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Re: [TCML] Homemade Crookes Tube?

HI Everyone
Let me try to put this to rest, crookes tube produce cathode Rays, and unless they reflect of of metal like the railway tube or Maltese cross tube they produce very little soft X Rays at all. I have a large collection of Crookes and geissler tube and have check them for X Rays many time and unless they bounce off metal you have nothing to worry about. Even at 10000 volt the railway and Maltese cross tube will produce soft X rays but not enough to hurt you. This is my Flickr site and you can see picture of some of them and a video 
of them.
https://www.flickr.com/photos/91001059@N08/
the tube in question will not produce harmful X rays.
The information below may help too.
Alton
W5ALS
A *Crookes tube* is an early experimental electrical discharge tube <http://en.wikipedia.org/wiki/Discharge_tube>, with partial vacuum, invented by English physicist William Crookes <http://en.wikipedia.org/wiki/William_Crookes>^[1] <http://en.wikipedia.org/wiki/Crookes_tube#cite_note-1> and others around 1869-1875,^[2] <http://en.wikipedia.org/wiki/Crookes_tube#cite_note-2> in which cathode rays <http://en.wikipedia.org/wiki/Cathode_ray>, streams of electrons <http://en.wikipedia.org/wiki/Electron>, were discovered.^[3] <http://en.wikipedia.org/wiki/Crookes_tube#cite_note-3>
Developed from the earlier Geissler tube <http://en.wikipedia.org/wiki/Geissler_tube>, the Crookes tube consists of a partially evacuated <http://en.wikipedia.org/wiki/Vacuum> glass container of various shapes, with two metal electrodes <http://en.wikipedia.org/wiki/Electrodes>, the cathode <http://en.wikipedia.org/wiki/Cathode> and the anode <http://en.wikipedia.org/wiki/Anode>, one at either end. When a high voltage <http://en.wikipedia.org/wiki/High_voltage> is applied between the electrodes, cathode rays <http://en.wikipedia.org/wiki/Cathode_ray> (electrons <http://en.wikipedia.org/wiki/Electron>) are projected in straight lines from the cathode. It was used by Crookes, Johann Hittorf <http://en.wikipedia.org/wiki/Johann_Hittorf>, Julius Plücker <http://en.wikipedia.org/wiki/Julius_Pl%C3%BCcker>, Eugen Goldstein <http://en.wikipedia.org/wiki/Eugen_Goldstein>, Heinrich Hertz <http://en.wikipedia.org/wiki/Heinrich_Hertz>, Philipp Lenard <http://en.wikipedia.org/wiki/Philipp_Lenard> and others to discover the properties of cathode rays, culminating in J.J. Thomson <http://en.wikipedia.org/wiki/J.J._Thomson>'s 1897 identification of cathode rays as negatively charged particles, which were later named /electrons <http://en.wikipedia.org/wiki/Electron>/. Crookes tubes are now used only for demonstrating cathode rays.
Wilhelm Röntgen <http://en.wikipedia.org/wiki/Wilhelm_R%C3%B6ntgen> discovered X-rays <http://en.wikipedia.org/wiki/X-ray> using the Crookes tube in 1895. The term is also used for the first generation, cold cathode <http://en.wikipedia.org/wiki/Cold_cathode> X-ray tubes <http://en.wikipedia.org/wiki/X-ray_tube>,^[4] <http://en.wikipedia.org/wiki/Crookes_tube#cite_note-4> which evolved from the experimental Crookes tubes and were used until about 1920. 


   How a Crookes tube works


Diagram showing a Crookes tube circuit.
Crookes tubes are cold cathode <http://en.wikipedia.org/wiki/Cold_cathode> tubes, meaning that they do not have a heated filament <http://en.wikipedia.org/wiki/Electrical_filament> in them that releases electrons <http://en.wikipedia.org/wiki/Electron> as the later electronic vacuum tubes <http://en.wikipedia.org/wiki/Vacuum_tube> usually do. Instead, electrons are generated by the ionization <http://en.wikipedia.org/wiki/Ionization> of the residual air by a high DC <http://en.wikipedia.org/wiki/Direct_current> voltage <http://en.wikipedia.org/wiki/Voltage> (from a few kilovolts <http://en.wikipedia.org/wiki/Kilovolts> to about 100 kilovolts) applied between the electrodes, usually by an induction coil <http://en.wikipedia.org/wiki/Induction_coil> (a "Ruhmkorff coil"). The Crookes tubes require a small amount of air in them to function, from about 10^-6 to 5×10^-8 atmosphere <http://en.wikipedia.org/wiki/Atm_%28unit%29> (7×10^-4 - 4×10^-5 torr <http://en.wikipedia.org/wiki/Torr_%28unit%29> or 0.1-0.005 pascal <http://en.wikipedia.org/wiki/Pascal_%28unit%29>).
When high voltage <http://en.wikipedia.org/wiki/Voltage> is applied to the tube, the electric field <http://en.wikipedia.org/wiki/Electric_field> accelerates the small number of electrically charged ions <http://en.wikipedia.org/wiki/Ion> always present in the gas, created by natural processes like photoionization <http://en.wikipedia.org/wiki/Photoionization> and radioactivity <http://en.wikipedia.org/wiki/Radioactivity>. These collide with other gas molecules <http://en.wikipedia.org/wiki/Molecule>, knocking electrons off them and creating more positive ions in a chain reaction called a Townsend discharge <http://en.wikipedia.org/wiki/Townsend_discharge>. All the positive ions are attracted to the cathode <http://en.wikipedia.org/wiki/Cathode> or negative electrode. When they strike it, they knock large numbers of electrons out of the surface of the metal, which in turn are repelled by the cathode and attracted to the anode <http://en.wikipedia.org/wiki/Anode> or positive electrode. These are the cathode rays <http://en.wikipedia.org/wiki/Cathode_ray>.
Enough of the air has been removed from the tube that most of the electrons can travel the length of the tube without striking a gas molecule. The high voltage accelerates these low-mass particles to a high velocity (about 37,000 miles per second, or 59,000 km/s, about 20 percent of the speed of light <http://en.wikipedia.org/wiki/Speed_of_light>, for a typical tube voltage of 10 kV^[5] <http://en.wikipedia.org/wiki/Crookes_tube#cite_note-5> ). When they get to the anode end of the tube, they have so much momentum <http://en.wikipedia.org/wiki/Momentum> that, although they are attracted to the anode, many fly past it and strike the end wall of the tube. When they strike atoms in the glass, they knock their orbital electrons <http://en.wikipedia.org/wiki/Atomic_orbital> into a higher energy level <http://en.wikipedia.org/wiki/Energy_level>. When the electrons fall back to their original energy level, they emit light. This process, called fluorescence <http://en.wikipedia.org/wiki/Fluorescence>, causes the glass to glow, usually yellow-green. The electrons themselves are invisible, but the glow reveals where the beam of electrons strikes the glass. Later on, researchers painted the inside back wall of the tube with a phosphor <http://en.wikipedia.org/wiki/Phosphor>, a fluorescent chemical such as zinc sulfide <http://en.wikipedia.org/wiki/Zinc_sulfide>, in order to make the glow more visible. After striking the wall, the electrons eventually make their way to the anode, flow through the anode wire, the power supply, and back to the cathode. 


The different glowing regions possible in a Crookes tube.
The above only describes the motion of the electrons. The full details of the action in a Crookes tube are complicated, because it contains a nonequilibrium plasma <http://en.wikipedia.org/wiki/Plasma_%28physics%29> of positively charged ions <http://en.wikipedia.org/wiki/Ion>, electrons <http://en.wikipedia.org/wiki/Electron>, and neutral atoms <http://en.wikipedia.org/wiki/Atom> which are constantly interacting. At higher gas pressures, above 10^-6 atm (0.1 Pa), this creates different colored glowing regions in the gas, depending on the pressure in the tube (see diagram). The details were not fully understood until the development of plasma physics <http://en.wikipedia.org/wiki/Plasma_physics> in the early 20th century. 


   The discovery of X-rays
When the voltage applied to a Crookes tube is high enough, around 5,000 volts <http://en.wikipedia.org/wiki/Volt> or greater,^[9] <http://en.wikipedia.org/wiki/Crookes_tube#cite_note-9> it can accelerate the electrons to a fast enough velocity to create X-rays <http://en.wikipedia.org/wiki/X-rays> when they hit the anode or the glass wall of the tube. The fast electrons emit X-rays when their path is bent sharply as they pass near the high electric charge of an atom's nucleus <http://en.wikipedia.org/wiki/Atomic_nucleus>, a process called bremsstrahlung <http://en.wikipedia.org/wiki/Bremsstrahlung>, or they knock an atom's inner electrons into a higher energy level <http://en.wikipedia.org/wiki/Energy_level>, and these in turn emit X-rays as they return to their former energy level, a process called X-ray fluorescence <http://en.wikipedia.org/wiki/X-ray_fluorescence>. Many early Crookes tubes undoubtedly generated X-rays, because early researchers such as Ivan Pulyui <http://en.wikipedia.org/wiki/Ivan_Pulyui> had noticed that they could make foggy marks on nearby unexposed photographic plates <http://en.wikipedia.org/wiki/Photographic_plate>. On November 8, 1895, Wilhelm Röntgen <http://en.wikipedia.org/wiki/Wilhelm_R%C3%B6ntgen> was operating a Crookes tube covered with black cardboard when he noticed that a nearby fluorescent screen glowed faintly.^[10] <http://en.wikipedia.org/wiki/Crookes_tube#cite_note-10> He realized that some unknown invisible rays from the tube were able to pass through the cardboard and make the screen fluoresce. He found that they could pass through books and papers on his desk. Röntgen began to investigate the rays full-time, and on December 28, 1895, published the first scientific research paper on X-rays.^[11] <http://en.wikipedia.org/wiki/Crookes_tube#cite_note-11> Röntgen was awarded the first Nobel Prize in Physics <http://en.wikipedia.org/wiki/Nobel_Prize_in_Physics> (in 1901) for his discoveries.
The medical applications of X-rays created the first practical use for Crookes tubes, and workshops began manufacturing specialized Crookes tubes to generate X-rays, the first X-ray tubes. The anode was made of a heavy metal, usually platinum <http://en.wikipedia.org/wiki/Platinum>, which generated more X-rays, and was tilted at an angle to the cathode, so the X-rays would radiate through the side of the tube. The cathode had a concave spherical surface which focused the electrons into a small spot around 1 mm in diameter on the anode, in order to approximate a point source of X-rays, which gave the sharpest radiographs <http://en.wikipedia.org/wiki/Radiograph>. These cold cathode type X-ray tubes were used until about 1920, when they were superseded by the hot cathode <http://en.wikipedia.org/wiki/Hot_cathode> Coolidge X-ray tube. 











--
Alton Smith antiqueradiotubes.com http://www.flickr.com/photos/91001059@N08/
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