Gradient coil for small halbach magnet

[abanerjee123]

Dear Dr. Thanks for the great software. I have a small halbach magnet with 30 mm diameter and 40 mm height. I want to generate x,y,z gradient for this magnet. Is it possible to make such small one? what kind of parameter I should use to get a reasonable coil? It will bea great help if you kindly guide me . I tried but not able to get it.

Thanks abhishek

This is your code for halbach example.

tikonov_factor=10000; num_levels=30; pcb_width=0.002; cut_width=0.025; normal_shift=0.006; min_loop_signifcance=3; %close all;

circular_resolution=10; conductor_width=0.0015; cross_sectional_points=[sin(0:(2pi)/(circular_resolution-1):2pi); cos(0:(2pi)/(circular_resolution-1):2pi)]; cross_sectional_points=cross_sectional_points.*repmat(conductor_width,[2 1]); normal_shift_smooth_factors=[5 5 5];

%% Run the algorithm %try coil_x.out=CoilGen(... 'field_shape_function','x',... % definition of the target field 'coil_mesh_file','create cylinder mesh', ...
'cylinder_mesh_parameter_list',[0.4913 0.154 50 50 0 1 0 pi/2],... % cylinder_height[in m], cylinder_radius[in m], num_circular_divisions, num_longitudinal_divisions, rotation_vector: x,y,z, and rotation_angle [radian] 'surface_is_cylinder_flag',true, ... 'min_loop_signifcance',min_loop_signifcance,... 'target_region_radius',0.1,... % in meter 'levels',num_levels, ... % the number of potential steps that determines the later number of windings (Stream function discretization) 'pot_offset_factor',0.25, ... % a potential offset value for the minimal and maximal contour potential ; must be between 0 and 1 'interconnection_cut_width',cut_width, ... % the width for the interconnections are interconnected; in meter 'conductor_cross_section_width',pcb_width,... %width of the generated pcb tracks 'normal_shift_length',normal_shift, ... % the length for which overlapping return paths will be shifted along the surface normals; in meter 'skip_postprocessing',false,...

[Philipp-MR]

Dear abhishek,

Nice to hear that you like the code. You can generate a coil according to your need. You just need to change the sizes of the cylinder radius and length in the "cylinder_mesh_parameter_list" as well as the DSV size. Also you the may need to update the regularizaion factor, in order to update the sensitivies to the smaller size of the coil.

Best Philipp

[abanerjee123]

Thanks Philipp for the reply. I will give a try. What is DSV?

[abanerjee123]

Dear Philipp , I have one more question. How to find the terminal. Looks like circuit is closed. ![Uploading Screenshot from 2024-09-26 19-32-58.png…]()

[abanerjee123]

where to connect?

[Philipp-MR]

You can cut the wire path at any location and add the terminals. DSV is the diameter of the imaging volume.

[abanerjee123]

Thanks a lot