Two times double gap strip lines read-out RPC

In this contribution we present a new type of structure of an MRPC counter and preliminary results obtained with it. The idea was to use a similar structure as the one of an identical double-gap RPC in which the inner aluminium electrods (the anodes) have been replaced by a Pestov glass of 109 Ωcm resistivity and the read-out to be done via strip lines (like in the Pestov counter, the corresponding strips on the two sides being connected together. The counter configuration is presented. The results reported here have been obtained with gaps of 300 μm, a 2.9 kV voltage for each and a flow of standard gas (85% C2F4H2, 10% SF6 and 5% C4H10 (isobutane)) at normal pressure. The time spectra have been obtained from gamma - gamma coincidence of a 60 Co source, between the two ends of the middle strip and a plastic scintillator of cylindrical size (Φ = 20 mm and h=20 mm) coupled to an XP2020 photomultiplier. Taking only the amplitudes larger than a given value, we looked to the left-right time correlation. The expected trend is shown. Using γ - γ coincidence the counter is fired on the whole length. A clear enhancement in the middle where the 60 Co source was placed was observed. With a narrow condition in the position (of about 30 mm) the sum time spectra t = 1/2(tleft + tright) was obtained. A Gaussian fit gives a σ=1.8 channels ( one TDC 8222A channel corresponds to 60 psec). Substracting quadratically the contribution of the plastic scintillator (90 psec - measured in separate runs using 2 identical scintillators and phototubes) a σ of ≅ 60 psec is obtained for the MRPC structure proposed by us. (authors)