Status Update: Diamond Radiator Procurement and Processing for GlueX Richard Jones, University of Connecticut GlueX collaboration meeting, Newport News, May 10-12, 2010

2 Outline Thin diamond production – laser ablation – chemical polishing – thin crystal cutting Mounting – carbon wires – smaller crystals

GlueX collaboration meeting, Newport News, May 10-12, Technique #1: laser ablation  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).

GlueX collaboration meeting, Newport News, May 10-12, Technique #1: laser ablation 152 µm 207 µm Results presented by J. Smedley et.al., BNL Instrumentation Group, Feb Deep ablation of polycrystaline sample:

GlueX collaboration meeting, Newport News, May 10-12, Technique #1: laser ablation Progress at UConn: – Pilot project funded ($13 K) by UConn Research Foundation: Jan – Laser installation, refurbishment, safety procedures worked out: Jan. – June – Optics design and installation: May – Aug – Design and installation of ablation chamber and rastering stage: June – Sep – First tests with diamond sample: Oct. 2010

GlueX collaboration meeting, Newport News, May 10-12, Technique #1: laser ablation Progress at UConn: – excimer gases highly corrosive, tend to attack o-rings and seals. – all o-rings in the system have been cleaned or replaced. – vacuum leak rate now 1 order of magnitude below spec! – thyratron checks out, makes sparks at the correct frequency – corrosive gas regulators, pump filter, valves all in place, waiting for fluorine gas from vendor…

GlueX collaboration meeting, Newport News, May 10-12, Technique #1: laser ablation Progress at UConn: – first light pulses expected in ~1 week – then what? – UConn engineer/tech Brendan Pratt designed the optics setup (see below)

GlueX collaboration meeting, Newport News, May 10-12, Technique #1: laser ablation 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

GlueX collaboration meeting, Newport News, May 10-12, Technique #2: chemical polishing  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

GlueX collaboration meeting, Newport News, May 10-12, Technique #2: chemical polishing  Goal will be to see if Sinmat can take a 200 micron diamond and thin it to 20 microns with their technique.  Challenges are: 1.handling of 20 micron diamond – very fragile 2.maintain uniform thickness 3.keep original rocking curve width  Quality control process: 1.obtain new monocrystals and characterize at CHESS 2.pass at least one through the SINMAT process 3.measure rocking curves again at CHESS

GlueX collaboration meeting, Newport News, May 10-12, Technique #3: thin layer cutting Method is potentially interesting for Gluex, but requires some new things: – access to IB facilities – new collaborators with this expertise two orders of magnitude in thickness – extrapolation of known process by two orders of magnitude in thickness Out of the blue from Element Six: mid-March, 2010 – We have “some capabilities” for (laser?) cutting thin layers from thick diamond substrates in one of our other facilities. – We just happen to have a 10 micron thick sample of electronic grade monocrystal 4.5 x 4.5 mm in area. Are you interested?

GlueX collaboration meeting, Newport News, May 10-12, All Techniques: raw material  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 £

GlueX collaboration meeting, Newport News, May 10-12, All Techniques: raw material  Element Six marketing: available by special order  Current belief in our group (based on limited data) carefully assessed and selected  HPHT monocrystals can have narrow rocking curves in places, but need to carefully assessed and selected.  Electronic-grade CVD monocrystals have consistently narrow rocking curves and have a much better growth morphology than HPHT samples we have seen. narrow rocking curve crystals:  HPHT synthetics  purity class: type IIa  market: diffraction applications electronic grade crystals:  CVD monocrystals  purity class: type III  market: electronic devices

GlueX collaboration meeting, Newport News, May 10-12, Procurement plans: raw material  Purchase the 10 micron diamond and assess to see if technique #3 can produce narrow rocking curve diamonds.  Purchase two each of the electronic grade and type IIa HPHT diamonds for work with SINMAT.  Purchase several of the non-electronic grade CVD monocrystals for testing the ablation process.

GlueX collaboration meeting, Newport News, May 10-12, Outline Thin diamond production – laser ablation – chemical polishing – thin crystal cutting Mounting – carbon wires – smaller crystals

GlueX collaboration meeting, Newport News, May 10-12, Mounting plans: 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.

GlueX collaboration meeting, Newport News, May 10-12, Summary  Progress since January on all three approaches to diamond thinning: 1.laser ablation – under construction 2.chemical polishing – project funded 3.thin crystal cutting – sample ordered  Mounting technique – carbon wires to replace tungsten – bench tests are underway