User:JClark
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PHY 315/CEB 558 Hands-On Science with Cosmic Rays
Assignment 1 Fall 08 Jean Clark wiki page
Jean Clark is a Physics teacher at Patchogue-Medford High School and a member of LIPTA (Long Island Physics Teacher Association.) After hearing about the course from past participants and reading the course description in the LIPTA newsletter, Jean thought that it was worth a try. There are many computer savvy people in the course, and hopefully they have patience with the newbie. Learning never stops. And Jean has a lot to learn.
Another personal fact, Jean has been married for almost 25 years and has 2 sons. As one might expect, she is proud of her son who is a graduate of Binghamton University, this past May. Jean's second son just entered High School as a 9th grader. She is also proud of her youngest son, as a sailor he finished 18th overall in a National Regatta this summer. Jean's husband is a farmer and has a farm stand that sells fruits, vegies, flowers, pumpkins and Christmas trees. Although Jean tries not to work at the farm stand, it is a family business where everyone gets involved and we all eat well.
Jean does volunteer work for many organizations. Since sailing is a big thing in her son's life, she volunteers with the junior sailing program, as fleet captain, race committee, and fund raising. She also was chairman of the middle school book fair for the last 3 years, sat on the site-based team and is on the Board of Governors at her local yacht club along with serving a 2 year term as bar chair.
The first night of the course was an introduction to Cosmic rays and the detectors. The demonstration of dry ice and evaporating alcohol helped students visualize Cosmic rays. After the explanation of the setup, students conducted their first experiment. Using 3 detectors and a voltage regulator, the idea was to get the best efficiency of the coincidences of the Cosmic ray counts. The following is the recorded data and plot.
Experiment 2 Experiment 2
Week 2 of the course, Harry Stuckey demonstrated some hot keys for the wiki. Students were encourage to explore and try different ways of linking. Data was taken many times for 10,60 and 300 seconds. The assignment was to plot the 3 fold coincidences and the single detector for all the times. I had trouble scatter plotting the chart, where it overwrote onto my data in excel. I checked to see the plots of others and today I found that Kenny G had done a nice graph with the data obtained.
Plot of 3 fold coincidences vs. trials
Week 3
Error Analysis was discussed. Measurement error is an estimation of how close a measurement is from the truth. Systematic errors in the measurement technique don't improve unless identified. Random errors average to 0 so we can get improvement with repeated measurements. Error is an interval, where 68% of all measurements will fall within full width, half maximum of the bell curve. Relative error or precision is improving when the error grows. The error is better when longer measurements are taken. For counted values the error can be estimated as SQRT(N), where N is the number of counts. Errors are usually represented as bars around data points in graphs.
The experiment was to change the area and measure the rate (counts per second)for a long period of time. The error was to be smaller than the change.
1. Find Area of detector 2. Calculate the Rate = (coin 1,2,3) divided by the time 3. Calculate Error = SQRT (coin 1,2,3 / time ) 4. Plot Rate vs Area and adding in error with bars around data points 5. Find the slope = change in y / change in x
Below the link is to the data and the slope calculated to be 137.606 Hz/cm^2
Week 4 Cosmic Chris
Media:Cosmic Chris Rate 9-24.xls
When conducting future experiments, the 3,4 and 5th floor must be done over. As it is known, the higher the altitude, the more cosmic ray detection is collected.
Another suggestion would be to collect the data at different time intervals.
A third suggestion is to examine the building structure. Perhaps there are different amounts of cement. Maybe a different location would give a better fit straight line. Perhaps in the center of the building on each floor, would give different results.
10/15/08
Media:rate altitude revision.xls
10/15/08 Close Encounters with Cosmic Chris
Objective: to collect cosmic ray counts from the center of the Physics building for an extended time.
Equipment: Cosmic Chris and a stopwatch
Procedure: Our team is experimenting with rates of cosmic rays versus altitude.
Cosmic Chris is a cosmic ray detector mounted on a hand cart so it can easily roll to any location. Cosmic Chris has a Geiger counter that counts up to 999 before it turns to 0. Therefore when getting counts over a thousand, it must be kept separately as a tally.
We started with level D in the Physics building. We took measurements in two locations. The first location was between the Math / Physics building in a hallway with windows on one side and a men’s lavatory, or offices on the other side. The second location was in the middle of the Physics building between a set of fire doors.
Using a stopwatch set to 5 minutes, we would simultaneously start the counter and the stopwatch. As was mentioned previously we would have to tally each 1000 counts of the Geiger counter. The counts ranged from 8000 to 11,000.
We proceeded to levels C, B, A, Pl and S keeping the experiment consistent. We only wanted to vary the altitude and not the location within the building. As we repeated the experiment it should be noted that the Pl (Plaza) level did not have any walls, windows, lavatory or offices. We were outside with only the roof and levels above us.
Once back on the computers, we entered our counts in Excel to find the rate, the error and made a series graph of the results.
Sidenote: To Ken and Paul, I tried to email the above to you on Monday.
10/22/08
This evening the three groups made presentations on the experiments. It was interesting since the groups although acting independently, were related to each other. The solid angle group had to measure the distance between the cosmic ray detectors. The rotation group had a fixed distance as the angle of the detectors was changed in 15 degree increments. The Cosmic Chris group measured rates versus different altitudes.
The next experiment will be to keep the same altitude with different amounts of stuff surrounding Cosmic Chris. As long as the weather cooperates, we will be taking Cosmic Chris outside of the building. Keeping the altitude constant, the idea is to measure the rates at different locations around the building. Perhaps as we get closer to the building the solid angle will change and there will be less counts. As we go further from the building my hypothesis is that there will be more exposure to cosmic rays, as long as other buildings are not interferring.
Two more experiments: 1. Keep the distance perpendicular from the building, go further away 2. Keep the radius constant, as measurements are made around the building
Ken and Paul, feel free to add diagrams!
10/29/08
The Cosmic Chris experiment was conducted in the Parking Garage for 3 min on the 4 different levels. Level 1 was without walls of cement, whereas the other levels had about a 3 foot high, thick wall of cement. Also to be noted is the error is much higher than in past experiments with altitude. This experiment was taking the counts for only 3 minutes. Therefore the prediction would be for a longer period of time, the error would be lower.
Future experiments of cosmic rate vs. altitude will be on different levels of the library with a glass ceiling. Another future experiment will be to add lead above Cosmic Chris and keep him at one altitude.
11/5/08
Media:perpendicular detector orientation.xls
Media:parallel detector orientation.xls
Cosmic Chris was abandoned for the experiment. Two detectors were used at first in a parallel orientation. In order for us to have enough layers of lead block, we decided to use the two detectors in a perpendicular orientation, so as to cut down on the area measured. Also the distance was kept constant between the detectors, as layers of lead were added. The rates were for 3 and 5 minutes. In summary as more lead was layered, there were less coincidence counts. The next experiment we will use 3 detectors for a 3 fold coincidence rate.
11/12/08
Media:11-12 perp 3 fold retest 2.xls
Media:11-12 perp 3 fold pics.ppt
The experiment was using 3 detectors with a perpendicular orientation to each other. The diagrams show the 3 detectors maintained an equal spacing throughout all the experiments. The variable was the layers of lead. Starting without lead, and just the cart and steel plate gave the most coincidence rate. With each trial a layer of lead was stacked on the cart and the cart was put in place over the bottom detector.
The model is the straight line equation on the graph. A different error was calculated, chi^2. The chi^2 error is (rate - model)/ error and square the whole thing. The chi^2 error improved from 2.556 to 1.597. The best chi^2 error equals 1. The reason this model and chi^2 error was used since the error bars did not touch the line on the first graph.
The diagrams are good to explain the setup for each run for the last 2 weeks.
