Near Space
collision of a cosmic ray is called a
secondary shower.
Particles in the secondary shower
continue traveling toward the surface,
sometimes colliding with other molecules lower in the atmosphere and
creating more secondary showers.
Eventually, secondary showers are
attenuated by the Earth’s atmosphere, protecting us from harm.
There can be millions of subatomic
particles in a secondary shower and
they can cover several acres of land
once they reach the ground.
The secondary cosmic rays
detected on the Earth’s surface are
mostly muons. On average, there are
close to 100 of these muons impacting every square yard of land per
second. Some of the surviving
primary cosmic rays are so energetic
that they can be detected in
deep mines.
isotope, giving archeologists a great
method of dating (radiocarbon
dating) organic artifacts that are less
than 50,000 years old.
There are several good sources
of information on cosmic rays, like
the book A Thin Cosmic Rain by
Friedlander and several Internet
sources. (I didn’t have a problem with
finding nonsense when doing my
Internet search — unlike what occurs
with some topics.)
Detecting Cosmic
Rays with the Aware
Electronics RM- 60
Effects
Aircraft pilots and their passengers receive less protection from
cosmic rays by the Earth’s atmosphere than we do at sea level. Even
residents of Denver, CO (sorry
EOSS) receive more radiation cosmic
rays than do residents of San Diego,
CA. Not only is the flux of cosmic
rays greater at higher altitudes, but
the flux of cosmic rays also increases
the closer the aircraft flies to the
geomagnetic poles. The flux is
greater near the magnetic poles of
the Earth because the Earth’s
magnetic field dips earthward and
funnels cosmic rays to the surface.
The muons found in cosmic ray
showers have very short half lives.
Their half lives are so short that, if it
wasn’t for the time dilation caused by
their relativistic speeds, muons would
never live long enough to make the
trip down to the Earth’s surface,
where we can detect them.
Cosmic rays may modify the
Earth’s ionosphere, influence cloud
production, affect the ozone layer,
and possibly have an impact on our
weather. Cosmic rays convert some
of the nitrogen- 14 atoms in our
atmosphere into the carbon- 14
SEPTEMBER 2004
My tool of choice for measuring
cosmic rays in near space is the RM-
60 Geiger counter. This Geiger counter is manufactured by Aware
Electronics ( www.aw-el.com) as a
PC- or laptop-based radiation detection system. The RM- 60 measures 1-
1/4” by 2-3/8” by 4-3/8” and weighs
a mere 4 oz. It’s designed to take its
power ( 5 to 9 volts at about 2 mA)
from the serial port of a PC.
Software loaded on the PC records
and graphs the detections from the
RM- 60.
The manual that comes with
each unit is very thorough and even
contains background information and
suggested experiments.
The output from the RM- 60 is a
constant + 5 volt signal until an event
is recorded. At that point, the voltage
drops to 0 volts for the length of the
GM tube’s dead time. The BASIC
Stamp is quite capable of detecting
radiation from the RM- 60.
You only need to modify a phone
cable to interface the RM- 60 to the
BASIC Stamp. Imagine adding a
radiation detector to your BOE-BOT.
To interface the RM- 60, you will need
a telephone cable (the kind with RJ-
11 jacks on both ends) and a method
to connect one end of the phone
cable to your BASIC Stamp.
In a future column, I will discuss
the flight computer I use and how I
interface sensors to it.
For now, however, you can wire
the RM- 60 to a Board of Education
(BOE) and launch that on your near
spacecraft. Let’s modify the phone
cable. You’ll need about 10 minutes
to do this.
1. Cut one end off the telephone
cable (the other end is left in place so
it can plug into the RM- 60).
2. Strip about 1” of outer insulation
TM
MicroStamp11
The World”s Smallest
68HC11 Microcontroller
M o d u l e !
• harness the power of the world’s most popular 8-bit
microcontroller in your own projects!
• easy-to-use Windows interface for fast loading via
your PC’s serial port
• control LEDs, speakers, lights, relays, motors, LCDs,
servos, and much more with your own easy-to-write
programs
• “plug right in” to any solderless breadboard (with
included adapter), so you can try out your ideas fast!
• re-programmable in-circuit thousands of times!
• your program stays inside MicroStamp11™ until you
replace it– even with no power applied!
• runs on standard alkaline or NiCd batteries for hours,
or use a DC adapter
• tiny stamp-size 1.4 inch x 1.0 inch module
• demo of powerful new XPad visual programming
environment included with Starter Package!
toll-free USA and Canada • Starter Packages* from $49
1-877-963-8996 www.technologicalarts.com
* RS232 Docking Module, serial cable, manual, and software disk included in Starter Packages
99
