IAXO and Baby-IAXO Magnet Systems- Towards an IAXO TDR and Start of a Baby-IAXO Construction Project -

Content1. Magnet requirements2. IAXO Conceptual Design3. Magnet Variants4. Step-up Baby-IAXO Proposal5. From CDR to TDR6. Conclusion

Herman ten Kate

1

1.1 Magnet RequirementsAxions and Helioscopes

Axion helioscope concept:

• A high magnetic field oriented transversely to the solar flux of axions in a large bore magnet, tracking the sun, with photons concentrating optics and X-ray detectors

• Magnet’s Figure Of Merit (MFOM):

• 300 x CAST was set as an “affordable” project size

• Thus design drivers are magnetic field B, area A and length L !

2

1.2 Magnet RequirementsParameters and lay-out optimization

B2 {magnetic field}• more than saturation field of iron at 1.7 T• cost efficient superconducting magnet technology • --> NbTi at 4.5 K using normal He cooling, Bpeak < 6 T • --> 2.5 T user field with 5.4 T peak magnetic field

L2 {length of the magnet}• as long as possible but • reasonable system length that can be rotated?• --> some 20 to 25 m: 22 m

A (or n x π/4 D2) {area filled with magnetic field} • one large area i.e. using a dipole magnet• or n times a bore in between toroid coils• i.e. 8 coils, or 10, 12, 14, 16 max, cost issue!• smallest reasonable number taken: --> 8 units• limit system diameter and go for maximum

practical size for optics: --> 600 mm bore 3

2.1 Conceptual design of IAXOSystem overview

5

2.2 Conceptual designMain Parameters

6

2.3 Conceptual designCold mass: coil winding pack in a casing

• Two racetrack type double pancakes

• 2 x 90 turns per coil• 8 coils of size 21 m x 1 m• Pre-stressed to reduce shear

stress• Glued in an Al5083 casing• Al alloy cooling pipes glued

on the casings• Central support cylinder to

react magnetic forces• Keystone boxes and plates for

increasing stiffness and supporting the warm bores.

7

2.4 Conceptual designCryostat and cold mass support

• Rigid central part of Al 5083, 70 mm thick

• Reinforced bottom plate, 150 mm thick

• 2 x 20 mm thick Al5083 reinforced cylinders

• 2 x 30 mm thick Klopper shaped end plates

• 8 thin cylindrical bores, to allow insertion of gas or other media or detectors

• Cold mass is fixed to the central part• 4 x G10 feet, connecting the reinforced

bottom plate and keystone box, support the cold mass.

8

2.5 Conceptual designSystem integration study

• IAXO is placed in a light and confined structure (cost efficient).

• Assembly is in another hall allowing for large tooling and infrastructure for the cold mass and cryostat integration.

• Installation of services lines and Integration with auxiliary systems is performed at the last stage of system integration at the installation site.

9

2.6 Conceptual design Movement System

• IAXO’s detectors need to follow the sun as long as possible.

• Services are placed on top of the rotating table.

• Flexible chains guide the different services lines to the connection point.

• Vertical movement is performed by two semi-circular supports with extension sections.

• A rotating table, mounted on top of circular rails and roller drives, performs the rotation and carries the helioscope structure.

• Altitude over horizontal tracking mount, connected to the vessel at the center of mass of the entire system.

• Providing a ±25○ inclination and a 360○rotation.

10

3.1 Toroid Magnet VariantsToroid of simple racetrack coils (default CDR)

11

Advantages:Racetrack coils, easy winding,straightforward support structure

Disadvantages:Relatively high peak field on conductorSignificant amount of field outside of free bores --> high stored energy,in-homogeneous field inside bore

Property Value

Free bore diameter [m] 0.6

Average field in bore [T] 2.5

Stored energy [MJ] 500

Peak-field on conductor [T] 5.4

Amount of NbTi, assuming 2 K margin [t]

12

3.2 Toroid Coil VariantsToroid of Dipoles built from Canted Cosine Theta Solenoids

12

Calculated in FIELD, assuming 5x5mm2 sc core in conductorInner radius: 0.375 mWinding angle: 15ο, (30o --> NbTi increases by about 30%)Advantage: lower peak field --> reduced amount of NbTiDisadvantage: not proven technology for this size, complicated windings

Property Value

Free bore diameter [m] 0.6

Average field in bore [T] 2.5

Stored energy [MJ] 280

Peak field on conductor [T] 3.3

Mass NbTi (2 K margin) [t] 3.5

5 mT boundary [m] 15.6

CCT design proposed by R.Musenich, S.Farinon (INFN Genova)

3.3 Toroid Coil VariantsToroids of Up-Down Configurated Octupole

13

2D calculation, uniform current density (real peak field is likely to be higher)Radial force may be controlled with amount of steelAdvantage: uniform field (Bmax=2.8 T in bore) and reduced amount of NbTiDisadvantage: winding much more complicated than conceptual toroidal design

Property Value

Free bore diameter [m] 0.6

Average field in bore [T] 2.5

Stored energy [MJ] 280

Peak-field on conductor [T] 3.2

Mass NbTi (2 K margin) [t] 2.9

5 mT boundary [m] 4.8

Octupole design proposed by A.Dudarev, M.Mentink (CERN)

3.4 Toroid Coil VariantsPros and cons…

14

Flat Racetrack Coils - Toroid design (CDR Default)• Straightforward coil winding and support structure• Proven technology for his size of magnets• But: Somewhat inefficient in terms of NbTi usage

CCT Dipoles - Toroid design• More efficient in terms of field configuration --> Reduced

stored energy, amount of NbTi• But: More complicated conductor layout

Saddle coils Octupole or Toroid design• Field configuration efficiency similar to CCT• Very homogeneous field inside bore• Still more complicated conductor layout compared to

conceptual toroidal design

4.1 Baby-IAXO - MotivationA fully functional scale-model demonstration IAXO

The IAXO CDR recommends the construction of models representing the three main challenges: a reduced-length T0 coil + a real size optics module+ real size detector unit, however, as stand-alone models, not integrated into a fully functional facility that may be used as a CAST+ !

At a magnet brainstorm meeting in Dec 2016, while discussing the strategy towards TDR, it was proposed to adapt the three-models program, and turn it into a fully functional subscale demonstration IAXO, called BabyIAXO, to bridge the gap between CDR and a 40 million size full IAXO project, at modest additional cost….

How does this BabyIAXO magnet look, aiming at FOM 10 x CAST?

15

T0 model coil

BabyIAXO……..

4.2 Baby-IAXO MotivationA fully functional scale-model demonstration IAXO

16

Coil optimization for 2.5 T bore field (higher possible, but cost….)Maximizing B2 in area, is pointing to a classical two layer cos-t dipole magnet, with top angles of some 60 in in inner layer and 30-40 degree in outer layer.

• 10xCAST, downscaling IAXO, while keeping the basics: exercise coil + 600mm optics + full size detector

--> 1 tube in stead of 8 and shorter, about 10 m length

Coil cross-section, 2 layers

Coil in 3D, 10m long

4.3 Baby-IAXO MotivationMagnetic field in and outside the coil

• Magnetic field in cross section and in the mid plane along the coil

17

• Note, that the dipole is not shielded by default

• Acceptance of this depends on the site for BabyIAXO.

• When shielding is required and extra iron shell around the cold mass is needed (which is heavy and costs)

4.4 Baby-IAXO MotivationConductor and Coil design

• Al0.1wt%Ni stabilized NbTi/Cu superconductor, in 2x2 layers, conduction cooled.

18

Cable propertiesCritical Current at 5T/4.2K [kA] 25Nominal current [kA] 10Temperature margin [K] 2# strands 18Strand diameter [mm] 1.45Total area [mm2] 185.6Strand area [mm2] 29.7

Coil properties Stored energy [MJ] 40Energy density [kJ/kg] 10Number of turns [-] 428Length of conductor [km] 8.2

Free bore diameter [mm] 600Bore length [m] 10

4.5 Baby-IAXO MotivationStress and mass in coil windings and structure

19

• 77 MPa in the coil windings with support structure present, a safe value for this conductor and Al alloy

• 100 MPa in the shell & pole pieces support structure

Mass superconductor [kg] 1900Mass coil support [kg] 10900Mass vacuum vessel [kg] 1400Mass thermal shield [kg] 500Total mass [kg] 14700

4.6 Baby-IAXOCryostat and heat load

20

Cryostat parametersFree bore diameter [mm] 600Bore length [m] 10Cryostat outer diameter [m] 1.0Heat load @77K [W] ≈185Heat load @4.5K [W] ≈15

• 10 m long, 1 m diameter cryostat of Al 5083, with 600mm free bore

• Bucking stress limited, use of reinforcement rings to keep the structure light

4.7 Baby-IAXO Fully dressed ….

21Option with 2 optics+detectors, limiting rotation to 180 degree?

4.8 Baby-IAXO Just another view……to please the eye and imagination

22

4.9 Baby-IAXO Cost A 1st rough cost estimate……

23

Superconductor, 8 km 800 k€Coil winding & tooling 240Cold mass structures (no iron shielding) 200 Cryostat and thermal shield 250Cold mass in Cryostat integration & tooling 175Various small part 75Controls, instrumentation, safety 170Power Converter, switch, RDU & bus bars 225Pumps, gages, valves 40Proximity cryogenics (connected to existing plant) 150Support & rotation system, simplistic 75Unforeseen (15%) 350

Total: ≈ 2750This is a rough guide cost, all to be confirmed by company or workshop quotes! True cost very much depends on:Man power cost (in lab workshop with local support, or company)Implantation of BabyIAXO in a local site with services and structures available.

5.1 From CDR to TDRMagnet Conceptual Design Report

24

&Two new addenda:

(1) IAXO Magnet Variants

(2) BabyIAXO CDR

5.2 From CDR to TDRDesign and engineering issues

• Detailing cold mass design: cryogenic system pipe-work; bus-connections; cold mass supports, tie rods and movement stops.

• Developing quench protection scheme, including an energy dump simulation.

• More details on the vacuum vessel and thermal shield design.

• Complete thermal design, temperature map, including radiation.

• Integration and assembly study, in particular interface with optics and detectors.

• Design of the rotation and inclination system.

25

• Find a site and study implementation and connections to local services

• Raise budget for the “learning-on-the-Job” construction of BabyIAXO, find a site and start its construction, implementation in the local environment

• Enjoy a few years of physics date taking while preparing for IAXO……

6.1 Developments, Initiatives at DESYGrowing commitments…..

• CERN commitment for a providing a Fellow for further detailing of BabyIAXO, magnet system, infrastructure, implementation in a site (decision autumn 2017).

• Various efforts developed at DESY for reinforcing of and participating to IAXO. • DESY will provide administrative support to the IAXO-office starting early 2018,

creation of an IAXO technical coordination office.• DESY physicist are creating an IAXO “group”, complementary to their other axions

like projects like ALPS, and are applying for funding.• DESY is performing a serious study for siting first BabyIAXO and later IAXO.• The IAXO community is transferring into a formal Collaboration of Institutes. • In the July 3 Collaboration Meeting at DESY, the IXAO Collaboration was

established including bylaws approved at the meeting.• Now seeking for MoU commitments from labs including appointments of

representatives in the Collaboration Board, selection of chairman and spokespersons, etc.

26

6.2 Siting at DESYSome pictures of July presentation…..

27

6. ConclusionSummary and next steps

• Magnet design satisfies the main criterion on axion sensitivity (300 x CAST).

• Design is relying on known engineering solutions and manufacturing techniques featuring minimum risk and cost.

• Segmentation, allowing staging of 3 principle units: magnet - optics - detector.

• IAXO is ready for site selection and implementation study.

• Demonstration project Baby-IAXO proposed, seeking site & funding……..

28