Instrumentos para la detección de radiaciones

http://einstein.ciencias.uchile.clInstrumentación 2008/clases/Radiaciones

2008Rev OA martes, 18 de noviembre de 2008

Three types of radiation - Alpha, Beta, Gamma

There are three primary types of radiation:

Alpha - these are fast moving helium atoms. They have high energy, typically in the MeV range, but due to their large mass, they are stopped by just a few inches of air, or a piece of paper.

Beta - these are fast moving electrons. They typically have energies in the range of a few hundred keV to several MeV. Since electrons are much lighter than helium atoms, they are able to penetrate further, through several feet of air, or several millimeters of plastic or less of very light metals.

Gamma - these are photons, just like light, except of much higher energy, typically from several keV to several MeV. X-Rays and gamma rays are really the same thing, the difference is how they were produced. Depending on their energy, they can be stopped by a thin piece of aluminum foil, or they can penetrate several inches of lead.

http://www.blackcatsystems.com/GM/experiments/ex7.html

Fuentes de radiaciones ionizantes

Emisores alfa: http://www.iem-inc.com/toolen1.html

Emisores beta: http://www.iem-inc.com/toolen2.html

Emisores gama: http://www.iem-inc.com/toolen3.html

http://www.iem-inc.com/toolset.html

Todo sobre radiaciones ionizantes

Reloj con punteros y puntos luminosos. 1950’s Timex wrist watches

El radio se usó para fabricar pinturas luminosas. Por sus efectos nocivos para la salud ya no se usa.

http://en.wikipedia.org/wiki/Radium_Girls

Símbolo de peligro de radiación.

Biological effects of ionizing radiation

1. Cells experience DNA damage and are able to detect and repair the damage.

2. Cells experience DNA damage and are unable to repair the damage. These cells may go through the process of programmed cell death, or apoptosis, thus eliminating the potential genetic damage from the larger tissue.

3. Cells experience a nonlethal DNA mutation that is passed on to subsequent cell divisions. This mutation may contribute to the formation of a cancer.

http://en.wikipedia.org/wiki/Ionizing_radiation#Biological_effects_of_ionizing_radiation

http://en.wikipedia.org/wiki/Radiation_poisoning#Measuring_radiation_dosage

The rad is a unit of absorbed radiation dose defined in terms of the energy actually deposited in the tissue. One rad is an absorbed dose of 0.01 joules of energy per kilogram of tissue

The more recent SI unit is the gray (Gy), which is defined as 1 joule of deposited energy per kilogram of tissue. Thus one gray is equal to 100 rad.

To accurately assess the risk of radiation, the absorbed dose energy in rad is multiplied by the relative biological effectiveness (RBE) of the radiation to get the biological dose equivalent in rems. Rem stands for "Röntgen equivalent in man." In SI units, the absorbed dose energy in grays is multiplied by the same RBE to get a biological dose equivalent in sieverts (Sv). The sievert is equal to 100 rem.

U.S. Department of LaborOccupational Safety & Health Administration

US department of labor. Occupational safety & Health Administration www.osha.gov

http://nutec.jaea.go.jp/fnca/common/images/e-8-personal.pdf

Dosimetría. Medición de la energía absorbida por el cuerpo al exponerse a radiaciones ionizantes.

Tipos de dosímetros personales:

1. Cámaras de ionización.

2. Películas fotográficas.

3. Termoluminiscencia

Thermoluminescent dosimeters (TLD) utilizes the effect in somematerials which can store the energy of ionizing radiation in excited stateelectrons in the abnormality of lattices. When a Thermoluminescentelement is heated, its radioactive energy accumulated inside is emitted inthe form of light. By detecting this light, the dose can be measured.

Electrómetro

+

+ +

++

+ ++ +

Americio 241

El americio 241 emite radiaciones ionizantes alfa y gama

La radiación ioniza el aire que está entre el 241Am y el electrómetro, por lo tanto se hace conductor y descarga el electrómetro llevando una corriente eléctrica hacia la tierra.

Proportional counter

Townsend AvalancheIn a proportional counter, many electrons (10 - 10,000) reach the anode for each primary ion pair produced in the gas. The reason is that the electron of each primary ion pair creates further "secondary" ion pairs as it gets close to the anode. These secondary ion pairs are produced in what is called an avalanche

The pulses produced by a proportional counter provide two useful pieces of information: The number of pulses counted gives a measure of the intensity of the radiation . The size of the pulses counted gives a measure of the amount of primary ionization produced by the radiation in the chamber.

Gas-Flow Proportional Counter

Fill gasoutlet Fill gas

inlet

Detector

sample

Sample planchet

O-ring

(window- optional)

anode

Helio +etanol

34 eV/ion par

Geiger-Müller tube

VELLEMANGeiger-Muller Counter KitINTERMEDIATE KIT: Some previous knowledge of electronics. Good soldering techniques for medium dense boards. US$190.00

-100V

0V

+100V

+200V

+200V

Doblador de voltaje. Fuentes de alta tensión.

-100V

0V

+100V

+200V

-100V

0V +200V

+200V

+100V

+200V

+400V

+400V

+200V +200V

Fuentes de alta tensión.

+400V

+200V

+600V

0 V

Fuentes de alta tensión.

Agregue más etapas para más voltaje.

Circuito para contar los pulsos del tubo Geiger Muller

Arduino

Determinación de la tasa de detección de desintegraciones. Pulsos por unidad de tiempo, ratemeter.

Detector Geiger-Mueller con salida análoga

s 100 RC

s , t

VO

dtdV

CRVV OOi

0

RVVi

dtdV

CRVV OO

RCdt

VVdV

O

O

dtdV

CRVV OO

RCdt

VVVVd

O

O

t

t

O RCt

VV0

0ln

RCt

VVVO

ln RC

t

O eVVV

RC

t

O eVV 1

R1

1kohm

C2

100nFV1

1V

J1

Key = Space

Vi VO

Filtro pasa bajos

Vo

Vi

dtVVd

CRVV

RV iOiOi

12

R1

R2

C

CR

t

eVV 110

CR

t

i eRRRV

V 112

210

Filtro activo pasa-bajo

ii VVRRV 2

1 VV

RRV

ii

2

1

dtVVd

CRVRRRV iO

Oi

12

21

dtVVd

CRVV OO

1

dtVVd

CRVV iOO

1

dt

CRVVVVd

O

O

1

1

t

t

O CRt

VV01

0ln

V

RRRVi

2

21

dtVVd

CRVVRRV iO

iOi 1

2

1

VVdVVd OiO

Vi y V son constantes para t > 0

CR

t

O eV

VV1

Vi = 0 para t = 0

Vo

Vi

dtVVd

CRVV

RV iOiOi

12

R1

R2

C

CR

t

i eRRRV

V 112

210

Filtro activo pasa-bajo

0 100 200 300 400 500 600 700 800 900 10000

20

40

60

80

100

120

Vo, volt

Tiempo, microsegundos

Vo

ViR1

R2

C

211

2

21,0

RRC

t

i eRRRV

V

?

Filtro activo pasa-bajo

Filtro activo pasa-bajo de dos etapas

http://www.dspguide.com/pdfbook.htm

The Scientist and Engineer's Guide to Digital Signal ProcessingBy Steven W. Smith, Ph.D.

Chapter 6 - Convolution The Delta Function and Impulse Response Convolution The Input Side Algorithm The Output Side Algorithm The Sum of Weighted Inputs

-7 -6 -5 -4 -3 -2 -1 00

0.05

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0.45

Intervalo de tiempo

Fact

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e po

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aciò

n

RCti

RCti

ee

iFactori

/

/

)(

Kernel para filtro RC:

)()()( iFactoritinputtOutput

Filtro digital

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Fact

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Filtro digital

RCti

RCti

ee

iFactori

/

/

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Kernel para filtro RC:

)()()( iFactoritinputtOutput

-7 -6 -5 -4 -3 -2 -1 00

0.05

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RCti

RCti

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iFactori

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Kernel para filtro RC:

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Filtro digital

-7 -6 -5 -4 -3 -2 -1 00

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0.45

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Fact

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iFactori

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Kernel para filtro RC:

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Filtro digital

-7 -6 -5 -4 -3 -2 -1 00

0.05

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0.45

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RCti

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iFactori

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Kernel para filtro RC:

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Filtro digital

-7 -6 -5 -4 -3 -2 -1 00

0.05

0.1

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0.3

0.35

0.4

0.45

Intervalo de tiempo

Fact

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n

RCti

RCti

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iFactori

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Kernel para filtro RC:

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Filtro digital

-7 -6 -5 -4 -3 -2 -1 00

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0.1

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0.4

0.45

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iFactori

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Kernel para filtro RC:

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Filtro digital

-7 -6 -5 -4 -3 -2 -1 00

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n

RCti

RCti

ee

iFactori

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Kernel para filtro RC:

)()()( iFactoritinputtOutput

Filtro digital

-7 -6 -5 -4 -3 -2 -1 00

0.05

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iFactori

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Kernel para filtro RC:

)()()( iFactoritinputtOutput

Filtro digital

-7 -6 -5 -4 -3 -2 -1 00

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Kernel para filtro RC:

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Filtro digital

-7 -6 -5 -4 -3 -2 -1 00

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iFactori

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Kernel para filtro RC:

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Filtro digital

-7 -6 -5 -4 -3 -2 -1 00

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Kernel para filtro RC:

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Filtro digital

?

Input OutputFiltro1 Filtro2

Filtro1

Filtro1 +Filtro2

Constantes de tiempo = 100 ms

Constantes de tiempo = 100 ms

Constantes de tiempo = 100 ms. Pulsos aleatorios

Constantes de tiempo = 500 ms. Pulsos aleatorios

p=0.2 ms-1

p=0.2 ms-1

Conversor de PWM a Voltaje

5 V

5 V

5 V

200 s 5 s

5%

50%

95%

PWM 0 -100% Vout 0 - 5V

Salidas “análogas” de Arduino.

Contador de centelleo.

Cristal de NaI (Tl) en forma de pozo

Tubo foto multiplicador

http://mysite.du.edu/~etuttle/electron/elect41.htm

a 418 V, b 570 V, c 775 V

Radiation Physics and ChemistryVolume 76, Issue 7, July 2007, Pages 1156-1159

Single Electron Rresponse, SER, de un tubo fotomultiplicador

http://www.becker-hickl.de/pdf/ampmt.pdf

Amplificador lineal

Amplificador lineal

La onda de salida tiene un curso temporal más largo que el impulso de entrada.El onda de salida tiene una amplitud que es una función lineal de la energía del pulso de entrada

El onda de salida tiene una amplitud que es una función lineal de la energía del pulso de entrada

El onda de salida tiene una amplitud que es una función lineal de la energía del pulso de entrada

El onda de salida tiene una amplitud que es una función lineal de la energía del pulso de entrada

Comparador de voltaje

V3

Vout

V3 V+ Vout

.09

V+

-1 9 0

Comparador de voltaje

V3

Vout

V3 V+ Vout

.09

V+

-1 9 .09

Comparador de voltaje

V3

Vout

V3 V+ Vout

.09

V+

0 9 .09

Comparador de voltaje

V3

Vout

V3 V+ Vout

V+

.09 0 .09

Comparador de voltaje

V3

Vout

V3 V+ Vout

V+

.09 -9 0

Comparador de voltaje

V3, volt

Vout, volt

V3

Vout

V3 V+ Vout

V+

.09 -9 -.09

Comparador de voltaje

V3, volt

Vout, volt

V3

Vout

V3 V+ Vout

V+

1 -9 -.09

Comparador de voltaje

V3, volt

Vout, volt

V3

Vout

V3 V+ Vout

V+

0 -9 -.09

Comparador de voltaje

V3, volt

Vout, volt

V3

Vout

V3 V+ Vout

V+

-0.09 0 -.09

Comparador de voltaje

V3, volt

Vout, volt

V3

Vout

V3 V+ Vout

V+

-0.09 90

Comparador de voltaje

V3, volt

Vout, volt

V3

Vout

V3 V+ Vout

V+

-0.09 90.09

Comparador de voltaje

V3, volt

Vout, volt

V3

Vout

V3 V+ Vout

V+

-1 90.09

Comparador de voltaje

PMT

HV

Amplificador lineal

Comparador Contador

Nivel de comparación

Seleccionando los eventos de más grandes que un umbral de tección

PMT

HV

Amplificador lineal

Comparador

Contador

Nivel superior

Seleccionando los eventos comprendidos entre un nivel inferior y un nivel superior.

Comparador

Nivel inferior

Xor

PMT

HV

Amplificador lineal

Comparador

Contador 2 Nivel 3

Seleccionando los eventos comprendidos entre un nivel inferior y un nivel superior.

Comparador

Nivel 2

Xor

Comparador

Nivel 1

Contador 1Xor

Extender a n canales

Espectro gama del Cs 137 obtenido con un cristal de NaI con Tl.

Foto peak, 662 keV

http://en.wikipedia.org/wiki/Gamma_spectroscopy

Tabla de isótopos radiactivos:http://nucleardata.nuclear.lu.se/nucleardata/toi/nucSearch.asp

Tabla de isótopos radiactivos:http://nucleardata.nuclear.lu.se/nucleardata/toi/nucSearch.asp

Emisores gama: http://www.iem-inc.com/toolen3.html

http://www.uwm.edu/Dept/EHSRM/RAD/HANDOUT.pdf

UV

Visible, azul

http://www.uwm.edu/Dept/EHSRM/RAD/HANDOUT.pdf

ScintillatorTubo fotomultiplicador

Amplificador lineal

Discriminador (es)

Contador (es)

Fuente de radiación

Tubo fotomultiplicador

Amplificador linealSumador

Detector de coincidencia

Fuente alta tensión Fuente alta tensión

Tabla de isótopos radiactivos:http://nucleardata.nuclear.lu.se/nucleardata/toi/nucSearch.asp

3H 18.6 keV14C 156.4 keV35S 167 keV32P 1709 keV

http://www.orcbs.msu.edu/radiation/programs_guidelines/radmanual/appendix_carbon_14.pdf

http://www.orcbs.msu.edu/radiation/programs_guidelines/radmanual/appendix_hydrogen_3.pdf

http://www.orcbs.msu.edu/radiation/programs_guidelines/radmanual/appendix_phosphorus_32.pdf

http://www.orcbs.msu.edu/radiation/programs_guidelines/radmanual/appendix_sulfur_35.pdf

Tabla de emisores beta: http://www.iem-inc.com/toolen2.html