Fast track-finding processor based on RAM look-up table for the VENUS detector at KEK

We have developed a fast track-finding processor using signals from the central tracking chamber of the VENUS detector in the TRISTAN experiments. Particle tracks are recognized by a look-up table made with a high-speed static RAM. This method enables us to implement the track finder in the first level triggering. The track finder has been working excellently under heavy background due to synchrotron radiation. A processing time of 110 ns is attained.     

A superconducting secondary beam line in the 12 GeV proton synchrotron at KEK

Design and performance of a superconducting high energy secondary beam line, π1, are reported. The π1 beam line was constructed to transport an 8 GeV/c unseparated secondary beam to the experimental area of the 12 GeV proton synchrotron at KEK. The beam line has been operated for five years without any serious problems and was shut down in the summer of 1986. We describe its design, construction and operational results.     

Performance of the VENUS lead-glass calorimeter at TRISTAN

The initial performance of the VENUS barrel electromagnetic calorimeter at TRISTAN is described. The calorimeter is composed of 5160 lead-glass counters in a semi-tower arrangement. An energy resolution of 3.8% was obtained for 26 GeV Bhabha events. The neutral pions in the hadronic events were reconstructed with a mass resolution of σ = 16 MeV. The gain of the lead-glass counters was stable within 2% during a four months operation at TRISTAN.     

On the testing of large superconducting magnet systems

A new approach to the testing of large superconducting magnet system is proposed.     

11 T liquid helium-free superconducting magnet

An 11 T liquid helium-free superconducting magnet designed at 6 K in vacuum using high temperature superconducting current leads was developed. The coil was conductively cooled down from room temperature to 4.1 K in 40 h by two 4 K GM-cryocoolers. In a performance test, the coil temperature rose to 6.8 K for the inner Nb₃Sn coil and 5.9 K for the outer NbTi coil, while sweeping the field at 5 A min⁻¹. A central field of 10.7 T in a 52 mm room temperature bore was generated at an operating current of 149 A. Holding the field at 10.5 T was achieved continuously for 24 h at a constant coil temperature of 4.8 K.     

19.3 T with a superconducting magnet

The magnet system HOMER has been used to generate a magnetic field of 19.3 T. Nb₃Sn insert coils were used in conjunction with the NbTi background magnet.     

Strain gauges for superconducting magnet testing

A survey of commercially available strain gauges potentially suitable for testing of superconducting magnets is presented. Strain measurement errors caused by magnetic fields and temperature changes are discussed. Previously unpublished data for the magnetic field induced error for weldable half-bridge strain gauges are given, along with the results of a test for the temperature dependence of the magnetorestistance of modified Karma alloy foil gauges in the liquid helium temperature range. Apparent strain-vs-temperature curves for the weldable half-bridge gauges and metal foil gauges are shown. Errors caused by magnetic fields are in general repeatable from gauge to gauge, whereas errors due to temperature effects exhibit considerable variation from gauge to gauge in a lot of nominally identical gauges.     

A 5 Tesla superconducting wiggler magnet

The design, construction and testing of a three pole superconducting magnet is described. Integral field measurements are compared with computed predictions. Integration of the magnet with its associated refrigeration system and the storage ring is outlined.     

The TOPAZ luminosity monitor at KEK

The details of the TOPAZ luminosity monitor at KEK are presented. The design concept and construction method are described. Optical fiber was chosen as the material for the light guide because of its flexibility. Results for the performance of counters in electron beam tests are presented. The data acquisition system is also described in detail.     

Direct digital control of a superconducting magnet

A microcomputer-based controller and its input/output interfaces have been developed for an inductor-converter unit (IC unit) which consists of a six-pulse Graetz-type converter and a solenoidal superconducting magnet (SM). The SM current is feedback-controlled through the following operations: detection of the SM current, comparison with the reference input for generation of the error signal, determination of the firing angle by the digital operation of compensation, and generation of the trigger pulses. The algorithms for digital compensation have been studied by experiments as well as computer simulations. Proportional-integral-derivative (PID), first-order exponential response with transport delay (Dahlin algorithm), and finite time settling control (FTSC) algorithms have been simulated and experimented by using the IC unit. Accurate agreements between the results of simulations and experiments have been obtained for the PID and Dahlin algorithms. The FTSC algorithm has shown the best response of the three methods.     

超导磁体在NdFeB永磁材料制备技术中应用研究

概述了超导磁体技术的研究进展,分析了超导磁体在NdFeB永磁材料制备过程中的应用前景,重点讨论了超导磁体在烧结NdFeB磁体、NdFeB铸锭组织、HDDR(氢化-歧化)工艺制备NdFeB纳米晶粉末等领域的具体应用情况.     

Data acquisition system for the VENUS detector at TRISTAN

A data acquisition system for the VENUS detector at the TRISTAN electron-positron collider is presented. The whole system of the VENUS detector consists of nine different kinds of principal detectors, and the total number of electronics channels of the system reaches about 30 000. A FASTBUS system was introduced as the main data path and the TKO and the CAMAC standard have also been utilized for the frontend electronics. A FASTBUS interface to an on-line computer (VAX11/780), simplex segment interconnect and many data acquisition modules were developed. Most of the data are analyzed in a VAX cluster system in real time. Data logging is done in a main frame computer (FACOM M382) by using an automatic loading cartridge tape subsystem.     

Large aperture superconducting magnet (benkei)

Benkei, which was a large window frame conventional magnet at KEK has been converted to a superconducting magnet. In the conversion, the pole gap has been doubled from 0.5 m to 1.0 m retaining an analysing power at 2 T m. Several new techniques were applied to coil windings and cryostat fabrication. The superconducting Benkei has shown satisfactory performances for long term operation.     

Lumped-Element Dynamic Electro-Thermal model of a superconducting magnet

Modeling accurately electro-thermal transients occurring in a superconducting magnet is challenging. The behavior of the magnet is the result of complex phenomena occurring in distinct physical domains (electrical, magnetic and thermal) at very different spatial and time scales. Combined multi-domain effects significantly affect the dynamic behavior of the system and are to be taken into account in a coherent and consistent model.A new methodology for developing a Lumped-Element Dynamic Electro-Thermal (LEDET) model of a superconducting magnet is presented. This model includes non-linear dynamic effects such as the dependence of the magnet’s differential self-inductance on the presence of inter-filament and inter-strand coupling currents in the conductor. These effects are usually not taken into account because superconducting magnets are primarily operated in stationary conditions. However, they often have significant impact on magnet performance, particularly when the magnet is subject to high ramp rates.Following the LEDET method, the complex interdependence between the electro-magnetic and thermal domains can be modeled with three sub-networks of lumped-elements, reproducing the electrical transient in the main magnet circuit, the thermal transient in the coil cross-section, and the electro-magnetic transient of the inter-filament and inter-strand coupling currents in the superconductor. The same simulation environment can simultaneously model macroscopic electrical transients and phenomena at the level of superconducting strands.The model developed is a very useful tool for reproducing and predicting the performance of conventional quench protection systems based on energy extraction and quench heaters, and of the innovative CLIQ protection system as well.     

Numerical treatment of the quenching process in superconducting magnet systems

A computer program for testing coil and protection design of a composed magnet system is presented. Small high field magnets consisting of two uniaxial cylindrical coils of different superconducting materials (eg NbTi and V₃Ga or Nb₃Sn) are considered, each coil may be subdivided into several sections which are protected by parallel resistors. Quench propagation due to thermal conduction and also due to rapid current increase (important in inductively coupled systems) is taken into account by means of solving a one-dimensional thermodiffusion equation. Field and temperature dependence of the critical current for every layer of the coils, is taken into account. The program calculates the time dependence of currents, external and internal voltages, resistances of the sections and of the radial temperature distribution. Calculations are compared with experimental investigations of three different systems, the results agree with experimental values concerning current decay and propagation velocity.     

TOPAZ barrel electromagnetic calorimeter at TRISTAN,KEK

A barrel electromagnetic calorimeter consisting of 4300 lead glass blocks has been constructed and operated in the TOPAZ electron-positron colliding experiment, at TRISTAN, KEK. Details of the apparatus, the readout system, the calibration procedure, and the stability monitoring system are presented. The performance of the detector studied with a test setup and that obtained in the initial experimental runs are discussed.