The Deep Underground Neutrino Experiment (DUNE) and why are Neutrinos so Important Anyway.

Over the past month or so I’ve published a series of posts describing what I see as the decline of science in America (28June to 12July2017). Well today I have some good news. Just this week construction has begun on the Deep Underground Neutrino Experiment or DUNE.

DUNE is a collaboration between two already existing physics labouratories. The Sanford Underground Research Facility (SURF) which is buried 2km deep in the old Homestake gold mine outside of Lead, South Dakota along with Fermilab outside of Chicago, the site of America’s most powerful particle accelerator, second only to the LHC at CERN in Europe.

By the way the Homestake mine first became a physics labouratory back in the 1960s when the first Neutrino telescope was build there to measure the flux of neutrinos coming from the Sun. An experiment that provided the first direct evidence that the Sun gets its energy from hydrogen fusion reactions.

The idea behind the DUNE experiment is that Fermilab will use its accelerator to generate an intense beam of the sub-atomic particles called Neutrinos, a particle that has been called the ghost particle because they only interact very rarely with other particles. To give you an idea of how rarely an interaction occurs, every second thousands of Neutrinos are going right through your body but over your entire lifespan only a handful will interact with a particle inside you.

That beam of Neutrinos from Fermilab will be aimed very precisely at SURF where the world’s largest Neutrino Detectors are now being installed. The 2000km trip underground will mean almost nothing to the Neutrinos; a few may be absorbed but only very a few. There will also be an identical detector array right at the output of Fermilab’s accelerator so that scientists can study what happens to the Neutrinos during their 2000km journey. The picture below shows a diagram of the planned setup of the DUNE experiment.

DUNE Experimental Layout (Credit: Fermilab)

You may ask, if only a few Neutrinos are absorbed in 2000km of rock won’t even fewer be captured by the detectors in South Dakota. Yes, absolutely, but the scientists will be able to measure precisely every characteristic of every single Neutrino that is detected.

So, what do the scientists hope to learn from DUNE, why are Neutrinos so important anyway? Well, first of all there is increasingly strong evidence that Neutrinos are actually far more numerous than the electrons and quarks that make up what we think of as matter. In a sense scientists simply don’t enjoy knowing so little about such an important particle.

There are some more well defined problems that we hope DUNE can help to solve. For one, the there’s the question why the Universe, or at least our part of it, is so dominated by matter with so little anti-matter. From all of our experiments at places like Fermilab the Universe should be composed of equal parts matter and anti-matter and Neutrinos may hold the key to understanding the imbalance.

Physicists also hope that a greater understanding of Neutrinos will give us greater insight into fundamental forces, gravity, electromagnetism and the nuclear forces. Understanding Neutrinos is also important because they play a large role in some of the most energetic events in the Universe, everything from supernova to black hole formation.

Despite the recent lack of support for science from our government it’s still true that America’s scientists are second to none and the DUNE project demonstrates how they will always find a way to do new and important work. If you’d like to read more about the DUNE experiment the links below will take you to the SURF and Fermilab WebPages for DUNE.

http://www.dunescience.org/

http://lbnf.fnal.gov/

America’s Science Decline: Part 3, Our Forgotten Atom Smashers

This is the third in a series of posts discussing what I see as the decline of Science in the United States. In part two of this series I talked about how for more than a century the United States built ever larger and larger telescopes, the largest in the World. I spoke of how those instruments made some of the most important discoveries in the history of science. I ended that post by pointing out that America no longer possessed the World’s largest telescope. I described how our largest scopes now had been built back in the 1990s and that while Europe and the rest of the World were planning to build the next generation of telescopes the United States was not.

This week I’m going to tell a very similar story about the scientific instruments that allow scientists to see the smallest objects in the Universe. I’m talking about the particle accelerators, the Atom Smashers with which we study the fundamental building blocks of creation.

The first scientist to smash one kind of particle into another was the Englishman Ernest Rutherford, who aimed the alpha particles from radioactive Uranium at a thin film of gold atoms. The scattering pattern from those alpha particles revealed the basic structure of the atom as a dense nucleus surrounded by a cloud of electrons.

Now Rutherford only aimed his alpha particles, collimated is the technical term. He couldn’t increase their energy in any way but other scientists soon began looking for techniques to do just that. Attempting to build instruments that would accelerate sub-atomic particles and use those particles to probe deeper and deeper into the atom.

The first really practical such atom smasher was the cyclotron, developed by Ernest Lawrence at the University of California at Berkeley in 1932. To understand the operation of the cyclotron, and particle accelerators in general, refer to the picture below.

Workings of a Cyclotron (Public Domain)

In a cyclotron charged particles, usually protons, are confined to move in circular orbits by a large external magnetic field. The size of the orbit is determined by the velocity / energy of the charged particle. The particles orbit inside two metal “D”s that are connected to a high voltage oscillator that gives one of the “D”s a positive voltage and the other a negative voltage with the voltages flipping back and forth at very high frequency.

The positively charged protons are repelled by the positive “D” and attracted to the negative “D”, but by the time they get to the correct side the voltage has flipped causing the protons to fly back and forth, gaining energy with each orbit. The increasing energy increases the size of the orbit until the protons reach the outer edge of the “D”s where they are extracted and fired at a target being studied.

The “D”s in Lawrence’s first instrument measured only 11 inches (28cm) across and could only accelerate the protons to an energy of 1.2MeV. (An eV is an electron volt, it stands for the amount of energy that an electron will gain as it crosses a potential of 1 Volt. an MeV is a million eVs, GeV is a billion eVs and TeV is a trillion)

In the years that followed Lawrence built progressively more powerful instruments including a 184 inch (467cm) device that was used during the development of the atomic bomb to study the separation of uranium isotopes.

In the 1950s a new design of accelerators was developed where the strength of the confining magnetic field was synchronized to the energy of the accelerated particles. These accelerators were christened synchrotrons and they continued to grow in size and energy. The Bevatron, still at UC Berkeley succeeded in producing the first the anti-protons and anti-neutrons while the Cosmotron at Brookhaven National Laboratory on Long Island discovered the Delta particle and produced the first artificial mesons. The picture below shows the Bevatron at Berkeley.

The Bevatron Particle Accelerator (Public Domain)

The rest of the world just couldn’t keep up. The US just kept building the most powerful instruments and making all the discoveries. In 1960 Brookhaven got a new 33Gev machine called the Alternating Gradient Synchrotron, which is still making important discoveries today. In 1983 a brand new facility was opened outside Chicago called Fermilab with an accelerator ring over one and a third mile (2.2km) in diameter. The instrument named the Tevatron because it not only accelerated protons to over a TeV but it also accelerated anti-protons in the opposite direction and studied the collisions between them. The discoveries made by American Atom Smashers formed the basis of what physicists call ‘The Standard Model’. In 1995 the Top quark was discovered at Fermilab, the last elementary particle to be discovered at an American facility.

At almost the same time the US congress cancelled the next great American accelerator, the Superconducting Super Collider or SSC, whose ring would have been over 17 miles (27.7km) in diameter and whose total energy would have reached 40TeV.

Instead the Europeans have taken the lead with their Large Hadron Collider (LHC) at CERN. This is the instrument that finally discovered the Higgs boson in 2013 with its 8.6 km ring (5.4miles) and energy of 13Tev. It is worth keeping in mind that America’s SSC would have been completed earlier than Europe’s LHC and still been more powerful if the politicians had not fought over a deficit that they’ve pretty much ignored since then anyway. And now even the Tevatron at Fermilab has been shut down over budget concerns.

Europe meanwhile is pressing on. There are plans under development at CERN for an even bigger, more powerful machine. Called the Future Circular Collider it will have a ring 32 km (20 miles) in diameter and a top energy of 100Tev. So therefore it will be Europe that in the next decades will lead the search for physics beyond the standard model.

In my next post I’ll conclude my discussion of how the United States is losing its once predominant position in Science.

Post Script: Even as I was writing this post the Physicists at CERN have announced the discovery of a new particle! Now this is not a new fundamental particle but rather the first composite particle with two heavy quarks. Worse yet, Fermilab had published data over ten years ago indicating the possible existence of this particle but the Tevatron was not quite powerful enough to meet the tight requirements needed to officially announce a discovery.