How to make the particles visible only on the outside of the circle

Phaser 3
1

Hello.

I created an emitter in the center of the circle. But I don’t want the particles to be visible inside the circle, only outside it. Particulars must fly exactly from the center of the circle.
How can I realize this (without masks)?

2 
particles.createEmitter({
    alpha: {
        onUpdate: (p) => (Phaser.Math.Distance.Between(p.x, p.y, CX, CY) > RADIUS ? 1 : 0)
    }
});