N. Yamamoto briefly reported a progress of new final focus system with longer L*, which is a case of L*=4.5m + 25cm. He could optimize a vertical beam size at IP. However, a horizontal beam size became 10 times larger because of increasing dispersion, whereas the Pantaleo's optics(L*=4.5m) has 2 times larger horizontal beam size than that of linear optics. This is probably due to weaker sextupoles. Therefore, further optimization of sextupoles must be necessary.
We discussed on the beam dump. TESLA group designed a beam dump of 1.2m diameter and 10m long, which contains pressurized water at about 9 atm. . In order to avoid boiling of water, a beam train should be deflected in circle of r= 5 cm, where a temperature rise should be less than 40 deg., i.e. 50 deg. to 90 deg. . The water dump should be the best choice for less radioactivity and good neutron absorption. We shall design a dump for JLC beam consulting radiation safety group at KEK. The dump is located at 200m from IP and it is separated by 6m from an incoming beam.
The next meeting will be on 21 Feb. (Thu.), 2002 13:30 - 15:00 at 3 gokan, 725.