Difference between revisions of "Total Absorption Counter"
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| + | === Observed problems=== | ||
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| + | After using Hall B lead glass TAC between 2016 and 2017 the light output significantly decreased. The radiation hardness of this lead glass is highly unlikely to exceed 10^5 rad. We are not going to be able to significantly reduce the radiation dose received by TAC since we need to accumulate meaningful statistics in the pair spectrometer with reasonable this converter that does not distort the PS acceptance shape. Therefore, it is important for GlueX to have a total absorption counter made of material with radiation hardness of ~10^6 rad or better. | ||
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| + | == Options considered earlier == | ||
* lead-glass counter array: | * lead-glass counter array: | ||
Revision as of 14:35, 16 March 2017
CLAS Total absorption counter used for PrimEx
The table below summarizes the information I obtained from various sources about the TAC counter that GlueX borrowed from CLAS.
| Property (source) | Value |
|---|---|
| Material (from Mahbub) | SF-5 Lead Glass |
| Composition by weigth (Web) | 55% PbO, 38% SiO2, 5% K2O, 1% Na2O |
| Length (from Mahbub) | 40cm |
| Height (from Mahbub) | 20cm |
| Width (from Mahbub) | 20cm |
| Weight of lead-glass block | 65 kg |
| Density (Web) | 4.08 g/cm^3 |
| Radiation Length of material (Web) | ~25mm |
| Critical Energy (Web) | 15.8 MeV |
| Refractive index (Web) | 1.67270 |
| PMT (from Mahbub) | 5 inch Hamamatsu R1250 PMT |
Observed problems
After using Hall B lead glass TAC between 2016 and 2017 the light output significantly decreased. The radiation hardness of this lead glass is highly unlikely to exceed 10^5 rad. We are not going to be able to significantly reduce the radiation dose received by TAC since we need to accumulate meaningful statistics in the pair spectrometer with reasonable this converter that does not distort the PS acceptance shape. Therefore, it is important for GlueX to have a total absorption counter made of material with radiation hardness of ~10^6 rad or better.
Options considered earlier
- lead-glass counter array:
- efficiency ~100%
- to avoid radiation damage: rate < 100kHz using radiator of 10-5 X0 and ~100 pA beam
- Cerenkov counter (higher current - but probably lower efficiency)
