That's fine for high levels of gamma from fallout in a nuclear attack, you say, but what about alpha radiation, either from fallout containing inhalation dangers due to Pu239 made from neutron capture in U238 in a nuclear explosion (which produces U239, decaying with a 23.5 minutes half life into Np239, which then decays with a 56 hours half life into Pu239), or in peacetime from Mr Putin's next attempt to assassinate someone using the alpha emitter Po210? Surely you need some expensive scintillation counter like the PCM5/1 with DP2R probe to reliably distinguish between alpha and beta/gamma, which I demonstrated on youtube?
Above: on 3 October 1960, James Robert Brown and Jack Sharpe filed US patent 3,126,482 for EMI Limited (the music publishers who also made and sold electronics, including Nuclear Enterprises Ltd, the Edinburgh based factory for radiation meters), “Radio-activity contamination monitor with discrimination means for alpha and beta radiation,” which was granted 24 March 1964. The brains of this invention is the ability to discriminate between 5 MeV alpha particles from typical fissile and fissionable fuel (uranium, plutonium, Am-241, etc.) and 0.5 MeV typical fission product beta particles. Alpha particles carry more energy and thereby cause larger flashes of light when they hit zinc sulphide, than beta particles (or Compton electrons released from atoms by gamma rays). All light flashes are detected in a photomultiplier probe fed with 850 volts (which is broken down into a range of potentials by a dynode chain of resistors, allowing electrons to be accelerated by successive multiplier plates in the probe). The box of tricks with the meter, batteries and loudspeaker contains 30 transistors (no ICs) which include two discriminator circuits for the amplified current pulses from the probe. Large current pulses, corresponding to particles of over 3 MeV, go into an alpha particle circuit and are assigned a "beeping pulse sound", while all smaller current pulses are assigned "clicks" (like an old fashioned geiger counter). Switched to alpha+beta, this instrument therefore allows the user to discriminate between alpha and beta radiation by the sense of hearing. Basically, the alpha detection circuit is like the "squelch" control in an old analogue radio transceiver: it cuts out (silences) all weak "noise" and is only triggered by strong signals. The scintillation probe is constantly sending out pulses of varying current. The alpha discriminator circuit simply ignores all pulses which are too small to be a beta particle. This makes the "alpha only" setting very useful in making the probe respond only to nearby contamination the clothing it is passing over. Older geiger probe based "contamination meters" proved useless in fallout areas because of the very high background count rate from beta and gamma emitters far away from the object the probe is placed near. These instruments were used in the British nuclear reactor industry to tell apart plutonium (alpha) from fission products (beta). The original 1960s instrument was the bulky box-like cream plastic PCM1 and PCM2 requiring eight D cells for power and demonstrated by Sean Connery in Dr No, but a more compact green coloured metal PCM3 soon followed, which during the 1970s evolved into the 1980s cream coloured PCM5 shown into the video which requires only two D cells (or rather, two rechargable AA cells placed in plastic A cell to D cell converters). After using the PCM5 for a few hours, you can clip the meter box by the handle into your belt and reliably assess contamination levels by hearing alone, with the probe in one hand. Various digital display versions are now available, including the LB 124 SCINT which combines the probe and analyser into one convenient handheld unit.
 |
| Turn the camera CCD chip in an old android based Samsung Mini smartphone into a reliable fallout radiation meter! |
 |
| Flashes occurring on the CCD image chip of the camera in a smartphone, like white dots of interference, are due to radiation. By calibrating a smartphone with a light-covered (black taped) camera lens using the Am-241 radioactive source from an ordinary spare household smoke detector, reliable measurements of radiation are possible using everyday household items. |
 |
| Above: scintillation counters use complex electron accelerator and multiplier vacuum tubes, but their role is simply to detect the flashes of light emitted by crystals which are disturbed by radiation. (Note that there are no heaters, and there is a "dynode chain" of resistors to break up an input of 850 volts or whatever into a range of different potentials in the probe for different plates. Therefore, the scintillation counter can be connected to the detector circuit box by just two conductors, e.g. simple coax cable.) Many materials emit light in this way. Even before the discovery in 1906 that gamma radiation from radium sources damages fast-dividing cancer cells, it has been discovered by Becquerel that ionizing radiation is like Roentgen's x-rays in having light-like properties on photographic plates (hence medical x-rays) and also makes zinc sulphide crystals glow. While zinc sulphide responds to alpha particles, ordinary perspex (a transparent plastic) is a good beta particle phosphor. By coating zinc sulphide on to anthracene, BC400, BC408, or other transparent plastic scintillation phosphor, you therefore get the "dual" phosphor which is the basis for the DP2 (50 cm^2 area) or DP6 (100 cm^2 area) alpha-beta "dual probe". The alpha side of the perspex is placed in direct contact with a thin light-proof mylar foil (metal coated plastic) which lets through over 50% of 5 MeV alpha particles, but stops light from entering. Beta particles can easily penetrate the thin zinc sulphide before causing light scintillations in the perspex. Gamma rays also produce Compton electrons with typically about half the energy of the original gamma ray, so those Compton electrons are similar to beta particles and can be detected in the same way. A large crystal of thallium doped sodium iodide gives much greater sensitivity for gamma radiation, however. The first scintillation counter was simply zinc sulphide fixed to the inside of a thin opaque metal foil at one end of a tube, allowing a glow of light to be seen when an alpha radiation emitter is placed beside the thin light-proof metal foil: you can see the glow by looking into the open end of the tube in a darkened room and with a lens you can even see the individual flashes, just like an expensive instrument. Geiger and Marsden used this manual approach to "counting" to prove Rutherford's nuclear atom theory by measuring the distribution of alpha particles scattered by a thin gold foil, until eye strain and boredom motivated Geiger to develop his electronic counter. |
 |
| Nuclear Enterprises (EMI) Portable Contamination Meter 5, PCM5, with scintillation probe in current use for decontamination of nuclear waste. |
 |
| EMI/Nuclear Enterprises radiation meters including two PCM1 alpha-beta discriminating meters, in the decontamination centre of the surprisingly hygienic but wicked Dr No, in the 1962 first James Bond movie. |
 |
| Sean Connery using PCM1 in the 007 film Dr No, 1962. |
 |
| Connery as 007 being carefully "frisked" by a DP2R dual alpha-beta probe, which is plugged into hand-slots and clothing monitor on the right, which has simultaneous dials for alpha and for beta contamination. This equipment was all bona fide EMI/Nuclear Enterprises stock, and the success of the realistic decontamination sequences of the film proved a marketing help for their sales of advanced radiation monitors. Although the PCM1 was fully transistorised and used only 1.5 volt D cells (twelve of them, providing 18 volts!), it was chunky and heavy. The PCM2 in 1965 differed only in offering a probe-clip to allow for one-handed operation. In 1968, the PCM3 was a streamlined metal cased version of half the weight, powered by a 9 volt battery. By 1980, this evolved into the lightweight PCM5, requiring only 3 volts (two D cells). |
Links to app download for the Rolf Deiter Klein smartphone gamma dose rate measurement:
https://play.google.com/store/apps/details?id=com.rdklein.radioactivity
Note that in an emergency where this app (or another type of radiation meter) is not available, a smartphone can be used as a basic indicator of strong radioactive contamination without such an app simply by blanking off the camera lens (to make it lightproof) with black tape or a taped over piece of foil or black paper, and opening the camera app to observe the rate of small white flashes (like old fashioned analogue TV interference) on the black screen background. Rolf Deiter Klein gives data tables here which convert the number of flashes per minute for different types of phones in to radiation levels: http://www.rdklein.de/html/radioa_data.html. For example, my old Samsung Galaxy Mini GT-S5570 has a calibration conversion factor of 27 flashes per minute for each microGray per hour of gamma radiation:
 |
| Different smartphone cameras have differing sensitivity to radiation: the Samsung Galaxy S4 gave 2 flashes per minute for 1 microGray/hour while the Samsung Galaxy Mini GT-S5570 have 27 flashes/minute for the same radiation level. In general, the newer and higher quality the smartphone camera, the more sensitive it is to radiation. (If you have a phone that has two cameras (front and back), you only need to cover up one of the cameras with tape to use as a radiation meter, leaving the other camera free to take pictures or video. The full list of data is found at: http://www.rdklein.de/html/radioa_data.html.) |
(For those unfamiliar with radiation units, 1 milliGray = 1000 microGray = 0.001 Joule/kg = 0.1 rad which for low LET gamma radiation with RBE =1 is equal to 0.1 rem or 1 milliSievert. For RBE =1, Grays and Sieverts are identical. For short term exposure over a few days or less, 10 Sieverts is the lethal dose, but spread out over 25 years in the bones of radium dial painters this dose was just the threshold dose needed to cause bone cancer, because of the repair by protein P53 to damaged DNA at low dose rates which is not possible at very high dose rates.)
His downloadable app simply counts the flashes and gives the conversion automatically. This is useful for very high radiation levels, but even then, without the app you can still get an idea of the relative strength of the radiation by the rate at which white flashes appear on the camera when the lens is properly covered. For example, if you take shelter in a concrete building, this will give an idea of the relative degree of fallout protection. It will make radiation visible, and provides a great civil defence use for old "network locked" smartphones (even without a SIM card, the WiFi network access allows radiation meter apps to be downloaded, installed and properly checked). This information about the use of smartphone cameras as nuclear radiation indicators should be included in modern civil defence handbooks. Being able to get an indication of harmful radiation using an everyday device like a smartphone should be useful information in a radiation emergency affecting a large area and thousands of people.
UPDATE: I have scanned in and uploaded to Internet Archive the full 1940 British Government handbook, Your Home as an Air Raid Shelter, with some extracts from other relevant documents appended. This information was fully tested and developed in World War II, and the Marxist attacks on civil defence facts have been responsible for the unnecessary injury and deaths of many thousands of people. Note particularly that I have also included (beginning at page 198) important extracts from the U.K. Civil Defence Training Memoranda 1-5, which explain how civil defence was a necessary part of the defeat of fascism in World War II. Note also that two of those five civil defence training memoranda were classified "Restricted", and those contained important civil defence information about civil defence throughout the world and also about the factual secret-classified U.S. Strategic Bombing Report 92 volume 2 on the real origin of the Hiroshima firestorm (obsolete, Japan-specific overturned charcoal cooking braziers in wooden homes of paper screens, not thermal flash as widely supposed by anti-civil defence exaggerations). My father was a Civil Defence Corps instructor in Colchester and found that most of the impressive evidence for making the case against hate-attacks on civil defence was classified "Restricted", and marked not for publication in newspapers. Therefore, proponents of civil defence in the Civil Defence Corps had their hands tied at the time, a tragedy when the unclassified publications (containing assertions without any evidence to back them up, due to secrecy) were held up for "ridicule" by bigoted, misinformed, ignorant MPs in the House of Commons during the 1960s.
The secret bureaucracy of the civil service in Britain prevented the proper evidence for civil defence from being used to discredit Marxist anti-civil defence propaganda by Jeremy Corbyn, Duncan Campbell, Phil Bolsover, and other folk. This bigoted, ill-informed, hate campaign of lies by ranting thugs has gone largely unopposed by "intelligent journalists" (mostly bigots and smug elitists) and thus has cost a great many lives in many wars since then. (Ignorant attacks on indoor shelters by the Cambridge Scientists Anti-War Group in the 1930s helped to kill thirty thousand in Britain before people like Lord Baker finally succeeded in getting the message through directly to Winston Churchill that indoor shelters can be made cheaply to save lives in comfort whereas outdoor shelters proved mostly too uncomfortable due to cold and flooding.) While the U.N. years "talking peace" over the Syrian civil war, simple relatively low cost countermeasures to reduce casualties from sarin and explosives are discounted in favour of an impractical, bigoted-propaganda based falsehood that the "only" options are either for a peace agreement/ceasefire or for an escalation to topple Assad. In reality, as with Saddam's threat, civil defence is a better proof tested and cheaper option to reduce casualties! Few editors in the media/government/U.N./disarmament lobby/CND want to launch a massive civil defence campaign to reduce casualties, they play politics while people suffer as a result.
UPDATE (15 April 2017): journalist Richard Madeley in 15 April 2017 Daily Express sensibly suggests: "Let's Send Gas Masks to Syria" (clip extract below):
The problems with this are that it is too limited a civil defence response, as we pointed out before on this blog, first most of the casualties are actually from bullets and debris from explosions (rather than gas, which produces only a small percentage of the casualties), and Syrian rebels tend to intercept aid supplies and get hold of any gas masks supplied, leaving the civilians unprotected. What is needed is a full WWII British civil defence type initiative, including the best proof-tested, low cost indoor sheltering techniques from bullets/shrapnel/blast debris, as well as gas proof rooms and masks. Sarin, for instance, is a danger in droplet form on the skin, so merely wearing a gas mask is not a complete solution, although it gives a high protection factor because any nerve gas is far more lethal to lung tissue than to the skin. Therefore, sheltered rooms - with window glass replaced by boarding, since explosives are often dropped ahead of gas, to break windows - is needed to avoid any risk of skin contamination by liquid droplet nerve agents. The same is necessary for protection against the dangers from blast, shrapnel and debris from explosions. On the other hand, well done Richard Madeley for daring to take the minority common sense viewpoint against the modern day equivalent of the nasty, "elitist", dogmatically political and fanatically anti-civil defence "Cambridge Scientists Anti-War Group" who ignore any evidence that contradicts them and sneer at proper criticisms.
Hamish de Bretton-Gordon, director of Doctors Under Fire, has now confirmed that Assad used sarin nerve gas, with the following evidence:
"It is now clear that the deadly nerve agent sarin, the same agent which the Assad regime used to kill up to 1,500 people in East Ghouta near Damascus in August 2013, was used in the chemical attack on Idlib last week. As the Union of Medical Care and Relief Organizations Chemical, Biological, Radiological and Nuclear (CBRN) adviser during the incident last week, I can confirm that samples smuggled out to Turkey have proved positive for sarin ...
"President Bashar al-Assad appears to use chemical weapons when he is in serious trouble or bogged down in a fight. The attack at East Ghouta saved the regime, as many believe it was about to be overrun by rebels in August 2013. Extensive use of chlorine in Aleppo in December 2016 broke an almost five-year siege, and the attack last week was to try to take Idlib, which has resisted throughout the civil war. President Trump's targeting of the air base from which the Syrian Air Force jets took off was a reasonable, proportionate and effective way to re-impose a chemical weapons taboo so effectively shattered in 2013 by international inaction over the Ghouta chemical attack.
"The numbers of those killed and injured (up to 100 people died and hundreds more were injured) suggest that a large amount of sarin was used, way beyond the capability of any al Qaeda groups who might have very small amounts of the agent. The most likely scenario is that Syrian jets dropped a number of bombs filled with the deadly agent.
"Conspiracy theories that these jets targeted Al Nusrah ammunition dumps that were full of sarin are unrealistic ... The Russians must have been aware that the Syrian regime has been using chemical weapons, in particular chlorine barrel bombs dropped from helicopters."
Update (4 May 2017): Ken Johnson and Professor Bryan Taylor, designer of Britain's first successful thermonuclear bomb, reveal why plastic foam was used for radiation coupling in the first successful (1.8 megatons) full scale thermonuclear British test of 1957
 |
| Click on photos for larger view: Ken Johnson, former Chief Scientist at AWE Aldermaston, holding a scale model of the full core insert of the first British fission weapon, Operation Hurricane, above a full scale replica nuclear weapon. Stills below show the 1952 Hurricane weapon implosion system design, and then the 1.8 megaton British thermonuclear test in 1957. |
 |
| Ken Johnson first detonating an unshaped explosive charge beside a metal plate to demonstrate poor effects: |
 |
| Ken Johnson's secret calculations of shock wave impulse for compressing cores more efficiently: |
 |
| Ken Johnson holding shaped explosive lens (in his left hand) which fits like lego into a hollow at the end of the explosive cylinder (in his right hand), the two explosives having different burning rates so as to focus the shock wave on a point (as proved below): |
 |
| Ken Johnson pointing out the far greater implosion impulse produced by the lens focus effect on solid metal immediately after the test (sharp metal edges). |
 |
| Bryan Taylor explaining that Britain's first successful 1.8 megaton test in 1957 used a spherical secondary state, necessitating low density plastic (polystyrene) in the radiation channel in order to allow the X-ray energy to uniformly arrive around the spherical stage and compress it to a focus. |
Ken Johnson, former Chief Scientist of Britain's Atomic Weapons Establishment in Aldermaston, Berkshire (AWE, originally called AWRE, Atomic Weapons Research Establishment), passed away on 28 September 2015, aged 79. However, before he died, Ken and Professor Bryan Taylor (Britain's radiation coupling thermonuclear warhead designer) and other colleagues made great efforts to show the previously secretive scientific basis of their work in Charles Colville's excellent documentary, broadcast on BBC4 last night (3 May 2017), Britain's Nuclear Bomb: The Inside Story.
Ken is filmed personally detonating two explosive charges (shaped and unshaped) beside a metal plate, to prove the effect of explosive lenses, cutting his finger in the process. Professor Bryan Taylor is then filmed taking a full two minutes (47-49 minutes in the 59 minutes film) explaining precisely why low density plastic foam was used to fill the radiation channel in the first fully successful, 1.8 megaton, British thermonuclear test of 1957:
"So we end up with something like this [see screenshot above]. There's an outer case in which there is a primary (a fission weapon) generally known as a Tom, and a secondary (the thermonuclear material), generally known as Dick. And the object is to get the [X-ray] radiation from the primary to surround Dick rather uniformly, so that it's compressed to a tight focus at the centre, where the temperature will rise and the thermonuclear reaction will start [after lithium is split by neutrons to give tritium].
"The question was, 'is it possible to get the radiation from the radiation from the trigger, Tom, to completely surround the secondary, Dick, in a more or less uniform fashion, before the radiation or the mechanical pressure [the debris shock wave from the exploding fission stage] has blown the whole thing apart? And to do this, the idea was we'd fill the space between Tom and Dick with a very low density material [like polystyrene], through which the [X-ray] radiation would pass rather rapidly. And to stop it all escaping and blowing everything apart, one makes the case of material of high electron density [uranium, or lead, a high-Z element], through which the radiation goes much more slowly. And the key to everything is, 'are these two speeds sufficiently different that it will do what one wants it to do?' ... Look, I was 27, and at that age, you can do anything!"
 |
| Prof. Bryan Taylor drawing spherical secondary being uniformly exposed to X-rays from all directions, for good compression. |
 |
| Bryan Taylor in 1957, Britain's original themonuclear weapon designer. |
A remarkable paragraph, providing complete clarity by the warhead designer responsible, on the role played by plastic foam in the British 1.8 megaton successful of a spherical secondary stage in 1957: Britain needed plastic foam to ensure that the spherical fusion stage (Dick) in its first thermonuclear weapons was uniformly compressed by X-rays. America didn't need do this in its first thermonuclear weapons, because it used a cylindrical shaped Dick, which did not suffer from the same problems of requiring such uniform compression: obviously, the compression of a cylinder needs to be symmetric in two dimensions only, not three which is the case for the British sphere (see quotation from Teller and Ulam's famous 9 March 1951 hydrogen bomb design report, LAMS-1225, below):
The American use of plastic foam in weapons with cylindrical stages, is entirely different: a layer of polystyrene is placed on the inside of the outer casing to act as a radiation mirror, re-radiating some X-ray energy back on the cylindrical metal pusher/ablation blanket surrounding the fusion fuel.
Richard Rhodes gives the details of the American early use of polystyrene inside early American thermonuclear weapons (having cylindrical, not spherical secondaries) on pages 492-3 of his 1995 book Dark Sun:
"X-rays from the fission primary would heat the plastic that lined the outer Sausage casing. The resulting hot plasma would re-radiate longer wavelength X-rays inward from all sides towards the thick uranium pusher. These X-rays would heat the surface of the pusher so hot that it would ablate: boil vaporized uranium off its outer surface. To every action there is an equal and opposite reaction ... accelerating the pusher shell inward and rapidly compressing [the fusion fuel]."
Rhodes backs this up on page 501 by quoting the former Los Alamos National Laboratory director Harold Agnew who observed thick polyethylene plastic sheets being nailed onto the lead lining of the 10 megaton Mike test's outer case:
"I remember seeing the guys hammer the big, thick polyethylene plastic pieces inside the casing. They hammered the plastic into the lead with copper nails."
This detail about the differing use of plastic inside American and British tests seems highly relevant to the later progress of nuclear weapons, away from the simple cylindrical secondaries of Edward Teller Richard Garwin (Garwin is the designer of Mike, see his 25 July 1951 Los Alamos report LAMD-746, Some Preliminary Indications of the Shape and Construction of a Sausage), and towards the spherical secondaries Britain successfully tested in 1957.
