Radiation Shielding<\/h3>\n\n\n\n Work in progress\u2014this section will be updated with shielding design details and calculations.<\/em><\/p>\n\n\n\nHigh Voltage<\/h2>\n\n\n\n Operating an X-ray tube requires very high voltages. For the HBJ21 tube, I need 50\u201370 kV. I split this requirement into a two-stage design:<\/p>\n\n\n\n
\n\nStage 1:<\/strong> A high-voltage transformer generating up to 28 kVAC (40 kV peak)<\/li>\n\n\nStage 2:<\/strong> A voltage multiplier that steps this up to a maximum of 160 kVDC<\/li>\n\n<\/ul>\n\n\n\nHigh Voltage Transformer<\/h3>\n\n\n\n The high-voltage transformer generates the first stage output of up to 28 kVAC. It operates at high frequency to improve efficiency and reduce output ripple after rectification. My target frequency is 10 kHz, though 2 kHz should be the minimum for acceptable performance with the current component selection.<\/p>\n\n\n\nTransformer Core<\/h4>\n\n\n\n I selected the UY30 core from an AliExpress seller, primarily due to its large size which allows for well-spaced windings and a high primary-to-secondary turns ratio. I plan to operate this core at less than 10% of its rated power, so I’m not concerned about reaching any thermal or magnetic limits.<\/p>\n\n\n\nTransformer Windings & Insulation<\/h4>\n\n\n\n High voltage insulation is critical for safety and reliability. Key lessons learned during winding construction:<\/p>\n\n\n\nV1 high voltage bobbin (failed due to arcing from inner winding to transformer core)<\/figcaption><\/figure>\n\n\n\nV2 high voltage bobbin\u2014reduced plastic insulation, more space for varnish and Teflon tape<\/figcaption><\/figure>\n\n\n\n\n\nInsulation materials:<\/strong> PETG, high-voltage varnish, and Teflon tape<\/li>\n\n\nVarnish as adhesive:<\/strong> Used high-voltage varnish to bond components together<\/li>\n\n\n3D printed parts:<\/strong> Do not trust 3D-printed parts alone due to layer gaps; use varnish to fill these gaps completely<\/li>\n\n\nWire coating:<\/strong> Apply varnish to wire while coiling to prevent arcing between inner and outer layers through air gaps between wires<\/li>\n\n<\/ul>\n\n\n\nVarnish Selection<\/h4>\n\n\n\n To protect and insulate the windings from damage and high voltage stress, I applied a thick coating of specialized high-voltage varnish. While many DIY builders use simpler solutions like nail polish or epoxy, the best solution I found is MG Chemicals 4228A liquid<\/strong>.<\/p>\n\n\n\nThe difference in dielectric strength is significant:<\/p>\n\n\n\n
\n\nEpoxy:<\/strong> ~500 V\/mil<\/li>\n\n\nMG Chemicals 4228A:<\/strong> 3,700 V\/mil<\/li>\n\n<\/ul>\n\n\n\nWhile it’s somewhat more expensive, the performance improvement justifies the cost. It’s also easy to apply, and the red coloring makes it simple to verify even coverage.<\/p>\n\n\n\n
[Reference: MG Chemicals 4228A Technical Data Sheet]<\/em><\/p>\n\n\n\nElectronics<\/h2>\n\n\n\nHigh Voltage Measurements<\/h3>\n\n\n\n Work in progress\u2014this section will detail the high voltage measurement and monitoring circuitry.<\/em><\/p>\n\n\n\nFilament Driver<\/h3>\n\n\n\n The X-ray tube filament requires current control from 0 to 2.9 A. The filament current directly controls the number of electrons emitted, which in turn determines the X-ray output intensity.<\/p>\n\n\n\n
Because the filament also serves as the return path for the high voltage generator through the X-ray tube, one side must always be connected directly to ground. This necessitates the use of high-side switching and current control.<\/p>\n\n\n\n
Circuit design:<\/strong><\/p>\n\n\n\n\n\nAn LM338T<\/strong> regulator provides a hard current limit of 2.82 A, preventing any over-current conditions<\/li>\n\n\nA shunt resistor<\/strong> provides feedback for current limiting, variable current control, and ADC monitoring<\/li>\n\n\nA MOSFET<\/strong> operating in its linear region enables variable current control<\/li>\n\n\nA DAC<\/strong> provides the setpoint, while an op-amp<\/strong> adjusts the MOSFET to match the target current<\/li>\n\n<\/ul>\n\n\n\nThis linear approach is not power-efficient and will dissipate several watts as heat, requiring adequate cooling. However, efficiency isn’t a primary concern here\u2014I prioritized a simple, robust design over a more complex switching converter, which would introduce additional points of failure.<\/p>\n\n\n\n
Hardware Safety Triggers<\/h3>\n\n\n\n As a fallback for software-based safety systems, I implemented a hardware-based safety circuit that can independently disengage the high-voltage system and trigger an alarm if any parameter exceeds safe thresholds.<\/p>\n\n\n\n
To maximize reliability, this safety system is kept as simple as possible. Multiple comparators monitor voltage readings from different system measurements. Each comparator’s trigger threshold is adjustable via trimmer potentiometers.<\/p>\n\n\n\n
Operation:<\/strong><\/p>\n\n\n\n\n\nWhen a comparator is triggered (input exceeds threshold), it stops pulling down its output<\/li>\n\n\n Because this condition only persists while the signal remains above threshold, a NOR SR latch<\/strong> circuit holds the alarm active until manually reset<\/li>\n\n\nWhile the alarm is active: a buzzer<\/strong> sounds and a red LED<\/strong> indicates which measurement triggered the safety<\/li>\n\n\nMultiple systems are simultaneously powered down to ensure a safe state:<\/li>\n\n<\/ul>\n\n\n\n\n\nPower to the primary side of the high-voltage transformer<\/li>\n\n\n DAC signal to the high-voltage transformer amplifier<\/li>\n\n\n AC power to the high-voltage transformer amplifier<\/li>\n\n\n Filament current driver<\/li>\n\n<\/ul>\n\n\n\nA self-test system<\/strong> using relays on each channel allows the safety system to be tested by ramping up the DAC signal and verifying that the safety circuit activates at the correct threshold.<\/p>\n\n\n\nHere is the complete safety circuit diagram:<\/p>\n\n\n\n
[Insert safety circuit diagram]<\/em><\/p>\n\n\n\nCategories:<\/strong> Uncategorized<\/p>\n\n\n","protected":false},"excerpt":{"rendered":"I’ve been working on building my own X-ray machine to image objects and determine their internal geometry without destructive testing. This project is still a work in progress, but I wanted to share some of my progress so far. I’m using this post for my own documentation as well, so<\/p>\n
Continue readingDIY X-Ray Imaging System<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-726","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/posts\/726","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/comments?post=726"}],"version-history":[{"count":13,"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/posts\/726\/revisions"}],"predecessor-version":[{"id":927,"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/posts\/726\/revisions\/927"}],"wp:attachment":[{"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/media?parent=726"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/categories?post=726"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/labparvum.com\/index.php\/wp-json\/wp\/v2\/tags?post=726"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\"Schematic](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/05\/Schematics-of-a-conventional-X-ray-tube-the-electrons-e-are-emitted-from-the-1.jpg\")
<\/figure>\n\n\n\n![\"HBJ21](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/05\/S44723d907816426dad70bce4797b24e2G.webp\")
<\/figure>\n\n\n\n![\"X-ray](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/05\/X-ray-spectrum-OMP.png\")
<\/figure>\n\n\n\n![\"Comparative](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/05\/1-s2.0-S0969806X21000876-gr7.jpg\")
<\/figure>\n\n\n\n![\"Radiacode](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/05\/4067478196-1024x1024.png\")
<\/figure>\n\n\n\n![\"High](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/05\/Screenshot-2025-05-28-152417-1024x240.png\")
<\/figure>\n\n\n\n![\"High](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/02\/IMG20250827223911-768x1024.jpg\")
<\/figure>\n\n\n\n![\"UY30](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/03\/71ApB7x7lfL._SL1200_-1024x1024.jpg\")
<\/figure>\n\n\n\n![\"V1](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/02\/image-6-1024x643.png\")
![\"V2](\"https:\/\/labparvum.com\/wp-content\/uploads\/2025\/02\/image-7-1024x655.png\")