Difference between revisions of "Broadband Tagger Hodoscope"

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(Hodoscope Construction)
 
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[[Image:tagger-fixed-array-front.jpg|280px|]]
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[[Image:TAGH-backside.jpg|900px|]]
  
(Note: the figure will be updated shortly (10/08)).
 
  
The coarse fixed-array hodoscope consists of 190 scintillators distributed over a length of 10 m on the focal plane of the two-magnet system.  
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The coarse broadband (fixed-array) hodoscope consists of 218 scintillators distributed over a length of 9.25 m mounted in counter rows at a distance of 8 cm (and 13 cm) behind the focal plane of the tagger magnet.  
The high-resolution device ([[Tagger_Microscope]]) will be positioned behind the fixed array.
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The high-resolution device ([[Tagger Microscope]]) will be positioned on the focal plane.
The scintillator array detects scattered electrons in the energy range of 0.3 to 9 GeV (for a 12 GeV electron beam), i.e. it will tag photons between 3.0 GeV and 11.7 GeV.
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The scintillator array detects scattered electrons in the energy range of 0.22 to 9.0 GeV (for a 12 GeV electron beam), i.e. it will tag photons between 3.0 GeV and 11.78 GeV.
  
The device will primarily be used to  
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The device will primarily be used to
* measure the energy spectrum during the calibration of the radiator crystals,  
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* measure the energy spectrum during the calibration of the radiator crystals,
* monitor the photon energy spectrum during data taking with coherent bremsstrahlung photons, and
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* monitor the stability of the incoherent photon spectrum during data taking,  
* the energy range of electrons between 0.3 to 3 GeV will be additionally used during data taking to detect any electrons whose associated bremsstrahlung photons have energies above 9.0 GeV in order to account for possible beam photon candidates with higher energies than covered by the variable microscope.
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* tag photons above the coherent peak in order to account for possible beam photon candidates with higher energies than covered by the variable microscope, and
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* act as tagging hodoscope for any experiments (other than GlueX) that require a wide tagged energy coverage or require tagging near the end point.
  
In order to allow for operating the hodoscope at the projected high rates, only the high-photon-energy range (<i>E<sub>&gamma;</sub></i>&gt;9.0 GeV) will be fully covered with detectors; the remaining range will be sampled by 50%.
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<table width="100%">
 
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<tr><td width="50%">
All counters will be mounted at angles such that they face normal to the path of the scattered electrons.  
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In order to allow for operating the hodoscope at the projected high rates, only the high-photon-energy range (<i>E<sub>&gamma;</sub></i>&gt;9.1 GeV) will be fully covered with detectors; the remaining range will be sampled.  
The construction of the hodoscope allows for later addition of counters to fully cover the whole energy range by filling the gaps between the 50% sampling scintillators and filling the second row of PMTs.
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The width of the counters varies between 3 mm and 21 mm to roughly equalize the count rate, i.e. keep the rate at 2-4 MHz per counter at nominal running conditions.
In order to enable the positioning of the scintillators close to the thin focal-plane window of the vacuum chamber, the PMTs are positioned below the flange of the vacuum window at a distance 30cm below the scattering plane. A second row of PMTs is necessary to allow the full tagging coverage above <i>E<sub>&gamma;</sub></i>&gt;9.0 GeV.
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<br>
Straight lightguides connect the tagger scintillators to the PMTs.
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All counters are mounted at counter-specific angles such that they face normal to the path of the scattered electrons.
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The construction of the hodoscope allows for later addition of counters to fully cover the energy range above the coherent peak for other microscope positions by filling the gaps between sampling scintillators.
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The mounting frame of the hodoscope is suspended from the Tagger-Hall ceiling to provide full flexibility of microscope positioning. The thin scintillators are slotted into cylindrical light guides which are fastened to mounting plates by a collar.<br>
  
 
See [[Specification for broad-band tagging hodoscope]] for details.
 
See [[Specification for broad-band tagging hodoscope]] for details.
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<br>
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[[Position and Energy Boundaries for all installed Counters]]
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</td>
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<td>
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&nbsp; &nbsp; &nbsp; [[Image:tagger-fixed-array-endpoint.jpg|400px|]]
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</td>
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</tr>
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</table>
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[[Some specifications on PMTs]]
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[[Electron trajectories]]
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[https://userweb.jlab.org/~sober/HallD Dan Sober's webpage: mapping results and transport calculations]
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==  Hodoscope Construction ==
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[[Hodoscope Fabrication Readiness Review ]]  (June 11, 2013)
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[[Follow up on the Hodoscope Fabrication Readiness Review ]]  (September 30, 2013)
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<table>
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<tr>
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<td> [[TAGH_LG_inspection|Light guide & scintillator inspection]]  &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </td> <td> ([[Media:TAGH_counter_assembly.xlsx | Excel spreadsheet: Counter assembly]]) </td>
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</tr>
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<tr>
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<td> [[TAGH_PMT_testing|PMT & pre-amp testing]] </td> <td> ([[Media:TAGH_pmt_tests.xlsx | Excel spreadsheet: PMT test]]) </td>
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</tr>
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<tr>
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<td> [[TAG_counter_assembly|Counter assembly (gluing, wrapping)]] </td> <td> ([[Media:TAGH_counter_assembly.xlsx | Excel spreadsheet: Counter assembly]]) </td>
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</tr>
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<tr>
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<td> [[TAGH_calibration|Hodoscope calibration]] </td>
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</tr>
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</table>
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[https://halldweb.jlab.org/wiki-private/index.php/Tagger_Hodoscope_Spare_Components Tagger Hodoscope Spare Components]
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[[Repairs made to TAGH scintillator counters over the summer of 2019]]
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[https://logbooks.jlab.org/entry/3900608 Counters repaired before the PrimEx-eta run in 2021]

Latest revision as of 20:36, 6 September 2021

TAGH-backside.jpg


The coarse broadband (fixed-array) hodoscope consists of 218 scintillators distributed over a length of 9.25 m mounted in counter rows at a distance of 8 cm (and 13 cm) behind the focal plane of the tagger magnet. The high-resolution device (Tagger Microscope) will be positioned on the focal plane. The scintillator array detects scattered electrons in the energy range of 0.22 to 9.0 GeV (for a 12 GeV electron beam), i.e. it will tag photons between 3.0 GeV and 11.78 GeV.

The device will primarily be used to

  • measure the energy spectrum during the calibration of the radiator crystals,
  • monitor the stability of the incoherent photon spectrum during data taking,
  • tag photons above the coherent peak in order to account for possible beam photon candidates with higher energies than covered by the variable microscope, and
  • act as tagging hodoscope for any experiments (other than GlueX) that require a wide tagged energy coverage or require tagging near the end point.

In order to allow for operating the hodoscope at the projected high rates, only the high-photon-energy range (Eγ>9.1 GeV) will be fully covered with detectors; the remaining range will be sampled. The width of the counters varies between 3 mm and 21 mm to roughly equalize the count rate, i.e. keep the rate at 2-4 MHz per counter at nominal running conditions.

All counters are mounted at counter-specific angles such that they face normal to the path of the scattered electrons. The construction of the hodoscope allows for later addition of counters to fully cover the energy range above the coherent peak for other microscope positions by filling the gaps between sampling scintillators. The mounting frame of the hodoscope is suspended from the Tagger-Hall ceiling to provide full flexibility of microscope positioning. The thin scintillators are slotted into cylindrical light guides which are fastened to mounting plates by a collar.

See Specification for broad-band tagging hodoscope for details.
Position and Energy Boundaries for all installed Counters

      Tagger-fixed-array-endpoint.jpg

Some specifications on PMTs

Electron trajectories

Dan Sober's webpage: mapping results and transport calculations

Hodoscope Construction

Hodoscope Fabrication Readiness Review (June 11, 2013)

Follow up on the Hodoscope Fabrication Readiness Review (September 30, 2013)

Light guide & scintillator inspection           ( Excel spreadsheet: Counter assembly)
PMT & pre-amp testing ( Excel spreadsheet: PMT test)
Counter assembly (gluing, wrapping) ( Excel spreadsheet: Counter assembly)
Hodoscope calibration

Tagger Hodoscope Spare Components

Repairs made to TAGH scintillator counters over the summer of 2019

Counters repaired before the PrimEx-eta run in 2021