, over dinner, just as often as I was sitting and listening to talks.

Of course, I couldn’t go to New Orleans and only work.  After talks on the last day, I ran off to the bayou with some friends and met some gators.

No, that is NOT my hand! That is the hand of a trained professional, petting a nine-foot gator.

“Why?”

Are you a regular reader of this blog? Are you really so brave and generous with your free time? If you are a regular reader, you’re likely scratching your head over a pretty significant question I’ve been ignoring.

“Why?”

I’ve told you that accelerators are big, that they’re hard to build, and that they can get very complex.  Why go to all that trouble?  What are these behemoths good for?  Well, here’s a list.  The internet likes lists, right?

    • Fundamental particle physics.  This is the one everybody thinks of first, especially since the term “atom smasher” is so popular.  If you collide two highly energetic beams together (like at CERN, for example), the resulting Einsteinian cataclysm is interesting in all sorts of ways.  You can search for new particles, test fundamental physical theories, and study exotic environments.  You can ask questions like “why is there matter in the universe?” with a straight face and the expectation of some sort of answer.  This all gets very awesome very quickly.
    • Basic physics, materials science, biochemistry, etc.  We can talk about this more later, but with an accelerator you can create ultra-bright, ultra-fast light pulses.  And then you can use those light pulses to study very small, very fast processes.  You can look at how proteins behave to study diseases and create new drugs.  You can design catalytic processes to enable artificial photosynthesis, because if plants can make fuel from sunlight, why can’t we?  There’s a long, long list of things you can do with these “light sources”. In fact, accelerator-based light sources are a HUGE field of research.  More accelerators around the world do this kind of thing now than do the above-mentioned fundamental physics research.
    • Medicine. I know people who have gotten radiation treatment for various forms of cancer.  Typically, doctors will attack a tumor with x-rays.  But the problem with x-rays is that they’ll also attack the healthy cells around a tumor.  A fascinating alternative is hadron therapy. It turns out that you can “tune” a beam of protons (or neutrons, or both) so that they deliver energy to a very specific target volume.  You can use beams of protons (or neutrons, or carbon atoms, or whatever) to attack tumors without so much damage to the surrounding, healthy tissue.  And where do those hadron beams come from?  Accelerators, of course!  I assert that this is cool. 
    • Safer nuclear power.  Nuclear power is generally pretty safe, but last year we all got an object lesson in its potential problems.  I know people working on accelerator-driven nuclear reactors that overcome some of these problems.  If you build a reactor right, you can control the fission process with an accelerator.  No beam, no fission!  This makes things much safer — you don’t have to worry anymore about meltdown.  “Aha”, you’re saying, “but what about nuclear waste?”  Well, it turns out that you can “burn” (really, transmute) nuclear waste with accelerators too.  Really.  I’m not kidding.  Here’s a video, shot at Fermilab:

There’s another hugely important use for accelerators that’s harder to talk about in concrete terms.  They’re hard to build, right?  And they require cutting-edge technology?  The technology that’s developed for accelerators often makes its way into the private sector, and from there into everyday life.  Do you know anybody who has had an MRI scan?  The magnet technology in MRI machines was first developed for bending particle beams in accelerators.

Not good enough?  Maybe you’ve never had an MRI?  Well, have you ever used this “world wide web” thing?

Seriously.  The vast architecture of the internet was developed by many people over a long time.  But the internet that you interact with daily is based on the work of a few people who worked at CERN.  They tried to figure out a better way to share their data, and the result was the World Wide Web.  You know how you type http://danielbowring.net into your browser in order to look at my site?  That’s the result of some people at an accelerator laboratory, trying to solve an interesting problem.

A long post today, I know.  I tried to pad it out with youtube videos, so it wouldn’t just be a vast ocean of text.  But hopefully, at the end, you have more questions now than you did when you started.  I encourage you to ask these questions in the comments section!  At the very least, stay tuned.  I plan to dig down deeper into these ideas (and talk about other uses for accelerators that I didn’t have room for here) in future posts.

Friday Physics Photos: A cryomodule that’s all plugged in and ready to go

Remember how I talked before about cryomodules?  I showed you photos of what they look like as they’re being assembled.  But I also told you (a) they’re complicated, and (b) they have a lot of different jobs to do.  They handle the plumbing of liquid and gaseous helium, they deal with high-power electrical connections, they house diagnostic equipment … it’s a lot of stuff.

Here’s a photo of a cryomodule that’s part of an actual accelerator, with all those connections made:

This one in particular is part of the ILCTA at Fermilab.

Friday Physics Photos: Welding refractory metals.

I’ve mentioned in previous posts that accelerators employ things called cryomodules and that cryomodules are complicated.  Let’s talk about one of the many, many ways that cryomodules are complicated.

Cryomodules have titanium components.  How do you build things out of titanium?  Specifically, how do you weld titanium?

Welding requires hot, hot heat, and when you make titanium (or niobium, or molybdenum, or tantalum …) hot, it starts to suck oxygen and nitrogen out of the air.  If you’re welding titanium and you’re not careful, all of a sudden you’ll have titanium oxide all around your weld.  And titanium oxide is brittle.  It’s weak.  You don’t want a load-bearing joint in your accelerator made of titanium oxide.

Instead, you have to build a box around the thing you want to weld and then blow argon past your weld joint.  The argon keeps oxygen and other atmospheric gasses away from your weld.  (Argon is a noble gas and is too snobbish to react with something as déclassé as titanium.)  Here’s a photo of that thing I just described:

Admittedly, there’s not a lot of physics going on in this photo.  I just like this thing because it looks like a UFO.  Actually, it reminds me a whole lot of these little plastic space ship toys I used to get at the National Air & Space Museum.

I have a couple secret goals with all these photos.  (1) I want to give you a sense of how complicated it can get to build a particle acccelerator.  (2) I want you to understand in rough terms how an accelerator gets built.  How am I doing so far?  Leave your questions and suggestions in the comments section!

Friday Physics Photos: Accelerating cavities.

Quite a few posts ago, I gave a super-brief overview of accelerators. I said they were the distant cousins of tube televisions, yes?  I acknowledge to you that this analogy is pretty silly, even if it’s apt.  But now let’s talk about how things get accelerated in the first place.  You do this with a cavity.

A cavity is just a hollow hunk of metal.  If you run electric current through the walls of the metal hunk, you’ll get electric fields in the hollow part.  And if you shape the metal hunk just right, those fields will have a certain shape.  An electric field applies a force to a charged particle in a specific direction.  So now do you see where this is going?  If you build a cavity right, you can send particles through the cavity in such a way that the cavity fields give those particles a push.  Do this enough times, and you’ll have some pretty fast particles.

How about some numbers?  Let’s say that high-tension power lines support roughly 100 kilovolts.  A cavity – much like the ones I’m about to show you – can apply 100 times that voltage to an electron.  How about some cooler, more rock-n-roll numbers?  Lightning is complicated, but Wikipedia says – roughly – that an accelerating cavity supports electric fields 10-100 times larger than what’s required to initiate a lightning strike.

Boo-ya.

Here’s a photo of an accelerating cavity:

Some notes about what you’re looking at:

  • The cavity itself is that five-lobed-hourglass thing.  Everything else is support, dressing, and power couplings.
  • This is a display model that’s standing on end, so that the hypothetical particle path goes up-and-down rather than the customary and more reasonable side-to-side.
  • It’s made of niobium, which is a superconductor at low temperatures. Remember I mentioned that accelerators use superconducting gizmos sometimes?

It can be hard to look at a structure like this and visualize exactly how this could be useful in accelerating particles.  Lucky for you I did some computer simulations of cavity fields at work that I haven’t ever used, so I can recycle them in this blog.

Here’s a cartoon of the electric field lines in an accelerating cavity.  You can see the wavy hourglass-type outline of the cavity structure.  The arrows represent the electric field, color-coded according to strength.

Properly speaking, this is the top half of a cross-sectional view of a cavity.  Anyway, the important part is down at the bottom, which represents the beamline.  That’s where the particles go: across the bottom of the picture from left to right.  You can see that the electric field lines all point in a straight line, pushing the beam from left to right.  That’s how it’s done, son!

PS, If you look closely, maybe you’ll notice some weird things about the shape of the electric field lines in this picture.  I assure you, those weird things are normal.  But if you’re feeling curious, then by all means ask a question in the comments section!

Friday Physics Photos: A class-10 cleanroom.

Remember the other week, when I told you about cryomodules?  And I mentioned how the beam pipe was sealed off in order to keep it clean?

Cleanliness turns out to be a big deal for accelerator components.  This is especially true of the pipes and cavities through which the beam runs.  The tiniest little bit of dirt or moisture can give off gas atoms, which can scatter the beam if they get in the way.  To briefly understate the issue, this is bad.  Particle contamination can also cause sparks, weird parasitic electron behavior, unwanted heating, and a few other problems that you wouldn’t normally think about.  Building accelerator components really makes you reconsider what it means to call something “clean”.

So let’s put some numbers on it.  A human hair is maybe 0.1 millimeters thick.  Imagine a particle 1000 times smaller than that.  Now imagine a room so clean that there are less than 350 particles that size floating around in every cubit foot.  This is what that room looks like:

Unless you happen to work in the semiconductor industry, this is the cleanest room you have ever seen.

There’s a technician in there, assembling some very clean hardware.  Here’s another way of understanding just how clean this room is: That technician had to train for something like 1.5 years in order to learn how to work in such a rarefied environment. You have to handle tools in a very specific way to, for example, avoid stripping a nut and sending microscopic metal shavings everywhere.  In there, you can’t even scratch your nose if it itches!  It would send a bunch of skin cells into the air around you and those might settle on the parts you’re assembling.  Or maybe oil from your skin would get on your glove and then on to the part you’re trying to keep clean.

Maybe now you’re thinking “oh that’s no big deal, I never scratch my nose”.  Ok, so (a) yes you do, and (b) imagine putting on a full-body suit made of synthetic fabric, going into a very, very dry, very air-conditioned room, and then knowing you can’t ever ever scratch your nose, no matter how much you want to.  I guarantee you’ll be going crazy within ten minutes.  Scratching your nose will be all you can think about.  Those cleanroom technicians have iron wills, let me tell you what.

Are you scratching your nose right now?

Let’s do a new thing: Friday Physics Photos

It pains me to say this, but sometimes I’m too busy to make blog posts.  It’s not that I don’t love you, dear reader.  Even when I’m not writing to you, I think about you.  In fact, it’s especially when I’m not writing to you that you’re on my mind.

So let’s try this new thing.  Every Friday, I’ll post a photo of some cool particle accelerator thing along with a short li’l description.  If I keep them short, I can totally keep to a weekly schedule.  Bonus for you: short = readable!

Let’s start with this one:

That giant yellow thing is called a cryomodule.

Ok, so you know how your laptop gets warm after you’ve used it for a while?  That warmth comes from electric current moving through copper.  Copper is a good conductor but it’s not perfect.  Some of that electric current gets dissipated as heat.

Accelerators can require huge electric currents, either to power magnets that steer the beam, or to create huge electric fields that accelerate the beam. (Remember, we talked about this?)  Well, so if copper gets hot in your laptop, think how hot it would get if you pumped megawatts of power through it.  Instead, accelerator components can be built with superconductors.  Superconductors have perfect DC conductivity, and near-perfect AC conductivity.  So you can move those huge currents without melting your machine.

What does all this have to do with a cryomodule?  Well, superconductors need to be cold in order to work, where “cold” usually means “a few degrees above absolute zero”.  This means you need to flow liquid helium (which is really super cold) across your superconducting components.  A cryomodule accommodates and insulates all that insanely complex plumbing.  It also manages the electrical transition between a cold superconductor and a room-temperature power source, houses tuners and diagnostic equipment, damps mechanical vibrations, and does some other stuff that it would take too long to explain right now.

Look, here’s another photo of some cryomodule innards:

You're looking at a low-quality cell phone photo of a shockingly complicated device.

Surprisingly, that big open pipe is not where the accelerator beam goes.  It’s the return pipe for the helium, which evaporates as it soaks up heat from the accelerator.  The beam pipe is just below the gas return pipe, and it’s sealed off so that it stays clean and pristine.

Next Friday: The cleanest room you have ever seen.

What does an accelerator look like? Part 4: The outsides.

I’ve spent a couple posts now talking about how particle accelerators are complex and cool.  I’m going to try to persuade you now that they can be beautiful, too.  Certainly, they’re beautiful in a conceptual way.  I think I’ve made this point before.  Herculean efforts by scientists, engineers, politicians, and taxpayers to explore the universe and gain fundamental understanding of what it means to be a human being … well, it gets me all choked up.  But for the purposes of this post, when I say that an accelerator can be beautiful, I mean beautiful in a purely aesthetic way.  Accelerator laboratories can be lovely places to spend the day.

They can sometimes look like office parks.  I concede this.  Here’s a photo of the main campus at SLAC:

This is where they play soccer during the lunch hour.

But look.  Fermilab has an area of about 10.6 square miles (27.5 square kilometers).  Here’s a few photos of the lab, taken from the 15th floor of the Wilson building.

You can see the curve of the main accelerator ring here, bordered by a kind of pond. It's about 4 miles around.

Almost everything you see in this photo is part of Fermilab. There are a few buildings on the horizon that are part of the neighboring town, Batavia.

The point is, these places can get big.  They need to be big to house the accelerator and all the supporting infrastructure.  But a lot of that stuff is underground.  What do they do with all that land at ground level?  They do stuff like this:

Fermilab is also home to a bison ranch.  Really.  In fact, they take conservation pretty seriously.  I bet you don’t picture this kind of thing when you picture particle physics:

This is as close as I could get. Their enclosure is pretty big and my zoom lens isn't super powerful.

Of course, not every lab is big enough to house farmland and nature preserves.  Lawrence Berkeley National Lab, where I work, just happens to be built in a beautiful place.  Here’s a photo I took as I was leaving my office one evening.  You can see the Golden Gate Bridge down there at the bottom, as well as parts of San Francisco, Sausalito, Mt. Tamalpais, and the city lights of Berkeley.

It almost makes it hard to leave work at night. By the way, I took this photo with the camera in my mobile phone. The colors aren't touched up at all. If anything, they're more drab than it looked in real life.