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Protocollo Acquisizione ed Analisi delle Tracce

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Protocollo Acquisizione ed Analisi delle Tracce Powered By Docstoc
					              RSS Radon - CR39
             Acquisition & analysis
                 of the tracks




dr. Massimo Vascotto
NOTE ABOUT THE PROJECT


• The aim of this project, only for educational purposes, is to
  propose an itinerary of study on the natural radioactivity,
  allowing students to measure the radon in their homes,
  following the same protocols of a real scientific research.
• Participation at the measure is voluntary, not mandatory.
• Participation in the project includes the compilation of a
  questionnaire that will be only used for the purposes related to
  the survey. Participants are responsible for the information
  provided in the questionnaire.
• Personal data, the information contained in the questionnaire
  and data related to the measure will be kept with any safety
  standards, in the archives and/or reporting of entities involved
  in the project, under the privacy laws.


                              Ma. 09/03
EQUIPMENT AND MATERIALS



• Microscope: Konus Academy
  1000x (Mod. 5304) 40x;
• Micro camera: Konus CMOS
  Camera USB PLUG (Mod. 5829)
  [~10x];
• Software: Konus Minisee
  (provided with micro camera);
• Resolution: 640x480pixel;
• Image dimensions: l=0,361mm
  h=0,263mm;
• Image surface: s=lxh=0,095mmq.

                         Ma. 09/03
IMAGE ACQUISITION
1. Switch the microscope “on” (pos. 2);
2. The micro camera is in working condition when the USB
   is inserted on the computer;
3. Click 2x on “Minisee” software, previously installed on
   your PC;
4. Click on file/import image/select device (select the driver
   as instructions);
5. Click on “acquire” icon [or follow the path: file/import
   image/acquire];
6. Select resolution (preference/resolution) on 640x480 (NB:
   microscope is on);
7. Insert a slide filled with CR39 on the microscope (note: ID
   number, is readable);
8. Try to focus the image. If possible, start from the serial
   number of CR39, if there is, or something visible, like a
   corner of CR39 (use focus and fine focus);
IMAGE ACQUISITION
9. Consider that light deformations like arching or saddling
    of the slide, may alter the focus, when you move it (note
    that you are working at 40x!).
    In that case is indispensable to re-focusing the image
    every time it is necessary (focus and fine focus);
10. Move the slide randomly. It is suggested to do this
    operation avoiding to look on the screen of the PC (this
    is due to the fact that human eye always try to search for
    something...). So, it is better to work in two people. One
    check the microscope, moves the slide and decide when
    to stop, and the other work on the monitor and on the
    software commands. Finally, both work on focusing;
11. Focus the image as best as you can (fine focus). Note
    that you have often some references to do this, like
    tracks, impurities, serial number, etc.;
12. Take the photo by clicking once on "SNAP SHOT";
 IMAGE ACQUISITION
13.Move the slide randomly and repeat the previous steps
   until you have collected at least ten images;
14.The images are saved per default on desktop and are
   numbered progressively (from minisee0000);
15.Remember to always create a folder named as the CR39
   analyzed, and then drag the collected images in;
16.Repeat the image acquisition for the next CR39, until you
   finish your working session;
17.Close the acquisition window by clicking on "exit";
18.Close the “Minisee” software. It is suggested to always
   have a backup copy of all the acquisitions;
19.Now you may count the tracks on your pictures and
   determine the radon concentration by means of the file
   “RSS Rn measurements CR-39.xls”.
   You may download this file at the link:
   http://physics.units.it/didattica03/orientamento/laboratori.php.
SOME INFORMATION ABOUT TRACKS
• Tracks generated by alpha particles on CR39 surface
  have dimensions of nanometers (nm) and so, to keep
  them visible at microscope, you must etch them with
  caustic soda (NaOH).
• By means of chemical etching you may widen the holes
  leaved by alpha particle up to tenth of micrometers (mm),
  so they become visible at microscope.
• For further information about etching see “CR39 EN.ppt”.
  You may download this file at the link:
  http://physics.units.it/didattica03/orientamento/laboratori.php;
• It is important now to point out something about the track
  geometry.
  This aspect is very important if you consider that you
  must be able to select “good tracks” from bad or poor
  ones, as this may affect your results (i.e. influence the
  final radon concentration).
SOME INFORMATION ABOUT THE TRACKS
• This aspect is correlated to different parameters, like:
   • the incidence angle of alpha particles;
   • the energy of alpha particles;
   •The range of alpha particles;
   • the length of chemical etching;
   • ...
• Normally the alpha particle may have any incidence
  angle when hits the CR39 surface. So, in most cases the
  hole leaved will be elliptical. The track will be circular
  only if the incidence angle will be perpendicular or
  nearly perpendicular to CR39 surface.
• Hole shape is also connected to the length of the
  chemical etching. For example, a short etching time will
  not allow to all holes to grow up and become visible.
                           Ma. 09/03
SOME INFORMATION ABOUT THE TRACKS
• A good timing etching will allow you to well distinguish
  the different kind of shape of the tracks and to improve
  the tracks counting.
• A long etching will
  produce in the
  transformation of all the
  elliptical holes in
  circular holes, as a
  consequence of the
  prolonged attach of
  caustic soda, like in
  figure.
• An super etching may
  determine the vanishing
  of almost (or all) the
                            Ma. 09/03
  tracks.
SOME INFORMATION ABOUT THE TRACKS
• Another aspect to be considered is the alpha particle
  range and energy. It is known that alpha particle range in
  air is around 10cm. In our case alpha particles, inside the
  exposure chamber, may range between 0 to 5cm.
• As alpha particle loose energy in inverse proportional rule
  to the range, the damage produced by alpha particle on
  CR39 will be consequent.
• All these considerations help us to understand that it is
  possible to have thousands of situations in shape and
  dimensions of the tracks and that counting them is not
  always so easy.
• Anyway, if we consider that the tracks will occupy some
  surface this, possibly, will be an aspect that we may take
  in account to decide if consider a track or not. Note that
  this is also the criteria adopted by the automated optical
  track reader, used by environmental protection agencies.
SOME INFORMATION ABOUT THE TRACKS
• Obviously this may introduce some errors as it is possible
  to count “as real tracks” something like impurities,
  scratches, chemical residual, etc.
• The eye approach is quite different, as it is able to discern
  between tracks and impurities.
• On contrary, eyes cannot work for a long time, especially if
  the number of observations is high. This may also
  introduce some errors, in counting phase.
• It is important to train, before start a real measure.
• It is important to set up a
  “boundary” in track dimensions
  to quickly conclude if a track is
  good or not.
• Anyway, good tracks are always
  “well shaped”. It doesn’t matter if
  they are circulars or elliptic.
SOME INFORMATION ABOUT THE TRACKS
• Moreover: we always must remember that we calculate
  radon concentration by means of pictures.
• The surface analyzed in a picture is less than dimensions
  of a CR39.
• So, possibly, this may
  represent a “poor
  statistic”, especially if
  compared to that of an
  optical reader, that is able
  to measure all the CR39
  surface (in less time), apart
  of the fact that it counts
  some false track.
• Usually this will be a real problem when Rn concentration
  is low. In this case is better to increase the number of
  acquisitions (more pictures).
TIME OF ACQUISITION OF TRACKS
• Remember to always focusing, the images before take the
  picture (fine focus).
• As said before this is due to the light imperfections on the
  slide shaping or on its thickness, that are inevitably
  amplified by the microscope (as we work at 400x). The
  consequence is that you have a change of the focus
  (sometimes you go inside or outside of the CR39 surface).
• Timing: you need between 3 to 5 minutes to acquire a set
  of images (about 20 to 30 seconds per image). Obviously
  you need some training. The timing depends also on the
  ability, the tiredness and on the accuracy of the operator
  and may be affected by several inconveniences.
• Then you must add the time to create the folder named as
  the ID of the CR39 (around 20 to 30 seconds) and to drag
  inside the images.
• Never consider this as a “time race”, but try reach the
  better result as you can.
A BRIEF TRAIN COURSE FOR READ THE TRACKS
• In the following slides we show some examples of
  pictures, in which we may see:
    • Good tracks;
    • Bad tracks (that’s to say tracks that we not consider
      for many causes. For example simply because they
      are too much small);
    • Impurities;
    • Faults;
    • Scratches;
    • Chemical residuals;
    • Other substances;
    • Bad etching tracks;
    •…
• Finally we show some pictures of the same subject, in
  different focusing conditions.
• Note: all the images are from school works.
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
SOME EXAMPLES OF TRACKS




                 Ma. 09/03
IMPURITIES, FAULT, AND SCRATCHES




                   Ma. 09/03
IMPURITIES, FAULT AND SCRATCHES




                   Ma. 09/03
IMPURITIES, FAULT AND SCRATCHES




                   Ma. 09/03
IMPURITIES, FAULT AND SCRATCHES




                   Ma. 09/03
IMPURITIES, FAULT AND SCRATCHES




                   Ma. 09/03
IMPURITIES, FAULT AND SCRATCHES




                   Ma. 09/03
IMPURITIES, FAULT AND SCRATCHES




                   Ma. 09/03
IMPURITIES, FAULT AND SCRATCHES




                   Ma. 09/03
IMPURITIES, FAULT AND SCRATCHES




                   Ma. 09/03
IMPURITIES, FAULT AND SCRATCHES




                   Ma. 09/03
EXAMPLES
      YES



            YES




                  Ma. 09/03
EXAMPLES




                                         YES



               BORDER OF A SERIAL ID OF CR39




           Ma. 09/03
EXAMPLES



      IMPURITY



                                       IMPURITY



            YES




                                  IMPURITY




                       IMPURITY
                  Ma. 09/03
EXAMPLES




                       YES




           Ma. 09/03
EXAMPLES
             YES




           YES

                   YES

                                 YES

            YES

                                  YES

     YES




                                  YES


                     Ma. 09/03
EXAMPLES




                       IMPURITIES



           YES




           Ma. 09/03
EXAMPLES


    IMPURITY




      YES




               Ma. 09/03
EXAMPLES




                                  IMPURITY




                      YES



           IMPURITY
                      Ma. 09/03
EXAMPLES




           IMPURITY




   YES




                      Ma. 09/03
EXAMPLES



              YES
        YES

                                      YES




                           IMPURITY
CHEMICAL
RESIDUALS




                    Ma. 09/03
ANOMALOUS ETCHING




                    Ma. 09/03
ANOMALOUS ETCHING




                    Ma. 09/03
ANOMALOUS ETCHING




                    Ma. 09/03
MICROSCOPE: 4x




                 Ma. 09/03
MICROSCOPE: 10x




                  Ma. 09/03
MICROSCOPE: 40x




                  Ma. 09/03
MICROSCOPE: 100x (badly focused)




                     Ma. 09/03
MICROSCOPE: USING FINE FOCUS




• The following slides show the same image at 40x just
  modifying the fine focus (consider that you have also a
  10x from micro camera, so it is a 400x enlargement),.
• We show the same hole focusing:
       • over the surface of CR39 (over the track);
       • at the surface of CR39;
       • inside the CR39 (…inside the track);




                           Ma. 09/03
MICROSCOPIO: OVER




                    Ma. 09/03
MICROSCOPIO: AT THE SURFACE




                  Ma. 09/03
MICROSCOPE: INSIDE




                     Ma. 09/03
MICROSCOPE & CALIBRATION SLIDE

 • In the following figure are shown the calibration slides
   used to determine the dimension of our images at
   microscope (remember we have a 40x from microscope,
   10x from micro camera, with a resolution of 640x480).




                           Ma. 09/03
FURTHER INFORMATIONS




 • For further information, please e-mail me at:

               massimo.vascotto@ts.infn.it




                           Ma. 09/03
Some references

• http://physics.units.it/didattica03/orientamento/l
  aboratori.php
• http://web.ct.infn.it/laborad/
• http://www.fgmambiente.it
• http://www.radosys.com/
• http://www.tdx.cesca.es/TESIS_UAB/AVAILABL
  E/TDX-0125103-094545//ka4de9.pdf




                       Ma. 09/03

				
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