S800 Documentation

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start [2013/09/24 21:25]
pereira 		start [2013/09/30 21:05]
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-**The S800 spectrograph**+====== Technical Aspects of the S800 ====== 
 + 
 +===== Technical Introduction ===== 
 + 
 +==== General ==== 
 +The S800 [1] is a superconducting spectrograph used for reaction studies with high-energy radioactive beams produced at the NSCL Coupled-Cyclotron Facility (CCF) and the A1900 Separator [2]. It was designed for high-precision measurements of scattering angles (ΔΘ=2 msr) and momentum (p/Δp=2×10<sup>4</sup>), and large momentum and solid-angle acceptances (ΔΩ=20 msr, Δp/p=6%). The S800 layout is shown in [[start|Fig. 1]]. It consists of two parts: the analysis line and the spectrograph.  
 + 
 +{{:wiki:s800_layout.png|}} 
 + 
 +==== Analysis Line ==== 
 +The analysis line extends from the object position to the target station, with a total length of 22 m. It includes four 22.5° dipoles, five quadrupole triplets, and two vertically steering magnets, assembled in two segments with configurations QQQ-H-DD-QQQ (segment 6) and QQQ-DD-H-QQQ-QQQ (segment 7) symmetrically oriented around an intermediate image plane. The maximum rigidity is 5 Tm, although it depends on the tune of the quadrupoles. The acceptances of the analysis line depends on the optical mode. 
 + 
 + 
 +==== Spectrograph ==== 
 +The spectrograph consist of two quadrupoles, a sextupole and two big dipoles assembled in a QQ-S-DD configuration (segment 8) that spans vertically from the target station to the focal plane, with a total length of 18 m. The figures of merit of the spectrograph are summarized in Table 1. Achieving the nominal angle and momentum resolution require the control of different conditions such as object size (less than 0.5 mm), target thickness, uncertainty of the incident angle on the target, intensity, and whether or not the incoming beam needs to be tracked.  
 + 
 + 
 + 
 +^ Momentum Resolution (p/Δp)      | 2×10<sup>4</sup> |  
 +^ Momentum Acceptance             | 5.8%             |  
 +^ Angle Resolution                | 2 msr            | 
 +^ Solid Angle Acceptance          | 7º×10º or 20 msr | 
 +^ Momentum Dispersion (x/δ)       | 9.5 cm/%         |    
 +^ Angle Dispersion (y/b)          | 0.9 mm/mrad      |    
 +^ Magnification(x/x)              | 0.74             |  
 +^ Focal Plane Size (x × y)        | 55 cm ×15 cm     |  
 +^ Maximum Rigidity                | 4 Tm             |  
 +^ Detector Position Resolution (x)| 0.3 mm           | 
 +^ Detector Position Resolution (y)| 0.3 mm           | 
 + 
 + 
 + 
 +====== Headline ====== 
 +====== Headline ====== 
 + 
 +====== Headline ====== 
 +====== Level 1 Headline ====== 
 +===== Level 2 Headline ===== 
 +==== Level 3 Headline ==== 
 +=== Level 4 Headline === 
 +== Level 5 Headline == 
 + 
 +---- 
 +∑ 
 +  * Unordered List Item 
 +  *   * Unordered List Item 
 +  *   * Unordered List Item 
 +  *   *   * Unordered List Item 
 +* Technical Introduction
  
-  * Technical Introduction 
   * Ion optics   * Ion optics
   * Detectors   * Detectors
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 DETECTORS DETECTORS
 +
 The standard detection system of the S800 includes a plastic scintillator at the object station; two tracking detector at the detector station in the Intermediate Image plane; a pair of cathode readout drift chambers (CRDC) located about 1 m apart; a multi-segmented ion chamber, and four large plastic scintillators of thicknesses 3 mm, 5 cm, 10 cm and 20 cm, respectively. The standard detection system of the S800 includes a plastic scintillator at the object station; two tracking detector at the detector station in the Intermediate Image plane; a pair of cathode readout drift chambers (CRDC) located about 1 m apart; a multi-segmented ion chamber, and four large plastic scintillators of thicknesses 3 mm, 5 cm, 10 cm and 20 cm, respectively.
  
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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)  × 56 cm (dispersive direction), and it is filled with a gas mixture consisting of 80% CF4 and 20% C4H10 at a typical pressure of 50 torr. A schematic view of a CRDC can be seen in Fig xxx, and their technical specifications are listed in Table xxx. Each detector consists of two windows mounted on frames, two printed circuit boards (PCB) and an anode frame.  Each PCB is made of un-masked G-10, and includes a field shaping foil to ensure a uniform field in the active region of the detector. Two G-10 spacers are laminated to the board on each side. The shaping foils are made of 1.9-mm pitch evaporated aluminum strips perpendicularly oriented to the electric field. The anode frame includes a glued cathode grounding plane, an anode wire running across the field, and a Frisch grid. Cathode pads are located in front of and behind the anode wire. The pads have a pitch of 2.54 mm. The anode frame is sandwiched between the two printed circuit boards with two spacers in between, as shown in Fig. xxx.  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)  × 56 cm (dispersive direction), and it is filled with a gas mixture consisting of 80% CF4 and 20% C4H10 at a typical pressure of 50 torr. A schematic view of a CRDC can be seen in Fig xxx, and their technical specifications are listed in Table xxx. Each detector consists of two windows mounted on frames, two printed circuit boards (PCB) and an anode frame.  Each PCB is made of un-masked G-10, and includes a field shaping foil to ensure a uniform field in the active region of the detector. Two G-10 spacers are laminated to the board on each side. The shaping foils are made of 1.9-mm pitch evaporated aluminum strips perpendicularly oriented to the electric field. The anode frame includes a glued cathode grounding plane, an anode wire running across the field, and a Frisch grid. Cathode pads are located in front of and behind the anode wire. The pads have a pitch of 2.54 mm. The anode frame is sandwiched between the two printed circuit boards with two spacers in between, as shown in Fig. xxx. 
  
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 Ionization Chamber Ionization Chamber
 +
 An ionization chamber downstream of both CRDCs is used to identify the Z number of the transmitted nuclei from their energy loss. The detector has an active volume of xxx cm x xxx cm x xxx cm and is filled with P10 gas at a typical pressure of 300 torr, although this value can be increased up to 600 torr for light nuclei. A technical layout of the detector is shown in Fig. Table xxx lists some of the technical specifications. The detector consists of 16 stacked-parallel plate ion chambers with narrow anode-cathode gaps, placed along the detector’s central axis. Each anode is sandwiched by two cathodes foils made of aluminum evaporated mylar.  An ionization chamber downstream of both CRDCs is used to identify the Z number of the transmitted nuclei from their energy loss. The detector has an active volume of xxx cm x xxx cm x xxx cm and is filled with P10 gas at a typical pressure of 300 torr, although this value can be increased up to 600 torr for light nuclei. A technical layout of the detector is shown in Fig. Table xxx lists some of the technical specifications. The detector consists of 16 stacked-parallel plate ion chambers with narrow anode-cathode gaps, placed along the detector’s central axis. Each anode is sandwiched by two cathodes foils made of aluminum evaporated mylar. 
  
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 Tracking Parallel Plate Avalanche Counters Tracking Parallel Plate Avalanche Counters
 +
 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 intermediate image plane of the 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 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 intermediate image plane of the 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 dipole magnets downstream of the intermediate image plane filter the particles produced  in the tracking detectors, which would otherwise contaminate the data. 
 Each TPPAC has an active area of 10 cm × 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, with a pitch of 1.27 mm. Each TPPAC has an active area of 10 cm × 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, with a pitch of 1.27 mm.
start.txt · Last modified: 2024/01/02 12:45 by pereira

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