Introduction to mechanical design of the SPES RFQ Ferrari Luigi, Technical Review, 09/21/15 Design review, 09/21/20151

OUTLINE Main dimension and tolerances Module components Machining considerations Assembly strategy Structural study (horizontal electrode) Thermal-fluid structural study Further works, conclusion and acknowledgement Design review, 09/21/20152

Main Tolerances and Dimensions RFQ Length: ≈7000mm External Diameter: 850mm Internal Diameter: 754mm 6 modules each one long about 1150mm Desired transversal positioning tolerance (X,Y) between electrode and tank of each module ± 0.05mm Expected distance (Z) between electrodes of adjacent modules: 0.15±0.05 mm Desired transversal tolerance(X,Y) between modules: 0.1mm Design review, 09/21/20153 Target profile accuracy per each electrode 0.02mm

Main module components: Tank Design review, 09/21/20154 AISI304L (R p0,2 =180MPa) (forged) 0.03 mm (4*skin depth) copper plating on inner tank surfaces and on tuner holes. 16  8mm deep-hole drilled cooling channels to be plugged after. External apertures are suitable for handling. They will be machined at first. Then inner cylinder wall machining will follow.

Design review, 09/21/20155 Special slot designed for a simple maintainability of the entire RFQ. These long slot permit the complete extraction of the screw without movement of the RFQ modules. Helicoflex® seat near the axis diameter of the screw cause less deformation of the tank. Extreme planes of each module used with machined shims assure a correct relative alignment between modules. Main module components: Tank

Main module components: Electrode Design review, 09/21/20156 Electrode made in brazed OFHC copper 4 deep-hole drilling per vane. Head machining are required in order to allow coupling of two plates (shown in the following) Each electrode end is equipped with 3 pins in order to allow precise plate re- positioning, if required. The brazing alloy is PalCuSil®10 (850°C melting point). It will be used for the brazing of the big copper pieces constituting the electrode body, as well as the plugs and the SS inserts

Main module components: Support Inserts Design review, 09/21/20157 AISI 316LN (R P0,2 =280MPa) Central threaded holes in order to plug the cooling channels and to use mounting tooling. 5mm housing for Helicoflex ® gasket (vacuum sealing)

Main module components: Support Flange Design review, 09/21/20158 AISI 316LN (R P0,2 =280MPa) Support flanges for supporting the electrode w.r.t. tank. They will be finished in the last phases of module assembly. Gasket housings (to be protected!) Thread for inserting special screws with reduction.

Main module components: Vacuum Cap Design review, 09/21/20159 in AISI304L (R p0,2 =180MPa) Two gasket housings (inner and outer) for vacuum sealing The thin part allows misalignments of the inner part w.r.t. the outer one.

Main module components: RF joint max=1.2mm Design review, 09/21/ LaCuD/0.15/0/465 Admittable excursion=1.2mm 5 to 8 N are needed for sealing in nominal position Total load for 1165mm electrode =475 to 760Kg 2.5mm

Main module components: Vacuum Seal Design review, 09/21/ Helicoflex © standard gaskets/ module 8 x C.S.=2mm, e2=0.6mm, D=100mm, Ftot=9000kg; 8 x C.S.=2.5mm, e2=0.6mm, D=150mm, Ftot=15400kg C.S. ( For the RFQ : 7 x C.S.=5mm, D=800mm, e2=0.8mm, Ftot=131000kg) Data from catalogue

Proposal for a brazed electrode Design review, 09/21/ Another possible solution (as an alternative to forged Cu) could involve not only plugs and inserts but also 3 bases and a thick plate. Deep hole drillings involve plate only, while the 3 bases are obtained via WEDM Modulation machining and other surface finishing can be done after brazing in order to avoid brazing-induced distortions. All machining of the inserts to be brazed is completed before brazing itself

Electrode machining Design review, 09/21/ Interface plates: the idea is to have an external modulation-related reference. Such plates are machined in the same way and with the same tool as modulation. The plates are fixed to the electrode ends via three pinned screws, in order to allow positioning repeatability. Copper bars: used to avoid changing the tool; they are machined at the same time as modulation. In this way, it is possible to obtain planes parallel to modulation axis. Moreover these pieces can be used as an external reference for next machining and module mounting

Assembly 1 h Design review, 09/21/ Reference plate-equipped electrode is mounted on a counterplate to be put on a granite plate (0.01 m flatness) The plate is equipped with a system of tilted planes in order to allow electrode alignment w.r.t. granite plane. CMM or laser tracker will measure alignment The electrode, once aligned, can be displaced with a pneumatic system on the assembly tooling

Assembly 2 Design review, 09/21/ Once positioned, the electrodes are placed in nominal position. Calibrated spacers can correct this position Then the electrodes are put in secure position. It is worth noticing that, in this phase, 2 mm are sufficient in order not to let RF joints interfere with the tank inner surface

Assembly 2 Design review, 09/21/ Now one proceeds to Tank handling structure mounting and then the tank is inserted from the top without RF joints

Assembly 3 Design review, 09/21/ Then the planes in blue and green are measured, and flanges are machined accordingly. In particular, flange machining foresees the re- machining of the Helicoflex ® seat, in order to obtain desired parallelism and roughness (1 micron)

Assembly 4 Design review, 09/21/ At this point the tank is lifted and RF joints are inserted. Then the tank is lowered and the tightening phase starts. In order to push the RF joint the electrode is pulled toward the external with an apposite tooling (to be modelled)

Assembly 4b Design review, 09/21/ Tank-flange-electrode coupling system: it is conceived in order to avoid moving the electrode w.r.t. the tank, thus avoiding contemporary fastenings of two gaskets.

Assembly 5 CF Spring Seal Design review, 09/21/ The thin SS part avoids loads on the structure during the gasket fastening.

Structural simulation of the electrode Design review, 09/21/ The study aims at the positioning of the supports in order to have an homogeneous electrode deformation ux vs z, thus easing compensation during mounting Z X

Constraints and loads applied Constraint on remote points, Gravity load, Equivalent force for seals (9000kg), and RF contact (370 kg) are taken into account Reaction permitted Design review, 09/21/201522

Engineer curve stress-strain for forged and annealed copper  p0.2 = 215MPa  p0.2  MPa E=117GPa Design review, 09/21/ For AISI316LN mechanical data are taken from literature 10 MPa= Safe stress value chosen for annealed Cu

Results: Equivalent Von Mises on Support Flanges Design review, 09/21/ Average stresses on the flange are <100MPa

Y Deformation intermediate electrode Axis of the support flange stay at Z=1/4L-17mm and Z=3/4L+17mm Design review, 09/21/ Directional deformation stay below the 14um and is homogeneous along the axis z.

Y deformation First and Last electrodes Axis of the support flanges stay at Z=1/4L+30mm and Z=3/4L+20mm Design review, 09/21/ Also for the extremity vane it is found a optimum distance that permits a uniform deformation under gravity effect. Directional deformation of tip stay below the 13 microns

Thermo-structural simulation of the electrodes Simulation inputs as shown in A. Palmieri presentation and results confirmed with 116 fluids element approach Design review, 09/21/ (The optional cooling channel on tank is used to reduce the mean stress of the electrode) UNDER STUDY!

Results: temperature of vane channels Design review, 09/21/ M1 Temperature calculated with power densities and with fluid elements agree within 0.1°C M2 M3 M4 M5 M6

Results: temperature of tank channels Design review, 09/21/  t (out-in) < 2°C for the tank cooling channels

Temperature Vane Design review, 09/21/201530

Temperature Tank Design review, 09/21/ The temperature in the flange zone is higher, since the reduced thickness reduces heat conduction. Anyhow, they do not exceed 50°C

VM stress on the electrode: Optional cooling channel off and on Design review, 09/21/ OFF ON Reduction of stress could be obtained with the additional cooling channel but further studies is needed

Directional deformation Design review, 09/21/201533

Basic study of support tank positioning Design review, 09/21/ SPES Steering Committee, INFN-LNL, March 23-24, 2015 Previous study was done to evaluate the correct position of electrode support flanges “This dimension and the support geometries will be studied to obtain a uniform displacements of lateral electrodes along the beam axis” Nodes on symmetry planes were constrained on each perpendicular plane direction.

Basic study for the support tank positioning Design review, 09/21/ The module supports (shape and positions) can affect the tank deformation as well as the tip displacements. Their dimensions are now under studying.

Further works and acknowledgments Detailed studies for the support flange Design of a brazing cycle and the geometry of the brazed joints Construction of one electrode and tank prototype Design of the support structure of the RFQ … Design review, 09/21/ Thanks to Marco Romanato for model drawing and for a lot of useful suggestions !!!!!