User:Chad A McCoy/Notebook/Jr. Lab/2008/09/22

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Speed of Light (Day 2): 9/22/2008

SJK 12:40, 4 October 2008 (EDT)
12:40, 4 October 2008 (EDT)
This is a good idea for calibration. However, I would think that MUCH bigger delays for calibration would work better. To minimize the effect of noise. Also, we did find the manual for the TAC, so you could look up the expected conversion factor...then decide whether to assume the machine is more accurate than your calibration or not.
  • Calibration of TAC:
TAC Amplitudes for known Delay Times (Volts)
Trial # Delay = 0 Delay = .5ns Delay = 1ns Delay = 2ns
1 1.84 2.24 2.36 2.20
2 .960 1.44 1.84 2.24
3 2.08 1.52 1.88 1.48
4 1.28 1.36 1.68 2.04
5 1.72 1.92 1.94 1.76
6 1.60 2.08 1.64 2.04
7 1.36 1.76 1.32 1.76
8 1.12 1.56 1.92 1.88
9 1.64 2.00 1.44 1.52
10 1.16 1.72 1.84 1.80
11 1.12 1.56 2.20 2.00
12 1.48 1.72 1.56 1.92
13 1.64 1.60 1.88 1.64
14 1.28 1.44 1.52 1.76
15 1.48 1.36 2.08 1.96
16 .960 1.72 2.16 1.88
17 .800 1.96 1.64 1.84
18 1.24 1.48 1.92 1.72
19 1.40 1.76 1.76 2.08
20 1.64 1.44 1.60 2.16
Avg: 1.379 1.682 1.809 1.884
  • Doing the calibration of the TAC using known delays allowed for a visible appearance that the minimum measured amplitude increased with each successive delay from 0ns to 2ns, showing that when taking an average, the delay time will allow for a relatively accurate measurement with the distribution due to scattering of light in the tube, and the time walk because of the differing peak voltage transmitted to the anode depending on the time walk and discriminator level in the TAC.
SJK 12:44, 4 October 2008 (EDT)
12:44, 4 October 2008 (EDT)
you need MUCH more information in your raw data notebook here about your method! I do see a lot of measurements (20!, a heroic number perhaps) for each distance...but it's not clear whether you did this all at once, or whether you moved the ruler between each measurement? All sorts of other details...what is your reference voltage for the PMT anode signal? How much are you averaging? What other techniques? It would be quite impossible for anyone to attempt to replicate your experiments by reading this!
  • Calculating the travel time of light relative to initial LED position inside tube.
TAC Amplitudes for Different distances relative to Photocathode (Volts)
Trial # Δd = 0.00m Δd = 0.25m Δd = 0.50m Δd = 0.75m Δd = 1.00m
1 .860 1.06 1.32 1.60 1.48
2 1.18 1.02 1.30 1.32 1.64
3 .940 1.12 1.00 1.02 1.60
4 1.08 1.60 1.68 1.52 1.28
5 .940 .780 1.32 1.12 1.52
6 1.04 1.34 1.22 1.30 1.92
7 .840 1.28 1.40 1.60 1.32
8 .820 1.14 1.56 1.48 1.46
9 .900 .920 1.44 1.56 1.24
10 1.10 1.08 1.40 1.30 2.06
11 1.36 1.42 1.48 1.36 1.28
12 .880 1.28 1.10 1.48 1.56
13 1.28 1.06 1.10 1.22 1.74
14 .920 1.32 1.60 1.50 1.38
15 .840 1.58 1.34 1.58 1.64
16 1.36 1.08 1.46 1.56 1.82
17 .760 .840 1.26 1.38 1.38
18 1.00 .860 1.40 1.66 1.34
19 1.22 1.14 1.50 1.62 1.58
20 1.24 1.34 1.22 .980 1.38
Avg: 1.028 1.163 1.355 1.408 1.529
  • All values calculated with measure function in Oscilloscope with margin of error +/- .02V