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<\/p>\n\n\n\ndeally, you should power your PMT from a lab-grade, low-noise, high-voltage power supply designed specifically to bias detectors. However, achieving exceptionally low ripple and high stability in a high-voltage power supply is not trivial, making these power supplies pricey. Designs for these low-noise power supplies are secrets closely guarded by companies that specialize in such products, such as Matsusada Precision, EMCO High Voltage, and Hamamatsu Photonics. Fortunately, relatively low-cost, high-voltage power supply modules are sold by these companies as components for larger instruments.<\/p>\n\n\n\n
Our home-built PMT power supply is built around the Matsusada JBE-2P high-voltage power supply module. This module sells new for around $200, but similar units can be found on the surplus market for a fraction of this price. The module is powered by 24 VDC (at 300 mA typical), and generates up to 2,000 V at 1 mA as a function of a 0- to 10-V control input. A 10-V reference output is available on the JBE-2P, allowing a 5 k\u03a9 potentiometer to be used for voltage control.<\/p>\n\n\n\n
The schematic diagram of\u00a0Figure 31\u00a0shows that 24 V for the JBE-2P are obtained by rectifying the output of a 25.2-V transformer (T1, a RadioShack 273-1366A) and regulating through a LM317 variable linear regulator. A kit comprising a circuit board and components for the regulator circuit is conveniently available from Velleman as their model K1823.<\/p>\n\n\n\n
Figure 31\u00a0Our variable-output PMT power supply is based around a Matsusada JBE-2P low-ripple, high-stability, high-voltage power module. Output voltage (up to 2 kV) and current (up to 1 mA) are monitored via two LCD panel meters.<\/p>\n\n\n\n
A second transformer and regulator board are used to produce an isolated output of +9 VDC to power two 3 1<\/sup>\/2<\/sub>-digit panel voltmeters. The digital voltmeters are used to show the voltage and current output from the high-voltage module. We used Lascar EMV1125 LCD panel meters because they need only a 7\/32-in. round hole for mounting, but any other 200-mV full-scale panel meter module should work equally well.<\/p>\n\n\n\n An even lower-cost alternative is to build the PMT power supply from a BXA-12579 high-voltage inverter used to drive a cold-cathode fluorescent lamp (CCFL). This under-$20 module produces 1,500 VAC at around 30 kHz from a 12-VDC input.<\/p>\n\n\n\n As shown in the schematic diagram of\u00a0Figure 32, the BXA-12579 has to be slightly modified for use in this circuit. The 100-\u03bcF\/25-V capacitor marked \u201cC1\u201d in the BXA-12579 needs to be removed so that the power input to the module can be varied rapidly. In addition, a pin needs to be added to access the transformer\u2019s high-voltage terminal, and the line connecting the low-voltage to the high-voltage ground must be cut.<\/p>\n\n\n\n Figure 32\u00a0A low-cost, variable-voltage PMT power supply can be based on a BXA-12579 inverter module that was originally designed as a power supply for CCFLs. In this circuit, the supply to the BXA-12579 inverter is modulated by op-amp U3. The high-voltage AC output of the inverter is rectified and doubled by D2\/D3 and C7\/C12. C13\/C14 are used to filter the high-voltage output.<\/p>\n\n\n\n The output voltage is regulated to the desired level by feeding op-amp U3 with an attenuated version of the output. This level is compared against the output of voltage control R17. The op-amp attempts to maintain the output constant by controlling the power to the inverter by way of transistor Q1.<\/p>\n\n\n\n This design incorporates a circuit used by Spectrum Techniques to reduce ripple in their PMT power supplies.7<\/sup> Op-amp U2 is used to neutralize AC signals from the high-voltage output by adding a voltage that is 180\u00b0 out of phase with any signal that goes through C9. A very stable and clean output can be obtained if the circuit is built within a grounded, metallic enclosure, being careful to prevent coupling of the high-voltage AC output into the rest of the circuit.<\/p>\n","protected":false},"excerpt":{"rendered":" deally, you should power your PMT from a lab-grade, low-noise, high-voltage power supply designed specifically to bias detectors. However, achieving exceptionally low ripple and high stability in a high-voltage power supply is not trivial, making these power supplies pricey. Designs for these low-noise power supplies are secrets closely guarded by companies that specialize in such […]<\/p>\n","protected":false},"author":1,"featured_media":4171,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[512],"tags":[],"class_list":["post-4283","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-light-as-particles"],"jetpack_featured_media_url":"https:\/\/workhouse.sweetdishy.com\/wp-content\/uploads\/2024\/09\/bulb.png","_links":{"self":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/4283","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/comments?post=4283"}],"version-history":[{"count":1,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/4283\/revisions"}],"predecessor-version":[{"id":4286,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/4283\/revisions\/4286"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media\/4171"}],"wp:attachment":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media?parent=4283"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/categories?post=4283"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/tags?post=4283"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/learning.oreilly.com\/api\/v2\/epubs\/urn:orm:book:9781118170700\/files\/OEBPS\/images\/40-1.jpg\")
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