Minutes from Beamdynamics meeting

Daniel said that the EUROTeV contract is at DESY waiting to be signed. Until the contract has been signed some institues cannot contract people and some cannot even advertise.

Takao showed a comparison of Placet and SAD simulations of the phase space ellipse at the IP for two different energies (1495/1500). There was a small difference between the simulations that may be caused by a difference in how multipoles are implemented.

Javier showed that he has calculated 1st and 2nd order matrix elements for the FFS and 1st, 2nd and 3rd order elements for the CS and CS + FFS. He has done this with MAD taking SR effects into account. For the FFS the phase space ellipse position predicted from the matrix elements agree well with Placet-simulations for different δ-values. The horizontal shifts of the ellipses are significant. See plots below. Javier then showed that the agreement was good for the CS as well. The ellipse position seems to be a 3rd order effect of δ.

It was proposed that a movie of the phase space ellipse along the line should be created. Daniel and Javier will take of this. Frank mentioned that he thinks it might be possible to correct the 2nd order effects without changing anything else. Finding a knob to do this would be very useful.

Peder said that he has been rewriting the code for simulations of luminosity-tuning bumps. This has been done in order to make the simulations faster and the bumps more stable, but also to get a more modular code. It was also mentioned that Peder should present his work on luminosity tuning bumps during some CLIC-meeting.

Helmut reported that he has done some comparisons of the MAD8 and MAD-X SR calculations. This was done for a single quad. The MAD-X calculations are in principle identical to the ones in MAD8 but he had found some problems for MAD-X though.

At this point Daniel pointed out that he wants to go on with SAD, MAD and Placet instead of starting with MAD-X as well. It was mentioned that MAD-X is more powerful then MAD8 when it comes to matching, but for this purpose SAD could be used as well.

Maxim said that he is trying to improve the dispersion correction in the damping ring. This could be done by putting the bpm:s as close to the sextupoles as possible, possibly even attaching them to the sextupoles (to reduce the relative offset) or by increasing the number of correctors. He has also been trying to use MAD to track a beam through a wiggler. He has sent the resulting MAD-file to ??? in order to get it verified. Maxim will also try to contact Winni Decking about sixtrack.

Daniel showed that he had run some new simulations with Igors PETS-model. These simulations made it clear that mode 4 was the one blowing up the beam. Igor has created a new model with mode 4 damped which Daniel had also simulated. The beam is no longer blown up as much, but mode 5 makes the beam grow a bit. With mode 5 removed the beam is not blown up at all.

Helmut proposed that there should be some disk space for common files like lattices, input files etc. According to Frank a webpage with the lattices already exists. Daniel said that common disk space like this could also be helpful for sharing of common codes. A CLIC-account like this already exists, but it is apparently already filled with non-CLIC data.