Variation of Ge-detector efficiency with source diameter and radial source position

1983 ◽  
Vol 34 (8) ◽  
pp. 1105-1108 ◽  
Author(s):  
R.G. Helmer
Keyword(s):  
Detector Efficiency ◽  
Source Position ◽  
Ge Detector

Optimization of Dead-Layer Thickness for a HPGe Detector Using UCODE-MCNP Codes

2009 ◽  
Author(s):  
Noha Shaaban ◽  
Wael El Gammal ◽  
Hesham Nasif
Keyword(s):  
Construction Materials ◽  
Simulated Data ◽  
Dead Layer ◽  
Detector Efficiency ◽  
Physical Measurements ◽  
Inverse Models ◽  
Hpge Detectors ◽  
Dead Layer Thickness ◽  
Ge Detector ◽  
The Dead

The use of modeling programs to predict the response of HPGe detectors is increasing in importance due to the extensive laboratory work, both in term of source preparations and measuring time. MCNP code is a powerful and useful tool for the simulation of Ge-detector efficiency calibration. The experimental efficiency data and MCNP calculations based only on the known physical measurements of the HPGe crystal do not agree well in some detectors. Detector construction materials and surface dead layers must be well specified. The dead layer of Ge detector is one of the most important factors that affect the calculations. In addition, and if provided by the manufacturer, the dead layer may changes with time. Consequently, it is necessary to optimize the thickness of the detector’s dead layer in order to obtain more accurate results for the efficiency of the detector using Monte Carlo calculations. Our approach consists of employing hybrid UCODE-MCNP codes to optimize the dead layer of the Ge-crystal aiming at decreasing discrepancies between experimental and simulated data of the Ge detector efficiency. UCODE has two attributes that are not jointly available in other inverse models: (1) the ability to work with any mathematically based model or pre- or post processor with ASCII or text only input and output files, and (2) the inclusion of more informative statistics.

Development of a conical anode Fe-gun for low voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 978-979
Author(s):  
T. Miyokawa ◽  
S. Norioka ◽  
S. Goto
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Irradiation Damage ◽  
Cold Cathode ◽  
Virtual Source ◽  
Source Position ◽  
Electrostatic Lens ◽  
Electrostatic Lenses ◽  
Wide Range

Field emission SEMs (FE-SEMs) are becoming popular due to their high resolution needs. In the field of semiconductor product, it is demanded to use the low accelerating voltage FE-SEM to avoid the electron irradiation damage and the electron charging up on samples. However the accelerating voltage of usual SEM with FE-gun is limited until 1 kV, which is not enough small for the present demands, because the virtual source goes far from the tip in lower accelerating voltages. This virtual source position depends on the shape of the electrostatic lens. So, we investigated several types of electrostatic lenses to be applicable to the lower accelerating voltage. In the result, it is found a field emission gun with a conical anode is effectively applied for a wide range of low accelerating voltages.A field emission gun usually consists of a field emission tip (cold cathode) and the Butler type electrostatic lens.

ADAPTAÇÃO E APLICAÇÃO DE MÉTODOS DE INTELIGÊNCIA COMPUTACIONAL PARA A ESTIMAÇÃO DE UMA FONTE DE POLUENTES EM ESTUÁRIOS

Engevista ◽  
2014 ◽  
Vol 17 (2) ◽  
pp. 152
Author(s):  
Radael De Souza Parolin ◽  
Pedro Paulo Gomes Watts Rodrigues ◽  
Antônio J. Silva Neto
Keyword(s):  
Computational Intelligence ◽  
Computational Models ◽  
Source Position ◽  
Iterative Search ◽  
Contaminant Source ◽  
Resources Management ◽  
Search Spaces ◽  
Grid Points ◽  
Computational Intelligence Methods

The quality of a given water body can be assessed through the analysis of a number of indicators. Mathematical and computational models can be built to simulate the behavior of these indicators (observable variables), in such a way that different scenarios can be generated, supporting decisions regarding water resources management. In this study, the transport of a conservative contaminant in an estuarine environment is simulated in order to identify the position and intensity of the contaminant source. For this, it was formulated an inverse problem, which was solved through computational intelligence methods. This approach required adaptations to these methods, which had to be modified to relate the source position to the discrete mesh points of the domain. In this context, two adaptive techniques were developed. In one, the estimated points are projected to the grid points, and in the other, points are randomly selected in the iterative search spaces of the methods. The results showed that the methodology here developed has a strong potential in water bodies’ management and simulation.

scholarly journals The optimum orientation of an absorbing barrier

2005 ◽  
Vol 461 (2060) ◽  
pp. 2369-2383 ◽  
Author(s):  
A.D Rawlins
Keyword(s):  
Noise Level ◽  
Noise Source ◽  
Shadow Region ◽  
Source Position ◽  
Absorbent Material ◽  
Noise Barrier ◽  
Receiver Point

In the following work, we solve the problem of the best orientation of a rigid noise barrier, which has one face lined with absorbent material, between a noise source and a receiver point in the shadow region of the barrier. By the ‘best orientation’, we mean that positioning of the barrier which yields the least noise level at the receiving point for a given barrier and source position.

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