Difference between revisions of "HV and Threshold calibration"
From Hall A Wiki
| Line 4: | Line 4: | ||
* calibrate all neutron bars to equal gains. | * calibrate all neutron bars to equal gains. | ||
| − | * set threshold voltage as low as posibble (50 mV), to reduce current on PMT's. | + | * set threshold voltage as low as posibble (50 mV = channel 300), 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. | ||
| Line 30: | Line 30: | ||
* 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, so these events will be at channel=2000 | + | 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=2000 |
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
Revision as of 08:41, 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 = channel 300), 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 cofficients, so these events will be at channel=2000
