From: "Rick Baartman" Subject: Re: cyclotron beam dynamics study for UCN Date: Tue, September 4, 2007 3:20 pm To: "Akira Konaka" Cc: "Jeffery Willam Martin" ,schmor@triumf.ca,krab@triumf.ca,dutto@triumf.ca,cymru@triumf.ca,masuda@post.kek.jp,spage@cc.umanitoba.ca,"Nigel Lockyer" I am pessimistic that UCN could share beam time with ISAC in the way suggested in 4.1.3 of your white paper. The reason is that ISAC targets require around 1% stability, as Ewart says. I think the technique mentionwed by Gerardo is feasible, but only for sharing with a less fussy user like muSR. In that case, it would not be worth the added operational complication, since it would only run for a small fraction of cyclotron uptime. BL4N as presently envisaged would contain a new high current proton dump. I believe the simplest solution for UCN would be to locate near this new dump. The 1min/3min duty cycle would be programmed at the ion source if UCN is sole user, or created with a kicker that deflects from the dump to UCN if sharing time with 2C and muSR. A way for UCN to share beam time with ISAC would be to extract 2 spatially separated beams down BL4N, one for ISAC and the other switched between the proton dump and UCN. It is not presently known whether this could be done with sufficiently low spills. Since the extracted emittance is small, it is not difficult to design a beam transport system with the necessary acceptance to carry both beams: the usual problem is not the beam core, but the halo created by large angle scatters in the cyclotron and especially the stripper foil. So it would be necessary to collimate the extracted beams in the cyclotron vault. We are currently investigating thin stripping foils; if we continue to use the traditional ones, the collimation needed may be too much. -- rick baartman