Set up common tuner loops, vector sum display

Study feedback response vs. cavity detuning. First, adjusted on resonance
for optimal feedback phase.

cav1_set1 - open loop response, cavity 1, -0.92 kHz
        G: 0.5068
    sigma: 2.0672e+05
       wr: 3.1395e+09
        x: [0.5068 2.0672e+05 3.1395e+09 9.7105e-07 -351.8539]
      tau: 9.7105e-07
      phi: 0.2559
        Q: 1.5188e+04

cav2_set1 - open-loop response, cavity 2, -1.08 kHz
        G: 0.5070
    sigma: 1.9880e+05
       wr: 3.1395e+09
        x: [0.5070 1.9880e+05 3.1395e+09 9.8905e-07 -383.2568]
      tau: 9.8905e-07
      phi: 1.0033
        Q: 1.5792e+04

err_set1  - closed-loop response

cav1_set2 - Full span, showing parasitic mode
cav2_set2 - Same, cavity 2

Set load angle offsets to 10 deg.

cav1_set3 - Detuned to -4.27 kHz
cav2_set3 - Detuned to -4.09 kHz

err_set2 - closed-loop response

Set load angle offsets to 30 deg.

cav1_set4 - Detuned to -12.08 kHz
cav2_set4 - Detuned to -11.43 kHz

err_set3 - closed-loop response, looks fine

Set load angle offsets to 60 deg
cav1_set5 - Detuned to -37.71 kHz
cav2_set5 - Detuned to -34.45 kHz

err_set4 - starting to see some peaking

Set load angle offsets to 70 deg
cav1_set6 - Detuned to -65.08 kHz
cav2_set6 - Detuned to -55.71 kHz

See phase of -77 for cavity 1 and -75 for cavity 2 at RF. Set load angle for
cavity 2 to 72 degrees

cav2_set6a - Detuned to -62.04 kHz

err_set5 - Peaking around 3 dB at -150 kHz

Set load angle offsets to 80/82 degrees
cav1_set7 - Detuned to -164.78 kHz
cav2_set7 - Detuned to -171.00 kHz

Lowered setpoint from 0.03 to 0.02 to avoid excessive reflected power

err_set6 - Peaking 6 dB at -210 kHz

Go back to on-resonance tuning, re-adjust loops

Direct loop (integrator off, loop gain 0.5) shows margins of -60 and +90,
optimal -165 deg.

Integrator is stable at a gain of 0.001 from -85 to +20, optimal -32.5

Rechecked - integrator best at 0, direct set to -165.

The loop is stable at detuning of 170 kHz, expected in operation 
(1.2GeV, 1MV, 250 mA) - 115 kHz.

