Characterisation of Au surface properties relevant for UV photoemission-based charge control for space inertial sensors

Precision space inertial sensors used for satellite geodesy missions, tests of fundamental physics, and gravitational wave observation utilise UV photoemission to control the electric potential of free-falling test masses with respect to their surrounding electrode housings. Successful generation of photoelectrons requires UV light energies greater than the work function of the illuminated surface. To ensure bi-polar test mass charge control (positive and negative charge rates), the quantum yields of the test mass and electrode housing surfaces must be well-balanced. LISA Pathfinder used mercury vapour lamps at 254 nm to discharge the gold coated test mass by likely relying on contaminants to lower the work function of gold from its nominal value of 5.2 eV. The LISA gravitational wave mission plans to use UV light emitting diodes (LEDs) instead of mercury vapour lamps. These UV LEDs have a lower mass, higher power efficiency, and produce light at wavelengths below 240 nm. In this paper, we measure the quantum yields of several Au-coated surfaces over a range of UV wavelengths and environmental conditions, varying temperature, vacuum pressure, and measuring over long periods of time. We use these data to draw conclusions and make recommendations for the development and handling of precision space inertial sensors for LISA and for other missions in the future.

[1]  Karsten Danzmann,et al.  LISA Pathfinder , 2019, Lepton Photon Interactions at High Energies.

[2]  T. Sumner,et al.  Effective decrease of photoelectric emission threshold from gold plated surfaces. , 2019, The Review of scientific instruments.

[3]  Salvatore J. Vitale,et al.  Precision charge control for isolated free-falling test masses: LISA pathfinder results , 2018, Physical Review D.

[4]  J. P. López-Zaragoza,et al.  Beyond the Required LISA Free-Fall Performance: New LISA Pathfinder Results down to 20  μHz. , 2018, Physical review letters.

[5]  J. P. López-Zaragoza,et al.  Charge-Induced Force Noise on Free-Falling Test Masses: Results from LISA Pathfinder. , 2017, Physical review letters.

[6]  G. Mueller,et al.  A new torsion pendulum for gravitational reference sensor technology development. , 2017, The Review of scientific instruments.

[7]  Badr Bin Salamah,et al.  Ground testing and flight demonstration of charge management of insulated test masses using UV-LED electron photoemission , 2016, 1607.03564.

[8]  J. P. López-Zaragoza,et al.  Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results. , 2016, Physical review letters.

[9]  Antoine Kahn,et al.  Fermi level, work function and vacuum level , 2016 .

[10]  G. Keiser,et al.  The Gravity Probe B gyroscope , 2015 .

[11]  Badr N. Alsuwaidan,et al.  The Gravity Probe B test of general relativity , 2015 .

[12]  G. Mueller,et al.  240 nm UV LEDs for LISA test mass charge control , 2015 .

[13]  Walter Fichter,et al.  Modeling and performance of contact-free discharge systems for space inertial sensors , 2012, IEEE Transactions on Aerospace and Electronic Systems.

[14]  D. DeBra,et al.  Invited article: advanced drag-free concepts for future space-based interferometers: acceleration noise performance. , 2009, The Review of scientific instruments.

[15]  Daniele Bortoluzzi,et al.  Prediction of the LISA-Pathfinder release mechanism in-flight performance , 2013 .

[16]  John Conklin,et al.  Measurement of drag and its cancellation , 2011 .

[17]  Daniel Hollington,et al.  The charge management system for LISA and LISA Pathfinder , 2011 .

[18]  R. Byer,et al.  UV LED operation lifetime and radiation hardness qualification for space flights , 2009 .

[19]  Diana N. Shaul,et al.  CHARGE MANAGEMENT FOR LISA AND LISA PATHFINDER , 2008 .

[20]  B. de Boer,et al.  Tuning of Metal Work Functions with Self‐Assembled Monolayers , 2005 .

[21]  Amy L. Graham,et al.  Interface Dipoles Arising from Self-Assembled Monolayers on Gold: UV−Photoemission Studies of Alkanethiols and Partially Fluorinated Alkanethiols , 2003 .

[22]  Paolo Bosetti,et al.  Gravitational sensor for LISA and its technology demonstration mission , 2003 .

[23]  Bonny L. Schumaker,et al.  Disturbance reduction requirements for LISA , 2003 .

[24]  A Satellite Freed of all but Gravitational Forces : " TRIAD I " STAFF , 2003 .

[25]  J. Delhalle,et al.  Self-Assembled Monolayers of n-Dodecanethiol on Electrochemically Modified Polycrystalline Nickel Surfaces , 1997 .

[26]  R. W. Christy,et al.  Optical Constants of the Noble Metals , 1972 .

[27]  Marie-Luce Thèye,et al.  Investigation of the Optical Properties of Au by Means of Thin Semitransparent Films , 1970 .

[28]  J. Rivière.  THE WORK FUNCTION OF GOLD , 1966 .