Multi-Cathode SNICS

Multi-Cathode Source of Negative Ion by Cs Sputtering (MC-SNICS) is capable of holding 40 cathodes. Cathode holder can be rotated in both ways from control room. Bidirectional motion and quick change of cathodes is necessary in AMS measurement for changing standard and AMS sample quickly to neglect accelerator parameter variation effect between different measurements.

Re-circulating Gas Stripper

IUAC Pelletron facility is equipped with foil stripper and gas stripper assembly. For AMS studies, transmission through the accelerator should be optimum. Gas stripper produces less divergence after stripping compared to foil stripper. Transmission also reduces by scattering of beam by gas molecules in accelerating tubes. So good vacuum should be maintained in these tubes. Therefore a new re-circulating turbo molecular pump - based pumping system has been designed and installed in the high - voltage terminal of the accelerator. This helps in improving beam transmission by maintaining good vacuum in the accelerating tubes while holding required gas pressures in the stripping area.

Off-Set Faraday Cup

Off-Set Faraday is installed after the analyser magnet. It is used to count stable isotopes which follows different trajectory after passing through analyser magnet in the case of simultaneous injection of both isotopes.

For example In the case of Be-10 measurement both ¹⁰Be¹⁷O^- and ⁹Be¹⁷O^- are injected simultaneously by selecting mass 26 in the injector magnet and that after acceleration¹⁷O⁵⁺ which is representative of ⁹Be current, is collected in the off-Set Faraday cup.

Off-Set Faraday cup is fitted with linear motion feed through and port aligner to make sure that all the stable ion beam should be collected in the Cup.

Wien Filter

Stripping can also happen at the places other than terminal by residual gas molecules inside the accelerating tube. These ions may not have the assumed value of kinetic energy T and accidentally can match the MT/q² and can not be rejected by the analyser magnet. Stable isotope can also come by scattering off chamber walls of the magnet or residual gas molecules, because they are much more abundant. All these unwanted entities can be separated by the Wien filter (T/M selection).

In Wien filter electric field E and magnetic field B are oriented at right angle to each other and perpendicular to the direction of motion of the ions. Wien filter transmits only those ions having a particular velocity, which is tuned with electric and magnetic field inside the Wien filter given by v = E / B. All other unwanted ions are deflected from the central path which are later intercepted by the slit installed before the detector.

Detection Setup

AMS Chamber

AMS chamber is equipped with remote controlled ladder (containing solid state detector and quartz), insertable Faraday cup, and view ports.

Clean Chemistry Laboratory

In AMS the isotope of interest is filtered (separated) from interfering isotopes at various levels. Chemical processing is the first filtering stage. During this stage the isotope of interest is separated from various elements present in the sample and converted in a suitable chemical form to produce high ion yield from the ion source. Chemical processing of sample also provide uniform matrix for analysis and reduces the mass of sample to be put in the ion source and thereby reduces the time needed to attain a given level of precision. Sometimes specific chemical form of the radionuclide reduces isobaric background.

A clean chemistry laboratory has been recently developed for sample processing. The laboratory is a metal free and equipped with all modern instruments. The lab has been designed to be kept at a positive pressure than the atmosphere with the clean air of about 6000 class. Laminar Flow stations of about 100 class air environment are being utilized for performing the column chemistry for samples processing.