95557368
A PROPOSED NATIONAL HEAVY-ION ACCELERATOR AT OAK RIDGE*
The proposed National Heavy‐ion Laboratory will be provided with a multi‐stage accelerator system integrated with the existing Oak Ridge Isochronous Cyclotron (ORIC) facilities. The main accelerator stage is to be a four‐sector isochronous cyclotron that will provide beam energies up to 100 MeV/u. Ions may be injected into the large cyclotron from either a 20 MV tandem electrostatic accelerator or from the ORIC. The ion energies range from 100 MeV/u for oxygen to 10 MeV/u for uranium. Maximum beam intensities range from ∼ 1013 particles/second for oxygen to 2 × 1012 particles/second for uranium. The sector magnet angle for the cyclotron is 52° which yields radial and axial focusing frequencies of νr = 1.1 – 1.2 and νz = 0.6 – 0.8. The field‐radius product of the magnet is 3018 kG‐cm at a maximum magnetic field of 16 kG. The rf system is tunable over the range 6 – 14 MHz to accommodate acceleration on harmonics 2 – 11. Second harmonic resonators are provided to increase the phase acceptance and/or the energy resolution.The proposed National Heavy‐ion Laboratory will be provided with a multi‐stage accelerator system integrated with the existing Oak Ridge Isochronous Cyclotron (ORIC) facilities. The main accelerator stage is to be a four‐sector isochronous cyclotron that will provide beam energies up to 100 MeV/u. Ions may be injected into the large cyclotron from either a 20 MV tandem electrostatic accelerator or from the ORIC. The ion energies range from 100 MeV/u for oxygen to 10 MeV/u for uranium. Maximum beam intensities range from ∼ 1013 particles/second for oxygen to 2 × 1012 particles/second for uranium. The sector magnet angle for the cyclotron is 52° which yields radial and axial focusing frequencies of νr = 1.1 – 1.2 and νz = 0.6 – 0.8. The field‐radius product of the magnet is 3018 kG‐cm at a maximum magnetic field of 16 kG. The rf system is tunable over the range 6 – 14 MHz to accommodate acceleration on harmonics 2 – 11. Second harmonic resonators are provided to increase the phase acceptance and/or the ener...
115550416
RECENT PROGRESS ON A SUPERCURRENT SEPARATED ORBIT CYCLOTRON.
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.
122110697
The Holifield Heavy Ion Research Facility
The Holifield Heavy Ion Research Facility has been in routine operation since July 1982. Beams have been provided using both the tandem accelerator alone and a coupled mode in which the Oak Ridge Isochronous Cyclotron is used as an energy booster for tandem beams. The coupled mode has proved to be especially effective and has allowed us to provide a wide range of energetic beams for scheduled experiments. In this report we discuss our operational experience and recent development activities.
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.
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.
7636464
On compatibility of the Kaluza-Klein approach with the COBE experiment
Contributions of primordial gravitational waves to the large-angular-scale anisotropies of the cosmic microwave background radiation in multidimensional cosmological models (Kaluza-Klein models) are studied. We derive limits on free parameters of the models using results of the COBE experiment and other astrophysical data. It is shown that in principle there is a room for Kaluza-Klein models as possible candidates for the description of the Early Universe. However, the obtained limits are very restrictive. Assuming that the anisotropies are mostly due to gravitational waves, none of the concrete models, analyzed in the article, satisfy them. On the other hand, if the contribution of gravitational waves is very small then a string inspired model is not ruled out.
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.
56354581
First CMB Constraints on the Inflationary Reheating Temperature
We present the first Bayesian constraints on the single field inflationary reheating era obtained from cosmic microwave background (CMB) data. After demonstrating that this epoch can be fully characterized by the so-called reheating parameter, we show that it is constrained by the seven years Wilkinson microwave anisotropies probe (WMAP7) data for all large and small field models. An interesting feature of our approach is that it yields lower bounds on the reheating temperature which can be combined with the upper bounds associated with gravitinos production. For large field models, we find the energy scale of reheating to be higher than those probed at the Large Hadron Collider, rho(1/4)(reh) > 17.3 TeV at 95% of the confidence limit. For small field models, we obtain the two-sigma lower limits rho(1/4)(reh) > 890 TeV for a mean equation of state during reheating (w) over bar (reh) = -0.3 and rho(1/4)(reh) > 390 GeV for (w) over bar (reh) = -0.2. The physical origin of these constraints is pedagogically explained by means of the slow-roll approximation. Finally, when marginalizing over all possible reheating history, the WMAP7 data push massive inflation under pressure (p < 2.2 at 95% of the confidence limit where p is the power index of the large field potentials) while they slightly favor super-Planckian field expectation values in the small field models.
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.
15719493
PROPAGATING COSMOLOGICAL PERTURBATIONS IN A BOUNCING UNIVERSE
Using the simplest model for a bouncing universe, namely that for which gravity is described by pure general relativity, the spatial sections are positively curved and the matter content is a single scalar field, we obtain the transition matrix relating cosmological perturbation modes between the contracting and expanding phases. We show that this case provides a specific example in which this relation explicitely depends on the perturbation scale whenever the null energy condition (NEC) is close to be violated.