Study Of MWDC In High Magnetic Field At The External Target Facility Of CSR

The Multi-Wires Drift Chamber(MWDC)is one of the most important gas detectors applied for measuring particle tracks at External Target Facility(ETF)of HIRFL-CSR in Lanzhou.In order to improve the accuracy of the particle track measurements and the particle identifications,and reduce measured position uncertainties due to the multi-scatterings in the air,a novel detector system of MWDCs for the particle track measurements set at the entrance and the interior of the dipole magnet.This thesis first introduced the development and research status of the Sceond Radiactive Beam Line in Lanzhou(RIBLL2)and the research motivation of the present studies.The theoretical basis of the MWDC,including the kinetic theory of gases and the working principle of drift chambers,was then given briefly.The theoritical simulations,including the Maxwell electrostatic field,the edge effect,the field wire malposition effect and among others,were performed about the MWPCs at ETF.Two types of MWDCs with drift cells with 5 mm and 10 mm were designed.The performance index of the established MWDC system,i.e.,working voltage,drift time spectrum,signal width,drifting track and among others,was examed using the 400 Me V/u 16O8+ beams.A track could be obtained when four or three layers of anode were fired,so,the detection efficiency is defined as the fired efficiency of each layer of anode wires on a track,and the track residual is defined as the difference between the distance calculated by the drift time of the anode wires and the distance from the anode wires to the track.In this paper,track residuals are used to characterize the position resolution of the detector.The results suggest that the detection efficiency(>99%)of the MWDC with the 5 mm drift cell,with a position resolution better than 130 μm,is greater than that with the 10 mm drift cell.It is also found that the MWDC performs well under a magnetic field of 1.2T and has a detection efficiency greater than 99%.Due to the Lorentz force difference along the X and Y axes,the drifting tracks differ.The position resolutions of X and Y are better than 140 μm.Allowing for the the multi-scatterings in the air,MWDCs applying under low pressure in the vacuum were built and examed.The detection efficiency is greater than 99% and the position resolution is 386 μm.MWDCs applyed under low pressure open up a new research field for upgrading the track detectors in vacuum at RIBLL1.The present work lays a foundation for the application of gas detectors in the experiments with high energy and high intensity at HIAF.