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Dear Okugi-san, Thank you very much for sending us very interesting results. I have comments on the CAIN/GP comparison and the RDR parameters etc.. (1) CAIN and GP calculations have been checked well before the TDR publication as seen in the excel file ( appended ). They are summarized below; ---- Relative Lum : CAIN/GP (w/ waist shift) TDR : Ecm = 250 500 GeV The ratio 0.99 0.99 Also, 1% luminosities agree within 1%. ---- However, there are differences between their results and the TDR values as ; Relative Lum : TDR/CAIN(GP) for TDR (w/ waist shift) TDR : Ecm = 250 500 GeV The ratio 0.95 1.06 (2) IP RDR parameters ( Ecm=250 and 500GeV) are listed below. ---- RDR : Ecm =250GeV Nb=2625 EmitX = 10um, EmitY=56nm BetaX = 22mm, BetaY=0.5mm Lum=0.77E+34 w/o waist shift calculated by GP RDR : Ecm =500GeV Nb=2625 EmitX = 10um, EmitY=41nm BetaX = 20mm, BetaY=0.4mm Lum=1.93E+34 w/o waist shift calculated by GP ---- Finally, I am also very interested in the case of the BBA resolution of 1um as Glen asked. Could you simulate in such case ? Best regards, Toshiaki Tauchi On 2015/01/08 14:36, "Okugi, Toshiyuki" <[log in to unmask]> wrote: > Dear Glen, > > A happy new year, > > I continued the beam tuning simulation, > and I will show some results of the beam tuning simulation. > I hope this will be the answer to your questions. > > At first, since many parameters were change in between RDR and TDR, > it is difficult to evaluate their performance > only to be compared the tuning simulation to the TDR and RDR design > luminosities. > > RDR luminosity was not included the effect of the waist. > On the other hands, TDR design was included the effect of waist shift. > Therefore, there are luminosity margin for RDR luminosity, and TDR are not. > Furthermore, number of bunch, emittance are different. > > Furthermore, > the simulation results for Gnineapig (TDR) and CAIN have discrepancies for the > luminosity evaluations > (We should do the systematic studies for the simulation codes to evaluate the > design luminosity). > > Since the luminosities for the tuning simulation were based on CAIN, > I believe the achieved luminosities should be compared with the luminosities > by CAIN simulation. > I put the beam tuning simulation result for same incoming beam parameters to > wiki page. > > http://atf.kek.jp/twiki/bin/view/Main/ILCBDSOpticsStorage > > In the wiki page, > I also put the beam tuning simulation with several quadrupole errors. > When I changed the quadrupole strength error to 1e-4, > the results of the tuning simulation were not changed so much. > > Therefore, I changed the amplitude of the sextupole field errors to 1e-4. > The results were improved, especially for the final horizontal beam size. > The horizontal beam size was not decreased, even when we increased the number > of iterations. > > This is the result of the beam tuning simulation. > > In present tuning, > we can minimize T322, T324, T326, T344, T346 and T366 for vertical direction. > But, we don’t have the tuning knobs for T124 and T146 for horizontal > direction. > I believe that this is the reason why the horizontal beam size limit for the > beam tuning simulation. > > If my assumption was correct, > we must decrease the requirement of the sextupole errors for quadrupoles > in order to focus the horizontal beam size at IP. > > We should continue the study to evaluate the tolerances of multipole errors > with the tuning simulation. > > Sincerely, > > Toshiyuki OKUGI, KEK > > > ----- Original Message ----- > Dear Toshiyuki and all, > > First, happy New Year to everyone! > > Thank you Toshiyuki for this summary of the optics and tuning work you have > done. > > The tuning performance seems not to be sufficient yet with the TDR parameters, > especially since adding more realistic features (dynamic errors, having to > tune e- & e+ beam lines simultaneously, use realistic lump signal input etc) > will only degrade this expectation. Here are some thoughts I have on how to > improve the tuning performance that might be worth considering: > > * Use 1e-4 instead of 1e-3 magnet strength errors, I have found in the past > this can make quite a difference and according to magnet design experts is an > achievable level of accuracy. Although, at some point in the future it will be > good to only specify this level of accuracy where needed. > > * Use a more advanced BBA / beam steering algorithm which gives a smoother > beam trajectory and smaller dispersive emittance growth (e.g. DMS). > > * Is 10um BPM-magnet BBA as good as can be done? What can be done to get 1um > or below, especially for the Sextupoles? With 100-nm level accuracy from > cavity BPMs, I would expect better possible performance. Although in reality, > 10um is about the best performance I have ever seen from the ATF2 BBA process > even with the cavities- this would be an excellent program for somebody to > consider trying to experimentally determine the BBA performance limits, > especially as it seems an important contribution to the BDS tuning > performance. > > * What limits the luminosity performance? Other second-order terms, or > third-order terms? Can we generate knobs to target these, using Octupoles if > required? Are these generated by how far the sextupoles must be moved, can > this effect be mitigated by more reliance on non-sextupole mover based > corrections (upstream dispersion correction by bumps or quad/skew-quad in > dispersive region solution, using skew-quad in non-dispersive region for > coupling correction)? > > In the past (for the RDR), we had the idea of emittance growth budgets for > each region, with 6nm allowed for the BDS- i.e. with a design 40nm, the BDS > could deliver design luminosity including all emittance degrading effects at a > 90% confidence level if supplied with a beam with 34nm vertical emittance. We > should eventually aim at providing a similar statement for the TDR. > > Best wishes, > > - Glen. > > >> On Dec 22, 2014, at 12:21 AM, Okugi, Toshiyuki <[log in to unmask]> >> wrote: >> >> Dear Glen and all, >> >> I summarized the ILC-BDS optics with (QF1 L*)=9.1m, (QD0 L*)=4.1m in >> http://atf.kek.jp/twiki/bin/view/Main/ILCBDSOpticsStorage >> >> The beam tuning simulation said >> the beam tuning results for the optics with (QF1 L*)=9.1m and (QD0 L*)=4.1m >> were almost exceeded the RDR design luminosity, when we assumed the RDR beam >> parameters. >> (The RDR luminosity was not assumed the waist shift.) >> >> But, when we assumed the TDR beam parameters, >> the achieved luminosity in the simulation was smaller than TDR design. >> However, the situation was almost same even if we use the smaller L* optics. >> >> Sincerely, >> >> Toshiyuki OKUGI, KEK >> >> ######################################################################## >> 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 > ######################################################################## 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