10 research outputs found
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Superconducting tunnel junction array development for high-resolution energy-dispersive x-ray spectroscopy
Cryogenic energy-dispersive x-ray detectors are being developed because of their superior energy resolution ((less than or equal to) 10 eV FWHM for keV x rays) compared to semiconductor EDS systems. So far, their range of application is limited due to their comparably small size and low count rate. We present data on the development of superconducting tunnel junction (STJ) detector arrays to address both of these issues. A single STJ detector has a resolution around 10 eV below 1 keV and can be operated at count rates of order 10,000 counts/s. We show that the simultaneous operation of several STJ detectors does not diminish their energy resolution significantly, while increasing the detector area and the maximum count rate by a factor given by the total number of independent channels
Campbell Penetration Depth of a Superconductor in the Critical State
The magnetic penetration depth was measured in the presence
of a slowly relaxing supercurrent, . In single crystal
below approximately 25 K, is
strongly hysteretic. We propose that the irreversibility arises from a shift of
the vortex position within its pinning well as changes. The Campbell length
depends upon the ratio where is the critical current defined
through the Labusch parameter. Similar effects were observed in other cuprates
and in an organic superconductor
Penetration of Josephson vortices and measurement of the c-axis penetration depth in : Interplay of Josephson coupling, surface barrier and defects
The first penetration field H_{J}(T) of Josephson vortices is measured
through the onset of microwave absorption in the locked state, in slightly
overdoped single crystals (T_{c} ~ 84
K). The magnitude of H_{J}(T) is too large to be accounted for by the first
thermodynamic critical field H_{c1}(T). We discuss the possibility of a
Bean-Livingston barrier, also supported by irreversible behavior upon flux
exit, and the role of defects, which relates H_{J}(T) to the c-axis penetration
depth . The temperature dependence of the latter, determined by
a cavity perturbation technique and a theoretical estimate of the
defect-limited penetration field are used to deduce from H_{J}(T) the absolute
value of .Comment: 9 pages, 6 figure
A software architecture for remote participation at the Textor-94 experiment
The Trilateral Euregio Cluster (TEC) is a collaboration between three plasma-physics institutes: the Laboratory for Plasma Physics at the Koninklijke Militaire School (KMS) in Brussels, Belgium, the FOM Institute for Plasma Physics in Rijnhuizen, the Netherlands and the Institute for Plasma Physics at the Forschungszentrum, Julich (FZJ) in Germany. They jointly perform nuclear fusion experiments at the tokamak reactor \u27Textor-94\u27 in Julich. Currently, scientists from FOM and KMS have to be physically present at the Textor-94 control room to participate in experiments, To show that remote participation is feasible, the Dynacore project built a software demonstrator that allows scientists to view measurement data, control measurement equipment and view the status of Textor-94. The demonstrator uses Java applets as clients, C + + servers, and CORBA for communication. The chosen architecture has the following advantages. It is portable, modular and reusable, eases collaboration in software development and optimizes for performance over the Internet. We solved the problems we had with applet security policies, the performance of our design and the integration of legacy systems. Our demonstrator shows that remote participation is feasible. The reactions from potential users are very positive. However, the demonstrator has to be improved for real usage in the future. (C) 2001 Elsevier Science B.V. All rights reserved
The TEC Web-Umbrella
The TEC community operates the TEXTOR device and in doing so collects and stores data from a number of different front-end acquisition systems, processing codes and analysis systems. Due to the evolution of these systems in the past, different, distributed data storage technologies were used to record this data. In an attempt to reduce the number of interfaces client codes have to use when accessing data from these data stores, an "umbrella" concept was developed: a software-layer that covers (as an "umbrella") as many as possible of these stores and provides a unified access mechanism to them. We explored the possibility of using the widely supported HTTP protocol for this purpose; this is the core protocol of the World-Wide-Web and it is capable of transporting almost any type of data. The concepts behind using this protocol were based on earlier work at JET. Access via this umbrella has been provided to the most important data stores around TEXTOR and access to others is being added regularly. Clients codes, libraries and programs have been developed for several user environments. The HTTP based concepts and the data-access via this system have been found to be highly portable. This paper gives an overview of the TEC Web-Umbrella. system, it describes the basic concepts of this system and it presents some of the client-side codes and programs. The paper also reports on some first (tentative) user experiences with it. (C) 2002 Elsevier Science B.V. All rights reserved
The TEC Web-Umbrella
The TEC community operates the TEXTOR device and in doing so collects and stores data from a number of different front-end acquisition systems, processing codes and analysis systems. Due to the evolution of these systems in the past, different, distributed data storage technologies were used to record this data. In an attempt to reduce the number of interfaces client codes have to use when accessing data from these data stores, an "umbrella" concept was developed: a software-layer that covers (as an "umbrella") as many as possible of these stores and provides a unified access mechanism to them. We explored the possibility of using the widely supported HTTP protocol for this purpose; this is the core protocol of the World-Wide-Web and it is capable of transporting almost any type of data. The concepts behind using this protocol were based on earlier work at JET. Access via this umbrella has been provided to the most important data stores around TEXTOR and access to others is being added regularly. Clients codes, libraries and programs have been developed for several user environments. The HTTP based concepts and the data-access via this system have been found to be highly portable. This paper gives an overview of the TEC Web-Umbrella. system, it describes the basic concepts of this system and it presents some of the client-side codes and programs. The paper also reports on some first (tentative) user experiences with it. (C) 2002 Elsevier Science B.V. All rights reserved