How do I handle this texture error in a keydown event?

I created a User Input Service event with particles, when I press the F key I should create a ball with the texture but it is giving error and I do not know how I put texture in it

This is My Script

game.Workspace.RainbowFlash.OnServerEvent:Connect(function(Player)
	local Character = Player.Character or Player.CharacterAdded:Wait()
	local Rb1 = Instance.new("Part")
	Rb1.Name = "Rb1"
	Rb1.Shape = Enum.PartType.Block
	wait(0.3)
	Rb1.Size = Vector3.new(0.2,5,2)
	Rb1.Material = Enum.Material.Neon
	Rb1.Anchored = false
	Rb1.BrickColor = BrickColor.Random()
	Rb1.CanCollide = false
	Rb1.Parent = Character
	Rb1.CFrame = CFrame.new(Character.LeftHand.Position)
	local tx = Instance.new("ParticleEmitter")
	tx.Name = "Texute"
	tx.Texture = "rbxgameasset://Images/a"
	tx.LightEmission = 0.6
	tx.Lifetime = 1
	tx.Rate = 500
	tx.Rotation = -180
	tx.RotSpeed = -150,260
	tx.Speed = 0
	tx.SpreadAngle = 0,0
	tx.Parent = Rb1
	local bv = Instance.new("BodyVelocity")
	bv.MaxForce = Vector3.new(math.huge,math.huge,math.huge)
	bv.Velocity = Character.HumanoidRootPart.CFrame.lookVector*70
	bv.Parent = Rb1
	
	wait(0.5)
	Rb1.Touched:Connect(function(hit)
		if hit and hit.Parent.Humanoid then
			hit.Parent.Humanoid:TakeDamage(5)
		end
	end)
	wait(1.5)
	Rb1:Destroy()
end)

Someone Help me