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Kirby W. Kemper

Kirby W. Kemper. Current Research In Radioactive Beam Physics A New Era Is About To Happen. We will have new facilities, new computational power and the ability to do experiments with any beam you can think of soon. Map of Florida.

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Kirby W. Kemper

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  1. Kirby W. Kemper Current Research In Radioactive Beam Physics A New Era Is About To Happen We will have new facilities, new computational power and the ability to do experiments with any beam you can think of soon

  2. Map of Florida

  3. Florida State University in 1851-First as a seminary for men then in 1904 as a women’s college and then in 1947 became a co-ed university. Today has 39,000 students.

  4. Westcott Building, Florida State University, Tallahassee.

  5. Accelerator Laboratory at Florida State

  6. Solenoid 1 Magnetic Spectrograph Target Position Solenoid 2 RF-Resonator RF-Resonator Magnetic Spectrograph Mass selectionslits Production target Experiment Experimental Nuclear Physics at Florida State University • Our new “discovery machine:” • We have built a new facility for in-flight production of exotic beams:RESOLUT • Completed first two experiments in 2007 • The program

  7. The Cast • Dr. Lagy T. Baby • Graduate Students: Joel Fridmann, Eric Diffenderfer, Allison Bernstein, Patrick Peplowski,Eric Johnson (G. Rrogachev)Rob. Reynolds (P. Cottle)Peter Wilson (Univ Surrey, UK)‏ • Undergraduate Students (REU):Y.K.-Lee, Rachel Goodlet, Joseph Brossett, David Arthur, Cliff Burchfield Supported by NSF OJI-grant to I.W.

  8. There are two ways in which physics tries to obtain a consistent picture of the structure of the atomic nucleus. One of these is the study of the elementary particles, their properties and mutual interactions. Thus one hopes to obtain a fundamental knowledge of the nuclear forces, from which one can then deductively understand the complicated nuclear structures. The other way consists in gaining, by direct experimentation, as many different data as possible for individual nuclei, and examining the relations among these data. One expects to obtain a network of correlations and connections which indicate some elementary laws of nuclear structure. These two ways have not yet met to establish a complete understanding of the nucleus, although many connections have been found. “Elementary Theory of Nuclear Shell Structure” M.G. Mayer and J.H.D. Jensen 1960

  9. How do we know we have seen new physics with radioactive beams? We must have high quality stable beam data for comparison So I will discuss both types of experiments Start with simplest thing possible: elastic scattering

  10. Classic Fresnel scattering problem

  11. Optical Model for Elastic Scattering

  12. I will show you that elastic scattering is dependent on the details of the internal structure of the projectile by reviewing some old and some new data. I also hope to convince you that elastic scattering does not depend on the details of the target for a specific range of scattering angles. Our test nuclei for the most part will be 6Li and 7Li, but will also include 6He and others.

  13. 6Li and 7Li nuclei

  14. John Blair first predicted that one might see projectile structure effects in the scattering of heavy-ions ( Phys. Rev. 115 (1959) ). Is there even a more direct way to see the presence of the g.s. quadrupole moment ? Scatter Polarized 6Li and 7Li beams

  15. 6Li and 7Li scattering on 58Ni

  16. Lets see what happens when elastic scattering is measured very accurately Compare 6Li and 7Li scattering on Pb just above the Coulomb barrier

  17. 6Li, 7Li + 208Pb Elastic Scattering at 39 MeV N. Keeley et al. Nucl. Phys. A571 (1994) 326.

  18. 6Li, 7Li + 208Pb Elastic Scattering at 39 MeV

  19. Comparison of 6Li and 6He (*) I. Tanihata et al. PLB 206, 592 (1988).

  20. 6He + 208Pb at 29.6 MeV (R. Raabe et al.) K. Rusek et al PRC67 (2003) 041604

  21. Conclusions from Li-6He study Virtual coupling to resonant and continuum states has direct influence on near-barrier elastic scattering from heavy targets in Coulomb rainbow region. Breakup threshold is perhaps the dominant factor as its energy determines where the continuum starts. With radioactive beams can probe role of breakup threshold, resonant states and continuum structure by choice of beam - use same target and energy relative to the Coulomb barrier.

  22. Possible elastic scattering experiments with a Pb target. 8B very low threshold (8B →7Be + p = 0.14 MeV) must also measure 7Be + target. Is 8B a proton halo? 7Be has lower threshold (1.59 MeV) than 7Li (2.47 MeV) but similar internal structure. How does scattering pattern change? Look at influence of b.u. threshold on scattering. 11Li →9Li + 2n (0.25MeV) very strong dipole excitation to continuum again need to measure 9Li + target (Y.Sakuragi, S. Funada and Y. Hirbayashi Nucl. Phys. A588 (1995) 65c, M.V. Andrés and J. Gómez-Camacho PRL 82 (1999) 1387). 11Be effect of strong dipole transition to bound state 1/2+  1/2- (0.32 MeV) threshold to 10Be+n (0.503 MeV)

  23. We were lucky in these first studies in that energy was just above Coulomb barrier, where the dipole is strongly excited through the Z2 contribution. Had the energy of the 6He beam been a lot higher, we would not have seen this virtual E1 effect What happens if we go to much higher energies where the scattering is pure nuclear? Here you will see that how you graph data sometimes obscures the physics.

  24. Comparison in Ratio to Rutherford Versus the momentum transfer qt = 2k sin(θcm/2)

  25. 6He, 6Li Scattering Experimental data for 6Li and 6He elastic scattering on 12C target at different energies as a function of angle and momentum transfer :

  26. Now lets switch to transfer reactions and the never ending question of spectroscopic factors. Remember, a single particle spectroscopic factor would be for example, the probability that the ground state of 17O looks like 16O+ 0d5/2 neutron As a reminder, the goal of reactions like (d,p) and (p,d) was to map out single particle strengths and to determine the centroid of their energies. B. L. Cohen et al Rev Mod Phys 35 (1963) 332 First look at existing (d,p) and (p,d) data from stable targets. What are the folklore problems?-Optical model parameters, bound state wave functions, etc

  27. A simple one step stripping reaction may be written diagramatically asA+a → B+bA + (b+x)a→ (A+x)b+bwhere A represents the target core, b represents the projectile core, and x is the transferred mass which may represent any number of particles.

  28. In the prior formalism, the cross section is related to the transition matrix element in which Vbx and VbA represent the interaction potentials between b and x, and between b and A respectively. The UbB is the optical model potential which describes the elastic scattering in the exit channel: the Ψ’s represent the internal wave functions of the distorted waves which describe the elastic scattering of the colliding systems aA and bB.

  29. A typical reaction

  30. J. Lee, M. B. Tsang and W. G. Lynch PRC 064320 (2007); M. B. Tsang, J. Lee et al PRL 102 062501(2009)

  31. When you do a consistent analysis of (d,p) and (p,d) reactions the spectroscopic factors make sense and the data can be used to test structure interactions. However, please don’t take this to mean we know the absolute spectroscopic factor for transfer to a given nuclear state to better than ±20% What about (d,p) with low energy radioactive beams? Lots of examples now using inverse kinematics--- Oak Ridge data Remember, we are looking for changes in shell structure because of being at the n dripline

  32. Now lets switch to transfer reactions with beams whose energy are 100MeV/amu These slides are from Alexandra Gade from MSU At present this is the only way to do structure studies far from the island of stability What makes these experiments feasible is the large cross sections and new detection capabilities. You must do particle-gamma-ray coincidences to select out states populated. Remember though you must calibrate reaction

  33. In-flight production of rare isotopes at the NSCL Focal plane Reaction product identificationS800 spectrograph Driver accelerator (v = 0.25-0.6 c) • Fragment separator (A1900) • Identification and beam transport • Stopped beam experiments, reaccelerated beam experiments • Fast beam experiments • Secondary reaction • Reaction product identification (S800 spectrograph) Identification and beam transport Reaction target Fragment separatorA1900 fragment separator Production target

  34. Example s = 10 mb NT = 2 1022 cm-2 (300mg/cm29Be) NB = 30 projectiles/s NR =520/day reactedbeam beam target • Experimental tasks • Particle spectroscopy • Identification of the reaction residues • Momentum distribution • - -ray spectroscopy • Identify the final state In-beam spectroscopy with fast beams at rates of a few nuclei per second v/c > 0.3 • Fast exotic beams allow for • thick secondary targets (100-1000 thicker than at low beam energy) • event-by-event identification Typical cross sections: one-nucleon knockout: 10-150 mb two-nucleon knockout: 0.10-1.50 mb

  35. Reduction Factor-A. Gade, NSCL Shell M

  36. So what we find now is that as you study the most deeply bound nuclei by proton or neutron removal, there is a large reduction in the extracted spectroscopic factor relative to that expected from structure calculations Is this reduction real, or a result of the theoretical calculations being done?

  37. What studies are needed-- Coul Ex that goes beyond first 2+--Resonance reactions to look for states predicted by no core shell model in light nuclei-- Mass measurements at neutron dripline-- Many transfer reactions With all of the new facilities proposed, coming on-line and that will be coming on line in the next few years, it is an exciting time to be a nuclear physicist Thank you

  38. Magnetic spectrograph Solenoid 2 Solenoid 1 Ion beam from linac Q Q Q Q D Mass-dispersivefocal plane Production target SuperconductingRF-resonator Experiment RESOLUT The RESOLUT radioactive beam facility • In-flight production of radioactive beams • Beam “cooling” with superconducting RF • Velocity bunching creates mass-dispersive focal plane

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