Conceptual Design of a Small

Aspect Ratio Tokamak of

Variable Configuration

J. Julio E. Herrera Velázquez1, Ismael Arroyo Díaz1,

Esteban Chác+vez Alarcón2 1Instituto de Ciencias Nucleares, UNAM, Mexico

2Instituo Nacional de Investigaciones Nucleares, Mexico

herrera@nucleares.unam.mx

Motivation

• Which could be a design, small enough to be supported with

relatively modest means, while at the same time it could

make a contribution to the field.

• Most tokamaks are restricted in their shape (aspect ratio,

elongation and triangularity) by their design. From the plasma

physics point of view, it would be desirable to have more

flexible devices in order to achieve a better understanding of

the role of those parameters.

• While the D shape in most tokamaks is motivated both by

structural reasons of the stress in the coils, and by physical

reasons, which allow for better MHD stability, it may be worth

studying from the plasma physics point of view a wider range

of configurations, including negative triangularity

The example of the TCV at Laussane

Coutlis et al., Nuclear Fusion

39 663 (1999)

𝑅𝑜=0.88 m

𝑎= 0.20 m

휀 = 𝑎/𝑅𝑜=.29

𝐼𝑝 ≤ 1MA

𝐵 < 1.54 T

The example of the TCV at Laussane

Coutlis et al., Nuclear Fusion 39 663 (1999)

TMX-1 Preliminary conceptual design

𝑅𝑜=34.3 cm

𝑎= 25.0 cm

휀 = 𝑎/𝑅𝑜=.73

𝐵~ 0.3 T

TMX-1 Preliminary conceptual design

Magnetic field system

• 10 toroidal field coils (maximum ripple smaller than 1%)

• Central solenoid

• Control coils

• 6 external control coils

• 6 internal control coils surrounding the central solenoid

• 8 vertical field and compensation coils distributed in an upper and a lower

gorup.

The 3D-MAPTOR code

Knowing the magnetic field of every current involved; both toroidal and poloidal, the

total magnetic field at each point is determined.

. Bl

P(r, ,z)

x lx l

z lz l^

y ly l^

l

R

r

e

e ze z^

e re r^

^ Bl

Bly

BlzBlr

módulo toroidal x

y

y

x

a1h1

z

a1-h1

P(r, ,z)

r B1

r2

r1

B2

B

The Poincarè map Starting from a set of intial conditions, the magnetic field is

found along the torus numerically, and the Poincarè map is made for any desired plane along the torus, or the equator.

x y z

dx dy dz ds

B B B B

z

x

y

P(x,0,z)

(x1,y1,z1)

(x0,y0,z0)

z

x

y

P(x,0,z)

(x1,y1,z1)

(x0,y0,z0)

𝜖 = 0.90

𝜅 = 1.88

𝛿 = 0.38

𝐼𝑝 = 0.62 kA

𝜖 = 0.73

𝜅 = 1.17

𝛿 = 0.05

𝐼𝑝 = 0.27 kA

𝜖 = 0.80

𝜅 = 1.7

𝛿 = −0.35

𝐼𝑝 = 0.27 kA

Vacuum Chamber

R= 63.0 cm., h= 120.0 cm. Material: Stainless steel 306L, Minimum thickness

6.35 mm

Stress simulation with INVENTOR AUTODESK

The magnetic field system

Stress simulation

Design of the toroidal field coils

Central solenoid and inner control coils

Central solenoid and inner control coils

Conclusions

• Preliminary stepd have been made in order to evaluate the

possibility of building a START-sized spherical tokamak with the

capability of making shape and position control studies.

• The general purpose is to study the dependence of the physics on

changing geometrical parameters, including the possibility of

negative triangularity.

Future Work

• Improving the coil distribution in order to allow a better sapce for

diagnostics

• Working on the power supplies and the feedback systems for the control

of the shape and position of the plasma column.