Diamond Radiator Thinning and Mounting for GlueX

1. GlueX collaboration meeting, Regina, Sept. 9-11, 2010 Diamond Radiator Thinning and Mounting for GlueX R.T. Jones

2. Outline • Diamond ablation • laser lifetime issue – resolved • facility construction continues • Diamond mounting • tests with carbon wires • measurements with glue droplets • Diamond assessment • plans for a run this Fall at CHESS • outlook for the next 12 months R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

3. Diamond ablation facility Where we were at the May meeting: • first light pulses expected in ~1 week – then what? • UConn engineer/tech Brendan Pratt designed the optics setup (see below) • …then on June 1, first light pulses seen, low power at first, but increasing … • however the lifetime remained less than 5 minutes per gas fill R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

4. Diamond ablation facility Could the gas recirculating volume be somehow contaminated? Lasing happens in here along the line of sight. Gas gets recirculated through here to remove heat and filter out dust produced by reactions with the walls. Decision: undertake a major disassembly to remove any debris that could contaminate the fluorine gas. R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

5. Diamond ablation facility The inside was caked with residue from years of operation with a chlorine – xenon mixture. R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

6. Diamond ablation facility before after R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

7. Diamond ablation facility before after R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

8. Diamond ablation facility • After reassembly, lasing lasts 30 minutes with a single gas fill ! • Passivation process: lifetime gets longer with each fresh fill • There are two ways to refresh the gas: • top-up – takes 20 seconds • flush and refill – takes 5 minutes • We are now at the point where laser lifetime will not limit anything that we want to do. • Power per pulse starts out at 150 mJ, threshold is 35 mJ. • Major remaining limitation is pulse rate: 2 Hz without cooling laser lifetime is now 8 hours for one fill R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

9. Diamond ablation facility • 20% spot-RMS displacements between adjacent spots to get good uniformity • complete coverage with less than 10,000 spots • conservative estimate 1 mm in depth per pulse • net result: required to thin a 300 mm diamond to 30 mm • 2 Hz is not good enough laser focal spot 300 x 200 mm 200,000pulses 4 mm R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

10. Diamond ablation facility • Work now underway • Chilled water recirculator has been ordered • Precision stages for raster are on the bench • Labview software for raster control is in development • Ablation vacuum chamber is in final design, fabrication will take place in physics machine shop • First ablation tests anticipated Dec. 2010 increases maximum pulse rate to 50 Hz R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

11. Diamond mounting: carbon wires • Advantage of wires: minimize material in the tails of the electron beam, allow for full 90° rotation. • Advantage of carbon wires over tungsten: • factor 5 times stronger per area • factor 60 longer radiation length • possibility to sinter carbon to the diamond • Disadvantages of carbon wires • more brittle, can break when flexed • cannot solder to the mounting frame • Samples and expert help obtained from Fermilab accelerator physicist with experience using carbon wires as targets. studied by students in summer 2010 R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

12. Diamond mounting: carbon wires R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

13. The Principles Behind Our Experiment: Ensuring Radiator Stability • Resonance- • a system’s tendency to vibrate with a larger amplitude at certain frequencies • Constructive intereference • Vibrating Wire • Crystal radiator must be stable • Must be finely tunable to create Coherent Bremsstrahlung UConn Mentor Connection 2010 Chelsea Sidrane 13 R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

14. Weighting the Wire Tension (T) Tension (T) drop of glue Wires assumed massless L/2 L/2 M Length (L) Making Measurements -resonance frequency of carbon fibers -increased mass lowers resonant frequencies Angular Frequency UConn Mentor Connection 2010 Chelsea Sidrane 14 R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

15. Weighting the Wire: Theory V. Data • Theoretical Data estimated to find resonant curve UConn Mentor Connection 2010 Chelsea Sidrane *Enlarged view* Peak of Resonance Curve is maximum resonant frequency 15 R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

16. Diamond mounting: carbon wires • Conclusions from resonance study • Carbon wires are robust enough to hold a mass similar to a 20 micron 4x4 mm2 diamond. • Simple holding technique suggested by Fermilab colleagues is reliable, even with 30 mm wires. • Handling carbon wires is manageable, even for inexperienced students. • If multiple strands are wound together, we can achieve a fundamental frequency > 10,000 kHz which is far out on the tail of the ground motion spectrum – more than factor of 100 in amplitude. R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

17. Diamond assessment at CHESS • New run planned for November, 2010 • Element Six 10 micron diamond (1) • Element Six 500 micron type IIa crystals (2) • Ideas for mounting technique • slotted pin • stretched mylar R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

18. Future Outlook • Diamond thinning • assessment of first 10 mm diamond – 11/2011 • first ablated diamond at UConn – 12/2010 • first thinned diamond by SINMAT – 3/2011 • Diamond mounting • proof of concept with 30 mm carbon wires – 7/2010 • search underway for larger carbon ``thread’’, with fall-back solution to bundle them out of 30 mm strands R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

19. BNL diamond ablation facility • Material is ablated (vaporized) from the diamond surface by a focused beam from a pulsed UV laser. • Each pulse creates a pit ~100 mm diameter. • Rastering the beam over the surface of the diamond creates a smooth surface (sub-micron roughness). • Residual amorphous carbon on the surface is removed by chemical reaction (e.g. ozone, RIE process). R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

20. 152 µm 207 µm BNL diamond ablation facility Results presented by J. Smedley et.al., BNL Instrumentation Group, Feb. 2009. Deep ablation of polycrystaline sample: R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

21. UConn diamond ablation facility focusing lens (fused silica) laser pulse power monitor ablation plume laser beam from excimer (not shown) at an angle so the plume does not deposit on the ablation chamber window Optics setup, with vacuum chamber and CaF2 entrance window removed R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

22. SINMAT diamond RCMP facility • Small Business Innovation Research (SBIR) grant proposal submitted to DOE in November, 2009. • Phase I – one year, feasibility studies, $100K total with $30K for UConn to carry out assessment with X-rays at CHESS • Notice of grant awarded: April 2010 ! 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 R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010

23. Element Six monocrystal inventory • Element Six marketing: available for online orders • CVD single crystals: • CVD monocrystals • purity class: unstated • 300 microns x 4.5 mm x 4.5 mm or 1.2 mm x 8 mm x 8 mm • HPHT single-crystal plates: • HPHT synthetics • purity class: type Ib • 500 microns x 4.5 mm x 4.5 mm 150 £ or 1800 £ 167 £ R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 2010