0000000000522565
AUTHOR
G. Gräff
Intense source of slow positrons from pulsed electron accelerators
A pulsed LINAC is used for pair production in a tantalum target of 2.5 radiation lengths in an energy range from 80 to 260 MeV. Several well-annealed tungsten vanes are placed immediately behind the target and thermalize a small fraction of the fast positrons. The slow positrons are extracted from the target region and magnetically guided over a distance of 17 m to the detector at the end of an S-shaped solenoid. Two Nal detectors with well-known detection efficiency are used to register the 511 keV annihilationγ-rays. To reduce pile-up effects 50 mm of Pb were placed in front of the detectors. At an average electron current of 1 μA we could detect about 107 slow positrons per second. The p…
On the observability of parity and time reversal violating interactions by trapped ion spectroscopy
The feasibility to measure neutral weak current interactions by spectroscopy on trapped ions is investigated. The sensitivity of the proposed experiment is compared to the sensitivity of similar experiments using atomic gases or beams. It is shown that there is no advantage as far as that part of the interaction is concerned which is a vector in the nucleon current and an axial vector in the electron current. This is mainly due to the relatively low ion density. The circular polarization however depending upon the nuclear spin orientation appears to be proportional to the coherence time, which is three orders of magnitude longer than in ordinary atomic beam resonance experiments. It is poin…
A direct determination of the proton electron mass ratio
The cyclotron frequencies of free protons and electrons in a magnetic field of 5.81 Tesla with superimposed electrostatic quadrupole field have been measured. The increase of energy connected with a transition at cyclotron frequency is detected by the measurement of the time of flight through an inhomogeneous magnetic field. From the ratio of the measured cyclotron frequencies of both particles the proton electron mass ratio is deduced. The resultm p /m e =1,836.1527(11) agrees within the limits of error (0.6 ppm) with the value of the indirect determination.
Precision Determination of Cyclotron Frequencies of Free Electrons and Ions
Within the last two decades the electrodynamical storage of electrons and ions developed into an experimental method of great versatility. That this method is now being used in so many different fields of physics and chemistry results primarily from the long storage times which nowadays can be achieved. Under ultrahigh vacuum conditions and in sufficiently strong electromagnetic fields the particles can easily be trapped for hours or even days. This really long storage time offers the possibility of studying reactions of very slow rate to the chemist and of precision measurement of photon-ion interactions to the physicist. The accuracy of photon-ion interaction measurement is finally limite…