HCP: Particle Physics Module, Lecture 5 Plan for today: Discuss several historical examples of the benefits of basic physics research to society

Benefits of Fundamental (Basic) Physics Research to Society About $4.0 billion is spent each year by the United States on what is considered fundamental physics research This is compared to the total U.S. federal government budget of ~ $2.8 trillion How does this investment by the taxpayers in basic physics research benefit society? To answer this question, we will consider several past examples from the AIP (American Institute of Physics) “Physics Success Stories”

Why should the United States pursue basic physics research? One answer comes from Robert Wilson, founding director of the Fermilab Accelerator in Illinois: But, if that were the only reason why isn’t the annual physics research budget ($4.0 billion) more like the National Endowment for the Arts budget ($130 million)?

Invention of semiconductor transistor (Bell Labs, 1947) was essential here.

Invention of the Semiconductor Transistor – Bell Labs 1947 Basic physics research in the quantum physics of solids was essential to the development of the semiconductor transistor.

Why are Semiconductor Transistors so Important? Transistors can be used to make voltage controlled switches. This is essential ingredient to the digital switching logic (0 and 1) that makes all computers work.

Integrated Circuits The development of integrated circuits made desktop computers possible – millions of transistors on a thumbnail sized chip of silicon.

Integrated Circuits

MASER: “Microwave Amplification by Stimulated Emission of Radiation” LASER: “Light Amplification

How A Laser Works – the three minute version Research on the quantum mechanics of atoms and radiation eventually led to the development of the LASER: “Light Amplification by Stimulated Emission of Radiation”

World Energy Consumption Within ~ 300 years supplies of fossil fuels will run out: One possible alternative: Nuclear fusion (same process that powers the stars): deuterium (from heavy water) electrical power generation

There are 2 billion people in China and India who would like to have the same standard of living as the U.S.

Nuclear Power – electrical energy from nuclear fission Based on a controlled chain reaction: Example: These neutrons can initiate further reactions  chain reaction Neutrons are emitted with kinetic energy: neutrons slow down  heat is generated  water is heated up  steam is created  turbine turns  generator  electricity

Proliferation Issue Natural uranium is 0.72% 235U and 99.28% 238U Only 235U is useful for fission because it can be fissioned by “slow” neutrons. Reactor grade uranium: ~3% 235U Weapons grade uranium: ~ 90% 235U OR “breed” useful fissionable material (239Pu) from the more abundant 238U:

Magnetic Resonance Imaging (MRI) Also called nuclear magnetic resonance (NMR). Came from fundamental research into the magnetism of atomic nuclei. Makes use of the magnetism of the proton: When radio waves (no tissue damage) of proper frequency are applied, the proton “magnets” flip to the opposite direction Magnetic field direction

Example of a MRI facility

PET (positron emission tomography) Uses radioactive (short-lived) nuclei created in low energy particle accelerators Medical use: Tag glucose with radioactive form of fluorine (18F) Then you can follow and track where the glucose is used in the body! PET setup:   BGO BGO   BGO = photon (x-ray) detector  Timing difference between the emitted photons  spatial positions  spatial profile of glucose usage  tomography!

Equipment needed at a PET facility Cyclotron (type of accelerator) Used to produce the radioactive nuclei: 18F Patient inserted into cavity surrounded by BGO  detectors 

Example of PET scans FDG = 2-fluoro – 2 deoxy – D - glucose Huntington disease brain Decreased metabolic activity in basal ganglia Responsible for some body motor functions basal ganglia Normal brain Note: the dark areas in each picture are areas of high metabolic activity; ie. places where glucose is being consumed basal ganglia