Joint Institute for Nuclear Astrophysics

1. Joint Institute for Nuclear Astrophysics Marble Nuclei: a Guided Tour For use with “Learning Nuclear Science With Marbles” version 4.2 JINA is supported by the National Science Foundation through the Physics Frontier Center program.

2. JINA-CEE & That Great Nuclear Science Laboratory in the Sky

3. Nuclear astrophysics Michigan State University’s National Superconducting Cyclotron Laboratory One of the JINA centers; a focal point for nuclear theory and research

4. Magnet safety The silvery magnet at the core of your “nucleus” is a rare-earth or neodymium magnet… very strong for its size. Don’t put that magnet in contact with anything that is magnetically sensitive (credit cards with a magnetic stripe, for instance)! If you get two of them together, careful they don’t pinch your fingers! You will likely drop some (or all) of your marbles. If you can’t find them, they are probably attached to a metal table leg or similar. Check: do you have 6 yellow & 6 green marbles? Now: PLAY with the nucleus for two minutes (it’s a toy, after all)!

5. The nucleus Studying the atomic nucleus Proton Neutron Electron All matter is made of atoms, and the nucleus is the heavy core of the atom An atom

6. …as you are compared to our ENTIRE solar system The nucleus is SMALL An atomic nucleus is as small compared to you… • There are 100 million atoms across your fingernail • The nucleus is 10,000 times smaller than the atom itself

7. Build a model nucleus • Proton • Neutron • Electron • Positron • Magnet to hold it all together Magnetic marbles make it possible!

8. Build a model nucleus • Proton (positive, heavy) • Neutron (neutral, heavy) • Electron (negative, light) • Positron (positive, light) • (ignore) Magnetic marbles make it possible!

9. Periodic Table and Nuclei

10. A nucleus by any other name Worksheet Part 1 • Number of protons determines the element • 4 protons = Beryllium • Number of neutrons determines the isotope • 5 neutrons (+ 4 protons) = Beryllium-9

11. Name that isotope Beryllium-9 Beryllium-8 Beryllium-10

12. Isotopes on a graph

13. All these carbon isotopes are chemically identical, but different numbers of neutrons gives them diverse nuclear properties A Periodic Table for Nuclei Protons (Elements) Neutrons (Isotopes)

14. Read your Chart of the Nuclides Build a random nucleus and name it!

15. Isotopes: stable or unstable? Worksheet Part 2 NSCL studies very unstable isotopes Stable nuclei are permanent and common. 100% of beryllium found in nature will be this isotope.

16. What makes an isotope unstable? Objects in our universe tend to move to the lowest possible energy state Valley of Stability (lowest-energy nuclei)

17. Why do unstable isotopes decay? • To get to a lower energy, of course! • The amount of energy in a nucleus is lower when it has: • About equal numbers of protons and neutrons • He-4, Li-6, B-10… • Or slightly fewer protons than neutrons (protons repel) • Li-7, Be-9, B-11, C-13, N-15… • Even numbers of neutrons and/or protons (pairs) • He-4, He-6, He-8! But NOT He-5, He-7. • Build a carbon-12. According to the rules above, should it be low-energy (stable)? Note: these are general rules from the nuclei we’ve measured, and sometimes these rules can be broken!

18. Beta-minus decays Too many neutrons, or not enough protons Valley of Stability

19. Beta-plus decays Not enough neutrons, or too many protons Valley of Stability

20. How do decays lower energy? Worksheet Part 2 NSCL studies very unstable isotopes

21. Radioactive decay changes isotopes After a series of decays, carbon-9 becomes helium-4

22. Unstable nuclei have a lifetime Worksheet Part 3 Be-10 decays to B-10 with a half life of 1.6 million years (flip something!)

23. Nuclear reactions Worksheet Part 3 How new elements and isotopes are made

24. Decay: unstable nuclei change

25. The nucleus splits into two smaller ones (fission), releasing three fast neutrons A neutron strikes a uranium-235 nucleus The fast neutrons may run into other nearby nuclei, if there are enough around Those nuclei undergo fission, and the chain reaction continues Fission: nuclei produce power

26. Fusion: sunlight is born During fusion, a tiny amount of mass is converted to energy, and a heavier element is created! When you “fuse” your marbles, does any energy come out?

27. Fragmentation: when nuclei smash This is how researchers at NSCL make the rare, unstable isotopes they want to study

28. Nuclear Reactions on Earth Are caused by: • Cosmic rays hitting nuclei in our atmosphere • Natural radioactivity • Nuclear power plants • Accelerator laboratories like NSCL

29. 3a: Advanced Binding Energy • “Binding energy” is the amount of energy that is necessary to break a nucleus completely apart (to protons and neutrons) • Binding energy is measured in MeV, which is a really small amount • More binding energy • more tightly bound nucleus • longer-lasting/more stable

30. 3a: Radioactivity • Nuclei can minimize their overall energy (i.e. become more tightly bound) through radioactive decay • The steeper the drop in energy, the faster that process will go (shorter half-life)

31. 3a: Magic Numbers • The lowest-energy nuclei are the stable isotopes. • Isotopes with just enough protons or neutrons to close a quantum energy shell (the “magic number”) are the lowest. • A nucleus is considered “magic” if it has this many protons or neutrons (or even “doubly-magic” if both): • 2 8 20 28 50 82 126

32. 3a: Binding by Element To change a nucleus to one that is less bound (moving down the graph) requires you to put energy in. Thus, changing a nucleus so that it moves up the graph means that energy comes out! Do these reactions release or consume energy? H fuses (combines) to He Three He-4 fuse to C-12 U fissions (breaks) into lighter elements Fe fuses or fissions Which one releases the most energy?

33. What nuclear scientists study Worksheet Part 4

34. Isotopes: many shapes and sizes The S800 spectrograph at NSCL measures nuclear size and shape

35. Limits of stability How far can nuclei go? … Proton “dripline”? UNBOUND Neutron“dripline”? UNBOUND

36. Making the Elements Black boxes are stable isotopes Protons (Elements) Iron common rare Neutrons (Isotopes) Nuclei are bombarded with neutrons, forming rare isotopes that will decay into stable heavy elements

37. Marble nuclei activities Fragmentation box Isotope BINGO Nucleosynthesis Game