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detectors [2013/12/13 18:34]
pereira |
detectors [2013/12/13 18:37]
pereira [Tracking Parallel Plate Avalanche Counters (TPPAC)] |
| Some experiments are particularly sensitive to the incoming positions and angles of the nuclei impinging on the target. Two tracking parallel plate avalanche counters (TPPAC) are installed in the [[Stations#Intermediate Plane|intermediate plane station]] of the [[Introduction#Analysis Line|analysis line]]. The position and angles measured with both TPPACs are transformed into the corresponding coordinates in front of the target, using the transfer matrix of the second half of the analysis line. The analysis line [[Magnets#Spectrograph Dipole|dipole magnets]] downstream of the intermediate image plane filter the particles produced in the tracking detectors, which would otherwise contaminate the data. | Some experiments are particularly sensitive to the incoming positions and angles of the nuclei impinging on the target. Two tracking parallel plate avalanche counters (TPPAC) are installed in the [[Stations#Intermediate Plane|intermediate plane station]] of the [[Introduction#Analysis Line|analysis line]]. The position and angles measured with both TPPACs are transformed into the corresponding coordinates in front of the target, using the transfer matrix of the second half of the analysis line. The analysis line [[Magnets#Spectrograph Dipole|dipole magnets]] downstream of the intermediate image plane filter the particles produced in the tracking detectors, which would otherwise contaminate the data. |
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| Each TPPAC has an active area of 10 cm x 10 cm and is filled with isobutane at a typical __pressure of 5 torr__. The detector consists of a cathode foil with a series of aluminum strips oriented in the non-dispersive direction, followed by an anode plate and a second cathode foil with the strips oriented in the dispersive direction (see [[Fig xxx]]). A total of 128 pads are connected to the strips of each cathode foil. The x and y positions are determined from the charge distribution on the pads. The position calibration was done using the pad pitch of 1.27 mm. | Each TPPAC has an active area of 10 cm x 10 cm and is filled with isobutane at a typical __pressure of 5 torr__. The detector consists of a cathode foil with a series of aluminum strips oriented in the non-dispersive direction, followed by an anode plate and a second cathode foil with the strips oriented in the dispersive direction. A total of 128 pads are connected to the strips of each cathode foil. The x and y positions are determined from the charge distribution on the pads. The position calibration was done using the pad pitch of 1.27 mm. |
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| The particles transmitted through the TPPAC ionize the gas, producing electrons and positive ions. The drift of electrons towards the central anode plane induces an image charge on the aluminum strips. The signal generated on a given pad is sent to a preamplifier, and processed by a switch capacitor array (SCA), which acts as an analogic memory. Since the signals of this detector are generated before a valid trigger occurs, they need to be temporarily recorded until the trigger is received. The SCA samples the signals from the detector with a period of 200 ns and saves the data on a continuous mode, generating an analogic buffer. When a valid trigger is received, the sampling stops and the SCA pointer moves back in the buffer by a number of samplings pre-defined according to the time passed between the tracking signal and the valid trigger. In this way, the valid trigger is correlated with the tracking signal corresponding to the same event. The reading algorithm is lead by the FPGA chips of a [[http://wwwp.cord.edu/dept/physics/mona/manuals/XLM72UM.pdf|XLM72]] VME module. The TPPACs can work at maximum rates in the range from | The particles transmitted through the TPPAC ionize the gas, producing electrons and positive ions. The drift of electrons towards the central anode plane induces an image charge on the aluminum strips. The signal generated on a given pad is sent to a preamplifier, and processed by a switch capacitor array (SCA), which acts as an analogic memory. Since the signals of this detector are generated before a valid trigger occurs, they need to be temporarily recorded until the trigger is received. The SCA samples the signals from the detector with a period of 200 ns and saves the data on a continuous mode, generating an analogic buffer. When a valid trigger is received, the sampling stops and the SCA pointer moves back in the buffer by a number of samplings pre-defined according to the time passed between the tracking signal and the valid trigger. In this way, the valid trigger is correlated with the tracking signal corresponding to the same event. The reading algorithm is lead by the FPGA chips of a [[http://wwwp.cord.edu/dept/physics/mona/manuals/XLM72UM.pdf|XLM72]] VME module. The TPPACs can work at maximum rates in the range from |
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| ===== Cathode Readout Drift Chambers (CRDC) ===== | ===== Cathode Readout Drift Chambers (CRDC) ===== |
| Two Cathode Readout Drift Chamber (CRDC) are used to measure the transversal positions and angles in the focal plane. The first detector (CRDC1) is located at the nominal optical focal plane, and it is separated 1 m from the second downstream detector (CRDC2). Each detector has an active depth of 1.5 cm, an active area of 26 cm (non-dispersive direction) x 56 cm (dispersive direction), and it is filled with a gas mixture consisting of 80% CF<sub>4</sub> and 20% C<sub>4</sub>H<sub>10</sub> at a typical pressure of __50 torr__. The operating high power depends on the charge of the measured nuclei. A schematic view of a CRDC can be seen in the figure below. | Two Cathode Readout Drift Chamber (CRDC) are used to measure the transversal positions and angles in the focal plane. The first detector (CRDC1) is located at the nominal optical focal plane, and it is separated 1 m from the second downstream detector (CRDC2). Each detector has an active depth of 1.5 cm, an active area of 26 cm (non-dispersive direction) x 56 cm (dispersive direction), and it is filled with a gas mixture consisting of 80% CF<sub>4</sub> and 20% C<sub>4</sub>H<sub>10</sub> at a typical pressure of 50 torr. The operating high power depends on the charge of the measured nuclei. A schematic view of a CRDC can be seen in the figure below. |
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| {{:wiki:crdc-drawing.jpg?600|Schematic view of the two S800 CRDCs.}} | {{:wiki:crdc-drawing.jpg?600|Schematic view of the two S800 CRDCs.}} |
