A fast track trigger processor for the opal detector at LEP

A fast hardware track trigger processor being built for the OPAL experiment is described. The processor will analyse data from the central drift chambers of OPAL to determine whether any tracks come from the interaction region, and thereby eliminate background events. The processor will find tracks over a large angular range, |cos θ| 0.95. The design of the processor is described, together with a brief account of its hardware implementation for OPAL. The results of feasibility studies are also presented.     

A fast programmable trigger for pattern recognition

We have built a fast programmable trigger processor based on a state-of-the-art Field Programmable Gate Array (FPGA) IC for the Palo Verde Neutrino Oscillation Experiment. The trigger processor can accommodate 160 ECL input signals, 8 NIM input signals, 16 ECL output signals and 8 NIM output signals. Our two-level trigger logic is designed asynchronously to maximize speed. We have attained trigger times of 40 ns for level 1 and 100 ns for level 2 with 132 asynchronous inputs. The trigger processor can be upgraded by replacing the FPGA with more advanced versions of the chip as they appear.     

A clocked,fast electronics trigger for high energy physics

For a Fermilab experiment we have designed and built gated-pulse-stretcher modules which allow us to clock all of the fast electronics with the accelerator rf, thus simplifying the trigger design.     

A fast trigger processor,for a scattering experiment,implemented in fastbus

A small angle interaction trigger processor (SAIT) used in a muon scattering experiment (NA28) at CERN is described. It comprises 10 FASTBUS modules and employs ECL 100K and 10K type circuits. The processor can select events with scattering angles larger than ∼1 mrad and can be used at a beam intensity of up to 10⁷ particles per second without appreciable deadtime losses.     

Superconducting magnet development for fusion at JAERI

The development of superconducting magnets for fusion at the Japan Atomic Energy Research Institute (JAERI) is described. The objective of the project is the Fusion Experimental Reactor (FER) which will be constructed with superconducting toroidal and poloidal coils. For toroidal coils, JAERI has already developed the 8 T Japanese LCT coil and five other large coils (one NbTi and four Nb₃Sn coils, from 7 T to 11 T) for the Cluster Test Programme. For poloidal coils, JAERI has developed three 30–50 kA pulsed conductors. In addition to coil development, cryogenic technology and structural material development are also in progress.     

A pipelined noise shaping coder for fractional-N frequencysynthesis

In this paper, we present the design considerations and implementation aspects of a pipelined all-digital fourth-order multi-stage-noise-shaping (MASH) delta-sigma (▵Σ) modulator suitable for fractional-N (F-N) phase-locked loop (PLL) frequency synthesis applications. In an effort to reduce the hardware complexity and power consumption, the alignment registers, which are normally required in pipelined adders, are eliminated by taking advantage of static modulator input. The MASH modulator has successfully been targeted to an Altera^TM field-programmable-gate-array (FPGA) device. The functional operation of the modulator has been verified through structural bit-level simulations as well as experimental results on the actual FPGA implementation     

A muon trigger for the MACRO apparatus

A trigger circuit based on EPROM components, able to manage up to 30 lines from independent counters, is described. The circuit has been designed and used in the MACRO apparatus at the Gran Sasso Laboratory for triggering on fast particles. The circuit works with standard TTL positive logic and is assembled in a double standard CAMAC module. It has a high triggering capacity and a high flexibility.     

Digital calibration for monotonic pipelined A/D converters

The original digital calibration approach for 1 b/stage and 1.5 b/stage pipeline analog-digital converters produces missing or nonmonotonic digital codes with the device and circuit impairments typical of modern deep submicrometer CMOS technologies. Two digital calibration algorithms are introduced to improve pipeline performance when using low-voltage low-gain nonlinear operational amplifiers and high random dc offset voltage comparators. The first technique computes calibration coefficients for each stage at actual transition points of the residue characteristic to assure converter monotonicity in the presence of random comparator offset voltages. The second augments a conventional pipelined architecture with an input-dependent level-shifting stage and additional digital calibration circuitry to achieve high differential and integral linearity with low-gain nonlinear operational amplifiers.     

Physics requirements for the design of the ATLAS and CMS experiments at the Large Hadron Collider

The ATLAS and CMS experiments at the CERN Large Hadron Collider are discovery experiments. Thus, the aim was to make them sensitive to the widest possible range of new physics. New physics is likely to reveal itself in addressing questions such as: how do particles acquire mass; what is the particle responsible for dark matter; what is the path towards unification; do we live in a world with more space-time dimensions than the familiar four? The detection of the Higgs boson, conjectured to give mass to particles, was chosen as a benchmark to test the performance of the proposed experiment designs. Higgs production is one of the most demanding hypothesized processes in terms of required detector resolution and background discrimination. ATLAS and CMS feature full coverage, 4π-detectors to measure precisely the energies, directions and identity of all the particles produced in proton-proton collisions. Realizing this goal has required the collaborative efforts of enormous teams of people from around the world.     

The data acquisition and reduction challenge at the Large Hadron Collider

The Large Hadron Collider detectors are technological marvels-which resemble, in functionality, three-dimensional digital cameras with 100 Mpixels-capable of observing proton-proton (pp) collisions at the crossing rate of 40 MHz. Data handling limitations at the recording end imply the selection of only one pp event out of each 10(5). The readout and processing of this huge amount of information, along with the selection of the best approximately 200 events every second, is carried out by a trigger and data acquisition system, supplemented by a sophisticated control and monitor system. This paper presents an overview of the challenges that the development of these systems has presented over the past 15 years. It concludes with a short historical perspective, some lessons learnt and a few thoughts on the future.     

Heavy-ion physics with the ALICE experiment at the CERN Large Hadron Collider

After close to 20 years of preparation, the dedicated heavy-ion experiment A Large Ion Collider Experiment (ALICE) took first data at the CERN Large Hadron Collider (LHC) accelerator with proton collisions at the end of 2009 and with lead nuclei at the end of 2010. After a short introduction into the physics of ultra-relativistic heavy-ion collisions, this article recalls the main design choices made for the detector and summarizes the initial operation and performance of ALICE. Physics results from this first year of operation concentrate on characterizing the global properties of typical, average collisions, both in proton-proton (pp) and nucleus-nucleus reactions, in the new energy regime of the LHC. The pp results differ, to a varying degree, from most quantum chromodynamics-inspired phenomenological models and provide the input needed to fine tune their parameters. First results from Pb-Pb are broadly consistent with expectations based on lower energy data, indicating that high-density matter created at the LHC, while much hotter and larger, still behaves like a very strongly interacting, almost perfect liquid.     

Superconducting magnet for K-500 cyclotron at VECC, Kolkata

K-500 superconducting cyclotron is in the advanced stage of commissioning at VECC, Kolkata. Superconducting magnet is one of the major and critical component of the cyclotron. It has been successfully fabricated, installed, cooled down to 4.2 K by interfacing with LHe plant and energized to its rated current on 30th April, 2005 producing magnetic field of 4.8 T at median plane of cyclotron. The superconducting magnet (stored energy of 22MJ) consists of two coils (α and β), which were wound on a sophisticated coil winding machine set-up at VECC. The superconducting cable used for winding the coils is multi filamentary composite superconducting wire (1.29 mm diameter) having 500 filaments of 40 μm diameter Nb-Ti in copper matrix which is embedded in OFHC grade copper channel (2.794 mm × 4.978 mm) for cryogenic stability. The basic structure of coil consists of layer type helical winding on a SS bobbin of 1475 mm ID × 1930 mm OD × 1170 mm height. The bobbin was afterwards closed by SS sheet to form the LHe chamber. The total weight of the coil with bobbin was about 6 tonne and the total length of the superconducting cable wound was about 35 km. Winding was done at very high tension (2000 PSI) and close tolerance to restrict the movement of conductor and coil during energization. After coil winding, all four coils (two each on upper and lower half of median plane of cyclotron) were banded by aluminium strip (2.7 mm × 5 mm) at higher tension (20,000 PSI) to give more compressive force after cool down to 4.2 K for restricting the movement of coil while energizing and thereby eliminating the chances of quench during ramping of current.After completion of coil winding by October, 2003, cryostat assembly was taken up in house. The assembly of cryostat (13 tonne) with support links (9 Nos.) refrigeration port, instrumentation port, helium vapour cooled current loads, etc. was completed by June, 2004. Meanwhile assembly of magnet frame was taken up and the cryostat was positioned in the magnet frame with proper alignment by August, 2004. After installation of cryostat on magnet, the cryostat was connected to the helium refrigerator/liquefier, having refrigeration capacity of 200 W and 100 l/h in liquefier mode with LN2 pre-cooling. The cryogenic delivery system supplying the liquid helium and liquid nitrogen to the superconducting magnet was successfully commissioned in November, 2004. The cool down of the cryostat to 10 K took around 8 days following which the LHe was filled in the cryostat (300 l) on 15th January, 2005. Subsequently the superconducting coils (α and β) were energized by two DC current regulated power supplies (20 V, 1000 A, 10 ppm stability) with slow and fast dump resistors connected externally across the superconducting coils for protection of coils at the time of power failure and quench.The paper describes the intricacies involved in coil winding, winding set-up, assembly of cryostat, cooling down the superconducting coils, filling by LHe and energization to rated current. The paper also highlights the operating experience of superconducting magnet and related test results.     

A fast multipole method for Maxwell equations stable at all frequencies

The solution of Helmholtz and Maxwell equations by integral formulations (kernel in exp(i kr)/r) leads to large dense linear systems. Using direct solvers requires large computational costs in O(N(3)). Using iterative solvers, the computational cost is reduced to large matrix-vector products. The fast multipole method provides a fast numerical way to compute convolution integrals. Its application to Maxwell and Helmholtz equations was initiated by Rokhlin, based on a multipole expansion of the interaction kernel. A second version, proposed by Chew, is based on a plane-wave expansion of the kernel. We propose a third approach, the stable-plane-wave expansion, which has a lower computational expense than the multipole expansion and does not have the accuracy and stability problems of the plane-wave expansion. The computational complexity is Nlog N as with the other methods.     

合肥超导托卡马克装置首次致冷

１９９４年７月１２－２２日期间合肥超导托卡马克装置ＴＨ－７首次低温调试。４Ｋ温区冷重高达１４Ｔ的超导环场磁体经９６ｈ致冷，用二相Ｈｅ保冷３昼夜。超导线圈内外侧设侧设置的热辐射屏重约８Ｔ，用液氦致冷，约６０ｈ冷至８０Ｋ。磁体共励磁二次，最大电流达４６５０Ａ，相应的环场为２．２Ｔ，超导体的最高场为３．７Ｔ。     

Development of the central trigger system for the BELLE detector at the KEK B-factory

In this paper, we describe the design and development of the central trigger system (GDL) for the BELLE detector at the KEK B-factory. The GDL consists of four types of single width 6U VME modules (ITD, FTD, PSNM and TMD) which are designed using the programmable logic techniques of Xilinx FPGA and CPLD. Individual and combined performance tests of these modules are done and it is confirmed that the GDL functions as expected.