Physics students become interested in physics because they want to understand the universe and typically excel in problem solving, but do not necessarily understand the daily work that experimental particle physics entails on a day-to-day basis. Upon leaving the CERN program, some people were inspired to do particle physics, while others were dissuaded. It was a very positive experience insofar as it really helped students discover what they wanted to do at an earlier point in their careers. This is incredibly useful, as introductory physics courses do not typically address it. It also opened opportunities to people to pursue other, related careers. For instance, one student is now pursuing medical physics, as much of the scientific knowledge needed runs parallel to this field.
The study abroad experience was also life-enriching. Few students, particularly those in STEM fields, have the opportunity to take courses in another country and be completely immersed in another culture and language. Our courses were taught in French and we interacted with the Swiss students on a daily basis. I think many universities try to be more protective of their students-they may study abroad but not experience real immersion. We learned to adapt and acquire communication skills that many young scientists do not attain.
We also were exposed to practical skills and were able to participate in the research evolving at the time. Many of us acquired programming as well as electronics skills. We encountered common obstacles in experimental physics research and learned to overcome them. We were able to learn about a variety of scientific research topics besides simply the search for the Higgs boson. I recall once listening with fascination to Dr. Sulak’s description of the ANTARES underwater telescope in the Mediterranean, and how it could even detect bioluminescence. The entire program gave me much more perspective that I think other new physics graduate students may not necessarily have.
Some advice to future interns:
(1) Take advantage of the occasional snow-shoeing trip, etc. That one trip will not make or break your grade. Do not be like me and persist in being a workaholic while missing out on some cool life experiences. When you are 80 years old, you’ll probably remember not going on the snow-shoe trip, but you won’t remember that you got a few points off on your partial wave analysis problem set.
(2) That said, do all your homework, despite the fact that the academic culture is a bit more laid back in Europe. You need to make sure you are still in line with your peers when you get back home to the US.
(3) Try to get as many people to show you what they are doing at CERN as possible and be really proactive about talking to different people there. This is a really good chance to network.
(4) If you find that you are getting claustrophobic studying in the dorms, head to the library. There are also nice places to study at UNIMAIL on the top floors.
(5) Try to speak French as often as you can. Don’t let the fact that you are often in a large group of Americans dissuade you from trying. It can be awkward, but it is not as difficult as you may believe.
(6) For the exams: The oral exams are not prevalent in the US. Do not worry too much if one does not go as well as you hoped. There is a bit of luck involved as you have to draw a question randomly and respond on the spot. I noticed that the European students are more aware of this and take everything in stride. Still, as always, preparation is key! Just don’t be too hard on yourself if the results are not what you expected.
(7) Be aggressive and energetic about your research and try to look for interesting projects outside of your more academic work. In other words, use Larry Sulak as your role model!
The Boston University Geneva Physics Program was incredibly meaningful to me. Since I attend a liberal arts school, my semester as part of the program was my first to focus entirely on physics, and I joyfully soaked up all the physics knowledge I could. Luckily, I found that CERN was full of many incredibly brilliant people who enjoyed explaining their work to a curious student. I worked as part of the Antihydrogen Experiment: Gravity, Interferfometry, Spectroscopy (AEGIS) collaboration. I fabricated scintillator detectors and took part in AEGIS’s first beam time. It was my first experience with a running experiment, and it was exhilarating. I acquired many new research skills associated with the work I did. In addition, participating in an international collaboration afforded me the opportunity to meet many physicists and engineers from across the globe. Watching the team leaders of AEGIS in action also gave me the opportunity to learn about effective leadership of a diverse, international team. The independence my mentor gave me, in addition to the structure of the courses at the University of Geneva, taught me that self-motivation is a necessity in order to do meaningful work. In short, I could not have asked for a better experience as part of the BU/CERN program!
Next year, I will begin pursuing my Ph.D. in physics at the University of Pennsylvania. I’m still deciding between research in experimental cosmology and high energy physics. Regardless of what I choose, I know that my experience as part of the BU/CERN program will provide me a solid foundation on which to build my career in physics.
Please contact me (email@example.com) if you have any questions about the program!
The BU Geneva Physics Program offered me a wealth of opportunities. As a student from a small liberal arts college, I did not have any previous experience working with a large collaboration of physicists, let alone at an institution solely dedicated to one subfield of physics. I greatly enjoyed doing research on ATLAS, learning a lot from my professor and the other students in the group. I fell in love with CERN and with experimental particle physics. I gained critical research skills as well a greater sense of confidence in my abilities as a physicist, both of which I needed at this time in my life to be able to continue on in the field. This program was instrumental in shaping my career path; I will be starting graduate school in the fall at Johns Hopkins University, pursuing a Ph.D. in physics and working with the JHU CMS group . I cannot imagine a better way to have spent Spring 2012 and I hope that this opportunity is available to undergraduates for years to come.
I’d be more than happy to answer any questions about the program at firstname.lastname@example.org.
Larry asked us to quickly respond to the prompt: “What the BU/CERN program meant to me”. Here is a brief response.
During my time in the BU/CERN physics program I participated in the R&D of the Electron Muon Ranger (EMR) for the Muon Ionization Cooling Experiment (MICE). I was tasked with testing and analyzing the performance of 217 old photomultiplier tubes. I helped in the construction of a cosmically-calibrated test bench, and later wrote code to analyze and interpret the data that we collected. A summary of the work I performed is included in an internal MICE note (http://mice.iit.edu/micenotes/public/pdf/MICE0383/MICE0383.pdf). As a MICE collaborator, I learned how to utilize experimental techniques such as analog to digital conversion, data acquisition, and use of an oscilloscope.
The BU/CERN physics program was an overwhelmingly positive experience for me. As a participant in program, I was able to attend many CERN conferences and colloquia (including the Higgs discovery seminar). This gave me a good sense of the world of high energy physics research. I became privy to the field’s jargon, and learned much about the process of experimentation for high energy physics. This stimulated an intense interest in the field.
Though I am currently searching for jobs that will make use of the skills I gained in Geneva and subsequently, I have not lost my zeal for high energy physics. After I have gained some more working experience, I aspire to pursue graduate studies in the field.
If any current or prospective participants in the program have any questions, I can be reached at email@example.com.
If your lab is far and if you stay for the summer (which I highly recommend by the way!), you need to follow a few tricks for keeping your CERN bike past the 3 month loan period. After the first 3 months, the bike shop will let you renew the loan for another month one or two times but towards the summertime, the bike suddenly becomes highly coveted for summer students. So beware and keep your bike away from the bike shop and out of plain view (i.e. don’t even park it outside main buildings because people will come around to check the racks for bikes that are past their loan period and confiscate them). Even if something is wrong with your bike do NOT bring it to the bike shop or it’s doomed. I had my bike taken away when I tried to get the gears on it fixed and other people (including Larry himself) had their bikes taken right from their racks.
P.S. if all this seems too much of a hassle, just try to buy a used bike off the CERN market or through local friends as soon as possible. If you manage to sell it by the end of the summer, it might not even cost you anything.
-Research the European University system before you come to Geneva. It’s very, very different than what you’re used to. Teachers will not coddle you at all, homeworks don’t count for much, and your entire grade will likely depend on a grueling 4 hour final exam (possibly an oral exam too).
-Attend most, if not all the lectures. It’s the best way to keep up with all the material and know exactly what you’re expected to know. You WILL be tempted to skip classes especially if the French phases you but try to at least follow along in the textbook during lecture. Chances are the lecture will follow the book pretty closely.
-Ask the professors and TF’s as many questions as you need. The professors don’t hold office hours but you can meet with TF’s outside of classes and talk to professors during the 15 minute breaks in the middle of class or before and after class. They are happy to clarify concepts in English.
-Talk to your classmates. They know how the system works and can give you some pretty helpful tips.
-Put off or not do homework. Attempt ALL of it even if you don’t need to. It’s the best practice for the final, I promise.
– Underestimate the final. Keep up with the work through out the semester or you WILL panic for an entire three weeks before the final.
Research at CERN
Just because most people’s minds immediately go to the Large Hadron Collider when they think of CERN, doesn’t mean that’s the only project at CERN. It’s true that the main focus of CERN is LHC particle physics but an amalgam of smaller and larger labs also research things like medical physics, clean energy, and antimatter. If you have any particular interests, do your research! Larry has crazy connections and can probably get you into any lab at CERN if you want it badly enough. Thanks to that, I now work in a medical physics lab developing medical imaging systems to work with cancer radiotherapy.
-housing in Geneva is expensive. the best deal is with the CERN hostel in St. Genis, however it gets fill rather quick and a few months before summer they reserve the spaces for the summer students so, as soon as you get your CERN IDs book it if you know your staying. this will save you hassle and money.
-Also there will probably be a lot of drama with the flights. BU pays for a group flight which leaves June 30th-ish. if you plan to say longer many people found that it was cheaper to get the refund for the flight and book it your self. However, if you know you want to stay during the summer then as soon as you get your study abroad package that has the info for the flight, call up the travel agency that BU has the deal with and have them immediately change the return date. also when you are accepting your flight there is a option to request later return date that makes this process easier. you can always change the return date of for a price of course and it gets ridiculous quickly.
NA62 is attempting to measure the branching ratio of the positive Kaon to positive Pion plus neutrino/anti-neutrino pair decay (meaning that the positive Kaon turns into a positive Pion and a neutrino/anti-neutrino pair). A branching ratio essentially tells us the frequency with which such a decay will occur. These can be measured or predicted by the standard model. For the Kaon decay NA62 is looking at, the branching ratio is about one in ten billion. This means that, one in every ten billion decays of a positive Kaon particle will produce a positive Pion and a neutrino/anti-neutrino pair, very rare.
The experiment consists of 8 modules, each module has 224 straws, half of which run perpendicular to the other half. The modules look like this:
There will be 8 of the these modules lined up along the beam line, each one represents an individual tracker. The straws in each module, that’s 224 straws, represents both an X and a Y coordinate. One set of 112, is aligned in the way shown in the picture and the other 112 are aligned perpendicularly, above the first set. This arrangement allows for the X-Y plane to be drawn, which is important for performing track reconstruction on the incoming particles.
The detector, as I’ve said, has 8 modules, but each 2 modules creates a view, so the detector has a total of 4 views. This is to provide more robust and accurate data; each view consists of 2 modules rotated forty five degrees from one another. So if one module represents X-Y then the rotated module represents a new set of coordinates, called U-V. With another set of coordinates, we can achieve much more accurate measurements of the particles position and therefore our track reconstruction becomes considerably more accurate.
The detector is of the gaseous breed; we use an Argon/CO2 mixture with a high voltage tungsten wire running down the center of each straw. In general, charged particle will enter the gas region of the straw; this will cause electrons to be knocked off in a statistical pattern. The wire running down the straw is set at a certain voltage (with the edge of the straw set to ground), so the electrons will accelerate under the incident electric field. This acceleration will cause more electrons to be knocked off, causing an electron cascade. This will then be read off by the electronics connected to the center wire.
Each straw then represents either an X or a Y coordinate (depending upon the orientation of the chamber relative to the path of the particle). Since the straws in the X direction are going to be in front of the straws in the Y direction, any particle that enters an X straw will also, inevitably, also hit a Y straw, thus giving us our X,Y position. The same logic holds true for the U-V set of coordinates.
That’s the gist of the experiment; there are, of course, many more intricacies that I haven’t relayed in this post. Below you’ll find a link to more documentation and my email address if you have any further questions.
So up until now, I’ve been explaining the whole of the NA62 experiment, but I haven’t mentioned what my actual contribution is. I have been working with the prototype of the NA62 straw tracker (the modules) and of an independent tracker called the MicroMegas detector.
A prototype of the main detector; using the same technology and principles.
Here’s the prototype:
The straws in the prototype run parallel to that length of it, each one also filled with the aforementioned Ar/CO2 gas mixture. The straws in this prototype operate exactly like the straws in the main detector. Each one has a wire running through which reads off the electron cascades, giving us a coordinate. Although we do want to test this prototype, the physics behind it are fairly well understood (the creation and implementation of the software is where all the work went into the prototype).
However, we have the MicroMegas independent tracker:
The MicroMegas (herein, MM) is a detector that operates completely outside of the prototype straw detector. It has two stations each comprised of two chambers; the stations sit on either side of the prototype (in the picture above you can see them below and above the cylinder). Each chamber consists of four major components: the stainless steel drift, the gas chamber, the mesh and the read-out strips. The drift is set to a certain potential (-900V) and the mesh is set to a different potential (-500V); in between these is the gas chamber. So, like in the straw detector, the particle enters the gas chamber and knocks off some electrons. These electrons are accelerated toward the mesh. The mesh, being permeable, allows the electrons to pass through into the another gas region, but this region is tiny compared to the main gas chamber, but the potential difference (since the strips are at ground) is 500 volts. This causes a fairly large electric field which massively accelerates the electrons, again causing an electron cascade. These electron cascades (as there are multiple for each particle) are then read off by the electronics (the strips).
Here’s one chamber:
The description I gave works best if you visualize the chamber in the transverse direction; that is to say not top down but rather a side-on view.
At this point, some of you may be wondering how we know to collect data. We can’t see the particles. Even if we could, they’re traveling at close to the speed of light, so every time we’d notice one, the particle would be halfway across the world before we could hit the button to try to record it. So we need something that can automatically trigger the data collection when it senses a particle, and it has to do it fast.
The black box you see on top of the chamber is the solution, it is called a scintillator and essentially what it does is wait for a particle and when one enters it, it emits an amount of light. That light is then read into a bunch of electronics which tell the computer to start collecting data and all of this happens before the particle enters the gas chamber (which is directly below the scintillator). We call this process the trigger (since it triggers the data collection).
Each MM chamber is either an X or a Y coordinate, depending upon it’s orientation, the green boards in the picture are oriented parallel to the strips, when a strip is hit, it reads out and that would be considered an X or a Y. Then the particle enters the second chamber (below the first) which is oriented 90 degrees from the first chamber. The same thing happens and we get our Y coordinate. Putting these together, we have an X-Y plane with the coordinate of the particle. Two of the chambers, separated by a meter or so will give us two X-Y planes. So, we have a particle that hits the top two chambers (producing an X-Y coordinate) and then the bottom two (another X-Y coordinate) and a separation distance. We can use this information to recreate the track the particle took. It is possible for a particle to hit the first station and miss the second, but in the lab we used cosmic rays (charge particles from space) which, for the most part, are relatively orthogonal to the planet’s surface.
For both the MicroMegas and for the Straw Prototype, we had the daunting task of developing the software that takes the collected data and expresses it in a form that we can actually use. This entailed decoding the data so that instead of having just counts of electrons (since that’s really all we get), we have things like millimeters or charge units. We have to take the raw data and turn it into something useful. Then we take that data, calibrate the the chambers (essentially find out how the software reads some of the dimensions of the chambers) and perform track reconstruction. This means that we construct the path the particle takes to travel through the detectors. All the software is written in C++ and ROOT.
In order to test the prototype more effectively, we ran the detector in the test beam and collected data from there. Here is our prototype set-up in the test beam area:
The test beam is a particle (hadron) beam which we have some control over and runs at 120 GeV. This beam is taken from the SPS (Super Proton Synchrotron). Having the beam is incredibly useful because it allows us to get hundreds of events in mere seconds whereas when using the cosmic rays, we’d have to collect data for days in order to get a couple of thousands of events. Also, with the beam, we get particles streaming into the chamber that are collimated (meaning the beams of particles are parallel) which allows our software to be more accurate and thus our results are considerably more robust.
Once we’ve tested the detectors, our software will become apart of the full NA62 software package and will run alongside many of the other pieces of software produced for the main experiment. If you wish to know any more about the experiment, you can go here and you’ll find more documentation or you can ask me directly at firstname.lastname@example.org.