By the Target Working Group Presented by L.Bruno AB/ATB Targets & Dumps Section

1. The CNGS Target T40 Lifting jacks review By the Target Working Group Presented by L.Bruno AB/ATBTargets & Dumps Section

2. The T40 Lifting jacks OUTLINE 1. Introduction to the CNGS target station 2. Functionalities of the lifting jacks 3. Working environment 4. The history of the lifting jacks 5. Summary

3. T40 Layout Schematic Vertical view Shield ( Downstream Monitor, Horn, … ) Proton beam Target enclosure Fixed structure “Handled” structure

4. Beam direction Target enclosure The CNGS Target Station Fixed shielding & steel frame

5. The lifting jacks Alignment table Target magazine Support disks BPKG monitor Beam Focal Point Target enclosure Fiducials Displacement mechanism Base table Shielding The lifting jacks are part oftwo identical displacement mechanisms, each made of a linear guide mounted ontwo coupled lifting jacks. Twohandling frames, a ventilation duct (not shown) andguiding fingers are the other parts of this sub-assembly.

6. The functionalities of the lifting jacks Linear guide Lifting jack The lifting jacks of the motorization allow the adjustment of upstream and downstream positions of the target table in a mechanical range of ±20 mm within a 100µ tolerance. Limit switches mark the start and stop position within ±15 mm.

7. Working environmentThe danger The past experience in the T9 target area has pointed out at the extremely severe corrosion processes occurring in humid radioactive environment. Water and ozone are the suspected causes. Courtesy of S.Rangod

8. Working environmentThe expected conditions Radiation Theexpected dose at the downstream jacks’ location is of ~50 MGy/yr (5x1019 p/yr) Humidity & Temperature In the CNGS target chamber the dew point will be 5°C. The operating temperature of the T40 jacks is R.T.< T< 100 °C.The humidity and thetemperature of the shielding within the target enclosure and of the air will be monitored and logged. An alarm is foreseen. Ozone The ozone-induced corrosion mechanism is complex and not well understood. Synergy with condensed water appears to be a key element.Ozone warning in air starts usually at 0.1 ppm (200µg m-3). In water, dissolved ozone considerably increases the corrosion potential of stainless steel at about 0.5 ppm. The ozone concentration of the target cooling air will be monitored and logged. An alarm is foreseen.

9. The jack’s components The key elements of the lifting jacks are the trapezoidal screw, the nut and the endless screw. The contact surfaces of these parts slide against each other. The picture is taken after the last (third) technical iteration with the provider.

10. The T9 Target jacks Order placed on 28 Nov 1994 The choice of the T40 jacks has been based on that of the T9 Target. Here, the spare T9 jack is shown after cleaning. The trapezoidal and endless screws are made of stainless steel, while the nut is of bronze. The casing is filled with grease. Standard axial/conical ball-bearings were used.

11. The first technical iteration(10 years later…) The first technical choice for the T40 jacks aimed at avoiding all materials whose radiation resistance is not proven. All parts (casing and ball-bearings included) have been asked in stainless steel. Inox 1.4404 (316L) for the screws and 1.4057 (431F) for the nut were asked. No lubrication was requested.

12. Radial inox bearings Nitriding (hard surface) The first technicaliterationNon-conformities After few cycles, the jacks were stuck and the roll bearings damaged by metal particles. It was found that the nuts had too high a roughness, the edges were not deburred, the gear geometry caused interference, the endless screw was made of 431F and the gear ratio was not conformal. PFAFF acknowledged the non-conformity.

13. The first technicaliterationUnsatisfactory cyclic tests (25 Aug 2005) After correcting the non-conformities, one jack was tested under a cyclic load. The resisting torque was too high. Based on a technical discussions held at the PFAFF premises in Germany (19 Sep 05), the decision was taken to lubricate the sliding parts.

14. The second technical iteration(Key elementslubricated by Molykote D-321 R) (25 Aug 2005)

15. The second technical iterationAgain unsatisfactory cyclic tests Lubrication was unsatisfactory: the lubricating layer peeled-off the nut/endless screw after few tens of cycles, well below the 1000 cycles required. It has been found that the endless screw is still not made of 316L as required.

16. The second technical iteration Details of the trapezoidal screw

17. The Third technical iterationStandard material used for the nut The decision has been taken to revert to a standard PFAFF solution for aggressive environments: graphite-loaded bronze nut (powder technology). No grease is used. Successful 20-cycles tests have been performed and the key parts inspected. Sliding occurs where expected. The resisting torque is within acceptable levels. The endless screw is still made of nitrided 431F, the trapezoidal one of nitrided 316L.

18. The Third technical iterationDetail of the endless screw The surface of the endless screw shows deposites of bronze and graphite. Stainless steel axial ball-bearings have been found and used for the nut.

19. The third technical iterationSatisfactory 20-cycles tests The tests were performed by PFAFF manually (i.e. long times needed). The CNGS schedule does not allow longer tests to be performed.

20. Remarks and summary The jack solution we aimed at has not been realized/tested: the material of the endless screw is still not what we asked for. Presently, the CNGS target has been installed with «2nd generation» jacks completely filled by CERN standard molykote. Commissioning tests were successful. Given the time constraints, we have reverted to a «3rd generation»very close to a PFAFF standard, the only non-standard material being 431F for the endless screw. No grease is used. Four «3rdgeneration» jacks have been rapatriated this week to be mounted in the second target assembly. This assembly will be used during operation. We must imperatively install the second target assembly in March !