Cyclotron Magnet Research Articles

The quadratic Zeeman-effect in the principal series of caesium, rubidium and potassium

The quadratic shift due to the atomic diamagnetism has been observed in the principal series of caesium, rubidium and potassium in absorption by means of the Amsterdam cyclotron magnet and a grating mounting. The theoretical formula for the quadratic Zeeman-effect is shown to account reasonably well for the observed displacements. In caesium weak components are found corresponding to electron transitions involving Δm s = ± 1, which are to be expected in the intermediate stages between anomalous Zeeman-effect and complete Paschen-Back effect.

A Study of the Alpha-Particles from Po with a Cyclotron-Magnet Alpha-Ray Spectrograph

A description is given of an alpha-ray spectrograph, consisting of the Princeton cyclotron magnet and a Plexiglas deflection chamber, in which the alpha-particles can be bent into a semi-circle of about 80-cm maximum diameter. Three different methods of detection have been employed according to the different strengths of the radioactive sources. They are the ordinary photographic method, the counting method, and the method of photographic tracks. The behavior of the spectrograph has been investigated with Po alpha-particles by the three methods of detection. The forms of the energy distribution have been determined, respectively, by these three methods and agree fairly well with one another. The half-width of the main line under favorable conditions is less than \textonehalf{} mm, which is equivalent to about 0.01 Mev. The intensities a few millimeters away from the maximum are less than 0.1 percent of the main line intensity. The track method of detection has been used to study both the low and high energy regions of the main line of the Po alpha-particles. Microscopic examination reveals distinctly a series of weak groups in the low energy region, while in the high energy region no indication of any discrete group has been found. These experiments have been carefully repeated with three different sources and under different experimental conditions. In each case similar results have been obtained. The emission of these different alpha-particle groups from Po may, as in the case of ordinary fine structure, leave the product nucleus, Pb, in different excited states. Then, when the Pb nucleus falls from one of these quantum states to the normal state, a gamma-ray quantum is given off. As far as energy and intensity are concerned, these weak groups of alpha-particles are generally compatible with the gamma-ray lines from Po as measured by Bothe. However, their intensities are not in agreement with the current theory of alpha-decay, as can be seen from the abnormally large spin changes deduced from the theory for the different alpha-transformations, and also from the large deviation of the Geiger-Nuttall curve for these groups from the curve for the members of the Ra family. Possible explanations of these short-range alpha-particles from Po have been suggested and discussed.

A Cyclotron Which Allows the Accelerated Particles to Emerge in a Direction Parallel to the Dee Interface

The construction of the dees, deflection channel, and vacuum chamber of a cyclotron is described. The design allows the accelerated ions to pass through an electrostatic deflecting field for one-quarter of a revolution and then to proceed through the magnetic fringing field for another quarter of a revolution before they leave the cyclotron vacuum chamber. This provides that the ions emerge in a direction which is parallel to the dee interface and perpendicular to the principal azimuthal plane through the long axis of the cyclotron magnet. Operation shows that the ions follow the prescribed path. The advantages of this construction are: 1. Relatively low deflection voltages are necessary. 2. Large beam currents (100 μa) mono-energetic to 2 percent can be obtained directly from the cyclotron. 3. It is easy to ``pipe'' the beam to a point many feet from the cyclotron. Therefore, many experiments can be performed outside of shielding tanks (4 feet of water) where possible errors due to background radiations from the cyclotron are small. 4. Magnetic analyzing equipment placed in the beam path provides a beam current density of approximately 0.001 μa/mm2 and mono-energetic to 0.1 percent. Several curves showing typical operational characteristics of a cyclotron are included.

A Voltage Stabilizer for a Direct-Current Generator

A simple stabilizer for a cyclotron magnet is described, which stabilizes the voltage across the magnet within one part in 2000. It acts as a variable resistance in parallel with the generator field, which remains shunt connected to the armature.

The Quadratic Zeeman Effect

The Zeeman effects of the principal series lines of sodium and potassium in the range $n=10 \mathrm{to} 35$ are observed in absorption, using the new 60-inch cyclotron magnet. With a field of 27,000 gauss, the lines having $n$ in the neighborhood of ten show a normal triplet representing the complete Paschen-Back effect of the narrow $^{2}P$ doublet. From about $n=12 \mathrm{to} 20$ all components show an increasing displacement toward short wave-lengths proportional to ${({n}^{*}),}^{4}$ the shift of the $\ensuremath{\pi}$ components being half that of the center of the two $\ensuremath{\sigma}$ components. This is the quadratic Zeeman effect, varying as ${H}^{2}$, and is here measured and compared quantitatively with theory for the first time. The agreement with the simple theory is excellent as far as $n=20$. Beyond this the lines show an additional displacement in the same direction, increasing as a higher power of $n$. At the same time the lines are broadened toward the red, with indications of an unresolved component whose intensity increases rapidly with $n$. The displacement is interpreted as a perturbation by the $F$ states, whose separation from the $P$ states in this region becomes comparable with the magnetic energy. The additional lines causing the broadening represent forbidden transitions $^{2}S\ensuremath{\rightarrow}^{2}F$. Beyond $n=28$ the broadening increases suddenly and becomes symmetrical, until the lines are no longer distinguishable at $n=35$. All of these perturbation effects are compared with the theoretical results given in the accompanying paper by Schiff and Snyder. Some features are accounted for quantitatively, while the others are satisfactorily explained qualitatively.