1. Newtonian Noise Mitigation by Using Superconducting Gravity Gradiometers
Ho Jung Paik Department of Physics University of Maryland ICGAC-XIII, Seoul July 4, 2017

2. NN for laser interferometers
Advanced laser interferometers will be limited by the NN due to Rayleigh waves and infrasound waves below 10 Hz.
NN dominated by Rayleigh waves
One way to reduce the NN is by going underground.
At z =  200 m, NN is reduced by 36 at 10 Hz and 3 at 3 Hz.
KAGRA: 200 m depth, ET: proposed to be at m depth.
For surface detectors, data from seismometers are used to estimate NN.
Apply coherent noise cancellation by Wiener filtering.
Paik

3. NN mitigation by using SGG
Sensitivity requirement:
Interferometer test mass
Correlation requirement:
SGG test
masses
Beker et al., GRG 43, 623 (2011)
Locate an SGG with only vertical arm under each test mass.
Paik

4. SGG with 4-m arm NN mitigation by using SGG appears feasible!
SGG with only vertical arm ( = 4 m, M = 1.5 ton, T = 4.2 K) is located under each interferometer test mass.
SQUIDs are further cooled to 0.1 K to reach 10 noise level.
Seismic noise is rejected to one part in 109 by CM rejection.
Scattering of waves off underground cavity and NN from local sources must be examined in comparison with conventional approaches.
Parameter
SGG
Each test mass M
1.5  103 kg
Arm-length 
4 m
Antenna temperature T
4.2 K
SQUID temperature TSQ
0.1 K
DM quality factor QD
107
Amplifier noise number n 10
Detector noise Sh1/2(f )
2  1020 Hz1/2
NN mitigation by using SGG appears feasible!
Paik