Preliminary design of the new HL-LHC beam screen for the low-β triplets

Transcription

1 Preliminary design of the new HL-LHC beam screen for the low-β triplets Marco Morrone TE-VSC-DLM 15/10/2015

2 Contents o CERN The Hi Lumi upgrade o Functional requirements -Functional study -Current vs new version -Design criteria o Mechanical design -Structural study during a quench -Thermal study during a quench o Prototyping and next steps

3 The Hi Lumi upgrade The HL-LHC Project Major intervention on more than 1.2 km of the LHC New IR-quads Nb 3 Sn (inner triplets) New 11 T Nb 3 Sn (short) dipoles Collimation upgrade Cryogenics upgrade Crab Cavities Cold powering Machine protection Smaller beam size at the interaction points. Beam profile around the experiments 25th November 2014 C. Garion

4 Functional requirements - functional study The HiLumi-LHC (HL-LHC) upgrade calls for a new tungsten-based shielding system to lower the debris coming from atomic collisions towards the cold masses of the superconducting triplet magnets (point 1 and 5). Therefore, the new beam screen has to ensure: -Thermal shielding of the cold bore from beam induced heat loads (1 W of heat on CB = 1kW of cooling energy, Grobner) -Vacuum stability -Mechanical resistance to magnet quench -Temperature in operation conditions between 40 and 60 K -Lowering beam impedance -Compliancy with beam optical requirements

5 Functional requirements current BS Cold mass Coils Beam screen Cold bore: separation UHV/ superfluid helium

6 Functional requirements new BS concept Beam screen as interface between:

7 Functional requirements - new BS concept Cold mass Proton beam

8 Functional requirements new BS concept Tungsten block Thermal links Thermal links Pumping holes Titanium ring Capillary Copper layer Courtesy of R.F Gomez

9 Gradient G [T/m] GG' [(T/m)^2/s] Functional requirements design criteria Vacuum stability Normal operation conditions Thermal Fourier Law 1D Worst-case scenario Magnet quench Resistive transition of the magnet Courtesy of V. Baglin Holes = 4% surface coverage Cross section thermal link Q = λs ΔT L Heat flux Thermal conductivity Temperature difference Thermal link length Q = 2W/ tungsten block of 40cm λ = 1000 W/K/m ΔT= 5 K L 25 mm Considering 4 links S = 10 mm 2 / link Specific force f GG ρ G - GG' Courtesy of E. Todesco Time [s] Magnetic gradient Electrical resistivity G GG' 0 dim= 20 * 0.5 mm Lorentz forces are maximum after s. Maximum GG = T 2 /m 2 /s

10 Gradient G [T/m] Mechanical design - structural study during quench 1 Magnet quadrupole gradient decay 3 Force distribution Laplace s law: f v =j B Time [s] 2 Eddy currents Ohm s law: j z = E z /r Maxwell equations rot E=- B/ t B: magnetic field E: electric field j: current density r: electrical resistivity Electrical field: E = 1/2.G.r 2. cos(2j).z Current density: j z = 1/2.G.r 2. cos(2j)/r Specific Laplace s force: f = 1/2.G.G.r 3. cos(2j)/r.(sin(2j)e q - cos(2j)e r )

11 Mechanical Thermal Magnetic Mechanical design - structural study during quench Multiphysics problem Time step Magnetic discharge Induced currents Temperature increase (Joule effect) Material properties vary with temperature Lorentz forces depend on material properties (electrical conductivity)

12 Mechanical - structural study during quench Fy = sec Fy = sec

13 Mechanical - structural study during quench [N] [N]

14 Mechanical - structural study during quench T.L. S shape COPPER MADE Thermal link 1

15 Mechanical - Thermal study during quench Thermal links T.L. wing shape COPPER MADE Thermal link 2

16 Thermal- Thermal study during quench Current density [A/m^2]

17 Temperature [K] Thermal- Thermal study during quench BS material heat capacity Q = mcδt Q= RI 2 Average temperature increase due to the eddy currents on the HL beam screen Time [s]

18 Temperature [K] Thermal- Thermal study during quench Max local temperature Thermal link 1 Thermal link 2 Tungsten block Stainless steel octagon Time [s]

19 Prototyping and next steps Assessing tolerances and mounting of the first BS prototype Next steps Design optimisation Peeling test Experimental test for the heat transfer and magnet quench

20 Mont Blanc Geneva