Diamond Radiator Fabrication and Assessment Brendan Pratt Fridah Mokaya Richard Jones University of Connecticut GlueX Collaboration Meeting, Jefferson Lab, February 2013

222 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

3 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

444 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 Vastly increase milling rate milling ~100microns/hr

55 sample 3: 30 microns thickness surface and thickness profiles (Zygo 3D)

66 S30: X-ray Measurements S30scan01 S30scan04

77 sample 2: 90 microns thickness surface and thickness profiles (Zygo 3D)

88 S90: X-ray Measurements

99 sample 1: 150 microns thickness surface and thickness profiles (Zygo 3D)

10 S150: X-ray Measurements

S150: Zygo Cross Section (before the accident) 11

12 Bob: X-ray Measurements

Bob: Zygo Cross Sections 13

14 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

15 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

16 U40: Original X-ray Measurements excellent result for thinned diamond! surface of U40 was not treated after ablation

17 U40: X-ray Measurements

18 Casey: X-ray Measurements

Casey: Zygo Cross Section 19

20 Most Importantly… 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 We’ve increased Ablation Rate to We’ve increased Ablation Rate to ~100microns/hr! ~100microns/hr!

21 Questions?

22 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