A spinthariscope () is a device for observing individual nuclear disintegrations caused by the interaction of

ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...

with a

phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or v ...

(see

radioluminescence Radioluminescence is the phenomenon by which light is produced in a material by bombardment with ionizing radiation such as alpha particles, beta particles, or gamma rays. Radioluminescence is used as a low level light source for night illumi ...

) or

scintillator A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbe ...

Invention

The spinthariscope was invented by

William Crookes Sir William Crookes (; 17 June 1832 – 4 April 1919) was a British chemist and physicist who attended the Royal College of Chemistry, now part of Imperial College London, and worked on spectroscopy. He was a pioneer of vacuum tubes, inventing t ...

in 1903. While observing the apparently uniform

fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...

on a

zinc sulfide Zinc sulfide (or zinc sulphide) is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite. Although this mineral is usually black because of various ...

screen created by the radioactive emissions (mostly

alpha radiation Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an at ...

) of a sample of

radium bromide Radium bromide is the bromide salt of radium, with the formula RaBr2. It is produced during the process of separating radium from uranium ore. This inorganic compound was discovered by Pierre and Marie Curie in 1898, and the discovery sparked a h ...

, he spilled some of the sample, and, owing to its extreme rarity and cost, he was eager to find and recover it. Upon inspecting the zinc sulfide screen under a

microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisi ...

, he noticed separate flashes of light created by individual

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be prod ...

collisions with the screen. Crookes took his discovery a step further and invented a device specifically intended to view these scintillations. It consisted of a small screen coated with zinc sulfide affixed to the end of a tube, with a tiny amount of

radium Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rat ...

salt suspended a short distance from the screen and a lens on the other end of the tube for viewing the screen. Crookes named his device from grc, σπινθήρ () "spark". Crookes debuted the spinthariscope at a meeting of the

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

, London on 15 May 1903.

Toy spinthariscopes

Spinthariscopes were quickly replaced with more accurate and

quantitative Quantitative may refer to: * Quantitative research, scientific investigation of quantitative properties * Quantitative analysis (disambiguation) * Quantitative verse, a metrical system in poetry * Statistics, also known as quantitative analysis ...

devices for measuring radiation in scientific experiments, but enjoyed a modest revival in the mid 20th century as children's educational toys. In 1947, Kix cereal offered a

Lone Ranger The Lone Ranger is a fictional masked former Texas Ranger who fought outlaws in the American Old West with his Native American friend Tonto. The character has been called an enduring icon of American culture. He first appeared in 1933 in ...

atomic bomb ring that contained a small one, in exchange for a box top and US$0.15 (). Spinthariscopes can still be bought today as instructional novelties, but they now use

americium Americium is a synthetic radioactive chemical element with the symbol Am and atomic number 95. It is a transuranic member of the actinide series, in the periodic table located under the lanthanide element europium, and thus by analogy was n ...

thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high ...

. Looking into a properly focused toy spinthariscope, one can see many flashes of light spread randomly across the screen. Almost all are circular, with a very bright pinpoint centre surrounded by a dimmer circle of emission.

In museums

The American History Museum of the Smithsonian has several spinthariscopes in its collections, and an article discussing them. However, none are currently on display.

References

{{Reflist

External links

Modern spinthariscopeElements of electricity: a practical discussion of the fundamental laws and ...
by

Robert Andrews Millikan Robert Andrews Millikan (March 22, 1868 – December 19, 1953) was an American experimental physicist honored with the Nobel Prize for Physics in 1923 for the measurement of the elementary electric charge and for his work on the photoelectric ...

, Edwin Sherwood Bishop, American Technical Society Particle detectors Radioactivity 1903 introductions Ionising radiation detectors Educational toys