123091565
Isochronous Cyclotron with Tandem Injector for Heavy Ion Acceleration
93888470
Design Study for the Conversion of the Oak Ridge Isochronous Cyclotron from an Energy Constant of K=90 to K=300 MeV
A possible method of achieving a K=300 MeV cyclotron by increasing the average magnetic field of the Oak Ridge Isochronous Cyclotron (ORIC) from 18.6 to 33.9 kG with superconducting coils has been investigated.
115550416
RECENT PROGRESS ON A SUPERCURRENT SEPARATED ORBIT CYCLOTRON.
124286964
INNOVATIONS IN ISOCHRONOUS CYCLOTRONS.
Since the last International Conference on Isochronous Cyclotrons, three major projects have been approved: the 585 MeV proton cyclotron of the Swiss Institute for Nuclear Research (SIN) to be built at Villigen near Zurich; the 500 MeV Hcyclotron of the Tri-University Meson Facility (TRIUMF) at Vancouver, British Columbia; and the 200 MeV variable energy cyclotron of the Indiana University. A much smaller but unique project has been successfully brought into operation, the cyclograaff at Duke University which combines a small cyclotron with a tandem accelerator in a way which enhances the desirable characteristics of both. Finally, the most important happening since the last conference has been the renewed interest in accelerators for very heavy ions. In the United States alone, there will be more than ten major proposals. This paper reviews the activities and progress of the past several years and discusses some of the important innovations accomplished or foreseen.
116322052
Accelerators for Heavy Ions
The use of heavy ion accelerators in nuclear physics, nuclear chemistry, atomic physics, and in material sciences studies is rapidly increasing. This paper reviews the present and developing scene in heavy ion accelerator concepts and technology. The area of applicability of various methods, likely avenues of future development and the trends of future requirements are discussed.
124130410
HEAVY-ION ACCELERATOR FACILITY FEATURING A SEPARATED-SECTOR ISOCHRONOUS CYCLOTRON.
An isochronous cyclotron of modest size with a model TU Tandem Van de Graaff as its injector would have the capability of accelerating the heaviest ions to well above the Coulomb barrier for the heaviest elements. An evaluation of several cyclotron designs has led to an isochronous cyclotron with four separate sectors. As now envisaged the cyclotron will be capable of accelerating heavy ions with a charge-to-mass ratio of 0.15 to an energy of 7.5 MeV1a.m.u. A unique feature of the plan is the use of a source of highly charged ions of the Dubna or LRL type in the terminal of the tandem. For example, to obtain energetic uranium ions, 9+ ions from the terminal ion source are accelerated to 144 MeV (0.605 MeV}a.m.u.), passed through a stripping foil to increase the ion charge to 36+, injected into the cyclotron, and accelerated to 1785 MeV (7.5 MeV1a.m.u.). The cyclotron will also accelerate light particles, for example, protons and a-particles to about 300 MeV. deuterons to 150 MeV, and 3 ~ e 2 ' ions to 400 MeV. For this added flexibility a small cyclotron will be provided as the alternate light-ion injector. When the tandem is used separately for experiments requiring its special capabilities, the two cyclotrons can also be used together for independent medium-energy research. When the tandem and large cyclotron are used together for heavy-ion acceleration, the injector cyclotron becomes an independent tool for low-energy nuclear chemistry or isotope production.
119193678
Trans-Planckian Issues for Inflationary Cosmology
The accelerated expansion of space during the cosmological inflation period leads to trans-Planckian issues which need to be addressed. Most importantly, the physical wavelength of fluctuations which are studied at the present time by means of cosmological observations may well originate with a wavelength smaller than the Planck length at the beginning of the inflationary phase. Thus, questions arise as to whether the usual predictions of inflationary cosmology are robust considering our ignorance of physics on trans-Planckian scales, and whether the imprints of Planck-scale physics are at the present time observable. These and other related questions are reviewed in this paper.
10194270
Trans-Planckian physics and the spectrum of fluctuations in a bouncing universe
In this paper, we calculate the spectrum of scalar field fluctuations in a bouncing, asymptotically flat Universe, and investigate the dependence of the result on changes in the physics on length scales shorter than the Planck length which are introduced via modifications of the dispersion relation. In this model, there are no ambiguities concerning the choice of the initial vacuum state. We study an example in which the final spectrum of fluctuations depends sensitively on the modifications of the dispersion relation without needing to invoke complex frequencies. Changes in the amplitude and in the spectral index are possible, in addition to modulations of the spectrum. This strengthens the conclusions of previous work in which the spectrum of cosmological perturbations in expanding inflationary cosmologies was studied, and it was found that, for dispersion relations for which the evolution is not adiabatic, the spectrum changes from the standard prediction of scale-invariance.
118876238
Green functions for topology change
We explicitly calculate the Green functions describing quantum changes of topology in Friedman-Lemaitre-Robertson-Walker universes the spacelike sections of which are compact but endowed with distinct topologies. The calculations are performed using the long wavelength approximation at second order in the gradient expansion. We argue that complex metrics are necessary in order to obtain a non-vanishing Green functions and interpret this fact as demonstrating that a quantum topology change can be viewed as a quantum tunneling effect. We demonstrate that quantum topological transitions between curved hypersurfaces are allowed whereas no transition to or from a flat section is possible, establishing thus a selection rule. We also show that the quantum topology changes in the direction of negatively curved hypersurfaces are strongly enhanced as time goes on, while transitions in the opposite direction are suppressed.
16485973
Exhaustive study of cosmic microwave background anisotropies in quintessential scenarios
Recent high-precision measurements of the CMB anisotropies performed by the BOOMERanG and MAXIMA-1 experiments provide an unmatched set of data allowing us to probe different cosmological models. Among these scenarios, motivated by the recent measurements of the luminosity distance versus redshift relation for type Ia supernovas, is the quintessence hypothesis. It consists of assuming that the acceleration of the Universe is due to a scalar field whose final evolution is insensitive to the initial conditions. Within this framework we investigate the cosmological perturbations for two well-motivated potentials: the Ratra-Peebles and the SUGRA tracking potentials. We show that the solutions of the perturbed equations possess an attractor and that, as a consequence, the insensitivity to the initial conditions is preserved at the perturbed level. Then, we study the predictions of these two models for structure formation and CMB anisotropies and investigate the general features of the multipole moments in the presence of quintessence. We also compare the CMB multipoles calculated with the help of a full Boltzmann code with the BOOMERanG and MAXIMA-1 data. We pay special attention to the location of the second peak and demonstrate that it significantly differs from the location obtained in the cosmological constant case. Finally, we argue that the SUGRA potential is compatible with all the recent data with standard values of the cosmological parameters. In particular, it fits the MAXIMA-1 data better than a cosmological constant or the Ratra-Peebles potential.
119254161
The moduli problem at the perturbative level
This paper demonstrates that existing upper bounds on the magnitude of cosmological dark matter and baryon isocurvature fluctuations can be translated into stringent constraints on the parameter space of moduli fields of supersymmetric theories, defined in terms of mσ (modulus mass) and σinf (modulus vacuum expectation value at the end of inflation). For the sake of concreteness, we assume here a quadractic modulus potential and we focus on high-scale inflationary models. These constraints are complementary to previously existing bounds from big-bang nucleosynthesis, therefore the moduli problem becomes worse at the level of cosmological perturbations. In particular, if the inflationary scale Hinf~1013 GeV, particle physics scenarios which predict high moduli masses mσ  10–100 TeV are plagued by the perturbative moduli problem, even though they evade big-bang nucleosynthesis constraints. This perturbative moduli problem is somewhat relaxed if the modulus is made heavy during inflation, with effective mass Hinf.