"Development of 3-dimentinal high resolution track detector"

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Development of multi-cell drift chamber with anode and cathode readout was made in the purpose of obtaining high resolution in both perpendicular and parallel with anode wires. Proto-tests using a gas mixture of helium-ethane which has less effect of multiple-scattering were done, and the following results were obtained ;1) Using a small cell type wire configuration, anode readout resolution better than 100mum was obtained with an atmospheric pressure. Several different operating conditions were tried and those results were reproduced by computer simulation. The effect of magnetic field was under control, and the helium based gas has different Lorentz angle than that of the argon based one.2) dE/dx data was measured for a mixture of helium-ethane 50 : 50 as a function of beta nu of incoming particle. Relativistic rize was small. Resolution was 10% for minimum ionizing particles by the sampling of 10 layrs.3) Angular dependence in the cathode readout resolution was measured and it showed the caracteristic as expected. Spacial resolution of 400mum(550mum) wqas obtained for normal (50 deg.)incidence. To suppress the spread of cathode images and to obtain better resolution, shorter anode-cathode gap was tried. Improvement of 20% was seen. Effect of primary ion density was examined by changing the gas mixture. Qualitative effect was seen, however, the data for shallow incident angle showed disagreement with the simulation. Even though the unknown factors remained in understanding the basic feature of the cathode readout, obtained performance was good enough for a practical use.Along with the accumulation of the basic data, progress in mechanical issues were made in the developement of thin cylinder with carbon fibers and cathode strips with thin alminum. These were satisfactory and we had a good outlook for the construction of the practical model.