High-pressure effects in miniature arrays of quadrupole analyzers for residual gas analysis from 10−9 to 10−2 Torr

Abstract

The design, construction, and characterization of a miniature array of 16 rods forming nine quadrupole mass analyzers for residual gas analysis are presented. The novel design takes advantage of the reduction of the dimensions and hence the mean free path to broaden the dynamic range by extending the operating pressure range up to 10 mTorr at the high end while maintaining the low-end sensitivity and mass resolution. The small size, low weight, low power consumption, and low cost of this mass analyzer enable many new applications such as in situ process control in high pressure processes. Applications which take advantage of the capability of operating the source pressure two orders of magnitude higher than conventional devices such as high-pressure contaminant monitoring are discussed. Data on high-pressure effects on the ionizer lifetime in various atmospheres and nonlinearities of the signal are presented and correlated with theoretical analysis. Ray tracing simulations and Monte Carlo statistical calculations are used to provide an understanding of the sensitivity reduction at pressures substantially higher than 10 mTorr. These calculations take into account the ion charge density in the source and the dissociation, charge exchange, and energy loss by the ions when colliding with residual molecules along the length of the rods.

Miniature toroidal radio frequency ion trap mass analyzer

“…In a few cases, these devices have been miniaturized [18] to sizes smaller than typical commercial linear quadrupoles although, to date, none have been miniaturized for the specific purpose of field portable instrumentation. Arrays of linear quadrupoles [19,20] have also been reported.…”

Comparison of ion coupling strategies for a microengineered quadrupole mass filter

“…Slightly lower resolution was achieved with a filter constructed using ceramic spacers and ideal hyperbolic electrodes [3], which were positioned to give an inscribed radius of 0.33 mm (about 50% bigger than the inscribed radius defined by 0.5 mm diameter rods). An array described by Boumsellek and Ferran [4,14] also yielded slightly lower resolution at 50% peak height, but very similar base line separation. This filter was constructed using 1 mm diameter rods that were bonded to glass supports using an accurate glass-tometal sealing technique.…”

“…Clearly, as the size of the entrance aperture decreases, there will be an inevitable loss of signal, although some of this can be recovered through the use of an array [2,4]. There is a well-known correlation [13] between the fractional geometrical error and ultimate resolution.…”

“…While there have been numerous attempts to make small analyzers, not all can reasonably be called miniature [1]. However, quadrupole mass filters [2][3][4][5][6] and various types of ion traps [7][8][9] with characteristic dimensions of the order of a few millimeters or less have been demonstrated. The size and weight contribution to a complete mass spectrometer system is not the only benefit of a miniaturized quadrupole mass filter.…”

Development of quadrupole mass spectrometers using rapid prototyping technology

“…First of all, there are semiconventional methods, which were used for realization of miniature quadrupole mass filters (QMFs) and arrays of quadrupole analyzers for residual gas analysis [2][3][4][5]. Another approach includes miniaturization of hyperbolic QMFs using ceramic material, coated with metal to define electrode regions [6,7].…”