Extremely cold positrons for antihydrogen production

The storage of extremely cold (4 K) antiprotons in a Penning trap is an important step toward the creation and study of cold antihydrogen. The other required ingredient, the largest possible number of comparably cold positrons, is still lacking. These would be recombined in a high vacuum with the trapped antiprotons, already stored at a pressure below 5×10⁻¹⁷ Torr, thereby avoiding annihilation of the antihydrogen atoms before they can be used in high accuracy measurements or in controlled collision experiments. In an exploratory experiment, positrons from a 18 mCi²²Na source follow fringing field lines of a 6 T superconducting solenoid through tiny apertures in the electrodes of a Penning trap to strike a tungsten (reflection) moderator. The positron beam is chopped mechanically and a lock-in directly detects a positron current of 2.5×10⁶e⁺/s on the moderator. The use of a moderator, unlike an earlier experiment in which < 100 positrons were confined in vacuum, should greatly increase the number of positrons trapped in high vacuum.     

Bestimmung von Brom und Silber in metallorganischen Komplexen durch potentiometrische Titration

Zusammenfassung Nach Zersetzung des Komplexes wird das gebildete unlösliche Silberbromid mit metallischem Zink zu festem Silber und gelösten Bromidionen umgesetzt. Beide Komponenten werden potentiometrisch titriert. Die Standardabweichung beträgt 0,5 bzw. 1%.Teil eines Vortrags anläßlich der Tagung Euroanalysis I, 28. 8.–1.9. 1972 in Heidelberg.     

The preparation and operation of electrodeless discharge lamps—a critical review

In this paper the literature on electrodeless discharge lamps (EDLs) is reviewed. Several aspects of preparation and operation of EDLs are critically discussed. Attention is also paid to multi-element EDLs and comparisons of EDL's with other light sources. The authors feel that the present situation must be characterized by the conclusion that really concrete and general conclusions cannot be drawn from the literature.     

Trapping positrons for low energy antihydrogen production

A method of trapping large numbers of positrons at liquid helium temperatures in a 6 Tesla magnetic field is described. Positrons from a sodium-22 source are moderated to low energies with a tungsten reflection moderator. A Penning trap with hyperbolic electrodes holds the positrons in a magnetron (EXB) orbit. The positrons are then cooled via coupling to a tuned circuit that is in resonance with the axial oscillation of the positrons. At this point, many slow positrons are permanently trapped in the Penning trap. The positrons are centered in the trap by applying a radio-frequency field at a frequency near the sum of the axial and magnetron frequencies. This method promises to produce 10⁶ trapped positrons at a density of 10⁷ to 10⁸ per cm³. Such densities of positrons would be useful in producing antihydrogen in combination with existing antiproton plasmas.     

Trapped positrons for antihydrogen

Positrons from a 12 mCi²²Na source are slowed by a W(110) reflection moderator and then captured in a Penning trap, by damping their motion with a tuned circuit. Because of the stability of the Penning trap and the cryogenic ultra-high vacuum environment, we anticipate that positrons can be accumulated and stored indefinitely. A continuous loading rate of 0.14 e⁺/s is observed for 32 h in this initial demonstration. More than 1.6×10⁴ positrons have thus been trapped and stored at 4 K, with improvements expected. The extremely high vacuum is required for compatibility with an existing antiproton trap, which has already held more than 10⁵ antiprotons at 4 K, for producing antihydrogen at low temperatures. The extremely cold positrons in high vacuum may also prove to be useful for cooling highly stripped ions.     

Study of structural and electronic transport properties of Ce-doped LaMnO3

The structural and electronic transport properties of La_1−x Ce _x MnO₃ (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration up to 50% doping. The system La_0.5Ce_0.5MnO₃ also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition.