My Life as a Guest Scientist at Fermilab

Tim Brennan, Academic Year 2000-2001

Outline

I. The Fermilab Site

II. The BTeV Experiment

a. Big Pictureb. Little Picture (my experimental work)

III. The Impact on Classroom(s)

a. New Lessons in “Old” Coursesb. New Courses?c. Virtual Lab

The BTeV Experiment

Goals:

- use Tevatron to create more B quarks/mesons than ever- use the statistics to test the validity of the Standard Model- specifically look for CP violation (a “preference” for matter)

Techniques

- build a new detector facility, a la CDF and D0- use low-cost computing techniques, in bulk, for fast decisions- use new technologies to precisely recreate particle tracks

Time Frame

- be ready by 2005

My Role on the BTeV Team

The BTeV team asked me to design some electronics fora photomultiplier tube, a device used to measure the energy of photons (and particles that produce photons) that are created during the collision of protons with anti-protons.

Photomultiplier Tube (PMT) Basics:

- a series of metallic plates held at increasing voltages- first plate (photocathode) receives light through a window- electrons are liberated via the photoelectric effect- next stage receives the electrons (e-) from the first stage- each e- is capable of releasing 3-4 more e- at the next stage- multiple stages results in lots (millions) of e-- output of last stage (anode) needs to be counted

Base Electronics Requirements

- establish and maintain the high voltages needed for each stage- take up as little room as possible- dissipate as little heat as possible- produce an appropriate output signal that can be integrated- output should be a linear function of input

Number of e - = K * (Energy of Input light)

where K is a constant

A Typical Result of the Base Electronics Performance

Input Light (digitized ‘counts’)

Output Charge(digitized ‘counts’)

Each count = .25 pC.

1000 counts = 250 pC.

Response of six-stage base and tube to light of various energies

Input Light (digitized ‘counts’)

Output Charge(digitized ‘counts’)

Each count = .25 pC.

1000 counts = 250 pC.

Response of ten-stage base and tube to light of various energies

Input Light (digitized ‘counts’)

Output Charge(digitized ‘counts’)

Each count = .25 pC.

1000 counts = 250 pC.

Space-Charge Effect? Notice the “roll-off.”

Impact on Classroom(s?)

New Lessons in Old Courses

- particle interactions- electromagnetics- data analysis- astrophysical phenomena- fruits from a world-class technical library

- “hardware” (articles)- “software” (greater understanding via reading)

New Courses??

- interdisciplinary course encompassing statistics, science,

and computer technology OR- AP Statistics course?

The Photoelectric Effect Virtual Lab

- demonstrates principles of photoelectric effect- low cost (free!) option for doing High Energy Physics lab - web-based technology- student-centered, constructivist application- graphical interpretation of critical physics principle- students induce mathematical rule first induced by Einstein- students can explain why light must be considered a particle- provides students a hands-on introduction to quantum world

Photoelectric effect, metal is potassium

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1E-18

2E-18

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5E-18

6E-18

0 2E+15 4E+15 6E+15 8E+15 1E+16

Frequency (Hz)

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Photoelectric effect, metal is zinc

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0 1E+15 2E+15 3E+15 4E+15 5E+15 6E+15

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Photoelectric effect, metal is magnesium

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2E-19

4E-19

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Intensity (%)

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Photoelectric effect, metal is potassium

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Many Thanks for a Special Year:

- Fermilab Education Office: Tom, Liz, Marge, Spencer, Melissa, Lamargo, and Nancy, for ideas, support, and laughs - Fermilab’s Visual and Media Services, for tech help- BTeV experimenters, for taking me on as a Fellow- Fermilab Library Staff, Celina and Rob, for research and ideas- Woodstock HS School Board, for granting this sabbatical- Teaching Colleagues, for keeping me connected- Russell and Ward, our unofficial guides to Chicago- my families and friends, for their love and support

- and to Beth, who, in the course of this past year, left TWO jobs that she loved so that I might pursue this amazing opportunity, and without whom I never would have dreamed it, pursued it, or lived through it. I am blessed to share my life with her. Thank You!

Thanks to all who made this a remarkable year!