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More On The International Linear Collider
paragon_au writes "The UK Independent is reporting that details for a purposed 40km long international Linear Collider have been released by 'An international panel of particle physicists [that] decided the high-energy linear collider - a £3bn machine for smashing matter against antimatter - will use revolutionary superconducting technology to shed light on the origin and nature of the universe. Plans for the International Linear Collider have still to be finalised but scientists hope that construction of the underground machine will begin in six years.'"
German lab wins linear collider contest
Particle physicists have chosen to base the proposed International Linear Collider on superconducting technology developed by an international collaboration centred on the DESY lab in Germany. The superconducting approach was chosen by an international panel ahead of a rival technology developed at Stanford in the US and the KEK lab in Japan. The eagerly-awaited decision was announced at the International Conference on High Energy Physics in Beijing today.
The 30-km-long International Linear Collider (ILC) will collide electrons and positrons together at energies of at least 500 billion electron volts. Particle physicists will use the ILC to make detailed studies of the Higgs boson and any other new particles, such as supersymmetric particles, that might be discovered at the Large Hadron Collider (LHC). It is envisaged that the ILC will turn on by around the middle of the next decade, about eight years after the start up of the LHC, which is currently being built at CERN in Geneva.
Is this the answer to God, the universe and all that?
Physicists plan £3bn experiment in a 20-mile long tunnel
They call it the God particle: a mysterious sub-atomic fragment that permeates the entire universe and explains how everything is the way it is. Nobody has ever seen the God particle; some say it doesn't exist but, in the ultimate leap of faith, physicists across the world are preparing to build one of the most ambitious and expensive science experiments the world has ever seen to try to find it.
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The SSC was a circular collider, not a linear collider, so it isn't a direct replacement. ILC would study collisions between electrons and positrons. With circular colliders, one problem is that particles lose energy as they go round the ring (due to synchnotron radiation). As the energy increase these losses also increase. This is less of a problem for heavy particles (e.g. proton-antiproton) collisions, but circular colliders don't scale well for electron-positron collisions, hence the need for a linear collider.
Despite the incredible importance of this research - not to mention basic research in general - it was dismissed as a boondoggle and sandbox for particle physicists.
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The problem with an electron accelerator is that energy is lost due to the bend radius and unless you have a very large accelerator, you quickly get to the point where energy is coming out just as fast as you can put it in. Solution: an infinite-bend-radius (linear accelerator).
What I haven't seen mentioned here yet is that we use both types of accelerators (proton and electron) for different reasons. Protons colliding give the highest energies and the collisions produce a wide variety of particles and interactions at a variety of interaction energies. Electron collisions are much cleaner, but tend to be at lower energies and rates. (This is because electrons are fundamental particles but protons are made of 3 quarks each and it's really the quarks colliding.) But, if you know the energy (mass) of the particle you want to study, you can produce them reliably and in a very clean environment so you can study them more precisely.
FROM A PHYSICIST:
First Why. Natural Science is a lot like mining. Physicists discover things about nature. They attempt to put together an idea of how the fundamental works, both large and small, and create methods to predict phenomena based on these ideas. Applied Physicists and Engineers then take this knowledge and ask themselves the question "How might I use this for mankinds advantage". A simple example is the transister. The transistor could be the most powerful invention of the last century. But, without the knowledge of quantum mechanics discovered by natural physicists the transistor would never be. Natural physicists mine for the knowledge that will be later used for application. Their are countless examples of this from maxwell and wireless applicatons, certainly quantum mechanics and solid state technology, and even general relativity and GPS satellites.
Second Linear Collider vs SSC, etc: The linear collider is not a discovery machine per se. It is a precision measurement machine meant to refine knowledge about discoveries that will be made by the Large Hadron Collider which is being built in Europe. Natural physics isn't about finding a particle alone. This does nothing for us. It's about building and understanding a model of nature that can later be used to predict phenomena as accurately as possible. Neither of these machines is focused on a single particle (HIGGS, SUSY, etc.) Saying so is the equivalent of saying we're building a workbench to put together only rocking chairs. Our 'workbench' is an experiment meant to study interactions spanning the entire current model of nature. It is an expensive tool, but keep in mind once it is built it will last 20-30 years (fermilab as an example). I don't believe it's very expensice considering this keeps the flow of technology rolling.
Superconducting: The magnets proposed are revolutionary because they will be at 2 kelvin. Fermilab operates at 70+.
Yes and no. The Linear Collider doesn't depend on the discovery of the Higgs per se, but it does become more compelling if the LHC (or Fermilab) discovers _something_. The most likely scenario is that the LHC (which comes online in 2007 or so) at CERN will discover some new things - supersymmetric particles, the Higgs, the physics that gives us neutrino masses, etc. The Linear Collider would then be used to study what's been discovered. If the LHC doesn't see anything interesting (which most physicists think is unlikely, because of various arguments, but it's possible), then the Linear Collider will be a lot less useful. But there are a LOT of different ideas for what the LHC could discover - it doesn't all hinge on testing one particular model.
From the physicists' point of view, though, you don't want to wait that long. Say the LHC starts in 2007 (though such projects are often delayed) and discovers something by 2009. Then you start a proposal for the Linear Collider, which you finalize by 2012. Then you build it, and it's working in 2020. That's a LONG wait! These projects take so long that physicists want to get the ball rolling and construction started ASAP.
With an electron-positron collider, you can make these new particles singly or in pairs and use up all the energy, so they are great for doing detailed studies of the particle in question.
Actually, curves do allow electrons. It's just that an accelerating particle radiates energy (synchrotron radiation), and that radiation increases exponentially as mass decreases. The LHC uses protons because their much larger mass (~1000 greater) siginificantly decreases synchrotron radiation. The previous accelerator at CERN, the LEP, occuped the same tunnel and used electrons and positrons. However, while the LEP could only reach energies of ~200 GeV, the LHC aims for 27 TeV. A linear accelerator nips the problem of synchrotron radiation in the bud.
To follow knowledge like a sinking star, / Beyond the utmost bound of human thought. ("Ulysses", Tennyson)
There was a proposal, called TESLA for a 500GeV linear collider, combined with an X-Ray FEL at DESY. They built a far ultra-violet FEL as a technology demonstrator for this.
The recent announcement is that the accelerator technology that had also been developed for TESLA, using superconducting resonant cavities to support very high intensity microwave standing waves that actually accelerate the electrons has been chosen from among four candidates as the acclerator technology for the ILC project. That may or may not be buolt at DESY, and will not, as far as I know, incorporate an X-ray FEL.