Phys 586 Laboratory

Lab 7

Goal: In this lab you will make basic measurements using proportionaltubes.

Reading: Class notes and Knoll 173-177.

Lab:

1. Make gas connections to the cylindrical proportional tube. Set the flowrate to be about 10 bubbles/s for about 5 minutes, then reduce theflow rate to be about 1 bubble/s. You’ll want to watch the bubble rateduring the lab as the time constant to equilibriuum is several minutes.Write down the gas mixture used.

2. Connect the HV cable to the proportional tube. What polarity HVshould be used? What is the value of the series resistor? What is thepurpose of this resistor?

3. Terminate the proportional tube with a blocking capacitor and 1k ohmterminating resistor. Turn up the HV slowly until you can easily see asignal from the 137

Cs source using the analog oscilloscope. Be careful tomake the connection to the oscilloscope AFTER the blocking capacitor.Failure to do so can damage the oscilloscope channel (that’s why ourPhys 586 oscilloscope has only one channel). Make a quick sketch ofthe signal and record the pulse amplitude, rise time, and fall time.

4. Measure the pulse amplitude, rise time, and fall time for HV settings100 V above and 100 V below your nominal HV.

5. Repeat the process using 100 ohm, 10k ohm, and 100k ohm resistors.Explain these results. Note you do not have to make a sketch for eachresistor value.

6. Slowly raise the voltage but do not exceed 3kV. What happens to thepulses? Explain what is happening inside the proportional tube.

1

7. Make gas connections to the rectangular proportional tube. Set theflow rate to be about 10 bubbles/s for about 5 minutes, then reducethe flow rate to be about 1 bubble/s. Set the HV to be 2500 V.

8. Look over the preamplifier circuit. It consists of a transimpedanceamplifier and a transconductance amplifier. Explain these terms.

9. Sketch the signal at the output of the preamplifier and the output ofthe amplifier/shaper using a gamma source. Record the amplitude,rise time, and fall time of each. Terminate each with 50 ohms into theoscilloscope. Again, these should be done quickly.

10. Record the gain and other settings you used for the amplifier/shaper.

11. Collect pulse height data with the 137Cs source.

12. Take pulse height data with the x-ray source using Cu, Rb, Mo, and Agtargets. A five minute run for each should give good statistics. Whatare the characteristic x-ray energies for these targets? A list can befound at http://www.kayelaby.npl.co.uk/atomic and nuclear physics/4 2/4 2 1.html.Record the pulse height mean and width for each target.

13. Make a linearity plot of your pulse height data. Comment on theresults.

14. Make an energy resolution plot of your pulse height data. Normallyone evaluates the energy resolution using the 5.9 keV x-ray from 55

Fe

but that source is not available to us. Use your energy resolution datato quote an energy resolution at 5.9 keV. Compare with an estimateusing Table 6.2 in Knoll. Comment on your results.

In your lab writeup, please include:

1. Write down the gas mixture and HV used.

2. Table of pulse height, rise time, and fall time for different resistor values.Comment on these results.

3. Explain the pulses seen when the HV is raised several hundred voltsabove nominal.

2

4. Gain and other parameters of the amplifier/shaper.

5. Sketch of the signal from the preamplifier and the amplifier.

6. Explain what transimpedance and transconductance amplifiers do.

7. Plots of pulse height spectra for the 137Cs source and Cu, Rb, Mo, and

Ag x-ray sources.

8. Comment on the pulse height spectra for 137Cs.

9. Table of x-ray energies and measured pulse heights and widths.

10. Linearity plot using the x-ray sources and comment on the result.

11. Energy resolution plot using the x-ray sources and comment on theresult.

12. Estimate the energy resolution at 5.9 keV and compare to the expectedvalue. Also, is this energy resolution larger or smaller compared to thatfor the NaI detector?

3

Transconductance 1

TransconductanceTransconductance, also known as mutual conductance, is a property ofcertain electronic components. Conductance is the reciprocal of resistance;transconductance, meanwhile, is the ratio of the current change at the outputport to the voltage change at the input port. It is written as gm. For directcurrent, transconductance is defined as follows:

For small signal alternating current, the definition is simpler:

TerminologyTransconductance is a contraction of transfer conductance. The old unit of conductance, the mho (ohm spelledbackwards), was replaced by the SI unit, the siemens, with the symbol S (1 siemens = 1 ampere per volt).

TransresistanceTransresistance, infrequently referred to as mutual resistance, is the dual of transconductance. The term is acontraction of transfer resistance. It refers to the ratio between a change of the voltage at two output points and arelated change of current through two input points, and is notated as rm:

The SI unit for transresistance is simply the ohm, as in resistance.

Devices

Vacuum tubesFor vacuum tubes, transconductance is defined as the change in the plate(anode)/cathode current divided by thecorresponding change in the grid/cathode voltage, with a constant plate(anode)/cathode voltage. Typical values of gmfor a small-signal vacuum tube are 1 to 10 millisiemens. It is one of the three 'constants' of a vacuum tube, the othertwo being its gain μ and plate resistance rp or ra. The Van der Bijl equation defines their relation as follows:

[1]

Transconductance 2

Field effect transistorsSimilarly, in field effect transistors, and MOSFETs in particular, transconductance is the change in the drain currentdivided by the small change in the gate/source voltage with a constant drain/source voltage. Typical values of gm fora small-signal field effect transistor are 1 to 30 millisiemens.Using the Shichman–Hodges model, the transconductance for the MOSFET can be expressed as (see MOSFETarticle):

where ID is the DC drain current at the bias point, and Veff is the effective voltage, which is the difference betweenthe bias point gate–source voltage and the threshold voltage (i.e., Veff := VGS - Vth).[2]:p. 395, Eq. (5.45) The effectivevoltage (otherwise known as the overdrive voltage) is customarily chosen at about 70–200 mV for the 65 nmtechnology node (ID ≈ 1.13 mA/μm of width) for a gm of 11–32 mS/μm.[3]:p. 300, Table 9.2[4]:p. 15, §0127

Additionally, the transconductance for the junction FET is given by , where VP is the

pinchoff voltage and IDSS is the maximum drain current.Traditionally, the transconductance for the FET and MOSFET as given in the equations above is derived from thetransfer equation of each device, using calculus. However, Cartwright [5] has shown that this can be done withoutcalculus.In datasheets, the transconductance is often called transfer admittance.[6]

Bipolar transistorsThe gm of bipolar small-signal transistors varies widely, being proportional to the collector current. It has a typicalrange of 1 to 400 millisiemens. The input voltage change is applied between the base/emitter and the output is thechange in collector current flowing between the collector/emitter with a constant collector/emitter voltage.The transconductance for the bipolar transistor can be expressed as

where IC = DC collector current at the Q-point, and VT = thermal voltage, typically about 26 mV at roomtemperature. For a typical current of 10 mA, gm ≈ 385 mS.

Amplifiers

Transconductance amplifiersA transconductance amplifier (gm amplifier) puts out a current proportional to its input voltage. In networkanalysis, the transconductance amplifier is defined as a voltage controlled current source (VCCS) . It is commonto see these amplifiers installed in a cascode configuration, which improves the frequency response.

Transresistance amplifiersA transresistance amplifier outputs a voltage proportional to its input current. The transresistance amplifier is oftenreferred to as a transimpedance amplifier, especially by semiconductor manufacturers.The term for a transresistance amplifier in network analysis is current controlled voltage source (CCVS) .A basic inverting transresistance amplifier can be built from an operational amplifier and a single resistor. Simplyconnect the resistor between the output and the inverting input of the operational amplifier and connect thenon-inverting input to ground. The output voltage will then be proportional to the input current at the inverting input,decreasing with increasing input current and vice versa.

Transconductance 3

Specialist chip transresistance (transimpedance) amplifiers are widely used for amplifying the signal current fromphoto diodes at the receiving end of ultra high speed fibre optic links. The MAX3724 and MAX3725 [7] areexamples.

Operational transconductance amplifiersMany semiconductor manufacturers produce chips (integrated circuits) which can function as transconductanceamplifiers. These are frequently described as operational transconductance amplifiers (OTAs) and normally havean input to allow the transconductance to be controlled. Examples are: CA3080 [8], MAX 435 [9], MAX 436 [9],LM13700 [10], OPA860 [11], OPA861 [12].

References[1][1] Blencowe, Merlin (2009). "Designing Tube Amplifiers for Guitar and Bass".[2] Sedra, A.S.; Smith, K.C. (1998), Microelectronic Circuits (http:/ / worldcat. org/ isbn/ 0-19-514251-9) (Fourth ed.), New York: Oxford

University Press, ISBN 0-19-511663-1,[3] Baker, R. Jacob (2010), CMOS Circuit Design, Layout, and Simulation, Third Edition, (http:/ / worldcat. org/ isbn/ 978-0-470-88132-3), New

York: Wiley-IEEE, ISBN 978-0-470-88132-3,[4] Sansen, W.M.C. (2006), Analog Design Essentials (http:/ / worldcat. org/ isbn/ 0387257462), Dordrecht: Springer, ISBN 0-387-25746-2,[5] Cartwright, Kenneth V (Fall 2009), "Derivation of the Exact Transconductance of a FET without Calculus" (http:/ / technologyinterface.

nmsu. edu/ Fall09/ Fall09/ 011. pdf), The Technology Interface Journal 10 (1): 7 pages,[6] http:/ / www. ius. edu. ba/ sselman/ EE301/ CH9. pdf[7] http:/ / pdfserv. maxim-ic. com/ en/ ds/ MAX3724-MAX3725. pdf[8] http:/ / www. intersil. com/ data/ fn/ fn475. pdf[9] http:/ / pdfserv. maxim-ic. com/ en/ ds/ MAX435-MAX436. pdf[10] http:/ / www. national. com/ ds/ LM/ LM13700. pdf[11] http:/ / focus. ti. com/ lit/ ds/ symlink/ opa860. pdf[12] http:/ / focus. ti. com/ lit/ ds/ symlink/ opa861. pdf

Further exploration• Horowitz, Paul & Hill, Winfield (1989), The Art of Electronics, Cambridge University Press,

ISBN 0-521-37095-7• Transconductance (http:/ / searchsmb. techtarget. com/ sDefinition/ 0,290660,sid44_gci214200,00. html) —

SearchSMB.com Definitions• Transconductance in audio amplifiers: article by David Wright of Pure Music (http:/ / www. beauhorn. com/

articles/ TC_amps_& _SD_horns. html)

Article Sources and Contributors 4

Article Sources and ContributorsTransconductance  Source: http://en.wikipedia.org/w/index.php?oldid=540873857  Contributors: Akulosophy, AlexHe34, Anoneditor, Aulis Eskola, Brews ohare, CPES, DekuDekuplex,DexDor, Evaluist, Fantumphool, FredK, Gene Nygaard, Glenn, Hooperbloob, Icairns, Kdf1252, Light current, Matt B., Nocal, Oli Filth, Omegatron, Rogerbrent, Salsb, Shivsagardharam,TedPavlic, That Guy, From That Show!, The Anome, Toffile, Trickoftheeye, Vanished user 05, Wolfmankurd, Пика Пика, 53 anonymous edits

Image Sources, Licenses and ContributorsImage:Image for Transconductance.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Image_for_Transconductance.svg  License: GNU Free Documentation License  Contributors:Wolfmankurd

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10

APPENDIX A

Details of the Variable Energy X-ray Source

Variable energy X-ray source code AMC.2084

SPECIFICATION

Construction: A compact assembly containing a sealed ceramic primary source which excites characteristic X-rays from six different targets in turn. The annular primary source surrounds the X-ray emission aperture in the fixed part of the stainless steel assembly and the targets are mounted on a rotary holder. Each target can be presented to the primary source in turn and the characteristic X-rays from the target are emitted through the 4mm diameter aperture.

Primary source: A 10mCi americium-241 source,consisting of a ceramic active component in a welded stainless steel capsule, withintegral tungsten alloy rear shielding.

X-ray emission:

Target selected Energy (keV)(1)

Kα

Energy (keV) (1)

Kβ

Photon yield(2)

(photons/s per steradian)

Cu 8.04 8.91 2,500 Rb 13.37 14.97 8,800 Mo 17.44 19.63 24,000 Ag 22.10 24.99 38,000 Ba 32.06 36.55 46,000 Tb 44.23 50.65 76,000

Notes: (1) weighted mean energies (2) the photon yield has been determined using a high resolution Si (Li) X-ray spectrometer; the photon output is highly collimated limiting emission to 0.5 steradians.

Atomic number and

element

K-series L-series

K edge

KNIII KMIII KMII KLIII KLII LI

edge

LINIII LIMIII LIMII LII

edge

LIINIV LIIMIV LIII

edge

LIIINV LIIIMV

Kβ2 Kβ1 Kβ3 Kα1 Kα2 Lγ3 Lβ3 Lβ4 Lγ1 Lβ1 Lβ2 Lα1

Intensity — 2–5 ~20 ~10 100 50–53 — ~5 50–35 20 — ~5 ~50 — ~5 ~90

4 Be 0.115 0.109 0.006 5 B 0.188 0.183 0.005 6 C 0.282 0.277 0.005 7 N 0.397 0.393 0.004 8 O 0.533 0.525 0.008 9 F 0.692 0.677 0.015 10 Ne 0.874 0.858 0.848 0.026 11 Na 1.080 1.071 1.041 0.039 12 Mg 1.309 1.302 1.253 0.062 0.056 13 Al 1.562 1.557 1.487 1.486 0.087 0.076 0.075 14 Si 1.840 1.836 1.740 1.739 0.118 0.101 0.100 15 P 2.143 2.139 2.014 2.013 0.153 0.130 0.129 16 S 2.471 2.464 2.308 2.307 0.193 0.164 0.163 17 Cl 2.824 2.816 2.622 2.620 0.237 0.204 0.202 18 Ar 3.203 3.190 2.958 2.956 0.286 0.247 0.245 19 K 3.607 3.590 3.314 3.311 0.340 0.296 0.293 20 Ca 4.034 4.013 3.692 3.688 0.403 0.346 0.342 21 Sc 4.486 4.461 4.090 4.086 0.462 0.400 0.400 0.396 0.39 22 Ti 4.965 4.932 4.511 4.505 0.529 0.460 0.458 0.454 0.45 23 V 5.463 5.427 4.952 4.944 0.626 0.585 0.519 0.519 0.511 0.51 24 Cr 5.987 5.947 5.415 5.405 0.694 0.654 0.582 0.583 0.572 0.57 25 Mn 6.537 6.490 5.899 5.888 0.768 0.721 0.649 0.649 0.638 0.63 26 Fe 7.112 7.058 6.404 6.391 0.846 0.792 0.721 0.719 0.708 0.70 27 Co 7.712 7.649 6.930 6.915 0.929 0.870 0.797 0.791 0.782 0.77 28 Ni 8.339 8.265 7.478 7.461 1.016 0.941 0.878 0.869 0.861 0.85 29 Cu 8.993 8.905 8.903 8.048 8.028 1.109 1.023 1.019 0.965 0.950 0.945 0.93 30 Zn 9.673 9.6581 9.572 9.567 8.639 8.616 1.208 1.107 1.102 1.057 1.035 1.034 1.01 31 Ga 10.386 10.3661 10.271 10.261 9.252 9.231 1.316 1.197 1.191 1.155 1.125 1.134 1.09 32 Ge 11.115 11.1011 10.983 10.978 9.887 9.856 1.426 1.294 1.289 1.259 1.218 1.228 1.18 33 As 11.877 11.8641 11.727 11.721 10.544 10.509 1.536 1.386 1.380 1.368 1.316 1.333 1.28 34 Se 12.666 12.6521 12.496 12.489 11.222 11.181 1.662 1.492 1.485 1.485 1.419 1.444 1.37 35 Br 13.483 13.4701 13.292 13.285 11.924 11.878 1.791 1.600 1.593 1.605 1.523 1.559 1.48 36 Kr 14.330 14.3151 14.113 14.105 12.650 12.598 1.923 1.706 1.698 1.732 1.637 1.680 1.58 37 Rb 15.202 15.1851 14.962 14.952 13.396 13.336 2.067 2.0512 1.827 1.817 1.866 1.752 1.806 1.694 38 Sr 16.106 16.0851 15.836 15.826 14.166 14.098 2.217 2.1972 1.947 1.937 2.008 1.872 1.940 1.806

39 Y 17.037 17.0151 16.737 16.725 14.958 14.882 2.372 2.3472 2.072 2.060 2.155 1.996 2.079 1.923

40 Zr 17.997 17.9631 17.662 17.649 15.770 15.692 2.535 2.5032 2.200 2.187 2.305 2.292 2.118 2.227 2.215 2.043 41 Nb 18.985 18.9471 18.623 18.606 16.615 16.521 2.698 2.6602 2.336 2.319 2.464 2.449 2.257 2.370 2.357 2.166 42 Mo 20.002 19.960 19.608 19.590 17.479 17.374 2.867 2.8252 2.473 2.455 2.628 2.611 2.396 2.523 2.508 2.295 43 Tc 21.048 21.002 20.619 20.599 18.367 18.251 3.047 3.0012 2.618 2.598 2.797 2.778 2.537 2.681 2.664 2.424 44 Ru 22.123 22.072 21.656 21.637 19.279 19.150 3.230 3.1792 2.763 2.744 2.973 2.952 2.683 2.844 2.825 2.556 45 Rh 23.229 23.173 22.723 22.698 20.216 20.073 3.421 3.3652 2.915 2.890 3.156 3.132 2.835 3.013 2.992 2.698

X-ray adsorption edges and characteristic X-ray line energies (keV)

46 Pd 24.365 24.303 23.819 23.792 21.178 21.021 3.619 3.557 3.073 3.046 3.344 3.318 2.990 3.187 3.163 2.838 47 Ag 25.531 25.463 24.943 24.912 22.163 21.991 3.822 3.754 3.234 3.203 3.540 3.511 3.151 3.368 3.342 2.985 48 Cd 26.727 26.653 26.095 26.061 23.173 22.985 4.034 3.960 3.402 3.368 3.742 3.710 3.319 3.554 3.525 3.134 49 In 27.953 27.872 27.275 27.237 24.209 24.002 4.250 4.169 3.572 3.534 3.951 3.915 3.487 3.744 3.712 3.288 50 Sn 29.211 29.122 28.491 28.439 25.272 25.044 4.475 4.377 3.750 3.703 4.167 4.127 3.661 3.939 3.903 3.442

Intensity — 5–15 ~20 ~10 100 53–65 — ~5 35–20 20 — 5–25 100 — 5–20 ~90

Proportional counter 1

Proportional counterThe proportional counter is a type of gaseous ionization detector device used to count particles of ionizingradiation. A key feature is its ability to measure the energy of incident radiation, and it is widely used wherediscrimination between radiation types is required, such as between alpha and beta particles.

Plot of variation of ion pair current against applied voltage for a wire cylindergaseous radiation detector.

A proportional counter uses a combinationof the mechanisms of a Geiger-Muller tubeand an ionisation chamber, and operates inan intermediate voltage region betweenthese. Considering a gas-filled chamber witha wire anode, if the field strengtheverywhere in the volume is below a criticalvalue, Townsend avalanches do not occur atall, and the detector operates as anionization chamber. If the applied voltage istoo high, complete ionisation of the fill gasoccurs with almost each ion pair and thedetector operates as a Geiger-Müllercounter, with the consequent loss of incidentparticle energy information. Theaccompanying plot shows the proportionaloperating region for a co-axial cylinderarrangement.

Operation

The generation of discrete Townsend avalanches in a proportional counter.

In a proportional counter the fill gas of thechamber is an inert gas which is ionised byincident radiation, and a quench gas toensure each pulse discharge terminates; acommon mixture is 90% argon, 10%methane, known as P-10. An ionizingparticle entering the gas collides with amolecule of the inert gas and ionises it toproduce an electron and a positively chargedatom, commonly known as an "ion pair". Asthe charged particle travels through thechamber it leaves a trail of ion pairs alongits trajectory, the number of which isproportional to the energy of the particle if it is fully stopped within the gas. Typically a 1 MeV stopped particle willcreate about 30,000 ion pairs.[1]

Proportional counter 2

Plot of electric field strength at the anode,showing boundary of avalanche region.

The chamber geometry and the applied voltage is such that in most ofthe chamber the electric field strength is low and the chamber acts asan ion chamber. However, the field is strong enough to preventre-combination of the ion pairs and causes positive ions to drifttowards the cathode and electrons towards the anode. This is the "iondrift" region. In the immediate vicinity of the anode wire, the fieldstrength becomes large enough to produce Townsend avalanches. Thisavalanche region occurs only fractions of a millimeter from the anodewire, which itself is of a very small diameter. The purpose of this is touse the multiplication effect of the avalanche produced by each ionpair. This is the "avalanche" region.

A key design goal is that each original ionising event due to incident radiation produces only one avalanche. This isto ensure proportionality between the number of original events and the total ion current. For this reason the appliedvoltage, the geometry of the chamber and the diameter of the anode wire are critical to ensure proportional operation.If avalanches start to self-multiply due to UV photons as they do in a Geiger-Muller tube, then the counter enters aregion of "limited proportionality" until at a higher applied voltage the Geiger discharge mechanism occurs withcomplete ionisation of the gas enveloping the anode wire and consequent loss of particle energy information.Therefore it can be said that the proportional counter has the key design feature of two distinct ionisation regions:1.1. Ion drift region: in the outer volume of the chamber - creation of number ion pairs proportional to incident

radiation energy.2.2. Avalanche region: in the immediate vicinity of the anode - Charge amplification of ion pair currents, while

maintaining localised avalanches.The process of charge amplification greatly improves the signal-to-noise ratio of the detector and reduces thesubsequent electronic amplification required.In summary, the proportional counter is an ingenious combination of two ionisation mechanisms in the one chamberwhich finds wide practical use.

Applications

SpectroscopyThe proportionality between the energy of the charged particle travelling through the chamber and the total chargecreated makes proportional counters useful for charged particle spectroscopy. By measuring the total charge (timeintegral of the electric current) between the electrodes, we can determine the particle's kinetic energy because thenumber of ion pairs created by the incident ionizing charged particle is proportional to its energy. The energyresolution of a proportional counter, however, is limited because both the initial ionization event and the subsequent'multiplication' event are subject to statistical fluctuations characterised by a standard deviation equal to the squareroot of the average number formed. However in practice these are not as great as would be predicted due to the effectof the empirical Fano factor which reduces these fluctuations.[1] In the case of argon, this is experimentally about0.2.

Proportional counter 3

Photon detectionProportional counters are also useful for detection of high energy photons, such as gamma-rays, provided these canpenetrate the entrance window. They are also used for the detection of X-rays to below 10 Kev energy levels, usingthin walled tubes operating at or around atmospheric pressure.

Radioactive contamination detectionProportional counters are used extensively as large area detectors to check for radioactive contamination onpersonnel, tools and items of clothing. This is normally in the form of installed instruments because of thedifficulties of providing portable gas supplies for hand-held devices. In this particular application they areflat-chambered multi-wire detectors for alpha and beta detection. They have a large area detection window madefrom such as metallised mylar to form part of the cathode, and an anode wire routed in a convoluted manner tointersperse fully within the gas fill area of the detector. These detectors are able to discriminate between alpha andbeta radiation and have a high efficiency for beta, but lower for alpha. The efficiency reduction for alpha is due tothe attenuation effect of the entry window, though distance from the surface being checked also has a significanteffect.They operate at very slight positive pressure above ambient atmospheric pressure. The gas can be sealed in thechamber, or can be changed continuously, in which case they are known as "gas-flow proportional counters". Gasflow types have the advantage that they will tolerate small holes in the mylar screen which can occur in use, but theydo require a continuous gas supply.

Guidance on application useIn the United Kingdom the HSE has issued a user guidance note on selecting the correct radiation measurementinstrument for the application concerned [2]. This covers all radiation instrument technologies, and is a usefulcomparative guide to the use of proportional counters.

External articlesPatents• U.S. Patent 3,092,747 [3], S. Fine, "Proportional counter"• U.S. Patent 2,499,830 [4], E. W. Molloy, "Air proportional counter"

References• Glenn F Knoll. Radiation Detection and Measurement, third edition 2000. John Wiley and sons, ISBN

0-471-07338-5.• G.Charpak and F.Sauli; Sauli, F (1984). "High-resolution Electronic Particle Detectors". Annual review of

Nuclear Science (Annual Reviews Inc.) 34 (1): 285–350. Bibcode 1984ARNPS..34..285C [5].doi:10.1146/annurev.ns.34.120184.001441 [6].

• E. Mathieson, Induced charge distributions in proportional detectors, http:/ / www. inst. bnl. gov/ programs/gasnobledet/ publications/ Mathieson's_Book. pdf

[1][1] Glenn F Knoll. Radiation Detection and Measurement, third edition 2000. John Wiley and sons, ISBN 0-471-07338-5.[2] http:/ / www. hse. gov. uk/ pubns/ irp7. pdf[3] http:/ / www. google. com/ patents?vid=3092747[4] http:/ / www. google. com/ patents?vid=2499830[5] http:/ / adsabs. harvard. edu/ abs/ 1984ARNPS. . 34. . 285C[6] http:/ / dx. doi. org/ 10. 1146%2Fannurev. ns. 34. 120184. 001441

Article Sources and Contributors 4

Article Sources and ContributorsProportional counter  Source: http://en.wikipedia.org/w/index.php?oldid=540298590  Contributors: Audiovideo, B8horpet, Blu3d, Carrionluggage, Cdang, Dougsim, Dschlue1, Forteblast,Gbleem, Goudzovski, Guidod, Heron, Ileresolu, Jac64, JanKorger, KP-Adhikari, KazakhPol, Matt Whyndham, Mbell, Mccreary, Mrmrbeaniepiece, Mumby, Nokta strigo, Plugwash, Reinholz,Sanders muc, Sergio.ballestrero, Spike Wilbury, Tevatron, WISo, Wtshymanski, 24 anonymous edits

Image Sources, Licenses and ContributorsFile:Detector regions.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Detector_regions.gif  License: Creative Commons Attribution-Sharealike 3.0  Contributors: User:DougsimFile:Proportional counter avalanches.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Proportional_counter_avalanches.jpg  License: Creative Commons Attribution-Sharealike 3.0 Contributors: User:DougsimFile:Gas counter anode electric field.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Gas_counter_anode_electric_field.gif  License: Creative Commons Attribution-Sharealike 3.0 Contributors: User:Dougsim

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