 |
 |
Dear Glen, I have a comment about the idea to remove the upstream energy spectrometer. The chicane of the upstream energy spectrometer has 3 roles. 1) Energy monitoring to abort the beam, when the beam energy drop was observed. Therefore, the energy spectrometer should be arranged to the upstream of the beam abort line. 2) Beam line shift from original beam line to detect the signal of laserwire. Therefore, we must shift the beam line more than 10mm (the design is 20mm), when the inner diameter of chamber was 20mm. 3) Spent electron measurement for polarimeter. It is important to measure the large energy spectrum to evaluate the polarization. When we use the 20mm diameter of the beam pipe, the chicane with 20mm dispersion can be measure the spent electron with the beam energy of E<2*Ebeam/3. On the other hand, the energy range was reduced to E<Ebeam/3 for the 5mm dispersion chicane. The chicane with large dispersion is better for the polarization measurement. Furthermore, we can measure the dispersion with the beam tuning dump in beam commissioning by putting the polarimeter to the upstream of the tuning dump line. I think the chicane with 20mm dispersion for energy spectrometer and polarimeter is important for ILC BDS. Furthermore, I have a question of your energy collimator design. the dispersion, generated by bending magnet is roughly defined to "eta=L*theta/2". The half length of ILC energy collimator is roughly 200m and the total bending angle to the center is 1.25mrad. The evaluated dispersion by the simple formula is 125mm. The dispersion of the energy collimator is 150mm, and number is consistent with the rough evaluation. In generally, when the length of energy collimator is changed, we must increase the total bending angle to make same dispersion at the energy collimator. How to increase the dispersion at the center of the energy collimator? If the bending angle was increased to make the dispersion large, the tunnel layout also must be changed. with best regards, Toshiyuki OKUGI, KEK ----- Original Message ----- Thanks Toshiyuki, I have added a statement that the reduced vertical beta function may adversely impact the collimation efficiency and possibly increase wakefield sensitivity under case 2 and in the summary. Before we would implement this change (which hopefully we wonąt need to), we would obviously have to consider this point in light of a requirements document for the collimation system, which we would hopefully have had time to write by then. Cheers, - Glen. ######################################################################## Use REPLY-ALL to reply to list To unsubscribe from the ILC-BDS list, click the following link: https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=ILC-BDS&A=1 ######################################################################## Use REPLY-ALL to reply to list To unsubscribe from the ILC-BDS list, click the following link: https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=ILC-BDS&A=1