Material Stability Studies for SpaceBased Missions

1
Material Stability Studies for Space-Based
Missions

• Alix Preston, Sridhar Reddy Guntaka, Rachel Cruz,
  J. Ira Thorpe, Gabriel Boothe, Rodrigo
  Delgadillo, Guido Mueller

2
LISA Requirements

• Stability of optical bench and telescope lt 1
  pm/vHz
• Stability of frequency reference cavity lt 10
  fm/vHz
• Non-thermal fluctuations are unknown and cannot
  be modeled in thermal simulations
• Stress release, creep, thermal noise, and aging
  could produce noise several orders of magnitude
  above what thermal models predict

• Potential Materials
• Zerodur
• ULE
• SiC
• CFRP

• Bonding Techniques
• Optical Contacts
• Hydroxide Bonding
• Silicate Bonding

3
Material Properties
4
Bonding Techniques
5
Experimental Setup

• 5 layers of gold coated stainless steel
• A similar system at Goddard reached a temperature
  stability of better than 10 µK/vHz at 1 mHz.
• Frequency of each laser is independently
  stabilized to each cavity

SiC and Zerodur cavities inside thermal shields
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Optical Cavities

• Silicon carbide cavity with optically contacted
  mirrors
• Possible material for telescope support structure
• Zerodur cavity with hydroxide bonded mirrors

SiC cavity with optically contacted mirrors
Zerodur cavity with hydroxide bonded mirrors
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Zerodur with Hydroxide Bonded Mirrors
Preliminary Results

• We expect to reach noise requirement levels
• In the process of characterizing the new tank

8
Silicon Carbide
Preliminary Results

• Already meets LISA requirement for the telescope
  support
• Long term temperature drifts are uncontrolled

9
Future Experiments

• Characterize new vacuum tank
• Temperature stabilize vacuum tanks
• A Super Invar cavity has been made using silicate
  bonding
• A CFRP spacer will be made by the University of
  Birmingham
• SiC cavity with hydroxide bonded mirrors
• Cavities will be tested to determine the
  dimensional stability of each material and
  bonding process

Super Invar cavity with silicate bonded mirrors
Supported by grant APRA04-0095-0007
10

• 2 Zerodur cavities with optically contacted
  mirrors
• Drift of 1 Hz/sec (1 pm/sec)

11

• Pound-Drever-Hall technique used to stabilize
  frequency of the laser
• By measuring the laser frequency, we are able to
  track the length of the cavity
• We then beat the two lasers together and measure
  the resultant frequency with a frequency counter