1 Instrumentos para la detección de radiaciones Instrumentación 2008/clases/Radiaciones 2008 Rev OA martes, 18 de noviembre de 2008

2 Three types of radiation - Alpha, Beta, GammaThere 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.

3 Todo sobre radiaciones ionizantes Fuentes de radiaciones ionizantes Emisores alfa: Emisores beta: Emisores gama:

4 Reloj con punteros y puntos luminosos. 1950’s Timex wrist watchesEl radio se usó para fabricar pinturas luminosas. Por sus efectos nocivos para la salud ya no se usa.

5 Símbolo de peligro de radiación.

6 Biological effects of ionizing radiationCells experience DNA damage and are able to detect and repair the damage. 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. Cells experience a nonlethal DNA mutation that is passed on to subsequent cell divisions. This mutation may contribute to the formation of a cancer.

7 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.

8 U.S. Department of Labor Occupational Safety & Health Administration US department of labor. Occupational safety & Health Administration

9 Dosimetría. Medición de la energía absorbida por el cuerpo al exponerse a radiaciones ionizantes.Tipos de dosímetros personales: Cámaras de ionización. Películas fotográficas. Termoluminiscencia Thermoluminescent dosimeters (TLD) utilizes the effect in some materials which can store the energy of ionizing radiation in excited state electrons in the abnormality of lattices. When a Thermoluminescent element is heated, its radioactive energy accumulated inside is emitted in the form of light. By detecting this light, the dose can be measured.

10 + Electrómetro +

11 El americio 241 emite radiaciones ionizantes alfa y gamaLa 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.

12

13 Proportional counter Townsend AvalancheIn a proportional counter, many electrons ( ,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.

14 Gas-Flow Proportional CounterHelio +etanol Fill gas outlet Fill gas inlet anode (window- optional) Detector O-ring sample Sample planchet

15 34 eV/ion par

16 Geiger-Müller tube

17 VELLEMAN Geiger-Muller Counter Kit INTERMEDIATE KIT: Some previous knowledge of electronics. Good soldering techniques for medium dense boards. US$190.00

18 During the first negative half-cycle, D1 will be forward biased and will hold the right end of C1 at ground. Therefore C1 will charge to a voltage equal to the peak voltage (vp) of the transformer winding, with its left end being negative with respect to ground.  .

19 During the following positive half cycle, D1 will be reverse biased and therefore will not conduct current. The voltage on C1 will add to the transformer output voltage, so a voltage of 2vp will appear at the left end of D2. Since C2 is not yet charged at all, this will forward bias D2 and allow the voltage at the right end of C1 to be applied to the top of C2. C2 will charge as C1 discharges, until the two capacitors can no longer forward-bias D2. For the first positive half-cycle, the voltage on C2 will be equal to vp, and C1 will be completely discharged, so that all the voltage at the left end of D2 comes from the transformer winding. 

20 On the next negative half-cycle, C1 charges again to vp, through D1On the next negative half-cycle, C1 charges again to vp, through D1. If there is no load to discharge C2, its output will remain at +vp.  On the second positive half-cycle, C2 is still charged to +vp, while the voltage at the left end of D2 is again +2vp. Again, C1 transfers part of its charge to C2, but this time they stop when C2 is charged to a voltage of +1.5vp.  This action continues, cycle by cycle, with C1 being fully recharged to vp on each negative half cycle, and then charging C2 to a voltage halfway between its starting voltage and +2vp. C2 will never quite charge to +2vp, but it will come very close. 

21 Doblador de voltaje. Fuentes de alta tensión.

22 The first two sections, consisting of C1-D1 and C2-D2, still operate as a voltage doubler exactly as described above. With the addition of C3-D3, however, we see an additional effect. On the negative half-cycles when D1 is forward biased, D3 is also forward biased by the voltage on C2. Therefore C2 and C3 are effectively connected in parallel by D1 and D3, while D2 remains reverse biased and therefore does not conduct. As a consequence of this parallel connection, C2 shares its charge with C3 and both capacitors get charged towards a voltage of +2vp. On the positive half-cycles, D1 and D3 are off, and D2 is on. This allows C2 to recharge from C1, but it also connects C1 and C3 in series, thus increasing the output voltage even more than the voltage doubler circuit.

23 Fuentes de alta tensión.+400V +400V +200V +200V +200V +200V +200V 0V +200V 0V -100V +100V +100V -100V

24 Fuentes de alta tensión. Agregue más etapas para más voltaje.

25 Circuito para contar los pulsos del tubo Geiger MullerArduino

26 Determinación de la tasa de detección de desintegraciones.Pulsos por unidad de tiempo, ratemeter. Detector Geiger-Mueller con salida análoga

27 Filtro pasa bajos Vi VO VO

28 Filtro activo pasa-bajoVi R1 C R2 Vi y V son constantes para t > 0 Vi = 0 para t = 0

29 Filtro activo pasa-bajoVi R1 C R2 Vo, volt Tiempo, microsegundos

30 ? Filtro activo pasa-bajo Filtro activo pasa-bajo de dos etapas Vo Vi

31 The Scientist and Engineer's Guide to Digital Signal Processing By 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

32 Filtro digital Kernel para filtro RC:

33 Filtro digital Kernel para filtro RC:

34 Filtro digital Kernel para filtro RC:

35 Filtro digital Kernel para filtro RC:

36 Filtro digital Kernel para filtro RC:

37 Filtro digital Kernel para filtro RC:

38 Filtro digital Kernel para filtro RC:

39 Filtro digital Kernel para filtro RC:

40 Filtro digital Kernel para filtro RC:

41 Filtro digital Kernel para filtro RC:

42 Filtro digital Kernel para filtro RC:

43 Filtro digital Kernel para filtro RC:

44 ? Output Input Filtro1 Filtro2

45 Constantes de tiempo = 100 msFiltro1 +Filtro2 Filtro1

46 Constantes de tiempo = 100 ms

47 Constantes de tiempo = 100 ms. Pulsos aleatorios

48 Constantes de tiempo = 500 ms. Pulsos aleatoriosp=0.2 ms-1 p=0.2 ms-1

49 Salidas “análogas” de Arduino.5 V 5% 5 V 50% Conversor de PWM a Voltaje PWM % Vout 0 - 5V 5 s 200 s 5 V 95%

50 Contador de centelleo. Cristal de NaI (Tl) en forma de pozo Tubo foto multiplicador

51

52 a 418 V, b 570 V, c 775 V Radiation Physics and Chemistry Volume 76, Issue 7, July 2007, Pages

53 Single Electron Rresponse, SER, de un tubo fotomultiplicador

54 Amplificador lineal

55 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

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

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

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

59 Comparador de voltaje V+ Vout V3 V V Vout -1 0 9 .09

60 Comparador de voltaje V+ Vout V3 V V Vout -1 .09 9 .09

61 Comparador de voltaje V+ Vout V3 V V Vout .09 9 .09

62 Comparador de voltaje V+ Vout V3 V V Vout .09 .09

63 Comparador de voltaje V+ Vout V3 V V Vout .09 -9

64 Comparador de voltaje Vout, volt V+ Vout V3 V3, volt V3 V+ Vout .09-.09 -9

65 Comparador de voltaje Vout, volt V+ Vout V3 V3, volt V3 V+ Vout 1 -.09-9

66 Comparador de voltaje Vout, volt V+ Vout V3 V3, volt V3 V+ Vout -.09-.09 -9

67 Comparador de voltaje Vout, volt V+ Vout V3 V3, volt V3 V+ Vout -0.09-.09

68 Comparador de voltaje Vout, volt V+ Vout V3 V3, volt V3 V+ Vout -0.099

69 Comparador de voltaje Vout, volt V+ Vout V3 V3, volt V3 V+ Vout -0.09

70 Comparador de voltaje Vout, volt V+ Vout V3 V3, volt V3 V+ Vout -10.09 9

71 Comparador de voltaje

72 Seleccionando los eventos de más grandes que un umbral de tecciónHV Amplificador lineal Comparador Contador PMT Nivel de comparación

73 Seleccionando los eventos comprendidos entre un nivel inferior y un nivel superior.HV Comparador Xor Contador Amplificador lineal PMT Comparador Nivel inferior

74 Seleccionando los eventos comprendidos entre un nivel inferior y un nivel superior.Comparador HV Nivel 3 Xor Contador 2 Amplificador lineal PMT Comparador Xor Contador 1 Nivel 2 Comparador Nivel 1 Extender a n canales

75 Espectro gama del Cs 137 obtenido con un cristal de NaI con Tl.Foto peak, 662 keV Tabla de isótopos radiactivos:

76 Tabla de isótopos radiactivos: Emisores gama:

77

78 Visible, azul UV

79 Fuente de radiación Fuente alta tensión Fuente alta tensión Tubo fotomultiplicador Scintillator Tubo fotomultiplicador Amplificador lineal Sumador Amplificador lineal Detector de coincidencia Discriminador (es) Contador (es)

80

81 14C 156.4 keV 35S 167 keV 32P 1709 keV Tabla de isótopos radiactivos: 3H keV 14C keV 35S keV 32P keV Tabla de emisores beta: