Direct measurements of the beam current in external-beam PIXE are difficult due to the ionization of air molecules. A method for indirect charge integration has been earlier presented by our research group. The method utilizes the light emission from air molecules excited by the particle beam. The light emission originates from the second positive band system in N-2. The light was measured with a photomultiplier tube. The geometry and the electronics have been improved during the six years that have passed since the method was taken into use. The current from the PM-tube is today about 210 times higher than the particle beam current measured by the means of a Faraday cup. This amplification is useful in the monitoring of small beam currents. The linearity and accuracy of the improved system are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.
|Julkaisu||Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms|
|Tila||Julkaistu - 1999|
|OKM-julkaisutyyppi||A1 Julkaistu artikkeli, soviteltu|
- charge integration
- external beam
- low current measurements
- second positive band system