Sunday, November 11, 2012

Extreme Science

Why do we care about ultra, micro, high and fast?
Science is trying to push human knowledge a bit further every day. In science you can find people working with extreme conditions to push these limits and gain an even deeper knowledge about fundamental science. To be able to know what happens in fundamental processes, you have to push these limits. Here, I want to walk you through some of the main extreme sides of research in physics and try to explain why we care about them.

As this blog focuses mostly on nanotechnology, let’s start with that extreme. Trying to work on smaller and smaller length scales opens up a whole new dimension and possible discoveries. Why? If you want to study or manipulate single atoms or molecules, you have to work in the nano scale, which is a hundred thousand times smaller than the width of a hair.

One of the four huge detectors at CERN. In the centre
is the actual beamline (image: CERN). 
One of the most famous example of high-energy physics is the large hadron collider (LHC) established in 2008 at Cern in Geneva, Switzerland. This massive huge ring underneath the surface is accelerating protons, the positive charged particles in an atom, to energies up to 7 Teraelectronvolt. The energy is so high that two protons are accelerated in the ring to almost near the speed of light, to be precise it's 99.9999991% of the speed of light. The protons travel in opposite directions in this ring and at some point they collide. Detectors like the one in the left image are recording these collisions. Why? The purpose of the LHC is to discover new particles. Once the two protons collide, they will break into smaller particles  One specific particle, the Higgs-Boson is of special interest, as this is supposed to be the particle giving mass to all other particles.

Many experiments on single atoms are performed at low temperatures. Temperature is a measure of how fast atoms move. If the temperature of e.g. water is above 100°C it will boil, the movement of water molecules is so strong that it will become a gas. If the temperature is below 0°C, the atoms do not move that much anymore and ice is formed. The absolute zero for the temperature is -273.15°C (or 0 Kelvin, the temperature unit system used most commonly in science). At this temperature, atoms do not move any more. However, it is really difficult to reach this zero value. Most low-temperature experiments usually run at the milli Kelvin scale, which is 1000 times colder than 1 Kelvin (-272.15°C), so already pretty cold. Why? Because the atoms almost do not move anymore, you can measure them very precisely. It's like taking a picture of moving object, it's so much easier to take a sharp image of still objects. You can study quantum mechanical effects e.g. to better understand how to improve quantum computers. 

Typical UHV set-up
Ultra High Vacuum (UHV)
In my last blog, I talked about cleanrooms. An UHV system is like an even better cleanroom on smaller scale. However, you can not enter a UHV system, as there is almost no air in there, only the samples are inside. For a vacuum in the range of 10^-11 mBar, one atom has to travel for about 7000 km to collide with another particle. In practice, one atom is hitting the wall of the chamber much earlier than any other particle. It’s amazing how few atoms are in the whole system. It is also amazing to see how these UHV systems look like. Usually, you'll find a UHV system covered with a huge amount of aluminium foil and cables hanging everywhere. ;-) Why? In a UHV system, one can study atomic structures without ANY other unwanted particles. As explained before, it's like the ultimate cleanroom. 

If you want to know more about these individual techniques, subscribe to my blog. See you soon. 

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