121687747
A full-scale thermal model of a prototype dipole cryomagnet for theCERN LHC project
Abstract The design, construction and thermal performance of an LHC Cryostat Thermal Model are described. In place of an LHC prototype dipole cold mass a standard- cryostat houses a cold mass with the same overall dimensions, cold surface area, thermal insulation and support systems. The Cryostat Thermal Model is connected to suitably dimensioned end boxes fixing the required temperature levels, by means of saturated helium baths at 1.9 K and 4.2 K, and controlled flows of gaseous helium at 50 to 75 K. Comprehensive instrumentation and fully automatic process control and data acquisition allow precise calorimetric measurements to be performed at all temperature levels.
118122719
DESIGN, TEST AND PERFORMANCE OF THE LIQUID HELIUM CRYOSTATS FOR THE LEP SUPERCONDUCTING QUADRUPOLE MAGNETS
The experimental areas of LEP, the high-energy electron-positron collider presently under construction at CERN, will be equipped with eight superconducting quadrupole magnets, housed in liquid helium cryostats embedded in the complex detector set-ups. To comply with transverse space restrictions, the 2.5 m-long slender cryostats feature a 130 mm diameter warm bore and a horizontally-oriented service funnel at one end, equipped with 2000 A current leads. The cryostats have been designed by CERN, manufactured and assembled by industry, and tested in the laboratory. Besides design principles and constructional features, results of tests and comparative performance data are presented.
116929466
The superfluid helium model cryoloop for the CERN Large Hadron Collider (LHC)
The high-field superconducting magnets of the CERN Large Hadron Collider (LHC) will operate in static pressurized helium II at a maximum temperature of 1.9 K, irrespective of their position around the 26.7 km circumference of the machine ring. Their static and dynamic heat loads will be transported by conduction in the pressurized helium II, to a heat exchanger tube threading its way along the magnet string, in which flowing saturated helium II absorbs the heat in quasi-isothermal conditions. Following promising results obtained with heated flow tests on two-phase helium II, a full-scale 20 m-long thermohydraulic model of a LHC cryoloop was designed, built and operated, addressing key issues such as flow stability, steady-state heat transfer, transient response to varying loads, control strategies, and influence of slope. We present the results obtained and show that they validate the basic design choices of the proposed LHC cryogenic system.
55204249
A Cryogenic Axial-Centrifugal Compressor For Superfluid Helium Refrigeration
CERN's new project, the Large Hadron Collider (LHC), will use superfluid helium as coolant for its high-field superconducting magnets and therefore require large capacity refrigeration at 1.8 K. This may only be achieved by subatmospheric compression of gaseous helium at cryogenic temperature. To stimulate development of this technology, CERN has procured from industry prototype Cold Compressor Units (CCU). This unit is based on a cryogenic axial-centrifugal compressor, running on ceramic ball bearings and driven by a variable-frequency electrical motor operating under low-pressure helium at ambient temperature. The machine has been commissioned and is now in operation. After describing basic constructional features of the compressor, we report on measured performance.
133673972
Investigation and qualification of thermal insulation systems between 80-K and 4.2-K
122695581
TOWARDS COST-TO-PERFORMANCE OPTIMISATION OF LARGE SUPERFLUID HELIUM REFRIGERATION SYSTEMS
The field range of superconducting devices may be extended by lowering their operating temperature, using superfluid helium refrigeration systems which have to deliver working pressures down to 1.6 kPa. The corresponding pressure ratio can be produced by integral cold compression or using a combination of cold compressors in series together with "warm" compressors at room temperature. The optimisation of such a system depends on the number, arrangement and characteristics of cold and warm machines as well as on the operating scenario and turndown capability. The aim of this paper is to compare relative investment and operating costs of different superfluid helium cryogenic systems, with the aim of optimising their cost-to-performance ratio within the constraints of their operating scenario.
122661128
A first approach to mechanical construction and cooling of a composite 3D silicon vertex detector
Abstract This paper presents first results on mechanical and cooling studies for a 3D silicon vertex detector designed for B physics at a hadron collider. Prototype modules were built from raw silicon wafers. One module was instrumented with resistors to simulate readout electronics. Both module movement and temperature variations were recorded. A cooling method utilizing simple air/helium flow was investigated, but proved inadequate because of too large temperature anisotropies.
43442717
Recent results from Fermilab E687
Recent analyses from Fermilab fixed target photoproduction experiment 687 are summarized. Emphasis is placed on strong interaction studies performed on high statistics samples of Charm decays and light quark states. In particular, semi-leptonic measurements of form factors in Cabibbo suppressed modes are described. A Dalitz analysis of the D{sub s}{sup +}{yields}{pi}{sup +}{pi}{sup -}{pi}{sup +} has been performed and can be linked to recent results on scalar states decaying to {pi}{sup +}{pi}{sup -}. In addition, Charm-Anticharm asymmetries in high energy photoproduction have been measured. Finally, photoproduction of light quark states, such as the vector meson {rho}(1700) or the f{sub 0}(980) are discussed.
125706131
The Single Field Flip Cooling Channel for a Neutrino Factory
116622236
Beam simulation tools for GEANT4 (and neutrino source applications)
Geant4 is a tool kit developed by a collaboration of physicists and computer professionals in the High Energy Physics field for simulation of the passage of particles through matter. The motivation for the development of the Beam Tools is to extend the Geant4 applications to accelerator physics. Although there are many computer programs for beam physics simulations, Geant4 is ideal to model a beam going through material or a system with a beam line integrated to a complex detector. There are many examples in the current international High Energy Physics programs, such as studies related to a future Neutrino Factory, a Linear Collider, and a very Large Hadron Collider.
121495790
Ionization loss in BGO
Abstract We report on a precise measurement of the energy loss through ionization by pions in bismuth germanate performed at several values of the incident particles momentum with a prototype of the L3 electromagnetic calorimeter. The experimental results are in good agreement with theoretical predictions showing the relativistic rise modified by density effect.