Chris Booth & Paul Smith Sheffield 16 th August 2007 MICE Target Installation

Actuator Actuator continued running on leaded bronze bearings for several weeks. ~3 million pulses achieved. This bearing material appeared to solve our ‘mechanical’ problem with a ‘small’ amount of dust production ~ less than 0.01g. Unfortunately: Leaded Bronze is not ‘liked’ by ISIS from a radiological point of view. More importantly we have had a statement from David Findley who feels that we really need to eliminate the dust problem as metallic dust could damage components in ISIS.

Chris, > > Following receipt of your on Friday we have had further > discussions here about the MICE target and the dust it generates. The > bottom line is that we are really very unwilling to put into the ISIS > synchrotron a piece of apparatus that poses a risk to ISIS when the > apparatus could be redesigned to remove the risk. > > So that you can perhaps better appreciate our concerns, I've attached a > photo of Straight 7 of the ISIS synchrotron showing the MICE target in > the foreground. Two things you can also see in the photo are the left > hand side of the top of an ion pump (below the MICE target) and one of > the RF cavities (towards the top of the picture, between the lighter > green quadrupole doublet and the darker quadrupole singlet). Both of > these may be badly affected by metallic dust finding its way into them. > No doubt we could change the ion pump when it failed, but it would cost > us several days to pump the synchrotron down again, and the problem > would recur. The RF cavity contains two accelerating ~14 kV gaps, and > metallic coatings from dust on the insulators could cause severe > problems, both in the cavity itself and in the high power RF drive > system which could damage itself trying to compensate for the degrading > insulators, and repairing the damage could take at least a week. > > Perhaps these downtimes don't sound too bad to you, but several days or > a week off to change an ion pump or repair an RF cavity in the middle of > a user run is a huge black mark against us in the eyes of our users - an > extra week off would bring our availability down from our typically > acceptable 90% to an unacceptable 72%. And then of course there would > be the financial cost of the repairs as well. > > I really think you have to eliminate the dust. > > David Details…..

Actuator Clearly this has put us in a predicament! We are presently having a new material, Diamond Like Carbon or DLC, coated onto both a shaft and a bearing. The testing of this material was going to be part of our ongoing development but it now looks as though we are becoming ‘reliant’ upon this material working to give us a solution that will allow us to install within the next few months. This is not a situation we feel very comfortable about. With the current shaft design we can only coat the top bearing. We will need to redesign and manufacture both the shaft and the bottom bearing to enable DLC to be coated onto both bearings. A test shaft and bearing has been sent off and upon receipt of the DLC coated shaft (next couple of weeks) we will start to test this new material.

Actuator A couple of points: Because this is a material is a very thin coating (5um) we will need to test the actuator to at least the number of actuations that we intend to use in ISIS. If it wears through after ‘n’ million pulses then we will be producing metallic dust again! We need to ascertain what ‘n’ can be achieved. If the DLC material works this is going to take a long time. (~ 2 weeks for every 1 million actuations.) We do not believe that we will totally eliminate dust production. Two dry surfaces rubbing together will clearly produce a certain amount of dust. Whether small amounts of dust will continue be an issue if it is non-metallic is unknown. This issue clearly needs to be discussed with ISIS personnel.

Installation As Chris mentioned in the last MICO talk we were having difficulty in finding the right people to talk to at ISIS to proceed with the installation. We now have a list of the right people and we have had some short discussions with some of them. Steve Warner is really our ‘King Pin’ in terms of getting things done but we are waiting for his return off of A/L! Next week Daresbury are setting up a meeting with Steve Warner at RAL at which I (P.S.) will be present. It is intended to use this opportunity to discuss the work that needs doing and hopefully to get some realistic schedule in place. (Cable wiring and routes, motor controls etc.)

Target Removal In order to install the new target we will need the old target removing! To remove it we need to have a health physics assessment and have an RPA (Radiological Protection Assessment?) in place. We have drafted an RPA but we need to discuss this further with Paul Wright? Hopefully we will be introduced to Paul Wright next week when we come down to meet with S.W. and the engineers from Daresbury.

Conclusions Realistically, as we can no longer use the leaded bronze bearings and because we need to test the DLC thoroughly (which will involve a target shaft redesign if we are to use) then it is looking unlikely that we will be able to install the target during the short November shutdown. All cabling and other target infrastructure still needs installing at RAL– hopefully we will make some headway with the installation schedule over the next couple of weeks. The old target needs removing. We need to establish contact with the right people and get a good RPA in place. A good RPA procedure will be become even more important for future target removal as SP7 is likely to become a very ‘hot’ area.