Technological Developments at CERN in 1999
Accelerator Technology
Subject:Radiofrequency gun electron sources
Collaborator:Paul Scherrer Institute (CH)
Contacts:P.Pearce, L.Rinolfi & B.Allardyce/CERN–PS
Reference:Collaboration agreement No.K 226/PS
Production of two 35MW RF sources (one for PSI, one for CERN). Investigate possible performance limits of both thermionic and photocathode RF guns.
Subject:Tests on NbTi wires
Collaborator:Technical University of Vienna (Exp. Physics Inst.) (AT)
Contacts:L.Oberli & P.Bernard/CERN–LHC
Measurement of the critical current and the magnetization between 4.2K and 2K in order to qualify the production of superconducting NbTi wires supplied by various European firms engaged in the R&D work for the LHC superconducting cables.
Subject:Niobium superconducting cavities
Collaborator:INFN Legnaro (IT)
Contacts:E.Chiaveri & G.Roy/CERN–SL
Reference:Agreement No.K 141/AC
Common development of technology for all-niobium superconducting cavities.
Subject:Surface preparation of niobium superconducting cavities
Collaborator:INFN Legnaro (IT)
Contact:E.Chiaveri/CERN–SL
Reference: Agreement No.K 462/SL
Surface preparation of twenty niobium superconducting cavities for heavy-ion application (ALPI project).
Subject:Fabrication of two single-cell superconducting cavities
Collaborator:CEA Saclay (FR)
Contacts:E.Chiaveri & G.Roy/CERN–SL
Reference:Agreement No.K 425/SL
Fabrication of two single cells (352MHz) on Nb/Cu for the SOLEIL project.
Subject:RF measurements of single-cell superconducting cavities
Collaborator:ACCEL (DE)
Contacts:E.Chiaveri & G.Roy/CERN–SL
Reference:Agreement No.K 467/SL
RF measurements of single-cell Nb/Cu (600MHz) in the framework of common collaboration for future high-intensity proton linac application.
Subject:Power coupler with adjustable coupling factor for superconducting accelerator cavities
Contacts:G.Roy, E.Haebel/CERN–SL, H.Vogel, D.Kiehlmann, P.Schafer & I.Mcgill/CERN–EP
An accelerator includes a beam tube having a cavity with a central axis along which particles can be accelerated. A radio-frequency power coupling device couples the cavity to a high-frequency power source. The coupling device includes a coaxial waveguide having a central axis, an outer conductor and an inner conductor. The outer conductor is fixed relative to the cavity defining an angle between the central axis of the cavity and the central axis of the coaxial waveguide. An external drive moves the inner conductor along the central axis of the coaxial waveguide.
Subject:Neutron-driven element transmuter
Contacts:C.Rubbia & J.-P.Revol/CERN–EP
A material is exposed to a neutron flux by distributing it in a neutron-diffusing medium surrounding a neutron source. The diffusing medium is transparent to neutrons and so arranged that neutron scattering substantially enhances the neutron flux to which the material is exposed. Such enhanced neutron exposure may be used to produce useful radio-isotopes, in particular for medical applications, from the transmutation of readily available isotopes included in the exposed material. It may also be used to efficiently transmute long-lived radioactive wastes, such as those recovered from spent nuclear fuel. The use of heavy elements, such as lead and/or bismuth, as the diffusing medium is particularly of interest, since it results in a slowly decreasing scan through the neutron energy spectrum, thereby permitting very efficient resonant neutron captures in the exposed material.
Subject:Semiconductor switch for LHC beam dumping
Collaborators:ABB (CH) (CH), Mittel (CA) & Westcode (UK)
Contacts:E.Vossenberg & G.Roy/CERN–SL
A fast high-power semiconductor switch (35kV, 2kA, 3micros rise time) will be used to pulse the LHC beam dump kicker magnets. The switch consists of a stack of ten modified gate turn-off (GTO) thyristors.
Subject:Chemical treatment of two 80MHz, niobium, radio-frequency quadrupoles
Collaborator:INFN Legnaro (IT)
Contacts:E.Chiaveri & G.Roy/CERN–SL
The chemical treatment of two 80MHz, niobium, radio-frequency quadrupoles.
Subject:Chemical treatment of 20quarter-wave resonators
Collaborator:INFN Legnaro (IT)
Contacts:E.Chiaveri & G.Roy/CERN–SL
The chemical treatment of 20quarter-wave resonators.
Subject:Production and test of a multicell reduced-beta cavity
Collaborator:INFN Milano (IT)
Contacts:E.Chiaveri & G.Roy/CERN–SL
The production and test of a multicell reduced-beta cavity (five cells, beta = 0.85, 350MHz) and for the chemical treatment and test of a single-cell beta = 0.5niobium cavity.
Subject:RF test of a single-cell beta = 0.8, 600MHz cavity
Collaborator:ACCEL (DE)
Contacts:E.Chiaveri & G.Roy/CERN–SL
The RF test of a single-cell beta = 0.8, 600MHz cavity produced by the collaborating firm, with advice from CERN.
Subject:Ferroelectric electron emission
Collaborators:Instituto Politecnico di Milano (IT), University of Katowice (PL), University of Milano (IT), Thomson-CSF, Central Research Lab, Orsay (FR) & Technical University of Berlin, Inst. of Theoretical Electrotechnics (DE)
Contact:H.Riege/CERN–LHC
Ferroelectric material is spontaneously polarising. The spontaneous electric polarisation field Ps of a ferroelectric layer is generally screened by charges on the surface. By a rapid change of Ps apparent surface charge densities of the order of 1Cb/m2 can be induced in certain ferroelectrics, high enough to generate electric surface fields and potential differences sufficient for pulsed electron (‘self’) emission without external extraction voltage. Hence, ferroelectric electron emission differs from conventional electron emission methods, which can yield a finite electron current only by means of an external extraction field.
Subject:Pseudo-spark switches
Collaborators:University of Erlangen (DE), Thomson-CSF, Central Research Lab., Orsay (FR) & Thomson-Short Systems, Bagneux (FR)
Contacts:H.Riege/CERN–LHC
The pseudo-spark is a low-pressure gas discharge on the left branch of the Paschen breakdown curve. It occurs in a geometrical arrangement with hollow electrodes, which are perforated with one or more axially symmetrical holes, through which the main discharge plasma communicates with the interior of the hollow electrodes. The pseudo-spark discharge can be efficiently triggered with nanosecond precision from the hollow cathode hole. This feature allows the application of pseudo-spark discharge devices as powerful cold-cathode, high-current, high-voltage switches.
Subject:Energy Amplifier
Contacts:C.Rubbia & J.-P.Revol/CERN–EP
A method for producing energy from a nuclear fuel material contained in an enclosure, through a process of breeding of a fissile element from a fertile element of the fuel material via a b-precursor of the fissile element and fission of the fissile element. A high-energy particle beam is directed into the enclosure for interacting with heavy nuclei contained in the enclosure so as to produce high-energy spallation neutrons. The neutrons thereby produced are multiplied in steady sub-critical conditions by the breeding and fission process. The breeding and fission process is carried out inside the enclosure.
Subject:Phase space tomography
Contact:S.Hancock/CERN–PS
One of the simplest tomography algorithms has been modified to take into account the non-linearity of large-amplitude synchrotron motion. This permits the accurate reconstruction of the density in longitudinal phase space of particles in a synchrotron from one-dimensional bunch profile data.
Controls
Subject:Four-quadrant power converter
Collaborator:LEEI/ENSEEIHT, Toulouse (FR)
Contacts:G.Roy, F.Bordry & A.Dupaquier/CERN–SL
The LHC machine will make extensive use of true bipolar power converters which will be installed underground leading to the necessity for reduced volume and high efficiency for the power converters.
Subject:High-current, low-voltage power converter
Collaborator:Danifysik A/S (DK)
Contacts:G.Roy, F.Bordry, A.Dupaquier & G.Fernqvist/CERN–SL
The LHC superconducting accelerator requires high currents (12.5kA) and relatively low voltages (10V) for its magnets. The converter is made up using a modular concept where five current sources (4kA, 6V) are placed in parallel. The 4kA sources are configured in plug-in modules: a diode rectifier on the AC mains with a damped L-C passive filter, a zero voltage switching inverter working at 20kHz and an output stage (high frequency transformers, Schottky rectifiers and output filters).
Cryogenics
Subject:Cryogenic support posts for LHC magnets
Collaborator:Constructiones Aeronauticas SA, CASA (Division Espacio) (ES)
Contacts:M.Mathieu & C.Benvenuti/CERN–EST
Study, manufacture and delivery of three prototypes of support posts for the LHC dipole magnets. These posts are made of fibre-glass composite material, using the resin transfer moulding system, in order to optimize the production cost of large quantities, while keeping the heat inleak very low at cryogenic temperatures
Subject:Cryogenic temperature measurement for large applications
Collaborators:Helsinki University of Technology (FI), Institute of Particle Physics Technology (FI) & RV-Elektroniikka oy Picowatt (FI)
Contacts:T.Niinikoski & H.Hilke/CERN–EP
Reference:CERN-PPE/96–56 and Cryogenics 36 (1996) 1033
A resistance thermometry system has been developed for the acquisition, control and monitoring of temperature in large-scale cryogenic applications. The resistance of the sensor is converted to a voltage using a self-balancing AC bridge circuit featuring square-wave excitation currents down to 1nA. The system is easily scalable and includes intelligent features to treat special situations such as magnet quenches differently from normal operation. An 8-channel prototype was successfully operated in the tests of superconducting microstrip line detectors (RD39). A new version of the prototype includes a card for diode thermometers, a card optimized for 100Pt and rhodium iron sensors, and ADC resolution improvement to 20bits.
Subject:Measurement of materials at 4.2 and 1.8K
Collaborator:University of Saragossa (ES)
Contacts:N.Siegel & P.Bernard/CERN–LHC
Measurement of material samples, including magnetic characteristics of steels, at liquid-helium temperature.
Subject:Polycarbonate-based cryogenic sealing
Contacts:P.Wertelaers & H.Hilke/CERN–EP
The possibility and difficulties of realising cheap and robust cryogenic sealing, based upon a polycarbonate rectangular-section ring, squeezed in between flanges with a ‘nose’ profile, have been investigated. Results were presented from computations and tests in liquid nitrogen and liquid helium. Experience with the production of large-diameter seals from plastically deformed rods is being investigated.
Detectors
Subject:Mass production technology for PbWO4 scintillation crystals
Collaborators:CEA Saclay (FR), IHE Bogorodysk (RU), IHE Minsk (Belarus), IHEP Protvino (RU) & Laboratoire d’Annecy-le-Vieux de physique des particules, LAPP (FR)
Contacts:P.Lecoq & H.Hilke/CERN–EP
Reference:International Science & Technology Centre Moscow, Project No.354-R, CERN/LHCC 96–19.
Full-scale investigation of solid-state characteristics of PbWO4 scintillation crystals for use in the CMS and ALICE electromagnetic calorimeters and development of large-scale (over 50000) production technology using the Czochralski procedure.
Subject:Further developments of hybrid photodetectors
Collaborators:DEP (NL), EGETEC (FR), Preciosa (Czech Republic), RD7 Collaboration, RD19 Collaboration, INFN Roma (IT) & University of Rome III (IT)
Contacts:E.Rosso & H.Hilke/CERN–EP
Reference:IEEE Trans. Nucl. Sci. 42 (1995) 130
A new class of photodetectors (hybrid photodetectors) has been developed which surpasses traditional photomultiplier performances. Their anodes can contain from one silicon diode (hybrid photomultiplier tubes) up to a few thousand silicon pixels with integrated electronics (imaging silicon pixel array tubes). These detectors are single-photon and position-sensitive and have already been applied to count photons: to image particle tracks in scintillating fibre trackers, and to detect, by means of a suitable scintillator, gamma- and beta-rays over a wide range of energies.
Subject:Gas Electron Multiplier (GEM)
Collaborators:Budker Institute for Nuclear Physics, BINP (RU) & Weizmann Institue of Sciences, Rehovot (IL)
Contacts:F.Sauli/CERN–EP
Consisting of a thin, metal-clad polymer foil pierced by a high density of holes (typically 100/mm2), manufactured by an innovative printed circuit technology, the GEM mesh allows electrons drifting through to be multiplied by a factor of several thousand or more.
Subject:Scintillator materials - the Crystal Clear Collaboration
Collaborator:RD18 Collaboration
Contacts:B.Allardyce/CERN–PS & R.Forty/CERN–EP
The Crystal Clear Collaboration aims to find new and better fast scintillators, and new and better ways to use scintillators. The main materials studied are CeF3, PbWO4 and cerium-doped hafnium glasses.
Subject:Microstrip detectors at cryogenic temperatures
Collaborator:RD39 Collaboration
Contacts:T.Niinikoski/CERN–EP
Operating a heavily irradiated Si detector at liquid nitrogen (LN2) temperature results in significant recovery of Charge Collection Efficiency (CCE).
Subject:Diamond tracking detectors
Collaborator:RD42 Collaboration
Contact:P.Weilhammer/CERN–EP
Diamond, grown in a chemical-vapour deposition process, can be used as a particle detector.
Subject:High resolution tracking devices based on capillaries filled with liquid scintillator
Collaborator:RD46 Collaboration
Contact:J.Panman/CERN–EP
A large number of small-diameter scintillating fibres and highly integrated readout through optoelectronic devices (e.g. 5¥ 105capillaries of 20micron inner diameter are read out by a single image intensifier chain of 40mm input window)
Subject:Crystalline YAl03, a novel material for transmissive optics
Contacts:E.Rosso, H.Leutz, D.Puertolas, C.D’Ambrosio & F.De Notaristefani/CERN–EP
Replacement of a quartz photocathode window by a YAl03 (YAP) window yields improved light transitions from BGO crystals (1.78times) and PbWO4 crystals (1.76times) to the photocathode. This improvement is due to the higher refractive index of YAP (1.95), which matches much better the indices of BGO (2.14) and PbWO4 (2.18) than quartz (1.47).
Electronics
Subject:PMC to HIPPI interface
Collaborator:Compaq (Digital Equipment Corporation) (US)
Contacts:A.Van Praag & H.Hilke/CERN–EP
Reference:Overview of the Use of the PCI Bus in Present and Future High Energy Physics Data Acquisition Systems, PCI’95 Conference Proceedings, March 1995 pp.83–88, Annabooks, 11838 Bernardo Paza Court, San Diego
The PMC-HIPPI interfaces are in many respects similar to the PCI-HIPPI interfaces except for the mechanical form factor that follows the PMC specification. They are foreseen to be used in VME modules as prescribed by ATLAS.
Subject:S-Link, a data link interface specification
Contacts:R.Mclaren, E.Van Der Bij & H.Hilke/CERN–EP
Reference:
Many HEP experiments require simple, point-to-point data links from the detector electronics to buffer memories. In future experiments at the LHC, thousands of optical links will be required. These links must transfer data reliably at speeds of 100Mbytes/s over distances of 200metres whilst remaining compact and inexpensive. Working with other HEP institutes and industry we have defined the S-LINK to satisfy the requirements of the experiments. The specification defines, at both ends of the link, a simple FIFO-like user interface that remains independent of the technology used for the physical link. The physical link provides transfer of data and control words, error detection, optional flow control, and test facilities.
Subject:Timing, trigger and control (TTC) systems for LHC detectors
Collaborator:RD12 Collaboration
Contact:R.Forty/CERN–EP
At each of the CERN LHC experiments, timing, trigger and control (TTC) signals must be distrubuted to numerous electronic systems from a single location in the vicinity of the central trigger processor. A multichannel distribution system has been developed which can broadcast the signals to several thousand destinations from a few relatively high-power laser sources over a passive optical fibre network with uncontrolled path lengths.
Subject:Optoelectronic analog and digital signal transfer
Contact:F.Vasey/CERN–EP
The development of analog optical-fibre links for tracking detectors at the LHC. Extensive tests have been made to qualify the radiation hardness of optical-link components. The compents, including lasers, optical fibre connectors and pin-diodes of different types and origins have been irradiated with neutrons at ~0.75 and 6MeV as well as gamma rays. The effects investigated included the influence of particle incidence-angle and low temperatures (–10°C). Results have confirmed that devices from several different manufacturers can survive the total expected LHC-tracker doses and fluences. Accelerated ageing tests of non-irradiated as well as irradiated lasers and pin-diodes have been carried out at 80–176°C for over 4000hours. Statistical analysis indicates that the reliability of radiation-damaged components will be compatible with the lifetime requirements of the experiments.
Subject:Radiation tolerance of integrated circuits
Collaborator:RD49 Collaboration
Contact:P.Jarron/CERN–EP
Study of the radiation tolerance of advanced CMOS technologies and Commercial Off The Shelf (COTS) components that are expected to be placed in the radiation environment of the LHC experiments.
Subject:Integrated time-to-digital converter
Collaborators:CAEN (IT)
Contacts:J.Christiansen/CERN–EP
A family of time-to-digital converters (TDC) for drift time measurements with a resolution of 200–250ps r.m.s.
Subject:Device and method to measure a short radiation pulse or an electric pulse
Collaborator:CEA Saclay (FR)
Contacts:G.Roy, M.Cuzin?? & E.Rossa/CERN–SL
A device for measuring a single short pulse includes at least one measuring unit (D1, Dn) comprising a conductive line (L) connected to a set of photoconductors (A, B1-Bp), the line and photoconductors being placed between two nonconductors forming a single support in which the length of the line (x1) separating the photoconductors two-by-two is equal to the product of the propagation speed on the line with respect to the duration of the pulse concerning the number of measurement points, the lifetime of the majority carriers of the photoconductors being selected as being equal to or less than 10% of the duration of the pulse. The device makes it possible to obtain a temporal analysis or the autocorrelation of the pulse which may be an electromagnetic radiation or ionizing pulse or an electric pulse.
Subject:Single photon counting pixel detector
Collaborators:INFN Pisa (IT), University of Glasgow (UK), University of Freiburg (DE) & INFN Napoli (IT)
Contact:M.Campbell/CERN–EP
The single photon counting PCC chip has been developed in a commercial 1mm CMOS process, and it comprises an array of 64¥ 64pixel readout cells. Each readout cell, with a dimension of 170mm ¥ 170mm, contains a preamplifier, a comparator and a 15-bit scaler. The PCC was developed by us in the framework of the Medipix Collaboration (which comprised CERN, University of Freiburg, University of Glasgow and INFN (Pisa and Napoli).
Subject:Evaluation of commodity VMEbus equipment
Collaborators:Creative Electronic Systems (CH) & Motorola Computer Group (US)
Contact:M.Joos/CERN–EP
A number of VMEbus PowerPC based SBCs running the LynxOS operating system have been evaluated in the following areas: CPU performance: integer and floating point, bandwidth to system memory; real time performance interrupt handling, process, scheduling, signal handling, PCI performance, VMEbus performance,