TtomaszeCEB558

From MariachiWiki

Jan 29, 2008 Class #1...................Back to ... Tom Tomaszewski

Looks like we're in for some exciting times! Even though the majority of this first meeting followed the lecture mode, I found it helpful to start with many of the details. The presentation power-points will be useful in my own classroom to expose my students to this research.

Many questions arose that may or may not be answered with hands-on investigations. At least we know that we can pose any inquiry and set up a method to seek the answer.

I'm short changing my blog due to a medical detour this week. I'm scheduled for gall-bladder surgery on Thursday, Feb 7th, that will have me out of the classroom for 4 or 5 days. One of the hardest parts of teaching is planning meaningful lessons in your absence. So, my time is consumed detailing the days when I'll be absent. I will be attempting a video conference lesson before I return - I'll let you know how that goes.

Feb 5, 2008 Class #2........... Using a special Logitech pen, I can record my class notes and transfer them here. This is a summary of the class, our goals, set up, challenges and discussions:

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
The Experiment - Counter Efficiency ............ After setting up our counter array -(stacked 3 with top and bottom pre-calibrated), we varied the operating voltage to the central counter to measure the flux rates. The software was set to detect 3-fold coincidence as well as 2-fold through the top and bottom counters. The result is summarized below. We can easily note that the best operating voltage range for out test counter should be about 5.6 to 5.7 volts. At this value, the voltage can fluctuate slightly without affecting the efficiency of the counter. (Click on the image to view)

Cosmic Ray Rates ............... The following chart sequence plots Cosmic Ray Rates for fixed time periods. The logical conclusion shown by the data is that for the consistent position of the counter and the short time period overwhich the data was collected, the rate of cosmic ray remains constant. (Click to view)

Modify Configuration ....... We turned the central counter 90 degrees to the top and bottom allignment. After looking inside the guncase (not the one we were using :-)) and determining the size of the scintillator, we estimated that about 1/3 of the detector was coincident with the outside 2. Therefore we concluded that the efficiency would drop to about 35 to 40%. This is shown here:

Feb 12, 2008 Class #3........... Unfortunately I missed today's class due to surgery - I knew we were discussing the reporting of errors in our data representation. I did mention that to my surgeon ... emphasizing that my request was for him to keep his error bars as close to 0 as possible :-). After reading through Prof. Mike's powerpoint for this week, I understand that the error percentage can be minimized by increasing the number of trials and/or the length of time of data collection - I hoped that my surgeon wasn't aware of that!

I do recognize that the format of this course is optimal for those times that we have to miss class. The availability of the powerpoint that corresponds to the lecture part of class and the wiki postings of those that were present effectively keep you up to date with the lesson.

I decided to give the error calculations and error bar - excel presentation a try. I went back to my data set that collected data for different time intervals, applied the error calculations and inserted error bars on the graph. My data is .

Here is the graph showing the data collected for 10 trials of counts for 10 and 20 seconds. We only collected 7 trials of counts for 30 seconds. Interestingly, the error decreases noticeably when comparing the 10 to 20 second sets, however, not so when comparing the 20 to 30 second sets. Is this enough of a data set to show that when we went from 20 to 30 seconds and decreased the trials from 10 to 7, the error variables due to time and number of trials tend to average out?

Top is counts for 30 secs; Center for 20 secs; Bottom for 10 secs.

As an aside ... while recuperating at home after surgery I did manage to teach my AP class via video conference. It was fun, the kids really enjoyed it and we got something done!

Here are a few clips from the session:

Feb 26, 2008 Class #5...........
After missing last week's class, I was fortunate to find that Karyn and I were both in need of coming up with an investigation that we could pursue. After a brief discussion, we decided that a shower study could possibly generate meaningful data that would enable us to apply the techniques we learned in all of the classes to date.
The procedure we followed is eloquently detailed on Karen's page under 'Week 5'.
The details of the data analysis are . We look forward to presenting this to the class. Hopefully, we'll all be able to learn from a critique of our assumptions!

Mar 4, 2008 Class #6...........Presentation Week
Each group effectively summarized their project by presenting results to all of us. Having all of the Power-points posted to the WIKI will be an effective reference as we continue our research.
I would like to continue our project, initially by getting much more data elements. Incorporating the statistical analysis and error components presented by the other groups may make it easier to make sense out of the data we are seeing.

Project Summaries:
Karyn and me: Cosmic ray showers - 4-fold coincidence and separation distance.
........................Our presentation can be accessed here.
Lena, Pat and Greg: Systematic errors

Joe, Harry and Tania: Cosmic ray count rate - Flux data.

Brad, James and Vincent: Cosmic ray count rate with height - using Cosmic Chris. Information about the building structure is an important part of this analysis.

Gillian, Desiree and Mildred: Flux rate and angular dependence.

Mar 11, 2008 Session #7...........

...

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

Mar 25, 2008 Session #8...........
Karyn and I continued to collect data to improve and expand on our investigation of 4-fold coincidence and counter separation. In addition to increasing our data collection time and duplicating counts for specific separation distances we added data collection for 2-fold coincidence at each separation. This was done simultaneously and will enable a comparison of results.

Apr 1, 2008 Session #9...........
Data collection process was completed this week. Since the count rate was very low, and decreased with separation distance, we felt that getting fairly reliable results required capturing data for longer periods of time. We ended up taking trials for 10-minute intervals. In addition, we repeated each position measurement twice.
The physical configuration of our setup was similar to our initial experimental setup; that is, two 'stacks' of 2 counters each. Counts were taken and the stacks were systematically separated for subsequent trials. In addition to longer time intervals, we additionally placed counters #1 and #2 in separate stacks so that we could get counts for 2-fold coincidences and compare that with our main intent - to measure 4-fold results.

The 4-fold results are shown here. Even though a power line of best fit is shown along with an equation, I question the validity of showing this. As we suspected, the trend of the data with increasing separation does not seem to approach zero counts, but tends to be leveling off. We may be approaching the view of consistent accidental counts.


For comparison purposes the following plot includes the trend for three additional count collections. They are 1-2 coincidence counts (1 and 2 are in separate stacks), 1,2,4 and 1,2,3 coincidences where 1 counter is in one stack and the other 2 make up the other stack. As can be seen, when the stacks are close together, there is a clear separation of the data count rate. But as the separation increases, the correlation between all 4 curves is much closer. Could it be that for the quantity of data that is being collected, the accidentals are the major influence?

.................To see our presentation, click here.
How would the results change if the counters were placed on edge so that the 'stacks' are narrow and tall?


Apr 15, 2008 Session #11...........

Changing gears sightly this week, Karyn and I put aside our investigation of count rates at various separation distances and started to look at the effects of how shielding affected these rates. Our initial approach was to limit our set up to monitor just 2-fold coincidences. This was configured in a way that enabled us to place any shielding material sandwiched between counters 1 and 2.

Our first set of runs was performed to provide a base-line (control) for the experiment. We were careful to include an 'air-space' between the counters that would match the separation needed for the insertion of the shielding materials. This, of course, was to eliminate any differences that might occur due to varying the configuration - which we did not want to have.

After collecting the initial data runs it became clear that the trends were unrealistic. Without much investigation (and with Mike's help) we felt that one counter was not performing properly - either too noisy or not plateaued correctly. After replacing that counter, we continued with data collection. We took 4 sets with 4 runs within each. As can be seen in the attached data table, the 4 sets included; no shielding (control), a 1.2 cm thick steel plate, 5.0 cm thick lead bricks and lastly, both steel plate with lead bricks. Because we used a rolling cart to place the shielding in place, the cart itself was part of the shielding as well. Even though the cart material was thin, it added a small amount of shielding of its own - most likely an additional small amount of steel.

The initial results are easily conclusive - the shielding materials did just that, they blocked the transmission of particles from reaching the lower counter. It can be seen that the thicker lead bricks blocked a higher percentage of particles. It would be interesting to investigate both an increasing thickness of the same material as well as comparing equal thicknesses of different materials. (I'm pretty sure that we don't have access to enough material to continue with this idea).

A question was raised by Rich Lefferts that would be interesting to investigate. What amount of material will behave as a converter before it actually shields? A converter would actually increase the particle count by having particle interactions generate additional particles with enough energy to leave the 'shielding' material. These would most likely be electrons. Possibly a way to start looking at this and have a tie-in to our initial data collection would be to use our initial setup but keep the shielding in place between one pair of counters. Would the trends be exactly the same, but with lower counts due to the shielding? Or, will the counts change because of possible conversion? We'll see ... maybe.


Apr 22, 2008 Session #12...........
Re-visiting the above Attenuation graph with an attempt at meaningful and measurable values for the shielding thickness (suggested by Mike) lead me to the Particle Data Group website. I came across a description of Mean Free Path and Collision Length which are described as:

The Mean Free Path of a particle in a medium is a measure of its probability of undergoing interactions of a given kind. It is related to the cross-section corresponding to this type of interaction by the formula ...

The Collision Lengths given for steel (actually iron) and lead are 10.6cm and 10.2cm respectively. (reference: Rudolf K. Bock, 9 April 1998)
The graph with my attempt to include this data is here. The x-axis, representing the shielding thickness of the steel and lead is displayed as Material Thickness divided by Collision Length. For 1.2cm of steel, a value of .113 derives from 1.2cm of thickness divided by a collision length of 10.6cm.

With the full shielding (steel + lead) in place, our previous 4-fold separation experiment was repeated. The data from this setup is

and ... the graphical representation of the 4-fold data is

Apr 29, 2008 Session #13...........
Once again, with assistance, we re-plotted the attenuation with the steel and lead shielding. The attempt I made last week did not correctly represent the interactions of particles with the materials. The following two plots include material thickness and radiation lengths.

The x-axis values are determined from the density times the thickness of the materials.

The x-axis values of Radiation Length (Xo) represent the mean distance over which a high-energy electron loses all but 1/e of its energy.


May 5, 2008 Final - Presentation Week ...........
Karyn and I summarized the work and results of the past few weeks. The shared presentation can be accessed here.
One final, and significant, reflection point was to consider the value of this course. For those of us who teach, what we take from this course goes beyond our own individual learning and involves our students. Personally, obtaining a comfort level with the equipment and data collection techniques and procedures was invaluable. I gained confidence in relating this to my students so that we might take advantage of the research capabilities of the Mariachi equipment in my classroom.

Additionally, I am fortunate to have a Quarknet Cosmic Ray Detector in my classroom which can be utilized in flexible ways that are similar to the counters we used in the NSL. You can investigate the features and capabilities of this CRD and the e-Lab data tools by accessing this link.

One of the first experiments that I'd like to pursue with some students is a repeat of the 2 and 4-fold coincidence investigation that Karyn and I spent a number of weeks on. Count rates related to separation distance will be interesting to compare with the smaller Quarknet counters. Even our final experiment will be interesting to continue and expand on. A few of my students are already thinking of collecting various materials to use for shielding.

As I re-read everyone's blog, I can see that each of the experiments will be effective as student investigations. As we attempt some of these, I'm sure that many other ideas from the students will lead us in various directions - and with the foundations provided here, I'm confident that we'll all be benefiting from this type learning.

Thanks Mike and Dima!!