Shunroku Taya

A stigmatic, second-order, double-focusing mass spectrometer

Abstract A double-focusing mass spectrometer of second order was constructed and the focusing property was examined. The ion optical system was determined by computer calculations in order to correct all second-order image aberrations. In the calculations the influences of the fringing field were taken into account. This ion optical system has velocity focusing, radial focusing and axial focusing properties. The instrument is composed of an electric toroidal sector ( r e = 212 mm, φ e = 85.2°, c = 0.5, ρ′ = −106 mm), and a uniform magnetic sector of non-zero entrance and exit angles ( r m = 200 mm, φ m = 90°, ϵ′ = 30°, ϵ″ = −10°). In experimental results, a maximum resolving power of 83 000 at 10% valley separation, and a total transmission of 43% were obtained. Axial focusing action and correction of the crescent shape resulting from second-order aberrations were observed from the shape of spectral lines taken on photographic plates.

A triple focusing mass separator

Abstract A new type of a mass separator having a large transmission rate was constructed. It is composed of a Wien filter with a magnetic entrance angle ( L w = 36 cm, α 1 = 28°, G m = 6 cm, G e = 3 cm) and an electric spherical sector ( ϕ e = 30°, r e = 18 cm, G s = 6 cm). This separator has radial, axial and velocity focusing, i.e. simultaneous triple focusing properties. An optinum resolution of 120 and transmission rate of 68% are obtained at the ion source and collector slit widths of S i = 3 mm, S c = 1 mm.

Analyses of silicon wafers by a high-resolution secondary ion mass spectrometer

Abstract A high-resolution secondary ion mass spectrometer (SIMS) was constructed for solid surface analyses. The instrument is composed of a Hitachi IMA-2 ion probe and a stigmatic, second-order, double focusing mass spectrometer. Commercially available silicon wafers (p-type, 20 Ω cm) were analyzed as test samples. The highest mass resolving power was 11,000 (10% valley). The analytical sensitivity of this SIMS permits detection of boron to silicon at an ion ratio of 10 −7 . The inorganic and hydrocarbon element ions were accurately resolved.

A simple double-focusing mass spectrometer

Abstract A revolutionary double-focusing mass spectrometer is constructed and the focusing property investigated. The instrument consists of an electric parallel plate condenser (6.3×4.2 cm2), a double electrostatic Q lens and a small magnet having pole pieces of rectangular shape (128×45 mm2, rm = 25 cm, φm = 30°, ϵ1 = ϵ2 = 15°). This arrangement facilitates adjustment, because the double-focusing conditions can be satisfied by electrical adjustment of the double Q lens. Therefore, no mechanical adjustment is necessary. The highest resolving power obtained is 1600 for a 10% valley separation.

An experimental study on the stigmatic focusing condition of a magnetic sector mass analyzer

Abstract Radial and axial focusing (stigmatic focusing) properties of a magnetic sector mass analyzer are studied experimentally. The instrument is a uniform magnet with non-zero angular entrance and exit pole edges ( r m = 70 mm, ϕ m = 90°, ϵ 1 = ϵ 2 : variable). The radial focusing properties are observed by mass spectral resolutions, and the axial focusing properties by photographic plates. The experimental radial focusing condition agrees with the calculated result of the sharp cut-off fringing field approximation. However, the axial focusing property is not consistent with the calculation. The stigmatic focusing condition is obtained experimentally at the calculated estimation for the extended fringing field approximation.

Second-order image aberration correction of double-focusing mass spectrometers by electrostatic hexapole lens

Abstract Ion optical properties of an electrostatic hexapole lens are described. The correction methods for second-order image aberrations of double-focusing mass spectrometers are also examined. As an experimental example, the second-order image aberration of a Hitachi double-focusing mass spectrometer are observed, and reduced by the electrostatic hexapole lens of 40 mm length. It is confirmed by photographic plates that the second-order image aberration of curved image lines is corrected by this hexapole lens.

Ion beam image transformation using magnetic quadrupole lenses

Abstract Large circular cross sectional beams extracted from a microwave ion source with multi-aperture electrodes are transformed into rectangular cross sections by a magnetic quadrupole triplet. The extractable ion source current is 50 mA at 5.0 kV and the diameter is 30 mm. In asymmetric lens operation, a rectangularly focused beam which has an 8 mm width and less than 40 mm height is obtained. Experimental focusing characteristics agree well with the theoretical ones for high current beams of from a few mA to 22 mA. It is possible that high purity beams of several tens of mA will be obtained by combining this system with a magnetic sector mass separator.

Influence of space charge neutralization on mass separator transmission

Abstract Ion space charge neutralization by low energy secondary electrons is investigated for a high current Ar+ beam through the transmission measurement of two different mass separators. They are a Wien filter type mass separator (WFS) as a separator containing voltage-supplied electrodes, and a magnetic sector type mass separator (MSS) not containing electrodes. A microwave ion source is employed for obtaining high current beams. The transmission of WFS decreases with the increases of the incident current to WFS and molecular weight of the sample gas used as the discharge gas. The focused beam width of WFS increases drastically when the incident current increases. On the other hand, these values are constant for MSS. It is confirmed experimentally that space charge neutralization deteriorates in the separator containing electrodes and the magnetic separator is useful for high current beams.