Two sequential Compton scatters method: A new method for radiation detector dead-time measurement

Method for effective dead time measurement in counting systems

In subcritical systems driven by an external neutron source, the experimental methods based on pulsed neutron source and statistical techniques play an important role for reactivity measurement. Simulation of these methods is very time-consumed procedure. For simulations in Monte-Carlo programs several improvements for neutronic calculations have been made. This paper introduces a new method for simulation PNS and statistical measurements. In this method all events occurred in the detector during simulation are stored in a file using PTRAC feature in the MCNP. After that with a special code (or post-processing) PNS and statistical methods can be simulated. Additionally different shapes of neutron pulses and its lengths as well as dead time of detectors can be included into simulation. The methods described above were tested on subcritical assembly Yalina-Thermal, located in Joint Institute for Power and Nuclear Research SOSNY, Minsk, Belarus. A good agreement between experimental and simulated results was shown.

Proper dose measurement skills are of the utmost importance for all applications of ionizing radiation in medicine. For years, since the discovery of ionizing radiation, the delivered dose to exposed people has been evaluated by means of subjective methods. In radiotherapy, the unit “erythema dose” was widely used. The erythema dose was connected to the reaction of the skin to radiation. (Strictly: The erythyma dose is the amount of radiation which, applied to the skin, makes it turn temporarily red [erythematous]. Webster’s New World™ Medical Dictionary, 3rd Edition) In the early days of the discovery of X-rays, the Roentgen radiation was commonly used. Luckily, the Roentgen radiation deposits the maximum energy to the surface, i.e. in the case of radiotherapy to the skin. Careful observation of the redness of the skin allowed therapists to finish treatment in the right time, before a serious injury of deeper anatomical structures would occur. However, this type of measurement of delivered dose was very imprecise. It depended on the individual reaction of each single person. In 1924 an objective method, namely the unit of radiation exposure, was introduced. This unit, the Roentgen, was internationally accepted in 1928 during the II International Congress of Radiology held in Stockholm. It was based on the measurement of the ionization of air exposed to ionizing radiation. At that time the method of the measurement of charge has been well developed. The method of dose measurement, based on charge measurement has been developing for years and today is considered as the most precise and the simplest method of dose measurement. Nevertheless, new detectors and new methods of dose measurement are still developing, and, what has to be emphasized, is that there is no ideal radiation detector for all applications of ionizing radiation. In this lecture the theory of dosimetry will be presented alongside the most often used detectors in medical practice.

A method of dead time measurement

Feynman-α measurements on the fast critical zero-power reactor masurca

A method for ultra-short pulse-shape measurements using far infrared coherent radiation from an undulator

A method for ultra-short pulse-shape measurements using far infrared coherent radiation from an undulator

A modified decaying source method for dead time measurement with non-negligible background counts

Alpha–beta monitoring system based on pair of simultaneous Multi-Wire Proportional Counters

The technology on the processing and detection of the extreme ultraviolet radiation and x-ray (EUV/x-ray) optical component is one of the main categories in modern short-wave band optical research. At present, EUV/x-ray optical component are in great demand on the construction of the rapidly developed synchrotron radiant lamp-house and beam of light engineering in developed countries. Now few countries has the ability of developing this kind of optical component with super-smooth surface and high precision and the key technology is processing and detecting technique. In this paper, the author study the measurement method and instrument of the EUV/x-ray optical component, improve the design of the measuring apparatus-long trace profiler LTP already existing, provide a kind of newly long trace profiler LTP-III, which is used to measure slope error.

Innovative real-time and non-destructive method of beam profile measurement under large beam current irradiation for BNCT

Practical prototype of a cluster-counting transition radiation detector

We present a method for obtaining the line spread function (LSF) of any radiation detector from measured data. The problem of finding a LSF is essentially a discrete deconvolution from known values of the input (Monte Carlo generated data) and the output (measured data) which can be put into matrix form. We applied the total least squares (TLS) method which is particularly useful when there are errors in both the input and output data. Results from computer simulation as well as from actual data are shown. In a practical application, however, our technique is currently limited by the ability of the Monte Carlo data to simulate correctly the inherent data from the head of the linear accelerator (linac). To overcome this difficulty we have solved by deconvolution and TLS for a more realistic inherent beam profile of our linac using the information from both profile data as measured with film and the film densitometer response function. The LSF of the densitometer was estimated with a simple method of direct measurement of a slit image and a full width at half maximum (FWHM) of 0.997 mm was recorded. Additionally, using the knowledge of this realistic inherent profile of the linac, a blurring function representing the finite source size effect missing in our current Monte Carlo profile simulation was determined. Finally, with the realistic inherent beam profile we have applied the deconvolution and TLS method to find a LSF for the Markus chamber and found a resulting FWHM of 5.39 mm. The TLS approach for deconvolving can find a useful application for both finding the LSF and correcting for the detector size effect once its LSF is known. This type of correction is required when a high spatial resolution is needed (e.g., in small field off-axis measurements). Convolved and measured profiles are also presented to illustrate the effect of the blurring due to different LSFs.

High Resolution Measurement of Dose Distributions in the LEKSELL Gamma Knife

Experimental work has been carried out to demonstrate using the radiotracer method for flowrate measurement of water in a 3 inches diameter of the carbon-steel pipeline. The water was supplied from a water tank of a volume of approximately 5000 liters. The tank was connected to the pipeline through a flexible plastic hose. A ball valve was installed at the far end of the pipeline to adjust water discharge from the pipeline. None flow meters were installed on the pipeline. Iodine-131 (131I) radioisotope with a concentration of 1 mCi.mL−1 has been injected instantaneously through the injection point located at 15 meters from the water tank. Two radiation detectors (notified as D1 and D2) which had been set-up respectively at the distance of 4 m and 7 m from the injection point recorded residence time distribution (RTD) curves of the radiation intensities emitted from the injected radioisotope. During the experiment, the system was assumed time-invariant by keeping the tank was always containing full of water. The transit time calculated based on mean residence time (MRT) was 89.9 s, and the linear velocity of the water flow is 3.33 cm.s−1