S800 Documentation

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-**The S800 spectrograph**+====== The NSCL 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.  
 + 
 + 
 +===== Technical Aspects of the S800 ===== 
 + 
 +  * [[Introduction]] 
 +  * [[Stations]] 
 +  * [[Magnets]] 
 +  * [[Modes of Operation]] 
 +  * [[Determination of Angles and Momentum]] 
 +  * [[Detectors]] 
 +  * [[Electronics]] 
 +  * [[Data Acquisition (DAQ)]] 
 +  * Software 
 +  * Coupled Detectors/Devices 
 +  * Types of Experiments 
 + 
 +===== Operation of the S800 ===== 
 + 
 + 
 + 
 +==== Magnets ==== 
 + 
 +=== 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  and delivers the liquid into the bottom of the coils. The helium overflowing the coils fills the dewar to provide cooling for the incoming liquid. Liquid nitrogen is supplied at the bottom of each side. A 0.25 dissipative resistor with a short decay constant is connected to a coil protection switch. In case of cryogenic failure, the switch reroutes the power supplied to the circuit into the resistor. The dipole steel has a 30° edge angle, so that particles are defocused and focused in the dispersive and non-dispersive directions, respectively. The inner and outer radii of the dipoles include trim coils to guarantee the uniformity of the field near the edge.  NMR probes are installed in the flat field region to measure the absolute field setting during operation. 
 + 
 + 
 + 
 +=== Spectrograph Quadrupole Doublet === 
 +In order to maximize the acceptance of the spectrograph, a doublet of superconducting quadrupoles is installed upstream of the two main dipoles [3]. The doublet focuses  the transmitted particles first in the non-dispersive and then in the dispersive directions. The quadrupoles are the iron-dominated type used in the NSCL beamlines, but with larger dimensions.  The pole tip of each quad has a length of 30 cm, and a radius of 12 cm for the first quad and  21 cm for the second one, i.e. almost twice and three times larger than the beamline quadrupoles, respectively.  The doublet weights 5 Tons, including the sextupole at the end of the second quad. The field gradient  of the first quadrupole is 19.7 T/m at a maximum operation current of 86 A. The field gradient of the second one is  7.5 T/m at a maximum operation current of 90 A.  Both quadrupoles have cryogenic Hall generators mounted on the pole tips to measure the  field gradient during operation.  The quadrupoles don’t have protection circuit since they can quench with no damage to the coils. 
 + 
 + 
 +=== 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 ====== 
 + 
 +====== 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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