Electromagnetic Trap Research Articles

How to make antimatter last

An experiment at CERN has shown that antiprotons can be kept for several minutes in an electromagnetic trap. But the prospect of making reality of the science fiction remains remote.

Electromagnetic Trapping of Neutral Atoms

Electromagnetic trapping of neutral atoms is a new branch of applied physics that has potential for use in very many areas, including metrology and high-resolution precision spectroscopy. It has the possibility of leading toward the spectroscopic ideal of an isolated atom at rest, available for interaction with electromagnetic field probes. We present an introduction to trapping in both dc magnetic fields and optical fields (laser beams). The basic ideas and fundamental limitations are discussed and the first successful experiments are reviewed.

Laser cooling and electromagnetic trapping of neutral atoms

Atoms in a thermal beam can be cooled, decelerated, and stopped using the radiation pressure from a nearly resonant laser beam. Several groups have already used this laser-cooling process on an atomic sodium beam. The techniques and results of the various experimental groups are reviewed, and applications of laser-cooled atoms, in particular the possibility of confining them in electromagnetic traps, are discussed.

Lumino-réfrigération

In a paper of 1950, Alfred Kastler proposed cooling of vapours by resonant light via optical pumping of the orientational levels of angular momentum, and successive collisions. Optical pumping of the degrees of freedom of the translational momentum is also feasible. This phenomenon has been demonstrated with ions, even with a single ion, in an electrodynamic or electromagnetic trap. Optical cooling by Raman-like two-photon transitions seems to be capable of generating ultra-low temperature levels.

Absorption of electromagnetic waves in the plasma resonance region in an electromagnetic trap

The authors consider the absorption of electromagnetic waves incident on the plasma surface in an electromagnetic trap. The electromagnetic waves are transformed in the plasma resonance region in the transition layer between the plasma and the magnetic field into Langmuir oscillations travelling in this layer towards decreasing densities. The absorption coefficient for waves of frequencies of the order of (but lower than) the maximum Langmuir frequency is of the order of unity. This ensures, in the presence of a metal chamber, effective absorption of the entire super-high-frequency power supplied.

Plasma Production, Losses, and Electron Temperature Measurements in the KEMP II B Electromagnetic Trap

Plasmas with densities approaching 1012 cm-3 have been produced in a spindle-cusp electromagnetic trap by electron beam injection. The plasma density seems to be limited by the input beam power. A neutral plasma is found to exist in the inner electrode regions. The electron temperature is about 30 eV, and the particle confinement times are about 100 4317360s. The loss of plasma electrons is dominated by cross field diffusion to the grounded electrodes which determine the plasma boundary. The confinement time is in rough agreement with calculations based upon classical diffusion via electron-neutral collisions.

A new measurement of the neutron lifetime

We have measured the mean lifetime τ of the free neutron by counting decay protons stored in an electromagnetic trap. Neutron density determination was by activation of calibrated boron foils. The result, based on five independent measurements for various experimental conditions, is τ = 937 ± 18 s.

L'équilibre Vlasov dans la machine KEMP II avec limites réalistes d'énergie et de moment des particules du plasma

Plasma equilibria have been calculated numerically for the electromagnetic trap, KEMP II, from the Vlasov and Poisson equations. A plausible form for the electron and deuterium ion velocity distribution functions has been assumed. Compared with the previous work of Brunel Lafrance, Burkhardt, and Gregory, the present work provides a more realistic treatment of the limits of integration in the expressions for the moments of the distribution functions in order to allow for energy and momentum values permitting the charged particles to escape the machine or encounter a material electrode. The parameters in the theory have been varied around reasonable estimates provided by experiments so that their influence on the equilibria could be studied. The densities predicted by our calculations are one to two orders of magnitude smaller than experimental estimates. We postulate that this difference is explained by the fact that our theory does not take into account electrons reflected by the classical mirror effect in the cusp regions of the KEMP II machine, thus preventing them from shielding the anode potential.

Measurement of the depth of the potential well in an electro-magnetic trap by a beam of neutral particles. (USSR)

Measurement of the depth of the potential well in an electro-magnetic trap by a beam of neutral particles. (USSR)

Density and lifetime measurements in the KEMP II electromagnetic trap

The temporal evolution of the electron density in a repetitively-pulsed electromagnetic trap has been measured. The plasma is produced by ionization of a background gas by a pulsed electron beam. The plasma density is measured by a microwave interferometer (8 GHz), and the particle lifetime by the density decay after the interruption of the beam pulse. These measurements show that reasonably dense plasmas (~4 × 1011 cm−3 cm−3) can be confined for the order of a millisecond. Apparently the effect of residual ionization becomes important in the decay phase, due to the high electron energies (~2000 eV).

ELECTRIC‐MAGNETIC CONFINEMENT

The theoretical plasma confinement times for an electromagnetic trap, which is an electrostatically plugged magnetic cusp device, are calculated. The plasma may be produced by electron beam injection or by other methods. Electron losses along field lines are inhibited by negative electrodes (cathodes) placed at the cusp openings. The main electron losses are then by diffusion in velocity space over the potential barrier and by collisional diffusion across the magnetic field. After a few ions are lost, the excess negative charge of the plasma creates a negative potential well in which the remaining ions are electrostatically trapped. (MOW)

Principles of the stored ion calorimeter

The properties of a harmonically bound radiatively thermalized ion gas were investigated by studying the behavior of an electron cloud stored in a Penning trap. A simple model characterizing ions contained in an electromagnetic trap is proposed and tested by investigating the electromagnetic−dynamic behavior of these electrons subject to various external perturbations. The ion calorimeter realized in such a system is also discussed; particular attention is devoted to sensitivity to heat inputs into the various degrees of freedom.

Investigation and test of the magnetic system of the Jupiter-1M electromagnetic trap

Investigation and test of the magnetic system of the Jupiter-1M electromagnetic trap

Plasma losses in the ring gap of an electromagnetic trap

The effect of diocotron instability on plasma losses in the ring slit of an electromagnetic trap was examined. It was found that the instability growth disturbs the initial symmetry of the electron layer in the ring slit. Secondary plasma generated by ionization of residual gas in the trap increases the instability growth rate. The instability can be suppressed by shorting one of the surface

Plasma accumulation through ionization of residual gas in an electromagnetic trap

Plasma accumulation through ionization of residual gas in an electromagnetic trap

Radiative Lifetime of Metastable Li II2S01

The radiative lifetime of Li II $2^{1}S_{0}$ has been measured by counting decay photons versus time from an ensemble of metastable Li ions stored in a simple electromagnetic trap of the Penning variety. The result is ${\ensuremath{\tau}}_{\mathrm{expt}}=503(26)$ \ensuremath{\mu}sec. The error represents one standard deviation from the mean of a series of 34 separate determinations. This result is in agreement with the theoretical value ${\ensuremath{\tau}}_{\mathrm{th}}=513$ \ensuremath{\mu}sec.

Two-stream instability in the magnetic slit of an electromagnetic trap

Two-stream instability in the magnetic slit of an electromagnetic trap