Status of the Pestov spark counter development for the ALICE experiment

Abstract

The basic Pestov detector module is shown in l•`ig. 2. lt consists oi two elec 2 Design and Mechanical Construction of the Counter a two-dimensional reconstruction oi the spark location. ionizing particle (KHP). The counter is read out via strip lines, which allows a pressure of l2 bar. which yields l 5 primary electrons from a minimum is possible at twice the threshold voltage (~6 The counter opera.tes at area of the anode remains sensitive. .~\ time resolution as good as 25 ps (r.m.s.) a limited area ol the semi-conductive anode (~ l 2 mmz), while the remaining discharge local, thus increasing the rate capability. The spark discha.rges only use of a semi-conductive anode and of a special gas mixture that keeps the gaseous parallel-plate detector working in the streamer/spark mode. lt makes The Pestov Spark Counter [1,2], schematically shown in Fig. l, is a. single-gap,

Particle identification

“…In large experiments all systems of a general-purpose detector contribute to particle identification by providing relevant parameters which are combined to joint likelihood functions (see Chap. 15). These functions are used as criteria to identify and distinguish different particles.…”

“…Planar spark counters provide excellent time resolution (σ t ≤ 30 ps) if properly constructed [15]. This, however, requires narrow electrode gaps on the order of 100 μm.…”

Particle identification using time of flight

“…In addition, the gas gap is small so at normal pressures there is a high probability that a charged particle will pass through without an ionizing interaction and thus will be undetected; however by pressurizing the chamber to 12 atmospheres, the detection efficiency can be made close to 100%. Thus the detector has to be placed in a pressure vessel; a cross section of the Pestof counter inside a pressure vessel as proposed for the ALICE TOF [12] is shown in figure 7. This detector has some other problems besides the mechanics of the pressure vessel.…”

“…The rate capability of the MRPC as built for ALICE is limited [36], and this will exclude such an MRPC from use in some applications. However this particular detector was made using sheets of soda-lime float glass as resistive plates; this glass has a bulk resistivity of 5×10 12 cm. There are low resistive glass and ceramics being studied for use as resistive plates for high rate applications [37,38].…”