Antiproton production horn operation and testing

Transcription

1 Antiproton production horn operation and testing 10th International Workshop on neutrino beams & instrumentation (NBI 2017) 18th 22nd September 2017 E. Lopez Sola C. Torregrosa, A. de Macedo CERN, Engineering Department, STI/TCD

2 Outline AD target area AD magnetic horn Horn operation Electrical operation Trolley system Clamping system Thermomechanical calculations Horn powering test-bench 2

3 AD target area Antiproton Decelerator (AD) ring Production of low energy antiprotons for studies of antimatter. AD target area The antiprotons are produced (AD target), focused (AD horn), momentum selected and injected into the AD ring 3

4 AD magnetic horn external conductor inner conductor! Two coaxial conductors: Inner conductor with bi-conical horn shape External conductor carrying 400 ka current pulse to and from the inner conductor 30 mm Inner conductor: Optimized thickness (1 mm 3.5 mm) small as possible to decrease antiproton reabsorption without compromising the mechanical integrity. Material: Aluminium AA7075-T6 High tensile strength under dynamic stresses Work in intense radiation fields 13 mm (3.5 mm thick) 4 60 mm (1 mm thick)

5 AD magnetic horn PS line BEAM #! Beam Target Horn x50 Effectiveness of the horn: Factor 50 gain in antiproton fluence with the magnetic horn 5

6 Electric Operation Capacitor discharge circuit 18 ignitron switches Generate fast (40 µs!) 400 ka current pulse Stripline carries 400 ka to the horn Junction box 80 connectors Power supply Stripline 5 m long Upgrade of the AD horn powering system: Replace ignitrons by solid state switches (IGBT) Clamping system Horn sandwich line + magnetic horn 6

7 Horn trolley current design Trolley supporting the magnetic horn, the sandwich line and the clamp Positioning of the horn Horn maintenance out of high radiation area Mounted on rails & lead-screws 4-5 m transversal movement with respect to the beam System drawbacks: Poor alignment precision Lead-screws induce vibrations Transmission systems fixed in very radioactive area Big amount of radio activated mass 7

8 Horn trolley system re-design Two subsystems: stationary support + motorized trolley During operation: Stationary support in the operation area, horn positioned on beam axis Motorized trolley + transmission systems parked and shielded 8

9 Horn trolley system re-design Two subsystems: stationary support + motorized trolley During maintenance: Motorized trolley displaced below stationary support Stationary support lifted and brought to maintenance area Trolley system upgrade: Full assembly testing in September No lead-screws Motorized trolley and transmission systems shielded Stationary support mechanically fixed by V-supports à improved precision Reduced size and activated mass

10 Clamping system In operation: Sandwich line positioned by the trolley and connected to main stripline Clamping system ensuring electrical contact à critical part Jaws: silver coating + multicontact strips Jaws Clamp arm Clamp design (1980 s) Insulator Clamping system and stripline damaged by arcing in the past 10

11 Clamping system re-design Multicontact strips Negative, positive and insulating layer glued together (no screws) But, only 0.1 mm compression range! Requires precise machining of all parts + control of gluing process Clamped assembly for measurement before gluing Floor of the 3D metrology machine Insulator 11

12 Spare horn dismounting Incomplete/outdated documentation à dismounting of a spare horn Validation of the existing drawings à Launch of the 3D model Knowledge acquired for the assembly of new horns Whole horn + stripline structure Verification of screws, dimensions, specifications Validation of the materials - Insulator stripline/negative plate - Inner conductor à Metrology inspection 12

13 Thermal calculations Beam pulse = 4 proton bunches coming from the PS machine ~ 500 ns pulse, 1.5x10 13 ppp at 24 GeV Coincident with the current peak à Strongest focusing magnetic field I (ka) Beam pulse Current pulse Beam Pulse t (µs) Energy deposition in the inner conductor (FLUKA) Current operational scenario: 90s repetition rate Max temperature ~ 55 C ü Inner conductor neck 13

14 Thermal calculations Future possible operational scenario: 9.6 s repetition rate + 70 s cooling Max temperature > 85 C! Aluminium AA7075 properties drop at high temperatures > 100 C Temperature ( C) Time (s) Horn forced air cooling systems study CFD calculations Possible optimization to increase the HTC distribution 14

15 Structural calculations High-current pulse à strong electromagnetic forces Compressive pressure applied to the external surface of the inner conductor 300 Static eq. VM stress along internal surface Max Pressure: 61 MPa 250 Results from ANSYS WB Z direction (mm) Min Pressure: 2.6 MPa Results from Maxwell 3D Static stresses Max eq. Von Mises stress 200 MPa (Inner surface of the neck ) Eq. VM stress (MPa) Yield strength of AA7075 at operation temperature: MPa 15

16 Structural calculations Dynamic stresses Max eq. Von Mises stress = 190 MPa Maximum tensile stress = 150 MPa (Horn neck surface, longitudinal direction) Stress (MPa) Nodal normal stress (Z direction) E E E E E-04 Time (s) Dynamic stresses could lead to high vibrations in the horn / trolley!! 16

17 Vibration measurements Calculated and then measured vibrations with LDV during April 2017 Structural calculation à velocity evaluated in the target point of the laser Velocity (m/s) 2.00E E E E E-01 Nodal velocity T 50 µs Time (s) Max velocity level due to the electrical impulse: 0.24 m/s T 50 µs Excellent agreement with the calculations despite the complexity 17

18 Horn powering test-bench Manufacturing of a new set of magnetic horns executed Dedicated horn test bench under construction in the AD target surface building à replica of the area setup High voltage Junction Box, stripline, clamping system Testing starting in October/November 2017 Tested horns instrumented with strain and temperature gauges to validate the thermomechanical calculations and study the operational limits Inner + outer conductor Junction box Stripline 18

19 Conclusions Several activities performed, on-going and planned related to the updates of the antiproton production horn The trolley system has been re-designed and is foreseen to be tested next year The clamping system is on re-design phase Thermal and mechanical calculations have been performed in order to evaluate the operational conditions of the horn and its future operation An horn powering test-bench is planned for next month with a replica of the re-designed AD horn. 19

20 Thank you for your attention! Acknowledgements: M. Calviani, C. Torregrosa, A. de Macedo, D. Horvath, B. Riffaud, R. Ferriere