37428412
Coupled Operation of the Oak Ridge Isochronous Cyclotron and the 25 MV Tandem
Coupled operation of the 25 MV tandem and the Oak Ridge Isochronous Cyclotron (ORIC) was achieved on January 27, 1981. A beam of 38 MeV 16O2+ was injected into ORIC, stripped to 8+ and accelerated to 324 MeV. Shortly afterwards, the energy was increased to the maximum design value of 25 MeV/amu (400 MeV). A spectrum taken of the scattering of this beam from a thin 208Pb target in the broad range spectrograph exhibited a resolution of 115 keV (FWHM). Performance of the system was in close agreement with that predicted from calculations.
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.
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.
125516191
Alternates to the cyclotron for heavy-ion acceleration.
The status and future possibilities for several alternates to the cyclotron for heavy‐ion acceleration are discussed. Linear accelerators, both conventional and superconducting, tandem electrostatic accelerators, and the electron ring accelerator are among the accelerator types and concepts reviewed and compared.
115293095
TRENDS IN THE UNITED STATES FOR THE ACCELERATION OF HEAVY IONS.
115550416
RECENT PROGRESS ON A SUPERCURRENT SEPARATED ORBIT CYCLOTRON.
18165833
Generation of large scale magnetic fields in single-field inflation
We consider the generation of large scale magnetic fields in slow-roll inflation. The inflaton field is described in a supergravity framework where the conformal invariance of the electromagnetic field is generically and naturally broken. For each class of inflationary scenarios, we determine the functional dependence of the gauge coupling that is consistent with the observations on the magnetic field strength at various astrophysical scales and, at the same time, avoid a back-reaction problem. Then, we study whether the required coupling functions can naturally emerge in well motivated, possibly string inspired, models. We argue that this is non-trivial and can be realized only for a restricted class of scenarios. This includes power-law inflation where the inflaton field is interpreted as a modulus. However, this scenario seems to be consistent only if the energy scale of inflation is low and the reheating stage prolonged. Another reasonable possibility appears to be small field models since no back-reaction problem is present in this case but, unfortunately, the corresponding scenario cannot be justified in a stringy framework. Finally, large field models do not lead to sensible model building.
34047731
Testing for w < -1 in the solar system.
In scalar-tensor theories of gravity, the equation of state of dark energy, w, can become smaller than -1 without violating any energy condition. The value of w today is tied to the level of deviations from general relativity which, in turn, is constrained by solar system and pulsars timing experiments. The conditions on these local constraints for w to be significantly less than -1 are established. It is demonstrated that this requires us to consider theories that differ from the Jordan-Fierz-Brans-Dicke theory and that involve either a steep coupling function or a steep potential. It is also shown how a robust measurement of w could probe scalar-tensor theories.
54573190
On the dependence of the spectra of fluctuations in inflationary cosmology on transPlanckian physics
We calculate the power spectrum of metric fluctuations in inflationary cosmology starting with initial conditions which are imposed mode by mode when the wavelength equals some critical length $\ell_{_{\rm C}}$ corresponding to a new energy scale $M_{_{\rm C}}$ at which trans-Planckian physics becomes important. In this case, the power spectrum can differ from what is calculated in the usual framework (which amounts to choosing the adiabatic vacuum state). The fractional difference in the results depends on the ratio $\sigma_0$ between the Hubble expansion rate $H_{\rm inf}$ during inflation and the new energy scale $M_{_{\rm C}}$. We show how and why different choices of the initial vacuum state (stemming from different assumptions about trans-Planckian physics) lead to fractional differences which depend on different powers of $\sigma_0$. As we emphasize, the power in general also depends on whether one is calculating the power spectrum of density fluctuations or of gravitational waves.
9779556
QUINTESSENCE: A MINI-REVIEW
Models where the accelerated expansion of our Universe is caused by a quintessence scalar field are reviewed. In the framework of high energy physics, the physical nature of this field is discussed and its interaction with ordinary matter is studied and explicitly calculated. It is shown that this coupling is generically too strong to be compatible with local tests of gravity. A possible way out, the chameleon effect, is also briefly investigated.
119068498
Reply to "Bouncing Universes and their perturbations: remarks on a toy model"
In this web note, we reply to a recent paper, gr-qc/0404126, confirming a previous work of ours in which a cosmological bouncing phase was shown to have the ability of modifying the spectrum of primordial perturbations (PRD 68, 103517 2003), but challenging its physical conditions of validity. Explicitly, Ref. gr-qc/0404126, besides pretending our Taylor series expansion of the scale factor close to the bounce amounts to choosing a family of polynomial scale factors, also claims that the bounce affects the spectrum only if the mass scale of the scalar field driving the dynamics is of the order of the Planck mass. We show that these objections are either misleading or incorrect since the minimum size of the Universe a_0 (value of the scale factor at the bounce) is either not physically specified, as required in a closed Universe, or implicitly assumed to be the Planck mass. We calculate this mass and obtain that, unsurprisingly, for a reasonable value of a_0, i.e. much larger than the Planck length, the scalar field mass is smaller than the Planck mass.