Process Monitoring Business Segment

Series 3000 Cycloid Mass Spectrometer

The Monitor Instruments Series 3000 Cycloid Mass Spectrometer is a high performance gas analyzer intended for quantitative measurement of gas components at masses up to 230 atomic mass units (amu). The basic analysis platform can be packaged in a versatile laboratory configuration or an industrial configuration conforming to Class 1 Division 1 where necessary.

The mass spectrometer design is simple, rugged, has a small footprint and low maintenance. Although there are other mass spectrometers available for high performance gas measurement in laboratory and industrial settings, the Monitor Series 3000 represents a market-changing increase in performance/price ratio.

Cycloidal Technology Overview

The linear cycloid mass analyzer is at the heart of the Series 3000 analysis platform. It uses crossed homogeneous magnetic and electrostatic fields designed to move the ions in a trochoidal trajectory in the plane perpendicular to the magnetic field, as shown in Figure 1. The cycloid is considered to be a “perfect” double focusing mass spectrometer in that an ion beam with variance in both initial speed and direction is brought to a single focal point. The term “perfect” is appropriate since the equations of motion for the ions are rigorously independent of both initial velocity and direction of motion in the ion source.

Figure 1: Linear Cycloidal Ion Trajectories. The magnetic field is into the page.

Superimposing the electric and magnetic fields not only reduces size and complexity, but also eliminates “fringe fields” which are always present in conventional designs. The result is an analyzer with excellent abundance sensitivity (typically less than 30 ppm) and an ideal peak shape for measurement stability. A typical peak shape is illustrated in Figure 2, a spectrum of the nitrogen peak at 28 amu. Here, the ratio of peak width at the top to that at the bottom is at least 0.50. Under these conditions, small mass peaks can be measured without “spillover” from major adjacent peaks over long periods of time with excellent stability and without need for frequent calibration. An additional size related benefit is the ability to operate at higher pressures with little performance penalty due to mean free path considerations. A more complete description of this technology can be found later in this document.

Figure 2: Flat Top Peak Shape.

Due to its small size, this analyzer is inherently low cost, and can be packaged in small form factors for a diverse set of applications. For the first time, laboratory and industrial requirements for high performance gas analysis can be met with a small and inexpensive mass spectrometer. Built for serviceability, all areas of the electronics and vacuum system can be easily accessed. The size of the laboratory configuration (Series 3000 L) shown in Figure 3 is similar to a PC mini-tower.

The Series 3000L

Figure 3: Series 3000L

The Series 3000 “MS engine” can be installed in an industrial configuration like that shown in figure 4.

This 3000 I configuration can provide:

Industrial enclosures for NEMA Class 1 Division 1 or 2 compliance
Application specific sample introduction systems
Supervisory Control and Data Acquisition (SCADA) software architecture for long-term uninterrupted operation
A readily expandable RS-485 I/O bus and external communication protocols for the most demanding applications

The Series 3000I

The results are outstanding: note the excellent resolution and peak shape in the following mass spectrum from a methane balanced Ethylene Oxide process.

Figure 4A: Series 3000I