581
edits
Changes
Jump to navigation
Jump to search
Line 29:
Line 29: − + + + + − An integrating circuit was designed and constructed to measure the sum of current off the gold-tungsten wire. The scans are done in pairs of 2d projections: xz (called x-scans) and yz (called y-scans). Between the scans the wire frame is swapped out because there are separate frames for the vertical (x-scan) and horizontal (y-scan) wires. The 2d scans consist of an inner loop over the transverse coordinate, and an outer loop over z. The transverse coordinate range is 2 mm and the z coordinate range is 12 mm. Each pass has a single value of z, and sweeps over the full 2 mm range in x or y. The output of the integrating circuit is connected to an ADC which is sampling continuously over that the whole time period the scan is taking place. − [[Image:2Wcircuit.png|left|thumb|300px|Schematic of integrating circuit used in focal study.]] − Each pixel in the plots shown in Figures 6 represents one laser pulse, with the color representing the pulse height integral. The lower-most row should be ignored because the scanning program was not yet fully synchronized to the raster pattern. The widths of the focal spot in x and y are shown in the 10 RMS values of the fits in Figure 7. The values in x and y are roughly the same, 65 µm vs 48 µm respectively. Figure 6a shows a maximum intensity at a z position of 4.8mm, however it is interesting to note that the shape of the focal spot does not appear to change drastically away from this point. The optical setup has a narrow focal spot with a wide depth of field which is ideal for the purpose of laser ablation. From this study it was also concluded that the use of a collimator at the focal point of L1 and L2 greatly reduced the background seen by the harp scan and should be used during the ablation process to protect the diamond surface away from the ablation point. − [[Image:2wire.png|left|thumb|300px|CAD drawing of harp scan mount]]
Diamond Radiator Thinning Using an Excimer Laser (view source)
Revision as of 21:27, 15 December 2016
, 21:27, 15 December 2016→Focal Spot Characterization
===Focal Spot Characterization===
===Focal Spot Characterization===
The focal spot created after the laser pulses pass through the optical setup illustrated in Figure 1 was measured using a harp scan in both the horizontal and vertical planes. Two mounts were machined with horizontal 8 and vertical v-grooves where 50 µm gold-tungsten wire was stretched and glued. The mount was anodized to insulate it from the gold-tungsten wire as well as the ablation chamber itself. As the laser irradiates the gold-tungsten wire electrons are freed via the photoelectric effect and a positive current flows through the wire which can be measured. The total current produced is dependent on the flux of UV light incident to the wire and therefore proportional to the local intensity of the beam. Passing the wire through the beam waist creates a series of pulses from the gold-tungsten wire that rise and fall in amplitude, the peak defining the coordinate of the laser pulse maxima for that particular position of L3 (which is mounted on a translation stage moving in the direction of the beam path called z).
The focal spot was studied using a gold-tungsten harp scanner in both the x and y plane. Each harp scan was comprised of an aluminum mount machined at UConn and then anodized to insulate it from the 50 micron gold-tungsten wire that was stretched across it as can be seen in the CAD drawing below.
[[Image:2wire.png|left|thumb|300px|CAD drawing of harp scan mount]]
The total current produced is dependent on the flux of UV light incident to the wire and therefore proportional to the local intensity of the beam. Passing the wire through the beam waist creates a series of pulses from the gold-tungsten wire that rise and fall in amplitude, the peak defining the coordinate of the laser pulse maxima for that particular position of L3 (which is mounted on a translation stage moving in the direction of the beam path called z). An integrating circuit was designed and constructed to measure the sum of current off the gold-tungsten wire. The scans are done in pairs of 2d projections: xz (called x-scans) and yz (called y-scans). Between the scans the wire frame is swapped out because there are separate frames for the vertical (x-scan) and horizontal (y-scan) wires. The 2d scans consist of an inner loop over the transverse coordinate, and an outer loop over z. The transverse coordinate range is 2mm and the z coordinate range is 12mm. Each pass has a single value of z, and sweeps over the full 2mm range in x or y. The output of the integrating circuit is connected to an ADC which is sampling continuously over that the whole time period the scan is taking place
{| cellpadding="3" style="text-align:center; margin: 1em auto 1em auto"
{| cellpadding="3" style="text-align:center; margin: 1em auto 1em auto"
|-
|-