Difference between revisions of "CLAS apparatus"
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=Tracking System= | =Tracking System= | ||
=Scintillators= | =Scintillators= | ||
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+ | The CEBAF Large Acceptance Spectrometer (CLAS) is equipped with 288 scintillator counters with photomultiplier tube on each side. | ||
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=Cherenkov detector= | =Cherenkov detector= | ||
The CLAS Cherenkov detector is a threshold gas counter filled with perfluorobutane <math>C_4 F_{10}</math> gas at atmospheric pressure. Perfluorobutane <math>C_4 F_{10}</math> was chosen for its high index of refraction n=1.00153, which results in a high photon yield and the following energy thresholds, for electrons 9 MeV and for pions it is 2.5 GeV. The Cherenkov detector is used to distinguish electrons from pions. The six superconducting coils placed at angles of 60 degrees in the azimuthal angle <math>\Phi</math> around the electron beam line produce a 5 T magnetic field.It is important to minimize the amount of material in all of the detectors to minimize hadron and electron absorption and secondary particle production upstream of the time-of-flight scintillators and calorimeters. The detector was divided in the six sectors with each sector independently instrumented to be an effective spectrometer. The Cherenkov detector was designed to maximize the coverage in each of the sectors up to an angle <math>\theta=45</math> degrees. <br> | The CLAS Cherenkov detector is a threshold gas counter filled with perfluorobutane <math>C_4 F_{10}</math> gas at atmospheric pressure. Perfluorobutane <math>C_4 F_{10}</math> was chosen for its high index of refraction n=1.00153, which results in a high photon yield and the following energy thresholds, for electrons 9 MeV and for pions it is 2.5 GeV. The Cherenkov detector is used to distinguish electrons from pions. The six superconducting coils placed at angles of 60 degrees in the azimuthal angle <math>\Phi</math> around the electron beam line produce a 5 T magnetic field.It is important to minimize the amount of material in all of the detectors to minimize hadron and electron absorption and secondary particle production upstream of the time-of-flight scintillators and calorimeters. The detector was divided in the six sectors with each sector independently instrumented to be an effective spectrometer. The Cherenkov detector was designed to maximize the coverage in each of the sectors up to an angle <math>\theta=45</math> degrees. <br> |
Revision as of 05:05, 15 August 2007
Apparatus
Target
The target materials used in the EG1b experiments were
To prepare the target material, ammonia gas was frozen at 77 K and then crushed into little
pieces, about 1-3 mm in diameter. In the case of deuterated ammonia was used. The target are kept in solid form during the experiment by liquid helium.
Tracking System
Scintillators
The CEBAF Large Acceptance Spectrometer (CLAS) is equipped with 288 scintillator counters with photomultiplier tube on each side.
Cherenkov detector
The CLAS Cherenkov detector is a threshold gas counter filled with perfluorobutane
As a light collector were used the system of mirrors , the light collecting cones and photomultiplier tubes(PMTs). In the extreme regions of the angular acceptance of the spectrometer the number of detected photoelectrons is too low. To get acceptable efficiency of the detector in these regions were placed photomultiplier tubes.
The charged particle trajectories are in planes of almost constant azimuthal angle, because of the toroidal configuration of the magnetic field. Under this conditions, the light collection can be designed to focus the light in the azimuthal angle direction. However, the polar angle is constant. Each of the six sectors was divided into 18 regions of the polar angle
The optical elements of each
The photomultiplier tubes were surrounded with high permeability magnetic fields,because they were located in the fringe field region of the spectrometer(??????).
Below is shown the scheme of CLAS detector