Speed of Light: 9/15/2008
SJK 12:37, 4 October 2008 (EDT)
12:37, 4 October 2008 (EDT)
Very good notes on the equipment. I do know you were thinking about the experiment for a long time, and not actually taking a lot of data the first day...nevertheless, I'd urge you to take more notes along the way. Even if you're not sure what you're doing, stop every 15 minutes or so to make notes ("trying this...looking at this...etc.").
- For this experiment, I am using a Bertan Associates Model 315 DC power supply, set to -1990 Volts and a Photo Multiplier Tube (PMT). The light signal is being initiated by a green LED at frequencies ~10kHz, and is powered by a Harrison Laboratories model 6207A DC power supply, set to 175 Volts. For analyzing signals I have BAC cables running from the LED into the "Start" port on an Ortec 567 Time-Amplitude Converter/Single Channel Analyzer (TAC/SCA), along with from the Anode of the PMT into a Canberra Nanosecond Delay Box and to the "Stop" port on the TAC, both of which are housed in a Harshaw NQ-75 Miniature NIM Bin. For viewing the signals, I have a BAC cable running from thr TAC output into Channel 1 of a Tektronix TDS1002 Two Channel Digital Storage Oscilloscope, and the second BAC cable from the anode of the PMT into Channel 2.
- Pictures of the setup can be found here.
- NOTE The Photo Multiplier Tube cannot be exposed to ambient light while connected to the high voltage supply.
- We decided to bypass the use of a multi-channel analyzer using an oscilloscope instead to determine the time delay and calibrate the apparatus.
- Bypassing the TAC altogether and looking directly at the signals from the PMT and LED emitter allowed for the ability to see the time differential down the tube and to see the delay settings changed on the display box.
- Viewing the data through the TAC showed a high negative peak from the anode when the photocathode is struck by pulses from the LED.