Accelerating Uranium in RHIC – II Surviving the AGS Vacuum

This Report is about the description of the survival rate of charge 90+ uranium ions in the AGS vacuum

The Partial Beam Lifetime at RHIC due to Coulomb Dissociation of the Nucleus

During beam crossing at RHIC, the Lorentz contracted Coulomb interaction between the heavy ions will excite internal modes of the nucleus. The subsequent decay of these modes is predominately via single or multiple nucleon emission. Changing the atomic mass Of the beam ion will eventually cause beam intensity loss at RHIC for the radius of the ion orbit is sensitive to changes of the ratio Z/A. While calculations for this beam loss mechanism have been made, it is now clear that these earlier theoretical studies underestimated the Coulomb dissociation loss rate for they appear to have included only a limited range of internal nuclear excitation energy. In this report we reexamine the question of Coulomb dissociation cross sections at RHIC by including internal excitation energies up to thousands of GeV. In addition, we utilize experimental photonuclear absorption cross sections when evaluating the dissociation cross section. Also, internal excitation of a nucleus in one beam wig result in both energy loss and transverse momentum change of an ion in the colliding beam. These recoil effects will be examined in detail to determine if there is an additional loss rate for ions out of the rf bucket or a non-negligible change in the ion's betatron momentum

Emittance Growth, Tune Shift and the Bunched-Beam, Bunched-Beam Interaction

While it is understood that the main limitation of beam lifetime in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven is the emittance growth due to intra-beam scattering, it is important to evaluate and understand both the emittance growth and nature of the tune shift due to multiple beam-beam crossings of the bunched-beams of heavy ions. We note within RHIC, fully stripped /sup 197/Au ions (charge 79e/sup +/) will survive up to ten hours in the collider, with six beam crossings per revolution. With this motivation, we have developed a fully relativistic theory of both the averaged emittance growth and the averaged tune shift for the bunched-beam, bunched-beam interaction that is based on a convolution integral over the densities of the two interpenetrating bunches. In order to calculate this integral, we choose to work in a frame where one bunch of the collider is stationary, and the other is highly relativistic. This frame has the additional advantage that the microscopic heavy ion interaction becomes perpendicular in nature. In this frame the convolution integral acquires many simplifying and physically interesting features. 8 refs

Analytic Studies of Decapole Correction Schemes

In this report, the decapole corrector scheme proposed for RHIC is reviewed and the effectiveness of a two family scheme is compared with a three family scheme

Asymptotic Normalization Coefficients for 13C+p->14N

The $^{13}C(^{14}N,^{13}C)^{14}N$ proton exchange reaction has been measured at an incident energy of 162 MeV. Angular distributions were obtained for proton transfer to the ground and low lying excited states in $^{14}N$. Elastic scattering of $^{14}N$ on $^{13}C$ also was measured out to the rainbow angle region in order to find reliable optical model potentials. Asymptotic normalization coefficients for the system $^{13}C+p\to {}^{14}N$ have been found for the ground state and the excited states at 2.313, 3.948, 5.106 and 5.834 MeV in $^{14}N$. These asymptotic normalization coefficients will be used in a determination of the S-factor for $^{7}Be(p,\gamma)^{8}B$ at solar energies from a measurement of the proton transfer reaction $^{14}N(^{7}Be,^{8}B)^{13}C$.Comment: 5 pages, 6 figure

Tests of Transfer Reaction Determinations of Astrophysical S-Factors

The ${}^{16}O ({}^{3}He,d) {}^{17}F$ reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ${}^{17}F$. The coefficients provide the normalization for the tails of the overlap functions for ${}^{17}F \to{}^{16}O + p$ and allow us to calculate the S-factors for ${}^{16}O (p,\gamma){}^{17}F$ at astrophysical energies. The calculated S-factors are compared to measurements and found to be in very good agreement. This provides the first test of this indirect method to determine astrophysical direct capture rates using transfer reactions. In addition, our results yield S(0) for capture to the ground and first excited states in $^{17}F$, without the uncertainty associated with extrapolation from higher energies.Comment: 6 pages, 2 figure

How does breakup influence the total fusion of 6,7^{6,7}Li at the Coulomb barrier?

Total (complete + incomplete) fusion excitation functions of $^{6,7}$Li on $^{59}$Co and $^{209}$Bi targets around the Coulomb barrier are obtained using a new continuum discretized coupled channel (CDCC) method of calculating fusion. The relative importance of breakup and bound-state structure effects on total fusion is particularly investigated. The effect of breakup on fusion can be observed in the total fusion excitation function. The breakup enhances the total fusion at energies just around the barrier, whereas it hardly affects the total fusion at energies well above the barrier. The difference between the experimental total fusion cross sections for $^{6,7}$Li on $^{59}$Co is notably caused by breakup, but this is not the case for the $^{209}$Bi target.Comment: 9 pages, 9 figures, Submitted to Phys. Rev.

Collective Modes of Tri-Nuclear Molecules

A geometrical model for tri-nuclear molecules is presented. An analytical solution is obtained provided the nuclei, which are taken to be prolately deformed, are connected in line to each other. Furthermore, the tri-nuclear molecule is composed of two heavy and one light cluster, the later sandwiched between the two heavy clusters. A basis is constructed in which Hamiltonians of more general configurations can be diagonalized. In the calculation of the interaction between the clusters higher multipole deformations are taken into account, including the hexadecupole one. A repulsive nuclear core is introduced in the potential in order to insure a quasi-stable configuration of the system. The model is applied to three nuclear molecules, namely $^{96}$Sr + $^{10}$Be + $^{146}$Ba, $^{108}$Mo + $^{10}$Be + $^{134}$Te and $^{112}$Ru + $^{10}$Be + $^{130}$Sn.Comment: 24 pages, 9 figure