Minutes from Beamdynamics meeting

Daniel started by informing about the EUROTeV phone meeting the 19 January. Most of the invited participated. For the minutes of the meeting follow this link: Minutes of the EUROTeV phone meeting 19.01.05

Tour de Table:

Takao showed new plots of the bandwidth at the IP calculated with SAD. This time the effect of synchrotron radiation was taken into account. For the horizontal plane the agreement between the SAD-simulations and Javier's MAD-simulations was excellent. For the vertical plane there is a significant discrepancy between the results from the two codes. Besides, the MAD results seemed a bit noisy. All the plots can be found in the pdf-file below. Takao also mentioned that he has now learnt how to do particle tracking with SAD.

Frank thought the difference may be caused by problems with the simulations of synchrotron radiation in the quadrupoles. Daniel on the other hand thought the source of the discrepancies might be the bending magnets. Daniel also pointed out that since σ_x is much larger than σ_y, an absolute error could be present in the simulations for both planes, but that it was only visible in the vertical one. It was also pointed out that Stefano Redaelli never found a disagreement like this when he did similar comparisons. On the other hand his simulations also included the collimator system.

Javier then showed a table with the luminosity calculated with and without synchcrotron radiation with SAD, MAD and Placet. He also displayed a few plots of the difference in particle positions as a function of energy between the three codes. SAD and Placet seemed to agree well while MAD gave quite different results.

Javier's and Takao's results (comparisoncodes2.pdf 6.53Mb)

Frank proposed that to go on from here the simulations should be discussed with Stefano and he should also be invited for the next meeting where this topic will be treated. He also pointed out that MAD only take the effect of SR into account at the entrance and the exit of the element. Maybe the elements have to be divided into smaller parts. Daniel proposed that a single SBEND and quadrupole investigation should be performed.

Peder showed the results of simulations of a luminosity-tuning bump using a laserwire as a tuning signal instead of the luminosity itself. He also showed the corresponding simulations performed with the luminosity as a signal. In both cases only three bumps were used and new simulations with more bumps should be performed. Another important step to take is to try to orthogonalize the knobs in order to make the tuning more efficient.

Laserwire-tuning (Laserwiretuning.ps 21kb)
Luminosity-tuning (Luminositytuning.ps 28kb)

By comparing the two plots it is clear that using the laserwire signal is almost as efficient as using the luminosity itself. It was pointed out that it would be helpful with a schematic drawing/explanation of the luminosity-tuning bumps and the use of the laserwire scanner. Daniel mentioned that he might have something like that.

Daniel wound up the meeting by telling that the advertisments for the EUROTeV fellows (particularly the one of Helmut) are now on the EUROTeV webpage. He also said that next weeks meeting will be more concentrated on CTF3.