Determination Of Fast Gas Filling Multi-wire Proportional Counter

In the field of Ionizing Radiation metrology, the meteraging of α、β plane sources is an indispensable part of radical activity quantity-transfer system. Surface emission rate determined a or β plane source can be used as radical activity standard to graduate instruments, to calibrate instruments, or to weigh the radical activity of other environmental sample. We consider it as activity reference source or test source. The conventional instrument to measure α、β plane sources is Large area2π Multi-Wire Proportional Counter which is of a approximately100%instrument efficiency, The use of MWPC(Multi-Wire Proportional Counter) is a kind of absolute measurement.China State Bureau of Quality and Technical Supervision promulgated and enforced JJG2041-1989"Verification Scheme of Measuring Instruments for Measurements of α、β Surface Contamination" in1989and JJG788-1992"Verification Regulation of The α、β Standard plane Source" in1992,Set of rules of Verification of The α、β Standard plane Source, Verification of The α、β Surface contamination, and the procedure radical activity quantity-transfer from the Primary Standard to each individual contamination. The Measuring Instruments for Measurements of α、β Surface Contamination is consist of a Primary Standard,a Secondary Standard and other Primary References. As we set up the project, there is a Primary Standard in National Institute of metrology P.R.China which is in Beijing and another Secondary Standard in National Institutes of Measuring and Testing Technology in Chengdu. There is no References instrument in provincial institute of metrology. Shanghai and the east part enjoy the highest economic growth speed in nowadays China, the Eastern China is a Nuclear Power Industry gathering place and is one of the Nuclear Technology, Radiation Protection and Environmental Monitoring Technology most prosperous area thus urgently demanding for determining. It is very practical to construct the2π α、β Primary Reference in Shanghai institute of Measurement and Testing Technology to provide quantity-trace for Nuclear Power Industry, Nuclear Technology, Radiation Protection and Environmental Monitoring Technology in Shanghai and Eastern China, and to meet the need of market at the same time.The main topics of this thesis are as follows:1. We did a full investigation about MWPC’s current situation, proved that it is meaningful and practical to construct a27πα、πβ Primary Reference in Shanghai institute of Measurement and Testing Technology based on MWPC, and set the specifications accordingly. Elaborated the character of a Ionizing Radiation metrology used MWPC and the Verification Scheme.2. We studied the MWPC’s electric-field distribution and operational principle, intensive studied the key component, we presented the design after fully considered.3. We innovated the MWPC’s gas filling pattern, adopted a fast gas filling design to minimize the gas filling time which a ordinary MWPC will take hours and achieved the anticipated target.4. We used intelligent instrument technology to design the overall measuring system on the basis of current MWPC. The system is consisted of MCU control part and upper computer. The main work is to construct a MWPC, to design circuits of a charge sensitive preamplifier and a main amplifier, a single chip processor control system based on c8051f020.5. We developed a software system, including a upper computer application and MCU program. Upper computer application developed on the platform of VC++6.0which is to control the measuring process, to acquire the data and analysis it. MCU program developed on the platform of KEIL, which is to acquire the data, to control the I/O device and to communicate. 6. We passed the Test evaluation, it meets each former set specifications, we accomplish the mission that determinated a2πα、2πβ particle emission reference instrument.To sum up, we reported a MWPC measuring system designed by using the modern measuring techniques, we innovated MWPC’s gas filling pattern. it is a perfect low cost instrument with advanced technology, simplified function, innovated measuring method. it meets the requirements of National Verification Scheme and each former set specifications. The instrument passed the Test evaluation, measuring system is of ideal a and β plateau curve length. determined with a plane source that surface emission rate in the range of (102～106) particle/2π sr·min, the efficiency is99.3%, the measurement repeatability is0.3%, the54hours stability is1.4%. determined with p plane source that surface emission rate in the range of (103～106) particle/2π sr·min, the efficiency is99.9%, the measurement repeatability is0.3%, the54hours stability is0.9%.