
Exposure Rate in an Air-Filled Ion Chamber
X
=
I / m[1 / (2.58E-4 C / kg
)
-R]
X
=
exposure rate
(
R / sec)
I
=
current (amperes)
m
=
mass of air in chamber (kg)
% Resolution of a Gamma Spec System
% R
= FWHM / peak energy x 100 = % resolution
FWHM
= peak energy width at full width half-max height
peak energy =
photopeak energy of interest
True Count Rate Based on the
Resolving Time of a Gas-Filled Detector
C
0
0
R
=
R / (1 - R Y) =
true count rate
0
R
=
observed count rate
Y
=
resolving time
Specific Gamma-Ray Constant (
Ã
) for Source Activity (A)
ã
en
air
Ã
=
ö
E (
ì
/
ñ
) e / W
Ã
=
specific gamma constant (R-cm / hr-A)
2
ö
=
photon fluence rate (
ã
/ cm -hr)
2
ã
E
=
gamma photon energy (MeV)
en
(
ì
/
ñ
) =
density thickness of air (g / cm )
2
e
=
electron charge (Coulombs)
W
=
average amount of energy to produce an ion
pair in air (eV)
Dose Rate (D) to Air from a Point Beta Source
D
=
300 A / d =
rad /hr
2
A
=
source activity in curies
d
=
distance from source in feet
61
Exposure Rate in an Air-Filled Ion Chamber
X
=
I / m[1 / (2.58E-4 C / kg
)
-R]
X
=
exposure rate
(
R / sec)
I
=
current (amperes)
m
=
mass of air in chamber (kg)
% Resolution of a Gamma Spec System
% R
= FWHM / peak energy x 100 = % resolution
FWHM
= peak energy width at full width half-max height
peak energy =
photopeak energy of interest
True Count Rate Based on the
Resolving Time of a Gas-Filled Detector
C
0
0
R
=
R / (1 - R Y) =
true count rate
0
R
=
observed count rate
Y
=
resolving time
Specific Gamma-Ray Constant (
Ã
) for Source Activity (A)
ã
en
air
Ã
=
ö
E (
ì
/
ñ
) e / W
Ã
=
specific gamma constant (R-cm / hr-A)
2
ö
=
photon fluence rate (
ã
/ cm -hr)
2
ã
E
=
gamma photon energy (MeV)
en
(
ì
/
ñ
) =
density thickness of air (g / cm )
2
e
=
electron charge (Coulombs)
W
=
average amount of energy to produce an ion
pair in air (eV)
Dose Rate (D) to Air from a Point Beta Source
D
=
300 A / d =
rad /hr
2
A
=
source activity in curies
d
=
distance from source in feet
61
Exposure Rate in an Air-Filled Ion Chamber
X
=
I / m[1 / (2.58E-4 C / kg
)
-R]
X
=
exposure rate
(
R / sec)
I
=
current (amperes)
m
=
mass of air in chamber (kg)
% Resolution of a Gamma Spec System
% R
= FWHM / peak energy x 100 = % resolution
FWHM
= peak energy width at full width half-max height
peak energy =
photopeak energy of interest
True Count Rate Based on the
Resolving Time of a Gas-Filled Detector
C
0
0
R
=
R / (1 - R Y) =
true count rate
0
R
=
observed count rate
Y
=
resolving time
Specific Gamma-Ray Constant (
Ã
) for Source Activity (A)
ã
en
air
Ã
=
ö
E (
ì
/
ñ
) e / W
Ã
=
specific gamma constant (R-cm / hr-A)
2
ö
=
photon fluence rate (
ã
/ cm -hr)
2
ã
E
=
gamma photon energy (MeV)
en
(
ì
/
ñ
) =
density thickness of air (g / cm )
2
e
=
electron charge (Coulombs)
W
=
average amount of energy to produce an ion
pair in air (eV)
Dose Rate (D) to Air from a Point Beta Source
D
=
300 A / d =
rad /hr
2
A
=
source activity in curies
d
=
distance from source in feet
61
Exposure Rate in an Air-Filled Ion Chamber
X
=
I / m[1 / (2.58E-4 C / kg
)
-R]
X
=
exposure rate
(
R / sec)
I
=
current (amperes)
m
=
mass of air in chamber (kg)
% Resolution of a Gamma Spec System
% R
= FWHM / peak energy x 100 = % resolution
FWHM
= peak energy width at full width half-max height
peak energy =
photopeak energy of interest
True Count Rate Based on the
Resolving Time of a Gas-Filled Detector
C
0
0
R
=
R / (1 - R Y) =
true count rate
0
R
=
observed count rate
Y
=
resolving time
Specific Gamma-Ray Constant (
Ã
) for Source Activity (A)
ã
en
air
Ã
=
ö
E (
ì
/
ñ
) e / W
Ã
=
specific gamma constant (R-cm / hr-A)
2
ö
=
photon fluence rate (
ã
/ cm -hr)
2
ã
E
=
gamma photon energy (MeV)
en
(
ì
/
ñ
) =
density thickness of air (g / cm )
2
e
=
electron charge (Coulombs)
W
=
average amount of energy to produce an ion
pair in air (eV)
Dose Rate (D) to Air from a Point Beta Source
D
=
300 A / d =
rad /hr
2
A
=
source activity in curies
d
=
distance from source in feet
61