This page is devoted to the current research I am doing pertaining to the MuLAN experiment.




June 12, 2006: For the past couple weeks I have been experimenting with our led boards as well as our photmultiplier tube in order to get a good understanding for what our signals should look like. So far I have been able to view signals for single photo-electrons. By calculating the area under the curves in the output signal produced by these single photo-electrons we are able to make a good estimate as to how many photo-electrons are present when viewing signals produced by our led system. Originally, I looked at the signals of the PMT's where I produced the TTL inputs, 5+/-, and gnd with function generators instead of the power supply through the driver board which we will actually be using. When I looked at the signals using the function generator there were two peaks that occured after the original pulse signal. Eventually after looking at several screen shots, I determined that this was a flaw induced by the setup using the function generator and not a problem inherent in our led design. I was able to make this assertion becuase when the led board was disconnected from the function generator setup the two strange peaks were still visible (although more distorted). Also, when I created the setup we will be using (power supply-->driver board-->led board), the peaks were not present.  

June 13, 2006:
These are the three screen shots of single photo-electrons that I used to get an idea of the area under the pulse, which is then used to determine how many photo-electrons are present in larger pulses.
  • pulse 1
  • pulse 2
  • pulse 3

    Here are screen shots which illustrate the double peaks following the initial pulse as mentioned above.

  • The first shot shows the peaks when the led board is connected
    function generaor with led board
  • This second shot shows the peaks when the led board is disconnected, leading to the assumption that the problem is a result of our function generator setup and not our led board.
    function generator no led board
  • Finally we view the pulse when driven by the power supply and driver board we will be using in Switzerland.
    Power supply with driver board 1
  • As you can see the two peaks after the initial pulse is non-existant in the final setup...this is good news because if it were it would produce signals on the PMT that do not occur at the same time
    function generator with led board
  • June 15, 2006: Today was spent looking at how the peak voltage of the PMT signal varied with the frequency of the input pulse. I adjusted the frequency of the pulse through a range from zero to about 45 kilohertz. After takng several data points in this region, I recorded and plotted them in excel. The voltages appear to fall off linearly as frequency is increased. Once I was able to see these results I adjusted the pots to get a larger voltage signal. I then repeated the frequency-voltage measurements recorded the results and plotted them in excel. Expectedly, the voltage decreased linearly with increasing frequency as it did previously; the only difference is that the slope of the line changed. One suprising result of these trends is that an increase in voltage by adjusting the potentiometers had virtually no effect on the maximum frequency at which the led would produce a signal.