Ryotaro Tanaka

Construction of the ATLAS semi-conductor tracker (SCT) barrel modules in Japan

Abstract We have developed a semi-automated assembly system and constructed 124 silicon microstrip modules so far for the ATLAS SCT barrel. This article describes the assembly procedure, evaluations of precisions and the module survey results. A precision of ∼2xa0μm is achievable with this assembly system.

The 55Mn and 57Fe NMR Study of FeCrMn Alloys

The nuclear magnetic resonance (NMR) study has been made for the 55 Mn and 57 Fe nuclei in disordered ferromagnetic alloys (Fe 1- x Cr x ) 0.99 Mn 0.01 ( x ≤0.3) by the spin echo method in zero external magnetic field at 1.7 K. The frequency corresponding to the center of gravity of the 55 Mn NMR spectrum increases from 239.9 MHz at x =0 up to a maximum value of 267±5 MHz at x =0.20 with increasing x and then decreases down to 236.4 MHz at x =0.30. The deduced value of the Mn magnetic moment increases monotonically from 0.72 µ B at x =0 with increasing x , passes a maximum value of 1.33 µ B at x =0.20 and then dedreases to 1.2 µ B at x =0.30. This variation of the Mn moment with x is correlated with that of the Cr magnetic moment, and it is suggested that the moment of the Mn impurity is more localized in alloys with a higher Cr content. The 57 Fe NMR spectrum is also discussed.

Measurement of the Polarization of \(\varLambda^{0}\) Hyperons Produced Inclusively by 12-GeV Protons on Tungsten

The polarization of 2.4×10 5 (varLambda^{0}) hyperons has been measured in inclusive production by 12- GeV protons on tungsten at three production angles, 3.5°, 6.5°, and 9.5°. In terms of Feynmans x F and the transverse momentum p T of (varLambda^{0}), the kinematic range is 0.3≦ x F ≦0.8 and 0.4≦ p T ≦1.6 GeV/c. The (varLambda^{0}) was identified by detecting the proton and pion from the (varLambda^{0}{rightarrow}ppi^{-}) decay with a double-stage magnetic spectrometer, and its polarization was determined from a hybrid Monte Carlo analysis on asymmetries in the angular distribution of the decay products. The observed polarization is consistent with the data obtained at higher energies, indicating that the phenomenon of the inclusive (varLambda^{0}) polarization scales down to the 12-GeV region. The polarization at 12 GeV increases linearly with p T up to 16% at p T =1.0 GeV/c, showing a tendency to level off above that point.

Development of the hybrid structure for the barrel module of the ATLAS silicon microstrip tracker

A novel hybrid structure for the barrel module of the ATLAS Semiconductor Tracker (SCT) is developed. The hybrid carries 12 bare readout chips totaling 1536 channels. A flexible copper-polyimide 4-layer lamination is used as a basic circuit. The circuit is re-enforced by two carbon-carbon bridges coated with Parylene polymer. The hybrid staffed by resistors, capacitors and pitch adaptors undergoes heat cycling and quality inspections. The hybrid after chip mounting and wire bonding is placed over the top and bottom sides of the module assembly with no direct contact to silicon sensors. Some twenty full-fledge modules with active silicon strip sensors were assembled Their electrical, mechanical as well as thermal performances of the module are proven to be excellent.

Polarized Λ0 production at KEK

We have measured the polarization of Λ0 hyperons produced inclusively by 12 GeV protons on tungsten at KEK. For moderate xF (0.2≳xF≳0.7), the polarization is nearly independent of xF and increases roughly linearly with pT. As xF increases beyond 0.7, however, the polarization shows a significant xF dependence. Some preliminary data were taken on copper and beryllium targets. A future project on Σ0 polarization at KEK is indicated.

Results of early phase of series production of ATLAS SCT barrel hybrids and modules

The ATLAS experiment is a general purpose experiment being constructed at the Large Hadron Collider (LHC) at CERN, Geneva. ATLAS is designed to exploit the full physics potential of LHC, in particular to study topics con- cerning the Higgs mechanism, Super-symmetry and CP violation. The cross sections for the processes under study are extremely small, requiring very high luminosity colliding beams. The SemiConductor Tracker (SCT) is an essential part of the Inner Detector tracking system of ATLAS. The active elements of the SCT is 4088 detector modules, tiled on four barrel cylinders and eighteen endcap disks. As a consequence of the high luminosity, the detector modules will operate in a harsh radiation environment. This the- sis describes work concerning radiation hardness, beam test performance and methods for production testing of detector modules. The radiation hardness studies have been focused on the electrical performance of the front-end ASIC and the detector module. The results have identifed features of the ASIC failing after irradiation and conrmed the good performance of the re-designed ASIC. The beam tests have been performed in the late prototyping and the pre-production phase, verifying the specied performance of the detector modules. Special effort have been made to evaluate the performance of irradiated detector modules. The assembly, quality assurance and characterisation of the detector modules will be done in the collaborating institutes. The thesis reports on methods developed for use during the production, to assess the electrical performance.

Design and operation of the Λ beam at KEK

Abstract The design and operation of a Λ beam using the KEK 12-GeV proton synchrotron are described. Fluxes of 110, 15, and 5 Λs were obtained for 1.0 × 1010 primary protons on a 40-mm long tungsten target at the production angles of 3.5°, 6.5°, and 9.5°, respectively. The Λs were identified by a kinematic fitting to their predominant decay mode, Λ → pπ−, which was analyzed by a double magnetic spectrometer.