First calculations of the CLIC Antisolenoid system A. Bartalesi, M. Modena - CERN

First calculations of the CLIC Antisolenoid system

A. Bartalesi, M. Modena - CERN

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First calculation for an antisolenoid for the CLIC Detectors was done in 2009 by D.Swoboda and impact on beam was then analyzed by B.Dalena.H.Gerwig started to work on the integration of all the subsystems of the MDI and the Detector region at the end of 2009.A.Bartalesi has joined our group as a Fellow in July 2010 and one of his task will be to work on the conceptual design for a “real” QDO taking into account its environment.In this context we have taken back the magnetic simulation of the antisolenoid and of the experiment magnet in order to prepare a global model for the QD0 environment.

The first calculations done during this Summer were mainly:-Make the modelization of a full-length QD0 and starting the mechanical-structural analysis (forces, harmonic analysis, deformations, stiffness, etc.)-Resume the magnetic calculation in order to prepare a global model for the QD0 environment. This second point is here presented.14 September 2010 A. Bartalesi, M.Modena: "CLIC Antisolenoid"

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CLID SiD experiment with its antisolenoid

14 September 2010 A. Bartalesi, M.Modena: "CLIC Antisolenoid"

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In the 2009 design the antisolenoid was composed by 5 segments differently powered. The structure was then simplified with only 3 segment powered. As we will see later, the shielding effect of the antisolenoid seems work at an acceptable level, anyway we have several reasons to try to better optimize the design mainly:

- Try to reduce the total forces and stresses on the antisolenoid coils and on the retaining structures by a distribution of the amperturns on a bigger area

- Make a better homogenization of the residual magnetic field at the front-end of the MDI region (where QD0 start) in order to avoid possible problems with the permanent magnet working conditions (very high longitudinal gradient of the external field)

We discussed this point with Barbara Dalena and she will check if an optimization routine (analytical) for the dimensioning and positioning of the antisolenoid segments could improve the magnet functioning.


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The total forces and the stresses seems acceptable even if quite high. We discussed the first mechanical results (global forces and internal stresses in the coils) with Andrea Gaddi and the cross-check with analytical formulas give a coherent result. The level of the global forces depends by the position of the antisolenoid deeply inside the iron of the experimental magnet; strong repulsive forces act between the two magnets and the azhimuthal (hoop) stress in the antisolenoid coils change of sign when the experimental magnet is switched on. These aspects must be taken into account in the dimensioning of the coils, supports and cryostat also not forgetting that the available space for the design of the antisolenoid and its ancillary structures will be quite limited radially .


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Coils dimensions and current densities


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Axial Magnetic Field in the experiment and in the QD0 region.Values are in Tesla. The grey box indicate the region of QD0 (2.7 m long)


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Radial Magnetic Field in the experiment and in the QD0 region.Values are in Tesla. The grey box indicate the region of QD0. NOTE: the magnetic field is plotted versus the real beam nominal direction (i.e. trajectory on a 10 mrad angle with the main solenoid axis)


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Load Case 1: both solenoid AND antisolenoid are energized

- Resulting forces tend to push the antisolenoid away from the IP - Radial forces on the coils are centripetal-like (less stable)


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Load Case 2: ONLY the antisolenoid is energized

- The antisolenoid coils are attracting between them- Radial forces on the coils are centrifugal-like (stable)



Load Case 1 (both solenoid AND antisolenoid are energized):Lorentz’s forces tend to collapse the antisolenoid

zr

zr

Radial and azimuthal stress maps on coil 1

σrr σθθ εrr εθθ

Max 0 MPa -51 MPa 4.4 e-4 -6.2 e-4

Min -15 MPa -77 MPa 1.4 e-4 -8.6 e-4


Load Case 2 (ONLY antisolenoid is energized):Lorentz’s forces tend to expand the coils

zr

zr

Radial and azimuthal stress maps on coil 1

σrr σθθ εrr εθθ

Max 0 MPa 161 MPa -4.0 e-4 2.0 e-3

Min -13 MPa 124 MPa -6.1 e-4 1.6 e-3


Axial stresses for Load Case 1 and 2 :Stresses coherent with global axial forces evaluated

zr

zr

Axial stress maps on coil 1

σzz εzz σzz εzz

Max 0 MPa -4.9 e-4 0 MPa 2.4 e-4

Min -44 MPa -9.5 e-4 -33 MPa -2.6 e-4

Load case 1 Load case 2

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CONCLUSIONS:

-First magnetic and mechanical analysis of the antisolenoid system for the CLIC experiments were done (based on the 2009 design).

-The magnet (superconducting technology) dimensioning seems feasible even if stresses and global forces are quite relevant.

-Discussion with Beam Physic Team are ongoing in order to check if the antisolenoid system design (coils positioning) could be better optimized from magnetic (and consequently mechanical) point of view.

-We analyzed the stresses and forces assessment with the Integration Team. Interaction with them will go on in order to find and check the feasibility of the magnet (structural, integration in the MDI region) that is the main target for the conceptual design phase of the Project.

-Important scenario to be taken into account in further simulations: discharging of the main solenoid and/or of the antisolenoid ( dynamic effect during transients).

(Thanks to Barbara and Andrea for the fruitful discussions)


Documents

First calculations of the CLIC Antisolenoid system A. Bartalesi, M. Modena - CERN