1. 1)Why study nuclei 2)Basic facts about Nuclei 3)Nuclear structure and nuclear reactions 4)Basic facts about collisions and reactions 5)Where we do our experiments 6)How we do the experiments 7)What one can learn from debris Part I: An introduction to basic nuclear science Romualdo T. de Souza Nuclear Chemistry at Indiana: http://nuchem.iucf.indiana.edu

2. Romualdo de Souza 1) Why study nuclei? Nuclei are at the heart of every atom; What is their structure, properties? What is the nature of the force that hold them together? Necessary to understand the formation of the elements – nucleosynthesis Important in understanding the properties of astrophysical objects such as neutron stars ( a giant nucleus with a radius of ~ 0.6 km)  nuclear equation-of-state. Important in understanding the thermodynamic properties of small, finite systems (ties to the study of atomic clusters). Important in understanding nuclear fission and nuclear fusion (energy source/ weapons) Neutrons Protons Stable Nuclei Known Nuclei Terra Incognita

3.  Fundamentals of supernova explosions are not understood!  Synthesis of the heavy elements is not understood  Limits of nuclear stability (superheavy elements, N/Z exotic) poorly known Only elements Z=1-4 produced in the Big Bang 1) Why study nuclei?

4. 2) Basic facts about nuclei: Nuclei behave like microscopic drops of liquid (fairly incompressible yet deformable). Nuclei are small (R= 1-10 x 10 -15 m);10 4 -10 5 times smaller than an atom; requires measuring instruments of a comparable size to measure them e.g. other nuclei Nuclei are positively charged so one has to overcome the mutual repulsion between two nuclei (Coulomb repulsion) i.e. Particle accelerators are required. ChemistryNuclear Chemistry Distance10 -10 m10 -15 m Density1-10 g/cm 3 2 x 10 14 g/cm 3 Time10 -14 s 10 -22 s

5. 2) Basic facts about nuclei: Binding energy TBE= Total Binding Energy Analogous to the heat of vaporization Binding energy curve for nuclei TBE/A = “average bond strength” How can one understand this binding energy curve?

6. 2) Basic facts about nuclei: The liquid drop model Charge denisty,  Radial distance (r) TBE = C 1 A  C 2 A 2/3  C 3 Z 2 /A 1/3  C 4 (N-Z) 2 /A 2 + C 6  /A 1/2 = C 1  C 2 A  1/3  C 3 Z 2 /A 4/3  C 4 (N-Z) 2 /A 3 + C 6  /A 3/2 volumesurfaceCoulombsymmetrypairing = TBE/A

7. 2) Basic facts about nuclei: The liquid drop model The first three terms in the liquid drop model (Volume, surface, and Coulomb) already explain the shape and magnitude of the Binding energy curve for nuclei.

8. 2) Basic facts about nuclei: The shell model Nuclei are not “formless blobs”. They have an internal structure in which protons and neutrons occupy orbitals much as in the atom (though with differences). Proton number Z Neutron number N (M measured – M liquid drop )c 2 Red arrows indicate nuclei of additional stability. They occur at the MAGIC NUMBERS: 2,8,20,50,82, and 126

9. 3) Nuclear structure and nuclear reactions Nuclear structure involves studying the internal levels in a nucleus. Since the transition between levels involves the emission of gamma rays, nuclear structure involves gamma ray spectroscopy 110 Ge detectors on a 10 inch radius sphere The next generation: Segmented Gamma ray detectors (GRETINA)

10. 3) Nuclear structure and nuclear reactions  total number of protons is conserved  total number of neutrons is conserved  Q (energy release) can be either positive (exothermic) or negative (endothermic)  to get the nuclei to react one must get into the range of the short range nuclear force (projectile and target nuclei must touch)  The reaction products are quite likely excited (their protons and neutrons are not in the ground state) and they will de-excite by emission of gamma rays, neutrons, protons, alpha particles and other clusters.

11. t=0 ms30 ms60 ms90 ms120 ms150 ms Fusion-like event Impact parameter selection: direct inspection Strongly Damped/Deeply inelastic event Deep inelastic + neck emissions event Classical drops: Collisions of mercury drops camera Deposit of a fraction of initial kinetic energy into heat and stretching the drops. How strong is the inter-atomic interaction? Role of surface tension. We want to study the same type of processes but with nuclear drops to learn about the forces holding nuclei together! 4) Basic facts about collisions and reactions?

12. Supercomputer simulations of 114 Cd + 92 Mo at E/A = 50 MeV; b=7.37 fm Antisymmetrized Molecular Dynamics

13. IU Cyclotron Facility The Indiana University Cyclotron Facility (IUCF) is a multidisciplinary laboratory performing research and development in the areas of accelerator physics, nuclear physics, materials science, life science and biomedical applications of accelerators. Accelerator Physics Accelerator Physics Defining the physics of producing and handling beams of sub-atomic particles Nuclear Physics and Chemistry Nuclear Physics and Chemistry Probing matter and forces at the sub-atomic scale Neutron Physics Neutron Physics Using neutrons to explore the molecular structure of proteins, crystals, surfaces, and much more Materials Research Materials Research Imaging, modeling and manipulating macromolecules Biomedical and Life Sciences Biomedical and Life Sciences Harnessing the power of radiation for research in biology and medicine http://www.iucf.indiana.edu

14. 5) Where we do our experiments (the accelerator side)

15. Up to C at 96MeV/A or U at 24MeV/A CSS1, CSS2 K=380 SISSI - fragmentation beams SPIRAL - re-acceleration of radioactive beams with CIME Ion sources

16.  4 dipole magnets act to bend the moving charged particle in a circular orbit  a voltage applied at radiofrequency as the particle moves between the dipoles causes the particle to accelerate, therefore spiraling outward  When the particle reaches the maximum radius of the cyclotron it is at the maximum energy and is extracted by a small electrostatic deflection Principle of acceleration of a cyclotron

17. A sense of scale : A K=200 cyclotron (IUCF)  Remember that GANIL has two K=380 cyclotrons coupled sequentially  Michigan State has two coupled superconducting cyclotrons (K=500 and K=1200)

18. 6) How we do our experiments (the detector side) Interaction of radiation with matter! Charged particles: protons, deuterons, tritons, alpha particles, intermediate mass fragments (IMF: 3≤Z≤20), fission fragments Neutral particles: gamma rays neutrons Gas detectors (incident particles cause ionization) Solid state detectors: Si, Ge (incident particles cause electron-hole pairs) Scintillators: liquid, plastic (incident particles cause scintillation)

19. 6) How we do our experiments (the detector side) E detector Incident particle with (Z,A,E) dx  E detector dE  Z 2 A dxE Interaction of radiation with matter! Different “bands” represent different isotopes.

20. 6) How we do our experiments (the detector side) Segmented Si detectors Backed by CsI(Tl) with photodiode readout … Are stacked to make a telescope… And electronics… 4x CsI(Tl) 4cm 16 strips v. (front) Target Beam Si-  E 65  m 16 strips v (front) Si-E 1.5 mm pixel 16 strips h. (back)

21. 6) How we do our experiments (the detector side) Many telescopes are combined together to give as complete a measurement as possible.

22. Collision of a nucleus with a light-ion (Z 2) converts kinetic energy of relative motion into intrinsic excitation i.e. heats the nucleus. From the debris – the fragmentation pattern we need to determine what happened identity of all the particles number of clusters (Z>2) number of light particles Z=1,2 energy of all the particles angles of all the particles 7) What one can learn from debris

23. 162 individual telescopes covering 74% of 4  Gas Ionization chamber/500 µm Si(IP)/CsI(Tl(PD) Each telescope measures Z,A, E, and  Identification of Z for 0.6≤E/A ≤96 MeV Identification of A for E/A ≥ 8 MeV for Z≤4 ISiS: Indiana Silicion Sphere We measure all information collision-by-collision (event-by-event). 4  measurements

24. Physical Chemistry, R. Chang, 2000 H 2 gas v (m/s) P(v) Charity, et.al., PRC (2001) Maxwell Boltzmann distribution Coulomb Barrier for α-particles Helium Isotopes Kinetic equilibrium: motion of all particles reflects a common temperature Kinetic energy spectra fit  Maxwell-Boltzman distribution  T Slope Thermometers

25. Angular distribution: comparing emission time to rotation time Circular ridge  PLF* emission “Isotropic” component Projectile velocity Other emission (mid-rapidity,...) When the rotation time is short compared to the emission time, a uniform emission pattern is observed. Emission from a hot nucleus

26. Chemical equilibrium: different partitions are populated according to their statistical weights. Emitting system 10 B 6 Li  F. Zhu et al., PRC52, 784 (1995) Relative energy spectrum of daughters reflects internal quantum levels of parent P m = (2J m +1)e -(E*-Em/T) P m /P n = (2J m +1)/(2J n +1)e -(En-Em)/T Extract temperature T Another Thermometer: Excited state populations

27. Phase transitions for small, finite, open systems  Transition from one phase to an other at constant T Constant P Infinite matter Closed system “Caloric curve” for nuclear matter Liquid phase Gas phase Liquid-gas coexistence  BOILING ? J. Pochodzalla et al., PRL 75, 1040 (1995) ChemistryNuclear Chemistry Distance10 -10 m10 -15 m Density1-10 g/cm 3 2 x 10 14 g/cm 3 Time10 -14 s 10 -22 s