CERN Control Center, Cryogenic Test Facility and some lectures....and Jazz

 

Over the last few days, I talked about lots of magnets, like dipoles, quadrapoles and sextapoles.  Here are some cross sections of those magnets on display at the Cryogenic Test Facility where we talked  about the magnets are fabricated, what technology and what material is used, and then were able to walk into a facsimile of the LHC tunnel and get an idea of how things appear in it.

 

quadrapole (used to correct the particles into a more laminar beam as they are the same charge and generally do not want to be near each other )and with two vacuum tubes

 

quadrapole (used to correct the particles into a more laminar beam as they are the same charge and generally do not want to be near each other)and with one vacuum tubes for the Phase du pantalon (bringing two beams into one near the experiments)

sextapole (used to correct for chromaticity cause when you try to focus a beam of particles with multiple momenta)

A new superconductor being introduced in the next iteration of the LHC, the HL-LHC, Niobium-Tin

The quadrapole is the red magnet in the LHC.  This one has an American flag since many of the parts came from American Partners.

Our tour guide was a PHD student named Toby and he was able to tell us all about how the superconducting wires used in the LHC greatly reduce the size of the copper wires that would needed to operate the magnets with a 19,000A current as seen in the photo below held by my colleague Phebe from Australia and Suman from India.  

That same current can be carried through this Niobium-Titanium superconducting braided wire as long at the temperature is dropped to 1.9 K just a very short way above absolute zero and almost -457 degrees F.  This means that the magnets need to be supercooled in a bath of liquid helium.  Something you may not know about helium is that new helium is not created very often on Earth, it is a byproduct of radioactive decay and is found in underground pockets, so it is very hard to get and will only get harder in the future.  This makes it extremely expensive and therefor not lightly wasted.  An attempt is made everywhere in CERN to capture and redirect the any used helium back to the reservoir to be used in cooling baths after it is properly cooled.

The magnets placed into the LHC have to be built in room temperatures, which means they have to be trained in order to make sure that it is able to work in cryogenic situations.  First they are supercooled, then they are slowly brought up to 30,000A.  Each time the temperature starts to spike, current is stopped and then the magnet cooled again and current is restarted again.   In this way they can be more sure the magnet will not heat up and blow up 100 meters underground.  This is the testing facility where the magnets are trained, the blue dipole on the back left is made using Chinese and Italian parts.

After this visit, we went to the CCC, the CERN Control Center, and saw from where all of the accelerators in CERN are run.  

After lunch we met with the director, Bettina Mikulec (the woman in pink) and she told us all about how the accelerators communicate through the CCC, whereas before they used to talk to each other and had a terrible time of keeping each other abreast of changes.  Now they use this site where they and you or I could check on the current status of any of the accelerators and get real life updates.

There are lots of bottles along the edges marking celebrations for supplied beams for discoveries made. 

A demo wire beam test.  The wire sweeps through the beam causing particles to be scattered and counted.  This can be used to check the strength and suitability of the beam before or during its trip in the LHC, or the other target areas.

We met with a senior engineer today as well named Raymond Veness.  This was a great time to just sit and listen to a guy tell an awesome story from the point of view of the engineer trying to meet the impossible specifications made by the theorists.  The physicist didn't want anything in the way of the detectors, but the beam had to stay in a vacuum and the vacuum needed to be contained in something.  The request was that they wanted the particles to travel through nothing surrounded by nothing.  So they started looking at nearly transparent atoms.  You start with hydrogen and helium but they are both gases, and lithium explodes in contact with air so they tried Beryllium.  The beryllium vacuum tube is nearly transparent since it has so few particles in the nucleus and, like all atoms, is mostly empty space, so the physicists got nearly nothing to surround their nothing.  The engineering efforts that go into this place are insane.  At the end, he left us with a request to send their enthusiasm to our students and bring the diversity to engineering.  I asked how he thought diversity helped in the engineering at CERN and he said that anecdotally he has seen that since CERN has started to equalize the hiring of men and women, the communication between all stakeholders has improved.  I think communication is bound to improve when you need to express the thoughts in your head.  Being with likeminded and similarly backgrounded people can lead to lazy communication and mistakes and shortcuts being made.

To end the night we took in a short concert in Geneva and rode in a Ferris Wheel!  It was a wonderful evening!