Fast Pre-Trigger Electronics of T0/Centrality MCP-Based Start Detector for ALICE

This work describes an alternative to the current ALICE baseline solution for a TO detector, still under development. The proposed system consists of two MCP-based T0/Centrality Start Detectors (backward-forward isochronous disks) equipped with programmable, TTC synchronized front-end electronic cards (FEECs) which would be positioned along the LHC colliding beam line on both sides of the ALICE interaction region. The purpose of this arrangement, providing both precise timing and fast multiplicity selection, is to give a pre-trigger signal at the earliest possible time after a central event. This pre-trigger can be produced within 25 ns. It can be delivered within 100 ns directly to the Transition Radiation Detector and would be the earliest L0 input coming to the ALICE Central Trigger Processor. A noise-free passive multichannel summator of 2ns signals is used to provide a determination of the collision time with a potential accuracy better than 10 ps in the case of Pb-Pb collisions, the limit coming from the electronics. Results from in-beam tests confirm the functionality of the main elements. Further development plans are presented

Fast front-end L0 trigger electronics for ALICE FMD-MCP tests and performance

We present design details and new measurements of the performance of fast electronics for the Forward Multiplicity Detector for ALICE. These detectors based on sector type Microchannel Plates (MCP) forming several disks gave the very first trigger decision in the experiment (L0). Fast passive summators integrated with the detectors are used for linear summation of up to eight isochronous signal channels from MCP pads belonging to one sector. Two types of microelectronics design thin film summators were produced. We present test results for these summators, working in the frequency range up to 1 Ghz. New low noise preamplifiers have been built to work with these summators. The new design shows a good performance with the usable frequency range extended up to 1 Ghz. An upgrade of the functional scheme for the L0 ALICE pre-trigger design is also presented.Abstract:List of figures Figure 1: ALICE L0 Trigger Front-End Electronics Functional Scheme. Figure 2: UHF design for a fast passive summator based on directional couplers. Figure 3: Photo of an industrially produced passive summator based on circular bridges. Figure 4: Oscillogram of the fast 4 signals separated by different delays shown at the fast output of the passive summator. Figure 5: The same as in Figure 4, but with the delays removed. Figure 6: Fast preamplifier layout. Figure 7: Gain versus Frequency Response for fast preamplifier. Figure 8: Transition response of the preamplifier for a 100 psec rise time step function. Figure 9: The shape of the MCP signal measured after the summator and fast preamplifier. </A

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

AlN/ZnO/diamond structure combining isolated and surface acoustic waves

International audienceIn order to generate surface acoustic waves (SAW) and waveguiding layer acoustic waves (WLAW) simultaneously, a multilayer structure of AlN/ZnO/diamond has been proposed. This structure has been investigated theoretically (two-dimensional finite element method) and experimentally. The nature of the excited modes and their order were identified by modeling and confirmed experimentally by measuring the frequency response of the device in the air and in contact with the liquid. The demonstrated structure can be used to realize a packageless sensor or resonator, using the WLAW alone. A temperature compensated gas or liquid sensor can also be realized by combined usage of the SAW and the WLAW

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

Fast front end L0 trigger electronics for ALICE FMD-MCP tests and performance

Also published in South African Journal of Geomatics, 1(1), 77-91This research investigates a methodology that the Cape Town City Council (CTCC) can use to improve flood risk assessments. Previous studies show that pairwise comparison method (PCM) can be used in conjunction with Geographic Information Systems (GIS) for more accurate risk assessment. Risk weights were subsequently calculated using pairwise comparisons for each settlement household based on questionnaire responses. The risk weights were then mapped into the GIS to show spatial disparities in flood risk. The various maps showed that vulnerability and risk are not homogeneous across Graveyard Pond settlement, and as well could pinpoint dynamics that amplify risk

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