Target Status

CM19 RAL

October 2007

P J Smith – University of Sheffield

Summary• Bearing Wear – We have made some progress here and we now

have a possible solution for a January Installation.

• Target Electronics – One complete set to go into ISIS. (Maybe a few more modifications before installation but these are minor issues).

• Target Installation Issues / Infrastructure Installation at RAL – Progress here has been slow. It has been difficult to get the momentum going although it looks like we are finally making some headway.

Top Bearing

Bottom Bearing

Magnets

Coils

Water Cooling

Simplified Diagram of the Internal Mechanics

Bearing Wear• As was reported at the last collaboration

meeting we were having problems with the bearings wearing out extremely quickly. See June talk for more photos

2 Problems:

The bearing wear makes the target unusable. (problem for us.)

The bearing wear was producing lots of dust. (problem for ISIS -> therefore problem for us!)

• At the last collaboration meeting we were at the following juncture:

Ceramic Bearings wore out within ~100,000 actuations

Had much better success with brass bearings but even so these were wearing out within ~250,000 actuations

Bearing Wear

• We tried to use a bearing based upon ruby bearings – this didn’t even last for a day!(<86,000 actuations)

• Next tried to use leaded bronze. This was a very good material and worked well for ~3 million pulses with very minimal dust production.

Bearing Wear• Given the ‘success’ of these bearings we approached ISIS to ask

about using leaded bronze bearings on the target mechanism in ISIS.

• There was an emphatic NO to any dust producing bearings.

• ISIS are very concerned with metallic dust getting into ISIS and damaging the synchrotron components. Notably RF cavities and ion pumps.

• Catch-22. We cannot make bearings that do not produce ANY dust.

Bearing Wear

• The next material that we have tried, and are still testing, is DLC (Diamond Like Carbon or Diamolith).

• It is a “Plasma Enhanced Chemical Vapour Deposition” (PECVD) process that deposits a material layer that is about 3-5um thick.

• We have presently only got one bearing, the top bearing, DLC coated and the target shaft. (We continued running on a leaded bronze for the bottom bearing)

• We have also increased the surface area over which the bearings operate. Moved from a curved bearing surface (point contact) to one that is flat and bears over ~5mm.

Bearing Wear

1.25 million Actuations!

Bearing Wear

• We have run the top bearing for 1.25 million actuations. No VISIBLE dust has been produced. However the coating did look as though it was wearing where there has been contact between the bearing and shaft, but it hadn’t worn through to the underlying metal.

• Wiping the bearing/shaft left a smear of material on the wipe.

• No measurable mass change in the bearing. (weighed to within 1 milligram)

• We are now having a full set of bearings produced to rerun on DLC bearings only. - We want to eliminate the possibility of any dust produced from the lower bearing (currently leaded bronze) affecting our results.

Bearing Wear• Continuing to run the first DLC bearing to see how many actuations

we can make before the coating wears through.

• Questions:

- How long will the material last?- Can we have a thicker layer of DLC be applied to our bearings?- Will ISIS accept this material?

- Will also consider other bearing materials i.e. Loaded Kapton but we are unlikely to have the opportunity to test this material before next year.

DLC Run Target – Minimum Dip Depth

Positioning System Recalibrated.Loose Magnets Fixed

Bearings removed wiped & replaced

Target Electronics

• Much work has been done on the target electronics to get it ready for ISIS.

• All electronics are now enclosed.

• Much documentation written (but much more to do!)

• New controller unit that has a few new features and will interface with the MICE DAQ.

• Aim is to have 2 sets of electronics so that we can continue developing in Sheffield when these units are installed at ISIS.

Installation• I will be brief some of the installation issues as Chris Booth will be

giving a MICO talk about this.

• Problems that we needed to solve for target installation into ISIS can be broadly broken down into three categories:

– Removal of the old target.– Approval to put the new target into ISIS.– Having the infrastructure in place to put the target into ISIS.

• We have been having many meeting with people from both RAL and Daresbury to get these issues sorted.

Removal of the Old Target• As you may recall we ran some tests with a prototype target on the ISIS beamline last

November. That target mechanism still remains on the beamline and needs to be removed.

• Cannot just go up and unbolt it! To remove the target we have to go through a procedure called an RPA ‘Radiological Protection Assessment’ and have this cleared by health physics.

• We have spent much time and discussion trying to get a good RPA procedure in place.

• It is our/RAL’s intention to use the removal of this target (which shouldn’t be hot) as a practice run to ensure that we get the removal procedure correct for future target removal when the target is likely to be very hot

• We are planning to have the infrastructure in place (documentation and equipment) to try and remove the target in November. This is dependent upon being given a suitable window of time. If this is not possible then the current target will have to be removed during the Christmas Shutdown

Target Approval

In order to use the target mechanism we need to convince ISIS that the target mechanism is not going to cause any problems for ISIS.

• Bearing Approval .• Drawing Approval / QA of components.• Risk Assessments.• Stress Analysis of possible failure modes. (W. Lau)

We are in the process of ensuring that the relevant ISIS personnel are satisfied with what we are doing.

Biggest perceived risk here is with the bearings. Will they be approved? How long will they last? Estimate ~2 million actuations

InstallationThere is a significant amount of infrastructure that needs to be in place for the target to operate.

~1500m of optical fibre links and several hundredmetres of cabling to be run between the MLCR/Synchrotron/ VacuumRacks.

Been a slow start in getting hold of the necessary people to make thishappen but we understand that installation of cable ducting and cabling willproceed soon.

Stepper Motor Control to Raise and Lower Target into beamline & P.S.P.

Daresbury Laboratories are overseeing this as they are familiar with themotor mechanism. P.S.P. is also to be reviewed by them.

Target Mechanism Power Supply

Daresbury laboratories have built a second target power supply and this iscurrently undergoing testing at Daresbury laboratories.

Conclusions

• We feel that we have found a good solution to the bearing problem. Questions remain: How many cycles are these bearings good for? Will it be accepted by ISIS?

• We are trying to ensure that we can satisfy the ISIS acceptance criteria.

• Much of the infrastructure & planning for installation is now coming together.