120950815
A 10-GeV on 10-GeV heavy-ion collider
115477044
Magnet Model Studies for Separated-Sector Heavy Ion Cyclotrons
A four-sector model of a 2400 ton (2200 metric ton), K=440, separated-sector cyclotron magnet has been built to 0.15 scale. The sector angle of the magnet is 52°. Magnetic field measurements have been made using a single Hall-effect element that was positioned by a high-precision numerically controlled table. Magnetic field data and the ion focusing characteristics are presented.
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.
115550416
RECENT PROGRESS ON A SUPERCURRENT SEPARATED ORBIT CYCLOTRON.
119279784
Collapse of small-scale density perturbations during preheating in single field inflation
After cosmic inflation and before the transition to radiation domination, the cosmic energy density may have been dominated during an extended period by an oscillating massive scalar condensate. We show that during this period, sub-Hubble scale perturbations are subject to a metric preheating instability in the narrow resonance regime. We analyze in detail both, quadratic and quartic potentials. The instability leads to the growth of density perturbations which in many cases become non-linear already before the beginning of a radiation dominated Universe. This is particularly the case when requiring a phenomenologically preferred low reheat temperature. These early structures may lead to the emission of gravitational waves and the production of primordial black holes.
119240885
Constraints on moduli cosmology from the production of dark matter and baryon isocurvature fluctuations
We set constraints on moduli cosmology from the production of dark matter—radiation and baryon— radiation isocurvature fluctuations through modulus decay, assuming the modulus remains light during inflation. We find that the moduli problem becomes worse at the perturbative level as a significant part of the parameter space m σ (modulus mass)—σ inf (modulus vacuum expectation value at the end of inflation) is constrained by the nonobservation of significant isocurvature fluctuations. We discuss in detail the evolution of the modulus vacuum expectation value and perturbations, in particular, the consequences of Hubble scale corrections to the modulus potential, and the stochastic motion of the modulus during inflation. We show, in particular, that a high modulus mass scale m σ ≳ 100 TeV, which allows the modulus to evade big bang nucleosynthesis constraints is strongly constrained at the perturbative level. We find that generically, solving the moduli problem requires the inflationary scale to be much smaller than 10 13 GeV.
119272244
Ultra Slow-Roll Inflation and the non-Gaussianity Consistency Relation
Ultra slow-roll inflation has recently been used to challenge the non-Gaussianity consistency relation. We show that this inflationary scenario belongs to a one parameter class of models and we study its properties and observational predictions. We demonstrate that the power spectrum remains scale-invariant and that the bi-spectrum is of the local type with fnl=5(3-ns)/4 which, indeed, represents a modification of the consistency relation. However, we also show that the system is unstable and suffers from many physical problems among which is the difficulty to correctly WMAP normalize the model. We conclude that ultra slow-roll inflation remains a very peculiar case, the physical relevance of which is probably not sufficient to call into question the validity of the consistency relation.
86861114
Nonvacuum initial states for cosmological perturbations of quantum mechanical origin
In the context of inflation, non-vacuum initial states for cosmological perturbations that possess a built in scale are studied. It is demonstrated that this assumption leads to a falsifiable class of models. The question of whether they lead to conflicts with the available observations is addressed. For this purpose, the power spectrum of the Bardeen potential operator is calculated and compared with the CMBR anisotropies measurements and the redshift surveys of galaxies and clusters of galaxies. Generic predictions of the model are: a high first acoustic peak, the presence of a bump in the matter power spectrum and non-Gaussian statistics. The details are controlled by the number of quanta in the non-vacuum initial state. Comparisons with observations show that there exists a window for the free parameters such that good agreement between the data and the theoretical predictions is possible. However, in the case where the initial state is a state with a fixed number of quanta, it is shown that this number cannot be greater than a few. On the other hand, if the initial state is a quantum superposition, then a larger class of initial states could account for the observations, even though the state cannot be too different from the vacuum. Planned missions such as the MAP and Planck satellites and the Sloan Survey, will demonstrate whether the new class of models proposed here represents a viable alternative to the standard theory.
118719996
The Quantum State of Inflationary Perturbations
This article reviews the properties of the quantum state of inflationary perturbations. After a brief description of the inflationary background, the wavefunction of the Mukhanov-Sasaki variable is calculated and shown to be that of a strongly squeezed state. The corresponding Wigner function and density matrix, which are convenient tools to characterize the properties of a quantum state, are also evaluated. Finally, the issue of definite outcomes for inflation is discussed.