Model March 01 2016

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Several topics were discussed pertaining to the modeling of the machine and/or the setup.

FOPT dispersion measurement versus 30Hz measurement

It has been observed for quite some time now that measuring the dispersion via FOPT yields a significantly different result than using the live 30Hz system.

The 30Hz system uses a 30Hz AC kick. It is adjusted by operations to yield 8mm at IPM1A21 bpm. The FOPT system uses a DC kick. It is 1.5 volts which is then scaled for the energy by FOPT. It takes energy from the system when doing a kick.

One might want to do studies to see if adjusting the FOPT kick to that of the 30Hz system yields the same results.

Separator setup

The RF separators have a slider allowing for adjustment of the RF amplitude by +/- 20 %.

The actual baseline amplitude is given by the total angle in microradians that one has to kick to extract the beam.

This has been setup erroneously in the past. We discussed whether or not eDT should set it by adding up the angles of each cavity in a particular pass and setting the separator to that total angle. No consensus yet whether or not this is the best way to go since

it was mentioned that the RF group was looking at having it done via another mechanism. We will look into it further and plot the course of action.

2R optics errors

There is still an optics error in the 2R region leading us to adjust 2R02 by 30 % or so. Quadrupoles in this region were checked multiple times. However this was done with a gaussmeter probe and may not have been sensitive enough to detect the error if it is due to a miswiring of the coils. A similar issue for the BT03 quadrupole was also missed with the probe and yet discovered when physically checking the connections at the patch panel.

Previous beam based differential orbit measurement in this region did not result in a clear outlier. We could not attribute the error to a single qua, hence the suspicion it must be miswiring. During the summer down, I will write an ATLIS to ask for a systematic check of the connections, using the same technique M. Tiefenback used for the BT03 quad.

Compton dipole setup

the current Optics decks have the compton dipole unpowered. It was done on purpose to avoid having the dipole loaded and turned on when we actually want to go straight-thru. We are considering to instead have the decks reflect the beam path going thru the chicane and have eDT load that BDL to setpoint 1 of the dipole.

Since eDT does not turn magnets off, it will still be setup in straight-thru but we will have the needed BDL in setpoint 1 when wanting to setup through the chicane. Setpoint 2 can be used as the zero field setpoint. We will check that this convention adheres to what is already the case elsewhere in the machine.


Scheduled to be released with the sqrt(2.0) bug fix as well as a number of other improvements.

Fast feedback in Hall A

It is likely underpowered for 11 GeV. The coils were not upgraded to run at twice the amperage when migrating from 6 to 12 GeV.

The 2L26 RF vernier is tripping the C100 zone as well. Concerned parties have been contacted to assess and hopefully fix it. I will (Yves) see if there is any benefit in moving some of the FFB correctors to a better location.