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Terahertz Radiation To Enable Portable Particle Accelerators ( 52

Zothecula writes with this Gizmag story about an interdisciplinary team of researchers who have built the first prototype of a miniature particle accelerator that uses terahertz radiation. "Researchers at MIT in the US and DESY (Deutsches Elektronen-Synchrotron) in Germany have developed a technology that could shrink particle accelerators by a factor of 100 or more. The basic building block of the accelerator uses high-frequency electromagnetic waves and is just 1.5 cm (0.6 in) long and 1 mm (0.04 in) thick, with this drastic size reduction potentially benefitting the fields of medicine, materials science and particle physics, among others."
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Terahertz Radiation To Enable Portable Particle Accelerators

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  • by Anonymous Coward

    Why worry? Each one of us is carrying an unlicensed nuclear accelerator on his back.
    - Dr. Venkman; Ghostbusters

  • One small step for particle accelerators, one giant step for mankind! This brings us one step closer to the replicator!
  • I wonder if this could bring ion power within our reach as a propulsion mechanism?
    • by tnk1 ( 899206 )

      We already have ion engines. They just aren't all that useful in a gravity well, but pretty efficient outside of one.

    • We have ion engines since decades, e.g. as positioning engines in satellites.
      We had a space probe using an ion engine to go to the moon and circle it.
      You must be out of the loop for quite a while.
      Welcome back!

    • The problem with ion drives is simple: F=mv and KE = 1/2mv^2.

      The force (thrust) you get from a rocket is proportional to the velocity of its exhaust, but the energy you need goes up with the square of the velocity. The limitation on ion engines is the power source, not the engines themselves.

      We are already using ion engines, though only for station-keeping (maintaining an existing orbit) or on small probes with big solar panels which can spend months or years performing orbital manoeuvres.

      • by Bengie ( 1121981 )
        Yes, if you double the exhaust velocity, you need to increase the energy by 4x assuming the same amount of exaust mass, but you gain more than 4x the acceleration due to efficiency. You have super linear gains because you conserve 100% of the increased energy, but you gain increase efficiency, allowing you to have better acceleration for the amount of energy you consume.
      • by sconeu ( 64226 )

        Someone may need to re-study his basic physics.

        F = ma, not mv.

        • He meant: F=(dm/dt)v for thrust and P=(dm/dt)v^2/2 for power. Alternatively p=mv for momentum and KE=mv^2/2. Your F=ma is not very relevant either for analyzing propulsion mechanisms.
          • by jbengt ( 874751 )

            Your F=ma is not very relevant either for analyzing propulsion mechanisms.

            Unless you want to figure the acceleration of the space vehicle you get for a given force from the engine.

  • so is this going show at 1060 west addison?

  • Charlie Stross wrote a short story, "Dechlorinating the Moderator" [] a while back about a convention of hobbyist particle physics geeks using stuff like this to produce Higgs bosons in a hotel's banqueting suite.

  • by beckett ( 27524 ) on Wednesday October 14, 2015 @05:01PM (#50729877) Homepage Journal
    see Spengler, E., Stantz, R., 1984
  • Big deal. Sony sold pocket-sized particle accelerators in the 1980s. []

  • Could this make possible a fission reacxtor design that requires a continuous input of neutrons (or protons) to keep the reaction going? To scram the reactor, just flick the Off switch instead of having to move moderator rods physically into place and then keep coolant circulating until most heat of decay is removed.

    • Technically that's still a critical reaction, just using a subcritical mass. This is sometimes called a critical assembly, esp when using neutron reflectors.

      And this device accelerates electrons. Neutrons are hard to accelerate; the only means we have of doing that are using small fusion reactions created by accelerating ionized helium isotopes into targets with more H isotopes.

      But yes, neutron acceleration can allow criticality in a much much smaller mass of fissile material, thus enabling backpack sized

    • by Rei ( 128717 )

      This is actually a thing. It's called an ADSR. They're an active research topic. The big thing that they need from their beam is POWER(TM). Designs usually call for something in the ballpark of 100MW.

      Note that such a concept isn't *entirely* failsafe. You can be guaranteed to shut down the fission, as there's no chain reaction, but you're not just going to make all of the radioactive daughter products disappear - they'll keep decaying and releasing heat even after you hit the "off" switch. On the other hand

    • The ASDRs don't add much in terms of safety. You basically have the same meltdown risk from decay heat as with a critical reactor because you are producing the same amount of fission products because you are trying to produce the same amount of power.

      There is a bit of a numbers game in trying to stay sub-critical.. You still need to play with control rods and burnable poisons etc to guarantee your reactor stays subcritical. You are aiming to get as close to critical as possible because your accelerator
  • Not so easy (Score:5, Informative)

    by joe_frisch ( 1366229 ) on Wednesday October 14, 2015 @07:48PM (#50731555)

    There have been designs for high frequency accelerators for a long time. These range from normal ~few GHz machines like SLAC, to 10s of GHz (CLIC - proposed), to THz to direct optical acceleration. There are also plasma based 2-beam accelerators which have extremely high gradients (10 GeV/M).

    There are some general trade-offs:

    Higher frequency -> more energy / length, but lower beam charge and tighter tolerances, and usually lower efficiency. Depending on the application this may or may not be a good trade, but very high frequency accelerators have so far found limited practical application. Most applications for high energy also require fairly high beam power and good beam quality.

    In particular high energy physics accelerators require very high average beam power (megawatts), which require high wall-plug efficiency, (to keep operating costs down). So far none of the high frequency accelerator designs look practical for this application. In addition for a high energy physics machine the final focus system is kilometers long, so even if the accelerators could shrink, it in no way results in a tiny machine.

    There is a lot of interest in high frequency accelerators for medical and other low energy low power applications. This is a case where there are a number of ways to solve the problem and we need to see which technology is ultimately the cheapest / easiest. Here mm-wave is competing with lasers and other types.

    For comparison, a conventional (x-band) 20MeV accelerator is 20cm long. The shielding for a 20MeV beam (which can generate neutrons) could easily be a meter of concrete.

    I'm not knocking this technology at all, it may be very useful for some applications. I just want to counter the idea that it will transform particle accelerators.

    Joe Frisch

    • by Rei ( 128717 )

      Thanks for the comment, Joe, particularly for commenting about power density and efficiency, which I had just wondered about in an above post. Concerning the distance needed for focusing, however, isn't that highly application dependent? I mean, how much does, for example, an ADSR really care about focus? A subcritical fuel assembly isn't exactly a small target, and your evaporation neutrons are going to radiate out in pretty much any direction regardless even if the high energy secondaries keep going rou

      • You are absolutely right that this depends a lot on the application. I'm from a high energy physics accelerator background so I tend to see things in those terms. Trying to ignore that bias I see as typical accelerator applications:

        1) High energy physics. This is designed for electrons so we are talking about a linear collider (look up ILC for example). Those need very high energy (TeV scale), since we've already done up to 200GeV with LEP. Very high beam powers (the cross sections are low). and very tiny

  • I've been reading articles about short accelerators for the past several decades, e.g. lasers, computer-pulsed EMF. Yet to see one to scale up to challenge existing accelerators.

"Mach was the greatest intellectual fraud in the last ten years." "What about X?" "I said `intellectual'." ;login, 9/1990