BASE Project DePauw University Ruizhe Ma, Mark Tolley, Professor Brooks

BASE  The Balloon Assisted Stratospheric Experiments (BASE) project is operated under the Physics and Astronomy Department at DePauw University.  Presently, the program uses helium filled weather balloons to carry scientific experiments into the stratosphere.  The communications and support system was purchased from StratoStar Systems of Upland, Indiana.

BASE – Summer 2010  Our project this summer aims to measure cosmic activities in the atmosphere by flying Geiger counters through the region of the stratosphere where these particles are produced. -Inside a Geiger counter

Cosmic Rays and Energetic Particles  Cosmic rays are continually bombarding the stratosphere and produce energetic particles  Ionizing radiation: Beta particles and Gamma rays  Geiger counters record the number of particles detected

Ionizing Radiation and Secondary Particles Reference:

Cosmic Rays and Energetic Particles  Number of particles is positively related to: - density of air molecules - intensity of cosmic rays  We expect to see the counts increase first then decrease after a critical altitude

Lead Shielding  Lead shielding is a commonly used form of protection from radiation such as beta particles and gamma rays because of its high total mass per area in the path of radiation particles.  We have adopted this form of shielding to our experiment. We expect a decrease in counts due to the lead shielding.

Equipment  Latex weather balloon  Parachute  GPS and Radio  Geiger counter  Tilt  Camera  anchored in styrofoam boxes

Geiger Counters

 attached to BASIC Stamp microprocessor  a simple 555 timer circuit processes the raw information into readable data

Geiger Counters  programmed to record the total counts for every consecutive minute or 30 seconds up to sixteen hours  shielded with different thickness of lead

Data from BASE 41 - counts per minute against time

Data from BASE 42 - counts per minute against time

Data from BASE 43 - counts per minute against time

Data from BASE 43b - counts per minute against time

Data from BASE 44 - counts per minute against time

Data from BASE 45 - counts per minute against time

Data Analysis  “M” shape  Critical altitude at the top of “M”, known as the Pfotzer maximum Burst Critical Altitude

Data from BASE 43 - counts versus altitude

Summary of Critical Altitudes Average: 67.6 ± 2.2 k feet (68% significance) 82.6% of our data are within one Standard Deviation

Crossover Altitudes FlightsAltitude (Feet) 4331k 43b32k 4439k

Data Analysis  The “showering effect” of the lead shield

Ground Tests ShieldCounts w/ Counts w/out Percentage ThicknessShielding Decreasedper mm 1.64mm %7.75% 2.69mm* %3.26% 4.77mm %3.04% 5.62mm* %2.86% 8.31mm %2.32% *Had only one run

Ground Tests Shield Counts w/Counts w/outPercentage TypeThicknessShielding Decreased Tube2.9 mm % Box2.7 mm %

Geometry of the Shower Effect

Low Energy Case High Energy Case

Geometry of the Shower Effect

Data from BASE 45 - counts per minute against time

Data from BASE 42 - counts per minute against time

Conclusions  1. The number of energetic particles increases as the altitude increases until a critical altitude beyond which the counts start to decrease. No seasonal variation has been seen.  2. A lead shield of a given thickness can only provide a protection from energetic particles of up until a particular energy. If the particles are too energetic there exists the “showering effect” which increases the number of energetic particles.

Conclusions  3. The enclosed volume and the shield thickness both affect counts. With the same shield thickness, more volume enclosed by the shield leads to more counts. With the same enclosed volume, the thicker shield leads to less counts on ground but higher counts at high altitudes.

Further Work  Try to find a quantitative relationship between counts and the enclosed volume/shield thickness  Floating valve  Hydrogen