Magnetic Lens System Research Articles

後方散乱法を用いたマイクロアナリシス

A new microanalysis using backscattering method was applied to measure lateral distributions as well as depth distributions of impurities in semiconductors. High energy He+-beam from the Van de Graaff accelerator could be squeezed to 70500μmφ on the target by means of the quadrupole magnetic lens and slits system. The lateral distributions of impurities in semiconductors were measured by step scanning i.e, by using a goniometer which slides the targets along the direction perpendicular to the beam line with a minimum step of 10μm.The microanalysis was applied to measure the lateral and depth distributions of Au atoms at GaAs crystal surface sintered in the nitrogen atmosphere after Au evaporation to GaAs crystal surface. It was found that the lateral distributions were not uniform either on the surface or in the bulk. Au atoms were diffused abnormally to the deep region in GaAs crystals, and the concentration profiles of Au were not fitted to complementary error functions. Also presented are the measured results of distributions of Sn doped into Si by means of two different techniques, i.e, doped oxide method and CZ pulling method.

Minimum Chromatic Aberrations of Magnetic Quadrupole Objective Lenses

Orthogonal magnetic quadrupole lens systems that could serve as electron microscope objectives are treated theoretically. After certain constraints are placed on the quadrupole field strength, the calculus of variations is applied to obtain systems with minimum chromatic aberrations. A digital computer was used to calculate optimum orthomorphic and anamorphotic objective type systems. The resulting orthomorphic systems have four lenses while the corresponding anamorphotic systems have three. The chromatic aberration only varies by a factor of 2 in this study indicating its relative insensitivity to choice of lens systems. It is found that the optimum quadrupoles have about 3.6 times as much chromatic aberration as round lenses with comparable fields and dimensions.

Nomograms for calculating the optical parameters of weak magnetic quadrupolar lens systems concerning antisymmetrical doublet and symmetrical triplet, for electrons in the 1–10 MeV energy range

Nomograms for calculating the optical parameters of weak magnetic quadropolar lens systems concerning antisymmetrical doublet and symmetrical triplet, for electrons in the 1–10 MeV energy range, are described and the conditions in which they are valid are give.

The ERA 4 MeV Injector

A pulsed electron accelerator has been constructed and is now in operation at the Lawrence Radiation Laboratory, Berkeley. It was designed specifically for and is used as an injector for ERA (electron ring accelerator) studies. Electron bursts of 1200 amperes and 40 nanoseconds duration can be produced at energies of 1.0 MeV to 4.25 MeV. The present repetition rate is approximately one per second. Acceleration is accomplished by means of ferrite loaded accelerating sections, each of which is capable of maintaining a 250 kV voltage pulse across the accelerating gap for a period of 40 ns. The voltage pulse has a rise time of 12 ns and the total timing jitter is of the order of one nanosecond. Five sections stacked together and operated as a unit function as the electron gun. The gun employs a field emission cathode and is operated at approximately 1 MV. Additional acceleration is achieved by means of an iterated system of accelerator sections and solenoidal magnetic lenses.

Magnetic Lens System of Unit Magnification for High Energy Charged Particles

A magnetic lens system designed from studies made with computing machines has been built and used at the Brookhaven cosmotron. It collected pions of 1020 MeV/c mean momentum produced at a target in the external proton beam, selected a narrow momentum bandwidth from a continuous momentum spectrum, recombined the selected momenta, and refocused the pions to an image of unit magnification. The effective solid angle of acceptance was 5.04×10−3 sr and the momentum band pass width was ±30 MeV/c. The measured particle yield on 1 in.2 at the focus was 5×105 for 6×1010 internal 3BeV/c protons; 27% were positive pions and 73% were protons.

Alternating Gradient Electrostatic Focusing for Linear Accelerators

The properties of the focusing systems using alternating convergent and divergent electrostatic lenses which were proposed by Courant et al. and Blewett are studied in detail, applied to Alvarez type of linear accelerators. It is found that the introduction and the removal of the focusing force of the system can be made approximately adiabatic by using half-length injection and extraction lenses. The appropriate choice of the parameters of the lenses in practical cases and the behavior of the ion beam going through such a system are discussed. The results can easily be reinterpreted to apply to magnetic lens systems.