1. Seismometer Development for the 1TeV Linear Collider
Josef Frisch, SLAC

2. The 1TeV Linear Collider
500 GeV electrons and positrons
Collide at Interaction Point
Want small beam spots to maximize number of interactions.
Spot sizes ~ 1 nanometer.
Final focus magnet relative positions must be stable to ~1nm

3. Detector – Magnets supported in ~1 Tesla field

4. Beam-Beam interaction provides low noise measurement at beam rate of 120 Hz.
High gain below a few
Hz.
Need stabilization above
1 Hz. One option is to use
Seismometers and feedback

5. Seismometer Requirements
Integrated noise above 1Hz, <1nm.
(better preferred).
Flat response to ~50Hz.
Can use compound sensor with piezo-sensor if needed
Relatively compact size: ~10x10x20cm
Operation in strong magnetic field

6. Test sensor parameters
Operation Feedback Seismometer
Test mass grams
Suspension frequency 1.5Hz
Mechanical Q >100
Theoretical thermal mechanical noise <1.5×10-10M/s2/Hz1/2.
Capacitor Sensor gap ~300 microns
Theoretical electronic noise < thermal noise
Vacuum <few microns

9. Results to date
Tests done in noisy lab – insufficient actuator strength to close feedback above a few Hz. (Would be ok in real application)
Noise (from correlation with STS-2) <5nm/s2/sqrt(Hz) at 1Hz.
1/f noise corner ~1Hz.
Meets our requirements – but would like better.