Search results for "plasma physics"
showing 10 items of 393 documents
Studies of Weak Beta-Delayed Protons Emitted in the Decay of Odd-Z, Tz = -3/2 Nuclei
1983
Radioactive decay of Tz = - 3/2 nuclides, 27P and 31Cl, predicted to be weak β-delayed proton precursors, have been looked for. Two proton groups having energies of 989 ± 15 and 1528 ± 20 keV and a half-life of 150 ± 25 ms were associated with the decay of 31Cl. The search for 27P is still under way, but the first qualitative results are briefly discussed.
The beta-, neutrino- and proton-asymmetry in neutron beta-decay
2004
This article describes measurements of angular-correlation coefficients in the decay of free neutrons with the superconducting spectrometer PERKEO II. A method for measuring the β-asymmetry coefficient A is presented, as well as a new method for determining the neutrino-asymmetry coefficient B, which allows a value for the proton-asymmetry coefficient C to be obtained for the first time. An ongoing experiment is trying to improve the accuracy of these quantities.
Dynamics of an unbalanced two-ion crystal in a Penning trap for application in optical mass spectrometry
2019
In this article, the dynamics of an unbalanced two-ion crystal comprising the 'target' and the 'sensor' ions confined in a Penning trap has been studied. First, the low amplitude regime is addressed. In this regime, the overall potential including the Coulomb repulsion between the ions can be considered harmonic and the axial, magnetron and reduced-cyclotron modes split up into the so-called 'stretch' and 'common' modes, that are generalizations of the well-known 'breathing' and 'center-of-mass' motions of a balanced crystal made of two ions. By measuring the frequency modes of the crystal and the sensor ion eigenfrequencies using optical detection, it will be possible to determine the targ…
A simple method for counting the number of trapped ions in an ion trap
1996
The number of stored Ca\(^+\) ions in an ion trap was measured optically by utilizing the metastable states. All the ions trapped are first pumped into the metastable \(D\) states. The ions in the metastable \(D\) states are transferred to the ground \(S\) state via the \(P\) state by exciting a \(D\rightarrow P\) transition. Each ion then emits one photon through a subsequent \(P\rightarrow S\) spontaneous emission. Thus, the number of photons is the same as the number of trapped ions initially in the metastable states. When a fraction of all the stored ions are pumped into the metastable states, the method is still applicable if the fraction of the ions is known.
High Cyclotron Harmonics Excitation in Multi-beam Terahertz Range Gyrotrons
2019
The paper presents recent results on the multi-beam gyrotrons operating at cyclotron harmonics in terahertz frequency range. The theoretical and experimental investigation of second harmonic 0.78 THz gyrotron includes comparison of generating and absorbing beam schemes, research on the effect of velocity spread and mode competition process, along with development of third harmonic 1.2 THz tube based on verified numerical codes and latest experimental results.
Spatial separation of atomic states in a laser-cooled ion crystal
1998
A laser cooled ion crystal containing several hundred Ca+ ions has been stored in a linear Paul trap. Cooling is provided by a red detund laser at the 4S1/2−4P1/2 resonance transition. A second laser serves for repumping of those ions which decay from the excited 4P1/2 level to the metastable 3D3/2 state. The ions can be additionally excited by a third laser to a long lived metastable 3D5/2 energy level which decouples them from the cooling laser radiation. The light pressure acting upon the laser cooled ions pushes them into the direction of the laser beam. The ions in the metastable 3D5/2 state, however, do not experience any light pressure force and diffuse to the crystal side which poin…
First imaging of corotating interaction regions using the STEREO spacecraft
2008
Plasma parcels are observed propagating from the Sun out to the large coronal heights monitored by the Heliospheric Imagers (HI) instruments onboard the NASA STEREO spacecraft during September 2007. The source region of these out-flowing parcels is found to corotate with the Sun and to be rooted near the western boundary of an equatorial coronal hole. These plasma enhancements evolve during their propagation through the HI cameras' fields of view and only becoming fully developed in the outer camera field of view. We provide evidence that HI is observing the formation of a Corotating Interaction Region (CIR) where fast solar wind from the equatorial coronal hole is interacting with the slow…
Enhancing the sensitivity of recoil-beta tagging
2013
Tagging with β-particles at the focal plane of a recoil separator has been shown to be an effective technique for the study of exotic proton-rich nuclei. This article describes three new pieces of apparatus used to greatly improve the sensitivity of the recoil-beta tagging technique. These include a highly-pixelated double-sided silicon strip detector, a plastic phoswich detector for discriminating high-energy β-particles, and a charged-particle veto box. The performance of these new detectors is described and characterised, and the resulting improvements are discussed.
Laser cooling of externally produced Mg ions in a Penning trap for sympathetic cooling of highly charged ions
2012
We have performed laser cooling of Mg ions confined in a Penning trap. The externally produced ions were captured in flight, stored and laser cooled. Laser-induced fluorescence was observed perpendicular to the cooling laser axis. Optical detection down to the single ion level together with electronic detection of the ion oscillations inside the Penning trap have been used to acquire information on the ion storage time, ion number and ion temperature. Evidence for formation of ion crystals has been observed. These investigations are an important prerequisite for sympathetic cooling of simultaneously stored highly-charged ions and precision laser spectroscopy of forbidden transitions in thes…
Stability of gyrotron operation in very high-order modes
2012
This study was motivated by the desire to increase the power, which can be delivered by gyrotrons in long pulse and continuous regimes. Since the admissible power level is determined by the density of ohmic losses in resonator walls, to increase the radiated power a gyrotron should operate in higher order modes. Using an existing gyrotron developed for plasma experiments in the International Thermonuclear Experimental Reactor as a base model, the stability of operation of such a gyrotron in modes with larger number of radial variations was studied. It is shown that the power level achievable in such gyrotrons in stable single mode regimes is close to 1.5 MW. The power level 1.7–1.8 MW can b…