Nine Orders of Magnitude in Two Days

This post documents a journey through nine orders of magnitude in energy, undertaken on a weekend in late September 2016. Starting at the highest energies currently available in the laboratory (TeV), we went down to fission (MeV), fusion plasma energies (keV) and finally back up again to GeV.

Although the picture-to-word-ration here likely exceeds unity, I hope you still find it entertaining!

CMS hall, in the middle of nowhere near Cessy, France. The lower building to the right houses the control room and High-Level-Trigger computer infrastructure.

We are right here!

Control room. Since the LHC (and thus all of the detectors) were switched off the week we visited, not much was going on.

Switched off indeed — good for us!

Salient feature of CMS is their huge solenoid: 6m inner bore, up to 4T. Stored energy is > 2GJ. You don’t want to extract this instantly!

Detector safety swichboard. Manual magnet dump, fire system trigger and the like.

Control room.

Entry door to the cavern. We didn’t use this one, but went through the MAD (material access door).

In the USC (Underground Service Cavern), which houses the low-level electronics and the Level-1 trigger.

Electronics racks everywhere…

The main theme of my Bachelor’s thesis: the global trigger FPGA (Virtex 7) of the Level-1 trigger system…

… brought to you by the Austrian Academy of Sciences!

Here it is, the CMS detector! Visible is only the iron return yoke, interleaved with muon chambers that make up the outer layers of the device.

Access shaft on top.

Beam pipe coming in from the right. The massive looking steel is shielding, to protect collision debris from going astray in the downstream magnets.

TOTEM is an auxiliary detector at Point 5, focusing on _elastic_ (thus small-angle) scattering of protons.

Power supply might be a little oversized here…

Looking back to the surface.

Cryo plant for the solenoid.

These Sr-sources are used to calibrate the calorimeter: they can be run through pipes traversing the detector, thus allowing to monitor the energy response.

In case of a magnet quench, the current (some 18kA) will divert here.

Cryo plant cooling towers and helium storage.

Guess what this is?

Change of place and a step down from TeV to MeV: this is the CROCUS zero-power reactor at the EPF in Lausanne. Used for teaching and training.

This is the reactor pool. Since the fuel was removed when we visited, the residual radiation was barely noticable (0.6uSv/h).

Reactor period = infty!

Just next door, in the Swiss Plasma Center at EPFL, the TCV (Tokamak a configuration variable) is operated. (The device is right behind the back wall, the toy penguin hanging from the ceiling holds a permanent magnet and hence moves during a shot!)

Thomson scattering data from an earlier shot.

We sneeked in during two plasma shots.

The neutral beam injection, used as a plasma diagnostic.

It’s bigger cousin: the neutral beam heating. As might be evident from the picture, not currently operative (it was installed during summer 2015).

Gyrotron gallery. A nice feature of TCV is its oversized heating system that has ample spare power to also operate under exotic conditions.

TCV from above.

Back in Geneva and back to the GeV energy scale. This is right above the PSB (Proton Synchrotron Booster), which accelerates protons to 1.4GeV. Specifically, this is the section where transverse feedback (TFB) is applied to the beams.

RF cabinet: locked, since the ring was operating and delivering beams to the upstream accelerators.

Inside the RF cabinet.

Electric schematic of the main magnet power supplies.

You might notice that all equipment is present four times: indeed, the PSB consists of 4 identical beam pipes, stacked on top of each other!

Thyratrons that power the kicker magnets, used to inject and eject the beams.

This magnet is identical to the ones used in accelerator, and wired in series with those. It contains excessive monitoring of current, B-field profile etc., which are used for feedback control.

A passage through maintenance tunnels and…

… another step down and back to MeV: electronic galley above the LINAC, the first machine in CERN’s complex.

The proton source is at the very left, followed by a radiofrequency quadrupole (copper) as first accelerating structure.

Then comes the LINAC, giving the protons an energy of 50MeV.