Operation of the Zero Ion Backflow electron multiplier in pure argon

The operation of the Zero Ion Backflow electron multiplier in pure argon is presented as an alternative to the readout of ionization signals from Time Projection Chambers. The Zero Ion Backflow electron multiplier operates in a noble gas atmosphere and totally suppresses all the secondary ions produced in the electron avalanches. It is composed of a proportional scintillation gap coupled to a gaseous photon-multiplier. The ion backflow suppression of the Zero Ion Backflow electron multiplier was demonstrated to be independent of the total charge gain of the detector. This paper presents the operation of the Zero Ion Backflow electron multiplier in pure argon with a GPM composed by a THCOBRA coupled to a CsI photocathode. For a scintillation gap of 7.5 mm an optical gain close to unity and energy resolution of 35% were achieved, without deterioration of the primary ionization statistical information.