240 nm UV LEDs for LISA test mass charge control

Olatunde, Taiwo; Shelley, Ryan; Chilton, Andrew; Serra, Paul; Ciani, G.; Mueller, G.; Conklin, John

doi:10.1088/1742-6596/610/1/012034

Cited by 14 publications

(12 citation statements)

References 3 publications

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“…These include low-pressure Hg discharge lamps as used on ROSAT 29 , GP-B 1 and LISA Pathfinder 30 , and various deep UV light emitting diodes (LEDs) 6,7,[31][32][33] . Of particular interest is that some of the new LEDs 31-33 offer spectra with photons of higher energy than the nominal gold work function of 5.1 eV.…”

Section: A Quantum Yieldmentioning

confidence: 99%

Effective decrease of photoelectric emission threshold from gold plated surfaces

Wass

Hollington

Sumner

et al. 2019

Review of Scientific Instruments

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Many applications require charge neutralisation of isolated test bodies and this has been successfully done using photoelectric emission from surfaces which are electrically benign (gold) or superconducting (niobium). Gold surfaces nominally have a high work function (∼ 5.1 eV) which should require deep UV photons for photoemission. In practice it has been found that it can be achieved with somewhat lower energy photons with indicative work functions of (4.1 − 4.3 eV). A detailed working understanding of the process is lacking and this work reports on a study of the photoelectric emission properties of 4.6 × 4.6 cm 2 gold plated surfaces, representative of those used in typical satellite applications with a film thickness of 800 nm, and measured surface roughnesses between 7 and 340 nm. Various UV sources with photon energies from 4.8 to 6.2 eV and power outputs from 1 nW to 1000 nW, illuminated a ∼ 0.3 cm 2 of the central surface region at angles of incidence from 0 to 60 • .Final extrinsic quantum yields in the range 10 ppm to 44 ppm were reliably obtained during 8 campaigns, covering a ∼3 year period, but with intermediate long-term variations lasting several weeks and, in some cases, bake-out procedures at up to 200 o C. Experimental results were obtained in a vacuum system with a baseline pressure of ∼ 10 −7 mbar at room temperature. A working model, designed to allow accurate simulation of any experimental configuration, is proposed.

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Section: A Quantum Yieldmentioning

confidence: 99%

Effective decrease of photoelectric emission threshold from gold plated surfaces

Wass

Hollington

Sumner

et al. 2019

Review of Scientific Instruments

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“…Charge management is achieved through photoemission; missions such as Gravity Probe B [13] and LISA Pathfinder [12] have used the 254nm UV line of Mercury lamps as the light source. Deep UV-LEDs operating at 255nm have been identified as a new method to mitigate TM charging [14,15]; newer UV-LED devices operating at wavelengths as low as 240nm are also becoming commercially available [16]. Compared to Hg lamps, UV-LEDs are smaller and lighter, consume less power, have a wider spectrum selection, and a much higher dynamic range, with at least an order of magnitude improvement in each performance area.…”

Section: Introductionmentioning

confidence: 99%

Ground testing and flight demonstration of charge management of insulated test masses using UV-LED electron photoemission

Saraf

Buchman

Balakrishnan

et al. 2016

Class. Quantum Grav.

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Abstract.The UV-LED mission demonstrates the precise control of the potential of electrically isolated test masses that is essential for the operation of space accelerometers and drag-free sensors. Accelerometers and drag-free sensors were and remain at the core of geodesy, aeronomy and precision navigation missions as well as gravitational science experiments and gravitational wave observatories. Charge management using photoelectrons generated by the 254nm UV line of Hg was first demonstrated on Gravity Probe B and is presently part of the LISA Pathfinder technology demonstration. The UV-LED mission and prior ground testing demonstrates that AlGaN UVLEDs operating at 255 nm are superior to Mercury vapor lamps because of their smaller size, lower power draw, higher dynamic range, and higher control authority. We show flight data from a small satellite mission on a Saudi Satellite that demonstrates AC charge control (UV-LEDs and bias are AC modulated with adjustable relative phase) between a spherical test mass and its housing. The result of the mission is to bring the UV-LED device Technology Readiness Level (TRL) to TRL-9 and the charge management system to TRL-7. We demonstrate the ability to control the test mass potential on an 89 mm diameter spherical test mass over a 20 mm gap in a drag-free system configuration. The test mass potential was measured with an ultra-high impedance contact probe. Finally, the key electrical and optical characteristics of the UV-LEDs showed less than 7.5% change in performance after 12 months in orbit.

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“…Compared to Hg lamps, UV LEDs are smaller, lighter, consume less power, have a wider spectrum selection, and a higher dynamic range, with at least an order of magnitude improvement in each performance area. The power output is also very stable, with a lifetime of ∼ 30, 000 hours 28 .…”

Section: Test Mass Charge Measurement and Controlmentioning

confidence: 99%

A new torsion pendulum for gravitational reference sensor technology development

Ciani

Chilton

Apple

et al. 2017

Review of Scientific Instruments

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We report on the design and sensitivity of a new torsion pendulum for measuring the performance of ultra-precise inertial sensors and for the development of associated technologies for space-based gravitational wave observatories and geodesy missions. The apparatus comprises a 1 m-long, 50 μm-diameter tungsten fiber that supports an inertial member inside a vacuum system. The inertial member is an aluminum crossbar with four hollow cubic test masses at each end. This structure converts the rotation of the torsion pendulum into translation of the test masses. Two test masses are enclosed in capacitive sensors which provide readout and actuation. These test masses are electrically insulated from the rest of the crossbar and their electrical charge is controlled by photoemission using fiber-coupled ultraviolet light emitting diodes. The capacitive readout measures the test mass displacement with a broadband sensitivity of 30 nm∕Hz and is complemented by a laser interferometer with a sensitivity of about 0.5 nm∕Hz. The performance of the pendulum, as determined by the measured residual torque noise and expressed in terms of equivalent force acting on a single test mass, is roughly 200 fN∕Hz around 2 mHz, which is about a factor of 20 above the thermal noise limit of the fiber.

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240 nm UV LEDs for LISA test mass charge control

Cited by 14 publications

References 3 publications

Effective decrease of photoelectric emission threshold from gold plated surfaces

Effective decrease of photoelectric emission threshold from gold plated surfaces

Ground testing and flight demonstration of charge management of insulated test masses using UV-LED electron photoemission

A new torsion pendulum for gravitational reference sensor technology development

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