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[2015] Final day in Switzerland

2015-01-30 - Since our bus departed at 8:00, many students chose to wake for breakfast around 6:30 or 7:00. Others, like the inhabitants of Room 24, decided that it would be more wise to stay asleep until 7:40 to capitalize on the late departure time. Nevertheless, everybody had enough time to eat some breakfast before our whole group set out for a day of touring the Swiss countryside, villages, and castles that border Lake Geneva. Originally, we had planned to travel to Chamonix in the French Alps, a famed ski town that hosted the original Winter Olympic Games in 1924, but 40cm of snow had already fallen there by Thursday and another 62cm were forecasted for Friday. (As it turned out, both highways that pass through Chamonix were closed Friday morning due to the extreme weather conditions.)

Our driver, a jolly man, suggested some of his favorite destinations within driving distance of Geneva, which we decided to go along with because of his expertise. Our first destination was a combination gift shop/cheese factory located in Gruyeres, where we got a first hand view of the aging process for Swiss cheese. Some people also purchased gifts, which ranged from cowbells to Swiss chocolate .

Then, we drove closer to the namesake chateau of the village, which is located on top of one of the many hills in the region. Walking the final part of the way to the chateau, we passed by the Museum HR Giger (named after the Swiss man behind the Alien films) that focuses on surreal and biomedical art and the Alien themed bar that lays opposite the street to the museum.

The chateau, which was home to 19 different Counts of Gruyeres, features turrets and parapets unlike many of the famous, more decorative chateaus of Europe.

While some of us finished up in the castle, others had fun with the snow.

Returning to the bus, some of us played the American card game "Liars Poker" (not for money!) to occupy ourselves as we travelled to our next destination, Chateau de Chillon on Lake Geneva. Others, especially those in the back of the bus, slept instead. The castle was undergoing some external restoration, but the view from the coast of the surrounding Chablais Alps was beautiful.

For lunch, we hopped on the bus to the small town of Montreux for kebabs, pizza, risotto, pasta, and fondue. Once again, the view was gorgeous, but the snow proved to be much more entertaining.

Freddie Mercury, the lead vocalist for Queen, adored the town of Montreux, where he recorded many of his songs between 1979 and 1991. The Freddie Mercury Memorial rock concert takes place every year in Montreux, where a statue to the proclaimed "lover of life"Â stands in homage to his recording career.

After finishing up with lunch, exploring the town, enjoying the waterfront, and "playing" with snow, we reboarded the bus to move on to our final destination, Lausanne and the Musee Olympique. The museum covers the history of the games, but also includes a sculpture of rotating abs (yes, you read that right), a high jump bar displaying the event world record, and a 100m track on which one can race Usain Bolt.

After departing, about 10 of us filled our travel time on the bus by playing the game known as "Werewolf" or "Mafia," which has almost identical rules across the Atlantic (we played with two werewolves, one witch, one cupid, and one fool). Like usual, the students in the back of the bus slept.

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[2015] Final day at CERN

2015-01-29 - Due to a slightly later departure time (huzzah!), many of us woke up later than usual and relaxed a bit before breakfast. At 8:00, we left the hostel and took a tram to CERN. We met Dr. Ren, Alex, and Daniel for a tour of ATLAS (A Toroidal LHC Apparatus) and COMPASS (Common Muon and Proton Apparatus for Structure and Spectroscopy), two CERN experiments with entirely different designs and purposes.

Unlike the ALICE, CMS, and LHCb experiments, ATLAS is the only LHC detector experiment located in Switzerland, directly across the street from the main CERN campus. Instead of taking a CERN shuttle like yesterday, we walked to the above-ground ATLAS control center to learn more about this cylindrical general purpose detector and the data acquisition algorithms that make ATLAS an effective tool for experimental particle physics. Since the LHC will begin operating again in a few months, the ATLAS chamber has already been sealed off from the public, allowing engineers to work more closely with the detector.

Unfortunately, nobody told our guides that a training session for members of the ATLAS project would be concurrent with our visit, which prevented us from viewing a computer model of the ATLAS detector through 3D glasses. Instead, we discussed the detector in the lobby where explanatory posters, samples of the materials used in the construction of ATLAS, as well as a view of its control room. Dr. Ren, a senior researcher at CERN and the LHC who focuses primarily on the calibration of particle detectors, emphasized that ATLAS must be able to extract meaningful physics from the 40 million beam crossings that occur every second inside the detector chamber. At 25 megabytes of data per crossing, ATLAS has the capacity to generate approximately one petabyte of data per second, which would be intractable for any computing network within the budget of CERN.

Alex, a CMS engineer, emphasized the implications of the research going on at ATLAS, specifically, the Higgs Boson. With the discovery of the Higgs Boson, astrophysicists are hopeful that the corresponding Higgs Field explains the exponential inflation of the Universe shortly after the Big Bang. The Higgs Field is a scalar field within the geometry of space and time, meaning that at any given point in space and time, there is a value associated with it, relating to mass. Though the connection between universal inflation and scalar fields requires advanced knowledge of astrophysics, our guide pointed out that the Higgs Field may not be the same field needed to match the theoretical field associated with inflation. Because of supersymmetry, there may be even more types of Higgs Bosons at higher energies! With so many discoveries to be made, Particle Physics has become quite the exciting field recently, and physicists are eager to run more and more experiments to collect more data.

However, a vast majority of the calorimetry and spectroscopy data generated by ATLAS is extraneous, describing physical phenomena that we already understand fully. To use the Higgs boson as an example, two of the most common decay channels (two muons and four electrons) occur once in less than one billion proton-proton collisions. This allows for lowest level trigger of the ATLAS experiment to eliminate the data from all proton-proton events that lack these appropriate signatures. The low-level trigger must be able to differentiate between definitely not Higgs-containing and possibly Higgs-containing events efficiently, effectively, and, most importantly, without error. Within 25 nanoseconds, the trigger must make a decision on whether the event should be accepted or rejected.

After passing through another two rounds of triggers, only one hundred megabytes of data is preserved per second. This data is forwarded by fiberoptic cable to the CERN data center, which fully reconstructs the event, commits it to magnetic tape memory, and forwards it to the eleven Level-1 data centers of the Worldwide LHC Computing Grid. To ensure that the triggers do not overlook important, yet seemingly normal, data, an unbiased stream of data is also submitted by the triggers. These experimental data are chosen at random and provide a check on the trigger algorithms, and ultimately, the stream accounts for only a small portion of the total data stored.

We also discussed the different layers of ATLAS, which are, from interior to exterior: the pixel detector, semiconductor tracker, transition radiation tracker, internal solenoid, electromagnetic calorimeter, hadronic calorimeter, and finally muon spectrometer. The pixel detector and trackers lie inside of a powerful solenoid magnet, allowing them to capture the curvature of particles' trajectories. The ECAL and HCAL are designed to interact strongly with certain particles (i.e. electrons and hadrons, respectively), allowing precise measurement of particle energies. Additionally, ATLAS measures missing transverse energy, which may be due to the expulsion of high energy neutrinos, but also could be an indication of weakly interacting massive particles.

After leaving ATLAS, we took a bus ride to COMPASS (the Common Muon and Proton Apparatus for Structure and Spectroscopy) near the center of the LHC ring in France. COMPASS collides protons from the SPS (Super Proton Synchrotron) with spin-aligned 6mK superfluid protons within a powerful magnetic field. Unlike the LHC experiments that collide protons head-on, COMPASS exemplifies a fixed target experiment in which high speed protons are fired at stationary hydrogen atoms.

The purpose of COMPASS is to very accurately measure the spin of the proton. Even though collisions within COMPASS are much less energetic than those within the LHC, the experiment necessitates targets of very low kinetic energy. Our guide at COMPASS explained even more about the intricacies of particle detector calorimetry and experimental design at CERN.

During our last meal in the CERN cafeteria, some of us elected to eat the "tete et langue de veau" (head and tongue of veal) while others of us ate delicious pizza, well-prepared pork cordon bleu, pasta, or turkey.

The afternoon was spent socializing and recovering from three intense days of information overload at CERN. Many of us went out for a very reasonable priced, high quality Chinese dinner near the hostel.

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[2015] Tour of LHCb, AMS, SMS-18, and CCC

2015-01-28 - We got up bright and early today (about ten minutes earlier than yesterday, so that we would actually leave at 7:45). After breakfast, we left the hostel at 7:50 (yay efficiency) and caught the train to CERN. We were met by a bus that would transport us around the CERN campus to the four sites we would visit today (the LHC-beauty experiment, Alpha Magnetic Spectrometer, Superconducting Magnet -18 test facility, and CERN Control Center).

When we arrived at the LHCb, we donned hard hats and were scanned and admitted to the experimental area deep underground.

We descended more than 100 meters into the large underground cavern that houses the LHCb and the defunct DELPHI experiment. We first went to DELPHI, a now defunct detector that has been dissected and put on display that formerly occupied the location of the LHCb detector.

At the experiment, we were actually able to touch the copper wire matrix that made up the tracker. The wires alternated between horizontal and vertical alignment, which allows for the detector software to determine the trajectory of a particle. Our guide told us about the improvements made by CMS over DELPHI's design, such as the replacement of DELPHI's copper wire tracker with silicon charge-coupled devices that provide higher resolution imaging of the particles as they curve in the magnetic field.

Depending on the scale of the experiment, particles of different charge can be separated using magnetic fields. By equating the Lorentz Force and the centripetal force, the momentum can be determined, and by analyzing the curvature of the path, the charge of the particle can be resolved.

We then moved across a thick cement radiation screen from the DELPHI exhibit to the actual site of LHCb (Large Hadron Collider-beauty experiment), which is designed to study the differences between matter and anti-matter through precise measurement of different parameters of b-meson physics.

More specifically, its goal is to shed light on why ordinary matter survived to make up our current Universe while seemingly all of the primordial anti-matter was annihilated and not symmetrically replenished. If matter and anti-matter were perfectly symmetric, we would expect to see stars formed from anti-matter among the ordinary stars of our Universe. To date, we have never found a larger anti-nucleus than antihelium, let alone anti-molecules or anti-matter stars.

686 scientists from 48 different institutes and 15 different countries around the world, along with hundreds of technicians and engineers, collaborate on the LHCb. We stood in a fenced off observational area and viewed the different parts of the LHCb, including the calorimeter system, which is designed to measure the energy of the produced particles, the tracker system, the muon tracker and the vertex locator. Unlike CMS, which must provide full azimuthal coverage to detect signatures of all kinds, the LHCb only needs to be able to measure interactions involving b-mesons. These mesons are massive enough that they stay at a very low angle relative to the plane of the LHC tunnel. This allows for the LHCb to have a pyrimidal design instead of the cylindrical design of CMS and ATLAS.

Our next location was the control facility for AMS (the Alpha Magnetic Spectrometer), a NASA-owned detector on the International Space Station. It is designed to detect anti-matter in cosmic rays and search for dark matter. We saw a model of the experiment and through it learned about the different parts of the module, including the vacuum case, tracker, calorimeter and magnet. It bore many similarities to the exhibits we viewed earlier, but unlike the LHCb and DELPHI it is entirely observational. We were guided by Dr. Vincent Smith, a member of the CMS project recently retired from Bristol University, who explained the role of cosmic rays in the ongoing search for new types of particle, such as the strangelet, a theoretically stable mix of top quarks, bottom quarks, and strange quarks that remains undiscovered as of yet.

For lunch, we ate at the CERN cafeteria, which provided awesome food, sampling from a variety of ethnicities. Overall, the meal was delicious and cheap, and we finished our lunch break with a new card game, Musta Maija, we learned from the Finns.

Our lunch ended at 1:00 p.m., just in time to make it to our belated introduction to CERN. Unlike the typical tour program for high schoolers visiting CERN, which include an introductory presentation, one site tour, and a trip to the onsite museum, we had the opprotunity to visit four different sites before we even received an introduction! We were once again graced by lecturer Dr. Vincent Smith, who gave us a very thorough overview of the origins of the organization and the different experiments going on at CERN. CERN, established in 1954, was originally called "Conseil Europeen pour la Recherche Nucleaire." When the name was changed to "Organisation Europeene pour la Recherche Nucleaire," physicists decided against changing the name to the unpronounceable "OERN." However, the original name no longer holds, because CERN is no longer a purely European organization (Israel is a member and Brazil is in the process of joining), and the focus is no longer solely on nuclear research.

After Dr. Smith's presentation, we travelled to SMS-18, where we learned about the testing and role of superconductor-containing magnets in the various experiments at CERN. The magnets must be kept below 2 Kelvin to retain their superconductive nature. If the magnet heats up too much, a quench may occur in which the coil's resistivity increases rapidly. If the quench is not controlled, the increased resistivity of the coil will cause immense amounts of heat to be emitted by the no longer superconductive magnet exacerbating the problem. Quenches are a common occurrence in the operation of the LHC, but an uncontrolled quench may cause the temperature of the magnets to rise rapidly, leading to thermal expansion and damage to the device. In 2008, an catastrophic quenching event cascaded out of control, necessitating the replacement of about fifty magnets.

Protons at the LHC are accelerated to full speed in multiple stages. First, the hydrogen atoms have their electrons striped with a powerful electric field. Then, the protons travel through a linear accelerator that uses progressively larger electromagnetic cavities to accelerate bunches of protons. Eventually, the protons enter the main LHC ring, which continues to accelerate the particles with x-ray frequency cavities. Since the protons are already at near the speed of light, the cavities are all the same size.

In addition, our guides described the theory behind superconductivity. Whereas electrons are traditionally confined to one set of quantum numbers and one location (due to the Pauli Exclusion principle), the formation of Cooper Pairs, caused by electron-phonon interactions, allow sets of pairs to "stack"Â due to their bosonic nature. From this, persistent current can be created, and large amounts of current can be sent through superconductors with no resistance.

After learning about how data is collected, we traveled to the CERN Control Centre (CCC) to learn about the inner mechanism of the collision process and how the different experiments interacted. In a presentation on another transforming window touchscreen, we learned how magnets can be employed with progressively larger radio frequency cavities to allow an amalgam of protons and particles to spread out and accelerate towards a collision detector. We were able to view parts from the different colliders and the room of people in charge of analyzing experimental data. Interestingly, they kept all celebratory champagne bottles from past successful experiments.

At the end of our time at CERN, we returned to the Hostel to work on homework, and we left an hour later for a group dinner with all the Finns at La Veranda. The group dinner included lots of good food, shared experiences, and ultimately an exchange of good-bye gifts, as three of the Finnish students are returning tomorrow to take a national Finnish Physics exam. We are now preparing for tomorrow, our final day at CERN.

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[2015] First tour of CERN