1. Diamond Radiator Development Richard Jones Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010

2. 2 Outline Producing thin crystals –three promising techniques –SBIR grant proposal (technique #2) –excimer laser project (technique #3) –risks, timeline, decisions Mounting thin crystals –two challenges –observations at CHESS –observations on the bench at UConn –ideas for mitigation –risks, timeline, decisions

3. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 3 Three promising techniques 1.Ion implantation, chemical etching, and lift-off 2.Chemically-assisted mechanical polishing 3.Laser ablation and reactive ion etching

4. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 4 Technique #1: ion implantation Method in use by groups in UK and Japan, perhaps elsewhere step 1: set ion beam energy for a specific depth, sweep over area of the crystal high-quality thick diamond monocrystal step 2: heat the crystal. The thin deposition layer converts to graphite. heating anneals the crystal, creates graphite layer step 3: laser-drill trenches around the edges and inject solution to etch the graphite chemical etch dissolves graphite, but not diamond

5. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 5 Technique #1: ion implantation Method in use by groups in UK and Japan, perhaps elsewhere step 4: braze a tiny wire to the thin crystal and simply lift it off the substrate

6. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 6 Technique #1: ion implantation Method in use by groups in UK and Japan, perhaps elsewhere step 4: braze a tiny wire to the thin crystal and simply lift it off the substrate Very thin crystals (400 nm) have been made with this technique. Possibly the only way to make diamond monocrystals thinner than 1  m. Many thin crystals can be cut from a single thick substrate. Discussion with experts: Never considered anything as thick as 20  m! Ion bombardment energy must be increased, so would need a specialized ion beam facility.

7. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 7 Technique #1: ion implantation Method is potentially interesting for Gluex, but –requires new collaborators with expertise in ion beam techniques (University of Strathclyde, Glasgow???) –requires access to IB facilities (may be available at Jlab in accelerator group for cleaning RF cavities???), –requires extrapolation of known process by 2 orders of magnitude in thickness (range is easy to calculate, but will increased energies damage the pristine crystal in new ways?)

8. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 8 Technique #2: chemical polishing Improves on mechanical polishing alone by reducing the forces needed to achieve a given material removal rate. Mechanical abrasion techniques are know to work, but they all suffer limitations: a)low removal rates b)poor surface finish c)extensive sub-surface damage d)poor scalability in manufacturing.

9. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 9 Technique #2: chemical polishing Basic idea of process: 1.Chemicals coating slurry particles undergo pressure-catalyzed reaction with diamond surface. 2.Mechanical abrasion removes the softened surface material. Diamond + chemistry + coated particle  soft surface layer [–C–C] [–C–O] Diamond soft layer + coated particle  removal of soft surface layer, leaving clean diamond surface [–C–O] [–C–C] process under development by Sinmat Inc., Gainesville, FL

10. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 10 Technique #2: chemical polishing Small Business Innovation Research (SBIR) grant proposal submitted to DOE in November, 2009. Phase I – one year, feasibility studies Budget – $100K for phase I, $30K for UConn Currently under review at DOE Company: Sinmat Inc 2153 SE Hawthorne Road, Suite 124 (Box 2) Gainesville Fl 32641-7553 Phone / Fax : 352-334-7270 Principal Investigator: Arul Arjunan Project Title: Defect Free, Ultra-Rapid Thinning/Polishing (20μm) of Diamond Crystal Radiator Topic Number: 46 - Nuclear Physics Instrumentation, Detection Systems and Techniques Sub-topic: e - Specialized Targets for Nuclear Physics Research

11. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 11 Technique #3: laser ablation 1.Material is ablated (vaporized) from the diamond surface by a focused beam from a pulsed UV laser. 2.Each pulse creates a pit ~100  m diameter. 3.Rastering the beam over the surface of the diamond creates a smooth surface (sub-micron roughness). 4.Residual amorphous carbon on the surface is removed by chemical reaction (e.g. ozone, RIE process). Technique being perfected by the BNL Instrumentation Group Results from BNL described at previous Gluex meetings Agreement (informal) with BNL group to cooperate with Gluex –Gluex needs its own laser ablation capabilities –BNL will compare results, advice, help with surface characterization

12. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 12 Technique #3: laser ablation As of the last collaboration meeting 9/2009: –Excimer laser with sufficient power, pulse rate found at UConn. –UConn laser last used 1998, needs refurbishment. –JSA proposal for $15,000 to refurbish laser was declined. News as of 12/2009 –Proposal submitted for internal funding at UConn under the Large Faculty Grant competition in Oct. 2009. –$13,000 requested for materials, supplies, student labor. –$5,000 additional in NSF grant operating funds to be devoted to project for student labor. –Request approved for full amount for period Jan.-Dec., 2010.

13. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 13 Laser refurbishment plan First, take the proper safety course required by the University of Connecticut Environmental Health and Safety department. Prepare Dr. Well's laboratory for the transfer of the excimer laser including setup of ventilation, three-phase (208V) power supply, cold water distribution and collection, and a sturdy table to put the laser on. Replacement of halogen filters Tend to the vacuum system: replace oil in diffusion pump, test for serious leaks at moderately low pressure (10−6 Torr) Test the RF generator (most expensive/hard to replace!) Procure a bottle of pure Ar gas Check internal circulating fan bearings, as these are a possibly source of corrosion Flush the tube, turn it on and test output power

14. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 14 Laser refurbishment: current status Gas lines have been installed with new Swagelok fittings. Gas solenoids have been repaired and the system has been charged with fresh Helium to 2600mbar. Currently the system is leaking >25mbar per hour and we plan on replacing o-rings in main laser window to fix this. Optics will be cleaned once we receive our new supplies and the laser must be realigned using a HeNe laser. A Veeco Helium Leak Detector was used to check for leak sites. The front window has the largest source of Helium at the moment and the o-ring will be replaced shortly. Also, a number of the "spark plugs" that discharge into the laser had noticeable leak rates and I hope to service them shortly.

15. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 15 Laser refurbishment: progressing well Brendan Pratt Project specialist (and group brewmaster) is UConn grad Brendan Pratt (see http://zeus.phys.uconn.edu/wiki/ for updates)http://zeus.phys.uconn.edu/wiki/

16. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 16 Risks with our approach Two complementary techniques –laser ablation is the standard option –RCMP is the backup option (depends on SBIR funding) –RCMP may be useful with laser ablation (clean ablated surface) the next 12 monthsA lot depends on what happens in the next 12 months: –Laser refurb. does not hit a show-stopper – none in sight –Sinmat’s interest in our project is maintained depends on SBIR funding or finding another source of funds –Our collaboration with CHESS staff is maintained we should carry out the upgrade they requested –We can procure a set of Element Six diamonds of our own

17. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 17 Mounting thin diamond crystals Two challenges: 1.mechanical vibration 2.stability of adhesive at elevated temperatures

18. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 18 Mounting thin diamond crystals Observation of vibration at CHESS Intensity (arb. units) 200  r (actual) 8  r (expected) Intensity (arb. units) 10  r FWHM

19. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 19 Undergraduate student Chris Pelletier aligns the Michelson Interferometer that he built. diamond crystal mounting wires Mounting thin diamond crystals Observations on the bench at UConn

20. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 20 Video of “Flare” Spot Motion Images taken with a high-speed camera: 1200 frames/s. Direct laser spot does not move, but creates a “flare” spot that we calibrated to the rotation angle of the wafer. windows video quicktime video

21. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 21 Flair Spot v. Time (Images) T=0sT=.000833sT=.001667s T=.0025sT=.004167sT=.005s T=.005833sT=.00667sT=.0075s

22. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 22

23. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 23 DFT of time-domain signals A single dominant resonance ~18 Hz is visible in both x and y. A fun undergraduate research project: tune the fundamental resonance frequency and measure the power spectrum of the driving force. Solution: push fundamental resonance up to where F(  ) is weak. Horizontal Motion Vertical Motion

24. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 24 Mounting thin diamond crystals Challenge #2: operating temperature temperature (K) x position (cm) y position (cm) Operating temperature for 20  m diamond for high intensity GlueX running. New result New result: now includes conduction through 18  m diameter W wires. Temperature is ~420° C, down from 520° C with radiation alone, but still too high for epoxy.

25. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 25 Mounting thin diamond crystals Challenge #2: high-temperature adhesives 1.ceramics – epoxy vendor recommendation 2.brazing – diamond experts say this works best 3.use a pinch-mount – avoid adhesives altogether requires more mass near the beam might grip in one corner esp. interesting if diamond thinning allows for fat edges grip the corner

26. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 26 Risks with our approach Vibration must be reduced 2 orders of magnitude wires are now anomalously long, can be reduced by factor 5 can go from tungsten to carbon fiber, more strength/Z 2 response dominated by match between resonances and power spectrum of building vibrations – should drop rapidly with frequency bench tests have resolution to just detect diamond motion down to 10  r p-p so we can optimize the mount using our interferometer. a solution that meets our requirements is yet to be demonstrated Epoxy mount (e.g. Mainz, Hall B) may fail in Hall D several workable solutions exist which one is best depends on the final morphology of the diamond

27. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 27 Timeline and decisions: 2010 Mar. 1, 2010: Funding found to buy diamonds from Element Six, and submit order for 3 samples. May 1, 2010: If diamonds are available, measure at CHESS, otherwise next window is Nov., 2010. June 1, 2010: UConn laser is working, or we need another solution. July 1, 2010: Sinmat’s SBIR was approved, or we need to find another funding source to work with them. … if all above milestones were met successfully, then Oct. 1, 2010: Obtain first thinned diamond back from Sinmat Nov. 1, 2010: Mount Sinmat diamond, characterize at CHESS.

28. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 28 Summary and outlook A number of open issues remain to be answered before we can procure radiator diamonds for GlueX. Diamond radiator development is the top priority for the UConn group in 2010. Detailed work plan set out for the period up until mid-summer with milestones and decisions. Purchase of diamonds from Element Six is now on the critical path for this development.

29. Gluex Collaboration Meeting, Newport News, Jan. 28-30, 2010 29 Questions