From: "Charles A. Davis" Subject: Re: cyclotron beam dynamics study for UCN Date: Wed, September 5, 2007 8:19 am To: "Rick Baartman" Cc: "Akira Konaka" ,"Jeffery Willam Martin" ,schmor@triumf.ca,krab@triumf.ca,dutto@triumf.ca,masuda@post.kek.jp,spage@cc.umanitoba.ca,"Nigel Lockyer" Hi Rick et al., It would actually not help us "to locate near this new dump". We want to have our UCN source as far away as possible from the alternate dump so as to eliminate the background. Thus it would be better to keep the UCN source in the proton hall if the alternate dump were in a 4N north (ISAC III?) Hall. The shielding of the UCN source (another TNF) would have to be sufficient in any event (like the TNF) to allow some degree of approachability while in operation. The present state of the proton hall shielding supplements this but the present limits are not what should limit us. -Chuck Davis Rick Baartman wrote: > 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. > >