Dispenser cathodes: The current state of the technology

Falce, Lou

doi:10.1109/iedm.1983.190538

Cited by 21 publications

(7 citation statements)

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“…Dispenser cathodes are a mature technology, deployed in numerous vacuum tube based communication applications, with excellent lifetime when the vacuum conditions are appropriate (∼10 −7 Torr total pressure, low levels of contaminants that are detrimental to DCEs, such as carbon monoxide, carbon dioxide, oxygen, and water vapor). Literature mentions that DCEs similar to the ones implemented in the multisource have a lifetime entitlement of thousands to tens of thousands of hours at current densities of few A/cm 2 ; 22 DCEs typically perform well at few A/cm 2 in continuous mode and at low tens of A/cm 2 in the pulse emission mode. 23 The dispenser cathodes in the multisource have been heated at the operating temperature for few hundreds of hours, with excellent emission stability.…”

Section: Discussionmentioning

confidence: 99%

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

et al. 2016

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Purpose: This paper summarizes the development of a high-power distributed x-ray source, or "multisource," designed for inverse-geometry computed tomography (CT) applications [see B. De Man et al., "Multisource inverse-geometry CT. Part I. System concept and development," Med. Phys. 43, 4607-4616 (2016)]. The paper presents the evolution of the source architecture, component design (anode, emitter, beam optics, control electronics, high voltage insulator), and experimental validation. Methods: Dispenser cathode emitters were chosen as electron sources. A modular design was adopted, with eight electron emitters (two rows of four emitters) per module, wherein tungsten targets were brazed onto copper anode blocks-one anode block per module. A specialized ceramic connector provided high voltage standoff capability and cooling oil flow to the anode. A matrix topology and low-noise electronic controls provided switching of the emitters. Results: Four modules (32 x-ray sources in two rows of 16) have been successfully integrated into a single vacuum vessel and operated on an inverse-geometry computed tomography system. Dispenser cathodes provided high beam current (>1000 mA) in pulse mode, and the electrostatic lenses focused the current beam to a small optical focal spot size (0.5 × 1.4 mm). Controlled emitter grid voltage allowed the beam current to be varied for each source, providing the ability to modulate beam current across the fan of the x-ray beam, denoted as a virtual bowtie filter. The custom designed controls achieved x-ray source switching in <1 µs. The cathode-grounded source was operated successfully up to 120 kV. Conclusions: A high-power, distributed x-ray source for inverse-geometry CT applications was successfully designed, fabricated, and operated. Future embodiments may increase the number of spots and utilize fast read out detectors to increase the x-ray flux magnitude further, while still staying within the stationary target inherent thermal limitations. C 2016 American Association of Physicists in Medicine. [http://dx

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Section: Discussionmentioning

confidence: 99%

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

et al. 2016

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“…Electron emission from a dispenser cathode utilizes a tungsten (W) pellet impregnated with a barium (Ba) compound [1,2]. Thermionic emission is induced by heating the tungsten pellet to high temperatures with a heating element enclosed in the body of the cathode.…”

Section: Introductionmentioning

confidence: 99%

Influence of Os-Ru coating on closed-space diode tests of M-Type dispenser cathodes

Swartzentruber

Balk

Roberts³

2011

2011 IEEE International Vacuum Electronics Conference (IVEC)

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Life testing of M-Type dispenser cathodes was performed for 1000 hours to help quantify the performance enhancement due to different osmium-ruthenium (Os-Ru) thin film microstructures. Os-Ru film microstructures were selected based on their potential to inhibit tungsten/Os-Ru interdiffusion as identified in previous studies. The results show that the 10W substrate biased 150nm thick film yielded a very stable knee temperature throughout its life. However, the knee temperature was high in comparison to the standard Semicon film.

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“…Dispenser cathodes are comprised of a porous tungsten (W) pellet impregnated with a barium (Ba) compound to improve electron emission [1,2]. The body of the cathode houses a heating element that heats the tungsten pellet to induce thermionic emission.…”

Section: Introductionmentioning

confidence: 99%

6.2: Optimizing osmium-ruthenium films to inhibit tungsten interdiffusion

Swartzentruber

Balk

et al. 2010

2010 IEEE International Vacuum Electronics Conference (IVEC)

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Osmium-ruthenium thin films were deposited on porous tungsten pellets, at the same time as cathode assemblies, to investigate possibilities for minimizing interdiffusion. Previous studies had identified promising film characteristics for inhibiting tungsten interdiffusion. For example, it was found that a 5W-substrate-biased film of 550 nm thickness exhibited high structural and compositional stability, and several other films exhibited promising properties as well. These films were produced and annealed, then analyzed for composition. Emission tests of M-type cathode assemblies, coated with the same candidate films, were performed to assess the degree of lifetime improvement imparted by the films to the cathodes.

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Dispenser cathodes: The current state of the technology

Cited by 21 publications

References 0 publications

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

Influence of Os-Ru coating on closed-space diode tests of M-Type dispenser cathodes

6.2: Optimizing osmium-ruthenium films to inhibit tungsten interdiffusion

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