Charge measurement and mitigation for the main test masses of the GEO 600 gravitational wave observatory

Hewitson, M., Danzmann, K., Grote, H., Hild, S., Hough, J., Luck, H., Rowan, S., Smith, J.R., Strain, K. and Willke, B. (2007) Charge measurement and mitigation for the main test masses of the GEO 600 gravitational wave observatory. Classical and Quantum Gravity, 24(24), pp. 6379-6391. (doi: 10.1088/0264-9381/24/24/013)

Abstract

Spurious charging of the test masses in gravitational wave interferometers is a well-known problem. Typically, concern arises due to the possibility of increased thermal noise due to a lowering of the quality factor of modes of the test-mass suspension, or due to the potential for increased displacement noise arising from charge migration on the surface of the test masses. Recent experience gained at the GEO 600 gravitational wave detector has highlighted an additional problem. GEO 600 uses electrostatic actuators to control the longitudinal position of the main test masses. The presence of charge on the test masses is shown to strongly affect the performance of the electrostatic actuators. This paper reports on a measurement scheme whereby the charge state of the GEO 600 test masses can be measured using the electrostatic actuators. The resulting measurements are expressed in terms of an effective bias voltage on the electrostatic actuators. We also describe attempts to remove the charge from the test masses and we show that the use of UV illumination was the most successful. Using UV illumination we were able to discharge and re-charge the test masses.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Rowan, Professor Sheila and Hough, Professor James and Strain, Professor Kenneth
• Authors: Hewitson, M., Danzmann, K., Grote, H., Hild, S., Hough, J., Luck, H., Rowan, S., Smith, J.R., Strain, K., and Willke, B.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Research Centre: College of Science and Engineering > School of Physics and Astronomy > Institute for Gravitational Research
• Journal Name: Classical and Quantum Gravity
• Publisher: Institute of Physics
• ISSN: 0264-9381
• ISSN (Online): 1361-6382

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
45931	2	Investigations in Gravitational Radiation.	Sheila Rowan	Science & Technologies Facilities Council (STFC)	ST/I001085/1	Physics and Astronomy