Feedback status shows BAD-MEAS

The normal cause of a status of BAD-MEAS (the status can be seen on the LOOP STATUS DISPLAY or the SCAVENGER ENERGY LOOP SUMMARY display) is that the energy is too far off so BPMs EP01 185 and 186 give no readings. If you know this is the case then skip the next paragraph.

Hit DISPLAY VECTOR on the FFBK SELECT PANEL until it displays a measurement vector which is not all white (i.e. mostly green and red). Items not displayed in green are considered to be bad measurements by fast feedback. For this particular loop if there are more than two bad measurements then the loop will show a status of BAD-MEAS and will do nothing. Note that you have to hit NEXT PAGE to see the whole measurement vector. Presumably there will be more than two non-green lines. If it is BPMs EP01,185 and 186 which are red, probably the energy is too far off so the beam does not reach them. If this is so, then proceed to the next paragraph. A measurement will be red for any of the following reasons.

1. The measurement value is outside the limits set on the MEASUREMENT panel. These are typically set to mm.
2. The calibration for the BPM was bad. This can be checked by going to the BPM CALIB panel.
3. The raw pulseheight (TMIT) is too small. This will happen if you have calibrated the BPMs for high intensity and the intensity is presently much lower.

1. The BPM is HSTA'ed offline on the feedback measurement panel.
2. The BPM is HSTA'ed offline on the BPM diagnostic panel.

If the beam energy is too far off, you must turn off the loop, fix it and then turn the loop back on. In more detail:

1. Change the loop HSTA to COMPUTE.
2. Go to the E+ TUNEUP AND RATE PANEL (available off the E+ SYSTEM INDEX). Assign LI17 LI18 FFPHAS to a multi-knob. This multi-knob adjusts two of the six AMPL's that feedback uses to control (via the fast feedforward hardware) the sector 17 and 18 phase shifters. It controls them in roughly the same way that feedback does and hence the multi-knob adjusts the scavenger beam energy. Note that this knob will do nothing if the loop is in the feedback state.
3. Using a BPM display and the multi-knob, set the energy correctly (so that BPMs EP01.185 and 186 read near zero).
4. Do a DISPLAY VECTOR and make sure it now shows two or fewer bad measurements.
5. On the same display (which you should update several times) make sure that the ENERGY SCAV state reads near zero (within about 200 MeV). If it doesn't, and the energy still looks good on the BPM display, you should either change the ENERGY SCAV setpoint (from the STATE panel) to the measured value, or save a new gold orbit (from the GOLD ORBIT panel).
6. Change the loop HSTA to FEEDBACK.
7. Look at the SCAVENGER ENERGY LOOP SUMMARY display. If it shows a GOOD status you are done.
8. If the status is still BAD-MEAS then you are still in trouble. On the summary display check if the FBCK E REQ is up at the same height as the MAX. FBCK E. If it is then you are out of energy headroom and you should go to the above section on that subject.
9. If you are not out of energy headroom and the BPM display shows once again that the energy is too far off, then repeat the above procedure a second time. If it still doesn't work after that then call an expert.