The Emitter generates creeper-emitting particles. These particles spawn deadly creeper, but they have a half-life and decay over time. Use a Nullifier to destroy an Emitter.

{
    "type": "unit",
    "enemy": true,
    "displayname":"Emitter",
    "image": "body.png",
    "sortingorder": 2,
    "position": [0, 0],
    "pivot": [0.5, 0.5],
    "isbuilt": true,
    "hasphysics": true,
    "parts": [],
    "scripts": [],
    "creeperdamages": false,
    "digitalissource": false,
    "nullifiable": true,
    "playercandestroy": false,
    "playercontrolbuildsupply": false,
    "playercontrolammosupply": false,
    "objectivetype": 4,
    "parts": [
                {"part": "$/weapon_emitter/weapon_emitter.json", "position": [0, 0]},
             ],    
    "controllers":     [
                        {
                            "name": "ondestroy_sandexplosion",
                            "amt": 500,
                            "minvelocity": 1.5,
                            "maxvelocity": 3,
                            "color0":[0.2, 0.4, 2],
                            "color1":[0.2, 0.6, 2],
                            "sandtype": 98,
                        }
                    ]                
}