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

R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, Outline Diamond ablation Diamond ablation  laser lifetime issue – resolved  facility construction continues Diamond mounting Diamond mounting  tests with carbon wires  measurements with glue droplets Diamond assessment 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, 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, 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: 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, 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, Diamond ablation facility before after

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

R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, Diamond ablation facility 30 minutes  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: 1.top-up – takes 20 seconds 2.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, 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  m in depth per pulse  net result: required to thin a 300 mm diamond to 30 mm  2 Hz is not good enough 4 mm laser focal spot 300 x 200  m 200,000 pulses

R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 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 Hz increases maximum pulse rate to 50 Hz

R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, 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. Diamond mounting: carbon wires studied by students in summer 2010

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

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

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

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

R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, Diamond mounting: carbon wires  Conclusions from resonance study 1.Carbon wires are robust 1.Carbon wires are robust enough to hold a mass similar to a 20 micron 4x4 mm 2 diamond. 2.Simple holding technique 2.Simple holding technique suggested by Fermilab colleagues is reliable, even with 30  m wires. 3.Handling carbon wires is manageable 3.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,  New run planned for November, Element Six 10 micron diamond (1) 2.Element Six 500 micron type IIa crystals (2)  Ideas for mounting technique – slotted pin – stretched mylar Diamond assessment at CHESS

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

R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11,  Material is ablated (vaporized) from the diamond surface by a focused beam from a pulsed UV laser.  Each pulse creates a pit ~100  m 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). BNL diamond ablation facility

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

R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11, laser beam from excimer (not shown) laser pulse power monitor focusing lens (fused silica) ablation plume at an angle so the plume does not deposit on the ablation chamber window Optics setup, with vacuum chamber and CaF 2 entrance window removed UConn diamond ablation facility

R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11,  Small Business Innovation Research (SBIR) grant proposal submitted to DOE in November,  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 Phone / Fax : 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 SINMAT diamond RCMP facility

R.T. Jones, GlueX Collaboration Meeting, Regina, Sept. 9-11,  Element Six marketing: available for online orders HPHT single-crystal plates:  HPHT synthetics  purity class: type Ib  500 microns x 4.5 mm x 4.5 mm 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 167 £ 150 £ or 1800 £ Element Six monocrystal inventory