The Cloud Chamber of Secrets The Effect of Magnetic Fields on Radioactive Particle Velocities in a Cloud Chamber

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The Cloud Chamber of SecretsThe Effect of
Magnetic Fields on Radioactive Particle
Velocities in a Cloud Chamber

• A Magical Physics Investigation by

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Dr. Roberta Gannett

• The particle tracker
• and media specialist

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Dr. Allison Nishitani

• The measuring master

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Dr. Cassie Miura

• The human compass

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What is a Cloud Chamber?

• A cloud chamber is an apparatus that tracks
  particles paths. It works by cooling isopropyl
  alcohol vapor at the bottom of the chamber with
  dry ice, while the top of the chamber is at room
  temperature so the vapor falls downward. There is
  too much vapor in the air and it is super-cooled,
  meaning that its in the vapor form at a
  temperature that is below where vapor can
  normally exist. Because it is at this cooler
  temperature, the vapor will easily condense into
  a liquid. An electrical charge ionizes the
  vapor, which leaves positively charged atoms.
  The ionized atom attracts other atoms to begin
  condensation, then you can see a trail that the
  particles leave behind them.

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How Do Make a Cloud Chamber?

• We went through several different models
  before finding one that works well. All of these
  didnt work

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This is Our Working Cloud Chamber
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Materials

• Plastic airtight chamber
• Sponge
• Black paint
• Rubber bands
• Hot glue
• Sheet metal
• RADIOACTIVE SOURCE (very dangerous)
• Isopropyl alcohol (very stinky)
• Dry ice (burns.burrrrrr)
• Cooler
• Ice pick
• Slide projector
• Digital camera

• TV
• VCR
• Dry erase marker
• Ruler
• Digital video camera with tripod
• Ice tray
• Strong magnet (neodymium)
• Hall effect probe

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How to Make the Chamber

• Cut the bottom out of the container
• Paint the metal plate black
• Secure the metal plate with putty as the new base
• Remove the clamps from the lid
• Create a very thick hot glue barrier along the
  inner top part of the chamber (not the lid)
• Cut sponge into long strips about 1 cm tall
• Glue the sponge to the glue barrier
• Put Harry Potter on top

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Laboratory Conditions

• Level surface that is resistant to cold
  temperatures
• Access to a sink and soap
• Dark room
• Constant temperature
• Room for all lab associates

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Chamber Procedure

• While wearing gloves, crush the ice and level it
  in the ice tray
• Wet the sponges with the alcohol
• Place the radioactive source in the chamber
• Place the magnet under the chamber and record its
  position
• Secure the chamber lid with rubber bands
• Place the chamber on the ice
• Turn on and adjust the light source
• Turn off other lights
• Film for 15 minutes

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Data Collection

• Find the best footage from the 3 hours of video
• Mark magnet location on TV screen
• View chosen footage on TV in slow motion
• When a curved particle track appears, pause the
  video and complete the circle with the pen
• Measure the radius and the distance to the magnet
  from the center of the circle

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Calculating the Magnetic Field

• Use the Hall Effect probe to measure the magnetic
  field produced by the magnet on the bottom of the
  chamber at intervals of .5 cm
• Find a regression formula to calculate the
  magnetic field at any distance

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Calculations

• Convert the measurements from the TV into meters
  and find the real lengths by using the proportion
  from the diameter of the chamber on the TV and
  the diameter of the real chamber
• Calculate the velocity by using vrqB/m

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Error

• The chamber
• Not airtight
• Reduced visibility due to distortion,
  reflection, condensation at the bottom
• Plastic not durable/resistant to 99.9 pure
  alcohol
• The Light source
• Spread
• Focus
• Intensity
• The Ice
• Not flat
• Not evenly exposed to the metal sheet
• Melted
• The source
• Metal base (attracted to the magnet)
• Obstructed the camera view
• The Magnet
• Position not visible through the metal sheet
• Hard to position
• Poles unknown

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Error (continued)

• Chamber Data
• The circles werent perfect because we werent
  able to use a compass
• The dry erase marker could smear or rub off
• The dry erase marker was thick
• We didnt know the exact position of the magnet
  on the TV screen
• The radius was hard to measure because it changed
  every second, so we had to guess at when we
  should pause the camera
• Magnetic Field Data
• The reading from the hall effect probe was
  constantly changing, so we had to approximate the
  readings
• The probe was large, so it was hard to take
  readings at small intervals along the chamber
• The magnet wasnt exactly where it was during the
  experiment