DEVELOPMENT OF A NOVEL VARIABLE DISPERSION ZOOM OPTICS FOR MAGNETIC SECTOR MASS SPECTROMETER

Magnetic Sector mass spectrometers are used in the precise isotopic ratio measurement of the inorganic samples in gaseous or solid form. TPD, BARC has been developing these instruments [1] for various applications in DAE. The instruments developed so far are based on conventional design of collector system whereby each collector is mounted on a mechanical motion feed-through [2]. This set-up suffers from the following limitations: a) In case of higher number of faraday cups (5 or more) mechanical assembly is very bulky and unwieldy, b) limited peak flatness (500 – 600 ppm) due to limited aperture size (~ 1 mm), c) difficulty in angular adjustment of the collector cups affecting the peak shape, d) the physical dimensions of the collector viz., 2.5 mm, restricting the placement of collectors at desired locations which limits the mass range for multi-collection ratio measurement to around 250 amu, e) prominent surface bulging effects during the fabrication of collector f) microphonic pick-ups in the collector mounting mechanism leading to higher noise in the amplifier and thus the internal precision.