Fast beam chambers of the set-up ISTRA-M

From an electron avalanche to the lightning discharge

“…In our measurements at relatively high gas gain (≈3.5 × 10 5 ) in the chambers with an anode wire pitch of 1 mm, an anode to cathode distance of 1.5 mm, and d a = 20 μm, chamber efficiency dropped from 99.6% to 98% only at the intensity 10 7 s -1 cm -2 [38]. From these data it follows that the responsibility for fast evacuation of ions from the avalanche region toward the cathode does not rest with the drift velocity: another mechanism is responsible, due to which the ions leave for the cathode from the avalanche region by covering a significant distance in a few nanosec onds.…”

“…Despite the chamber operation under exposure to intense fluxes of charged particles (10 7 -10 8 s -1 cm -2 ) and the large content of isobutane (20%)-which is a source of rad icals contaminating the anode wires 20 μm in diame ter-the detection characteristics of the chambers were maintained after a passage of 3 × 10 13 parti cles/cm 2 through them [37,38], which exceeds by approximately a factor of 100 the radiation resistance of standard chambers [39], in which the avalanche ter minates on the surface of anode wires.…”

Search for heavy neutrino in $$K^{+} \rightarrow \mu ^{+} \nu _{H}$$ K + → μ + ν H decay

“…2, is a magnetic spectrometer complemented by electromagnetic and hadron calorimeters and a Decay Volume. The first magnet M 1 with surrounding 1 mm pitch PC's (BPC (1Y ) , BPC (2Y,2X ) , BPC (3X,3Y ) , BPC (4X,4Y ) of ∼1500 channels in total [17,18]) serves as a beam spectrometer. It is supplemented by two threshold Cherenkov counterš C 1 ,Č 2 for kaon identification and by beam trigger scintillation counters S (1) , S (2) , S (4) , each of 200 × 200 × 1 mm 3 , and a thicker one, 60 × 85 × 6 mm 3 , delivering the reference time, S (3) .…”