In the first example, we build an upper part of the stability triangle for a quadrupole mass filter with hyperbolic electrodes. Note that it takes approximately 2 hours to plot the diagram on an Intel Core i7 (2.80 GHz) processor.

The analyser has the inscribed radius ro=5 mm and 200 mm long hyperbolic electrodes. A sinusoidal RF voltage is applied to electrodes at the frequency of 2 MHz.

To plot the diagram in the DC offset-versus-RF amplitude space for 609 Da ions, a powerful Scan2D tool is used. In simulations, we leave RF amplitude fixed and vary DC offset trough 50 values. Then RF amplitude is changed and computations are repeated again. In every single scan, 100 ions oscillate between the electrodes for 200 us in the X-Y plane and the remaining ions are counted.

In the second example, we use 2D scan to build a stability chart for a 3D ion trap.

A sinusoidal RF voltage at 1 Mhz is applied to the ring electrode of the ion trap with r0 = 7.07 mm and z0 = 10 mm. To plot the full stability zone, we scan RF amplitude from 0 to 9 KV and DC offset voltage in the range from -2100V to +500 V.

A computation of the diagram on an Intel Core i7 (2.80 GHz) processor takes 2 hours.

Here we present one more exciting exercise for a quadrupole mass filter with cylindrical rods.

The electric field in such analyzers deviates from the ideal quadrupole field and suffers from some nonlinear distortions.

Normally, stability diagrams are computed for the ideal quadrupole field.  SIMAX offers a unique opportunity to compute the trapping efficiency as a function of operating parameters (amplitude of the RF supply and DC voltage) for any arbitrary electrode system with a non-perfect field, for example, for a quadrupole mass analyzer with cylindrical rods. In this example, the filter with r/r0=1.125 is examined (this is a commonly used value for quadrupole mass filters with cylindrical rods).

The trapping efficiency for a quadrupole mass filter with cylindrical rods in a normal mode of operation for reserpine ions (609 Da) computed for the quadrupole mass filter with ro=5mm, r/ro=1.125. The mass filter is driven by a sine wave RF voltage at 1MHz. Note, that the nonlinear field completely destroys the tip of the stability triangle. There is no more clear Y boundary (on the right side of the diagram) since it is also distorted by the field imperfections. This affects the stability in the Y direction substantially.

A computation of the diagram on an Intel Core i7 (2.80 GHz) processor takes 1 hour.

The trapping efficiency for a quadrupole mass filter with cylindrical rods in a normal mode of operation for reserpine ions (609 Da) computed for the quadrupole mass filter with ro=5mm, r/ro=1.125. The mass filter is driven by a sine wave RF voltage at 1MHz.

Note, that the nonlinear field completely destroys the tip of the stability triangle. There is no more clear Y boundary (on the right side of the diagram) since it is also distorted by the field imperfections. This affects the stability in the Y direction substantially.

The X-band-I obtained with AC1= 3.7551 V and AC2= 11.0399 V for reserpine ions (609 Da) for the quadrupole mass filter with cylindrical rods with ro=5mm (r/ro=1.125) operated at the main frequency of 1MHz.

Note, that the boundaries of the X-bands are not affected by nonlinear field distortions!

The X-band-I for reserpine ions (609Da) in the quadrupole mass filter with hyperbolic rods, r0 =5 mm operated at the main RF frequency of 1MHz with AC1= 3.7551V and AC2= 11.0399V