Physics307L F08:People/Mondragon/Notebook/071024
note: power for LED is from - to +, not gnd to +
Verified the LED works power supply is Harrison Labroratories ewruhdkjdf GSA prop. 00029
PMT Voltage at -1900 V
We set the voltage to the pulser so we get 10.03+/- 0.02 khz
THE tAC SEEMS TO WORK, ADDING A DELAY TO THE SIGNAL SEEMS TO MAKE THE TAC OUTPUT A BIGGER SIGNAL the delay that the delay box puts into the signals is unnoticable on anb o-scope
Speed Of Light
(week 1)
NOTES:
Set up as described in the lab procedure. Tomas and I verified that the PMT was operating (green light seen).
Set Up
LED pulser voltage: 153.9
With the O Scope, we verified the start and stop TAC signals. We also measured a pulse frequency of 8.4kHHz. We adjusted the PMT voltage to get the pulse frequency of exactly 10.01kHz (+/- .02kHz)
System Calibration: We will use the delay box got measure the insertion loss. The TAC seems to be working and we confirmed the delay box works by using the MCA. The histogram shifts when a delay switch is turned (YES!). After configuring the MCA we started taking cal data
TAC Settings/High Voltage for PMT
Range = 100
Multiplier = 1
SCA Window = 811
SCA Lower Level = 48
Start and Stop = Anti
Output = Out
Voltage = 1500 + 497.1
Calibration Data (needed or "Time Walk")
| Time | Centoid | FWHM |
|---|---|---|
| 4ns | 24.133 | 12.161 |
| 8ns | 67.79 | 14.938 |
| 12ns | 108.2 | 13.329 |
| 16ns | 153.7 | 14.874 |
| 20ns | 192.6 | 14.841 |
| 24ns | 236.4 | 17.610 |
| 28ns | 276.5 | 15.903 |
| 32ns | 323.0 | 23.378 |
| 36ns | 360.3 | 18.118 |
| 40ns | 404 | 21.038 |
| 44ns | 444.4 | 19.412 |
| 48ns | 490.5 | 25.0955 |
| 52ns | 530.1 | 21.614 |
| 56ns | 573.3 | 25.081 |
The curves we were seeing from the MCA looked Poissonish.
Calculations
important!!! FWHM is not the error . It is related, however,
[math]\displaystyle{ \mathrm{FWHM} = 2 \sqrt{2 \ln (2) } \; \sigma \approx 2.355 \; \sigma. }[/math]
| Time | Centoid | FWHM | Centroid error |
|---|---|---|---|
| 4ns | 24.133 | 12.161 | 28.637 |
| 8ns | 67.79 | 14.938 | 35.18 |
| 12ns | 108.2 | 13.329 | 31.4 |
| 16ns | 153.7 | 14.874 | 35.0 |
| 20ns | 192.6 | 14.841 | 34.9 |
| 24ns | 236.4 | 17.610 | 41.5 |
| 28ns | 276.5 | 15.903 | 37.4 |
| 32ns | 323.0 | 23.378 | 55.0 |
| 36ns | 360.3 | 18.118 | 42.7 |
| 40ns | 404 | 21.038 | 49.5 |
| 44ns | 444.4 | 19.412 | 45.7 |
| 48ns | 490.5 | 25.095 | 59.1 |
| 52ns | 530.1 | 21.614 | 50.9 |
| 56ns | 573.3 | 25.081 | 59.1 |
Linefit/ Channel number to time conversion
[math]\displaystyle{ channel\,number=(10.53 \pm 0.69 \tfrac{channels}{s})(time\,delay) -(17.29 \pm 19.54)channels }[/math]
[math]\displaystyle{ time \, delay=(0.09495 \pm 0.00626 \tfrac{s}{channel})(channel\,number) -(1.641 \pm 1.861)s }[/math]
