H.L. Ravn

Bio: H.L. Ravn is an academic researcher from CERN. The author has contributed to research in topics: Neutron & Ion source. The author has an hindex of 36, co-authored 158 publications receiving 3863 citations.

Recent progress in neutrino factory and muon collider research within the Muon Collaboration

Abstract: We describe the status of our effort to realize a first neutrino factory and the progress made in understanding the problems associated with the collection and cooling of muons towards that end. We summarize the physics that can be done with neutrino factories as well as with intense cold beams of muons. The physics potential of muon colliders is reviewed, both as Higgs factories and compact high-energy lepton colliders. The status and time scale of our research and development effort is reviewed as well as the latest designs in cooling channels including the promise of ring coolers in achieving longitudinal and transverse cooling simultaneously. We detail the efforts being made to mount an international cooling experiment to demonstrate the ionization cooling of muons.

The new CERN-ISOLDE on-line mass-separator facility at the PS-Booster

Abstract: The ISOLDE on-line isotope separators have been operated since 1967 at the CERN-SC. This 600 MeV proton synchro-cyclotron had to be shut down in December 1990 after 33 years of service and it was decided to move ISOLDE to a new experimental area. The new on-line mass-separator facility is now under construction at the CERN PS-Booster. This accelerator provides an average current of about 2-mu-A of 1 GeV protons in very short high intensity pulses at low repetition rate. The beam can hit either one of the two target stations, the general purpose separator (GPS), a reconstructed ISOLDE-2 type machine (which can deliver beams simultaneously into three beam lines), and the high resolution separator (HRS), which is essentially the slightly modified ISOLDE-3 separator. The central GPS beam line and the HRS feed a common beam transport system to which most of the experiments will be connected. The new facility will be taken into operation in spring 1992.

Discovery of Radioactive Decay of Ra 222 and Ra 224 by C 14 Emission

Abstract: Using the ISOLDE on-line isotope separator at CERN to produce sources of $^{221}\mathrm{Fr}$, $^{221}\mathrm{Ra}$, $^{222}\mathrm{Ra}$, $^{223}\mathrm{Ra}$, and $^{224}\mathrm{Ra}$, and using polycarbonate track-recording films sensitive to energetic carbon nuclei but not to alpha particles, we have discovered two new cases of the rare $^{14}\mathrm{C}$ decay mode---in $^{222}\mathrm{Ra}$ and $^{224}\mathrm{Ra}$. Our results for branching ratios, $B$, relative to alpha decay are for $^{221}\mathrm{Fr}$ and $^{221}\mathrm{Ra}$, $Bl4.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$; for $^{222}\mathrm{Ra}$, $B=(3.7\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$; for $^{223}\mathrm{Ra}$, $B=(6.1\ifmmode\pm\else\textpm\fi{}1.0)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$; for $^{224}\mathrm{Ra}$, $B=(4.3\ifmmode\pm\else\textpm\fi{}1.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$.

Beta decay of the new isotopes K 52 , Ca 52 , and Sc 52 ; a test of the shell model far from stability

Abstract: The nuclides $^{52}\mathrm{K}$, $^{52}\mathrm{Ca}$, and $^{52}\mathrm{Sc}$ have been produced by fragmentation of a uranium target with a 600 MeV proton beam The subsequent \ensuremath{\beta} decays to the daughter nuclei $^{52}\mathrm{Ca}$, $^{52}\mathrm{Sc}$, and $^{52}\mathrm{Ti}$ have been studied by neutron and \ensuremath{\gamma} spectroscopy on sources obtained from on-line mass separation \ensuremath{\beta} decay energies have been determined by \ensuremath{\beta}-\ensuremath{\gamma} coincidence spectroscopy In addition to the short half-life of $^{52}\mathrm{K}$ (${T}_{1/2}$=110\ifmmode\pm\else\textpm\fi{}30 ms), we attributed two different half-lives (${T}_{1/2}$=46\ifmmode\pm\else\textpm\fi{}03 s and ${T}_{1/2}$=82\ifmmode\pm\else\textpm\fi{}02 s) to $^{52}\mathrm{Ca}$ and $^{52}\mathrm{Sc}$, respectively A decay scheme has been established for $^{52}\mathrm{K}$ involving five \ensuremath{\beta} branches to delayed neutron emitting states between 66 and 103 MeV and one \ensuremath{\beta} branch to a bound level at ${E}_{x}$=256 MeV The $^{52}\mathrm{Ca}$ decay scheme accounts for \ensuremath{\beta} branches to four levels at 164, 275, 346, and 427 MeV for which the deduced logft values restrict the angular momentum and parity to ${J}^{\ensuremath{\pi}}$${=1}^{+}$ For the $^{52}\mathrm{Sc}$ ground state, strong \ensuremath{\beta} transitions to the ${2}^{+}$ (105 MeV) and the (${4}^{+}$) (232 MeV) levels in $^{52}\mathrm{Ti}$ strongly favor a ${J}^{\ensuremath{\pi}}$${=3}^{+}$ attribution The measured ${Q}_{\ensuremath{\beta}}$ values for the $^{52}\mathrm{Ca}$ (57\ifmmode\pm\else\textpm\fi{}02 MeV) and $^{52}\mathrm{Sc}$ (802\ifmmode\pm\else\textpm\fi{}025 MeV) decay are noticeably lower than expected from mass systematics The energy level diagrams of $^{52}\mathrm{Ca}$, $^{52}\mathrm{Sc}$, and $^{52}\mathrm{Ti}$ nuclei have been calculated in the framework of the shell model with a realistic interaction Good agreement between theory and experiment is achieved as well for excitation energies as for mass excesses, assuring then the applicability of the theory to this region of nuclei far from stability

Decay of Neutron-Rich Mn Nuclides and Deformation of Heavy Fe Isotopes

Abstract: The use of chemically selective laser ionization combined with $\ensuremath{\beta}$-delayed neutron counting at CERN/ISOLDE has permitted identification and half-life measurements for 623-ms ${}^{61}\mathrm{Mn}$ up through 14-ms ${}^{69}\mathrm{Mn}$. The measured half-lives are found to be significantly longer near $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}40$ than the values calculated with a quasiparticle random-phase-approximation shell model. Gamma-ray singles and coincidence spectroscopy has been performed for ${}^{64,66}\mathrm{Mn}$ decays to levels of ${}^{64,66}\mathrm{Fe}$, revealing a significant drop in the energy of the first ${2}^{+}$ state in these nuclides that suggests an unanticipated increase in collectivity near $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}40$.

Self-consistent mean-field models for nuclear structure

Abstract: The authors review the present status of self-consistent mean-field (SCMF) models for describing nuclear structure and low-energy dynamics. These models are presented as effective energy-density functionals. The three most widely used variants of SCMF's based on a Skyrme energy functional, a Gogny force, and a relativistic mean-field Lagrangian are considered side by side. The crucial role of the treatment of pairing correlations is pointed out in each case. The authors discuss other related nuclear structure models and present several extensions beyond the mean-field model which are currently used. Phenomenological adjustment of the model parameters is discussed in detail. The performance quality of the SCMF model is demonstrated for a broad range of typical applications.

Quantum electrodynamics

Abstract: THE subject of quantum electrodynamics is extremely difficult, even for the case of a single electron. The usual method of solving the corresponding wave equation leads to divergent integrals. To avoid these, Prof. P. A. M. Dirac* uses the method of redundant variables. This does not abolish the difficulty, but presents it in a new form, which may be dealt with in two ways. The first of these needs only comparatively simple mathematics and is directly connected with an elegant general scheme, but unfortunately its wave functions apply only to a hypothetical world and so its physical interpretation is indirect. The second way has the advantage of a direct physical interpretation, but the mathematics is so complicated that it has not yet been solved even for what appears to be the simplest possible case. Both methods seem worth further study, failing the discovery of a third which would combine the advantages of both.