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- | **The S800 spectrograph** | + | ====== |
+ | Welcome to the wiki page of the NSCL S800 spectrograph. The page provides technical information about the S800, as well as instructions to operate the S800 prior to and during an experiment. | ||
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+ | ===== Introduction ===== | ||
+ | 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/ | ||
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+ | ==== Analysis Line ==== | ||
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+ | 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. | ||
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+ | [[s800]] | ||
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+ | ==== Spectrograph ==== | ||
+ | The spectrograph consist of two quadrupoles, | ||
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+ | ^ Momentum Resolution (p/ | ||
+ | ^ Momentum Acceptance | ||
+ | ^ Angle Resolution | ||
+ | ^ Solid Angle Acceptance | ||
+ | ^ Momentum Dispersion (x/ | ||
+ | ^ Angle Dispersion (y/b) | 0.9 mm/ | ||
+ | ^ Magnification(x/ | ||
+ | ^ Focal Plane Size (x × y) | 55 cm ×15 cm | | ||
+ | ^ Maximum Rigidity | ||
+ | ^ Detector Position Resolution (x)| 0.3 mm | | ||
+ | ^ Detector Position Resolution (y)| 0.3 mm | | ||
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+ | ==== S800 Stations ==== | ||
+ | The S800 includes several detector stations: | ||
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+ | The intermediate image box (see (picture) Fig. xxx) is equipped with two Tracking Parallel Plate Avalanche Counters (TPPACs) . | ||
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+ | The standard configuration of the S800 used to employ a scattering chamber (see (picture) Fig. xxx) that contains a ladder for holding the targets. This ladder is mounted on a drive that allowed for continuous rotation as well as vertical translation for the fine adjustment of the target position and thickness. This scattering chamber also contains two fixed-position drives movable by 1" increments located in front of the target, as well as a table that can be inserted from the chamber top covering the whole area of the chamber. The inside dimensions of this chamber are 1 m along the beam axis by 1 m transversally. It can be configured for a fixed set of spectrograph angles using a set of welded front flanges for 0°, 5°, 8°, 10°, and 18°. | ||
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+ | A much larger scattering chamber (see (picture) Fig. xxx) is available to accommodate for bigger detector systems such as HiRA. This chamber retains a target mechanism similar to the one described above (vertical translation + rotation), but with the additional possibility of shifting the target position along the beam axis. This feature is necessary for experiments that require more space " | ||
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+ | As mentioned before, the scattering chamber is equipped with drives that can accommodate any kind of tracking detector (with a small adaption). Standard PPAC detectors (limited to 1 kHz count rate) can be installed at those locations. However, one should keep in mind that reaction products stemming from interaction of the beam with the detectors pose a possible contamination of the beam and require " | ||
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+ | Some detection systems do not require a scattering chamber. In this case, the chamber will be removed and the target is slid into a pipe surrounded by the detector array. SeGA, CAESAR, GRETINA, PLUNGER, LENDA have standard frames and setups to be used with the S800. Other detector arrays would require the design and fabrication of new hardware. In this configuration a target change presently requires venting the target section and dismounting part of the hardware to access the inside of the beam pipe. This operation typically takes about 30-45 minutes. | ||
+ | The S800 focal plane box (see (picture) Fig. xxx) is equipped with various detectors including two position sensitive Cathode Readout Drift Chambers (CRDCs) for tracking the trajectories of the particles, a ion chamber for the measurement of energy loss, a timing scintillator | ||
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+ | ==== Magnets ==== | ||
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+ | === Spectrograph Dipoles === | ||
+ | Each S800 dipole [3] weights 70 Tons and has a 15 cm gap. The bending radii and angle are 2.8 m and 75°, respectively. The magnet has five main pieces: two top slabs, the inner and outer side yokes, and the pole tip assembly. The maximum current supplied to the coil is 450 A, translating into a 1.6 T maximum central magnetic field, and a maximum magnetic rigidity of about 4 Tm. Trim coils are installed on the inner and outer radii of the dipoles to achieve a uniform field near the edges of the magnet. The operating current of the trim coils is 43.75% the value of the magnets. A liquid helium feed circuit brings liquid helium through a heat exchanger at the top of the magnet | ||
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+ | === Spectrograph Quadrupole Doublet === | ||
+ | In order to maximize the acceptance of the spectrograph, | ||
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+ | === Spectrograph Sextupole === | ||
+ | The only high-order magnet included in the S800 is a sextupole coil installed around the bore tube of Q2. The purpose of this element is to correct the broadening of the beam at the focal plane due to the dominant (x|2) aberration. This defines a narrower trajectory of the beam, allowing the use of a beam blocker at the focal plane to block the unreacted beam when its magnetic rigidity is close to the tuned setting. | ||
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====== Headline ====== | ====== Headline ====== |