> On Apr 2, 2015, at 7:58 PM, Toshiyuki Okugi <[log in to unmask]> wrote: > > > Dear Glen, > > I think it is possible to reduce the length of energy collimator > for the horizontal emittance growth by the Synchrotron radiation. > > The problem is, however, the vertical betatron collimation is still remained. > The gap of the vertical collimator is better to design as large as possible > in order to reduce the wake effect and to reduce the tolerance of orbit adjustment. > > In my design, the main vertical betatron collimation > is also assumed to the energy collimator section (highest betaY), > and the vertical beta function at energy collimator is designed to betaY=4000m > and the phase advance in between energy colliator to QD0 was adjusted > in order to increase the collimator gap of the vertical spoiler. > > In present design, the vertical full gap hight is about 2mm, > and the gap is comparable to the horizontal one at betatron collimator section. > > When we reduce the energy collimator length, the vertical beta function is also reduced (in generally). > Therefore, the vertical beta collimation also should be set at betatron collimation section, > and the gap of the collimator will be reduced to about half to the present one. > > This is just a comment for this issue. > > Sincerely, > > Toshiyuki OKUGI, KEK > > > ----- Original Message ----- > Dear colleagues, > > As reported in the recent global timing working group report (EDMS D1097725), the BDS group was invited to look into ways to cut ~150m from the length of the positron system (optionally also from the electron side) to fix the timing mismatch between e- and e+ beams which exists in the current TDR lattices. There is a change request in process looking at increasing the linac length by ~1.5km (CR4 - EDMS D1092915) for additional reasons which will fix this problem if that is approved, but here Nick has also asked for a quick look into the possibility of shortening the BDS as an input into these discussions. > I think the most obvious candidate is for shortening the energy collimation system, which comes mainly at the cost of an additional 2.1% horizontal emittance growth and 220 MeV energy loss for the 1 TeV machine (negligible impact for 500 GeV). > As a suggested response to these requests, please find attached short note. Let me know if you have any comments or other suggestions on this topic. > > Best regards, > > - 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