Everything David says is spot on. In addition to his tips:
Your tungsten looks a little thin for alumium. I use 3/32. It should hold up to the amps better.
There's a lot of either soot or smudges on your work. If it's soot from the welding process, it's another sign that you are having shielding gas problems. What type of gas are you using? If it's smudges from your gloves, get a clean pair of gloves. Having clean work makes all the difference with aluminum.