Hi....I'm Tom Iannarelli
This is my 1st home page, and I have a lot more pictures
to put on this page,
But I don't have a scanner handy....sorry.
I'm interested in Physics, chemistry, poetry, music (anything
except country),
all sports, and my friends and family.
I have a girlfriend named Melissa, and I've been seeing
her for over two and a half years.
Love ya babe.
Here's
my loved ones
I also have a few great friends, Ashley, Leslie, Joan, Jill, Josh, Chris, and Justin
I'd like to give a little shout out to all the great people
and friends I've made here at IU...Evann, Jonee, Tim, Amanda, and Betsy
Here's
Pics of them
Here's
my school pic
Here's
my team
Peace...
Journal
Electronic documentation
Plateau ? the operating voltage of our PMTs is between 1400v ? 1700v. The plateau is the optimum voltage where small fluctuations in PMT voltage produces very small changes in the PMT signal. Plateauing is finding this optimum voltage. The voltage on the PMT is varied and we count the number of signals in one minute from a scintillator in a light tight environment, and in the presence of a sodium 22 source. The PMT signal is discriminated and counted on a scalar.
The operating voltage of our PMT is supplied by a Crockcroft ? Walton base. It is powered by a 15 volt power supply, and can control the voltage at the PMT from 1024v ? 2048v. To control the voltage, two 32 bit Binary words are sent to the base. The first word supplies the base address, the second controls the addressing mode and sets the operating voltage. The two words are entered on a test panel using two sets of four hexadecimal bytes.
While finding the plateaus, Dave told us first that the test panel voltage settings are in hexadecimal (A base 16 number.) We choose the decimal voltage, and find the hexadecimal code for that particular voltage and the test panel sends the appropriate binary code to the base to set the desired voltage.
Once you've chose a hexadecimal value to test at, you are ready to start the plateau. First, you need to hook up a PMT to the base (Make sure you take the PMT # which is on the little gold plate.) Set all its settings to zero. (The settings are inside the base tubes.) Make sure the power source is off, and connect the bases to the power source. Connect the base to a crate on an in slot. This will send the # of counts to the crate to be processed. Then, connect the crate to the counter in the out slot under the in slot. Then you should be ready to start counting. All you need is a scintillation detector with a radioactive material behind it. We used sodium 22 at 10 centimeters to the tube. Put the unpowered base and PMT into a light tight environment, and seal the light tight environment.
Once we were all ready, and had the PMT in the light tight box, we started
counting. We had no idea what to be looking for, but we were sure
there would be a huge jump in the readings after we reached the plateau.
We started at a voltage of 1300v and first increased the voltage by 100v.
This ended up being harder to find a plateau, se we decided to change the
100v increments to 20v. This was extremely accurate, and we found
the plateau easily.
plateau
drawing
plateau
pictures
Journal 2
Coincidence - The comic ray telescope is two scintillating plates held in parallel planes with an 18 inch separation A coincidence occurs when a cosmic ray passes through both plates The PMTs produces signals from thermal energy (noise) as well as cosmic rays. Noise signals occur at kilohertz rate and are very unlikely to occur in both plates at the same instant. Signals from cosmic rays WILL occur in both plates within nanoseconds, which produces a coincidence.
The signals from the two PMTs are discriminated to produce a digital
pulse. The digital pulses are sent to an AND gate. If both inputs of
the AND gate are high indicating signals, the output goes high and the
coincidence is observed and counted on a scalar. The coincidences can
be detected at a megahertz rate.
Journal 3
It is very important to make sure that the plates are light tight because
that is what the PMT's are designed to sense. If the assembly lets
in light then we will not get a true
reading of the number of cosmic rays. Therefore, once it is wrapped
it must be tested for light leaks. This can be done by running the
output from the assembly to the
discriminator and then to the counter. Set the voltage such that
you see a steady flow of counts. And set the threshold as low as
it will allow in order to distinguish between
light and noise. Once this is set up you simply run a light across
the whole detector while watching the counter; if the counter shows many
counts at once, then go over it
again to make sure that you might be leaking light. If it is
a leak then use some black tape to seal up the hole and repeat until you
finish the whole plate.
Hear are a few links I love
cool animation
funny stuff
great stuff to do, when you have
nothing to do
good download site for music
joecartoon