A mixed columnar-equiaxed solidification model is used to predict the macrosegregation in high grade steel ingots. In this model, three phases are considered: the melt; the columnar phase, which is ...assumed to be stationary; and the equiaxed phase, which is free to move. With this approach, the model is able to simulate the evolution of the primary solid phase distributions including the columnar-to-equiaxed transition, the melt convection and the grain sedimentation, and their influence on the macrosegregation. Thermodynamic information of a ternary alloy (Fe-C-Cr) is simplified by the piecewise linearization of the phase diagram around the suitable compositions in the ferritic and austenitic regions. As a result, macrosegregation of carbon and chromium has been analyzed. As the first step, the validation of the numerical model was performed on a benchmark ingot of a laboratory scale. Computed macrosegregation and primary structure were compared with measurements and good agreement was obtained.
Status and characterisation of COMPASS RICH-1 Albrecht, E.; Baum, G.; Birsa, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2005, Letnik:
553, Številka:
1
Journal Article
Recenzirano
COMPASS RICH-1, a gas-radiator RICH detector with large transversal dimensions, which makes use of MWPC with CsI photocathodes as photon detectors, is in operation at COMPASS since 2001. The ...behaviour of the detector components is optimised and fully understood. The characterisation of the detector is now complete. We report about the detector status and its response in the COMPASS environment.
VUV absorbing vapours in n-perfluorocarbons Albrecht, E.; Baum, G.; Bellunato, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2003, Letnik:
510, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The optical transparency of perfluorocarbons used as Cherenkov media is of prime importance to many Ring Imaging Cherenkov detectors. We will in this paper show that the main photon absorbers in ...these fluids are hydrocarbons with double or triple bonds. We will moreover discuss a process which can eliminate these pollutants and restore the intrinsic excellent optical transparency of these fluids in the VUV range.
COMPASS RICH-1 Albrecht, E.; Baum, G.; Birsa, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2003, Letnik:
502, Številka:
1
Journal Article
Recenzirano
RICH-1 is a large acceptance gaseous RICH using 3m of C4F10 as radiator and MWPCs with CsI photo-cathodes as VUV photon detectors. The main characteristics of this RICH are the large acceptance and ...the use of far UV photon detectors, which implies large dimensions, UV transparencies of the elements up to the photo-cathode, and good UV mirror reflectance.
We give a description of the detector, first results about its performances and a report about various technological achievements required by this challenging project.
The radiator gas and the gas system of COMPASS RICH-1 Albrecht, E.; Baum, G.; Bellunato, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2003, Letnik:
502, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The design of the COMPASS RICH-1 gas system, its operational modes, the cleaning setups for the preparation of the radiator gas and transmission measurement installations are described. The gas ...system in presently fully operational and satisfactory transmission of VUV light through the radiator gas has been reached.
The mirror system of COMPASS RICH-1 Albrecht, E.; Baum, G.; Birsa, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2003, Letnik:
502, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The architecture and the properties of the mirror system of the COMPASS RICH-1 detector, composed by 116 spherical VUV reflecting units supported by a lightweight mechanical structure, are described.
First performances of COMPASS RICH-1 Albrecht, E.; Baum, G.; Bellunato, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2004, Letnik:
518, Številka:
1
Journal Article
Recenzirano
Odprti dostop
COMPASS RICH-1, designed in 1996 for hadron identification at high momenta in the COMPASS large angle spectrometer, is based on the use of MWPCs with large size CsI photon detectors. This choice, ...dictated by technical and economical considerations, has imposed VUV requirements for mirror reflectance and radiator transparency.
The detector is now fully operative and its preliminary performances are presented.
The COMPASS RICH-1 read-out system Baum, G.; Birsa, R.; Bradamante, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2003, Letnik:
502, Številka:
1
Journal Article
Recenzirano
Odprti dostop
This paper describes the reconfigurable read-out system for the 82944 RICH-1 channels of the COMPASS experiment (NA58) at CERN. The system is based on 192 identical large front-end boards (BORA ...board). BORA was designed for acquiring, digitizing, threshold subtracting and transmitting event data. The overall operation of the board is controlled and supervised by a DSP tightly interacting with an FPGA that acts as a parallel co-processor. The DSP allows characterizing each analog channel by locally calculating noise and pedestal. Each BORA communicates with the outside world through two optical fibers and through a dedicated DSP network. One optical fiber is used to receive event triggers, and the other one is used to transmit event data to subsequent processing stages of the acquisition system. The DSP network allows reconfiguring and reprogramming the DSPs and FPGAs as well as acquiring sample events to visualize the overall operation of the system. The whole RICH has eight DSP networks working in parallel. These networks are handled by DOLINA, a PC resident multiprocessor board containing eight DSPs. Each network is formed by 24 BORA DSPs and 1 DOLINA DSP. The read-out system can steadily work up to a trigger rate of 75kHz with maximum pixel occupancy of 20%, reaching a transmission data rate of 5.13Gbytes/s.
Results from COMPASS RICH-1 Albrecht, E.; Baum, G.; Birsa, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2004, Letnik:
535, Številka:
1
Journal Article
Recenzirano
COMPASS RICH-1, designed in 1996 for hadron identification at high momenta in the COMPASS large angle spectrometer, is a large acceptance gaseous RICH with a 3
m thick
C
4
F
10
radiator. MWPCs with ...CsI photocathodes are used as VUV photon detectors and the image focalization is provided by a large UV mirror wall.
π
/K are separated in the several 10
GeV/
c
domain.
The main characteristics of the detector are the large acceptance resulting in very large transversal dimensions, the use of far UV photon detectors, which implies VUV transparency of the radiator gas and good VUV mirror reflectance and the high rate capabilities, made possible by the read-out system architecture.
The detector description, the various technological achievements and present performances are given. In particular, preliminary RICH-1 performances obtained analysing the data from the 2002 and 2003 runs are presented.
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