m 0 000 000 000 001 00 6748

m = 0. 000 000 000 001 00 6748 kg proton melectron = 0. 000 000 0009 kg mproton = 1836 melectron Each individual electron is a mere one 10 thousandths to several hundred thousandths of an atom’s mass!

Affinity: a natural liking or sympathy close: stronger attraction electron jumps Some atoms/molecules attract electrons more strongly than others. far: weaker attraction F 12 r

Electron Affinity rabbit’s fur glass wool silk rubber hard plastic Different materials have different electrons affinities When fur is rubbed across a plastic rod, both acquire an equal but opposite charge. plastic rod fur If the fur merely rests on top of the plastic, each will acquire equal and opposite charges. 1) True. 2) False. Friction is necessary to provide enough heat (energy) for electrons to jump from the fur to the plastic.

Some plastics readily stick to glass surfaces by static cling alone. Poly vinylidene chloride [PVd. C] with polyisobutylene [PIB] and polyethylene-vinylacetate [EVA] additives generates enough static to stick to itself!

A spark is often observed when plugging or unplugging an appliance.

Charge is invisibly small but sparks are visible! What are they made of? Why can we see them?

+ The sudden cascade of many + electrons leaping across the gap + produces the visible flash of light + + + + + is NOT made up of electrons. Light + When electrons jump they create“electromagnetic waves”of light. + -

Read out by 10 stage EMI 9256 photomultiplier tube PMMA (polymethyl methacrylate) doped with a scintillating fluor 2 ft x ½ inch

Measuring the threshold setting with a voltmeter Test Points for the 4 Threshold Voltages are labelled: TPVTH 1 TPVTH 2 TPVTH 3 TPVTH 4 The mounting holes are all GROUNDed

Thresholds are adjustable through the potentiometers with a jewelers screwdriver.

At LOW THRESHOLD we expect to be dominated by noise, which plummets rapidly with threshold. 100000 1000 Its exponential drop should ideally look like a straight line on a logarithmic plot. At HIGH THRESHOLD background noise is pretty much eliminated; any additional increase in threshold will actually start cutting into the real signal. 1000 100 50 100 Threshold (milli. Volts) 150

Try to confirm your selection by eye, with an oscilloscope, adjusting it’s own trigger threshold. A very low threshold will have the oscilloscope almost continuously triggering, revealing a band of noise. Moving the threshold just far enough to kill the noise and give only the flickering images of healthy signals can give you an approximate idea of where threshold should be set. Note: the DAQ card has a built-in x 2 amplifier, so uses thresholds twice the size of the ones you'll need to set for the oscilloscope trigger. (i. e. , a threshold of 65 m. V from the DAQcard scan corresponds to a 32 m. V trigger threshold on the oscilloscope).

Number of “triggers” Trigger 1 Count the total number of “two-fold” coincidences between the top and bottom panel. Test Counter 1 Test Counter 2 Trigger 2

Threshold scans all detectors can run off the same single power supply. Efficiency scans the "trigger" detectors (the top and bottom in the telescope stack) must remain at a fixed high voltage, while the "test" counters in the middle have their high voltage varied in a scan. This requires using two different power supplies. . . one for the triggers another for the tests.

To get the most accurate measure of the efficiency of the test counters Trigger 1 Test Counter 2 Trigger 2 the TRIGGER counters must be operating at high efficiency. 1) True. 2) False.