Quench in high field YBCO insert dipole Antti Stenvall Department - - PowerPoint PPT Presentation

Quench in high field YBCO insert dipole

Antti Stenvall

Department of Electrical Engineering Electromagnetics Tampere Finland http://www.tut.fi/smg firstname.lastname@tut.fi

WAMSDO-13 CERN, January 15-16 2013

Acknowledgements

This work is carried out in EuCARD project WP 7 HFM: Superconducting High Field Magnets for higher luminosities and energies, Task 7.4 Very high field dipole insert

◮ CERN: J Fleiter, ◮ CEA-DSM-IRFU-SACM, Saclay, France: M Devaux, M

Durante, P Fazilleau, T L´ ecrevisse, and J-M Rey

◮ Grenoble (and their numerous labs), France: P Tixador ◮ INFN, Milano, Italy: M Sorbi, G Volpini ◮ TUT, Tampere, Finland: E H¨

ar¨

• , A Stenvall

EuCARD is a common venture of 37 European Accelerator Laboratories, Institutes, Universities and Industrial Partners involved in accelerator sciences and technologies. The project, initiated by ESGARD, is an Integrating Activity co-funded by the European Commission under Framework Programme 7 for a duration of four years, starting April 1st, 2009.

Outline

◮ Overview of the case: Nb3Sn-YBCO hybrid dipole magnet in

EuCARD project

◮ Starting points ◮ Insert quench simulations ◮ Considerations on insert protection scheme ◮ Uncertaintities / difficulties / future work ◮ Conclusions

Overview of the case

◮ YBCO magnet producing 6 T will be inserted into the bore of

FRESCA II (previous presentation), maximum field will be 19 T at 4.2 K

◮ Insert consists of six racetrack coils (3 double pancakes)

Overview of the case

◮ YBCO magnet producing 6 T will be inserted into the bore of

FRESCA II (previous presentation), maximum field will be 19 T at 4.2 K

◮ Insert consists of six racetrack coils (3 double pancakes)

Overview of the case

◮ YBCO magnet producing 6 T will be inserted into the bore of

FRESCA II (previous presentation), maximum field will be 19 T at 4.2 K

◮ Insert consists of six racetrack coils (3 double pancakes)

Old design of FRESCA II

Overview of the case

◮ Insert will be wound from a cable consisting of two 12-mm

wide custom-stabilized-strengthened YBCO tapes. Two of these cables will be connected in parallel.

Overview of the case

◮ Insert will be wound from a cable consisting of two 12-mm

wide custom-stabilized-strengthened YBCO tapes. Two of these cables will be connected in parallel.

CuBe2 50 µm CuBe2 50 µm Copper 50 µm Copper 50 µm Hastelloy Hastelloy Copper 70 µm YBCO YBCO Solder Width=12.06 mm Thickness=460 µm

Overview of the case

◮ Insert will be wound from a cable consisting of two 12-mm

wide custom-stabilized-strengthened YBCO tapes. Two of these cables will be connected in parallel.

Overview of the case

◮ Insert

◮ inductance: 4 mH ◮ operation current: 2800 A ◮ self-energy: 15.7 kJ

◮ FRESCA II

◮ inductance: 64 mH ◮ operation current: 10500 A ◮ self-energy: 3.53 MJ (225 × that of insert)

◮ Mutual inductance 9.3 mH

◮ total energy 3.68 MJ ◮ mutual energy 8.7 × that of insert

◮ Maximum insert terminal voltage 800-1000 V

→ maximum dump resistor 0.29 Ω

Starting points

◮ FRESCA II is the big guy, we focus only on the quench

simulations of the insert and how to protect it and the influence of protection on FRESCA II

◮ We need to know how quench evolves in insert → simulate

quench

◮ We need to know how fast we can discharge the insert and

what is its influence on the FRESCA II → do simple circuit simulations

FEM quench simulations of HTS magnets

Simulating quench in an HTS magnet

◮ HTS magnets don’t want to quench easily, at least in

• simulations. Options for triggering quench
• 1. Quench the coil with a heater → unrealistic temperatures in

the hot spot in the beginning

• 2. Force critical current to some value below Ic in some region →

if region is too small, there are several seconds to quench → long simulation times

FEM quench simulations of HTS magnets

Simulating quench in an HTS magnet

◮ HTS magnets don’t want to quench easily, at least in

• simulations. Options for triggering quench
• 1. Quench the coil with a heater → unrealistic temperatures in

the hot spot in the beginning

• 2. Force critical current to some value below Ic in some region →

if region is too small, there are several seconds to quench → long simulation times

◮ Quench doesn’t propagate to the whole coil → don’t simulate

the whole coil (quench can also be difficult to detect, especially at low currents)

FEM quench simulations of HTS magnets

Simulating quench in an HTS magnet

◮ HTS magnets don’t want to quench easily, at least in

• simulations. Options for triggering quench
• 1. Quench the coil with a heater → unrealistic temperatures in

the hot spot in the beginning

• 2. Force critical current to some value below Ic in some region →

if region is too small, there are several seconds to quench → long simulation times

◮ Quench doesn’t propagate to the whole coil → don’t simulate

the whole coil (quench can also be difficult to detect, especially at low currents)

◮ How to get critical current characteristic for such a cable?

Did anyone ever measure Ic(B, T, θ) over a wide range of parameters? If you buy new batch of tape, has it similar properties than the samples? → we used certain approximation for Ic.

FEM quench simulations of HTS magnets

Simulating quench in an HTS magnet

◮ Our FEM approach

◮ We use custom-built code for quench simulations which we

constantly develop

FEM quench simulations of HTS magnets

Simulating quench in an HTS magnet

◮ Our FEM approach

◮ We use custom-built code for quench simulations which we

constantly develop

◮ We focus on characteristics which are important for quench

and leave other details for other specialists (postprocessing, basis functions, . . . ) → we develop our code within Gmsh environment directly ontop of Gmodel and Riemannian manifold interfaces.

FEM quench simulations of HTS magnets

Simulating quench in an HTS magnet

◮ Our FEM approach

◮ We use custom-built code for quench simulations which we

constantly develop

◮ We focus on characteristics which are important for quench

and leave other details for other specialists (postprocessing, basis functions, . . . ) → we develop our code within Gmsh environment directly ontop of Gmodel and Riemannian manifold interfaces.

◮ All solvers (including matrix assemblers) are built by us in

C++ with help from many GNU licensed libraries.

FEM quench simulations of HTS magnets

Simulating quench in an HTS magnet

◮ Our FEM approach

◮ We use custom-built code for quench simulations which we

constantly develop

◮ We focus on characteristics which are important for quench

and leave other details for other specialists (postprocessing, basis functions, . . . ) → we develop our code within Gmsh environment directly ontop of Gmodel and Riemannian manifold interfaces.

◮ All solvers (including matrix assemblers) are built by us in

C++ with help from many GNU licensed libraries.

◮ We can separate the magnetic problem from the thermal (at

least the meshes), and also combine if needed. We are free to build in FEM software what ever we need – within the limits of time (and money).

Simulation results

Step 1: compute field distribution (for Ic computations add the contribution from FRESCA II)

Simulation results

Step 2: simulate quench without any detection, terminate when Thot spot = 400 K, now circuit simulator wasn’t included due to low inductance

◮ Mesh

Simulation results

Step 2: simulate quench without any detection, terminate when Thot spot = 400 K, now circuit simulator wasn’t included due to low inductance

◮ Mesh

Simulation results

Step 2: simulate quench without any detection, terminate when Thot spot = 400 K, now circuit simulator wasn’t included due to low inductance

◮ Mesh

Simulation results

Step 2: simulate quench without any detection, terminate when Thot spot = 400 K, now circuit simulator wasn’t included due to low inductance

◮ Mesh

Simulation results

Step 2: simulate quench without any detection, terminate when Thot spot = 400 K, now circuit simulator wasn’t included due to low inductance

◮ Mesh

Simulation results

Step 2: simulate quench without any detection, terminate when Thot spot = 400 K, now circuit simulator wasn’t included due to low inductance

◮ Mesh

Simulation results

Simulation results

Simulation results

Simulation results

Step 3: determine when detection threshold voltage (100 mV) is reached, how normal zone propagetes etc

0.2 0.4 0.6 0.8 1 50 100 150 200 250 300 350 400 Time [s] Hot spot temperature [K] 0.02 0.1 0.5 1 2 5 710 50 100 150 200 250 300 350 400 Voltage over normal zone [V] Hot spot temperature [K]

Simulation results

Step 4: Circuit simulations

◮ Possible protection circuits

Linsert 0.28 Ω

Diode(s) A

Iinsert(t) LFII IFII(t) M Linsert 1 Ω 1 Ω 1 Ω 2 Ω

Diode(s) A B C D

Iinsert(t) LFII IFII(t) M

20 40 60 0.5 1 1.5 2 2.5 3 Time [ms] Resistance [Ω]

Simulation results

Step 4: Circuit simulations

◮ Insert fast discharge

20 40 60 500 1000 1500 2000 2500 3000 Time [ms] Insert current [A] Constant Rdump Time varying Rdump 20 40 60 100 200 300 400 500 600 700 800 Time [ms] Insert terminal voltage [V] Constant Rdump Time varying Rdump

Simulation results

Step 4: Circuit simulations

◮ Insert fast discharge

20 40 60 10500 10600 10700 10800 10900 11000 11100 Time [ms] FRESCAII current [kA] Constant Rdump Time varying Rdump

Simulation results

Step 4: Circuit simulations

◮ FRESCA II quench and insert dischange

200 400 600 800 1000 500 1000 1500 2000 2500 3000 Time [ms] Insert current [A] Constant Rdump Time varying Rdump 2000 4000 6000 8000 10000 12000 FRESCAII current [A] 50 100 200 400 600 800 1000 Time [ms] Insert voltage [V] Constant Rdump Time varying Rdump

Simulation results

Step 4: Circuit simulations

◮ FRESCA II quench while insert in open circuit

500 1000 −200 −150 −100 −50 50 100 Time [ms] Insert open circuit voltage [V]

Simulation results

Step 5: conclusion (not a new one): this small coil can be protected with only a dump resistor BUT

◮ How could we discharge the magnet as fast as possible and

what is the influence of this to the PSU of FRESCA II?

◮ Option to consider: if FRESCA II quenches, could we first

discharge insert and then activate the quench protection of FRESCA II? How to include the PSU of FRESCA II to simulations?

◮ Protection of very large HTS magnets is much more difficult:

margin to Tcs is high → effective quench heaters cause problems

Discussion - open questions

◮ How to get reliable scaling law for Ic(B, T, θ)? ◮ How difficult is it to protect HTS magnets having large stored

energies?

◮ What is the influence of AC-losses during quench in such a

wide coated conductor?

Summary

◮ YBCO insert magnet in EuCARD project was introduced ◮ Quench in the magnet was studied ◮ Possible protection schemes for the insert were considered ◮ Open questions were presented

Thank you for your attention

You can find this presentation and summarizing paper also from my home page http://antti.stenvall.fi