Nuclear Instruments and Methods in Physics Research最新文献

Streamer tubes with graphited walls and external pick up strip electrodes have been used to study the localization and the spread of electromagnetic showers following compact or distributed converters of up to two radiation lengths of materials. Comparing the strip distributions for different conditions, we find no deterioration, neither in the positioning nor in the resolving power with respect to minimum ionizing particles traversing no material.

Three drift chambers arranged to represent the cross section of the LEP L3 muon detector were used for track measurements. Displacing the middle chamber by 3.8 mm, corresponding to the sagitta of a 45 GeV muon in 5.1 kG, measurements with UV laser tracks 3 m long yield an equivalent momentum resolution of 1.5%.

A method to perform the measurement of photon beam spectra from X-ray tubes is described. It consists of exciting the fluorescence of elements with their K-binding energies lying within the energetic range of the bremsstrahlung spectrum, using the tube photon beam, and a ²⁴¹Am excitation source as a reference, to normalize individual results of each element. According to the numerical treatment described in this article, uncertainties in relative photon flux determinations range from 10% to 2% depending on the photon energies. This method overcomes the difficulties associated with the detection of high photon rates produced by an X-ray tube.

A time-of-flight technique and iron-filtered neutrons were applied to neutron radiography and to computer tomography. By making use of iron-filtered neutrons, the existence of 1 mm thick copper within an iron block of 20 cm thickness could be clearly distinguished. To investigate the possibility of neutron computer tomography using iron-filtered neutrons, two cylindrical metallic samples made of CuFePb and CuFeAl were used. From the reconstructed image of the samples, we could clearly see the internal structures.

A data acquisition system which consists of encoder and buffer memory modules has been developed for the meson spectroscopy experiment of E64 at KEK. It is simple, flexible and has a high rate performance. The adapted on-line program has a flexible structure and is powerful in monitoring the data acquisition process.

Measurements of the response of BGO crystals to protons in the energy range from 6 to 13 MeV and to alpha particles in the range from 6 to 19 MeV are discussed. Results were obtained with a photomultiplier tube and a photodiode readout. A comparison is made with the response of a NaI(Tl) crystal to 13 MeV protons.

Kinematic line broadening of the image was corrected by using multipole magnetic fields for the spectrograph “RAIDEN” at the Research Center for Nuclear Physics (RCNP).

Arrival positions of the collimated rays with various angles of incidence were measured at the focal line as a function of strengths of the multipole magnetic fields. Measurements were performed for various values of the kinematic factor of nuclear particles scattered from the target nucleus. Strengths of the multipole fields which achieved the best directional focussing were extracted from the measured results. The strengths were proportional to the kinematic factor and the kinematic line broadening was corrected up to higher order in the median plane.

An analytical calculation of the variance is performed, in some simple case, for standard least-squares estimators of track parameters (accounting for independent measurement errors only); comparison is made with optimal estimators (accounting also for scattering errors, correlated between one point and the following ones). A new method is proposed for optimal estimation: the points measured on the track are included backwards, one by one, in the fitting algorithm, and the scattering is handled locally at each step. The feasibility of the method is shown on real events, for which the geometrical resolution is improved. The algorithm is very flexible and allows fast programmation; moreover the computation time is merely proportional to the number of measured points, contrary to the other optimal estimators.