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7D10.80-u1 - Cosmic Ray Telescope

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​7D10.80-u1 - Cosmic Ray Telescope

Title7D10.80-u1 - Cosmic Ray Telescope

Demonstrate detection of muons from the upper atmosphere and also other high energy particles that meet the coincidence requirement established by the instrumentation.

Assembly Instructions

TEK O-Scope settings saved under Save/Recall Setting 3 (Sept. 2005)

The muon detector is built with several dedicated components. There is a processor (the bin assembly) which consists of an amplifier, discriminator, and coincidence tray; this is preassembled on a rack. The bin processes the signals from the two photomultiplier tubes (PMT) which are mounted at different elevations (in our case separated by ~3 feet). The bin outputs to an oscilloscope where comparisons can be made about the different rates of muon detection at different altitudes. Additionally, we include a speaker so that the sound of coincident muons can be heard by the class.

To assemble the demonstration, most electronic components are placed on the bottom of a 4’ cart. These include: the processor rack, the Tektronix scope, the high voltage power supply (HVPS), and the optional amplifier and speaker. On the top of the cart, place one PMT. Build a shelf with 4 bench clamps and 4 cross bars, and place the second PMT on top of that, about 3 feet above the other PMT.

Connecting the PMT to power
Plug the PMTs into the HVPS with the provided coaxial cables via a distribution switch. The power supply inputs are labeled (w/ color 6). The mini-coax outputs are labeled with color 7. The outputs go to the processor rack. Caution: Incorrect connection to the HVPS can destroy the detectors!

Input to the processor
The inputs to the processor rack are from the 2 PMT. The lower elevation detector is “Input 1” and the higher one is “Input 2” to the amplifier on the rack.

Output from the processor
The processor has five outputs, four to the oscilloscope and one to the optional speaker. We organize the scope inputs so the first two channels simply measure the number of incident muons on each plate. These channel inputs are labeled (color 1 & 2). They come from the amplifier. The third and fourth channels measure the number of coincident muons. The third channel, input color (color 3), displays coincident muons from the coincidence tray. The fourth input (color 4) shows a processed muon coincidence from the amplifier tray.

Optionally, we can output the signal of coincident muons to a speaker. Route the (color 5) coaxial cable from the coincidence tray’s output to a mini Radio Shack Amplifier, which is in turn output to a standard speaker.

Programming the Oscilloscope
Make the following settings to the TEK scope (most are found in the Quickmenu): DC Coupled (all), Impedance 50 Ohm (all), Ch1 @ 100mV, Ch2 &Ch3 @ 500mV, M(Hor)= 100ns, Trigger(Source) on Ch3, Set bandwidth to 20MHz, Trigger to Normal, Sample, Neg Slope, LF reject, Edge Trigger, Horizontal Resolution: Normal, Aquire: Wave Alert.  (April 2009) SET TRIGGER LEVEL TO NEGATIVE!! to view negative pulse!

Turning on the devices
First turn on the bins (the processor rack) and the optional amplifier. Only after the other devices are on will you turn on the HVPS. To turn on the HVPS, flip the switch and allow to warm up for 15 seconds. Switch to KV output, and VERY slowly dial in 1800 VDC. To turn the PS off, reverse those directions (dial down, turn off).

Optimizing the scope
The scope usually needs some tweaking to get it to trigger properly. Just adjust the trigger level until stable, then make sure that the display is properly indicating on the screen.

Setup Time30
Operation Time2
Preview Time5
Operation Instructions

Analyze the output on the oscilloscope, and explain what the students are hearing on the speaker. They are hearing coincident muons. The oscilloscope is shows three significant things: the number of incident muons on the top and bottom PMTs, and the coincident muons (muons incident on both tubes). The electronics are designed to measure "coincident" muons, i.e. a single muon that passes through both plates.

Demo on DimeNo
PIRA 200No
Export Instructions (if different)
Category7 Modern Physics
Subcategory7D - Nuclear Physics
Keywordsmuon, coincidence, relativistic, cosmic ray, telescope
Construction Information
PMT with scintillator assembly
bin assembly
oscilloscope - Tektronic, 4-channel
HVPS 0-2000 VDC
HV distribution box
amplifier 100W Radioshack stereo
pre-amp - Radioshack mini
bench clamp
bench rod
rod clamp
rod - long
rod - short
cosmic ray telescope wire accessories