Beam dynamics studies in the driver LINAC pre-stripper section of the RIA facility

The RIA facility driver LINAC consists of about 400 superconducting (SC) independently phased rf cavities. The LINAC is designed to accelerate simultaneously several charge-state beams to generate as much as 400 kW of uranium beam power. The LINAC beam dynamics is most sensitive to the focusing and accelerating structure parameters of the pre-stripper section, where the uranium beam is accelerated from 0.17 keV/u to 9.4 MeV/u. This section is designed to accept and accelerate two charge states (28 and 29) of uranium beam from an ECR ion source. The pre-stripper section must be designed to minimize the beam emittance distortion of this two-charge-state beam. In particular, the inter-cryostat spaces must be minimized and beam parameters near transitions of the accelerating and focusing lattices must be matched carefully. Several sources of possible effective emittance growth are considered in the design of the pre-stripper section and a tolerance budget is established. Numerical beam dynamics studies include realistic electric and magnetic three-dimensional field distributions in the SC rf cavities and SC solenoids. Error effects in the longitudinal beam parameters are studied.     

Multi-strange-quark states at ultra-relativistic heavy-ion collisions

We examine the possibility of producing and evidencing exotic strange matter (strangelets and metastable multi-hypernuclear objects, MEMO’s), including also pure hyperonic bound states ((ΛΛ)_b, (ξΛ)_b), at RHIC and LHC. Simulations are presented to estimate the sensitivity of the STAR and ALICE experiments to the detection of these objects, focusing mainly on metastable short-lived (weak decaying) strange dibaryons, with a particular emphasis on theH-dibaryon, a six quark-bag bound state (uuddss).     

The comparison of characteristics of π− mesons produced in central Mg-Mg interactions with the quark gluon string model predictions

A detailed study of pion production in central Mg-Mg collisions at a momentum of 4.3 GeV/c per incident nucleon was carried out with use of the setup GIBS. The average kinematical characteristics of pions (multiplicity n ₋, momentum P, transverse momentum P _T, emission angle Θ, rapidity Y) and corresponding distributions have been obtained. The experimental results have been compared with the predictions of the Quark Gluon String Model (QGSM) and satisfactory agreement between the experimental data and the model has been found. The QGSM reproduces also the dependence of average P _T on n ₋. The temperatures of π⁻ mesons have been estimated in the rapidity interval of 0.5 ≤ Y ≤ 2.1. A satisfactory fit for π⁻ mesons has been achieved by using a form involving two temperatures T ₁ and T ₂. It is found that the QGSM underestimates T ₂ by (10−15)%. The data have been analyzed using the transverse momentum technique. The observed dependence of the <P _x ^′(Y)> on Y shows the S-shape behaviour. The slope at midrapidity F has been determined. The QGSM reproduces the <P _x> distribution satisfactorily, but underestimates the parameter F. Received: 2 August 1997 / Revised version: 17 November 1997     

Single-sheet identification method of heavy charged particles using solid state nuclear track detectors

The theoretical and experimental investigations of the penetration of charged particles in matter played a very important role in the development of modern physics. Solid state nuclear track detectors have become one of the most important tools for many branches of science and technology. An attempt has been made to examine the suitability of the single-sheet particle identification technique in CR-39 and CN-85 polycarbonate by plotting track cone length vs. residual range for different heavy ions in these detectors. So, the maximum etchable ranges of heavy ions such as ⁹³Nb, ⁸⁶Kr and ⁴He in CR-39 and ⁴He and ¹³²Xe in CN-85 polycarbonate have been determined. The ranges of these ions in these detectors have also been computed theoretically using the Henke-Benton program. A reasonably good agreement has been observed between the experimentally and theoretically computed values.      

Polarization parameters in systems with spin-spin interactions

The spin-spin interaction of two arbitrary spin systems is considered in some detail. The temporal evolution of the polarization parameters and the correlation parameters has been worked out. Applications of the formalism and the interpretation of the results to processes such as heavy-ion interactions, muon and nuclear repolarization and depolarization in muonic atoms and interactions of multilevel systems are outlined.