Progress in Diamond Target Fabrication University of Connecticut: Brendan Pratt Fridah Mokaya Richard Jones GlueX Collaboration meeting, Newport News, Feb , 2012

GlueX Collaboration Meeting, Newport News, Feb , Outline Thickness measurements Improved ablation process Report from Sinmat, Inc. Goals for CHESS run in June Outlook for 2014

GlueX Collaboration Meeting, Newport News, Feb , Thickness measurements thickness uniformity: no strict requirements stated design goal:  1 micron (5%) over active area may be modified for “picture frame” target design capability to measure thickness profile is needed capability to measure thickness profile is needed cannot measure one surface at a time both surfaces to be imaged without moving the sample active area original concept active area more realistic

GlueX Collaboration Meeting, Newport News, Feb , Thickness measurements head moves up and down ~ 1 micron reproducibility xy stage moves the sample ~ 2-3 micron wobble/weave at fixed position, resolution xy : 2 microns z : microns (5nm) field of view is smaller than sample: 600 x 400 microns field of view is smaller than sample: 600 x 400 microns take 100 tiled images with 15% overlaps stitch them together to form a single image

GlueX Collaboration Meeting, Newport News, Feb , Thickness measurements works well stitching the images from the upper surface – works well z (  m) x (mm) y (mm) z (  m) x (mm) y (mm)

GlueX Collaboration Meeting, Newport News, Feb , Thickness measurements idea: Try to look through the diamond and see the bottom surface reflection transmitted back through the top surface. z (  m) x (mm) y (mm) z (  m) x (mm) y (mm)

GlueX Collaboration Meeting, Newport News, Feb , Thickness measurements E6-10 diamond E6-10 diamond: uniformity is  20%, texture on one surface z (  m) x (mm) y (mm) x (mm) y (mm) z (  m)

GlueX Collaboration Meeting, Newport News, Feb , Thickness measurements summary demonstrated capability measurement is automated, takes ~30 minutes resolution better than required (<100 nm rms) ability to characterize surface features about the E6-10 diamond: thickness is 11  2 microns, close to vendor claim thickness uniformity would be OK for GlueX What are those bumps on one side? question for E6: What are those bumps on one side? no answer so far no answer so far M.F. has departed E6 M.F. has departed E6 new rep. T.O. has begun correspondence on this issue new rep. T.O. has begun correspondence on this issue

GlueX Collaboration Meeting, Newport News, Feb , Laser ablation: recap from 2011 Excimer laser refurbished XY translation stage purchased Vacuum chamber constructed, leak checked Optical bench and UV focusing optics installed Chiller (allows for rep rate >3Hz, max 50Hz) External trigger circuit designed and built Data acquisition card for pulse measurement LabView control program written and tested first cuts into diamond in October 2011 slide by B. Pratt

GlueX Collaboration Meeting, Newport News, Feb , Laser ablation: results from Skewed Spot due to Spherical Abberations in Optics slide by B. Pratt

GlueX Collaboration Meeting, Newport News, Feb , Laser ablation: original optics Single fused silica focusing lens creates large spherical aberrations in spot. 11 slide by B. Pratt

GlueX Collaboration Meeting, Newport News, Feb , Improved ablation process: new 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 slide by B. Pratt Larger beam at L3 => more parallel beam at L3 => smaller focus at diamond

GlueX Collaboration Meeting, Newport News, Feb , Improved ablation process – using new raster program mm increments mm increments slide by B. Pratt

GlueX Collaboration Meeting, Newport News, Feb , Improved ablation process – using new raster program slide by B. Pratt 0.7mm 0.9mm0.5mm

GlueX Collaboration Meeting, Newport News, Feb , Improved ablation process – using new raster program slide by B. Pratt trenches show 0.05mm step after each row of the raster

GlueX Collaboration Meeting, Newport News, Feb , Improved ablation process: vertical cut slide by B. Pratt z (microns) x (mm)  feedback on laser pulse amplitude was turned off  depth variation consistent with pulse-to-pulse fluctuations in laser power (non-linear)  online pulse power monitor is part of the DAQ setup

GlueX Collaboration Meeting, Newport News, Feb , Improved ablation process: horizontal cut milling depth 0.8 microns slide by B. Pratt z (microns) x (mm)  cut profile much wider in x than y  comes from combination of 45° angle w.r.t. beam and laser spot asymmetry  45° incidence angle can be reduced  may require 90° sample rotation to produce flat central region

GlueX Collaboration Meeting, Newport News, Feb , Improved ablation process: single shot long axis ~ 600  m short axis ~ 100  m depth ~ 120 nm/shot residue (soot) easy to clean by ultrasonic bath

GlueX Collaboration Meeting, Newport News, Feb , Improved ablation process: summary Laser is operating at above ablation energies for hours of run time. Automation of milling cycle is complete. Beam spot has been “cleaned” of spherical aberrations. Plans are to mill a 20 micron region out of a 300 micron diamond before CHESS run in June. slide by B. Pratt

GlueX Collaboration Meeting, Newport News, Feb , Report from SINMAT Phase II STTR award underway since Sept. Perfecting their thinning process 1.RIE (reactive ion etching, atomic oxygen plasma) for rapid material removal – residual roughness 10%. 2.RCMP (reactive chemically-assisted mechanical polishing) to plane the rough surface, remove surface anomalies. 3.repeat… First time around they went too fast First time around they went too fast – time pressure due to project 9-month deadline Next time around, want to treat both sides Next time around, want to treat both sides. It still may be that the residual curvature seen in SINMAT-9 is due to surface damage on the side that Sinmat did not process. Current job list: 100, 80, 60, 40, 20 micron samples. Current job list: 100, 80, 60, 40, 20 micron samples.

GlueX Collaboration Meeting, Newport News, Feb , Goals for CHESS run in June five SINMAT samples: A subset of these is expected to serve as the first pieces in the Hall D radiator inventory. one or two UConn samples: 100, 80, 60, 40, 20  m picture-frame fabrication thinned to 20 microns in central 3 x 3 mm 2 zone

GlueX Collaboration Meeting, Newport News, Feb , Outlook for 2014 For commissioning will have For commissioning will have: at least 2 thick diamond targets (100, 80, …) already qualified with X-rays at CHESS will doubtless satisfy flatness requirements goniometer mount will be version 1.0 target mounting problems and halo interactions in the mount are reduced reduced radiation damage allows radiator lifetime studies without rapid degradation can still test active collimator reduced polarization

GlueX Collaboration Meeting, Newport News, Feb , Outlook for 2014 By that date, planning to provide: By that date, planning to provide: two picture-frame targets with 20 micron centers already qualified at CHESS with mounting fixture to be mounted on target ladder together with the above fail-safe targets useful to measure radiation lifetime at elevated currents expected for full-intensity running useful to commission the pair spectrometer enables maximum polarization

GlueX Collaboration Meeting, Newport News, Feb , Questions