Difference between revisions of "HV and Threshold calibration"
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* 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. | ||
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optimum was chosen at threshold 5 MeV - still need to verify this. | optimum was chosen at threshold 5 MeV - still need to verify this. | ||
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Calibrations steps - | Calibrations steps - | ||
Revision as of 08:05, 13 April 2010
Procedure for the neutron array HV and threshold calibration
Main considerations -
- calibrate all neutron bars to equal gains.
- set threshold voltage as low as posibble (50 mV), 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 - still need to verify this.
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=1500 12.5 cm bar -> E=25 MeV -> channel=1875 15.0 cm bar -> E=30 MeV -> channel=2250 25.0 cm bar -> E=50 MeV -> channel=3750
- 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, so these events will be at channel=2000
- Gain calibration cross check using the C(e,e'p) reaction, by indentifying the punch-through point of the protons.
The punch-through energy in a 10cm wide bar is 120 MeV. The TOF vs. ADC of the C(e,e'p) events should have the following shape -
