User:Brian P. Josey/Notebook/Junior Lab/2010/09/13: Difference between revisions

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==Speed of Light Lab, Day 1==
==Speed of Light==
For this experiment, my partner [[User:Kirstin Grace Harriger|Kirstin]] and I measured the speed of light. The speed of light is one of the most fundamental physical constants, and the fastest speed at which anything can travel. To do this, we shot light from an light emitting diode (LED) down a long cardboard tube to a photomultiplier tube (PMT). This PMT then measures the incoming light and converts it into a signal. We then measured the differences in the signals on the oscilloscope to find the time that it takes for light to travel a given length down the tube. From the measured time for a given distance, we were able to calculate the speed through linear regression, as explained in more detail in the procedure and results sections below. From our data, we were able to successfully measure the speed of light as 31.0 ± 0.5 cm/ns. The accepted value for the speed of light is 29.98 cm/ns in a vacuum.
 
 
===Equipment===
In addition to the cardboard tube, LED light, and PMT, we had several pieces of equipment that we used in this experiment. They were:
 
* Tektronix TDS 1012 Oscilloscope
* Bertan Model 215 High voltage power supply
* Ortec TAC/SCA Module (Model 567)
* Harrison Laboratories Power Supply (Model 6207A, 160V, 0.2A)
* Canberra Delay Module (Model 2058)
 
There are a couple of safety concerns with the experiment. The first is that both of the power supplies generate a significant voltage and current, so shock is a major concern, and once the power supplies were turned on and connected, touching any frayed wires, or the back and underside of the chassis could result in shock. There was also a risk of damaging the PMT by exposing it to too much light; once the PMT was on, it could not be removed from the tube or the ambient light would overload it and ruin it. Even removing the LED from the tube could result in too much light reaching the PMT as is to be avoided.
 
===Set Up===
The PMT was already placed in the cardboard tube at one end, while the LED was attached to a series of meter sticks taped together at the other end. These meter sticks are used to measure how far the LED is from the PMT at any given time. With the PMT and LED already in place, we began to connect all of the other components into place. To do this we inserted the Betran power supply, Ortec TAC and Canberra Delay Module into the chassis and secured them with thumbscrews. Then by using BNC cables, we connected the other components. The ''A'' connection of the PMT was connected to the top input of the delay module, while the output of the delay module was connected to a T-splitter. One part of the splitter was connected to the channel 1 input on the oscilloscope, while the other was connected to the stop input on the TAC. We connected the start input on the TAC to the LED, and we connected the power cable of the LED to the Harrison power supply. Finally, we connected the output of TAC to channel 2 on the oscilloscope, and the "-HV" port on the PMT to the Bertan power supply completing all of the wiring.
 
We then adjusted the settings on our set up for the experiment. On the Bertan power supply, we set the polarity to negative, voltage to 2000 V and the offset to 400 V. On the delay module, we set the delay to 20 ns, and the Harrison power supply to 190 V. On the TAC, we set the range to 100 ns, the multiplier to 1, the output switch to to "Out" and the start and stop switches to "Anti".
 
 
 
 
 
 
 
I am working with Kirstin *Insert link* again today, and the lab we are doing is the speed of light. Today, we are going to get the experiment set up, and account for the "time walk" which can leave a systematic error in the experiment. Next week we'll be taking our final runs.
I am working with Kirstin *Insert link* again today, and the lab we are doing is the speed of light. Today, we are going to get the experiment set up, and account for the "time walk" which can leave a systematic error in the experiment. Next week we'll be taking our final runs.


Revision as of 10:44, 28 September 2010

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Speed of Light

For this experiment, my partner Kirstin and I measured the speed of light. The speed of light is one of the most fundamental physical constants, and the fastest speed at which anything can travel. To do this, we shot light from an light emitting diode (LED) down a long cardboard tube to a photomultiplier tube (PMT). This PMT then measures the incoming light and converts it into a signal. We then measured the differences in the signals on the oscilloscope to find the time that it takes for light to travel a given length down the tube. From the measured time for a given distance, we were able to calculate the speed through linear regression, as explained in more detail in the procedure and results sections below. From our data, we were able to successfully measure the speed of light as 31.0 ± 0.5 cm/ns. The accepted value for the speed of light is 29.98 cm/ns in a vacuum.


Equipment

In addition to the cardboard tube, LED light, and PMT, we had several pieces of equipment that we used in this experiment. They were:

  • Tektronix TDS 1012 Oscilloscope
  • Bertan Model 215 High voltage power supply
  • Ortec TAC/SCA Module (Model 567)
  • Harrison Laboratories Power Supply (Model 6207A, 160V, 0.2A)
  • Canberra Delay Module (Model 2058)

There are a couple of safety concerns with the experiment. The first is that both of the power supplies generate a significant voltage and current, so shock is a major concern, and once the power supplies were turned on and connected, touching any frayed wires, or the back and underside of the chassis could result in shock. There was also a risk of damaging the PMT by exposing it to too much light; once the PMT was on, it could not be removed from the tube or the ambient light would overload it and ruin it. Even removing the LED from the tube could result in too much light reaching the PMT as is to be avoided.

Set Up

The PMT was already placed in the cardboard tube at one end, while the LED was attached to a series of meter sticks taped together at the other end. These meter sticks are used to measure how far the LED is from the PMT at any given time. With the PMT and LED already in place, we began to connect all of the other components into place. To do this we inserted the Betran power supply, Ortec TAC and Canberra Delay Module into the chassis and secured them with thumbscrews. Then by using BNC cables, we connected the other components. The A connection of the PMT was connected to the top input of the delay module, while the output of the delay module was connected to a T-splitter. One part of the splitter was connected to the channel 1 input on the oscilloscope, while the other was connected to the stop input on the TAC. We connected the start input on the TAC to the LED, and we connected the power cable of the LED to the Harrison power supply. Finally, we connected the output of TAC to channel 2 on the oscilloscope, and the "-HV" port on the PMT to the Bertan power supply completing all of the wiring.

We then adjusted the settings on our set up for the experiment. On the Bertan power supply, we set the polarity to negative, voltage to 2000 V and the offset to 400 V. On the delay module, we set the delay to 20 ns, and the Harrison power supply to 190 V. On the TAC, we set the range to 100 ns, the multiplier to 1, the output switch to to "Out" and the start and stop switches to "Anti".




I am working with Kirstin *Insert link* again today, and the lab we are doing is the speed of light. Today, we are going to get the experiment set up, and account for the "time walk" which can leave a systematic error in the experiment. Next week we'll be taking our final runs.

Equipment

  • Tektronix TDS 1012 Oscilloscope
  • Bertan Model 215 High voltage power supply
  • Ortec TAC/SCA Module (Model 567)
  • Harrison Laboratories Power Supply (Model 6207A, 160V, 0.2A)
  • Canberra Delay Module (Model 2058)

Set Up

We followed along with Alexandra's notebook, here [[1]] to connect the cables, following her procedure we:

  • The "A" connection of the photomultiplier tube (PMT) to the top input of the delay module.
  • The output of the delay module to a BNC T-splitter
   * One side connected to the channel 1 input on the oscilloscope
   * The other to the "Stop" input of the Time-Amplitude Converter (TAC).
  • The output of the TAC to the channel 2 input of the oscilloscope.
  • The "-HV" connection of the photomultiplier tube (PMT) to the "-HQ" connection of the Bertan Power Supply (PSU).
  • The "Start" input of the TAC to the cable attached to the LED.


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