Abstract: A semiconductor ion emitter for a mass spectrometer, comprises an electrode having semiconductor whiskers provided on the conductive surface of a base. A process for manufacturing such semiconductor ion emitter, includes steps of evaporating gold onto a wire having a diameter of about 60 .mu.m, preheating the coated wire, and supplying a gas containing the semiconductor for growth of the whiskers on the gold plated wire. An apparatus for such process comprises a vacuum vessel for enclosing the wire, means for controllably heating the wire and means for controllably supplying a gas containing the semiconductor into the vacuum vessel.

Abstract: Binary data is generated by a facsimile scanner or the like. A binary run length code indicating a number of successive "1" or "0" bits in the data is formed. A shift code comprising all "0" or "1" bits in a number equal to the number of the run length code is appended to the run length code only when the run length code is longer than a preceding run length code. A shorter run length code is indicated by inserting logical "0" bits in vacant high order places of the run length code so as to make the run length code equal in length to the previous run length code.

Abstract: The molecules of a sample are ionized and the produced ions are subjected to a dispersion according to their kinetic energies in an electrostatic field and then to a dispersion according to their mass numbers in a magnetic field. Of the mass-dispersed ions, some having a specific mass number are focussed by means of a lens system disposed between the electrostatic and magnetic fields and the focussed ions are detected by an ion detector.

Abstract: A mass spectrometer employing superimposed electric and magnetic fields arranged substantially at right angles. The central orbit of the ion beam is located on an equipotential surface in the electric field at right angles to the magnetic field. The ions constituting the ion beam are separated in accordance with their mass to charge ratios by superimposed fields. The field strengths are adjusted to satisfy the two dimensional double focusing condition.

Abstract: A virtual image type double focusing mass spectrometer having a diverging electrostatic field and a converging magnetic field, wherein parameters related to the fringing effects in the boundaries of said fields and to the distribution of the electrostatic field reduces image aberrations of the second order.