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Steve Nahn | USLHC | USA

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Magnet’s ramping!

Friday, August 29th, 2008

Just a quicky-the CMS magnet ramps have started in the last few days – this is critical for us, since the last time we really turned on this magnet it was on the surface, about 2 years ago (nearly to the day!). Here’s the plot of the current (in Amps) versus time for the last few days – last night they reached 10 kA, about half of what they eventually plan to get to, but one does these sorts of things pedantically and carefully.  Keep in mind your house probably has 100 A service – so 10 kA is 100 Houses!  That’s a lot, but that’s the beauty of superconductivity.

The CMS magnet ramping up in the collision hall

I believe the plan is to go to 3/4 of full field this evening.   Soon all those event display pictures with tracks will be curving!


Back from the Blogging Sabbatical

Wednesday, August 27th, 2008

Yes, been gone for far too long. July saw the arrival of my family in Geneve for a week, plus a move to new digs sans ethernet but with a great view:
A Porch with a view
Not having ethernet at home doesn’t bode well for blogging – I feel guilty writing when I should be working. But we got our 10 million channel detector working reasonably well, detecting Cosmic rays with the rest of CMS. This is a great step, but the Cosmic trigger rate is considerably less than what we expect at the LHC, so we still have to wait to see how well we’ll do with beam, and it won’t be too long now.

Then August, and a trip to Maine (Acadia NP) to get reacquainted with my family as well as some old friends from Fermilab who we used to go camping with, as described in my first blog appearance by a Quantum Diary writer. It’s pretty obvious who I am in the story. Anyway, 4.5 families of 4 in a house in Maine for a week, no ethernet or even cell coverage there, but we’re all still friends and had some really really good seafood. When I came back, I took my laptop in for repairs, as it did not run and charge at the same time, which added chaos into the normal work day for me. Well, 10 days, two motherboards, one keyboard, and a LCD display cable later it seems to have recovered, although again a week without my laptop doesn’t help the blogging (especially when my kids tie up the home computer during their laconic end of summer…)

But now I’m back, back at MIT, and will try to add my color commentary to the reports we get from those bloggers lucky enough to be there on the front lines. I’ll hop back and forth to Geneve a few times this fall, but in fact as others have mentioned it is very hard to predict exactly when beam will turn on – those who plan to go for “first beam” will probably be disapppointed due to some hiccup which pushes it just past the tenure of their stay. But it will come, of that I’m sure, and all indications are that the hiccups if any will be small. Meanwhile there is a fresh crop of yound and very enthusiastic students just coming in, and someone needs to teach them some Electromagnetism (it helps when your experiment has built the largest doorbell magnet in the world, though that’s not what we use it for…) so we’re off to a new semester.

The activity at the experiment is centered around being ready for the first collisions, the detector is closed up now (finally we cannot try to mess around with the 0.1% that isn’t working normally!  Striving for perfection can be a pain, and counterproductive as well!) and they are starting to run the magnet regularly.  You know how you feel when you are almost to the top of a very long roller coaster climb – anxious and excited about the ride ahead?  Hold on!


Forget Ask a Scientist, ask a Science Reporter!

Saturday, July 19th, 2008

Just wanted to publicly say kudos to NYT senior science editor Dennis Overbye, who has been answering the public’s science questions. He received (at least) 11 questions concerning LHC (probably many more in fact) and I think he sums up the situation rather well, so I invite you to read it yourself. I especially like his last paragraphs, but as I’ve claimed before, it is these people’s job to communicate well, so it isn’t surprising that they are quite good at it.


CMS in Cyprus

Wednesday, July 9th, 2008


If I’m quick I’ll get this in just after Peter’s blog. While ATLAS went to Berne, CMS went to Limmasol (Lemesos) Cyprus for the collaboration meeting. Now, it is rather a critical time, so the wisdom of going fairly far away is dubious, but getting the upper management and riffraff out of the hair of those really doing the work for a while is maybe not such a terrible idea. I’m told it was quiet and people could get work done at CERN. Anyway, I had a good time-Limmasol is a resort town, so it wasn’t particularly serene (think Miami Beach for Brits and rich Russians) but I did get into the countryside a little which was quite nice. Also, my buddy Chris proposed an alternative excursion to the one planned for the whole collaboration, which was very fun, since I only get to do this particular activity once every blue moon. He’s on the right, I’m on the left

In other news, we have tracks in our tracker! Triggered by Cosmics via the muon chambers, with more than 95% of it turned on! So far performance looks really excellent, I’ll provide more details soon


“Good Morning”

Friday, June 13th, 2008

How often do you greet perfect strangers?

I have a great bike ride from Ferney-Voltaire (where I am staying) to CERN: Here’s the route (red line):

My Route from Ferney to CERN

Much of it is on little roads through fields of alfalfa, sunflowers (which are in fact purple when they first flower), poppies, and other plants I cannot identify, just skirting the suburb of Meyrin (I don’t have a camera with me, else I’d post a picture). On my way in I typically come across 5 or 6 random people out walking (usually with the dog) or running, basically just enjoying the nice morning and environs, and each of these people I greet with a “Bon jour” (although my French is terrible) and they return the greeting. That is just how it is done here – quite a departure from the “don’t make eye contact with anyone” standard in the US (at least the urban US), and much more friendly. So usually I’m in a pretty good mood when I get to work.


What it looks like

Saturday, June 7th, 2008

Back at CERN! Good to be here, more students coming in, everybody getting pretty excited. Recent progress in the cavern is the installation of the beam pipe on one side. I guess this is pretty hard to imagine, so I thought a picture might help:

Here's a picture of the Beampipe going into the minus end of CMS

So, on the very bottom of the picture you see these copper looking flanges (they’re not copper, I believe they are Aluminum, but it is just a trick of the lighting). That is the very tip of the first Endcap plug. Underneath those flanges will be the Electromagnetic Endcap, we hope! (there’s been some delay, so it is now “critical path”) Extending from that is the beampipe (eventually the plug will slide over the beampipe) which then penetrates the barrel part of the detector. It might help to have a quick glance at the cartoon before trying to understand the following: from the outside radius moving inward (it is cylindrically symmetric, so this the easiest way to describe it) what you can see is

  • Muon Chambers/Magnetic Field return – the “M” in CMS stands for Muons! This the is the red layers of steel interspersed with aluminum (silver) muon chambers- there are four cylindrical layers of chambers. The red steel in between is where the magnetic field goes so that it can form a continuous loop (magnetic fields have to go in a closed loop, and they much prefer to go through steel than air). They measure muons via the ionization trail they leave behind, and we know they are muons because anything else coming from the interaction region in the center either won’t penetrate this far to the outer detectors or won’t leave a trail at all (those would be neutrinos…) More…
  • Next step in radially: Solenoidal Magnet – the “S” stands for Solenoid. This is the grey collar that looks like it has a whole bunch of metal bands going from the outside to the inside, and every few bands you can see some green cables. The bands are actually cable trays, carrying the cable connections to the inner detectors. The Solenoid itself is 13 m long and has an inner diameter of about 6 m and since it is superconducting cavities inside we can get to about 4 T, making it the most powerful magnet in the world in terms of energy stored. More…
  • (more…)


Progress we take for granted

Monday, May 19th, 2008

Just for fun: One of the fun things about working at MIT is that you have a nice perch to observe the progress of technology. I was wandering around the MIT museum with the kids and came upon this:256 kB!

This object is about 50 years old and approximately 1 cubic meter in size if I remember correctly. Anyone want to guess what it is?


The nomadic summer

Monday, May 12th, 2008

Ah, just spent some time getting the summer organized. The plan of attack is to abandon wife and family for June at CERN, then they come over to visit (feel a little like I’m in prison! They get visitation rights!) for a week in July, plus see some old friends, I head back in August and visit them, and maybe come back to CERN for a bit before returning to MIT for fall classes (which will be interesting, since I am also “course administrator” which is a code word for lots of chores with little fun- it’s one of those things you can really only mess up…).

Plus, there’s a trip to Cyprus for our collaboration meeting. It’s the first CMS meeting away, and so will be pretty interesting. When these meetings happen at the lab, most people tend to ignore the meeting, and focus on keeping up on their regular day to day activities instead. When they put the meeting elsewhere, there’s not much you can do about the day to day, so it tends to be more focused, and therefore more productive. In addition, people tend to spend more time with their collaborators eating and finding entertainment outside of meeting hours, which is better for collaboration building. However, I noticed a very strange thing about Cyprus, which I will share with you.

Cyprus flights

For reasons which are yet a mystery to me, flying to Cyprus for a reasonable amount of money means arriving in the middle of the night. The return is the same way – the reasonable flights all leave between 2 AM and 4 AM. The only flight which doesn’t arrive way early involves a 17 hr with 11 hours at Heathrow (ick). I’m a little worried about why this is, if anyone cares to explain it to me, I guess I want to hear it.

Anyway, it will be very exciting at CERN this summer – and a bit frustrating. Think about finally getting to do what you have planning to do for twenty years or so and then having all these annoying little issues that keep putting things off. This is what it is like, when you have a small chance of something breaking in any of many many components, there is a fair amount of unforseen issues that have to be dealt with. They’re not showstoppers, but with everyone holding their breath for the first interaction, you can get a lot of oxygen deprivation, let’s say. The Tracker cooling is experiencing something like that right now – first time working with the full system, some new issues being discovered or failures of supposedly reliable components, most of which we of the Tracker group don’t even have control over (they fall into someone else’s scope) but we are still waiting to get all the services lined up to be able to turn the detector on fully, and everyone is getting a little antsy. I keep telling my students to get used to it, every detector system goes through these growing pains, and the LHC detectors will be no different…so dear readers I guess you should know too that while I fully believe we’ll get the machine and detectors running, it may take a while, so only hold your breath if you look good in blue.


Earth Day and Doomsday

Saturday, April 26th, 2008

Hi Folks-

In honor of Earth Day (and because I still retain my Badger Pride, in this case for Earth Day founder Gaylord Nelson) I ask you a question: which is more likely, that we will all be swallowed up at the turn on of the LHC, or that we will adiabatically ruin our planet to satiate our increased demands for convenience and “higher quality of life”. The Energy problem/Global Warming/choose your own name for it is getting more and more attention these days, for good reason, and so it has been on my mind. At MIT, we have an Energy Initiative where the Institute as a whole has taken up the energy challenge, and people like Governor Patrick are giving talks to highlight its importance. In the Physics Department, we focus more on technological solutions, but I am not convinced this is the way to go. My brother, who has been working for Wisconsin Energy Conservation Corporation for the last 10 years or so (it has been at this business for 25 years!) tells me that in we currently have the technology to dramatically reduce our energy consumption (working with energy providers, building developers, and ordinary consumers) which is more expensive up front, but in the end saves money as well as energy. It is just a matter of getting people to change their habits-but that is really hard.
My main example of this is during my daily commute. My vehicle of choice is:
My vehicle of choice

which I ride for 10 minutes mostly along a path to a subway (it’s called the “T” in Boston) which takes me to MIT. I ride all year long (thanks to my town of Arlington, which has decided to plow the bike path) except in really bad weather when I take a bus to the T. This has many advantages:

  • With gas at $3.70/gallon and parking at $500/semester it’s better economically (My T pass costs $37/month, subsidized by MIT). By the way, in Switzerland gas was something like $5.20/gal last year, so it is still cheap in the US. Parenthetically, I am continually chagrined by our current leader’s commitment to reduce US dependence on foreign oil – not oil in general, that would be detrimental to the US oil industry, with which the current administration shares some pretty cozy past history, no? OK, I’ll step off the soap box.
  • I get at least 20 minutes of exercise a day, whether I like it or not. I don’t have to set aside extra time for exercise, it is part of my daily routine, and 20 minutes a day, done regularly, goes a long way. And it is outside, fresh air, not cooped up in some health club (which again costs more money)
  • It is faster! Well, if there were no traffic, it might be slightly faster by car, but when in Boston is there no traffic? Actually the fastest way to get from my house to MIT is bike all the way, but the bike back in traffic is no fun (too many cars, too much pollution, too many drivers venting their stress with their driving tactics and their horn) so I usually take the T instead.
  • There is a certain satisfaction I get out of cruising through traffic like a hot knife through butter while everyone is stuck in gridlock.

I’ve been using my bike for commuting since college, except for a few stints here and there when I had to deal with the kids at the same time, and I have to say the driver’s attitudes are getting better. Whereas there was little respect for bikers back in the day, now for instance I cross one road on the path every morning (Lake St) and I’d say 90% of the time cars go out of their way to yield the right of way to me- kudos to Arlington!

Often I have ample opportunity to observe the car traffic flowing around me, so I play a little game. I try to see how high I can count consecutive cars with single occupants, until I see one with more than one occupant, upon which I reset the count to zero. I think the highest I’ve ever counted was around thirty, and it isn’t hard to get to 10 at all. Forget the bike, what if half of those ten people in their car all alone got into someone else’s car – what effect would that have on traffic accidents, length of commute, pollution, parking space, noise, energy consumption…at the cost of being able to come and go as one pleases (but not really, because they schedule around traffic, no?). So I think the real challenge is not necessarily getting the technology but changing the mind set – the arguments are convincing, if you can get people to listen. I have a dream about getting school kids walking to school or waiting for the bus to play this game, and report their maximum count, then chart it as a function of location and time to see which part of the US is the most carpool friendly, but that’s not my day job. Anyway, awareness is what Earth Day is all about, so thanks Governor Nelson

PS I know this isn’t about the LHC so much, but we physicists tend to think about all sorts of stuff…and for readers near Boston, get on your bike duringBay State Bike Week


More press!

Thursday, April 10th, 2008

Well, the Hawaii botanist brouhaha isn’t particularly great, but it did raise the public’s awareness of the LHC, even on radio quiz shows where their non-expert opinion of the nature of the universe just after the Big Bang was “there were no good restaurants”. Probably have to agree with that, although I just got done reading “The Restaurant at the End of the Universe” by Douglas Adams to my kids, so if I couple that with Time Reversal invariance, maybe I can come up with a theory of good restaurants at the beginning of the universe too? All facetiousness aside, I guess (almost) all publicity is good, but we’ll probably do better when Angels and Demons hits the big screen.