THOMAS JEFFERSON NATIONAL ACCELERATOR FACILITY
ACCELERATOR OPERATIONS CREW CHIEF SIGN IN FORM
Date : 02-19-20
Time : 23:39:43
Day : Wednesday
Shift : Owl
Crew Chief : Surles-Law
Program Deputy: Nissen
Team : X
Arm : Garcia
Designated SSO: Anthony
Operators : Anthony, Garcia
This stamp certifies that the above Crew Chief has read/reviewed/received the following:
Once again, grabbed the MBC2T09H corrector and cheated it left again which helped reduce Compton Rates (Figs 1 and 2). I didn't want to keep leaning on that corrector and eventually it may be put back.
After reviewing the Hall A Steer Up Screen, I chose to examine the affect of MBC1C06 on Compton Rates. Bingo!!! With a -80 G-cm change, the Compton rates were nearly reduced by 50% (Figs. 3 and 4).
Backed out of most of the MBC2T09 changes from earlier while using the 1C06H to tweak Compton Rates when needed (Figs 5 and 6).
Resulting orbit is shown in Fig. 7.
We started getting mismatch alarms in the alarm handler for MQK3C19.
Around 21:07 Magnet current got unstable, we were getting repeated alarms for this magnet.
Crew chief advised that we cycled the magnet.
Magnet was cycled.
Currently have not had any new alarms in the alarm handler for this magnet. However, there is still a deviation from set point.
Will continue to monitor.
Maybe this is where Hall A personnel are getting confused about the FFB system. #1 The FFB bpms on IOCSE9 can be placed in Normal SEE mode or FastFeedback mode, #2 the FFB RF can be turned ON or OFF (this is a signal that feeds the vernier inputs of SL20 cavities 1 thru 8). #3 The FFB system as whole can be Turned ON or OFF. Then there are the areas of using FeedForward and the Slow Lock Areas.
please see elog entry 3787575.
(Hall A or Hall C) Energy Position modulation System RF Vernier output by design is not
permitted electrically to work while (Hall A or Hall C)FFB RF is turned on. FeedForward has nothing to do with this.
Hall A requested the Compton Rates to be lowered. Adjusted MBC2T09H, first positively which seemed to work some when Hall C was off, but then negatively after Hall C beam returned. Compton Rates were lowered 30% (Fig. 2), at the time, Hall A was running without FFB on so orbit corrections were not done. Ion Chamber rates seemed to decrease as well (Fig. 3). Hall A said they can run overnight with these Compton Rates.
Fig. 1 shows quantitative adjustment of MBC2T09H.
Fig. 4 shows 2T->Hall A BPM Orbit after the change.
So it turns out FF-off with FFB on ALMOST works....the data initially looked great....until we realized our beam-modulation (which pauses FFB) and is supposed to dither SL-20 the energy Vernier fails. Beam modulation appears unable to dither the SL-20 energy coil when FFB is ON, paused, and FF is off. Other combinations attempted were FF-DAC OFF/FF-ON, FFDAC ON/FF-OFF, FFDAC-OFF/FF-OFF....and finally we tried letting OPS turn on FF but like before this morning, that was unsuccessful. The only thing that allowed dithering of SL-20 was to turn FFB off completely.