核辐射的检测方法，指标，仪器，原理和相关的环境标准Nuclear radiation detection methods, indicators, instruments, principles and relevant environmental standardsThe interaction between nuclear radiation and matter is the physical basis of nuclear radiation detection. The interaction between nuclear radiation and matter, including ionization, scattering and absorption of nuclear radiation, the use of ionizing radiation of the substance decays, absorption and reflection effect in combination with α, β, and γ-ray features a variety of detectioncan be completed.Nuclear radiation detection instrument principles and methodsTo indicate the recording and measurement of nuclear radiation materials or devices. Radiation and nuclear radiation detector material interactions and some kind of information (such as electrical, optical pulse or material changes in the structure), the zoom after record analysis, to determine the number of particles, location, energy, momentum, flight time, speed, quality and other physical quantities. Nuclear radiation detectors is nuclear physics, particle physics and radiation applications an indispensable tool and means. In accordance with the recording, nuclear radiation detectors are generally dividedinto two major categories of counters and track room.Counter to the electrical impulses in the form of records, analysisof the radiation produced by certain types of information. The type ofthe counter gas ionization detectors, multi-wire chamber and drift chamber, semiconductor detectors, scintillation counters and Cerenkov counters.The gas ionization detector ionization charge generated in the gas through the collection of rays to measure nuclear radiation. The main types of ionization chamber, proportional counter and Geiger counter. Their structure, usually cylindrical container with two electrodesfilled with a gas, the voltage between the electrodes, the difference is that the operating voltage range. The low operating voltage of the ionization chamber, direct collection of the ray in the original gas produce ion pairs. The output pulse amplitude is smaller, faster rise time, and can be used for the measurement of radiation dose measurement and spectroscopy. The higher the operating voltage of the proportional counter, make more ion pairs in high-speed movement in the electricfield in the original ion collection electrode to the much larger ion than the original ion (ie, the gas amplification), resulting in higher output pulse. Pulse amplitude is proportional to the energy of the incident particle loss, suitable for spectroscopy measurements. Geiger counter, also known as Geiger - Muller counter or GM counter, it's a higher operating voltage, multiple ionization process, therefore the magnitude of the output pulse is high, is no longer proportional to the original ionization of the ion number, you can not amplificationdirectly be recorded. It can only measure the number of particles can not measure the energy to complete the one-pulse count a long time.Multi-wire chamber and drift chamber which is a variant of the proportional counter. Counting function, and also can distinguish between charged particles through the area. Multiwire chamber with parallel wire electrode in the working status of the proportional counter. Each root of wire and its surrounding space is equivalent to a detector, the latter connected to a recording instrument. Therefore, only when the particles to be detected into the adjacent space of the wire associated with this record instruments to record an incident. In order to reduce the number of electrode wire, from the measurement of ion drift time of the wire to determine the site of the ions, which have another detector gives a start signal and the same article, the site of the incident, according to this principle of the system into the counting device is called a drift chamber, it has a better position resolution (50 micron), but allowed count rate than the multi-wire chamber.Semiconductor detector radiation generated in the semiconductor, charge carriers (electrons andholes) in the reverse bias electric field is collected by theelectric pulse signal to measure nuclear radiation. Commonly used in silicon, germanium a semiconductor material, there are three main types: ? spraying a layer of gold film in the n-type single crystal surface barrier; ? highresistivity p-type silicon diffusion into the layer to provide electronic impurities diffused junction; ? in the p-type germanium (orsilicon) surface coating a thin layer of lithium metal and lithium-drift-type drift. HPGe detector with high energy resolution, high detection efficiency of γ radiation, can be stored at room temperature, wide range of applications. Gallium arsenide, cadmium telluride,mercuric iodide and other materials.Scintillation counter by the charged particles hit the scintillator, so that the ionization of atoms (molecules), excited in the process ofde-excitation light-emitting optoelectronic devices (such as PMT)optical signals into electrical signals that can be measured to measure nuclear radiation . Scintillation counter to distinguish between a short time, high efficiency, but also according to the size of the electrical signal determination of the energy of the particles. Scintillator can be divided into three categories: ? The inorganic scintillator, the usefulness of thallium (Tl)-activated sodium iodide NaI (Tl) and CsI CsI (Tl) crystal, electronics, γ radiation sensitive, high luminous efficiency better energy resolution, but the light decay time longer; BGO crystal density, high luminous efficiency, and thus very effectivein high-energy electrons, gamma radiation detection. Such as silver (Ag)-activated zinc sulfide ZnS (Ag) is mainly used to detect alpha particles; glass scintillator to measure alpha particles, low energy X-radiation, measurable neutron to join the carrier; barium fluoride (BaF2) density fluorescent composition, both for energy measurement, but alsofor time measurement. ? organic scintillator, including plastics,liquids and crystals (eg anthracene, stilbene, etc.), the first twouniversal. Due to their light decay time is short (2 to 3 ns, fastplastic scintillator can be less than 1 ns), commonly used in time measurement. They charged particle detection efficiency of nearly 100%. ? gas scintillator, including xenon, helium and otherinert gases, luminous efficiency is not high, but the light decaytime is shorter (<10 ns).Cerenkov counter the movement of high-speed charged particles in the transparent medium faster than light in the medium velocity, it will produce Cerenkov radiation, the radiation angle and particle velocity, thus providing a measurement of charged particle velocity detectors. Such detectors often and photomultiplier tubes used in conjunction; can be divided into a threshold-type (records only particles larger than a certain speed) and the differential equation (select only a certain speed of the particles) two.Commonly used in several counters, gas proportional scintillation cell, self-quenching streamer counter, the recent gas detector, the output pulse amplitude and time characteristics. Electromagnetic calorimeter (or the shower counter) and hadron calorimeter to measurethe high-energy electrons, gamma radiation or hadrons (see elementary particles) of energy. Provides a way for the very high identification of charged particles through a radiation counter.Tracks room to record, analyze and track radiation image measurement of nuclear radiation. The main types of nuclear emulsion cloud chamberand bubble chamber, spark chamber and the streamer chamber, solid state nuclear track detectors.The nuclear emulsion photographic emulsion can record chargedparticles to a single track. Incident particles in the latex to form a latent image center, after a chemical treatment to record the particle track can be observed under the microscope. It has an excellent position resolution skills (1 micron), large stopping power, the function is continuous and sensitive.The cloud chamber and bubble chamber so that ions generated by the incident particle groups tothe formation of condensation centers in supersaturated vapor toform droplets (cloud chamber), gasification center formation in the superheated liquid into the bubble (bubble chamber), the photographic method records, so that the charged particle tracks visible. Bubble chamber, good position resolution (good up to 10 microns), is the target, often bubble chamber vertex detector with counter used together.Spark chamber and streamer chamber devices require high voltage,when the particles enter the device to produce ionization, ion movement in the strong electric field, the formation of multiple ionization, proliferating rapidly, many times the ionization process streamer spark , so that the charged particle tracks become visible. The streamer chamber has a good time characteristics. They have good spatial resolution (about 200 microns). In addition to the available photographic records particle track, but also recording pulse signal, as the counter use.Solid state nuclear track detectors heavy charged particles hit, such as mica, a class of plastic material damage along the path, after chemical treatment (etching), the injury to expand into the voids can be observed under the microscope, suitable for detection of heavy nuclei.Obtained by the composition of the many types of detectors, magnets, electronic equipment, computers and other radiation spectrometer, a variety of physical, is the development trend of modern nuclear physics and particle detection.。
