Space weather effects on drilling accuracy in the North Sea

The oil industry uses geomagnetic field information to aid directional drilling operations when drilling for oil and gas offshore. These operations involve continuous monitoring of the azimuth and inclination of the well path to ensure the target is reached and, for safety reasons, to avoid collisions with existing wells. Although the most accurate method of achieving this is through a gyroscopic survey, this can be time consuming and expensive. An alternative method is a magnetic survey, where measurements while drilling (MWD) are made along the well by magnetometers housed in a tool within the drill string. These MWD magnetic surveys require estimates of the Earth’s magnetic field at the drilling location to correct the downhole magnetometer readings. The most accurate corrections are obtained if all sources of the Earth’s magnetic field are considered. Estimates of the main field generated in the core and the local crustal field can be obtained using mathematical models derived from suitable data sets. In order to quantify the external field, an analysis of UK observatory data from 1983 to 2004 has been carried out. By accounting for the external field, the directional error associated with estimated field values at a mid-latitude oil well (55 N) in the North Sea is shown to be reduced by the order of 20%. This improvement varies with latitude, local time, season and phase of the geomagnetic activity cycle. By accounting for all sources of the field, using a technique called Interpolation In-Field Referencing (IIFR), directional drillers have access to data from a “virtual” magnetic observatory at the drill site. This leads to an error reduction in positional accuracy that is close to matching that of the gyroscopic survey method and provides a valuable independent technique for quality control purposes

A Prototype Fast Multiplicity Discriminator for ALICE L0 Trigger

The design details and test results of a prototype Multiplicity Discriminator (MD) for the ALICE L0 Trigger electronics are presented. The MD design is aimed at the earliest trigger decision founded on a fast multiplicity signal cut, in both options for the ALICE centrality detector: Micro Channel Plates or Cherenkov counters. The MD accepts detector signals with an amplitude range of plus-minus 2.5 V, base duration of 1.8 ns and rise time of 300-400 ps. The digitally controlled threshold settings give an accuracy better than 0.4% at the maximum amplitude of the accepted pulses. The MD internal latency of 15 ns allows for a decision every LHC bunch crossing period, even for the 40 MHz of p-p collisions

Grand-Canonical Ensemble of Random Surfaces with Four Species of Ising Spins

The grand-canonical ensemble of dynamically triangulated surfaces coupled to four species of Ising spins (c=2) is simulated on a computer. The effective string susceptibility exponent for lattices with up to 1000 vertices is found to be $\gamma = - 0.195(58)$. A specific scenario for $c > 1$ models is conjectured.Comment: LaTeX, 11 pages + 1 postscript figure appended, preprint LPTHE-Orsay 94/1

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

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

A study of the etapipi channel produced in central pp interactions at 450 GeV/c

The reaction pp -> pf (eta pi pi) ps has been studied at 450 GeV/c. There is clear evidence for an a2(1320)pi decay mode of the eta2(1645) and eta2(1870). In addition, there is evidence for an a0(980)pi$ decay mode of both resonances and an f2(1270)eta decay mode of the eta2(1870). No evidence is found for a JPC = 2++ a2(1320)pi wave.Comment: 15 pages, Latex, 4 Figures Branching ratio a2pi /f2 eta correcte

A study of the f0(1370), f0(1500), f0(2000) and f2(1950) observed in the centrally produced 4pi final states

The production and decay properties of the f0(1370), f0(1500), f0(2000) and f2(1950) have been studied in central pp interactions at 450 GeV/c. The dPT, phi and |t| distributions of these resonances are presented. For the J = 0 states, the f0(1370) and f0(2000) have similar dPT and phi dependences. These are different to the dPT and phi dependences of the f0(980), f0(1500) and f0(1710). For the J = 2 states the f2(1950) has different dependences to the f2(1270) and f2'(1520). This shows that the dPT and phi dependences are not just J phenomena.Comment: 14 pages, Latex, 4 Figure

A search for charmonium states produced in central pp interactions at 450 GeV/c

A search for centrally produced charmonium states has been presented. There is no significant evidence for any charmonium production. An upper limit of 2 nb is found for the cross section of chic production using the decay chic(1P)-> J/psi gamma.Comment: 10 pages, Latex, 4 Figure

A study of the centrally produced pi0pi0pi0 channel in pp interactions at 450 GeV/c

The reaction pp -> pf (pi0pi0pi0) ps has been studied at 450 GeV/c. The pi0pi0pi0 effective mass spectrum shows clear eta(547) and pi2(1670) signals. Branching ratios for the eta(547) and pi_2(1670) are given as well as upper limits for the decays of the omega(782), a1(1260) and a2(1320) into 3pi0.Comment: 10 pages, Latex, 4 Figure