Changes

Figure 6 shows two columns of broad asymmetric patterns in a diamond sample cut using only a single lens for a varying number of laser pulses. Figure 7 shows the improvement in beam shape gained after using the three lens setup.

Figure 6 shows two columns of broad asymmetric patterns in a diamond sample cut using only a single lens for a varying number of laser pulses. Figure 7 shows the improvement in beam shape gained after using the three lens setup.

If the focal spot that created these patterns was rastered over an entire diamond it would result in a radiator with large surface variations rendering it unusable for GlueX. The focus of the laser defines the cutting tool with which the diamond is shaped. An ill-defined focused will ablate non-uniformly as the diamond is rastered across it making it extremely difficult to cut uniformly to 20 µm thickness without cracking the thin diamond membrane. The geometry of the focus also determines the fluence (laser energy per cm2 ) incident on the diamond surface. A tightly focused beam spot increases the available fluence, increasing the rate of ablation. It is therefore very important to measure the waist of the beam after L3 in the three lens system.

If the focal spot that created these patterns was rastered over an entire diamond it would result in a radiator with large surface variations rendering it unusable for GlueX. The focus of the laser defines the cutting tool with which the diamond is shaped. An ill-defined focused will ablate non-uniformly as the diamond is rastered across it making it extremely difficult to cut uniformly to 20 µm thickness without cracking the thin diamond membrane. The geometry of the focus also determines the fluence (laser energy per cm2 ) incident on the diamond surface. A tightly focused beam spot increases the available fluence, increasing the rate of ablation. It is therefore very important to measure the waist of the beam after L3 in the three lens system.

==Focal Spot Characterization==

==Focal Spot Characterization==

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| [[Image:xscan_005_map.png|left|thumb|300px|5a]] ||   || [[Image:yscan_003_map.png|right|thumb|300px|5b]]

| [[Image:xscan_005_map.png|left|thumb|300px|Figure 9a]] ||   || [[Image:yscan_003_map.png|right|thumb|300px|Figure 9b]]

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| [[Image:xscan_005_fit.png|left|thumb|300px|5c]] ||   || [[Image:yscan_003_fit.png|right|thumb|300px|5d]]

| [[Image:xscan_005_fit.png|left|thumb|300px|Figure 9c]] ||   || [[Image:yscan_003_fit.png|right|thumb|300px|Figure 9d]]

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*Color maps of the two orthoganol scans of beam focal region, where the color represents the charge per pulse seen on the wire in arbitrary units.

Figures 9a and 9b are color maps of the two orthoganol scans of beam focal region, where the color represents the charge per pulse seen on the wire in arbitrary units.

*Projections of the color maps shown in Figure 6 onto the transverse axis with Gaussian fits to central peak over a flat background.]]

Figures 9c and 9d are projections of the color maps shown in Figure 6 onto the transverse axis with Gaussian fits to central peak over a flat background.]]

Each pixel in the plots shown in Figures 7 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 RMS values of the fits in Figure 8. The values in x and y are roughly the same, 65 µm vs 48 µm respectively. Figure 7a 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

Each pixel in the plots shown in Figures 9 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 RMS values of the fits in Figure 9c,d. The values in x and y are roughly the same, 65 µm vs 48 µm respectively. Figure 9b 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

==Ablation Rate==

==Ablation Rate==