How to create an Illustrator fountain spray effect, you can use the arc tool singularly. Just select the tool in the tools panel and apply and then position the curved design as you wish.
However, you can also hold down the tilde key as you draw the design and as you do that you will generate 100s of copies of that artwork from that central position of drawing the design - it create a spray like effect, it creates a fountain etc. You can use the tilde key in countless ways to create all kinds of amazing artworks.
You can also manipulate the line of the curved design so instead of just a solid line you can add dashes as well as different curved width profiles and much more to create a near infinite number of designs
all vectors that can then be manipulated even further such as using warping tools and more.