An Improved Method using RBF Neural Networks to Speed up Optimization Algorithms

The paper presents a method using Radial Basis Function (RBF) neural networks to speed up deterministic search algorithms used for the optimization of superconducting magnets for the LHC accelerator project at CERN. The optimization of the iron yoke of the main LHC dipoles requires a number of numerical field computations per trial solution as the field quality depends on the excitation and local iron saturation in the yoke. This results in computation times of about 30 minutes for each objective function evaluation (on DEC-Alpha 600/333). In this paper we present a method for constructing an RBF neural network for a local approximation of the objective function. The computational time required for such a construction is negligible compared to the deterministic function evaluation, and thus yields a speed-up of the overall search process. The effectiveness of this method is demonstrated by means of two- and three-parametric optimization examples. The achieved speed-up of the search routine is up to 30 %

The correlation of processes of crystallization and changes of free electron density amorphous alloy powder Co80Ni20

Great attention is being given today to investigations on the capabilities and structural changes of amorphous and nanocrystal materials. Structural changes of the amorphous cobalt and nickel alloy powder obtained by electrochemical deposition were investigated in this paper. The crystallization process, as determined by the DSC method, occurred in two steps. The temperature dependence of electrical resistively and magnetic susceptibility in isothermal and non-isothermal conditions within the temperature range of room temperature to 700ºC was determined for the powder samples pressed under pressure of 800 MPa. The X-ray structural examinations results correlate with those of the DSC analysis and the electrical resistively measuring

Integrated Design of Superconducting Magnets with the CERN Field Computation Program ROXIE

The program package ROXIE has been developed at CERN for the field computation of superconducting accelerator magnets and is used as an approach towards the integrated design of such magnets. It is also an example of fruitful international collaborations in software development.The integrated design of magnets includes feature based geometry generation, conceptual design using genetic optimization algorithms, optimization of the iron yoke (both in 2d and 3d) using deterministic methods, end-spacer design and inverse field calculation.The paper describes the version 8.0 of ROXIE which comprises an automatic mesh generator, an hysteresis model for the magnetization in superconducting filaments, the BEM-FEM coupling method for the 3d field calculation, a routine for the calculation of the peak temperature during a quench and neural network approximations of the objective function for the speed-up of optimization algorithms, amongst others.New results of the magnet design work for the LHC are given as examples

2004 ATLAS Combined Testbeam : Computation and Validation of the Electronic Calibration Constants for the Electromagnetic Calorimeter

From July to November 2004, a full slice of the ATLAS barrel detector was studied in testbeam. A complete electromagnetic barrel module was used, read by the final electronics and operated by ATLAS TDAQ software. This note describes in details the electronic calibration procedure and the cell energy reconstruction: each step of the procedure and its associated software is explicitly described. The general calibration procedure is very similar to the one applied in previous barrel and endcap standalone testbeams. Emphasis is put on tools developed in the context of the combined testbeam which can be used for commissioning and operation of the calorimeters in ATLAS. Many validation studies were performed on each calibration constant. Previously unobserved effects such as the FEB temperature dependence of some constants were observed. Overall, the calibration performances are at the expected level

Rate effects in high-resolution drift chambers

The impact of high counting rates on the spatial resolution of cylindrical drift tubes is investigated in detail and the results are compared with simulations. Electronics effects and space-charge effects are quantitatively analysed. A spatial resolution of $\sigma < 80\,\mu\mathrm{m}$ can be achieved even at rates as high as 1500\,Hz/cm wire length (300\,kHz per wire)

Resolution limits of drift tubes

Measurements of the drift-tube response to charged particle tracks are compared with a complete simulation. The measured resolution of typically 80\,$\mu$m agrees well with the simulation and allows the individual factors limiting the resolution such as diffusion, charge deposit fluctuations, gas gain fluctuations and signal processing to be studied. The results with respect to the dependence of the drift chamber resolution on gas gain, gas pressure and electronics parameters are reported

Measurement of the solenoid magnetic field

We describe the machine used to map the solenoid field and the data sets that were collected. The bulk of the note describes the analysis of this data. A series of small corrections are made; some taken from surveys and some derived from the data itself. Two fitting methods are defined and applied to all data sets. The final result is that the field map at normal operating current can be fitted to a function that obeys Maxwell with an r.m.s. residual of less than 5 Gauss. Systematic errors on the measurement of track sagitta due to the field uncertainty are estimated to be in the range 2.3E-4 to 12E-4, depending on the track rapidity. Finally, the representation of the map in Athena is briefly described

Front-end electronics for drift tubes in a high-rate environment

A front-end electronics readout for drift tubes in a high-rate environment is presented. This system allows us to encode several pieces of information (leading edge time, trailing edge time, signal charge and piled-up hits from multiple tracks) into a single readout channel that is presented to the TDC. The advantage of active baseline restoration compared to bipolar signal shaping is discussed

Dependence of Drift Tube Performance on the Anode Wire Diameter

Cylindrical pressurized drift tubes with different anode wire diameters wereoperated in a 170~GeV muon test beam. The dependences of spatialresolution, efficiency and streamer probability on the anode wirediameter were measured. The resolution measurements are compared with a simulation