I've ablated something! ...I think

As predicted, Bianca and I spent pretty much all day in the lab Tuesday. After realigning some misaligned components, and relocating the CCD camera--of all the components in our system that one is particularly problematic as it tends to wander off on its own a lot--we got to shooting. We used KETH kurai and went around the rim, varying the number of bursts. We had the shutter set for the lowest (quickest) setting, so we were getting 1-2 pulses per burst. No damage was visible to the naked eye.

Wednesday was Bastille day. I slept in, planned for my trip to Ireland, and went to the Eiffel tower to see the fireworks. The fireworks, although pretty cool, were not overly impressive. I wound up walking back to Cité U from there because there were so many people and the metro was packed. Many of the buses were not running, probably because of all the people in the streets.

I came in on Thursday and experimented with the shutter. After tracking down the manual online, I figured out how to change the duration of the open and close cycle. I wanted to see how precisely the shutter's timer was, but something electrical was wrong with the laser and I didn't get the chance. I spend the afternoon making a presentation for Bianca of the SEM results.

My flight for Dublin left at 0930 Friday morning, which necessitated my waking up at 0500 to be at Port Maillot by 0615. I spent a few hours in Dublin before taking a train to Waterford. A friend of mine lives in Tramore, a small seaside city on the southern coast, where I spent the weekend. The trip was a lot of fun. I got back to Cité around 0130 on Monday morning because my flight back had been delayed. I was worried because the metro shuts down at 0030 and we did not get to Port Maillot until then, but I happened to meet 3 French girls who happened to live near Cité and we shared a cab.

On Monday I spent almost the entire day in the lab. I scanned across the surface of KETH Kurai with 1 mm spacing, hitting the coin with a different number of pulses/burst at different heights. I used bursts of 1-2, 5, 10, 50, and 100 pulses. We measured the spot size with a CCD camera and found the best focus to be ~70 microns in diameter. Unfortunately, the energy meter walked off, so I couldn't get a good measure of pulse energy, but if the numbers from Tuesday were still valid, it was on the order of 5 micro-Joules, giving a fluence of ~130 mJ/cm^2. This should, one would imagine, be enough for results to be visible after 100 pulses, but this was not the case, so I'm a little worried about whether the energy is significantly less. I performed the same experiment except with 1-2, 5, 10, 50, 100, and 500 pulse bursts on AN43U and again saw nothing visibly different about the coin.

I will try more pulses today. We're already using the maximum energy from the beam Rod's giving us, so if that doesn't work, the only other alternative is to use a tighter focal spot.