A time-of-flight spectrometer has been designed and fabricated for measuring the charge state distributions of target ions produced in collisions of keV-electrons with gaseous target atoms/molecules. The design details of the spectrometer and the description of experimental procedures for optimizing various parameters are presented and discussed. The working principle of the spectrometer, its time-and mass-focussing conditions, transmissions and detection efficiency etc. are given. A few typical test runs on multiple ionization of Ne and Ar gas atoms are illustrated. These spectra are found to yield the time resolution of about 10 ns for Ar 4· ion peak in 24.0 keV e -Ar collisions while the mass resolution of the spectrometer is obtained about 10% at mass m 20. Keywords. Recoil ions; time-of-flight (TOF) spectrometer; multiple ionization. PACS Nos 29.25.-t; 34.70.+e General considerationsThe time-of-flight spectrometer in its simplest form, consists of an ion source and an ioncollector fixed at two opposite ends of an evacuated tube. The ions formed in the ion source, for example, in electron-atom/molecule collisions are extracted out and are made to move towards the collector under a constant or a pulsed electric field. In either case, the time-of-flight of the ions is proportional to Ô´m qµ where q is the charge state and m is the mass of ions.A time-of-flight spectrometer possesses the following salient features:(i) speed of collection of ions at the collector is relatively fast´ 1 µsµ, 623

Development of a new electron-recoil ion/photon coincidence setup for investigating some of the electron induced collision processes, such as electron bremsstrahlung, electron backscattering, innershell excitation and multiple ionization of target atoms/molecules in bombardment of electrons having energies from 2.0 keV to 30.0 keV with solid and gaseous targets is described. The new features include the use of a compact multipurpose scattering chamber, a time-of-flight spectrometer for detection of multiply charged target ions, a 45 AE -parallel plate electrostatic analyzer for measuring energy and angle of the ejected electrons, a room temperature high resolution Si-PIN photo diode X-ray detector for counting the collisionally induced photons, a coincidence data acquisition system consisting of a 200 MHz Pentium based 8K-multichannel analyzer and a standard network of a fast/slow coincidence electronics. In particular, the details of design, fabrication and assembly of indigenous components employed in the setup are presented. Selected experiments planned with the setup are mentioned and briefly discussed. A report on performance, optimization, efficiency, time resolution etc. of the time-of-flight (TOF) spectrometer and that of the 45 AE -parallel plate electrostatic analyzer (PPEA) is presented. Test spectra of electron-recoil ion coincidences, energy distribution of ejected electrons and characteristic plus non-characteristic X-ray spectrum are illustrated to exhibit the satisfactory performance of the developed setup.

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