From MariachiWiki

PHY315 / CEB558

Wiki Page of Karyn Waszmer

Week 1 (1.29.08)

On the first day of class the syllabus and the design of the course were outline. The following topics were also discussed:

• What are cosmic rays?
• Why study cosmic rays?
• The History of Cosmic Rays
• Cosmic Ray Showers
• Detection of Radiation/Particles
• Detectors
  • Cloud Chambers
  • Geiger Counter
  • Scintillator
• Software
• Demonstration of identifying coincidences

Week 2 (2.5.08)

Due to a nasty fall during a 5k race, and an even nastier one down the stairs the other night, I missed the first hour and a half of class for an orthopedic appointment. When I finally arrived to class we discussed:

• Creating Efficiency Curves in Excel
• Effects on Efficiency Experiments
  • Cosmic Ray distance to photomultiplier tube
  • Detector 2 turned at 90° with respect to Detectors 1 & 3
  • Increasing time of data collection

In order to choose a correct operation point for our detector Harry and Tom increased the voltage of the detectors in 0.1 - 0.2 V increments from 4.9 Volts to 5.9 Volts. Using the DAQ application, the detectors were set to collect data for each increment for 60 seconds. Afterwards, we imported our data into Excel and calculated the efficiency as a percentage by dividing the triple coincidence count by the double coincidence count and multiplying by 100. Our data generated the following results.

As seen in the above graph, the efficiency plateaued at 5.5 V to 5.9 V. From the graph we concluded the operating voltage to be 5.7 Volts. At this interval the efficiency was high (97.19%) and the noise count was low (418.3 Hz).

Once the operating voltage was determined, we were able to carry out some secondary experiments. We first experimented with possible ways in which the efficiency (coincidences) of our detectors could be altered. By turning the middle detector 180° to the trigger detectors, we attempted to test if the length a cosmic ray traveled in the scintillator to the photomultiplier tube would be drastic enough to decrease the number of coincidences. After a short discussion with Dima regarding the high speed of cosmic rays (~ c), and the small change in distance (~.50 m), we determined that the lag in detection time would be minimal (> 1000 ns). Thus, it would not cause a lag in detection time or a decrease in coincidence counts.

In our second experiment, we were testing the effects of the middle detector's alignment with respect to the trigger detectors on the efficiency. By turning the middle detector 90° with respect to detectors 1 & 2, we were able to cause the efficiency to decrease by approximately 2.5 times.

Lastly, we tested the effect of collection time on efficiency. We increased the collection time in 10 second increments from 10 seconds to 30 seconds. At 10s of collection the average efficiency was 95.11%, at 20 s it was 95.37%, and at 30 s it was 95.93%. Though our data displays an increase in efficiency of .041%/s, a conclusion can not be reached without a significant amount of data. Perhaps next week it could be determined if an increase in collection time yields a higher efficiency.


Week 3 (2.12.08)

I knew it would take longer to get to Stony Brook University with the snow, so I left Northport High School at 3:40 pm for class. After an hour and a half of driving, I only made it to Smithtown. At that point I knew it would take another hour and a half to get to stony brook, so I gave up and turned around.

Fortunately I was able to read the notes Professor Marx posted on the wiki. It appears that experimental efficiency was discussed this week. When discussing error in an experiment it is important to use appropriate terms to represent how close your measurements are to the actual value and how “true” your data is. Words that help clarify the validity of your measurements include accuracy, precision, random errors and systematic errors.

Accuracy (percent error) is able to be measured as a percentage. In order to determine the accuracy, the square root of counts (dN) is divided by the number of counts (N) and then multiplied by 100. In order to provide a range of the “true” measurements, it is important to include error bars.

Lastly, it was discussed that an increase in data collection time and surface area of the detectors yielded a higher count rate. Because the two variable above and vary greatly between experiments it’s important to determine a count rate per unit of time and area, which we call flux. Flux can be determined using the equation (count rate) d2 / (area of top panel) (area of bottom panel).

Week 5 (2.26.08)

Both Tom and I were not present at last week’s class, so when we arrived this past week to see every group working on an interesting study, we were both at a loss for a topic to investigate. We contemplated a few experiments off the bat, but were dejected with the lack of control variables and large possibilities of error. We were both interested by the properties of cosmic ray showers, and devised a simple experiment to hopefully determine some properties of these showers.

Once the primary cosmic ray strikes Earth’s atmosphere, secondary particles are generated at random. Considering the unpredictability of these showers, one would expect a random distribution of cosmic rays at the surface with a decreased density around the perimeter. In 2001, at the 27th International Cosmic Ray Conference, in Hamburg, Germany some scientists shared their study of simulated energy deposits as a function of distance from the shower core. Their study revealed that electron densities in e/γ-detectors decreased as distance increased from the shower core.

Knowing we were unable to reproduce a similar experiment due to lack of similar technologies, and the inability to locate a shower core, Tom and I decided to attempt an experiment which could reveal a trend in shower density with respect to area. Our big question was whether coincidences were more probable at closer distances as opposed to further distance?

Essentially, we were investigating the effect of horizontal separation distance on four-fold coincidence rates. We were both unsure of what to expect, although we hypothesized that if the horizontal separation distance increased then the four-fold coincidence rate would decrease.

Aware that this method was not definitive, we were attempting to detect two separate particles produced in the same shower by examining four-fold coincidences. We began our experiment by placing four detectors stacked two by two and side by side (.40 m). Using the tiles on the floor as markers, we moved detectors 3 and 4 by two tile (~ 1.22 meter) increments. We decided to plot the horizontal separation distance as the distance between the middle of detectors 1 and 3. In order to represent the possible separation distance accurately though, we measure the maximum separation as the distance between adjacent corners of detectors 1 and 3, and the minimum separation as the distance between the interior edges of detectors 1 and 3.

For each distance, data was collected at 3.0 minutes intervals. We performed two trials per set distance and plotted the average.

Our results are as follows:

Week 6 (3.5.08)

This week each group presented an overview of their experiment. Gillian, Desiree & Mildred kicked off the evening by presenting their results from their flux rate and angular dependence experiment. Harry, Tania and Joe presented their results on their flux data as well, in which they were able to determine the flux by increasing the distance between two counters and measuring the count rate. Tom and I presented our information on Cosmic Ray Showers regarding the relationship between four-fold coincidences and separation distance. Pat, Greg and Lena presented on Systematic errors. And lastly, James, Vinny and Brad presented their experiments dealing with cosmic Chris' ray count rate with respect to height.

Our presentation can be accessed here.

Week 7 (3.11.08)

This week we had a short discussion regarding the next step of investigations and how to more information from our counters. Dima demonstrated that the energy deposited by a cosmic ray increases the longer it is present in the counter by turning it on its side. Secondly he demonstrated an increase in time delay between a coincidence by increasing the cable length. Afterwards, the class split up into groups. Some groups remained the same as before while others branched off of and found new topics to research. Tom and I however, stayed loyal all the way and continued working together on the same topic discussed in prior posts. We spent the rest of our evening collect more data, which I will not post to the wiki since there isn't enough data to make any conclusions.

Week 8 (3.25.08)

This week Tom and I continued collecting more data for our experiment. We maintained the setup of our original experiment, except that in our upgraded investigation we decided to collected data at 10 minute intervals as opposed to our 3 minutes in our previous experiment. Through out the course of the evening we were able to collect twelve more data points in addition to our four from the previous week. Trends are beginning to appear within the data, however it is still too soon to form any conclusions until we have completed our second trial of data collection. To see our raw data, click .

Week 9 (4.1.08)

This week Tom and I focused on completing our second trial of data collection and begin analyzing the data. As the scintillators counted we convereted our distance measurements from inches to meters, organized our trials, calculated the count rate, determined the average of our two trials and calculated error for our distance measurements & count rates.
During the end of the evening, we brainstormed about the format of our presentation and possible answers to our questions. We decided to recap on the procedure & results of our previous experiment, explain our most recent experiment and provide answers to our remaining questions.

After analyzing our results the trends between count rate and distance become clear. As the separation distance between the counters increases the count rate decreases. This trend continues till about 4.0 m, at this distance and beyond the count rate then levels off as the distance increases. Tom suggests that this may be possible to consistent accidentals while I hypothesize that it may be simple coincidence in the general count rate.
The reason why the trend decreases at first may be attributed to the fact that particles tend to decay or interact more at lower sea levels due to increased air pressure. It also may be attributed to Delta Rays. The scintillators work on the concept that cosmic rays knock into atoms, causing their electrons to become excited and jumping to higher orbital. As the electron returns to its original orbital it emits a photon which is detected by the photomultiplier and converted into a current. In some cases, the electrons are knocked into with such a large amount of energy, they completely escape the atom and even the scintillator. This electron in turn can be detected by an adjacent scintillator and therefore detected as a separate particle. When the detectors are closer together, this Delta Ray phenomenon is more possible, thus causing the the four-fold coincidence to be higher.

Another trend that revealed itself during the analysis process was the fact that the coincidences between detectors 1 & 2, and also 1,2 & 3 were much higher than the 4-fold coincidences. This was puzzling to us because we had placed detectors 1 & 2 in separate stacks just as 1 & 3 were stacked separately from 2 & 4. One possible explanation could be accidental counts. We learned from Dima and from Lena, Pat and Greg's previous presentation that the accidental count rate decreases as more counters are added to the pile.

To see our presentation, click .

To see our data on 4 fold coincidences, click .

To see our data on 4,3,2 & 1 fold coincidences, click .

Week 10 (4.8.08)

Each group presented the results of their data this week. Desiree & Brad (James wasn't present) presented their data on their speed of cosmic rays experiment. Though their hard drive crashed and they lost a significant amount of data, their trends showed an average speed of approximately the speed of light (with out taking into consideration error).

Tom and I gave our presentation on the updated version of our cosmic ray shower experiment. Results of this experiment were discussed in last week's blog.

Lena, Greg, Mildred and Pat presented their experiment on cosmic ray angles. Similar to the results of Desiree, Gillian, & Mildred's results, they also detected less cosmic rays at greater angles.

Harry, Joe and Tania presented their data on cosmic ray energy deposits. It was especially interested by the fact that the two vertical set ups produced different results and reasons for this.

Lastly, Gillian presented her experiment regarding the data she collects at Smithtown High School. Her results yielded a very apparent relationship between cosmic ray counts and air pressure. Though her results could not prove which was the cause and effect, it was very evident that cosmic ray counts were higher during times of low pressure. I even used her results in my Honors Physics class today when we discussed reasons why the speed of light varies in air due to certain conditions. Thanks Gillian!

Though we got out a little late, it was a pleasure to see the interesting experiments being carried out.

Week 11 (4.15.08)

Though a few questions still remained after our last experiment, Tom and I decided to approach our study of cosmic rays from a new angle. Instead of continuing our study of cosmic ray showers, we decided to test comic rays' penetrating ability or how the cosmic rays converted as they passed through various materials.

The first stage of our experiment began by attempting to establish a control. We stacked two detectors on top of each other and placed two 2x4's of wood and two books in between like the picture to the left. The reason for this was to allow for less error later on in the experiment when we would have the detectors separated by other materials. We collected data from this setup in four trials at 5.0 minute intervals.

After completing our first set of data we then placed a very heavy piece of steel in between the two detectors. As suggested by Rich and Michael, it was best to roll a metal flat bed cart over the first detector with the steel on top, and then place the first detector upon both the cart and steel sheeting. After collecting four trials, we removed the steel and placed lead bricks upon of the cart with the first detector on top. The last set of our data taken for the evening involved placing the steel upon the cart and lead bricks, with the first detector on top.
As expected, our control setup contains the greatest number of two-fold coincidences. As the amount of substance between the two detectors increases, the number of two-fold coincidences decreases. What was unexpected was the fact that this trend is also evidence for the top detector. We had expected that the counts in the top detector remained constant and the bottom detector's counts would continue to decrease. Though the counts for the bottom detector were consistenly lower than the control for the lead bricks and combination of lead and steel, what we found even more puzzling was when the steel was placed in between the two detectors that the counts detected in the five minute interval would increase for the bottom detector(2). At first we assumed the detectors were switched with the discriminators, but when we checked they were connected properly.

Rich explain the concept of lead acting as a converter which may possibly be a reason for the increased counts. Michael also introduced the concept of high energy cosmic rays producing electron-positron pair creation and the Brehmsstahlung effect. Perhaps with more data and research, we could determine the cause of these unexpected results.

Some errors already identified include the fact that height varies slightly between the two detectors for each material placed on top. Considering that the steel was 1.2cm thick, the lead bricks for 5.0cm thick, and the combination of the two were 6.2cm thick would effect our original control which was manipulated to mimic the height of the steel-cart system.

Next week I will be down in Florida visiting family. Tom has agreed to continue taking data, in which we could hopefully find more interesting results.

Week 12 (4.22.08)

While in Florida this week, Tom combined our previous experiment involving count rates and separation distance with our new shielding experiment. As experienced in our last experiment, as the distance increases the four-fold count rate decreases. However, due to the shielding the overall trend is much lower. The results of this experiment are visible in the graph below.

Week 13 (4.29.08)

This week we did not need to collect any more data for our experiment, instead we focused on analyzing the data we had and presenting it in a reasonable manner. We decided that it was most logical to separate our experiment into two parts to minimize confusion. The first part of our experiment involved the effects of different types of shielding materials on count rate. The latter experiment tested the effects of shielding on the count rates as separation distance increase.

Our first experiment confirmed our hypothesis. As the density of the material increased, the count rate decreased. Though we formed our hypothesis regarding density, later we decided to plot radiation length and density x thickness instead.

The second experiment produced similar results to the previous experiments it mimicked, however the count rates were much lower and the leveling off of count rates as the distance increased was more drastic in my opinion.

All information regarding our experiments is available in the following power point file.
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Through out the course of the week I decided to focus on the most valuable concepts I obtained from this class. Though the breadth of my learning was very expansive, I decided to focus on the practical applications of this course that will most influence my teaching in the future.

Though this class was not required to complete my masters, I though that taking it would be most beneficial in aiding our research students who have been planning on researching cosmic rays once we finally receive our detectors. Considering this, I found that learning how to actually use the equipment was with out a doubt the most important thing I learned.
Secondly, I found it useful learning how to use and maintain a wikipage. Considering that I working on a Master's towards computer education, I found this extremely useful and entertaining.
Thirdly, certain aspects of cosmic rays that I found most interesting included learning about the different methods used to detect cosmic rays (cloud chambers, geiger counters, & scintillators), as well as learning about the particle interactions that occur in cosmic ray showers. I also enjoyed the data taking process along with understanding the causes for our results. And lastly, of all of the data presented by classmates, I particularly enjoyed the results of Gillian's experiments on the effects air pressure has on cosmic ray counts.

Week 14 (5.6.08)

This week Tom and I presented the results of our last experiment. Using the same presentation, I focused on the first part of our experiment while he focused on the latter. At the end of my presentation I highlighted my opinion of the key components to the course, which are also mentioned is last week's blog.

The rest of the class also presented a summary of their past and most recent experiments. Overall, it was great to see the many different ways in which the class utilized the same detectors to learn multiple properties about cosmic rays.

Lastly, I would like to mention thanks to Tom and Michael for their help through out the semester. Without them, I certainly wouldn't have learned as much as I did.