When in the Course of Particle Events....

People often ask me "What is ATLAS?" -- which is a difficult question to answer, as it's a highly complex and massive device. In short, it's a general purpose particle detector, which means it's designed to help study a range of phenomena from the Standard Model to SUSY to things beyond our ken. The ATLAS detector has four main subsystems: the Inner Detector, the Calorimter, the Muon Spectrometer, and the Magnet System. My own work involves the Muon Spectrometer -- specifically the End Cap, but that's matter for another post -- but some of more exciting developments of late have occurred in the Magnet System.

The Magnet System is what bends the charged particles produced in each event allowing us to track them and deduce the charge and momenta of these products. As the particles are going nearly the speed of light, the magnets need to be extremely powerful: the Barrel and End Cap toroids generate 3-8 Tesla (T), while the Central Solenoid generates 2 T. How powerful is this? Well, the Earth's magnetic field ranges from 30 mT to 60 mT (the largest values being, unsurprisingly, at the magnetic poles where the magnetic flux lines converge). So the magnetic fields we'll be generating at ATLAS are up to x100,000 the Earth's magnetic field. For this reason, it's strongly recommended for people with pacemakers not to do calisthenics in the Pit when the detector is functioning.

At present, the folks over on Team Magnet are ramping up their tests in the Pit (where the detector does its business). They recently ran a successful test at half the final operational current of 20,000 Amps (A). Yes, you heard me: 20 kA. Forget going up to 11, this sucker is electrical. For reference, heart fibrillation can occur at low voltages (110-200 V) from 60 to 300 mA (depending on AC or DC and path taken to the heart) while a bolt of lightening usually has 30 to 300 kA.

While the test at 10 kA was successful, reaching the halfway mark current-wise doesn't spell smooth sailing from here out. Why not? The current induces a magnetic field (which is the whole point of the current), which then creates a force on the superstructure of the system: the magnetic force essentially tries to bend the system (which is an oval) into a minimal energy state (a circle). So how does the force depend on the current? Let's go back to E&M and first recall Gauss' Law and the Lorentz Force Law....

Guass' Law states that (in a properly chosen geometry) the magnetic field is proportional to the enclosed current. The Lorentz Force Law tells us that the force created by a magnetic field is q v x B (I'll try and upload some nice equations later, but I can't right now). With a little algebraic trickery, we can restate this as I l x B. As B ~ I, we get that the force is proportional to the square of the current.

So the 1/2 full current test is really just 1/4 of the force the system must withstand. Fortunately for us, there will be a full test this weekend to see how the whole thing holds up. Here's hoping....

All Thimfu Fall Apart

Bhutan has always fascinated me. In some ways, they are rather archaic, almost Amish -- the king lifted the ban on TV and the internet only seven years ago. But, they also are rather progressive: the king can be impeached by the National Assembly.

In my youth, two facts remora-ed themselves to my brain: their largest export was stamps and everyone celebrated their birthday on same day -- New Year's. Sadly, both of the these facts are not true -- though the former was true until 1974 when tourists were first allowed into the country; I blame my beloved National Geographic Atlas, printed in 1974. False the latter fact may be, it still resonates with me in some way. Why should one's own New Year not start on one's birthday? One's entry into the world surely must be considered new.

My own birthday was last Wednesday, the 25th of October -- savvy readers who will do/have done well at Geekfest know that this is the same day as the Council of Elrond -- so I set about to write a set of resolutions. They are as follows:

Respond to friends/family within 24 hours
Do 100 push-ups and crunches per day
Read one Shakespeare play per month
Take one photograph to be proud of per month
Find 5 restaurants worthy of taking friends/family
Go skiing in the Alps
Go hiking in the Alps and Jura
Watch 10 Best Picture winners
Memorize two poems
Learn to drive stick
Save $200 per month
Make one recipe from each cookbook per week
Read Paradise Lost
Blog at least once per day
Read 5 Booker Award winners
Read 5 Pulitzer Prize winners
Bike around Lake Geneva
Work through Peskin

Some are for fun, some are for self-improvement (all you Tyler Durdens out there can just keep your opinions to yourself), some are ambitious, some less so. Some of you will note that one resolution is to blog once or more a day. In the spirit of this resolution, I've started a new blog.

Some may ask why I've started a new blog when I had one already. One word: tagging. I've always wanted tags, so I signed up with Blogger's beta to get my hands on them. I also want to have a bit more focus on physics -- both for friends and family who keep asking the nagging question "so what exactly do you do?" and in the spirit of autodidactism -- so I've tried to reflect that in the design. If you faint when people start discussing the Standard Model, fear not, for I bring tidings of great joy: I'll also be posting about food, ex-pat culture, movies, TV, photography, sports, books, and anything else that strikes or tickles my fancy.

I'd also like to engage friends and visitors, so if you have a comment, a question, or whatever, please post it. If it's a question, I'll see what I can do about dedicating a post to answer it. As an aspiring teacher of physics, I hope to refine my pedagogy a little here, too. If you have a blog of your own, feel free to respond to me there, too. I think dialogues between blogs can be a lot of fun, so I'd love to engage in some -- just make sure I know about your blog.