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    Seeing Muons!
    By Tommaso Dorigo | March 1st 2013 07:58 AM | 19 comments | Print | E-mail | Track Comments
    About Tommaso

    I am an experimental particle physicist working with the CMS experiment at CERN. In my spare time I play chess, abuse the piano, and aim my dobson...

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    My physics department in Padova is not a huge place, and yet I usually fail to be aware of what goes on around, since I spend all of my time buried inside my office. This morning, though, I had to pass by a meeting room on my way in, and I thus learned of a workshop about to start. Given my interest for the topic, I decided to attend to at least part of it.

    The workshop, titled "Mu-Steel", centered on the problem of detecting small amounts of radioactive materials concealed within large amounts of scrap metal destined to be fused in steel factories. A truck loaded with metal parts may be the perfect place to dump a radioactive source, which is a costly thing to get rid of. If the source gets melted and becomes part of the production of other objects, of course the economic damage to the factory may be very large, hence the interest of detecting these sources with effective methods.

    I have discussed the technique in another posting a couple of years ago, so I will not go into details again here. The general concept however is interesting to mention: one can use cosmic-ray muons to produce a 5-time "radiography" of a container, if the truck carrying it is made to transit and stop for a few minutes within a portal equipped with appropriate muon detector elements. The trajectory of muons -particles that interact only weakly with matter, and are thus sensitive to the nuclei of heavy elements- is deflected by their interaction with matter; by reconstructing the amount of deflection of a large number of muons, it is possible to reconstruct the image of the local density of matter within the container.

    The researchers who are developing the technique have done a great deal of progress in the recent past. They showed a full design of a portal designed to screen full tracks, a set of examples of reconstruction of muon data with the 3-D image of small lead bricks concealed in scrap iron, and the new muon detectors designed and built for the purpose. The next step is to find industries who are interested in taking the project to the building phase.

    What captured the most my attention today at the workshop was a device that organizers had placed in the meeting room. I later learned that this usually rests in a exhibit area of the department, where I have failed to notice it for a long time. It is a muon detector made with a wafer of detection elements yielding small pink sparks at the location where the muon is going through. The wafer is complemented at the top and the bottom by sheets of plastic scintillator that provide the trigger for the sparks. A picture is shown on the right.

    It is quite nice to see this thingy in operation: one typically observes a nice muon track every couple of seconds (a screenshot with one such track is on the left). One should note that muons rain from the upper atmosphere with a frequency of about 100 per square meter per second (at sea level), so the device in question -which has an effective area of about a tenth of a square meter- should see a rate of about ten muons per second; however its efficiency is kept low, but still the rate is good enough. In the 20-seconds .MOV video available here, which I took during the coffee break, you can see half a dozen tracks.

    I should also mention that if you have been to CERN for a visit, you probably have noticed a similar device, but occupying a whole wall, in the permanent exhibit of building 33. I must say, however, that all the times I went there I found it out of order -this is five or six times in the course of the last three years. I hope they put it back in operation: seeing muons is really cool!

    Comments

    rholley
    Just looked at the .MOV video.

    If one did not have the description, with those people in the background, one could imagine all sorts of science fiction scenarios!

    Robert H. Olley / Quondam Physics Department / University of Reading / England
    It's like "Primer", with a demonstration of world-bending SCIENCE to the guys with money :-)

    Hi Tommaso,

    It is interesting to see that cosmic events are happening quite naturally around us, can be made good use of. Isn't that the way though for our own nature that we are to be inventive, and to find effective ways of using that process toward one's advantage?

    This brings the idea of "relativistic Muons- http://hyperphysics.phy-astr.gsu.edu/%E2%80%8Chbase/relativ/imgrel/mu1.gif " into the playing field as a useful way with which to measure. There is some sense here then of the importance continue experiments play as an endpoint to further decay ( Proton Collision ->Decay to Muons and Muon Neutrinos ->Tau Neutrino ->tau lepton may travel some tens of microns before decaying back into neutrino and charged tracks" in order to see the results from Gran Sasso.

    Another example is measuring Magma flows in a volcano?:) The location of the muon detector on the slopes of the Vesuvius volcano for instance.( http://cdsweb.cern.ch/record/1312698/files/icon-Vesuvio_image.jpg )

    Like X-ray scans of the human body, muon radiography allows researchers to obtain an image of the internal structures of the upper levels of volcanoes. Although such an image cannot help to predict ‘when’ an eruption might occur, it can, if combined with other observations, help to foresee ‘how’ it could develop and serves as a powerful tool for the study of geological structures.

    Muons come from the interaction of cosmic rays with the Earth's atmosphere. They are able to traverse layers of rock as thick as one kilometre or more. During their trip, they are partially absorbed by the material they go through, very much like X-rays are partially absorbed by bones or other internal structures in our body. At the end of the chain, instead of the classic X-ray plate, is the so-called 'muon telescope', a special detector placed on the slopes of the volcano.See: Muons reveal the interior of volcanoes- http://cdsweb.cern.ch/journal/CERNBulletin/2010/50/News%20Articles/13126...

    s ask for some considerable relevance to what appears

    You see "collision points" ask for some considerable relevance to what appears on our backdrop measures and what conditions at time of cosmic particle collision provide for an effective way of looking at what is happening naturally all around us.

    Best,

    MikeCrow
    That was pretty cool. I wonder if it was Muon's my camera was detecting.
    Never is a long time.
    That is really great, something every physics department should own. Did you happen to learn how/where to get the instrument that is in the video? Maybe just the name of it even.

    dorigo
    Unfortunately I don't know any details. But I will ask !

    (If I don't add a message here it's because I forgot - in which case feel free to email me).

    Cheers,
    T.
    dorigo
    This instrument was constructed by the Laboratorio de Instrumentacao e Fisica Experimental de Particulas (LIP) in Portugal.

    Cheers,
    T.
    Ok, thanks Tommaso!

    I think it might have been the Coimbra mechanical workshop
    http://www.lip.pt/index.php?id=2&lg=en&projectid=33&status=0
    I can ask around eventually

    Cheers,
    Pietro

    rholley
    Just thought — one doesn’t have to wait for the muon shower to visually detect the cosmic rays.

    Since the early Gemini and Apollo missions, there has been a more direct cosmic ray detector called an astronaut.  There the detector is the retina inside an eyeball, a small scintillation chamber where Čerenkov radiation is given off as the cosmic ray particle passes through.
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    Jimmy Wales' Super Bag of Trivia on Eye Flashes:

    http://en.wikipedia.org/wiki/Health_threat_from_cosmic_rays#Central_nerv...

    A reminder of why one needs highly redundant and/or radiation-hardened computers with spare components when leaving LEO.

    dorigo
    Hi Robert,

    the light signal is tiny, and one single particle cannot be detected by the human eye, not even in complete darkness. High-energy particles and showers however may give a different outcome.

    Cheers,
    T.
    Hfarmer
    Dr. that is a very very impressive device you have there.   Was it constructed by students?  
    Science advances as much by mistakes as by plans.
    dorigo
    Hi Hontas,

    no, it was purchased, but as I said above I don't know the details, although I might find out.

    Cheers,
    T.
    Hfarmer
    Thanks.  I ask because our departments students have been building a muon counter.  It has proven harder for us than it sounded.  I have confidence they'll get it working. 
    The version you have is really really cool.  If you find out what kit it came from I'd like to build it myself. :)
    Science advances as much by mistakes as by plans.
    dorigo
    See comment above - constructed by LIP in Portugal.

    Cheers,
    T.
    Hfarmer
    Thanks :)
    Science advances as much by mistakes as by plans.
    In Padova, during the master degree, students which choose the "Esperimentazioni di fisica subnucleare I/II" course can choose among different physics experiences, one of them being setting up a muon detector similar to this but without the sparks, if I can remember correctly (basically just the scintillators and the readout electronics).

    The readout used quite standard commercial CAEN NIM modules ( stuff like this http://www.caen.it/csite/Product.jsp?Type=Product&parent=12 ), and probably the responsible for the course can gather information about where to fetch the scintillator material.

    For the apparatus built at LIP, in principle it should be largely built from raw pieces produced here, but if you contact the mechanical workshop (I posted the link above) they should give a certain answer (or point you to the builder)

    Cheers,
    Pietro

    Hfarmer
    Well I would really like to attempt to build this and reignite my universities nascent efforts to build such a detector.  
    It is being built by our society of physics students, which here is mostly an undergraduate organization.  As far as I know I am the only graduate student taking an interest in it.  I try to guide them in the right directions but have no power to say to them do this instead.   Something like this would be a really cool, really physicsy experience.  If I can sell it to them.

    I took an interest because their plans intersected with my general research interest, astrophysics, astroparticle etc.  
    Science advances as much by mistakes as by plans.