Difference between revisions of "Specification for broad-band tagging hodoscope"
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| − | + | [[Image:TAGH-from-magnet-all.jpg|900px|]] | |
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| + | In its standard configuration the fixed-array hodoscope consists of 218 scintillators distributed over 9.1 m behind the focal-plane of the tagger spectrometer. Standard configuration refers to a coherent-peak setting at 9.0 GeV, i.e. the microscope covers the energy range 8.1<E<sub>γ</sub><9.1 GeV. | ||
Tagging range (for a 12 GeV electron beam): | Tagging range (for a 12 GeV electron beam): | ||
| − | * <b>Photons between 3.0 GeV and | + | * <b>Photons between 3.0 GeV and 8.2 GeV</b>: detector positions correspond to 60 MeV steps in E<sub>γ</sub> with <b>30-50% sampling</b>. The counter widths are chosen such that the typical rate per counter is limited to 3-4 MHz at 10<sup>8</sup> γ/sec on target; |
| − | * <b>Photons between 9. | + | * <b>Photons between 9.2 GeV and 11.78 GeV</b>: scintillators cover the full energy range, counter widths were calculated such that the typical rate per counter is limited to 1-4 MHz at 10<sup>8</sup> γ/sec on target. |
| − | + | ||
All counters will be mounted at angles such that they face normal to the path of the scattered electrons. | All counters will be mounted at angles such that they face normal to the path of the scattered electrons. | ||
'''Scintillators''' | '''Scintillators''' | ||
| − | + | <table width="100%"> | |
| − | + | <tr><td width="70%"> | |
| − | + | {| | |
| − | + | | Material | |
| + | | EJ-228 | ||
| + | |- | ||
| + | | Thickness | ||
| + | | 6 mm | ||
| + | |- | ||
| + | | Height | ||
| + | | 40 mm (slotted into the light guides, slot depth: 3mm) | ||
| + | |} | ||
| + | |||
| + | {| border="1" style="text-align:center;" cellpadding="10" cellspacing="0" | ||
| + | |- style="font-style:bold; color:blue;" | ||
| + | |!scope="row" | Counter # || width <br>[mm] || distance from <br>focal plane || E<sub>γ</sub> <br>[GeV] || ΔE <br>[MeV] | ||
| + | |- | ||
| + | | 1 – 22 || 21.0 || 8 / 18 cm || 11.43 – 11.78 || 10.2 – 23.7 | ||
| + | |- | ||
| + | | 23 – 40 || 16.0 || 8 / 18 cm || 11.01 – 11.43 || 18.4 – 29.5 | ||
| + | |- | ||
| + | | 41 – 64 || 10.0 || 8 / 18 cm || 10.46 – 11.01 || 18.7 – 26.8 | ||
| + | |- | ||
| + | | 65 – 81 || 8.0 || 8 / 18 cm || 10.05 – 10.46 || 21.7 – 26.0 | ||
| + | |- | ||
| + | | 82 – 139 || 5.0 || 8 / 13 / 18 cm || 9.20 – 10.05 || 16.4 – 22.2 | ||
| + | |- | ||
| + | | 140 – 195 || 4.0 || 8 / 13 / 18 cm || 7.07 – 8.13 || 16.6 – 17.2 | ||
| + | |- | ||
| + | | 196 – 274 || 3.0 || 8 cm || 3.05 – 7.03 || 13.7 – 20.3 | ||
| + | |} | ||
| + | |||
| + | </td> | ||
| + | <td> [[Image:TAGH-counter-cut.jpg|100px|]] | ||
| + | </td> | ||
| + | </tr> | ||
| + | </table> | ||
| + | |||
| + | '''Light guides''' | ||
| + | |||
| + | All light guides (UVT PMMA) have cylindrical shape of 120 mm length and 7/8" = 22.2mm diameter to cover the size of the photocathode. A collar at 60mm height with 2 bolts along the slot line ensure proper positioning of the counters: threaded holes for the bolts in the mounting plates are correspondingly oriented. | ||
| + | |||
'''Photomultipliers''' | '''Photomultipliers''' | ||
| − | + | Hamamatsu R9800: 1" tube with 8 dynodes, rise time 1.0 ns, transit time 11 ns, 27% quantum eff., max. anode current 100 μA.<br> | |
| + | magnetic shields: μ-metal cylinders.<br> | ||
| + | HV dividers and 2-stage preamps (amp. factor 8.5x) developed at Jefferson Lab, they allow for limiting the anode current to 15-20 μA at 4 MHz rate.<br> | ||
| + | Operating voltage: U=900 V resulting in a gain of 5×10<sup>5</sup>, anode current contributes to less than 5% of the active base current. | ||
'''Readout electronics''' | '''Readout electronics''' | ||
| − | + | The new preamp boards have 2-channel output for fADC250 and F1TDC. | |
| + | |||
| + | |||
| − | + | ==Fixed array counter positions== | |
| − | + | Table moved to [[Position and Energy Boundaries for all installed Counters]] | |
| − | + | ||
| − | + | ||
Latest revision as of 21:00, 25 January 2017
In its standard configuration the fixed-array hodoscope consists of 218 scintillators distributed over 9.1 m behind the focal-plane of the tagger spectrometer. Standard configuration refers to a coherent-peak setting at 9.0 GeV, i.e. the microscope covers the energy range 8.1<Eγ<9.1 GeV.
Tagging range (for a 12 GeV electron beam):
- Photons between 3.0 GeV and 8.2 GeV: detector positions correspond to 60 MeV steps in Eγ with 30-50% sampling. The counter widths are chosen such that the typical rate per counter is limited to 3-4 MHz at 108 γ/sec on target;
- Photons between 9.2 GeV and 11.78 GeV: scintillators cover the full energy range, counter widths were calculated such that the typical rate per counter is limited to 1-4 MHz at 108 γ/sec on target.
All counters will be mounted at angles such that they face normal to the path of the scattered electrons.
Scintillators
|
|
Light guides
All light guides (UVT PMMA) have cylindrical shape of 120 mm length and 7/8" = 22.2mm diameter to cover the size of the photocathode. A collar at 60mm height with 2 bolts along the slot line ensure proper positioning of the counters: threaded holes for the bolts in the mounting plates are correspondingly oriented.
Photomultipliers
Hamamatsu R9800: 1" tube with 8 dynodes, rise time 1.0 ns, transit time 11 ns, 27% quantum eff., max. anode current 100 μA.
magnetic shields: μ-metal cylinders.
HV dividers and 2-stage preamps (amp. factor 8.5x) developed at Jefferson Lab, they allow for limiting the anode current to 15-20 μA at 4 MHz rate.
Operating voltage: U=900 V resulting in a gain of 5×105, anode current contributes to less than 5% of the active base current.
Readout electronics The new preamp boards have 2-channel output for fADC250 and F1TDC.
Fixed array counter positions
Table moved to Position and Energy Boundaries for all installed Counters
