Transcript Detecting radiationx

Detecting Radiation
Oui!
It is Friday apres-midi!
Time for a bottle du vin avec ma petit
fille.
Oi Vay!
The lab is une grande mess.
Je will sweep tout la merde into a
drawer!
Voila !
Clean!
Parfait!
Detecting Radiation
Becquerel's photographic plate, fogged by exposure to radiation from a uranium
salt. The shadow of a metal Maltese Cross placed between the plate and the
uranium salt is clearly visible.
Electroscope: a static electricity detector
The leaves repel
each other, since
they have the same
charge.
Over time, as
invisible charged
particles zip
through the
electroscope, they’ll
neutralize some of
the positive charge,
and the leaves will
relax.
Victor Hess carried an
electroscope aloft many
times between 1911 and
1913.
He expected that it
would be less affected by
the Earth’s radioactivity
at higher altitudes.
But NO!
Radiation was coming
from beyond the Earth,
also.
Nobel Prize!
Ding!
Cloud Chambers & Bubble Chambers rely
on PHASE CHANGES caused by passing
unseen particles…
Cloud Chamber
A Geiger counter is a metal case filled with a certain type of gas.
Inside the metal case is a positively charged wire with just under the voltage required to ionize the gas within the
container.
When a charged particle enters through a thin glass panel at one end of the counter, it ionizes the particles of gas
within the chamber.
These particles are attracted towards the positively charged wire.
As they accelerate towards the wire, they ionize additional particles.
As the particles strike the wire, they create a voltage pulse which is amplified and sent to an electric counter.
These pulses can also be sent to a loudspeaker, which causes each pulse to be heard as a “click” sound.
Bubble Chamber….
Geiger Counter
A Geiger counter is a metal case filled with a certain type of gas.
Inside the metal case is a positively charged wire with just under the voltage required to ionize the gas within the
container.
When a charged particle enters through a thin glass panel at one end of the counter, it ionizes the particles of gas
within the chamber.
These particles are attracted towards the positively charged wire.
As they accelerate towards the wire, they ionize additional particles.
As the particles strike the wire, they create a voltage pulse which is amplified and sent to an electric counter.
These pulses can also be sent to a loudspeaker, which causes each pulse to be heard as a “click” sound.
Most silicon particle detectors work, by
doping narrow (usually around 100
micrometers wide) strips of silicon to make
them into diodes. As charged particles pass
through these strips, they cause small
ionization currents which can be detected and
measured.
Arranging thousands of these detectors
around a collision point in a particle
accelerator can give an accurate picture of
what paths particles take. Silicon detectors
have a much higher resolution in tracking
charged particles than older technologies such
as cloud chambers or wire chambers.
The drawback is that silicon detectors are
much more expensive than these older
technologies and require sophisticated
cooling to reduce leakage currents (noise
source) as well as suffer degradation over
time from radiation.
Photomultiplier tubes (photomultipliers or PMTs for short),
are extremely sensitive detectors of light in the ultraviolet, visible, and
near infrared ranges of the E-M spectrum. These detectors multiply the
current produced by incident light by as much as 100 million times in
multiple stages, enabling individual photons to be detected when the
incident flux of light is very low. Unlike most vacuum tubes, they are
not obsolete.