A. J. Baltz

Exact Dirac Equation Calculation of Ionization and Pair Production Induced by Ultrarelativistic Heavy Ions

An exact solution of the time-dependent Dirac equation for ionization and pair production induced by ultrarelativistic heavy ion collisions is presented. Exact transition probabilities, equivalent to those that would be obtained in an untruncated basis coupled channels calculation, are presented. Exact bound-electron positron pair production probabilities are calculated to be mostly smaller than those calculated with the same potential in perturbation theory at impact parameters small enough for differences to occur. {copyright} {ital 1997} {ital The American Physical Society}

Evidence for higher order QED effects in e+ e- pair production at the BNL Relativistic Heavy Ion Collider.

A new lowest order QED calculation for RHIC ee pair production has been carried out with a phenomenological treatment of the Coulomb dissociation of the heavy ion nuclei observed in the STAR ZDC triggers. The lowest order QED result for the experimental acceptance is nearly two standard deviations larger than the STAR data. A corresponding higher order QED calculation is consistent with the data. PACS: 25.75.-q, 34.90.+q

Higher-order QED calculation of ultrarelativistic heavy-ion production of μ + μ − pairs

A higher-order QED calculation of the ultraperipheral heavy-ion cross section for {mu}{sup +}{mu}{sup -} pair production at the Relativistic Heavy Ion Collider and the Large Hadron Collider is carried out. The so-called Coulomb corrections lead to an even greater percentage decrease of {mu}{sup +}{mu}{sup -} production from perturbation theory than the corresponding decrease for e{sup +}e{sup -} pair production. Unlike the e{sup +}e{sup -} case, the finite charge distribution of the ions (form factor) and the necessary subtraction of impact parameters with matter overlap are significant effects in calculation an observable ultraperipheral {mu}{sup +}{mu}{sup -} total cross section.

Spiral Design and Beam Dynamics for a Variable Energy Cyclotron

Beam-orbit studies were performed for the conversion of the SREL synchrocyclotron magnet for use as a room temperature, multiparticle, isochronous cyclotron. Based on model magnet measurements of field profiles for 8 to 23 K gauss hill fields, a four sector spiral pole tip design has been realized which allows all isotope species of heavy ion beams to be accelerated to required final energies. The total spiral angle of 38° allows injection of the beams from the MP tandem into the cyclotron through a valley. The two valley RF system of 140 kV peak accelerates beams on harmonic numbers 2, 3, 4, 6 and 10 at 14 to 21 MHz. Computer calculations indicated acceptable vz, Vr and phase space beam characteristics and passing of resonances for typical beams considered: 16O at 8 and 150 MeV/amu, 60Ni at 100 MeV/amu and 238U at 2.5 and 16 MeV/amu. Single turn extraction is achieved with electrostatic deflection.