The second stability region of the quadrupole mass filter. II. Experimental results

Abstract The quadrupole mass filter can be operated in a stability region near a = 0, q = 7.547. The resolution achievable was examined as a function of quadrupole field length for various r.f. frequencies and ionic masses. The limitations to performance were compared with those of the same quadrupole operating in the normal manner. With the particular ion source used, sensitivity at resolutions of a few hundred was an order of magnitude lower than in the normal operation. However, there was a length advantage of about fourteen times and resolutions of greater than 1000 could be achieved with ions of 300 V energy. Ultimate achievable resolution was only about 50% greater than in normal operation.