1. Diamond Radiator Fabrication and Assessment Brendan Pratt Fridah Mokaya Richard Jones University of Connecticut GlueX Collaboration Meeting, Jefferson Lab, October 2012

2. Phase II STTR Project Interim Report, Sept., 20122 22 Outline Assessment of uniform samples produced by VPIE Advances with diamond ablation: improved optics Images of UConn’s first “picture frame” diamond Assessment of the UConn 40-micron sample Plans for upcoming CHESS run

3. Phase II STTR Project Interim Report, Sept., 20123 33 Uniform samples produced by VPIE raw material: type-3 CVD diamond from E6 original thickness ~150 microns 3 thinned samples: 150, 90, 30 microns thick 1.surface and thickness profiles with Zygo 2.X-ray rocking-curve topographs

4. Phase II STTR Project Interim Report, Sept., 20124 4 sample 1: 150 microns thickness surface and thickness profiles (Zygo 3D)

5. Phase II STTR Project Interim Report, Sept., 20125 5 sample 2: 90 microns thickness surface and thickness profiles (Zygo 3D)

6. Phase II STTR Project Interim Report, Sept., 20126 6 sample 3: 30 microns thickness surface and thickness profiles (Zygo 3D)

7. Phase II STTR Project Interim Report, Sept., 20127 X-ray diffraction assessment – June 2012 measurements at Cornell High Energy Synchrotron (CHESS)diffraction end-station C special monochromator setup and diffractometer configured for these measurements thanks to CHESS Staff Scientist Ken Finkelstein S150 S150 – thick reference standard S90 S90 – intermediate reference S30 – primary sample of interest

8. Phase II STTR Project Interim Report, Sept., 20128 X-ray assessment: S150 surface of S150 was polished with RCMP process limited by instrumental resolution !

9. Phase II STTR Project Interim Report, Sept., 20129 X-ray assessment: S90 surface of S90 was not treated after VPIE process not as flat as S150, but still in spec.

10. Phase II STTR Project Interim Report, Sept., 201210 X-ray assessment: S30 – the real target surface of S30 was not treated after VPIE process challenge lies here!

11. Phase II STTR Project Interim Report, Sept., 201211 add a frame new idea tested in 2012: add a frame diamonds appear to warp severely when thinned to 20 microns try to stiffen the diamond by leaving a thick outer frame around the 20 micron region frame around 20 micron is still part of the single crystal, maintains planarity warping is from combination of mounting and internal stresses

12. Phase II STTR Project Interim Report, Sept., 201212 First “picture frame” sample: U40 3 mm 300 micron frame around outside edge thinned inner rectangular window residual raster pattern is from a coarse laser step size

13. Phase II STTR Project Interim Report, Sept., 201213 Diamond Laser Ablation at UConn UConn group has a pulsed excimer laser (193nm) that has been configured with optics for diamond machining. Laser operates at above ablation energies for hours of run time. Milling process has been automated for cutting predefined patterns in diamond (~30k pulses per fill) Beam spot has been “cleaned” of spherical aberrations. Milled trenches in Element6 3.2x3.2mm diamond Developed in-house ozone cleaning apparatus for removing amorphous carbon off milled diamond

14. Phase II STTR Project Interim Report, Sept., 201214 3D Zygo Images of U40 approximate bottom surface depth, Zygo measurement on next slide White-light interferometer gives surface and thickness profiles with sub-micron prec. top surface measurements with Zygo

15. Phase II STTR Project Interim Report, Sept., 201215 3D Zygo Images of U40 White-light interferometer gives surface and thickness profiles with sub-micron prec. average thickness 40μm

16. Phase II STTR Project Interim Report, Sept., 201216 X-ray rocking curve for U40 excellent result for thinned diamond! surface of U40 was not treated after ablation

17. Phase II STTR Project Interim Report, Sept., 201217 Observations on ablated sample Definition of the central region is good. Sharpness of the walls does not degrade with depth. Pileup of amorphous carbon is not catastrophic So far no clouding of the ablation chamber window from residue Excellent flatness of the central region Excellent flatness of the central region So far no need for active correction to cutting rate, So far no need for active correction to cutting rate, but pulse-by-pulse recording of laser power is being collected, can be used to keep the milling rate even more uniform

18. Phase II STTR Project Interim Report, Sept., 201218 Upcoming CHESS Run CHESS recently acquired a new camera which will make scans 10x faster! Sinmat has just provided the first sample that has been picture-frame etched with a mask. U40 will soon become U20

19. Phase II STTR Project Interim Report, Sept., 201219 Questions?

20. Phase II STTR Project Interim Report, Sept., 201220 Backup Slides

21. Phase II STTR Project Interim Report, Sept., 201221 Improved laser optics L1 L2L3 First the laser beam is expanded setting L1 and L2’s focal points at the same location The “Point” is then imaged through L2, creating a parallel beam Finally, the light is focused through L3, a fused silica lens with a large radius of curvature (34.5mm) onto the target Larger beam at L3 => more parallel beam at L3 => smaller focus at diamond

22. Phase II STTR Project Interim Report, Sept., 201222 Improved Ablation Process: spread beam in y Beam spot spread widely in x Top View Instead, tilt in y (required mechanical changes) Side View Beam spot now more symmetric beam spot out of laser is elliptical major axis is horizontal

23. Phase II STTR Project Interim Report, Sept., 201223 New vs. Old Spot Profile Approx. 0.3mm Approx. 0.2mm Approx. 0.60mm Approx. 0.15mm Wider spot size in y allows for larger step sizes and faster rasterizing. Aspect Ratio 1.5 Aspect Ratio 4 before after