Determination of the number of wounded nucleons in Pb+Pb collisions at 158 A GeV/c

The charged particle multiplicity distributions measured by two experiments, WA97 and NA57, in Pb+Pb collisions at 158 A GeV/c have been analyzed in the framework of the wounded nucleon model (WNM). We obtain a good description of the data within the centrality range of our samples. This allows us to make use of the measured multiplicities to estimate the number of wounded nucleons of the collision

Sector Multipad Prototype of the FMD-MCP Detector for ALICE (1997)

We present results of the technology, manufacturing andfirst tests of a novel MCP-based sector prototypefor the Forward Multiplicity Detector for the ALICE experiment at the LHC. The detector is to provide better than sqrt(M)/Mresolution for high multiplicity events, and about 50 pstiming resolution. Two Sector MCPs are mounted on a 200 ceramics board with the multipad readout integrated with a passive summator. This microelectronics UHF device provides isochronous analogue summation of the fast 1ns signal components from 8 pads, along with the individual readout of charges. The setup is baked under 300C and then sealedinto a singular thin wall (200 ) stainlesssteel vacuum sector chamber with Ti getter keeping a vacuum of 10-5Torr.The separation of the fast and slow componentsallows us to use this detector as the zero level trigger,in pile up and beam-gas interaction diagnostics and for thedetermination of the collision vertex along the beam axis. The results of the first and future lab and in-beam tests are discussed and presented.SUMMARYThis job is a continuation of our studiesof the fast applications [1]for the Forward Multiplicity Detector in the ALICE experimentat the LHC [2]Two Sector MCPs (about 18 cm2 area) are mountedon a thin (200 ) single ceramics boardwith the microelectronics design for multipad readout integrated with a passivesummator [3].This UHF device provides isochronous analogue summation of thefast components of 1ns signals from 8 pads along with the individual readout of charges [4].The setup is assembled together with theceramic plate which integrates multichannel feedthroughsand one cylinder Ti-getter pump specially developed forthis detector. This ceramic plate is welded to the stainless steel vacuum sector chamber.Special Al coating is applied on the inner side of the 200 micronthick chamber walls in order to prevent hydrogen diffusion. The whole setup is baked under 300C ,a getter Ti pump is activated, and then the chamber is hermetically sealed, providing the working vacuum of 10(-5)Torr. The separation of the fast and slow signal components which is done by passive summatorallows us to use this detector as the zero level trigger, in pile-up and beam-gas interaction diagnostics and for thedetermination of the collision vertex position along the beam axis [2], [4].Small area (1 cm2) prototype detectors were widely used during the initial stages of the technological developments.Vacuum tests were performed: degassing rates were studied for the stainless steel thin wall chamber , Ti getter, MCPs and ceramics board and feedthroughs. UHFstudies confirmed the technological feasibilities of the passive summator and feedtroughs design with the useful frequency range up to 1.1GHz.First in-beam studies were done at the low energy university cyclotron. Future in-beam tests are also planned.Abstract:This job is supported by the International Science andAbstract:Technology Center, Grant No.345.Acknowledgements[1] G.Feofilov et al., NIM A367 (1995) 402-407[2] N.Ahmad et al., "ALICE Technical Proposal ", CERN/LHCC/95-71, LHCC/P3, 15 December 1995, chapters 7 and 9.[3] G.Feofilov et al.,ALICE Int. Note/MCP,95-39,16/11/95[4] L.Efimov, G.Feofilov et al., 2nd-Workshop on Electronics for LHC Experiments, Balatonfured,Hungary, September 23-27, 1996;p.166-169CERN/LHCC/96-39, 21 October 1996<P

Fast Micro-Channel Plate Detector for MIPs

Abstract for the 6th International Conference on Advanced Technology and Particle Physics, to be held at Villa Olmo, Como, Italy, 5-9 October 1998. For a couple of the last decades Micro-channel plates (MCPs) are known as a fast (1 ns), fine granularity (5-12&micro;), high gain (103 -104), excellent time resolution (30-50 ps), high counting rate (1011 1/cm2 was reported) and efficient detector widely used in low energy nuclear physics. Nevertheless, these nice features have not been exploited sufficiently in the high energy experiments so far. The use of MCPs in the HEP experiments demands the developments of technologies different from the low-energy applications: in particular the low mass vacuum thin-wall chambers in the UHV technique. It is the great intrinsic capability of the MCPs for the registration of MIPs, high gain and sharp signals that prompted us to develop a fast multiplicity detector for ALICE at the LHC. The chevron MCP setup (gain up to 10*8) gives a strong signal for the Ultra High Frequency (UHF) readout system capable of combining hte isochronous fast components of the signal summation over the MCP disk with the charge registration from the individual pads for any event. This isochronous multipad readout is based on a specifically developed multichannel passive summator (which serves also as the UHF filter). In the present report we present the status of the isochronous MCP disk development and the experimental tests:model simulations of the MCP detector performance in heavy ion collisions at the LHCtests of various MCP structures (small area prototypes and sector multipad prototype).The programme of experimental tests included: efficiencytiming resolutionlong term stabilityradiation hardnesscounting ratesmultiplicity resolutionThe first results achieved so far:efficiency for MIPs (our old results: 80; K.Oba et al.: 90; Hamamatsu reference: 96; the tests of our new sector prototype are planned).timing resolution (our old in-beam results: 86ps; our in-lab new results: 30-40ps; new in-beam tests are planned).radiation hardness (passive tests at PNPI were done with neutrons up to 1019 for 1cm2).counting rates studies (are in progress)Further important tests are planned at the available beams in 1998: efficiency for MIPs, timing resolution, multiplicity resolution. Results are tobe presented and discussed

Determination of the number of wounded nucleons in Pb+Pb collisions at 158 A GeV/c

The charged particle multiplicity distributions measured by two experiments, WA97 and NA57, in Pb+Pb collisions at 158 A GeV/c have been analyzed in the framework of the Wounded Nucleon Model (WNM). We obtain a good description of the data within the centrality range of our samples. This allows us to make use of the measured multiplicities to estimate the number of wounded nucleons of the collision