IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Construction of the New Prototype of Main Quadrupole Cold Masses for the Arc Short Straight Sections of LHC Peyrot M Rifflet J M Simon F Tortschanoff Theodor Védrine P 2000 10 170 173 Each cold mass of the short straight sections in the eight LHC arcs will contain a 3.25 m long twin aperture quadrupole of a nominal gradient of 223 T/m. This magnet will be aligned in a 5.3 m long inertia tube together with auxiliary magnets on each end. On the quadrupole connection end either a pair of 38 cm long octupole or trim quadrupole magnets will be mounted, on the other end there will be combined sextupole-dipole correctors with a yoke length of 1.26 m. The powering of the main quadrupoles will be assured by two pairs of copper stabilized superconducting bus-bars placed inside the cold mass next to the bus-bars for the main dipole magnets. Each of the two quadrupole apertures will be connected to its quench protection diode. The construction of three prototypes has been entrusted to the CEA/Saclay laboratory, in the frame of the special French contribution to the LHC project. The first cold mass prototype has been completed and warm-measured for its multipole content at CEA. The second cold mass is presently under completion. The paper will review the experience with the development of the quadrupole coils and cold mass construction and gives the results of the first warm magnetic measurements. An outlook for the series manufacture of the 400 arc quadrupole magnets and their cold masses for the LHC machine will complete the report. research-article

The CERN Cryogenic Test Facility for the Atlas Barrel Toroid Magnets Haug F Cambon A Delruelle N Orlic J P Passardi Giorgio Tischhauser Johann 1999 The superconducting magnet system of the ATLAS detector will consist of a central solenoid, two end-cap toroidal magnets (ECT) and the barrel toroid magnet (BT) made of eight coils symmetrically placed around the central axis of the detector. The magnets will be tested individually in a 5000 m2 experimental area prior to their final installation at an underground cavern of the LHC Collider. For the BT magnets, a dedicated cryogenic test facility has been designed which is currently under the construction and commissioning phase. A liquid nitrogen pre-cooling unit and a 1200 W@4.5K refrigerator will allow flexible operating conditions via a rather complex distribution and transfer line system. Flow of two-phase helium for cooling the coils is provided by centrifugal pumps immersed in a saturated liquid helium bath. The integration of the pumps in an existing cryostat required the adoption of novel mechanical solutions. Tests conducted permitted the validation of the technical design of the cryostat and its instrumentation. The characteristics of one pump were measured and pressure rise of 300 mbar at nominal flow of 80 g/s confirmed the specifications. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Design and construction of a 1 m model of the low current superconducting quadrupole for the LHC insertions Kirby G A Lucas J Ostojic R Rodríguez-Mateos F Krischel D Schillo M 2000 10 150 3 About one hundred individually powered low current superconducting quadrupoles will be installed in the LHC insertions. One of the design requirements was to keep the excitation current of the magnet below 6 kA in view of minimizing the costs of the powering circuits. The design of the quadrupole is based on a 8.2 mm NbTi cable, and is designed for a nominal gradient of 200 T/m at 1.9 K. In this paper we present the design of the quadrupole and discuss the construction details of the 1 m single aperture model which has been recently completed. research-article

A Method to Measure Thermal Deformation of Superconducting Magnet Cross Sections Grau-Carles A García-Tabarés L Todesco Ezio Tommasini D Siegel N 1999 The precision measurement of the cable positioning in superconducting coils is of great interest both at room and liquid nitrogen temperatures because mechanical and thermal deformations affect the quality of the magnetic field. The paper describes a new two-coordinate measuring device, which is able to obtain scanned images of flat composite samples at liquid nitrogen temperature. The sample is cooled at 77 K into a flat quartz tray to permit the optical access to the sample from the bottom. The comparison of the images taken at room and liquid nitrogen temperatures by a high-resolution flatbed scanner gives the thermal contraction of the components. research-article

The Magnets for the LHC Experiments Taylor T M 1999 The Large Hadron Collider (LHC) presently under construction at the European Laboratory for Particle Physics (CERN) will provide proton-proton collisions at the 14 TeV level. Each of the four approved detectors (ALICE, ATLAS, CMS, and LHCb) to be installed at the interaction points of this machine relies on a sophisticated magnet system for separation and momentum measurements of the charged particles. The magnets are being designed, manufactured, tested and installed under the technical and financial responsibility of the experiment collaborations, but must satisfy constraints imposed by the laboratory, regarding in particular the cryogenics, powering, controls, and safety. The delivery and assembly schedules are also highly constrained by the requirement to have the magnet systems fully installed before the projected commissioning of the accelerator in 2005. The report will compare the salient features of these magnet systems, and of their integration into the CERN environment. research-article

Cryogenics for the Large Hadron Collider Lebrun P 1999 The Large Hadron Collider (LHC), a 26.7 km circumference superconducting accelerator equipped with high-field magnets operating in superfluid helium below 1.9 K, has now fully entered construction at CERN, the European Laboratory for Particle Physics. The heart of the LHC cryogenic system is the quasi-isothermal magnet cooling scheme, in which flowing two-phase saturated superfluid helium removes the heat load from the 36'000 ton cold mass, immersed in some 400 m3 static pressurised superfluid helium. The LHC also makes use of supercritical helium for non-isothermal cooling of the beam screens which intercept most of the dynamic heat loads at higher temperature. Although not used in normal operation, liquid nitrogen will provide the source of refrigeration for precooling the machine. Refrigeration for the LHC is produced in eight large refrigerators, each with an equivalent capacity of about 18 kW at 4.5 K, completed by 1.8 K refrigeration units making use of several stages of hydrodynamic cold compressors. The cryogenic fluids are distributed to the cryomagnet strings by a compound cryogenic distribution line circling the tunnel. Procurement contracts for the major components of the LHC cryogenic system have been adjudicated to industry, and their progress will be briefly reported. Besides construction proper, the study and development of cryogenics for the LHC has resulted in salient advances in several fields of cryogenic engineering, which we shall also review. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 The Helium Cryogenic System for the ATLAS Experiment Delruelle N Haug F Passardi Giorgio ten Kate H H J 2000 10 1511 13 The magnetic configuration of the ATLAS detector is generated by an inner superconducting solenoid and three air-core toroids (the barrel and two end-caps), each of them made of eight superconducting coils. Two separated helium refrigerators will be used to allow cool-down from ambient temperature and steady-state operation at 4.5 K of all the magnets having a total cold mass of about 600 tons. In comparison with the preliminary design, the helium distribution scheme and interface with the magnet sub-systems are simplified, resulting in a considerable improvement of the operational easiness and the overall reliability of the system at some expense of the operational flexibility. The paper presents the cryogenic layout and the basic principles for magnets cool-down, steady state operation and thermal recovery after a fast energy dump. research-article

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Nucl. Instrum. Methods Phys. Res., A Nucl. Instrum. Methods Phys. Res., A 0167-5087 A study of the transverse fluctuations of hadronic showers in the NOMAD electromagnetic calorimeter Autiero D Baldo-Ceolin Massimilla Bobisut F Camilleri L L Cattaneo Paolo Walter Cavasinni V Collazuol D Conforto G Conta C Contalbrigo M De Santo A Di Lella L Ferrari R Flaminio Vincenzo Fraternali M Gibin D Gninenko S N Graziani G Guglielmi A M Iacopini E Kirsanov M M Kovzelev A Lacaprara S Lanza A La Rotonda L Laveder M Lupi A Marchionni A Martelli F Mezzetto Mauro Orestano D Pastore F Pennacchio E Petti R Polesello G Renzoni G Roda C Rubbia André Salavatore F Sconza A Toropin A N Valdata-Nappi M Veltri M Vercesi V Volkov S 1998 411 The transverse shower shape of the energy deposition of hadrons in the NOMAD lead glass calorimeter has been studied by exposing a prototype of this calorimeter to pion test beams of various momenta and incident angles. Large event to event fluctuations in the shower shape and significant energy depositions far from the incident hadron were observed making it difficult to associate all the deposited energy to the incident hadron that caused it. Since in the NOMAD detector the momenta of charged hadrons are measured by a magnetic spectrometer, such an association is necessary to be able to subtract from the calorimeter all the energy caused by the observed charged hadrons in order to avoid double counting. Probability functions based on the measurements have been developed to describe fluctuations of the lateral shower shape.\ Starting from these functions, an algorithm is developed for identifying the energy deposition associated to a charged hadron.\ The identification and separation of overlapping showers based on these functions is also discussed. The Monte Carlo simulation of the calorimeter reproduces the test beam data well therefore allowing the application of the algorithm at angles and momenta not studied in the test beam. research-article

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Summary notes of the GLM held on 10.12.2001 BAILEY R. 2001 DSLLIB

SPLinac Tückmantel Joachim 2001 The beam in a proton linac is very sensitive to field perturbations in the cavities. Therefore a simulation program was written modeling longitudinal beam dynamics in a realistic composite linac RF system. Fast RF vector sum feedback loops control several cavities with b-dependent transit time factors driven by one transmitter. Modeling of feedback loops covers limited transmitter power and bandwidth and possible loop-delay. Vector sum calibration errors, power splitting errors and scatter in the coupling strength to the cavities are optional as well as beam loading of the pulsing beam. Different modes of mechanical cavity perturbations including Lorentz force detuning can be chosen. A multitude of phase-space representation of bunches as well as RF quantity plots are available, most of them can be assembled as a movie, showing the system dynamics in 'real time'. research-article

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Design Considerations for the LHC 200 MHz RF System Boussard Daniel Chiaveri Enrico Kindermann H P Linnecar Trevor Paul R Marque S Tückmantel Joachim 2000 The longitudinal beam transfer from the SPS into the LHC 400 MHz buckets will not be free of losses without a lower frequency capture system and a fast longitudinal damping system in LHC. We present a complete study of a combined system using four identical copper cavities at 200 MHz delivering 3 MV total CW voltage and having still enough bandwidth to achieve fast longitudinal damping. The shape of a cavity was designed according to the accelerating mode performance, its tuning and the higher order mode spectrum with respect to the LHC beam lines and their possible attenuation. The possibility to park the cavities during coast was included. The local heat load and the corresponding cooling water distribution as well as deformations were studied and techniques to build the cavity with all ports at low cost are proposed. The parameters of the RF generators, couplers and detuning are determined. Simulations of the total LHC RF system incorporating real delays, generator bandwidth and the control loops confirm that this system is capable of capturing and damping the beam longitudinally without losses. PREPRINT

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Limitations on LHC beam intensity in the SPS in 2000 Linnecar Trevor Paul R 2000 research-article

Radiation Detection and Measurement Knoll Glenn F 1989 BOOK

Tracking of the high $p-{t}$ particles in ITS stand-alone detector Kindziuk P Leszczynski P Maliszewski A Mazur J G Pluta J Roszczewski A Gutbrod H H 1999 PREPRINT

High resolution pixel detectors for $e^{+}e^{-}$ linear colliders Caccia M Campagnolo R Meroni C Kucewicz W Deptuch G Zalewska-Bak A Battaglia Marco Österberg K Orava Risto Higueret S Winter M Turchetta R Grabiec P Jaroszewicz B Marczewski J 1999 The physics goals at the future e+e- linear collider require high performance vertexing and impact parameter resolution. Two possible technologies for the vertex detector of an experimental apparatus are outlined in the paper: an evolution of the Hybrid Pixel Sensors already used in high energy physics experiments and a new detector concept based on the monolithic CMOS sensors. PREPRINT

Design and Testing of a Prototype Pixellated CZT Detector and Shield for Hard X-Ray Astronomy Bloser P F Grindlay J E Narita T Jenkins J A 1999 We report on the design and laboratory testing of a prototype imaging CZT detector intended for balloon flight testing in April 2000. The detector tests several key techniques needed for the construction of large-area CZT arrays, as required for proposed hard X-ray astronomy missions. Two 10 mm x 10 mm x 5 mm CZT detectors, each with a 4 x 4 array of 1.9 mm pixels on a 2.5 mm pitch, will be mounted in a ``flip-chip'' fashion on a printed circuit board carrier card; the detectors will be placed 0.3 mm apart in a tiled configuration such that the pixel pitch is preserved across both crystals. One detector is eV Products high-pressure Bridgman CZT, and the other is IMARAD horizontal Bridgman material. Both detectors are read out by a 32-channel VA-TA ASIC controlled by a PC/104 single-board computer. A passive shield/collimator surrounded by plastic scintillator surrounds the detectors on five sides and provides a ~45 deg field of view. The background spectrum recorded by this instrument will be compared to that measured by a single-element CZT detector (10 mm x 10 mm x 2 mm high-pressure Bridgman material from eV Products) fitted with the same passive/plastic collimator but including an active BGO shield to the rear. This detector has been previously flown by us completely shielded by a passive cover. We describe preliminary laboratory results for the various systems, discuss initial background simulations, and describe our plans for balloon flight tests. PREPRINT

The ISOCAM/LW Detector Dark Current Behaviour Biviano A Sauvage M Gallais P Boulade O Román P Guest S Okumura K Ott S 1999 We describe the calibration, measurements and data reduction, of the dark current of the ISOCAM/LW detector. We point-out the existence of two significant drifts of the LW dark-current, one throughout the ISO mission, on a timescale of days, another within each single revolution, on a timescale of hours. We also show the existence of a dependence of the dark current on the temperature of the ISOCAM detector. By characterizing all these effects through polynomial fittings, we build a model for the LW calibration dark, that depends on the epoch of observation (parametrized with the revolution number and the time elapsed in that given revolution since the activation) and on the temperature of the ISOCAM detector. The model parameters are tuned for each of ISOCAM/LW pixel. We show that the modelling is very effective in taking into account the dark-current variations and allows a much cleaner dark subtraction than using a brute average of several calibration dark images. The residuals of the LW model-dark subtraction are, on average, similar to the pre-launch expectation. PREPRINT

The Implications of Galaxy Formation Models for the TeV Observations of Current Detectors Boone L M Bullock J S Primack Joel R Williams D A 1999 This paper represents a step toward constraining galaxy formation models via TeV gamm a ray observations. We use semi-analytic models of galaxy formation to predict a spectral distribution for the intergalactic infrared photon field, which in turn yields information about the absorption of TeV gamma rays from extra-galactic sources. By making predictions for integral flux observations at >200 GeV for several known EGRE T sources, we directly compare our models with current observational upper limits obtained by Whipple. In addition, our predictions may offer a guide to the observing programs for the current population of TeV gamma ray observatories. PREPRINT

Neutral kaons as instrument for studying heavier fkavors Azimov Ya I 2001 Strangeness oscillations in decays of neutral kaons are suggested to be used as an analyzer to investigate detailed properties of heavy flavor hadrons and their decays. Here we briefly explain why, where, and to what problems this approach may be applied. research-article

2.4 - 197 micron spectroscopy of OH/IR stars Sylvester R J Kemper F Barlow M J De Jong T Waters L B F M Tielens A G G M Omont A 1999 Infrared spectra of a number of evolved O-rich stars have been obtained with the Short- and Long- Wavelength spectrometers on board the Infrared Space Observatory. The very broad wavelength coverage (2.4-197 micron) obtained by combining observations made with the two spectrometers includes practically all of the flux emitted by the sources, and allows us to determine the emission and absorption features of the dense circumstellar dust shells. Agreement between the fluxes obtained by the two instruments is generally very good; the largest discrepancies are probably due to source variability. Our sample of oxygen-rich AGB stars exhibits a wealth of spectral features due to crystalline silicates and crystalline water ice in emission and absorption. In this study a qualitative overview of all features due to crystalline silicates and water ice in these high mass loss rate objects is presented. It seems that there is a certain onset value for the mass loss rate above which these features appear in the spectrum. Moreover, crystalline silicate emission features have been detected for the first time at wavelengths where the amorphous silicates are still in absorption, implying different spatial distributions for the two materials. A spherically symmetric and an axi-symmetric geometry are proposed. PREPRINT

Phys. Rev. A Phys. Rev. A How useful is Detector Cascading? Kok P Braunstein S L 2001 63 Detector cascading provides us with a Rosetta Stone, relating detectors with single-photon resolution to detectors with single-photon sensitivity but no resolution. Most standard realistic detectors lack single-photon resolution. Detector cascading always improves the resolution of any set of detectors. We introduce the confidence of an event, which quantifies the level of certainty that upon an n-fold detector coincidence in the cascade there were exactly n photons present. Although theoretically detector cascading connects detectors with single-photon resolution to standard detectors, our results suggest that currently real single-photon resolution detectors are superior to detector cascading with standard detectors. research-article

Nanomechanical resonators operating as charge detectors in the nonlinear regime Kroemmer H Erbe A Tilke A Manus S Blick R H 1999 We present measurements on nanomechanical resonators machined from Silicon-on-Insulator substrates. The resonators are designed as freely suspended Au/Si beams of lengths on the order of 1 - 4 um and a thickness of 200 nm. The beams are driven into nonlinear response by an applied modulation at radio frequencies and a magnetic field in plane. The strong hysteresis of the magnetomotive response allows sensitive charge detection by varying the electrostatic potential of a gate electrode. PREPRINT

Measurement of neutrino oscillations by means of a high density detector on the atmospheric neutrino beam Aglietta M Ambrosio M Aprile E Bologna G Bonesini M Bencivenni G Calvi M Castellina A Curioni A Fulgione W Ghia P L Gustavino C Kokoulin R P Mannocchi G Murtas F Murtas G P Negri P Paganoni M Periale L Petrukhin A A Picchi P Pullia Antonio Ragazzi S Redaelli N G Satta L Tabarelli de Fatis T Terranova F Tonazzo A Trinchero G C Vallania P Villone B 1999 A high-density calorimeter, consisting of magnetized iron planes interleaved by RPCs, as tracking and timing devices, is a good candidate for a next generation experiment on atmospheric neutrinos. With 34 kt of mass and in four years of data taking, this experiment will be sensitive to $\nu_\mu \to \nu_x$ oscillation with $\Delta m^2 > 6 \times 10^{-5}$ and mixing near to maximal and fully cover the region of oscillation parameters suggested by Super-Kamiokande results. Moreover, the experimental method will enable to measure the oscillation parameters from the modulation of the L/E spectrum ($\nu_\mu$ disappearance). For $\Delta m^2 > 3 \times 10^{-3}$ eV$^2$, this experiment can also establish whether the oscillation occurs into a tau or a sterile neutrino, by looking for an excess of muon-less events at high energies produced by upward-going tau neutrinos ($\nu_\tau$ appearance). PREPRINT

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IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 A Mole for Warm Magnetic and Optical Measurements of LHC Dipoles Bottura L Buzio M Deferne G Glöckner C Jansen H Köster A Legrand P Rijllart A Sievers P 2000 10 1454 7 A new rotating coil probe (a mole) has been developed for the simultaneous measurement of the magnetic field and magnetic axis of warm superconducting LHC dipoles and associated corrector windings. The mole houses a radial rotating coil and travels inside the magnet aperture by means of an externally driven two-way traction belt. The coil is rotated by an on-board piezo motor, being tested in view of future devices for cold measurements as the only type of motor compatible with strong magnetic fields. A virtual light spot is generated in the coil center by a LED source. The position of this light spot is measured from the outside by a system including a telescope, a CCD camera and a DSP. Jigs on reference granite tables are used to transfer the optical measurements to the magnet fiducials. We describe here the main characteristics and performance of the mole research-article

Nucl. Instrum. Methods Phys. Res., A Nucl. Instrum. Methods Phys. Res., A 0167-5087 Performance of the CLEO III LiF-TEA Ring Imaging Cherenkov Detector in a High Energy Muon Beam Artuso M Ayad R Azfar F Efimov A Kopp S E Mountain R Majumder G Schuh S Skwarnicki T Stone S Viehhauser G Wang J C Coan T E Fadeev V Volobuev I P Ye J Anderson S Kubota Y Smith A Lipeles E 2000 441 374 392 The CLEO III Ring Imaging Cherenkov detector uses LiF radiators to generate Cherenkov photons which are then detected by proportional wire chambers using a mixture of CH$_4$ and TEA gases. The first two photon detector modules which were constructed, were taken to Fermilab and tested in a beam dump that provided high momentum muons. We report on results using both plane and "sawtooth" shaped radiators. Specifically, we discuss the number of photoelectrons observed per ring and the angular resolution. The particle separation ability is shown to be sufficient for the physics of CLEO III. research-article

First measurement of $\Re(\epsilon'/ \epsilon)$ with the NA48 detector at CERN Mazzucato E CERN 2000 research-article

Chandra Detection of Massive Black Holes in Galactic Cooling Flows Brighenti Fabrizio University of California, Santa Cruz, CA and Dipartimento di Astronomia, Universita di Bologna Mathews W G 1999 Anticipating forthcoming observations with the Chandra X-ray telescope, we describe the continuation of interstellar cooling flows deep into the cores of elliptical galaxies. Interstellar gas within about r = 50 parsecs from the massive black hole is heated to T > 1 keV and should be visible unless thermal heating is diluted by non-thermal pressure. Since our flows are subsonic near the massive black holes, distributed cooling continues within 300 pc from the center. Dark, low mass stars formed in this region may be responsible for some of the mass attributed to central black holes. PREPRINT

The Angular Resolution of Space-Based Gravitational Wave Detectors Moore T A Hellings R W 1999 Proposed space-based gravitational wave antennas involve satellites arrayed either in an equilateral triangle around the earth in the ecliptic plane (the ecliptic-plane option) or in an equilateral triangle orbiting the sun in such a way that the plane of the triangle is tilted at 60 degrees relative to the ecliptic (the precessing-plane option). In this paper, we explore the angular resolution of these two classes of detectors for two kinds of sources (essentially monochromatic compact binaries and coalescing massive-black-hole binaries) using time-domain expressions for the gravitational waveform that are accurate to 4/2 PN order. Our results display some interesting effects not previously reported in the literature, and particularly underline the importance of including the higher-order PN terms in the waveform when predicting the angular resolution of ecliptic-plane detector arrays. PREPRINT

Nucl. Phys. A Nucl. Phys. A New experimental data for the decays $\phi \to \mu^{+}\mu^{-}$ and $\phi \to \pi^{+}\pi^{-}$ from SND detector Achasov M N Aulchenko V M Beloborodov K I Berdyugin A V Bozhenok A V Bukin D A Burdin S V Dimova T V Dolinski S I Drozdetsky A A Druzhinin V P Dubrovin M S Gaponenko I A Golubev V B Ivanchenko V N Ivanov P M Korol A A Koshuba S V Kukartsev G A Nesterenko I N Otboev A V Pakhtusova E V Popov V M Salnikov A A Serednyakov S I Shary V V Shatunov Yu M Sidorov V A Silagadze Z K Usov Yu V Zakharov A S 2000 675 320 324 The processes $e^+e^-\to\mu^+\mu^-$ and $e^+e^-\to\pi^+\pi^-$ have been studied with SND detector at VEPP-2M $e^+e^-$ collider in the vicinity of 0.45\pm 0.32)\times 10^{-4}$ and $B(\phi\to\pi^+\pi^-)=(0.71\pm 0.11\pm 0.09)\times 10^{-4}$ were obtained. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Accurate Calculation of Fringe Fields in the LHC Main Dipoles Kurz S Russenschuck Stephan Siegel N 2000 10 85 8 The ROXIE program developed at CERN for the design and optimization of the superconducting LHC magnets has been recently extended in a collaboration with the University of Stuttgart, Germany, with a field computation method based on the coupling between the boundary element (BEM) and the finite element (FEM) technique. This avoids the meshing of the coils and the air regions, and avoids the artificial far field boundary conditions. The method is therefore specially suited for the accurate calculation of fields in the superconducting magnets in which the field is dominated by the coil. We will present the fringe field calculations in both 2d and 3d geometries to evaluate the effect of connections and the cryostat on the field quality and the flux density to which auxiliary bus-bars are exposed. research-article

Optimization of operation and test of large size GEM detectors Bachmann S Physikalisches Institut, RWTH Aachen, Germany Bressan A Placci Alfredo Ropelewski Leszek Sauli Fabio 1999 We describe basic development work aimed at the realization of large (~1000 cm2 active) detectors for the COMPASS experiment, based on the gas electron multiplier technology. Essentially a high-rate forward spectrometer, the experiment requires high accuracy tracking of scattered particles and light detectors, in order not to degrade mass resolution and particle identification. The choice of a double GEM structure with two-coordinate read-out fulfils the above requirements. Systematic studies confirm the required performances, with good safety margins for an operation in harsh environments. We discuss the design problems encountered in the construction of the large devices and the solutions adopted, together with preliminary results obtained with prototypes in the laboratory and in a high intensity beam. PREPRINT

Micro-pattern gas detectors Sauli Fabio 2001 Micro-strip gas chambers, with their excellent localization properties, high rate capability and good granularity, have been adopted by many experiments in particle physics. Two recurrent problems however have been reported: a slow degradation under sustained irradiation (or aging), and the rare but devastating occurrence of discharges. New breeds of detectors aim at improving on these crucial points, the micro-dot, CAT, micromegas, the gas electron multiplier are examples. Very performing, they are moreover robust and reliable. Two-stage devices, making use of a gas electron multiplier as first element, permit larger gains in presence of high rates and heavily ionizing tracks. Possible promising future developments in the field are outlined. research-article

AIP Conf. Proc. AIP Conf. Proc. RICH detectors Nappi E 2000 536 60 86 Basic principles of the Ring Imaging CHerenkov (RICH) technique are given, the issues of designing devices based on such a technique and the factors which limit the particle discriminating power are discussed. The challenging designs adopted by current experiments are also reviewed. research-article

Two Coupled Superconducting Cavities as a Gravitational Wave Detector Bernard P. CERN Gemme G. INFN, Genoa Parodi R. INFN, Genoa Picasso E. Pisa, Scuola Normale Superiore 1999 First experimental results of a feasibility study of a gravitational wave detector based on two coupled superconducting cavities are presented. Basic physical principles underlying the detector behaviour and sensitivity limits are discussed. The detector layout is described in detail and its rf properties are showed. The limit sensitivity to small harmonic displacements at the detection frequency (around 1 MHz) is showed. The system performance as a potential g.w. detector is discussed and future developments are foreseen. PREPRINT

W W cross section and W branching ratios at $\sqrt{s}=183$ GeV Pérez P CERN 1998 Measurement of WW cross section and W branching ratios at LEP2 with the ALEPH detector W pair production cross-section is measured at LEP2 with the ALEPH detector. W decay branching ratios and the |V_cs| element of the CKM matrix are derived. The agreement of the cross-section with the Standard Model prediction allows a limit to be set on the W decay rate to invisible decays. PREPRINT

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High resolution calorimetric low temperature detectors for applications in atomic and nuclear physics Egelhof P 1999 PREPRINT

Study of the charge multiplication phenomenon is silicon epitaxial detector Sobolev Yu G Kushniruk V F Bialkowska E Khlebnikov S Yu Penionzhkevich Yu E Trzaska W H 1999 PREPRINT

Deposit of isotopically modified Gadolinium suitable to detect solar neutrinos Cribier Michel 1999 PREPRINT

The Capabilities of the Alpha Magnetic Spectrometer as GeV $\gamma$-ray detector Battiston R 1999 The modeled performance of the Alpha Magnetic Spectrometer (AMS) as a high-energy (0.3 to 100 GeV) gamma-ray detector is described, and its gamma-ray astrophysics objectives are discussed. PREPRINT

Phys. Lett. B Phys. Lett. B On Wigner's clock and the detectability of spacetime foam with gravitational-wave interferometers Ng Y J Van Dam H 2000 477 429 435 A recent paper (gr-qc/9909017) criticizes our work on the structure of spacetime foam. Its authors argue that the quantum uncertainty limit for the position of the quantum clock in a gedanken timing experiment, obtained by Wigner and used by us, is based on unrealistic assumptions. Here we point out some flaws in their argument. We also discuss their other comments and some other issues related to our work. We see no reason to change our cautious optimism on the detectability of spacetime foam with modern gravitational-wave interferometers like LISA. research-article

Resonant Spheres Serrano M A Lobo J A 1999 We discuss the capabilities of spherical antennæ as single multifrequency detectors of gravitational waves. A first order theory allows us to evaluate the coupled spectrum and the resonators readouts when the first and the second quadrupole bare sphere frequencies are simultaneously selected for layout tuning. We stress the existence of non-tuning influences in the second mode coupling causing draggs in the frequency splittings. These URF effects are relevant to a correct physical description of resonant spheres, still more if operating as multifrequency appliances like our PHCA proposal. PREPRINT

A detector for precision study of high energy $e^{+}e^{-}$ annihilations Burrows P N 2000 The status of the design of a detector for the TESLA collider is presented. research-article

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IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Measurement and Analysis of Axial End Forces in a Full-Length Prototype of LHC Main Dipole Magnets Artoos K Kurtyka T Savary F Valbuena R Vlogaert J 2000 10 69 72 A full-length, twin aperture prototype (MBP2N1) dipole magnet for the LHC project was assembled at CERN with collared coils delivered by industry. The design of this prototype is close to that foreseen for the dipole series manufacture as far the coil geometry and that of the yoke components are concerned. The bolts that transfer the axial magnetic forces from the coil ends to the cold mass end plates were instrumented to verify the axial coil support. These axial forces were initially measured after partial assembly, during a standard and an accelerated cool down Introduction to 1.9 K, and during magnet excitation up to 9.2 T. High force levels were observed, triggering a comparison with analytical models and measurements routinely made on 1-m single aperture dipole models. The prototype magnet was re-assembled with lower initial axial force settings and with additional instrumentation, to monitor these forces during the entire assembly process, and re-tested, to possibly correlate axial forces with training behaviour. This paper reports about the experimental observations and provides models towards their understanding research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Statistical Studies of the Robustness of the LHC Main Dipole Mechanical Structure Bajko M Fessia P Perini D 2000 10 77 80 This paper describes two methods used to study the effect of the tolerances of the components on the structure of the LHC main dipole. The first method, called semi-statistical, is useful for the study of the effect of single different parameters and allows the determination of the acceptable variance of the dimensions of magnet components. The second one, fully statistical, allows the study of the combined effect of many parameters. The use of these two methods allowed to evaluate with good confidence the robustness of two different dipole cross-section designs, featuring austenitic and aluminium alloy collars, respectively. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 FEM Computations Concerning the Effect of Friction in Two LHC Main Dipole Structures Bajko M Fessia P Perini D 2000 10 81 4 The mechanical behaviour of a dipole structure is considered when also friction is taken into account, studying its effect on different components and in different conditions. In particular the difference in behavior between a structure with aluminium collars and one with austenitic steel ones was studied. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Localization of Electrical Insulation Failures in Superconducting Collared Coils by Analysis of the Distortion of a Pulsed Magnetic Field Komorowski P A Tommasini D 2000 10 166 9 The localization of possible electrical faults in superconducting accelerator magnets may, in most cases, be a complex, expensive and time-consuming process. In particular, inter-turn short circuits and failures of the ground insulation are well detectable when the magnet is collared, but often disappear after disassembly for repair due to the release of the pre-stress in the coils. The fault localization method presented in this paper is based on the measurement and analysis of the magnetic field generated inside the magnet aperture by a high voltage pulse. The presence of the fault modifies the distribution of the current in the coils and produces a distortion of the magnetic field. The described method aims at locating both the longitudinal and azimuthal position of the fault-affected area. The test method, the transient case FEM models and the implemented experimental set-up are presented and discussed for the LHC dipole models. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Measurement of Superconducting Busbars Models for the LHC Main Dipole Le Coroller A Derégel J Henrichsen K N Hervieu M Juster F P Perinet-Marquet J L Vlogaert J 2000 10 1118 21 The LHC main dipoles will be connected in series by superconducting busbars, consisting of a superconducting cable brazed onto a stabilizing copper profile. In case of a quench detection, protection heaters will be activated to drive the magnet to theresistive state. In addition, the magnet will be protected by a bypass diode. In order to limit quench propagation, the excitation current is ramped down at an initial rate of 113 A/s and with a time constant equal to 104 s. When a busbar quenches, its temperature must stay below safe values. Comparative measurements of a hollow and a solid busbar were performed in 1.9 K superfluid helium, 4.2 K liquid helium and 4.2 K gaseous helium during the current ramp down. We describe the experimental set-up and report the results. The development of temperatures, the quench propagation velocities as well as the residual resistance ratio (RRR) were measured. The busbar stabilized by a solid copper profile was found to be the most appropriate choice. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Random Errors induced by the Superconducting Windings in the LHC Dipoles Scandale Walter Todesco Ezio Wolf R 2000 10 93 7 The problem of estimating the random errors in the LHC dipole is considered. The main contributions to random errors are due to random displacements of the coil position with respect to nominal design and to the variation of the magnetization of the superconducting cable. Coil displacements can be induced either by mechanical tolerances or by the manufacturing process. Analytical and numerical scaling laws that provide the dependence of the random errors due to random displacements on the multipolar order are worked out. Both simplified and more realistic models of the coil structure are analysed. The obtained scaling laws are used to extract from experimental field shape data the amplitude of the coil displacements in the magnet prototypes. Finally, random errors due to interstrand resistance variation during the ramp are estimated research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Design, Manufacturing Status, First Results of the LHC Main Dipole Final Prototypes and Steps towards Series Manufacture Artoos K Bottura L Fessia P Bajko M Modena M Pagano O Perini D Savary F Scandale Walter Siemko A Spigo G Todesco Ezio Vlogaert J Wyss C 2000 10 98 102 This paper reports about the program of six LHC superconducting main dipole final prototypes and the steps towards series manufacture. The above program, launched in summer 1998, relies on collared coils manufactured by industry and cold masses assembled at the CERN Magnet Assembly Facility. Following design, stability and robustness studies, the magnet design for series manufacture features a "6-block" coil and austenitic steel collars. A general description of the magnet with its main components is given and the main working parameters and the most important manufacturing features are presented. Results of mechanical and magnetic measurements are given as well as the performances of the first prototype. A comparison with results from the previous generation of dipole magnet models and prototypes is also made. Finally an outlook towards series manufacture is given. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Selection of the Cross-Section Design for the LHC Main Dipole Fessia P Perini D Russenschuck Stephan Völlinger C Vuillermet R Wyss C 2000 10 65 8 With the aim of selecting the most suitable design for the series production of the LHC main dipoles, several possible configurations were analysed with respect to admissible component tolerances and structural stability, field level, field quality, number and weight of parts. Two alternatives designs, featuring common collars made out of aluminium alloy and austenitic steel, respectively, were finally compared in detail. Although both designs are almost equivalent at nominal conditions, the austenitic steel collar structure turned out to be far less sensitive to components dimensional variations. This paper reports the main results of the above evaluations, which lead to the choice of austenitic steel collars for the LHC main dipoles. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Status of the Short Dipole Model Program for the LHC Artoos K Bottura L Fessia P Perini D Sanfilippo S Siegel N Siemko A Tommasini D Vanenkov I Walckiers L Wyss C 2000 10 49 52 The model program for the LHC main dipoles is dedicated to the study and validation of design variants and assembly parameters to achieve reproducible performance and optimise components and assembly costs. The topics investigated in the last year include the material of the coil end spacers, the use of polyimide films from different manufacturers, the definition of optimum azimuthal and longitudinal coil pre-stress values, shimming of coil ends, collaring around the "cold bore" and different layouts of the yoke ends. This paper presents the main characteristics of such recent models, the results obtained during cold tests and the plans for the final phase of the model program for the LHC dipoles. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Design and Manufacture of a Large-Bore 10 T Superconducting Dipole for the CERN Cable Test Facility Leroy D Spigo G Verweij A P Boschmann H Dubbeldam R L González-Pelayo J 2000 10 178 82 A large-bore 10 T superconducting dipole magnet was designed and fabricated in close cooperation between CERN and HMA Power Systems. The dipole has a length of about 1.7 m and an aperture of 88 mm and is composed of two two-layer poles wound with NbTi cables cooled to 1.9 K to reach magnetic inductions close to 10 T. This dipole will be installed at the CERN cable test facility and used as a background field magnet to test LHC superconducting cables. In its large aperture up to four cable samples can be tested at the same time. The mechanical design of the magnet is such that coil prestress variations between warm and cold conditions are kept within 20 MPa. A short model was also built and cooled down in order to check and confirm with test results the mechanical behavior of the dipole. Magnetic measurements, at room temperature, were performed upon its arrival at CERN prior to installation in the test facility. The dipole was recently cooled down and tested. This paper will discuss the design, the main manufacturing steps and the initial test results. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Influence of Mechanical Tolerances on Field Quality in the LHC Main Dipoles Scandale Walter Todesco Ezio Tropea P 2000 10 73 6 We evaluate the influence of mechanical tolerances on the field quality in the LHC dipoles. We show that the most relevant effect is due to tolerances on the coil and on the internal part of the collars. The sensitivities of the field error multipoles on the mechanical tolerances are worked out using a finite element model of the dipole cross section. A MonteCarlo method is used to simulate the overall effect of both collar and coil tolerances on field quality. Correlation between random multipoles is worked out, and a comparison with the target table of the LHC field errors is given. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Analysis of Warm Magnetic Measurements in a LHC Main Dipole Prototype Gleis S Miles J Pagano O Scandale Walter Todesco Ezio 2000 10 1439 42 The data relative to the magnetic measurements at room temperature of the MBP2N1 prototype of the LHC dipole are presented. The measured field harmonics are compared to the results of the numerical model of the dipole cross section. The contribution from different effects are evaluated and compared to experimental data. Relevant quantities on the mechanical structure and on the expected field quality are worked out. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Further Development of the Sextupole and Decapole Spool Corrector Magnets for the LHC Allitt M Bapna S Ijspeert Albert Karmarkar M Karppinen M Mazet J Pérez J Puntambekar A Ruwali K Salminen J Thipsay A 2000 10 162 5 In the Large Hadron Collider (LHC) the main dipoles will be equipped with sextupole (MCS) and decapole (MCD) spool correctors to meet the very high demands of field quality required for the satisfactory operation of the machine. Each decapole corrector will in addition have an octupole insert (MCO) and the assembly of the two is designated MCDO. These correctors are needed in relatively large quantities, i.e. 2464 MCS Sextupoles and 1232 MCDO Decapole-Octupole assemblies. Half the number of the required spool correctors will be made in India through a collaboration between CERN and CAT (Centre for Advanced Technology, Indore, India), the other half will be built by European industry. The paper describes final choices concerning design, materials, production techniques, and testing so as to assure economic magnet manufacture but while maintaining a homogenous magnetic quality that results in a robust product. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Temperature Profiles During Quenches in LHC Superconducting Dipole Magnets Protected by Quench Heaters Maroussov V Sanfilippo S Siemko A 2000 10 661 4 The efficiency of the magnet protection by quench heaters was studied using a novel method which derives the temperature profile in a superconducting magnet during a quench from measured voltage signals. In several Large Hadron Collider single aperture dipole models, temperature profiles and temperature gradients in the magnet coil have been evaluated in the case of protection by different sets of quench heaters and different powering and protection parameters. The influence of the insulation thickness between the quench heaters and the coil has also been considered. The results show clear correlation between the positions of quench heaters, magnet protection parameters and temperature profiles. This study allowed a better understanding of the quench process mechanisms and the efficiency assessment of the different protection schemes. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 A Practical Fit for the Critical Surface of NbTi Bottura L 2000 10 1054 7 Known expressions for the critical temperature, critical field and Pinning force in NbTi are combined into a self-consistent fit formula that provides the critical current density as a function of temperature and field. The main advantage of such a fit is the extended validity range. Data available in literature and measurements on LHC strands are used to demonstrate the accuracy of the fit. The Jc data-sets used to cover a range of field from 0 T to 9 T and temperature from 1.9 K to 9 K. The standard deviation of the fits presented is of the order of 5 % or better. This accuracy is generally sufficient for design purposes, extrapolation and scaling of measured results. Better accuracy, e.g. for short sample limit prediction, can be achieved restricting the domain of validity. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Coil Size and Geometric Field Quality in Short Model Dipoles for LHC Ang Z Bottura L Russenschuck Stephan Siemko A Tommasini D Walckiers L 2000 10 53 6 We have measured the magnetic field at room temperature and at 1.8 K on more than twenty, 1-m long, single aperture LHC superconducting dipole models. The magnets feature either a 5-block coil geometry or the baseline 6-block geometry foreseen for the LHC. Comparison of warm and cold measurements show that the coil geometry is essentially unchanged during cooldown. We have therefore used mechanical measurements taken on the coil and collars during assembly to estimate the azimuthal coil length. Based on these measurements we show here that the sensitivity of allowed harmonics on coil size is in good agreement with the prediction obtained from the numerical model used for designing the LHC magnets. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Twin Rotating Coils for Cold Magnetic Measurements of 15 m Long LHC Dipoles Billan J Bottura L Buzio M D'Angelo G Deferne G Dunkel O Legrand P Rijllart A Siemko A Sievers P Schloss S Walckiers L 2000 10 1422 6 We describe here a new harmonic coil system for the field measurement of the superconducting, twin aperture LHC dipoles and the associated corrector magnets. Besides field measurements the system can be used as an antenna to localize the quench origin. The main component is a 16 m long rotating shaft, made up of 13 ceramic segments, each carrying two tangential coils plus a central radial coil, all working in parallel. The segments are connected with flexible Ti-alloy bellows, allowing the piecewise straight shaft to follow the curvature of the dipole while maintaining high torsional rigidity. At each interconnection the structure is supported by rollers and ball bearings, necessary for the axial movement for installation and for the rotation of the coil during measurement. Two such shafts are simultaneously driven by a twin-rotating unit, thus measuring both apertures of a dipole at the same time. This arrangement allows very short measurement times (typically 10 s) and is essential to perform cold magnetic measurements of all dipoles. The coil surface and direction are calibrated using a reference dipole. In this paper we describe the twin rotating coil system and its calibration facility, and we give the typical resolution and accuracy achieved with the first commissioned unit. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 A Fast Sextupole Probe for Snapback Measurement in the LHC Dipoles Bottura L Larsson L Schloss S Schneider M Smirnov N Haverkamp M 2000 10 1435 8 In superconducting particle accelerators a fast change of the magnetic field occurs during the first few seconds after the start of an energy ramp. Standard magnetic measurements using a coil rotating at 1 Hz do not have the time resolution required to completely resolve this phase, usually called snapback. For this reason we have developed a new and fast system dedicated to sextupole measurements. The basic component consists of three Hall plates mounted on a ring. In an ideal case this arrangement compensates the main dipole field and produces a signal proportional to the sextupole only. Mechanical tolerances and differences in the sensitivity of the Hall plates are compensated by instrumentation amplifiers and an in situ fine adjustment of the probe orientation. Using this hybrid compensation technique we have measured sextupole variations in an LHC dipole prototype during snapback at a rate of 5 Hz. In this paper we present details on the device and the results of our measurements. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Design and Fabrication of a 1 m Model of the 70 mm Bore Twin Aperture Superconducting Quadrupole for the LHC Insertions Kirby G A Lucas J MacKay R S Nobes S C Ostojic R Treadgold J R 2000 10 61 4 For reasons of geometrical acceptance, 70 mm bore twin aperture quadrupoles are required in the LHC insertions. For an operating gradient of 160 T/m at 4.5 K, a design based on a four layer coil wound from two graded 8.2 mm NbTi conductors has been developed. Three 1 m single aperture quadrupoles of this design have been built and successfully tested. Thereafter, the magnets have been disassembled and the coils re-collared using self-supporting collars. In this paper, we describe the design features of the twin aperture quadrupole, and report on the initial collaring tests and procedures for collaring and final assembly of the 1 m magnet. research-article

IEEE Trans. Appl. Supercond. IEEE Trans. Appl. Supercond. 1051-8223 Further Development of the Sextupole Dipole Corrector (MSCB) Magnet for the LHC Ang Z Arshad S A Bajko M Bottura L Coxill D Giloux C Ijspeert Albert Karppinen M Landgrebe D Walckiers L 2000 10 158 61 Combined sextupole-dipole corrector magnets (MSCB) will be mounted in each half cell of the new Large Hadron Collider (LHC) being built at CERN. The dipole part, used for particle orbit corrections, will be powered individually and is designed for low current, originally 30 A but now 55 A. The sextupole part, used for chromaticity corrections, is connected via cold busbars in families of 12 or 13 magnets and is powered with 550 A. Several versions of this corrector magnet were tested as model magnets in order to develop the final design for the series. In the first design the coils are nested, with the dipole coil wound around the sextupole coil to obtain as short a magnet as possible, accepting the slight cross-talk between the coils due to persistent currents, and increased saturation effects. The design has evolved and an alternative design, in which the dipole and sextupole coils are separated, is now favored. Tests at 4.5 K and at 1.9 K were conducted to determine the training behavior, the field quality, and the cross-talk between the windings. This paper discusses the results for the different configurations. research-article