I am looking for material(s) of low sputtering coefficient and which produces not too many secondary electrons. I consider both positive and negative ions of 2-6 keV kinetic energy.
Graphite is a good choice for Faraday cups. It is also good to put a bias grid in front of the cup with a bias of about -200 V to reflect secondary electrons- a ground plane in front of the bias grid is desirable as well. the cup should be encased in a grounded shielded cage such as SS.
Having no data on the sputtering coeff. and secondary emission of W and Mo foils, intuitively I would prefer tungsten or molybdenum. A better advice on the matter can be obtained, I suppose, from Prof. Dr hab. Ryszard Błaszczyszyn, e-mail: [email protected]
Check the first paper on the design, I use it to characterize ion beam from the rupture of a pinch on a dense plasma focus device, if you want more info check the second link.
Depending on your energy range and angle of incidence you have to choose the material for FC.The following paper gives you a good idea about the simulations and calculations needed for a faraday cup design.
Conference Paper Design and Simulation of 10kW Faraday Cup for Ion Beam Curre...