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2003 SPS National Interns
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Anthony Visco Anthony Visco
California State University-Chico, CA

Internship: NASA Goddard Space Flight Center
Online Journal
Week of July 25, 2006 Week of July 4, 2006 Week of June 13, 2006
Week of July 18, 2006 Week of June 27, 2006  
Week of July 11, 2006 Week of June 20, 2006  
Date: July 25, 2003
Week Seven

This week was spent developing the support structure and sample shield for the X-ray fluorescence unit. It has been a great learning experience in engineering and design. It takes teamwork and coordination to complete this kind of project. I have had to call around to find the cost of materials, machine shops construction times and fees, etc.

The X-ray fluorescence system is basically an X-ray tube, a sample shield and sample holder, and an X-ray detector. The sample is placed in the shield and holder to be irradiated. The X-ray tube fits into one end and the detector sits at the other. The majority of the radiation is emitted into the shield which must absorb enough to protect the user for X-rays. One of my first tasks on the project was to calculate the thickness of the shield required to be within regulations. Since some of the X-rays come out of the back end of the tube, an additional environmental shield was designed to absorb this excess radiation. The design for the environmental shield has been completed leaving only the sample shield and support structure.

I decided to have the support structure and the shield integrated into one unit. The unit is free-standing in the outer environmental shield. I expect to have the support and shield finished by next week.

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Date: July 18, 2003

Week Six/Mid-term Presentations

This week I divided my time between preparing for my presentation and designing the environmental shield for the X-ray fluorescence system. The original concept was to use lead lining in a plywood box, but due to the dangers of using lead and the weight, we have opted for a lead-infused plastic. This has been very challenging for me since I am not trained in product design. I've had many concepts and after discussion with my mentor, these concepts have evolved in such a way that the original idea is barely recognizable.

I also realized that the time scales that I had in mind are not realistic since we must contract people for the actual construction of the environmental shield. Something as simple as constructing the box will take from two to four weeks. The power supply could take as long as eight weeks. I've been pushing to get as much done as possible in these remaining weeks. I am starting to recognize that I probably will not see the finished product.

The presentations went extremely well. I think all the mentors were impressed with the job we did. It was interesting to see how everyone else's projects were coming along. It was especially interesting to see how inter-related my project was with Jeff's and Justin's. At the end of the presentations, my mentor Jack Trombka and Dr. Eric Vogel from NIST got into a lengthy discussion about joining their efforts.

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Date: July 11, 2003

Week Five

This week I spent more time on the forensics project, and I have worked out most of the required shielding thicknesses. We had a meeting this Friday with the Center for Technology Commercialization who is working with us on the project. It was interesting to see the dynamics between the two sides of the project. NASA represents the scientific side and CTC represents the business side. I got an insight to how the projects go from paper to product, and the importance of organizing the project so that the objectives, dates of completion, costs, etc. are clear to all involved. It is truly a group effort, and many different stages will be done by a variety of different groups.

At the meeting more responsibility for the project was delegated to me, as my crew at NASA has been extremely busy with other projects and proposals. We hope to have a working model ready for testing by the end of my internship.

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Date: July 4, 2003

Week Four

This week I started a new project. We are working with the Justice Department to use the considerable technology of spectroscopy to aid in forensics. By using characteristic spectral lines and their relative intensities, blood, semen and gunpowder can be shown to be in certain samples taken from the scene of the crime. We are trying to develop a handheld unit that is capable of analysis at the scene of the crime. Though the elements that make up the characteristic lines of gunpowder, for example, occur naturally, the relative intensity of the lines can determine if they came from a gun and who the shooter was. If the analysis can be done on the scene, a suspect can be held for probable cause while more detailed analysis is conducted at the lab.

We are using X-rays up to 70 KeV. The sample is bombarded with X-rays, and a detector is used to collect the reflected photons. The detector then gives a reading of the pulse height spectrum from which the peaks are separated from the background noise. It is the peaks that represent the characteristic lines. To protect the operator from the X-rays, the whole apparatus must be inserted into a metal shield.

It is my job to calculate the attenuation of X-rays in different tungsten alloys to determine the thickness of the shield. We hope to have a working model soon and run tests in the lab to determine, amongst other things, if the operator will have acceptable dosages of X-rays due to the apparatus. On Tuesday, we'll have a conference with the engineers to discuss the design.

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Date: June 27, 2003

Week Three

This week I finished up cataloging the spallation products created in cadmium zinc telluride detectors due to interactions with high energy protons. I also made many graphs representing the pulsite spectra any one of these decaying radioactive nuclei would produce. I created a package for Dr. Trombka, and he will be presenting it as a reference at his presentation in Brookhaven.

Upon the completion of my project, I took a radiation safety course which will allow me to work in the laboratory with radioactive materials. One of my lab projects next week may involve calibrating some radiation detectors. I'm looking forward to getting some hands-on experience in the laboratory.

This week we held a celebration at Goddard called "Goddard Day." There were many booths from the different departments and clubs that have formed at NASA. The clubs covered such topics as amateur radio, scuba diving and small aircraft piloting. Many of the booths were giving away free things, and I collected bags full of goodies and posters. There was live music, and each department presented a group for karaoke with lyrics changed to fit the group's activities. Clearly, science is their forte.

This Friday, we met with the computer scientists and discussed computer simulations to see if we could produce the pulsite spectra due to scattering of cosmic rays from the surface of Mars. As a first simple model, the planet Mars will be represented as an infinite plane with many rectangular "bumps" of varying heights and areas placed upon it to represent rocks and other formations. Using a Monte Carlo simulation, we will try to determine the composition of the Martian surface by analyzing the pulsite spectrum. This was very interesting to me and gave me ideas of possible study in graduate school. It is exciting to see those at the forefront of the field pushing science further. It inspired me and strengthened my desire to contribute, though I realized how far off I am when I presented some of my "unique" approaches to Dr. Trombka and found I was trying to reinvent the wheel.

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Date: June 20, 2003

Week Two

This week I catalogued the spallation products due to high energy proton interaction with cadmium telluride zinc detectors. The products of these interactions are radioactive and hence when they decay to lower energies, they emit photons. This induced activity forms part of the background noise in pulse height spectra. We are hoping that from this information we can program the detector to ignore voltages that are due to these frequencies of radiation. I thought the task would take 15 minutes, but after 8 hours on my first day, I had come up with nothing.

On the second day, somewhat frustrated, I asked the head librarian at the NASA library for help. After 15 minutes, he was unable to come up with anything. I went back to my research, but after several hours, he returned. I was amazed to find that he had been trying to find this information for me the whole time. It was the information he provided that led to my eventual success. The information was only in recent journals, and the search engines I had been using did not include these journals. I learned my first valuable lesson in research: Make friends with the librarians.

Once we found the spallation products, I was asked to find what particles were emitted during the decay of the radioactive nuclei and their respective energies. The emitted particles were mostly positrons and Beta particles. Dr. Floyd directed me to a table of isotopes where I could find the respective energies, though it took almost 2 hours for me to learn to interpret the table.

Next week, I will look into what isotopes of cadmium zinc telluride whose decay would produce these radioactive nuclei.

This Friday, I was privileged to sit in on a meeting discussing the geology of Mars presented by Dr. Tim McCoy. Dr. McCoy is the curator of the Meteor Collection at the Smithsonian. I introduced him to Gary White, and the two discussed a possible behind-the-scenes tour at the Smithsonian. Though much of the meeting was technical and somewhat over my head, I learned much about the political process of physics. Unlike theoretical physics, in research, funding is an issue. Therefore, the research must be useful to other physicists as opposed to solely satisfying the interests of the theoretician. Research is a team effort, and the funding must reflect this.

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Date: June 13, 2003

First Week

I'm finally getting settled in at NASA Goddard. The first week consisted solely of researching on radiation detectors to get me up to speed. The project we are working on involves cadmium zinc telluride detectors which are used for spectroscopy. It's been like finals week for me with my nose buried in one textbook or another. I'm working under Dr. Trombka and Dr. Floyd. Both are in the forefront of extraterrestrial spectroscopy as is evident by their names on all the books and papers I've been reading. I get daily personal lectures from these distinguished physicists, and I'm getting paid to do it. I've heard the two of them get into heated discussions. The excitement of the field is contagious!

Next week, I will be studying induced activity in the cadmium zinc telluride detectors. We are trying to find the different species created by interaction with cosmic rays in order to see if we can reduce the background noise from our pulse height spectra. By doing so, we will come to a clearer understanding of a frequency band of cosmic radiation that has eluded physicists to date.

On a different note, we have been experiencing severe storm conditions in D.C. It rained so hard that water started coming into the bus, and one of the Metro lines was shut down between two of the stations. I personally like the rain because it brings the temperatures down, though the bus driver told me this weather is uncommon for this time of year.

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