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Amplified frame-dragging effects due to superconductors?

  1. Dec 5, 2008 #1
    Hi there,

    This is my first post and I am guessing I should post my question here at the astrophysics section so I'm doing so (admin, if you think the topic should belong somewhere else, please move it).

    My question is with regards to the continued research conducted by Tajmar et al [1,4-7]. To answer the apparent, what seems to be an amplified effect of classical frame dragging seen near the vicinity of a rotating superconductor...

    In their initial publication [1], they attempted to use the apparent increase in the charge to mass ratio of electrons within a superconductor measured by tate et al. [2] to answer the non-classical frame dragging phenomenon (which is if I remember, >18 orders of magnitude stronger than classically predicted by GR). I coudn't understand where and how they derived many of the equations so I simply ignored their initial paper for the theoretical aspects on [1].

    The canterbury group at New Zealand is still the only group in the world to attempt replicating the effect and they concluded that the effect does not exist [3]. But they still measured an anomalous torque within the vicinity of the cryogenically cooled rotating superconductor. Tajmar et al. [4-7] continued to refine their experiment by using a similar measurement technique as Graham with a higher sensitivity setup to detect the effect and similarly measured an induced rotation and anomalous torque. They've taken into account of many environmental factors and concluded even after Graham's results that the effect is real (specifically see [7])....

    Superconductors surely have some interesting features to themselves (those obvious phenomenons, I won't explain...) such as the Tao Ball phenomenon where superconducting particles form a millimeter scale sphere under strong electric field [8].

    So the discussion that I would like to bring up is, does anybody have a thought for these phenomenon ? Does everybody think that it's simply measurement error ? I understand that condensed matter physics and theoretical understanding of high temperature superconductors are still undergoing enormous research. But I wanted to discuss the implication and significance of this effect to the understanding of the universe (if the effect is indeed real and can be verified by more than just two groups). Hmm... I hope I am asking the question I hoped to ask...

    The reference links are provided below (mostly from the arXiv site), some I couldn't find electronic reprints, just hard copy from journals.
    [2]Tate, J., Cabrera, B., Felch, S.B., Anderson, J.T., "Determination of the Cooper-
    Pair Mass in Niobium" Phys. Rev. B 42(13), 7885-7893 (1990).
    [8][8] R. Tao, X. Xu, and E. Amr, “MgB2 superconducting particles in a strong electric field”, Physica C, V398, N3-4, 78—84, 2003.

    Note: [3] was published and can be found on the Elseveir website but you must pay. So I'm just providing you the link to their group website.
  2. jcsd
  3. Dec 11, 2008 #2

    I believe Tajmar sees most weight variation during the acceleration of the disc. It would be very hard to rule out some counter-emf artifact bearing in mind that (i might be wrong here) all elements and combinations thereof have some magnetic properties and even if they don't they have electrons and other bits and pieces which may be influenced by a varying flux.
  4. Dec 11, 2008 #3
    Hi Nick, thanks for your reply. I completely agree with your opinion. Although it seems like Tajmar et al. utilized air motors to induce the rotation (I'm guessing since electric motors will influence the accelerometers reading). They also semi-abandoned using accelerometers for this reason and switched to using laser gyros.
    In their latest paper ([4] in my last post), they also considered the vaporization effect of the liquid helium that may be causing a small tilt on the structural support of the cryostat (they performed an FEA simulation using ANSYS). All seems to be below the sensitivity of the laser gyro. I've read more on their latest paper and they seemed to conclude that the effect is not due to the rotating superconductor. They conclude that the effect might be rather do to the rotating helium. It also seems like the effect is amplified as the liquid helium temperature decreases.

    Jeez... I wonder what they will measure if they encase the liquid helium in a torus encasement and spin that up with the temperatures much lower than what they've tested.... (they've went down to 4K)

    Deffinitely, can't wait for their next results :-)
  5. Dec 12, 2008 #4
    If they encased the apparatus in a 50mm thick lead box and earthed it then found a gravitational discrepancy above the lead box I think that would be convincing enough. I think I read somewhere that Podkletnov measured a gravitational variation in the room above the apparatus! I guess not verified yet.
  6. Dec 15, 2008 #5
    hey Nick, thanks for the reply again. As for your suggession on encasing the apparatus in a 50 mm thick lead, are you concerned of the vibrational issues? The laser gyro that Tajmar used was mechanically decoupled from the cryostat so they seemed to solve that issue. I've re-read their paper (yes, I actually have to read a paper at least 4-5 times to fully digest the information...) they swireled the liquid helium using a thin aluminum fin. They also filled up an aluminum cup wth liquid helium and rotated it. Both experiment yielded the anomalous signal...

    I wonder if there's been past experiment in a similar setup... I mean, rotating a liquid helium and, using a laser gyro to detect the rotation induced, and cranking down the liquid helium temperature down to micro kelvin shouldn't be a sophiticated experiment to perform...
  7. Dec 15, 2008 #6
    No - the earthed lead (Pb) casing is to shield whatever object or measuring apparatus you are using from stray electromagnetic fields which could influence the results. (I'm presuming there are induced currents present in the rotating disc)
  8. Dec 17, 2008 #7
    Ahah, I see the reason for encasing the apparatus in an lead shielding now. Tajmar et al. used an mu metal shielding around the measurement apparatus (cryostat) so the stray EM contributions were taken into account of. With their latest results, they nullified the effect due to the superconductive phase of the object. I guess we just have to wait for their next results. I hope they will perform more detailed experiments on rotating the helium. I'll update this thread once they have further updates.
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