Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?
Announcements Science

NC State Creates Most Powerful Positron Beam Ever 214

eldavojohn writes "A fairly large breakthrough took place earlier this month with the most powerful man-made antimatter electron beam ever being created at North Carolina State University. Professor Hawari who worked on the project explains its benefits: 'The idea here is that if we create this intense beam of antimatter electrons — the complete opposite of the electron, basically — we can then use them in investigating and understanding the new types of materials being used in many applications.'"
This discussion has been archived. No new comments can be posted.

NC State Creates Most Powerful Positron Beam Ever

Comments Filter:
  • Re:I for one . . . (Score:2, Informative)

    by newgalactic ( 840363 ) on Monday October 22, 2007 @06:36PM (#21078463)
    btw - NC State is the Wolfpack, not Tarheel's (UNC). But they also hate Duke, so your headline still works.
  • Re:Ghostbusters!! (Score:5, Informative)

    by kebes ( 861706 ) on Monday October 22, 2007 @06:40PM (#21078491) Journal
    Electron microscopes can already image at the atomic level, but a positron microscope has advantages [aps.org] because it can give complimentary information (e.g. about the positions of atomic vacancies). You can also use positron beams for PALS (Positron Annihilation Lifetime Spectroscopy [wikipedia.org]), which is a powerful tool for determining the distribution of sizes in (nano-scale) voids in materials (difficult to measure by any other technique). It's also worth remembering that PET scans [wikipedia.org] used in medicine involves a positron-emitting chemical injected into the patient.

    There are probably a whole bunch of other experiments that positrons would be great for performing, but intense positron sources are not readily available. The development of more intense positron sources will certainly be welcomed by the scientific community, as it may allow previously unimagined types of measurements.
  • Re:I for one . . . (Score:5, Informative)

    by gregoryb ( 306233 ) on Monday October 22, 2007 @06:40PM (#21078501) Homepage
    Tarheel? Thems fightin' words, son! It's WOLFPACK...
  • by Ungrounded Lightning ( 62228 ) on Monday October 22, 2007 @06:59PM (#21078695) Journal
    So if you shot a powerful positron beam at something and also shot a powerful electron beam at it also, would you have a continuous antimatter explosion at the crossover point?

    Kinda. It's more like a gamma-ray (and neutrino) light source. The electron-positron annihilation releases a tad over a MeV mainly as two photons that fly off in opposite directions - plus a neutrino, so the photons are somewhat under half the energy each.

    Think of it as an x-ray tube - without the vacuum tube - but with the power supply, instead of being in the kilovolt range, cranked up to whatever the beam voltage is plus an extra half-million volts or so.

    Also, if you have a target you don't really need the electron beam. Just ground it well enough that it doesn't accumulate enough positive voltage to deflect the positron beam to somewhere else.
  • by Wilson_6500 ( 896824 ) on Monday October 22, 2007 @06:59PM (#21078701)
    You know, when you've read as many science fiction books as I have, this shit is a liiiitle creepy.

    Why? These are usually research reactors, from what I understand. They're not meant to power cities; they're not meant to run at a profit. They're meant to generate some types of isotopes for nuclear medicine students, and to give the nuclear engineers something to do.

    I've read a lot of science facts, and that's why this shit doesn't feel that creepy at all. I don't mean to single you out, of course, and there are plenty of valid security and OSHA-like concerns at pretty much any nuclear facility; the public's allergy to anything remotely involving the word "radiation," however, is something that could stand a lot of improvment. The dangers of nuclear science are more to do with mismanagement and a lazy operating culture--which are thankfully not fundamental physical issues but rather human ones that can potentially be fixed.

    And, frankly, I'd rather the public learn about nuclear science from scientists rather than science fiction authors.
  • by BlueParrot ( 965239 ) on Monday October 22, 2007 @07:06PM (#21078785)

    Yes, and one of the news magazine shows (20/20, 60 minutes, I forget which) had an article about the complete lack of security at these reactors. Often, the security is a grad student with next to no sleep.

    Did they also mention that these reactors have a very low power output and that you couldn't cause a meltdown even if you tried? Even for a dirty weapon the material in these reactors would be rather useless. You can find more dangerous chemicals in your local paint shop.

    Having said that, I think we should ban the nuclear family on health and safety grounds. IT'S NUCLEAR! THINK OF THE CHIDLREN!
  • by Ungrounded Lightning ( 62228 ) on Monday October 22, 2007 @07:22PM (#21078959) Journal
    How is the beam manipulated?

    Like an electron beam - with electric and/or magnetic fields. (But because the particles are positive you have to use the reverse of the fields you'd use on electrons.)

    doesn't it cause an explosion if it touches normal particles?

    It causes a spot of gamma-ray (and neutrino) "light" emission. Kinda like an x-ray tube with a half-million volts between the electrodes (minus the vacuum bottle).

    can it be used as a weapon?

    If you have a BIG truck to carry the swimming-pool reactor around. B-)

    as fuel?

    No. You'd need to trap the antimatter to use it later - and to trap any significant amount you'd have to make anti-matter neucei to counter (most of) the anti-electrons' mutual repulsion. Otherwise you'd be spending far more power holding it in than it would ever produce. That means making at LEAST anti-protons, a much more ambitious task (over 1,800 times as hard if you're just counting energy per particle).
  • by olddotter ( 638430 ) on Monday October 22, 2007 @07:25PM (#21078995) Homepage
    Currently, there are approximately 25 universities across the United States with active nuclear reactors on campus

    You know, when you've read as many science fiction books as I have, this shit is a liiiitle creepy.

    This isn't a little creepy. Idiocracy [netflix.com] is a bit creepy. Manna [marshallbrain.com] is a bit creepy. And this Wired story [wired.com]is down right scary and creepy. If we continue down this path, then we are well on our way to being a nation of idiots.
  • by TFer_Atvar ( 857303 ) on Monday October 22, 2007 @07:45PM (#21079179) Homepage
    Actually, there are 32. I wrote my senior thesis on this topic. That number is actually down from the late 1970s, when there were nearly 60. As a previous commenter said, they're virtually all research reactors, and most are of the TRIGA design designed by General Atomics. When the engineers and scientists went about designing it in the 1950s, they asked themselves how they could design a reactor that was completely accident-proof. Even if you wanted to melt down a TRIGA, you couldn't. Yanking every control rod fully out of the reactor will cause a spark in neutron activity before the water moderates the reaction back down. NC State had the first collegiate nuclear reactor in the United States, before even the TRIGA design. Rest assured, they know what they're doing.
  • by 644bd346996 ( 1012333 ) on Monday October 22, 2007 @08:05PM (#21079365)
    Note: I've been in the PULSTAR reactor room several times.

    Nuclear reactors generally pose two threats. The first is that they will get out of control. That can't happen at NC State. By the time the water gets hotter than bathwater, alarms would be going off. The reactor isn't allowed to get at all close to boiling.

    The other risk comes from the radioactive substances being stolen. Ignoring the fact that the stuff in the reactor is the least accessible stuff in the building, you would need lethal weapons and scuba gear to get significant quantities out of the reactor room. Getting the stuff off campus would be even harder.

    There is a much bigger risk of somebody raiding the chemistry labs for chemical weapons materials.
  • by Anonymous Coward on Monday October 22, 2007 @08:17PM (#21079463)
    Is that sustained or pulse power? Most research reactors can be pulsed to similar numbers for a millisecond or so before they shut themselves down.
  • Re:Obligatry (Score:3, Informative)

    by petermgreen ( 876956 ) <.plugwash. .at. .p10link.net.> on Monday October 22, 2007 @08:24PM (#21079517) Homepage
    antimatter is nasty in the sense that when it hits matter it releases lots of energy. weight for weight it would make nukes look tame.

    However antimatter does not to our knowlage occour in significant quantities naturally and it isn't feasible to make enough of it to be dangerous (we have to make it from energy and I don't think the process is very efficiant).

  • by LinearBob ( 258695 ) on Monday October 22, 2007 @10:48PM (#21080569)
    The Stanford Linear Accelerator Center, or SLAC, generates and accelerates electron and positron beams (and when needed, polarized or spin oriented beams) for colliding beam and fixed target experiments. SLAC has literally hundreds of dipole, quadrapole, and sextupole electromagnets placed along their accelerator, beam lines, and storage rings, all for focusing and directing their charged particle beams. If the center of mass of colliding electron and positron beams is high enough (at a collision energy called a "resonance") new particles will be created from the combined beam energies. During the 1990's, SLAC accelerated electrons and positrons to approximately 49 Giga Electron Volts (or GeV) each with their accelerator. After the two beams drifted in evacuated beam lines away from the accelerator, they were directed such that the electron beam and the positron beam approached an interaction point in the center of a large particle detector called SLD, from opposite sides. In the detector, the two beams would collide, creating new chargeless particles called Z-Zero or Z-Naught particles, with a collision energy of about 95.5 GeV. The Z-Zero, before it decays, is about one half as heavy as a silver atom, but quickly decays into a lot of smaller fragments, some charged and others not charged. The mass of that Z-Zero particle represents the direct conversion of the accelerator's energy into matter.

    http://www2.slac.stanford.edu/vvc/detectors/sld.html [stanford.edu]

    In the diagram shown in the link above, look for the e- and e+ labels. Those represent the electron (e-) and positron (e+) beams entering the SLD detector from opposite sides. In the center of the SLD detector is a small cylindrical piece called a Vertex Detector. The center of the vertex detector (a silicon CCD device about the size of a soft drink can with several million pixels in three concentric layers) is where SLAC's electrons actually collided with positrons. The parts of the detector around the Vertex detector are like the layers of an onion. Each layer gathers a different kind of data about the collisions that took place inside the vertex detector at the interaction point. There are a lot of very sophisticated electronics in the layers of all particle detectors, but all of the electronics have one purpose, to gather information about the decay fragments coming from the electron/positron collisions so the events that took place during and immediately after the collision can be reconstructed and analyzed with very sophisticated computers.

    Beginning in 1998, SLAC began an experiment called the asymmetric B-meson factory, or "B Factory" for short. In the B Factory, the electron beams run at a little over 9 GeV beam energy, while the positron beams run at only about 3 GeV. Both colliding beams run at very high currents, on the order of two amperes in the electron storage ring, and three amperes in the positron storage ring. The collision of these two high current beams produces millions of B mesons, each with a residual momentum (due to the asymmetric beam energies) that makes it possible for the particle physicists to study more effectively how those B mesons decayed.

    Here is a link to more information about "Storage Rings" and their electromagnets:

    http://en.wikipedia.org/wiki/Storage_ring [wikipedia.org]

    And here are links to three of SLAC's web pages, where you can learn more about colliding beam physics. BaBar is name of the particle detector used to study their decaying B Mesons, and PEP-II is the storage ring collider used to make those B Mesons.

    The PEP-II storage ring collider is at: http://www.slac.stanford.edu/grp/ad/ADPEPII/ADPEPII.html [stanford.edu]

    The BaBar detector is at: http://www-public.slac.stanford.edu/babar/ [stanford.edu]

    And SLAC's main web page (the first web page in t
  • by Anonymous Coward on Monday October 22, 2007 @11:40PM (#21080921)
    Your opinion about foreign graduate students is a bunch of crap. The reason there are so many foreign students in graduate school is because the majority of Americans don't need/want to. Foreigners are at a big disadvantage since they are foreign. It would make sense they would go to the effort to get any extra edge they can when competing for jobs. A lot of foreign graduate students would stay here in America except we kinda drive them out because they have trouble becoming legal citizens. We should be snatching these people up since they're motivated, smart and help the economy.
  • by Anonymous Coward on Tuesday October 23, 2007 @02:16AM (#21081859)
    Here's how I know that, unlike me, you aren't an NCSU NE graduate student:

    1.) The fuel rods are something you can just "remove." This action poses some purely physical difficulties- they're meters underwater, bathed in a deadly neutron flux, and have to be removed by tools taking a lot of time.
    2.) Monitors at access points would detect something being removed and sound alarms.
    3.) You don't really get to be alone with the reactor for any period of time worth mentioning.
    4.) Fuel rods aren't the attractive target people think they are.
    5.) Becoming a reactor operator and being allowed access to the PULSTAR directly involves more than just taking a few classes- security post 9/11 is much greater. Undergraduates aren't allowed to have keys to the classroom building anymore, let alone the reactor. There are things called background checks by the way.

Who goeth a-borrowing goeth a-sorrowing. -- Thomas Tusser