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GlueX collaboration meeting, Newport News, May 10-12, 2010
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Status Update: Diamond Radiator Procurement and Processing for GlueX
Richard Jones, University of Connecticut
GlueX collaboration meeting, Newport News, May 10-12, 2010
GlueX collaboration meeting, Newport News, May 10-12, 2010
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Outline• Thin diamond production
– laser ablation– chemical polishing– thin crystal cutting
• Mounting– carbon wires– smaller crystals
GlueX collaboration meeting, Newport News, May 10-12, 2010
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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, 2010
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Technique #1: laser ablation
152 µm 207 µm
Results presented by J. Smedley et.al.,BNL Instrumentation Group, Feb. 2009.
Deep ablation of polycrystaline sample:
GlueX collaboration meeting, Newport News, May 10-12, 2010
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Technique #1: laser ablation
• Progress at UConn:– Pilot project funded ($13 K) by UConn Research
Foundation: Jan. 2010.– Laser installation, refurbishment, safety
procedures worked out: Jan. – June 2010.– Optics design and installation: May – Aug. 2010.– Design and installation of ablation chamber and
rastering stage: June – Sep. 2010.– First tests with diamond sample: Oct. 2010
GlueX collaboration meeting, Newport News, May 10-12, 2010
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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, 2010
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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, 2010
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Technique #1: laser ablation
laser beam fromexcimer (not shown)
laser pulsepower monitor
focusing lens (fused silica)
ablation plumeat an angle so the plumedoes not deposit on theablation chamber window
Optics setup, with vacuum chamberand CaF2 entrance window removed
GlueX collaboration meeting, Newport News, May 10-12, 2010
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Technique #2: chemical polishing
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 Inc2153 SE Hawthorne Road, Suite 124 (Box 2)Gainesville Fl 32641-7553Phone / Fax : 352-334-7270
Principal Investigator: Arul ArjunanProject Title: Defect Free, Ultra-Rapid Thinning/Polishing
(20μm) of Diamond Crystal RadiatorTopic Number: 46 - Nuclear Physics Instrumentation,
Detection Systems and TechniquesSub-topic: e - Specialized Targets for Nuclear Physics Research
GlueX collaboration meeting, Newport News, May 10-12, 2010
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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 fragile2. maintain uniform thickness3. keep original rocking curve width
Quality control process:1. obtain new monocrystals and characterize at CHESS2. pass at least one through the SINMAT process3. measure rocking curves again at CHESS
GlueX collaboration meeting, Newport News, May 10-12, 2010
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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– extrapolation of known process by
two orders of magnitude in thicknesstwo 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 We just happen to have a 10 micron thick10 micron thick sample of electronic sample of electronic
grade monocrystal 4.5 x 4.5 mm in area. Are you interested?grade monocrystal 4.5 x 4.5 mm in area. Are you interested?
GlueX collaboration meeting, Newport News, May 10-12, 2010
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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, 2010
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All Techniques: raw material
Element Six marketing: available by special order
Current belief in our group (based on limited data) HPHT monocrystals can have narrow rocking curves in places,
but need to carefully assessed and selectedcarefully 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, 2010
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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, 2010
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Outline• Thin diamond production
– laser ablation– chemical polishing– thin crystal cutting
• Mounting– carbon wires– smaller crystals
GlueX collaboration meeting, Newport News, May 10-12, 2010
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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, 2010
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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
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