Difference between revisions of "HV and Threshold calibration"
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| Line 4: | Line 4: | ||
* calibrate all neutron bars to equal gains. | * calibrate all neutron bars to equal gains. | ||
| − | * set | + | * set gains as low as posibble, to reduce current on PMT's. |
* set threshold energy as low as possible to increase efficiency. | * set threshold energy as low as possible to increase efficiency. | ||
* set threshold energy low enough to remove minimum ionizing electrons. | * set threshold energy low enough to remove minimum ionizing electrons. | ||
| − | optimum was chosen at threshold 5 MeV - | + | optimum was chosen at threshold = 5 MeV = 300 channels - need to re-check. |
| + | this is equivalent to 1 MeV = 60 channels | ||
| + | |||
Calibrations steps - | Calibrations steps - | ||
| Line 19: | Line 21: | ||
adjust HV, so that the muon peak will be at- | adjust HV, so that the muon peak will be at- | ||
| − | 10.0 cm bar -> E=20 MeV -> channel= | + | 10.0 cm bar -> E=20 MeV -> channel=1200 |
| − | 12.5 cm bar -> E=25 MeV -> channel= | + | 12.5 cm bar -> E=25 MeV -> channel=1500 |
| − | 15.0 cm bar -> E=30 MeV -> channel= | + | 15.0 cm bar -> E=30 MeV -> channel=1800 |
| − | 25.0 cm bar -> E=50 MeV -> channel= | + | 25.0 cm bar -> E=50 MeV -> channel=3000 |
* Beam calibration using the H(e,e'p) reaction. | * Beam calibration using the H(e,e'p) reaction. | ||
| − | Use the H(e,e'p) reaction to create 1 GeV/c protons which will have energy loss of 32 MeV for a 10cm wide bar, calibrate the gain cofficients, so these events will be at channel= | + | Use the H(e,e'p) reaction to create 1 GeV/c protons which will have energy loss of 32 MeV for a 10cm wide bar, calibrate the gain cofficients, so these events will be at channel=1920 |
Revision as of 08:46, 13 April 2010
Procedure for the neutron array HV and threshold calibration
Main considerations -
- calibrate all neutron bars to equal gains.
- set gains as low as posibble, to reduce current on PMT's.
- set threshold energy as low as possible to increase efficiency.
- set threshold energy low enough to remove minimum ionizing electrons.
optimum was chosen at threshold = 5 MeV = 300 channels - need to re-check.
this is equivalent to 1 MeV = 60 channels
Calibrations steps -
- Test-area calibration using cosmic muons
Use top-buttom bar trigger, to obtain vertical minimum ionizing muons with known energy deposit.
adjust HV, so that the muon peak will be at-
10.0 cm bar -> E=20 MeV -> channel=1200
12.5 cm bar -> E=25 MeV -> channel=1500
15.0 cm bar -> E=30 MeV -> channel=1800
25.0 cm bar -> E=50 MeV -> channel=3000
- Beam calibration using the H(e,e'p) reaction.
Use the H(e,e'p) reaction to create 1 GeV/c protons which will have energy loss of 32 MeV for a 10cm wide bar, calibrate the gain cofficients, so these events will be at channel=1920
