Keison Digilert 100 Installation manual

3/06
Nuclear Radiation Monitor
Operation Manual

Contents Page
1 Introduction 1
How the Digilert 100 Detects Radiation 1
2 Features 1
The Display 3
The Switches 3
The Detector 4
The Ports 5
3 Operation 5
Units of Measurement 5
Starting the Digilert 100 5
Operating Modes 6
Operating Ranges and Response Times 6
Taking a Timed Total Count 7
Using the Alert 8
The Utility Menu 9
Interfacing to an External Device 10
4 Common Procedures 10
Establishing the Background Count 11
Environmental Area Monitoring 11
Checking an Object 11
5 Maintenance 12
Calibration 12
Troubleshooting 15
6 Basics of Radiation and Its Measurement 16
Ionizing Radiation 17
Measuring Radiation 18
Radiation Measurement Units 18
Determining What Is a High Reading 19

Contents Page
Appendix A Technical Specifications 20
Appendix B Options 21
Observer Software 22
Warranty 23
Calibration Database Application 24
Precautions
To keep the Digilert 100 in good condition, handle it with care, and
observe the following precautions:
* Do not contaminate the Digilert 100 by touching it to radioactive
surfaces or materials.
* Do not leave the Digilert 100 in temperatures over 122* F (50
C) or in direct sunlight for extended periods of time.
* Do not get the Digilert 100 wet. Water can damage the circuitry
and the coating of the mica surface of the Geiger tube.
* Avoid making measurements with the detector window in direct
sunlight; this could affect the readings if the coating of the mica
surface of the Geiger tube has been damaged by moisture or
abrasion.
* Do not put the Digilert 100 in a microwave oven. It cannot
measure microwaves, and you may damage it or the oven.
* If you expect to not use the Digilert 100 for longer than one
month, remove the battery to avoid damage from battery
corrosion.
* Change the battery promptly when the battery indicator appears
on the display.

1
1 Introduction
The Digilert™ 100 is a health and safety instrument that measures alpha, beta,
and gamma radiation. With the Digilert 100, you can:
* Monitor possible radiation exposure while working near radionuclides
* Ensure compliance with regulatory standards
* Check for leakage from X-ray machines and other sources
* Set the alert level and use the Digilert 100 in Alert mode; if the radiation
goes above the level you set, the alert beeper sounds to let you know
* Screen for environmental contamination or environmental sources of
radioactivity
* Connect the Digilert 100 to a computer or data logger to record and
tabulate your data
This manual gives complete instructions for using the Digilert 100 and
procedures for common applications.
How the Digilert 100 Detects Radiation
The Digilert 100 uses a Geiger-Mueller tube to detect radiation. The Geiger
tube generates a pulse of electrical current each time radiation passes through
the tube and causes ionization. Each pulse is electronically detected and
registers as a count. The Digilert 100 displays the counts in the mode you
choose: counts per minute (CPM), milliroentgens per hour (mR/hr), or total
counts for a timed period. In SI units, counts per second (CPS) and
microsieverts per hour ( μSv/hr) are used.
2 Features
The Digilert 100 measures alpha, beta, gamma, and x-ray radiation. This
chapter briefly describes the Digilert 100's functions. For more information on
how to use the Digilert 100, see Chapter 3, "Operation."
The Digilert 100 counts ionizing events and displays the results on the liquid
crystal display (LCD) (4). You control which unit of measurement is shown by
using the mode switch.

Whenever the Digilert 100 is operating, the red count light (1) flashes each time
a count (an ionizing event) is detected.
The Display
Several indicators on the LCD (1)show information about the mode setting, the
current function, and the battery condition.
" The numeric display (A) shows the current radiation level in the unit
specified by the mode switch setting.
" A small battery (B) appears to the left of the numeric display to indicate
low battery voltage.
2
(1) LCD Display
(8) CAL Input
(7) Count Light (3) On/Off/Audio
Switch
(2) Mode Switch
(9) Output
(5) Plus & Minus Buttons
(4) Set Button
Illustration 1
Illustration 2

" A radiation symbol (C)
appears when the Alert feature is on.
" An hourglass (D) appears to the left of the numeric display during a timed
count.
" TOTAL (E) appears when the Digilert 100 is in Total mode.
" X1000 (F) appears when the radiation level is displayed in X1000 mode.
" CAL (G) appears while you are calibrating the Digilert 100.
" SET (H) appears when you are setting the timer, the Alert level, or the
calibration factor, or working in the Utility menu (the numeric display shows
the setting you are adjusting instead of the current radiation level).
" The current unit of measurement (I)- CPM, CPS, mR/hr or μSv/hr--is
displayed to the right of the numeric display.
" MENU (J) appears when you are in the Utility Menu.
The Switches
The Digilert 100 has two switches on the front, and three buttons on the end
panel. Each switch has three settings, which are described below.
On/Off/Audio Switch (3)
Audio. The Digilert 100 is on, and it makes a clicking sound for each radiation
event detected.
On. The Digilert 100 is operating, but audio is off.
3
(A) Numeric Display
(B) Low Battery
(C) Alert
(D) Timer
(E) Total
Mode
(I) Units of
Measurments
(H) Utility Menu, Timer,
Calibation, Alarm
Set Mode
(G) CAL
Mode
(F) X1000
Mode
(J) Menu
Illustration 3

Off. The Digilert 100 is not operating.
Mode Switch (2)
mR/hr. The numeric display shows the current radiation level in milliroentgens
per hour from .001 to 110. When SI units are used, it shows the current
radiation level in microsieverts per hour, from .01 to 1100.
CPM. The display shows the current radiation level in counts per minute from 0
to 350,000. When X1000 is shown, multiply the numeric reading by 1000 to get
the complete reading. When SI units are used, the display shows the current
radiation level in counts per second from 0 to 3,500.
Total. The display shows the accumulated total of counts starting when the
switch is turned to this position, from 0 to 9,999,000. When X1000 is shown,
multiply the numeric reading by 1000 to get the complete reading.
Set Button (Figure 2 (4))
The Set button is used to set the alert, select items in the Utility Menu, and
set the Calibration settings. See “Using the Alert” and “Utility Menu” in
Chapter 3 and “Calibration” in Chapter 5.
+ and - Buttons (Figure 2 (5))
The “+” and “-” buttons are used to adjust the numeric display for timed
counts, alert settings, and calibration settings. See “Taking a Timed Count”
and “Setting the Alert” in Chapter 3 and “Calibration” in Chapter 5.
The “+” and “-” buttons can also be used to make selections in the “Utility
Menu”. For details, see “Utility Menu” in Chapter 3.
The Detector
The Digilert 100 uses a Geiger tube to detect radiation. Alpha radiation does
not penetrate most solid materials, so this Geiger tube has a thin disk of mica,
which alpha radiation can penetrate, on its end. The screened opening at the
top of the Digilert 100 is called the window. It allows alpha and low-energy beta
and gamma radiation to penetrate the mica end of the tube.
CAUTION: The mica end surface of the Geiger tube is fragile. Be careful not to
let anything penetrate the screen.
4

The Ports
There are two ports on the left side of the Digilert 100.
The calibration input port (2) is used for calibrating electronically using a pulse
generator. For more information, see "Calibrating Electronically" in Chapter 5.
The output port (3) below the calibration input port allows you to interface the
Digilert 100 to a computer, data logger, or other device using a 3.5 mm stereo
plug. For more information, see "Interfacing to an External Device" in Chapter
3.
3 Operation
The guidelines in this chapter describe how to use the Digilert 100.
Units of Measurement
The Digilert 100 is designed both for users of conventional units (milliroentgens
per hour and counts per minute) and for users of SI units (microsieverts per
hour and counts per second). To switch between conventional and SI units, use
the Utility Menu. See "The Utility Menu" in this chapter.
Starting the Digilert 100
Be sure that a standard 9-volt alkaline battery is installed in the battery
compartment in the lower rear of the Digilert 100. Note: When installing the
battery, place the battery wires along the side of the battery and not under it.
To start the Digilert 100, set the top switch to the mode you want, and set the
bottom switch to On or Audio. The Digilert 100 then does a four-second system
check, displaying all the indicators and numbers.
After the system check, the radiation level is displayed in the selected mode.
One minute after you start the Digilert 100, a short beep indicates that enough
information has been collected to ensure statistical validity.
Operating Modes
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When the mode switch is set to mR/hr or CPM, the numeric display is updated
every three seconds. At low count rates, significant changes in the radiation
level displayed can take up to one minute to stabilize. See "Operating Ranges
and Response Times" in this chapter for more information.
CPM (or CPS) and timed total counts are the most direct methods of
measurement; mR/hr (or μSv/hr) is calculated using a conversion factor
optimized for Cesium-137, so this mode is less accurate for other radionuclides,
unless you have calibrated the Digilert 100 for a specific radionuclide using an
appropriate source. It is more appropriate to measure alpha and beta activity
using CPM than using mR/hr. Conversion for alpha and beta emitters is
calculated differently, and the Digilert 100's reading in mR/hr may not be
accurate.
The most immediate indicators of the radiation level are the count light, the
audio beep, and the alert. It takes three seconds before an increase is shown
on the numeric display in the dose rate modes.
Operating Ranges and Response Times
The following table shows the radiation levels the Digilert 100 measures in each
mode and how they are displayed. In some modes, when radiation levels
increase over certain preset levels, the Digilert 100 uses autoranging,
automatically changing to the X1000 scale. Whenever X1000 is shown above
the numeric display, multiply the displayed reading by 1000 to determine the
radiation level.
Mode Regular Range X1000 Range
mR/hr .001-110 NA
μSv/hr .01-1100 NA
CPM 0-9999 10,000-350,000
(displayed as 10.00-350, with X1000 indicator)
CPS 0-3500 NA
Total/Timer 0-9999 10,000-9,999,000
(displayed as 10.00-9999, with X1000 indicator)
Maximum level. When the maximum level for the current mode is reached, the
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Digilert 100 beeps for three seconds, pauses for three seconds, and repeats
that pattern. The numeric display flashes. The beeping pattern and the flashing
continue until the level decreases or the Digilert 100 is turned off.
Display update and response time. In Total mode, the numeric display is
updated each second. In the dose rate modes, the numeric display is updated
every three seconds. When the radiation level is less than 1,000 CPM, the
reading in any of the dose rate modes is based on the radiation detected in the
immediately previous minute. In order to give a quicker response to changes,
when the radiation level exceeds 1,000 CPM, the reading is based on the
previous 3 seconds, as shown in the following table. This automatic change in
response time is called auto averaging.
Radiation level Basis for reading
<1000 CPM or 1 mR/hr 1 minute
>1000 CPM or 1 mR/hr 3 seconds
Note: You can set the response time to 3 seconds at all radiation levels using
the Utility Menu; see "The Utility Menu" in this chapter.
Taking a Timed Total Count
The Digilert 100 can give you a total count for a timed period of from one minute
to 24 hours.
A timed total count is useful for determining the average counts per minute over
a period of time. The number of counts detected by the Digilert 100 varies from
minute to minute due to the random nature of radioactivity. When a count is
taken over a longer period, the average count per minute is more accurate, and
any small increase is more significant.
Taking an average allows you to detect low-level contamination or differences in
background radiation due to altitude or soil mineral content, and can be useful
for educational purposes. For example, if one 10 minute average is one count
higher than another 10 minute average, the increase may be due to normal
variation. But over 12 hours, a one count increase over the 12 hour
background average is statistically significant.
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To take a timed count, follow these steps:
1. With the Digilert 100 operating, set the Mode switch to Total. The display
shows SET, the hourglass, and the most recent timing period used. The
first time you use the timer, the setting is 00:01, which means one minute.
2. Use the + and - buttons to set the timing period. The timed period can be
for 1 to 10 minutes in one-minute increments, for 10 to 120 minutes in ten-
minute increments, or for 1 to 40 hours in one-hour increments.
3. Press the Set button. The Digilert 100 starts totaling the counts it registers,
and the numeric display is updated each time a count is registered. The
hourglass indicator flashes during the timed period.
During the counting period, if you want to see how many minutes remain,
press the Set button. The display counts down from the time setting in
hours and minutes to zero. For example, if the display shows 00:21, 21
minutes remain.
4. At the end of the timed period, the Digilert 100 beeps three times, and
repeats the beeping several times. The number displayed is the total
count.
5. To find the average dose rate for the timed period, divide the total by the
number of minutes.
The average count is in counts per minute. To convert to mR/hr for
Cesium-137, divide by 1000.
6. Move the Mode switch to one of the dose rate modes to return to normal
operation.
If you move the Mode switch to one of the dose rate modes while the Digilert
100 is taking a timed count, the timed count will stop.
Using The Alert
The Alert can be set in mR/hr or cpm. When using Utility Menu option #2 to
switch units of measurements, the alert is reset to the default alert level of .1
mR/hr (1.0 mS/hr). Once the alert threshold is reached the beeper will sound
until the alert is deactivated, or the radiation level drops below the set alert
threshold.
1. To set the Alert, press the "SET" button on the end panel. The "ALERT"
icon (radiation symbol) and the "SET" icon are displayed.
2. Use the "+" and "-" buttons to adjust the display to the desired level.
8

3. Press the "Set" button once to retain the setting in memory. Then press it
again to turn the alert mode on. The "ALERT" icon is now displayed to
indicate the instrument is operating in the Alert mode.
4. To use the previous alert setting, press the set button twice. Now the alert
mode is on.
5. To deactivate the Alert mode, press the "Set" button again. The "ALERT"
icon is no longer displayed.
The Utility Menu
The Utility Menu allows the user to change default settings for several operating
parameters. Once a setting is changed, it remains in effect unless they are
changed through the Utility Menu.
1. To activate the Utility Menu, hold down the “+” button while turning the
instrument on. The display will show the "MENU" icon. Release the “+”
button and a “1” indicating option 1 will appear along with the “Menu” icon.
2. Scroll through the menu by pushing the “+” or “-” buttons.
3. To select an option, push the “Set” button and the “SET” icon is displayed.
4. Use the “+” or “-” buttons to toggle between choices and press the “Set”
button to enter the new value. The instrument will continue to operate in
the Utility Menu mode, and the display will show "0" and "MENU". To
adjust another Utility Menu option, repeat the above steps.
5. To exit the Utility Menu at any time, press the SET button again. The
Digilert 100 continues with the normal start-up routine.
Options Function Comments
1. Auto Averaging or “on” selects Auto Averaging Refer to
3 sec. Averaging “oFF” selects 3 second “Response Time
(fast response) averaging (Autoaveraging)” in
Chapter 3
2. Units Of Selects between mR/hr
Measurements and CPM or μSv and CPS
Options Function Comments
9

3. Cal 100 Reset Automatically resets Cal Press the set Button
factor to 100 No toggling required
4, 5, 6 Reserved for future options
7. Cal Factor Adjust Manually adjusts cal factor Use “+” or “-”
Buttons to increase
or decrease the
value
8. Factory Default Automatically resets to Press the set Button
Reset Auto Averaging, mR/hr, CPM, No toggling required
and CAL 100
9. Revision # Displays software version number
Interfacing to an External Device
The lower output jack on the left side of the Digilert 100 is a dual miniature jack
that provides a data output that can be used to drive external devices. You can
use it to record the counts on a computer, data logger, or accumulating counter.
Use a 3.5 mm stereo plug to access this port. The outputs provide a positive
pulse (9 volt peak, 1 Kohm impedance) each time the Geiger tube detects a
count. At the tip of the plug, the pulse is approximately 1mS wide and is well
suited for chart recorders and audio output. The ring signal is approximately
80uS wide and is suitable for high speed counting and RS-232 interfacing. A
cable with an RS-232 connector (capacitor coupled) for an IBM PC-compatible
computer serial port and accompanying software are available from International
Medcom. A standard stereo or mono headphone can be plugged directly into
the jack. For some types of headphone, external volume control may be
needed.
4 Common Procedures
The following sections give guidelines for several commonly-used procedures.
With any procedure, the user must determine the suitability of the instrument or
procedure for that application.
Establishing the Background Count
Normal background radiation levels vary at different locations, according to
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altitude and other factors, such as types of minerals in the ground. Levels differ
at different distances from the ground, and may differ even in different areas of
the same room. To accurately interpret the readings you get on the Digilert 100,
it is a good idea to establish the normal background radiation level for each
area you plan to monitor. You can do this with a total/timed count. Use the
steps shown in "Taking a Timed Total Count" in Chapter 3 to get a ten-minute
average.
A ten-minute average is moderately accurate. You can repeat it several times
and see how close the averages are. To establish a more accurate average,
take a one-hour count. In some locations, you may want to take a longer count,
for example, 12 hours. If you need to determine whether there is prior
contamination, take averages in several locations and compare the averages.
Environmental Area Monitoring
You can keep the Digilert 100 in CPM or mR/hr mode whenever you want to
monitor the ambient radiation, and look at it from time to time to check for
elevated readings. You can also use Alert mode to warn you if the radiation
increases above the alert level.
If you suspect an increase in ambient radiation, use the timer to take a five or
ten minute count, and compare the average to your average background count.
If you suspect an increase that is too small to detect with a short timed reading,
you can take a longer count (for example 6, 12, or 24 hours).
Checking an Object
To check an object, put the Digilert 100 next to it. The end window should be
facing and close to the object; otherwise you may miss alpha and low-level beta
radiation. If you want to find out if an object is slightly radioactive, place the
Digilert 100 next to it and take a timed count over an appropriate period of time.
When you are not using the end window, hold the Digilert 100 so that the side
wall of the tube is as close as possible to the object. Alinging the symbol
marking the center of the detector close to the object is the best position. The
illustration at the right shows the position of the Geiger tube in the Digilert 100.
To measure as much as possible of the radioactivity of an object, place the
11

Digilert 100 as close as you can without touching
the object. The radiation level for gamma
radiation from a localized source decreases
according to the inverse square law. If you move
to twice the distance from the object, the radiation
drops by a factor of four.
CAUTION: Never touch the Digilert 100 to a
object that may be contaminated. You may
contaminate the instrument. A contaminated
instrument will not be accepted for repair or
servicing.
5 Maintenance
The Digilert 100 should be handled with care and
can be calibrated as necessary to comply with
regulations. Use the following guidelines to
maintain the Digilert 100 properly.
Calibration
The Digilert 100 should be calibrated as often as your regulations require. The
best way to calibrate is using a calibrated source. If no source is available, it is
possible to calibrate electronically using a pulse generator.
The standard radionuclide for calibration is Cesium-137. A certified calibration
source should be used. To calibrate the Digilert 100 for another radionuclide,
you must use a calibrated source for that radionuclide or the appropriate
conversion factor referenced to Cs-137.
CAUTION: In calibration mode, the smallest increment that can be adjusted is
.010, which prevents fine adjustment of the calibration factor. Thus, errors can
occur if you use a low-level source or background to set the calibration factor.
Calibrating Using a Source
Before you calibrate the Digilert 100, make sure the distance between the
12

Digilert 100 and the source is correct to produce the appropriate dose rate.
Place the Digilert with the end panel facing the source and the center of the
alpha window aligned with the center of the source. When using Cs-137 for
gamma calibration, place the Digilert with the rear of the instrument facing the
source (to filter the beta emissions) and the center of the Geiger tube (indicated
by the symbol on the rear label) aligned with the center of the source. This
filters the beta emissions. Follow these steps:
1. Start with the Digilert 100 turned off and the Mode switch set to mR/hr.
2. Hold down the - button on the end panel while you turn the On/Off/Audio
switch to On. (Don't use the Audio setting.)
The display shows CAL, and the Digilert 100 counts down for 15 seconds,
beeping each second. This delay gives you a chance to move out of the
field and then expose the source. At the end of the 15 seconds, the
Digilert 100 beeps several times.
3. The Digilert 100 collects data for 60 seconds, beeping as it does so, with
CAL and the hourglass indicator flashing. At the end of the 60 seconds, it
beeps several times. The display shows CAL and SET. You can now seal
or close the source.
4. Press the + and - buttons to adjust the reading to what it should be. When
the reading is correct, press the Set button. The new calibration factor is
automatically calculated from the adjustment you make.
5. The new calibration factor is displayed for several seconds, then the
Digilert 100 beeps and resumes regular operation.
The calibration factor is set to 100 (percent) at the factory. If you change the
reading, for example, to 20% higher than the factory reading, the new
calibration factor would be 120. The current calibration factor is displayed
during the system check when the Digilert 100 is first turned on.
Calibrating Electronically
You can calibrate electronically using a pulse or function generator. Electronic
calibration requires a cable with a 2.5 mm plug, with the tip carrying the signal.
Follow these steps:
1. Set the signal height to 3.3 volts (positive pulse) and the pulse width to 80
microseconds.
13

CAUTION: Do not inject a pulse when the Digilert 100 is turned off. Do
not exceed 5 volts.
2. Plug the cable into the upper jack.
3. Start with the Digilert 100 turned off and the Mode switch set to mR/hr.
Hold down the - button on the end panel while you turn the On/Off/Audio
switch to On. (Don't use the Audio setting.)
The display shows CAL, and the Digilert 100 counts down for 15 seconds,
chirping each second. At the end of the 15 seconds, the Digilert 100
beeps several times.
4. The Digilert 100 collects data for 60 seconds, beeping as it does so, with
CAL and the hourglass indicator flashing. At the end of the 60 seconds, it
beeps several times. The display shows CAL and SET.
5. Use the following table to check the Digilert 100's accuracy. The table
shows appropriate pulse generator count rates to calibrate for Cs137. If
the accuracy is not within desired limits, follow steps 5-7. Note that the
Digilert 100 automatically compensates for lost counts due to GM tube
dead time. Thus, the display reading in CPM mode does not equal the
input frequency. You can display uncompensated counts in CPM mode by
continuously holding down the - (minus) button; the reading now
corresponds to the input frequency.
Pulse Generator CPM mR/Hr μSv/hr CPS
Input (PPM)
11,629 11,994 10 100 205
22,661 23,888 20 200 399
52,600 59,720 50 500 995
78,541 95,552 80 800 1,593
93,993 119,440 100 1,000 1,991
6. Press the + and - buttons to adjust the reading to what it should be. When
the reading is correct, press the Set button. The new calibration factor is
automatically calculated from the adjustment you make.
7. The new calibration factor is displayed for several seconds, then the
Digilert 100 beeps and resumes regular operation.
14

Troubleshooting
The Digilert 100 is a highly reliable instrument. If it does not seem to be
working properly, look through the following chart to see if you can identify the
problem.
Problem Possible Cause What To Check
Display is blank no battery, dead battery, install a new 9-volt battery
poor battery connection if count light and audio
defective LCD work, the LCD may
need to be replaced
Display works, but no defective Geiger tube look through the window
to counts are registered check the mica surface of
the tube; if it is wrinkled or
a break is visible replace it
Reading is high, but contamination scan the Digilert 100
another instrument; with another instrument
has a normal reading clean instrument with
water and mild detergent
Instrument has false moisture circuit board may be wet;
high reading dry the instrument in a
warm dry place; if it still
has a problem, it requires
service
15

Problem Possible Cause What To Check
Instrument has false photosensitivity remove from direct
high reading sunlight and ultraviolet
sources; if the high count
drops, the mica window
coating may have washed
off the Geiger tube due to
getting wet; the tube will
need to be replaced
Instrument has false continuous discharge replace the Geiger tube
high reading
Instrument has false electromagnetic field move the instrument away
high reading from possible sources of
electromagnetic or radio
frequency radiation
Service
If the Digilert 100 requires servicing, please contact your distributor or the
manufacturer at the following address:
Do not attempt to repair the Digilert 100; it contains no user-serviceable parts
and you could void your warranty.
CAUTION: Do not send a contaminated instrument
for repair under any circumstances.
S.E. International, Inc
P.O. Box 39, 436 Farm Rd
Summertown, TN 38483-0039
Tel: [phone], Fax: [phone] E-mail: [email protected]
6 Basics of Radiation and Its Measurement
This chapter briefly tells what radiation is and how it is measured. This
information is provided for users who are not already familiar with the subject. It
is helpful in understanding how the Digilert 100 works and in interpreting your
16

readings.
Ionizing Radiation
Ionizing radiation is radiation that changes the structure of individual atoms by
ionizing them. The ions produced in turn ionize more atoms. Substances that
produce ionizing radiation are called radioactive.
Radioactivity is a natural phenomenon. Nuclear reactions take place
continuously on the sun and all other stars. The emitted radiation travels
through space, and a small fraction reaches the Earth. Natural sources of
ionizing radiation also exist in the ground. The most common of these are
uranium and its decay products.
Ionizing radiation is categorized into four types:
X-rays are usually manmade radiation produced by bombarding a metallic target
with electrons at a high speed in a vacuum. X-rays are electromagnetic
radiation of the same nature as light waves and radio waves, but at extremely
short wavelength, less than 0.1 billionth of a centimeter. They are also called
photons. The energy of X-rays is millions of times greater than that of light and
radio waves. Because of this high energy level, X rays penetrate a variety of
materials, including body tissue.
Gamma rays occur in nature and are almost identical to X rays. Gamma rays
generally have a shorter wavelength than X-rays. Gamma rays are very
penetrating; thick lead shielding is generally required to stop them.
Beta radiation. A beta particle consists of an electron emitted from an atom. It
has more mass and less energy than a gamma ray, so it doesn't penetrate
matter as deeply as gamma and X-rays.
Alpha radiation. An alpha particle consists of two protons and two neutrons, the
same as the nucleus of a helium atom. It generally can travel no more than 1 to
3 inches in air before stopping, and can be stopped by a piece of paper.
When an atom emits an alpha or beta particle or a gamma ray, it becomes a
different type of atom. Radioactive substances may go through several stages
of decay before they change into a stable, or non-radioactive, form.
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