User:Michael R Phillips/Notebook/Physics 307L/2008/10/01: Difference between revisions

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These are all measured with our initial (farthest) data at x=0, slowly moving the LED closer to the PMT. They are the voltages of our output square wave (aka our TAC).
These are all measured with our initial (farthest) data at x=0, slowly moving the LED closer to the PMT. They are the voltages of our output square wave (aka our TAC).
* '''Reference Voltage = -432mV'''
* '''Reference Voltage = -432mV'''
* At x=0: 5.2 +/- .2 V
* At x=0: 5.2±0.2 V
* At x=5: 5.0 +/- .4 V
* At x=5: 5.0±0.4 V
* At x=15: 5.8 +/- .4 V
* At x=15: 5.8±0.4 V
* At x=20: 5.4 +/- .4 V
* At x=20: 5.4±0.4 V
* At x=30: 3.6 +/- .4 V
* At x=30: 3.6±0.4 V
* At x=40: 4.0 +/- .4 V
* At x=40: 4.0±0.4 V
* At x=50: 5.0 +/- .4 V
* At x=50: 5.0±0.4 V
* At x=60: 4.6 +/- .2 V
* At x=60: 4.6±0.2 V
* At x=70: 4.0 +/- .2 V
* At x=70: 4.0±0.2 V
* At x=80: 6.2 +/- .2 V
* At x=80: 6.2±0.2 V


===Day 2===
===Day 2===
Line 108: Line 108:
  30    4.8
  30    4.8


Now we start taking actual data. Following are the data points we took. The 'x' values are how much we moved the light source closer to the photomultiplier tube, and the 'V' values correspond to the output from the TAC. This is all taken without any rotation of the photomultiplier tube (thus no rotation of the polarizer).
We decided this was not the way for us to go about the experiment, so we changed our tactics:
 
Now we start taking actual (good) data. Following are the data points we took. The 'x' values are how much we moved the light source closer to the photomultiplier tube, and the 'V' values correspond to the output from the TAC. This is all taken without any rotation of the photomultiplier tube (thus no rotation of the polarizer) and using the measure function of our oscilloscope.


  '''x(cm)'''    '''V(V)'''
  '''x(cm)'''    '''V(V)'''

Revision as of 14:52, 8 October 2008

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Set up & preliminary data

After taking our safety quiz, we started fiddling around with all our equipment, including our oscilloscope (Tektronix TDS 1002), photomultiplier tube (PMT) and the associated power supply (Bertan model 315) and NSEC Delay (Canberra model 2058), our LED light with a periodic voltage supplied to it by a 200V power supply (Harrison model 6706A), and the Time-to-Amplitude Converter (aka TAC, EG&G Ortec model 567).

We fired everything up, using these values:

  • Voltage to PMT: 1820V
  • Voltage to LED: 190V
  • TAC multiplier: 1
  • TAC range: 50
  • Delay: 0

We initially collected a lot of terrible data at first, using some error voltage created by the output of our TAC. Following is some actual preliminary Data (meaning on day 1 ).

These are all measured with our initial (farthest) data at x=0, slowly moving the LED closer to the PMT. They are the voltages of our output square wave (aka our TAC).

  • Reference Voltage = -432mV
  • At x=0: 5.2±0.2 V
  • At x=5: 5.0±0.4 V
  • At x=15: 5.8±0.4 V
  • At x=20: 5.4±0.4 V
  • At x=30: 3.6±0.4 V
  • At x=40: 4.0±0.4 V
  • At x=50: 5.0±0.4 V
  • At x=60: 4.6±0.2 V
  • At x=70: 4.0±0.2 V
  • At x=80: 6.2±0.2 V

Day 2

On the beginning of the second day, we set up everything as we remembered from the previous week. Within just a couple of minutes, we powered everything up and got a square wave result for us to measure. As soon as we moved the light source back for a starting position, however, we lost our square wave and had to start fiddling with the O-scope and other equipent to recover it. After some time, we managed to regain a decent square wave by rotating our photomultiplier tube to get a maximum readable voltage. We even managed to measure the threshold of the TAC to be 400mV (this is the voltage that we do not want to allow below) with some minor assistance from Koch.

We started by setting our TAC voltage very high, at 1950V, so that we could get large outputs. This is our calibration data for a few different time delays.

Delay (ns) First Run(V) Second Run(V)
0 5.0±0.2 4.8
.5 5.0 4.9±0.1
1 5.0 5.0
2 5.2 5.2
4 5.6 5.6
6 6.0 6.0
8 6.4 6.4
10 6.8 6.8
12 7.2 7.1±0.1
14 7.6 7.6
16 8.0 8.0
18 8.4 8.4
20 8.6±0.2 8.5±0.1

We will use this data to do a linear fit. The slope should be very near 10V/50ns.

Data Acquisition

Here is the data we took initially, correcting for the amplitudes by rotating the photomultiplier tube (and polarizer). 

x(cm)  V(V)
0     4.8
10    4.8
20    4.8
30    4.8

We decided this was not the way for us to go about the experiment, so we changed our tactics:

Now we start taking actual (good) data. Following are the data points we took. The 'x' values are how much we moved the light source closer to the photomultiplier tube, and the 'V' values correspond to the output from the TAC. This is all taken without any rotation of the photomultiplier tube (thus no rotation of the polarizer) and using the measure function of our oscilloscope. 

x(cm)     V(V)
0         5.0
10        4.6
20        4.0         
30        3.7±0.1        
40        3.4
50        3.2
60        2.8
70        2.6
80        2.2
90        2.0
100       1.6
110       1.2
120       1.0
130       0.4
140       0.2
150       0.0



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