Editing Cathode-ray tube (section)

===Anode===  <!--Expand: how anode voltage is derived from horizontal deflection circuitry, the horiz. deflection coil and its voltage, which is created by the flyback so it creates anode voltage that is then multiplied and fed and horiz. deflection coil voltage that contributes to anode voltage, maybe flyback first creates 120v horiz. high current voltage, goes to the coil, returns from the coil, then its fed and voltage multiplied and energy added and fed to the anode-->
The outer conductive coating is connected to ground while the inner conductive coating is connected using the anode button/cap through a series of capacitors and diodes (a [[Cockcroft–Walton generator]]) to the high voltage [[flyback transformer]]; the inner coating is the anode of the CRT,<ref name="auto54">{{cite web |url=https://worldradiohistory.com/hd2/IDX-Business/Books/Regulation/IDX/Radio-Operating-Questions-&-Answers-12th-OCR-Page-0494.pdf |archive-url=https://web.archive.org/web/20210306171748/https://worldradiohistory.com/hd2/IDX-Business/Books/Regulation/IDX/Radio-Operating-Questions-&-Answers-12th-OCR-Page-0494.pdf |archive-date=2021-03-06 |url-status=live |title=Radio operating Q&A |website= worldradiohistory.com|access-date=2020-12-11}}</ref> which, together with an electrode in the electron gun, is also known as the final anode.<ref>{{Cite patent |country=US |number=7071605B2 |url=https://patents.google.com/patent/US7071605B2/en |title=Cathode structure for color cathode ray tube}}</ref><ref name="auto6">{{Cite book|author= Thorn-AEI Radio Valves and Tubes Limited <!--http://www.r-type.org/articles/art-004f.htm-->|title=Electrons in Shadow-mask Colour Tubes|location= United Kingdom|date=1968}}</ref> The inner coating is connected to the electrode using springs. The electrode forms part of a bipotential lens.<ref name="auto6"/><ref name="auto11">{{Cite patent |country=US |number=5196764A |url=https://patents.google.com/patent/US5196764A/en |title=Cathode ray tube having symmetrical anode potential}}</ref> The capacitors and diodes serve as a [[voltage multiplier]] for the current delivered by the flyback.

For the inner funnel coating, monochrome CRTs use aluminum while color CRTs use [[aquadag]];<ref name="auto38"/> Some CRTs may use iron oxide on the inside.<ref name="auto50"/> On the outside, most CRTs (but not all)<ref>https://www.crtsite.com/radar-crt.html there is no matte black coating on the outside of the CRT so here is no aquadag on the outside</ref> use aquadag.<ref>{{Cite book|url=https://books.google.com/books?id=90GZPA-hCuMC&q=crt+aquadag+outer+outside&pg=PA134|title=Newnes Guide to Television and Video Technology: The Guide for the Digital Age - from HDTV, DVD and flat-screen technologies to Multimedia Broadcasting, Mobile TV and Blu Ray|first=K. F.|last=Ibrahim|date=14 September 2007|publisher=Elsevier|isbn=9780080550664|via=Google Books}}</ref> Aquadag is an electrically conductive graphite-based paint. In color CRTs, the aquadag is sprayed onto the interior of the funnel<ref>{{Cite patent |country=US |number=3791846A |url=https://patents.google.com/patent/US3791846A/en |title=Method for applying an internal coating to a cathode ray tube}}</ref><ref name="auto38"/> whereas historically aquadag was painted into the interior of monochrome CRTs.<ref name="auto68"/>

The anode is used to accelerate the electrons towards the screen and also collects the secondary electrons that are emitted by the phosphor particles in the vacuum of the CRT.<ref>{{cite web | first=Kirt|last=Blattenberger | title=Navy Electricity and Electronics Training Series (NEETS), Module 6 | website=RF Cafe | url=https://www.rfcafe.com/references/electrical/NEETS-Modules/NEETS-Module-06-2-21-2-30.htm | access-date=2020-12-11}} <!--US military source--></ref><ref name="auto70">{{Cite patent |country=US |number=2582822A |url=https://patents.google.com/patent/US2582822A/en |title=Cathode-ray tube with aluminized screen}}</ref><ref>{{Cite web|url=https://electronicscoach.com/cathode-ray-tube-c-r-t.html|title=What is CRT (Cathode Ray Tube)? definition, block diagram and working of CRT|date=19 May 2018}}</ref><ref name="auto82">{{cite journal |last1=Ozawa |first1=Lyuji |title=Electron flow route at phosphor screens in CRTs |journal=Materials Chemistry and Physics |date=15 January 2002 |volume=73 |issue=2 |pages=144–150 |doi=10.1016/s0254-0584(01)00360-1 }}</ref><ref name="auto68"/>

The anode cap connection in modern CRTs must be able to handle up to 55–60kV depending on the size and brightness of the CRT. Higher voltages allow for larger CRTs, higher image brightness, or a tradeoff between the two.<ref name="auto36">{{cite journal |last1=Solomos |first1=E. |title=A projection graphic display for the computer aided analysis of bubble chamber images |journal=Nuclear Instruments and Methods |date=20 December 1979 |volume=167 |issue=2 |pages=305–311 |doi=10.1016/0029-554X(79)90019-3 |bibcode=1979NucIM.167..305S |url=https://cds.cern.ch/record/133614 }}</ref><ref name="auto3"/> It consists of a metal clip that expands on the inside of an anode button that is embedded on the funnel glass of the CRT.<ref name="auto16">{{Cite patent |country=US |number=5583392A |url=https://patents.google.com/patent/US5583392A/en |title=CRT anode cap}}</ref><ref>{{Cite web|url=https://www.petervis.com/electronics%20guides/Sony%20KV-36FS76U/final-anode.html|title=Final Anode|accessdate=18 December 2022}}</ref> The connection is insulated by a silicone suction cup, possibly also using silicone grease to prevent [[corona discharge]].<ref>{{Cite web|url=http://repairfaq.cis.upenn.edu/Misc/samnew/tvfaq/tvasocfcrt.htm|title=SER FAQ: TVFAQ: Arcing, sparking, or corona from CRT HV anode (red wire/suction cup)|website=repairfaq.cis.upenn.edu|access-date=8 December 2020|archive-date=30 October 2020|archive-url=https://web.archive.org/web/20201030212335/http://repairfaq.cis.upenn.edu/Misc/samnew/tvfaq/tvasocfcrt.htm|url-status=dead}}</ref><ref>{{Cite web|url=https://www.repairfaq.org/samnew/tvfaq/tvrchvc.htm|title=SER FAQ: TVFAQ: Removing the CRT HV connector|website=www.repairfaq.org}}</ref>

The anode button must be specially shaped to establish a hermetic seal between the button and funnel. X-rays may leak through the anode button, although that may not be the case in newer CRTs starting from the late 1970s to early 1980s, thanks to a new button and clip design.<ref name="auto3"/><ref>{{cite web | url=https://patents.google.com/patent/DE2833485C2/en?q=(Crt+anode+nickel+cup)&assignee=Toshiba&oq=Crt+anode+nickel+cup+Toshiba+ | title=Anodenknopf für eine Kathodenstrahlröhre }}</ref> The button may consist of a set of 3 nested cups, with the outermost cup being made of a Nickel–Chromium–Iron alloy containing 40–49% of Nickel and 3–6% of Chromium to make the button easy to fuse to the funnel glass, with a first inner cup made of thick inexpensive iron to shield against x-rays, and with the second innermost cup also being made of iron or any other electrically conductive metal to connect to the clip. The cups must be heat resistant enough and have similar thermal expansion coefficients similar to that of the funnel glass to withstand being fused to the funnel glass. The inner side of the button is connected to the inner conductive coating of the CRT.<ref name="auto70"/> The anode button may be attached to the funnel while its being pressed into shape in a mold.<ref>{{Cite patent |country=KR |number=20000050533A |url=https://patents.google.com/patent/KR20000050533A/en |title=Apparatus for fusion-welding anode button to crt funnel}}
{{Cite web|url=https://books.google.com/books?id=oaWc_Z7Y-A8C&q=crt+glass+funnel+press+mold&pg=PA200|title=Official Gazette of the United States Patent Office|publisher=United States Patent Office|date=5 December 1969|via=Google Books}} press
{{Cite patent |country=US |number=4198588A |url=https://patents.google.com/patent/US4198588A/en |title=Anode button for a cathode ray tube}} nested design
{{Cite patent |country=US |number=4155614A |url=https://patents.google.com/patent/US4155614A/en |title=Connector assembly for anode button of a cathode ray tube}} clip and cap design, x-rays</ref><ref name="auto24">{{Cite patent |country=US |number=4422707A |url=https://patents.google.com/patent/US4422707A/en |title=CRT Anode cap}}</ref><ref name="auto3"/> Alternatively, the x-ray shielding may instead be built into the clip.<ref>{{Cite patent |country=US |number=4894023A |url=https://patents.google.com/patent/US4894023A/en |title=Connector assembly for anode ring of cathode ray tube}}</ref>

The flyback transformer is also known as an IHVT (Integrated High Voltage Transformer) if it includes a voltage multiplier. The flyback uses a ceramic or powdered iron core to enable efficient operation at high frequencies. The flyback contains one primary and many secondary windings that provide several different voltages. The main secondary winding supplies the voltage multiplier with voltage pulses to ultimately supply the CRT with the high anode voltage it uses, while the remaining windings supply the CRT's filament voltage, keying pulses, focus voltage and voltages derived from the scan raster. When the transformer is turned off, the flyback's magnetic field quickly collapses which induces high voltage in its windings. The speed at which the magnetic field collapses determines the voltage that is induced, so the voltage increases alongside its speed. A capacitor (Retrace Timing Capacitor) or series of capacitors (to provide redundancy) is used to slow the collapse of the magnetic field.<ref name="auto89" /><ref>{{Cite patent |country=US |number=4825129A |url=https://patents.google.com/patent/US4825129A/en |title=CRT focus tracking arrangement}}</ref>

The design of the high voltage power supply in a product using a CRT has an influence in the amount of x-rays emitted by the CRT. The amount of emitted x-rays increases with both higher voltages and currents. If the product such as a TV set uses an unregulated high voltage power supply, meaning that anode and focus voltage go down with increasing electron current when displaying a bright image, the amount of emitted x-rays is as its highest when the CRT is displaying a moderately bright images, since when displaying dark or bright images, the higher anode voltage counteracts the lower electron beam current and vice versa respectively. The high voltage regulator and rectifier vacuum tubes in some old CRT TV sets may also emit x-rays.<ref name="auto74">{{Cite magazine|title=TV X-Rays<!--http://www.rfcafe.com/references/radio-electronics/tv-x-rays-radio-electronics-april-1970.htm-->|date=April 1970|magazine=Radio Electronics}}</ref>