Using muon physics to teach relativity, radiation, and instrumentation Daniel W. Koon1 and Jeremy Ouellette Department of Physics St. Lawrence University Canton, NY, USA 1dkoon@stlawu.edu - PowerPoint PPT Presentation

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Using muon physics to teach relativity, radiation, and instrumentation Daniel W. Koon1 and Jeremy Ouellette Department of Physics St. Lawrence University Canton, NY, USA 1dkoon@stlawu.edu

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Title: Using muon physics to teach relativity, radiation, and instrumentation Daniel W. Koon1 and Jeremy Ouellette Department of Physics St. Lawrence University Canton, NY, USA 1dkoon@stlawu.edu


1
Using muon physics to teach relativity,
radiation, and instrumentationDaniel W. Koon1
and Jeremy OuelletteDepartment of PhysicsSt.
Lawrence UniversityCanton, NY,
USA1dkoon_at_stlawu.edu
  • SUMMARY
  • Muon physics provides a convenient tool for
    teaching various aspects of radiation physics and
    instrumentation in an undergraduate lab. We will
    describe how we have been using cosmic muons in a
    second-year undergraduate teaching laboratory to
    teach radiation physics and instrumentation. We
    will also describe how we recreated a classic
    muon decay experiment to test special relativity,
    using equipment available in an undergraduate
    laboratory and comparing measurements from both
    Mt. Washington (elevation 1917m) and near sea
    level. Finally, we will address the suitability
    of this test of special relativity to
    undergraduate teaching laboratories throughout
    the Americas, especially along the Cordillera de
    los Andes and in Central America, where the
    change in altitude needed can sometimes be
    obtained with a drive of a few hours or less. 
  • MOTIVATION
  • Teaching nuclear physics can be a particular
    challenge in a small undergraduate laboratory. A
    cosmic muon detection lab simplifies matters in
    the following ways
  • Muons
  • Cheap, plentiful
  • Require no handling, additional radiation safety
    procedures
  • Distinctive double-decay signature easily
    identified, even against a noisy background
  • Instrumentation
  • Scintillator Rugged radiation transducer
  • Photomultiplier Useful detector for general
    laboratory applications
  • Storage scope Simple solution for collecting
    time-domain events

EXPERIMENTS PROOF OF RELATIVISTIC TIME
DILATION IN COSMIC MUONS1 Mt. Washington
(elevation 1907m) Trial A 150 counts / 3hr
B 124 C 133 Average 136 21 (95
confidence level) Canton, NY (1770m or 6.9 ms
lower _at_ v0.9c) Trial D 61 counts / 3hr
E 61 F 52 Average 58 10 (corresponds
to 3.5 0.4 ms travel from Mt.
Washington) Measured g 2.0 0.2 Classical
result g 1 In conclusion, we have measured
the time dilation factor to definitively exclude
the classical result. COSMIC MUON
SPECTROSCOPY IN LATIN AMERICA Even larger
discrepancies between classical and relativistic
predictions are possible along the Rocky
Mountains, the Andes, and the mountains of
Central America, where one can reach great
extremes in altitude with just a few hours
drive. A large change in altitude allows for a
much more emphatic proof of relativistic time
dilation. As an example, consider Costa Rica.
Predictions of the remaining flux of cosmic muons
at sea level based on measured flux at the top of
a 3400m summit will differ by a factor of 20
(relativistic prediction larger by a factor of 20
than the classical prediction). This provides for
a conclusive test of the predictions of special
relativity. Both Irazú and sea level are within
three hours drive from San José In the Meseta
Central. REFERENCE 1. David H. Frisch
and James H. Smith, Measurement of Relativistic
Time Dilation Using m-Mesons, Am. J. Phys. 31,
342-55 (1963). FOR MORE INFORMATION http//it.st
lawu.edu/koon/
EXPERIMENTS MUON LIFE TIME, DETECTOR DEAD
TIME Mean lifetime (See Fig. 4a) Results t
2.23 0.07 msec Accepted value 2.20
msec Deadtime (See Fig. 4b) 1.3 0.2
msec Compare to Geiger-Müller tube typ. 100
msec Figure 4a The number of
muons remaining in the scintillator as a function
of time, for trials on top of Mt. Washington
(top) and in Canton, NY (bottom). Both graphs are
labeled with best-fit exponential curve
parameters. Mean lifetime is determined from this
fit. Figure 4b Mt. Washington
data of Fig. 4a, on expanded scale. Dead time is
measured from connecting a straight-line fit of
the first three data points to the exponential
curve of the rest of the data.
Fig. 2 Scintillator/detector assembly inside the
protective light-covering. SLU
apparatus Scintillator 15cm diameter x 13 cm
height plastic scintillator PMT RCA 6342A, 5cm
diameter end-on window Electronics
Differentiator, homemade, OP27GP-based 40x
inverting op amp amplifier, homemade. Oscilloscope
Tektronix TDS 210 Shielding Lead
bricks Fig. 3 Output of
storage scope Tektronix TDS 210. Trace 1 (top)
shows raw scintillator signal, triggered at the
left hand side of the screen. Trace 2 (bottom)
shows output of an ORTEC 420 Timing SCA.
Horizontal scale is 1 microsecond per division.
Bottom trace clearly shows dead time of 1.3ms.
There is an electronic delay of 1.4ms between top
and bottom traces.
Location Altitude (m) relativistiic / classical prediction
Volcán Irazú 3412 11
Meseta Central 1100 1.41
Sea level 0 201
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