The Effect of Artificial Lighting on a Cosmic Ray Detector

The Fluorescent Starbursts on a Black Background Nasser Al Buloushi Jillian Avalon Graden Barnes Renee Batzloff Teacher: Tom Brestel

Background The purpose of a photomultiplier tube is to amplify light so that it is easier to detect. In a cosmic ray detector, photons emitted by the excited electrons from the scintillator are sent into the tube, and hit the photocathode, a plate coated with a light-sensitive material. When the photons strike the plate, electrons are produced. These electrons travel back and forth through the tube, hitting the plates, and colliding with each other, producing more electrons and photons. This activity continues until there is enough electrons to create a signal large enough for the detector to sense.

Background Due to the sensitivity of photomultiplier tubes, phototube noise is created. This occurs when an outside source excites electrons producing a signal, and essentially deceiving the cosmic ray counter, which causes the count to be higher. To minimize this noise, two scintillator paddles are used “in coincidence” , meaning that the particle must pass through both scintillators in order to register.

Objective To see how much artificial light affects the amount of cosmic ray counts.

Hypothesis An outside light source will cause the photomultiplier tube to increase the cosmic ray count.

Materials Cosmic Ray Detector Artificial Light Source Light Bulbs of Varying Wattage Aluminum Foil Cardboard

Procedure Obtain a Cosmic Ray Detector Set the detector to the following settings- upper single, infinite count, count mode. Under room light, turn on the detector for 10 minutes, and record the cosmic ray count. Repeat 2 more times , then calculate the baseline average.

Procedure 5. Set up the light so that it shines directly on the upper scintillator. 6. Cover the lamp shade with aluminum foil. 7. Before turning on the detector, let the lamp run for a few minutes. 8. Turn on the detector, and after 10 minutes, record the cosmic ray count. 9.Repeat 2 more times. Change the bulb every 3 trials.

Data Base Count (Bottom Paddle) Reading 1 7611 counts Error 87 counts Average 7937 counts 139 counts Base Line Reading (Set 1) Reading 1 3174 counts Error 56 counts Reading 2 3018 counts 55 counts Reading 3 2951 count 54 counts Average 3048 counts Reading with 25 Watt Light Bulb Reading 1 3080 counts Error 55 counts Reading 2 3021 counts Reading 3 2998 counts Average 3033 counts 20 counts Reading with 75 Watt Light Bulb (Bottom Paddle) Reading 1 7794 counts Error 88 counts Reading 2 7704 counts Reading 3 7803 counts Average 7767 counts 26 counts Reading with 60 Watt Black Light (Bottom Paddle) Reading 1 7779 counts Error 88 counts Reading 2 7803 counts Reading 3 7892 counts 89 counts Average 7825 counts 28 counts Reading with 75 Watt Light Bulb Reading 1 26385 counts Error 162 counts Reading 2 26186 counts Reading 3 7252 counts 85 counts Average 19941 counts 5181 counts

Data Base Count (Counter 2) Reading 1 3214 counts Error 57 counts Average 3481 counts 114 counts Reading with 75 Watt Light Bulb (Counter 2) Reading 1 2991 counts Error 55 counts Reading 2 2488 counts 50 counts Reading 3 2837 counts 53 counts Average 2772 counts 121 counts Reading with 60 Watt Black Light (Counter 2) Reading 1 3311 counts Error 58 counts Reading 2 3605 counts 60 counts Reading 3 3126 counts 56 counts Average 3347 counts 114 counts

Error Analysis

Error Analysis As you can see from the previous graph, the 75 watt bulb seemed to have a huge impact on the scintillator. However, when our group tried to confirm our results, we realized we had run into a systematical error, and the Cosmic Ray Detector was giving us inaccurate results. Based on our data, and background information, we made the logical conclusion that the heat from the light bulbs changed the sensitivity of the Cosmic Ray Detector.

Error Analysis When our group compared the error range of the base line readings and the trials with lights on the cosmic ray detector we found that the error ranges overlapped. Based on this information, we can make the conclusion that the light did not have as much of an effect as we had first thought.

Conclusion After analyzing the data, we believe that it proves inconclusive as to the effects of artificial lighting on cosmic ray detectors. However, based on our data, and background information, we have come to the logical conclusion that heat has a major effect on cosmic ray detectors. This is most likely what caused the systematical error we ran into.

The Fluorescent Starbursts on a Black Background