Detection of low energy positive ions by scintillation methods

This thesis deals with the feasibility of efficiently detecting low energy positive ions, those with energies of less than several hundred electron volts, using phosphors. The scintillation technique, first used visually and greatly improved in the last ten years by the use of a photomultiplier tube, has greatly advanced detection in high energy fields. The photomultiplier is capable of delivering milliampere pulses of current of short duration and these can be registered directly by the many electronic devices currently in use. Extensive work has been done with phosphors which scintillate under which energy bombardment, due in part to their wide use in the television industry, but very little is known of their use for the detection of low energy positive ions --Introduction, page1

The Simple Assurance Argument Interchange Format (SAAIF) Manual

This document describes the Simple Assurance Argument Interchange Format, a proposed meta-model for describing structured assurance arguments. We describe the syntax and semantics of the model elements, compare the meta-model to existing argument formats, and give an example to illustrate its use

An Investigation of Proposed Techniques for Quantifying Confidence in Assurance Arguments

The use of safety cases in certification raises the question of assurance argument sufficiency and the issue of confidence (or uncertainty) in the argument's claims. Some researchers propose to model confidence quantitatively and to calculate confidence in argument conclusions. We know of little evidence to suggest that any proposed technique would deliver trustworthy results when implemented by system safety practitioners. Proponents do not usually assess the efficacy of their techniques through controlled experiment or historical study. Instead, they present an illustrative example where the calculation delivers a plausible result. In this paper, we review current proposals, claims made about them, and evidence advanced in favor of them. We then show that proposed techniques can deliver implausible results in some cases. We conclude that quantitative confidence techniques require further validation before they should be recommended as part of the basis for deciding whether an assurance argument justifies fielding a critical system

Thermal Analysis of the Divertor Primary Heat Transfer System Piping During the Gas Baking Process

A preliminary analysis has been performed examining the temperature distribution in the Divertor Primary Heat Transfer System (PHTS) piping and the divertor itself during the gas baking process. During gas baking, it is required that the divertor reach a temperature of 350 C. Thermal losses in the piping and from the divertor itself require that the gas supply temperature be maintained above that temperature in order to ensure that all of the divertor components reach the required temperature. The analysis described in this report was conducted in order to estimate the required supply temperature from the gas heater

The international school psychology survey: Data from Australia, China, Germany, Italy and Russia

Using the International School Psychology Survey (ISPS) this study aims to advance our knowledge of the characteristics, training, roles and responsibilities, challenges and research interests of school psychologists around the world. Data are presented from five countries; Australia, China (Hong Kong), Germany, Italy and Russia. The ISPS contributes valuable information regarding the profession of school psychology in each of these countries. Building upon the ISPS data previously gathered in Albania, Cyprus, Estonia, Greece and Northern England, this study yields additional information regarding the training, roles, responsibilities and contexts of school psychologists. Information from international colleagues provides unique insights regarding similarities, differences and diversity among school psychologists in different countries. © 2006 SAGE Publications.postprin

Comparison of Alternatives to the 2004 Vacuum Vessel Heat Transfer System

A study comparing different alternatives for the Vacuum Vessel Primary Heat Transfer System has been completed. Three alternatives were proposed in a Project Change Request (PCR-190) by relocating the heat exchangers (HXs) from the roof of the Tokamak building to inside the Vacuum Vessel Pressure Suppression System (VVPSS) tank. The study evaluated the three alternatives and recommended modifications to one of them to arrive at a preferred configuration that included relocating the HXs inside the Tokamak building but outside the VVPSS tank as well as including a small safety-rated pump and HX in parallel to the main circulation pump and HX. The Vacuum Vessel (VV) Primary Heat Transfer System (PHTS) removes heat generated in the VV during normal operation (10 MW, pulsed power) as well as the decay heat from the VV itself and from the structures/components attached to the VV (first wall, blanket, and divertor {approx}0.48 MW peak). Therefore, the VV PHTS has two safety functions: (1) contain contaminated cooling water (similar to the other PHTSs) and (2) provide passive cooling during an accident event. The 2004 design of the VV PHTS consists of two independent loops, each loop cooling half of the 18 VV segments with a nominal flow of 475 kg/s of water at about 1.1 MPa and 100 C. The total flow for both loops is 950 kg/s. Both loops are required to remove the heat load during normal plasma operation. During accident conditions, only one loop is needed to remove by natural convection (no pump needed) the decay heat of the complete VV and attached components. The heat is transferred to heat exchanger (HXs) located on top of the roof, outside the Tokamak building. These HXs are air-to-water (A/W) HXs. Three alternatives have been proposed for this cooling system. For a detailed discussion of these alternatives, please refer to Project Change Request, PCR-190 (Ref. 1). A brief introduction is given here. Alternative 1 includes only one main forced circulation loop with a small safety-rated pump in parallel with the main circulation pump. In addition, this alternative has two natural circulation safety loops. Both the safety and main loops supply water to the bottom of the VV with six branch lines and collect the heated water at the top of the vessel through six branches. The distribution headers are located in the lower pipe chase and the collection headers in the upper pipe chase. Each of these loops (one main and two emergency) has a HX mounted in the Vacuum Vessel Pressure Suppression System (VVPSS) tank. The main HX is cooled using either Component Cooling Water System (CCWS) or Chilled Water System (CHWS) water, and the emergency HXs are cooled by natural circulation of the VVPSS water. See Fig. 1 taken from PCR-190. Alternative 2 is exactly the same as Alternative 1 except that there is only one emergency loop and one emergency HX. See Fig. 2 taken from PCR-190. Alternative 3 also has one main forced circulation loop with a small safety-rated pump in parallel with the main circulation pump and one natural circulation safety loop. In this case, both the safety and main loops supply water to the top of the VV with three branch lines and collect the heated water at the top of the vessel through three branches. Here, the distribution header is located in the upper pipe chase as is the collection header. As before, each of these loops has a HX mounted in the VVPSS tank. The main HX is cooled using either CCWS or CHWS water, and the emergency HXs are cooled by natural circulation of the VVPSS water. See Fig. 3 taken from PCR-190. The preferred configuration is developed by selecting specific attributes of the other configurations analyzed and the logic for selecting this configuration is discussed at the end of the document. It is a modification of Alternative 2 that eliminates the separate safety loop, but incorporates a small safety rated HX and pump in parallel with the main HX and pump. It uses 18 inlet and 18 outlet branches (as did the 2004 design) and locates the HXs outside of the VVPSS tank. Tables 1 and 2 examine alternatives to the 2004 VV heat transfer system design that were proposed in PCR-190, as well as the preferred option