Part1: Store Alpha
We will use an option that is part of the 'Store alpha' tool. For PD
Particles to let you have access to that tool, you'll need to go beyond
the originally purchased 1.0 installation and apply the 1.2 or latest free update
patch.
Using PD Particles 1.2 in this example, click the "Cool Tools" button in the toolbar:

Click the Store alpha tool - even if you currently don't have any
selection mask or other content in the alpha channel.

The alpha channel always exists, you just may not have it visible. Or,
if everything is selected (the default), it may just not show the
marching ants.

In PD Particle's version of the Store Alpha tool, the initial panel
windo size may not show all tools it includes.
<<< Grab the lower right corner of the panel, to resize it.

After resizing the Stored alpha
panel, you should see the last option in the lower right corner:
Get buffer
This is the way you probably will see it in PD Pro.
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