Thursday, 19 November 2015

Fabrication, Assembly and Testing of Multiwire Proportional Counters

Fabrication, Assembly and Testing of Multiwire Proportional Counters


Lakshmi Dagar , Amity Institute of Applied Sciences (Amity University) Noida, U. P.; Kajol Chakraborty, Amity Institute of Applied Sciences (Amity University) Noida, U. P.; Punita Verma, Kalindi College, University of Delhi, New Delhi; Akhil Jhinghan, Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi


Multiwire Proportional Counters, Fabrication, Detector


Multiwire Proportional Counter (MWPC), a particle studied under this project is an indispensable part of all nuclear physics experiments involving the study of compound nucleus and fission fragments. The work done under this project involves the fabrication, assembly and testing of a MWPC. The experimental work has been done at Inter University Accelerator Center (IUAC), New Delhi. The MWPC fabricated at IUAC had an active area of 16x11 cm2. Timing resolution and gain of the fabricated MWPC was made to improve over that of already available MWPCs at IUAC by reducing the anode wire pitch and using a ten micrometer diameter wire for anode frame. The fabricated MWPC was thoroughly tested with an alpha source and it was observed that the detector could handle heavy count rate exceeding 20 KHz without any breakdown. Fabricated MWPC was also used in a nuclear physics experiment in the NAND experimental set up of IUAC to extract information about mass, kinetic energy and angular distribution of fission fragments. All the detailed investigations done with the detector were part of the M.Sc. Dissertation work of the first two authors. During under graduation and post-graduation, students study about proportional counters with emphasis on their construction and basic principle of operation. However, this project work provided the first two authors with a unique opportunity of getting a practical experience on how these proportional counters are fabricated and their importance in the field of nuclear physics. Thus, project based learning leaves a larger impact on the mind of the students as far as understanding of concepts of science is concerned


A multi wire proportional counter is simply a gas filled wire chamber consisting of a large number of anode wires stretched in a plane for position measurement. The original motivation of developing such detectors came from the need to track particles in high energy physics experiments. The wire chambers, thus developed worked amazingly well and helped scientists make grea discoveries at particle accelerators. Although these chambers are still used in some laboratories, but since the advent ofhigh resolution silicon detectors their utility has somewhat diminished. Fig.1 shows the sketch of a typical multi wire proportional chamber [1]. The closely spaced thin anode wires are stretched in a plane that is midway between two cathode planes. The cathodes are kept at negative potential with respect to anode wires that are kept at ground potential. Each of the anode wires acts as an independent proportional counter and must therefore be read out independently [2].
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