heatsink gap

i have this gap around the same thickness as the diameter of a pencil lead used in those sharpening pencils, not the mechanical ones.it's between the processer, and the heatsink. what should i do:

1. get a copper plate, and sandwitch it between thermal grease.

2. put more thermal grease

3. put thermal pad, which is ussually thick enough for the task

4. use thermal putty, which is what is originally used in my computer.

this is the problem i'm having on one of my computers, and i don't have the option of buying a cpu cooler to replace it. just one of these 4 options, which is the best.

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