6.2.1 Overview

The test setup was to be mounted into the CASYMS calibration chamber [35]. The chamber has a diameter of 1200mm and is equipped with a turntable allowing the rotation and translation of the setup relative to the incoming ion beam provided by the calibration facility. The test setup was divided into two parts. In the first part a neutral atom beam had to be created out of the ion beam. This was done by reflecting the ion beam from a polished tungsten surface. Upon reflection the primary ions get neutralized with an efficiency close to 100%. Primary molecular ions also dissociate to a large extent making it advantageous to use a molecular primary beam as molecular beams have a much higher intensity at CASYMS. Ion optics removed remaining charged particles after reflection from the neutralization surface. The neutral beam was also geometrically collimated using several slits. The second part was the actual instrument prototype with conversion surface, extraction lens, and time-of-flight section, for which a modified version of a CODIF instrument [36] was used.

Figure 6.1: Schematics of the NICE prototype and the test setup. The ion source of the CASYMS chamber injects an ion beam from the left. The beam is neutralized using a tungsten surface. Deflection plates remove all remaining charged particles. The neutral beam then hits the conversion surface in the entrance system of the NICE prototype. The negative ions produced upon reflection are then collected by an extraction lens. A time-of-flight (TOF) measures the composition of these ions. Typical energy spectra are shown at different points in the prototype. The energy of an incident oxygen atom was taken as reference. As an example expected particle types are shown for a CO \( ^{+}_{2}\) primary beam used for oxygen measurements.

March 2001 - Martin Wieser, Physikalisches Institut, University of Berne, Switzerland